/**
 * sdr-api-core.js - SimpleDocReview's HTTP API, ported to run without a server.
 *
 * A Hugging Face Static Space has no compute, so `app.py` cannot run. This file
 * is a port of every route upstream's `ReviewHandler` serves and of the logic
 * behind them: the rubric analyzer, the DOCX text extractor, status
 * recalculation, the notification queue, and the record migrations.
 *
 * It contains no DOM and no storage engine. Everything environment-specific
 * arrives through `createApi()`:
 *
 *     store        persistence  (app.py's data/reviews.json + uploads/ pair)
 *     now          clock        (app.py utc_now)
 *     uuidHex      identity     (app.py uuid.uuid4().hex)
 *     inflateRaw   DEFLATE      (app.py zipfile)
 *
 * That separation is what makes it testable: `sdr-api-shim.js` supplies
 * IndexedDB and the browser clock, while `tests/parity/` supplies an in-memory
 * store and a fixed clock so these responses can be diffed against the real
 * Python server's.
 *
 * Comments name the app.py function each part mirrors. When upstream changes
 * that file, change this one - never the other way round.
 */
(function (root, factory) {
  "use strict";
  var api = factory();
  if (typeof module === "object" && module !== null && module.exports) {
    module.exports = api;
  }
  if (root) {
    root.SdrApiCore = api;
  }
})(typeof globalThis !== "undefined" ? globalThis : this, function () {
  "use strict";

  // --------------------------------------------------------------- constants
  // app.py: MAX_UPLOAD_BYTES, ALLOWED_EXTENSIONS, CONTACT_FIELDS, *_LABELS.

  var MAX_UPLOAD_BYTES = 5 * 1024 * 1024;
  var ALLOWED_EXTENSIONS = [".txt", ".md", ".docx"];
  var CONTACT_FIELDS = ["email", "slack", "teams"];

  var STATUS_LABELS = {
    uploaded: "Uploaded",
    in_review: "In review",
    changes_requested: "Changes requested",
    approved: "Approved"
  };

  var ASSIGNMENT_LABELS = {
    pending: "Pending",
    commented: "Commented",
    changes_requested: "Changes requested",
    approved: "Approved"
  };

  var SEVERITY_ORDER = { high: 0, medium: 1, low: 2 };

  var DOWNLOAD_TYPES = {
    ".txt": "text/plain",
    ".md": "text/markdown",
    ".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
  };

  // Python's `\w` is Unicode-aware where JavaScript's is ASCII-only, so the
  // port uses Unicode property escapes. `\b[\w'-]+\b` can only begin and end on
  // a word character - an apostrophe or hyphen at either edge fails the word
  // boundary - which is what the outer/inner split below spells out.
  var WORD_PATTERN = /[\p{L}\p{N}_](?:[\p{L}\p{N}_'-]*[\p{L}\p{N}_])?/gu;

  // ------------------------------------------------------------------ errors

  /**
   * An error carrying the status app.py would have replied with.
   *
   * app.py maps `ValueError` to 400 and calls `send_error_json(..., NOT_FOUND)`
   * for missing records, so the status has to travel with the message for the
   * responses to stay identical.
   */
  function apiError(message, status) {
    var error = new Error(message);
    error.apiStatus = status || 400;
    return error;
  }

  function badZip(message) {
    // app.py catches zipfile.BadZipFile in do_POST and replies with this text.
    return apiError(message || "The DOCX file appears to be invalid.", 400);
  }

  // ----------------------------------------------------------------- helpers

  function two(value) {
    return value < 10 ? "0" + value : String(value);
  }

  /** app.py utc_now(): an ISO-8601 UTC stamp truncated to whole seconds. */
  function defaultNow() {
    var when = new Date();
    return (
      when.getUTCFullYear() +
      "-" + two(when.getUTCMonth() + 1) +
      "-" + two(when.getUTCDate()) +
      "T" + two(when.getUTCHours()) +
      ":" + two(when.getUTCMinutes()) +
      ":" + two(when.getUTCSeconds()) +
      "+00:00"
    );
  }

  /** app.py uuid.uuid4().hex: 32 lowercase hex characters, no dashes. */
  function defaultUuidHex() {
    var bytes = new Uint8Array(16);
    globalThis.crypto.getRandomValues(bytes);
    bytes[6] = (bytes[6] & 0x0f) | 0x40;
    bytes[8] = (bytes[8] & 0x3f) | 0x80;
    var hex = "";
    for (var index = 0; index < bytes.length; index += 1) {
      hex += (bytes[index] < 16 ? "0" : "") + bytes[index].toString(16);
    }
    return hex;
  }

  /** DEFLATE with no zlib wrapper - what a ZIP member stores. */
  function defaultInflateRaw(bytes) {
    if (typeof DecompressionStream === "undefined") {
      return Promise.reject(
        badZip("This browser cannot read DOCX files: DecompressionStream is unavailable.")
      );
    }
    var stream = new Blob([bytes]).stream().pipeThrough(new DecompressionStream("deflate-raw"));
    return new Response(stream).arrayBuffer().then(function (buffer) {
      return new Uint8Array(buffer);
    });
  }

  /** Python `str(value or "")`: falsy values collapse to the empty string. */
  function pyStr(value) {
    if (value === undefined || value === null || value === false || value === 0 || value === "") {
      return "";
    }
    if (Array.isArray(value) && value.length === 0) {
      return "";
    }
    return String(value);
  }

  /** app.py clean_text(). */
  function cleanText(value, fallback, maxLength) {
    var limit = maxLength === undefined ? 240 : maxLength;
    var text = pyStr(value).trim();
    return (text || (fallback === undefined ? "" : fallback)).slice(0, limit);
  }

  /** Python re.escape(), for the characters these patterns actually contain. */
  function escapeRegExp(value) {
    return String(value).replace(/[.*+?^${}()|[\]\\\-]/g, "\\$&");
  }

  function emptyContact() {
    return { email: "", slack: "", teams: "" };
  }

  function isPlainObject(value) {
    return typeof value === "object" && value !== null && !Array.isArray(value);
  }

  function hasOwn(target, key) {
    return Object.prototype.hasOwnProperty.call(target, key);
  }

  /** app.py normalize_contact(). */
  function normalizeContact(payload) {
    var source = isPlainObject(payload) ? payload : {};
    var contact = {};
    CONTACT_FIELDS.forEach(function (field) {
      contact[field] = cleanText(source[field], "", 240);
    });
    return contact;
  }

  /** app.py owner_from_payload(). */
  function ownerFromPayload(payload) {
    var source = isPlainObject(payload) ? payload : {};
    var owner = { name: cleanText(source.name || source.owner_name, "Owner", 120) };
    var contact = normalizeContact(source);
    CONTACT_FIELDS.forEach(function (field) {
      owner[field] = contact[field];
    });
    return owner;
  }

  /**
   * Stable descending sort on one string key.
   *
   * Python's `sorted(..., reverse=True)` keeps equal elements in their original
   * order rather than reversing them. These timestamps have one-second
   * resolution, so ties are routine and a plain `.reverse()` would reorder
   * same-second activity that the Python server leaves alone.
   */
  function sortByDesc(items, key) {
    return items.slice().sort(function (left, right) {
      var a = left[key] || "";
      var b = right[key] || "";
      if (a === b) return 0;
      return a < b ? 1 : -1;
    });
  }

  function sortByAsc(items, read) {
    return items.slice().sort(function (left, right) {
      var a = read(left);
      var b = read(right);
      if (a === b) return 0;
      return a < b ? -1 : 1;
    });
  }

  // ----------------------------------------------------- filenames and bytes

  /** app.py sanitize_filename(). */
  function sanitizeFilename(filename) {
    var name = pyStr(filename) || "document";
    var segments = name.split(/[\\/]/);
    name = segments[segments.length - 1].trim();

    var dot = name.lastIndexOf(".");
    var stem = name;
    var suffix = "";
    // pathlib keeps a leading dot in the stem ('.env' -> stem '.env') and reads
    // a trailing dot as no suffix at all ('notes.' -> stem 'notes.').
    if (dot > 0 && dot < name.length - 1) {
      stem = name.slice(0, dot);
      suffix = name.slice(dot).toLowerCase();
    }
    if (!stem) stem = "document";

    var cleaned = stem.replace(/[^A-Za-z0-9._ -]+/g, "-").replace(/^[ .\-_]+|[ .\-_]+$/g, "");
    return (cleaned || "document") + suffix;
  }

  /** pathlib's Path(name).suffix.lower(). */
  function extensionOf(filename) {
    var name = pyStr(filename);
    var segments = name.split(/[\\/]/);
    name = segments[segments.length - 1];
    var dot = name.lastIndexOf(".");
    if (dot <= 0 || dot === name.length - 1) return "";
    return name.slice(dot).toLowerCase();
  }

  function tryDecode(bytes, encoding) {
    try {
      return new TextDecoder(encoding, { fatal: true }).decode(bytes);
    } catch (error) {
      return null;
    }
  }

  /**
   * app.py decode_text_bytes(): utf-8-sig, then utf-16, then cp1252, then utf-8
   * with replacement characters.
   *
   * TextDecoder("utf-8") strips a leading BOM, which is what utf-8-sig does.
   * Python's utf-16 codec consumes a BOM when present and assumes
   * little-endian when it is absent.
   *
   * One knowing divergence: WHATWG windows-1252 maps the five bytes Python's
   * cp1252 rejects (0x81, 0x8D, 0x8F, 0x90, 0x9D) rather than raising, so a
   * file Python would fall through to replacement-character utf-8 decodes here
   * as windows-1252 instead.
   */
  function decodeTextBytes(bytes) {
    var utf8 = tryDecode(bytes, "utf-8");
    if (utf8 !== null) return utf8;

    if (bytes.length % 2 === 0) {
      var bigEndian = bytes.length >= 2 && bytes[0] === 0xfe && bytes[1] === 0xff;
      var utf16 = tryDecode(bytes, bigEndian ? "utf-16be" : "utf-16le");
      if (utf16 !== null) return utf16;
    }

    var cp1252 = tryDecode(bytes, "windows-1252");
    if (cp1252 !== null) return cp1252;

    return new TextDecoder("utf-8").decode(bytes);
  }

  // --------------------------------------------------------------- ZIP/DOCX

  function readUint16(bytes, offset) {
    return bytes[offset] | (bytes[offset + 1] << 8);
  }

  function readUint32(bytes, offset) {
    return (
      (bytes[offset] |
        (bytes[offset + 1] << 8) |
        (bytes[offset + 2] << 16) |
        (bytes[offset + 3] << 24)) >>> 0
    );
  }

  function findEndOfCentralDirectory(bytes) {
    // The record is 22 bytes plus a comment of at most 65535, so it lies within
    // the last 65557 bytes. Scan backwards for its signature.
    var earliest = Math.max(0, bytes.length - (22 + 65535));
    for (var offset = bytes.length - 22; offset >= earliest; offset -= 1) {
      if (readUint32(bytes, offset) === 0x06054b50) return offset;
    }
    return -1;
  }

  /**
   * Locate one member of a ZIP archive and return its stored bytes.
   *
   * Just enough of the format to read a DOCX. Sizes come from the central
   * directory because a local header may defer them to a data descriptor, and
   * Word writes members either stored or deflated. ZIP64 is rejected rather
   * than guessed at; Word does not produce it for a 5 MB document.
   */
  function findZipMember(bytes, wanted) {
    var eocd = findEndOfCentralDirectory(bytes);
    if (eocd < 0) throw badZip();

    var entryCount = readUint16(bytes, eocd + 10);
    var directoryOffset = readUint32(bytes, eocd + 16);
    if (entryCount === 0xffff || directoryOffset === 0xffffffff) {
      throw badZip("This DOCX file uses ZIP64, which this static build cannot read.");
    }

    var cursor = directoryOffset;
    var decoder = new TextDecoder("utf-8");
    for (var index = 0; index < entryCount; index += 1) {
      if (cursor + 46 > bytes.length || readUint32(bytes, cursor) !== 0x02014b50) {
        throw badZip();
      }
      var method = readUint16(bytes, cursor + 10);
      var compressedSize = readUint32(bytes, cursor + 20);
      var nameLength = readUint16(bytes, cursor + 28);
      var extraLength = readUint16(bytes, cursor + 30);
      var commentLength = readUint16(bytes, cursor + 32);
      var localOffset = readUint32(bytes, cursor + 42);
      var name = decoder.decode(bytes.subarray(cursor + 46, cursor + 46 + nameLength));

      if (name === wanted) {
        if (localOffset + 30 > bytes.length || readUint32(bytes, localOffset) !== 0x04034b50) {
          throw badZip();
        }
        var localNameLength = readUint16(bytes, localOffset + 26);
        var localExtraLength = readUint16(bytes, localOffset + 28);
        var dataStart = localOffset + 30 + localNameLength + localExtraLength;
        if (dataStart + compressedSize > bytes.length) throw badZip();
        return {
          method: method,
          data: bytes.subarray(dataStart, dataStart + compressedSize)
        };
      }

      cursor += 46 + nameLength + extraLength + commentLength;
    }
    return null;
  }

  /** Python html.unescape(), narrowed to what WordprocessingML emits. */
  function unescapeXml(value) {
    return String(value).replace(
      /&(?:#(\d+)|#[xX]([0-9a-fA-F]+)|(amp|lt|gt|quot|apos|nbsp));/g,
      function (match, decimal, hex, named) {
        if (decimal) return String.fromCodePoint(parseInt(decimal, 10));
        if (hex) return String.fromCodePoint(parseInt(hex, 16));
        return {
          amp: "&",
          lt: "<",
          gt: ">",
          quot: '"',
          apos: "'",
          nbsp: " "
        }[named];
      }
    );
  }

  /** app.py extract_docx_text(). */
  function extractDocxText(bytes, inflateRaw) {
    var member = findZipMember(bytes, "word/document.xml");
    if (!member) {
      // app.py turns zipfile's KeyError into this ValueError.
      throw apiError("The DOCX file does not contain document text.", 400);
    }

    var raw;
    if (member.method === 0) {
      raw = Promise.resolve(member.data);
    } else if (member.method === 8) {
      raw = inflateRaw(member.data);
    } else {
      raw = Promise.reject(badZip("This DOCX file uses an unsupported compression method."));
    }

    return raw.then(function (xmlBytes) {
      var xmlText = new TextDecoder("utf-8").decode(xmlBytes);
      var paragraphPattern = /<w:p\b[^>]*>([\s\S]*?)<\/w:p>/g;
      var lines = [];
      var paragraph;
      while ((paragraph = paragraphPattern.exec(xmlText)) !== null) {
        var runPattern = /<w:t\b[^>]*>([\s\S]*?)<\/w:t>/g;
        var runs = [];
        var run;
        while ((run = runPattern.exec(paragraph[1])) !== null) {
          runs.push(unescapeXml(run[1]));
        }
        if (runs.length) lines.push(runs.join(""));
      }
      return lines
        .map(function (line) { return line.trim(); })
        .filter(function (line) { return line.length > 0; })
        .join("\n");
    });
  }

  /** app.py extract_text(). */
  function extractText(filename, bytes, inflateRaw) {
    var extension = extensionOf(filename);
    if (extension === ".txt" || extension === ".md") {
      return Promise.resolve(decodeTextBytes(bytes).trim());
    }
    if (extension === ".docx") {
      return Promise.resolve()
        .then(function () {
          return extractDocxText(bytes, inflateRaw);
        })
        .then(function (text) {
          return text.trim();
        });
    }
    return Promise.reject(apiError("Unsupported document type.", 400));
  }

  // --------------------------------------------------------------- analyzer

  function countWords(text) {
    var matches = text.match(WORD_PATTERN);
    return matches ? matches.length : 0;
  }

  /** app.py snippet_for(). */
  function snippetFor(text, pattern) {
    var search = new RegExp(pattern.source, pattern.flags.replace("g", ""));
    var match = search.exec(text);
    if (!match) return "";
    var start = Math.max(0, match.index - 70);
    var end = Math.min(text.length, match.index + match[0].length + 70);
    return text.slice(start, end).replace(/\s+/g, " ").trim();
  }

  /** app.py has_section(). */
  function hasSection(text, terms) {
    for (var index = 0; index < terms.length; index += 1) {
      var term = escapeRegExp(terms[index]);
      if (new RegExp("^\\s*(?:#+\\s*)?" + term + "\\b", "im").test(text)) return true;
      if (new RegExp("\\b" + term + "\\s*:", "i").test(text)) return true;
    }
    return false;
  }

  var SECTION_CHECKS = [
    ["purpose", ["purpose", "objective"], "Purpose or objective"],
    ["scope", ["scope", "applicability"], "Scope"],
    ["owner", ["owner", "document owner", "responsible party"], "Owner"],
    ["date", ["date", "effective date", "review date"], "Date or review date"],
    ["risk", ["risk", "risks", "risk assessment"], "Risk section"],
    ["approval", ["approval", "approved by", "signature", "sign-off"], "Approval or signature"]
  ];

  var PLACEHOLDER_CHECKS = [
    ["todo", /\bTODO\b|\bTBD\b|\bTBA\b/i],
    ["insert", /\[(?:insert|add|fill in)[^\]]*\]|<\s*(?:insert|add|fill in)[^>]*>/i],
    ["blank", /_{4,}|\{\{[^}]+\}\}/]
  ];

  var VAGUE_LANGUAGE = [
    "best effort",
    "as needed",
    "reasonable",
    "as appropriate",
    "when possible",
    "from time to time"
  ];

  var LONG_SENTENCE_PATTERN = /[^.!?]{260,}[.!?]/;

  /** app.py analyze_document(). */
  function analyzeDocument(text, now) {
    var findings = [];
    var normalized = pyStr(text).trim();
    var wordCount = countWords(normalized);

    SECTION_CHECKS.forEach(function (check) {
      var key = check[0];
      var label = check[2];
      if (!hasSection(normalized, check[1])) {
        findings.push({
          id: "missing-" + key,
          severity: key === "approval" ? "high" : "medium",
          title: "Missing " + label.toLowerCase(),
          detail: "Add a clear " + label.toLowerCase() + " section or label before approval.",
          snippet: ""
        });
      }
    });

    PLACEHOLDER_CHECKS.forEach(function (check) {
      var pattern = check[1];
      if (pattern.test(normalized)) {
        findings.push({
          id: "placeholder-" + check[0],
          severity: "high",
          title: "Unresolved placeholder",
          detail: "Replace template placeholders before the document can be considered final.",
          snippet: snippetFor(normalized, pattern)
        });
      }
    });

    VAGUE_LANGUAGE.forEach(function (phrase) {
      var pattern = new RegExp("\\b" + escapeRegExp(phrase) + "\\b", "i");
      if (pattern.test(normalized)) {
        findings.push({
          id: "vague-" + phrase.split(" ").join("-"),
          severity: "medium",
          title: 'Vague language: "' + phrase + '"',
          detail: "Make the requirement measurable, accountable, or time-bound.",
          snippet: snippetFor(normalized, pattern)
        });
      }
    });

    if (wordCount < 80) {
      findings.push({
        id: "short-document",
        severity: "low",
        title: "Very short document",
        detail: "Confirm the document has enough context for reviewers and approvers.",
        snippet: ""
      });
    }

    if (LONG_SENTENCE_PATTERN.test(normalized)) {
      findings.push({
        id: "long-sentence",
        severity: "low",
        title: "Long sentence",
        detail: "Break long sentences into shorter reviewable statements.",
        snippet: snippetFor(normalized, LONG_SENTENCE_PATTERN)
      });
    }

    // app.py sorts on (severity rank, title). Compare code units rather than
    // locale: Python compares strings by code point, and these titles contain
    // quote marks that a locale-aware comparison orders differently.
    findings.sort(function (left, right) {
      if (SEVERITY_ORDER[left.severity] !== SEVERITY_ORDER[right.severity]) {
        return SEVERITY_ORDER[left.severity] - SEVERITY_ORDER[right.severity];
      }
      if (left.title === right.title) return 0;
      return left.title < right.title ? -1 : 1;
    });

    return {
      reviewed_at: now(),
      word_count: wordCount,
      findings: findings,
      counts: {
        high: findings.filter(function (item) { return item.severity === "high"; }).length,
        medium: findings.filter(function (item) { return item.severity === "medium"; }).length,
        low: findings.filter(function (item) { return item.severity === "low"; }).length
      }
    };
  }

  // ------------------------------------------------------------------ the API

  /**
   * Build an API instance over one storage backend.
   *
   * @param {object} options
   * @param {object} options.store       load/save the record store and uploads
   * @param {function} [options.now]     app.py utc_now
   * @param {function} [options.uuidHex] app.py uuid.uuid4().hex
   * @param {function} [options.inflateRaw] raw DEFLATE, for DOCX
   */
  function createApi(options) {
    var settings = options || {};
    var store = settings.store;
    var now = settings.now || defaultNow;
    var uuidHex = settings.uuidHex || defaultUuidHex;
    var inflateRaw = settings.inflateRaw || defaultInflateRaw;

    if (!store) throw new Error("createApi requires a store.");

    // ------------------------------------------------------------ migrations
    // Ported from app.py's migrate_* family. The default objects are built
    // eagerly, exactly as Python builds its `defaults` dict, so each call
    // consumes one id from `uuidHex` whether or not the id is used. The parity
    // tests depend on that: they run both implementations off the same
    // deterministic id sequence.

    function migrateReviewer(reviewer) {
      var changed = false;
      var timestamp = now();
      var defaults = {
        id: uuidHex(),
        name: "Reviewer",
        created_at: timestamp,
        updated_at: timestamp
      };
      Object.keys(defaults).forEach(function (key) {
        if (!reviewer[key]) {
          reviewer[key] = defaults[key];
          changed = true;
        }
      });
      CONTACT_FIELDS.forEach(function (field) {
        if (!hasOwn(reviewer, field)) {
          reviewer[field] = "";
          changed = true;
        }
      });
      return changed;
    }

    function migrateNotification(notification) {
      var changed = false;
      var defaults = {
        id: uuidHex(),
        recipient_type: "owner",
        recipient_name: "Owner",
        recipient_contact: emptyContact(),
        document_id: "",
        document_title: "",
        event: "notice",
        message: "",
        created_at: now(),
        read_at: null
      };
      Object.keys(defaults).forEach(function (key) {
        if (!hasOwn(notification, key)) {
          notification[key] = defaults[key];
          changed = true;
        }
      });
      if (!isPlainObject(notification.recipient_contact)) {
        notification.recipient_contact = emptyContact();
        changed = true;
      } else {
        CONTACT_FIELDS.forEach(function (field) {
          if (!hasOwn(notification.recipient_contact, field)) {
            notification.recipient_contact[field] = "";
            changed = true;
          }
        });
      }
      return changed;
    }

    function migrateAssignment(assignment) {
      var changed = false;
      var timestamp = now();
      var defaults = {
        id: uuidHex(),
        reviewer_id: "",
        reviewer_name: "Reviewer",
        reviewer_contact: emptyContact(),
        status: "pending",
        status_label: "Pending",
        assigned_at: timestamp,
        updated_at: timestamp,
        approved_at: null,
        approval_name: "",
        approval_initials: "",
        comments: []
      };
      Object.keys(defaults).forEach(function (key) {
        if (!hasOwn(assignment, key)) {
          assignment[key] = defaults[key];
          changed = true;
        }
      });
      var label = hasOwn(ASSIGNMENT_LABELS, assignment.status)
        ? ASSIGNMENT_LABELS[assignment.status]
        : assignment.status;
      if (assignment.status_label !== label) {
        assignment.status_label = label;
        changed = true;
      }
      if (!isPlainObject(assignment.reviewer_contact)) {
        assignment.reviewer_contact = emptyContact();
        changed = true;
      } else {
        CONTACT_FIELDS.forEach(function (field) {
          if (!hasOwn(assignment.reviewer_contact, field)) {
            assignment.reviewer_contact[field] = "";
            changed = true;
          }
        });
      }
      if (!Array.isArray(assignment.comments)) {
        assignment.comments = [];
        changed = true;
      }
      return changed;
    }

    /** app.py build_legacy_activity(). */
    function buildLegacyActivity(record) {
      var owner = isPlainObject(record.owner) ? record.owner : {};
      var activity = [
        {
          id: uuidHex(),
          type: "uploaded",
          actor: owner.name || "Owner",
          message: "Uploaded " + (record.filename || "document") + ".",
          created_at: record.created_at || now()
        }
      ];
      if (record.reviewed_at) {
        activity.push({
          id: uuidHex(),
          type: "review_run",
          actor: "System",
          message: "Ran the local rubric review.",
          created_at: record.reviewed_at
        });
      }
      (Array.isArray(record.comments) ? record.comments : []).forEach(function (comment) {
        activity.push({
          id: uuidHex(),
          type: "comment_added",
          actor: comment.author || "Reviewer",
          message: "Commented: " + pyStr(comment.body).slice(0, 120),
          created_at: comment.created_at || now()
        });
      });
      if (record.approved_at) {
        activity.push({
          id: uuidHex(),
          type: "approved",
          actor: "Reviewer",
          message: "Approved the document.",
          created_at: record.approved_at
        });
      }
      return sortByAsc(activity, function (item) { return item.created_at; });
    }

    function migrateDocument(record) {
      var changed = false;
      var timestamp = now();
      var defaults = {
        id: uuidHex(),
        filename: "document",
        extension: ".txt",
        status: "uploaded",
        created_at: timestamp,
        updated_at: timestamp,
        reviewed_at: null,
        approved_at: null,
        word_count: 0,
        findings: [],
        comments: []
      };
      Object.keys(defaults).forEach(function (key) {
        if (!hasOwn(record, key)) {
          record[key] = defaults[key];
          changed = true;
        }
      });

      if (!isPlainObject(record.owner)) {
        record.owner = ownerFromPayload({});
        changed = true;
      } else {
        var owner = ownerFromPayload(record.owner);
        if (JSON.stringify(owner) !== JSON.stringify(record.owner)) {
          record.owner = owner;
          changed = true;
        }
      }

      if (!Array.isArray(record.assignments)) {
        record.assignments = [];
        changed = true;
      }
      record.assignments.forEach(function (assignment) {
        changed = migrateAssignment(assignment) || changed;
      });

      if (!Array.isArray(record.activity) || record.activity.length === 0) {
        record.activity = buildLegacyActivity(record);
        changed = true;
      }

      return changed;
    }

    function migrateDb(data) {
      var changed = false;
      if (!Array.isArray(data.documents)) {
        data.documents = [];
        changed = true;
      }
      if (!Array.isArray(data.reviewers)) {
        data.reviewers = [];
        changed = true;
      }
      if (!Array.isArray(data.notifications)) {
        data.notifications = [];
        changed = true;
      }
      data.reviewers.forEach(function (reviewer) {
        changed = migrateReviewer(reviewer) || changed;
      });
      data.notifications.forEach(function (notification) {
        changed = migrateNotification(notification) || changed;
      });
      data.documents.forEach(function (record) {
        changed = migrateDocument(record) || changed;
      });
      return changed;
    }

    /** app.py load_db(): read, migrate, and write back when migration ran. */
    function loadDb() {
      return Promise.resolve(store.load()).then(function (loaded) {
        var data = isPlainObject(loaded)
          ? loaded
          : { documents: [], reviewers: [], notifications: [] };
        if (migrateDb(data)) {
          return Promise.resolve(store.save(data)).then(function () {
            return data;
          });
        }
        return data;
      });
    }

    function saveDb(data) {
      return Promise.resolve(store.save(data));
    }

    // --------------------------------------------------------- record shapes

    /** app.py add_activity(). */
    function addActivity(record, eventType, actor, message, timestamp) {
      if (!Array.isArray(record.activity)) record.activity = [];
      record.activity.push({
        id: uuidHex(),
        type: eventType,
        actor: cleanText(actor, "System", 120),
        message: cleanText(message, "", 500),
        created_at: timestamp || now()
      });
    }

    /** app.py assignment_counts(). */
    function assignmentCounts(record) {
      var counts = { pending: 0, commented: 0, changes_requested: 0, approved: 0 };
      (record.assignments || []).forEach(function (assignment) {
        var status = assignment.status || "pending";
        counts[status] = (hasOwn(counts, status) ? counts[status] : 0) + 1;
      });
      return counts;
    }

    /** app.py recalculate_document_status(). */
    function recalculateDocumentStatus(record) {
      var assignments = record.assignments || [];
      if (!assignments.length) return;

      var statuses = assignments.map(function (assignment) {
        return assignment.status || "pending";
      });
      if (statuses.indexOf("changes_requested") !== -1) {
        record.status = "changes_requested";
        record.approved_at = null;
        return;
      }
      var allApproved = statuses.every(function (status) { return status === "approved"; });
      if (allApproved) {
        record.status = "approved";
        record.approved_at = record.approved_at || now();
        return;
      }
      record.status = "in_review";
      record.approved_at = null;
    }

    /** app.py public_assignment(). */
    function publicAssignment(assignment) {
      return {
        id: assignment.id,
        reviewer_id: assignment.reviewer_id,
        reviewer_name: assignment.reviewer_name,
        reviewer_contact: assignment.reviewer_contact || emptyContact(),
        status: assignment.status,
        status_label: hasOwn(ASSIGNMENT_LABELS, assignment.status)
          ? ASSIGNMENT_LABELS[assignment.status]
          : assignment.status,
        assigned_at: assignment.assigned_at,
        updated_at: assignment.updated_at,
        approved_at: assignment.approved_at === undefined ? null : assignment.approved_at,
        approval_name: assignment.approval_name || "",
        approval_initials: assignment.approval_initials || "",
        comments: assignment.comments || []
      };
    }

    /** app.py public_document(). */
    function publicDocument(record, includeText) {
      var view = {
        id: record.id,
        filename: record.filename,
        extension: record.extension,
        status: record.status,
        status_label: hasOwn(STATUS_LABELS, record.status)
          ? STATUS_LABELS[record.status]
          : record.status,
        created_at: record.created_at,
        updated_at: record.updated_at,
        reviewed_at: record.reviewed_at === undefined ? null : record.reviewed_at,
        approved_at: record.approved_at === undefined ? null : record.approved_at,
        word_count: record.word_count === undefined ? 0 : record.word_count,
        findings: record.findings || [],
        comments: record.comments || [],
        owner: isPlainObject(record.owner) ? record.owner : ownerFromPayload({}),
        assignments: (record.assignments || []).map(publicAssignment),
        assignment_counts: assignmentCounts(record),
        activity: sortByDesc(record.activity || [], "created_at")
      };
      if (includeText) {
        view.text = record.text || "";
      }
      return view;
    }

    /** app.py public_reviewer(). */
    function publicReviewer(reviewer) {
      return {
        id: reviewer.id,
        name: reviewer.name,
        email: reviewer.email || "",
        slack: reviewer.slack || "",
        teams: reviewer.teams || "",
        created_at: reviewer.created_at,
        updated_at: reviewer.updated_at
      };
    }

    /** app.py public_notification(). */
    function publicNotification(notification) {
      return {
        id: notification.id,
        recipient_type: notification.recipient_type,
        recipient_name: notification.recipient_name,
        recipient_contact: notification.recipient_contact || emptyContact(),
        document_id: notification.document_id,
        document_title: notification.document_title,
        event: notification.event,
        message: notification.message,
        created_at: notification.created_at,
        read_at: notification.read_at === undefined ? null : notification.read_at
      };
    }

    function findDocument(data, documentId) {
      return data.documents.filter(function (record) {
        return record.id === documentId;
      })[0] || null;
    }

    function findReviewer(data, reviewerId) {
      return data.reviewers.filter(function (reviewer) {
        return reviewer.id === reviewerId;
      })[0] || null;
    }

    function findAssignment(record, reviewerId) {
      return (record.assignments || []).filter(function (assignment) {
        return assignment.reviewer_id === reviewerId;
      })[0] || null;
    }

    /** app.py reviewer_payload(). */
    function reviewerPayload(payload, existing) {
      var reviewer = {};
      if (existing) {
        Object.keys(existing).forEach(function (key) {
          reviewer[key] = existing[key];
        });
      }
      reviewer.name = cleanText(payload.name, "", 120);
      if (!reviewer.name) throw apiError("Reviewer name is required.", 400);
      var contact = normalizeContact(payload);
      CONTACT_FIELDS.forEach(function (field) {
        reviewer[field] = contact[field];
      });
      return reviewer;
    }

    /** app.py build_assignment(). */
    function buildAssignment(reviewer) {
      var timestamp = now();
      var assignment = {
        id: uuidHex(),
        reviewer_id: reviewer.id,
        reviewer_name: reviewer.name,
        reviewer_contact: normalizeContact(reviewer),
        status: "pending",
        status_label: "Pending",
        assigned_at: timestamp,
        updated_at: timestamp,
        approved_at: null,
        approval_name: "",
        approval_initials: "",
        comments: []
      };
      migrateAssignment(assignment);
      return assignment;
    }

    /** app.py create_notification(). */
    function createNotification(data, record, recipientType, recipientName, recipientContact, event, message) {
      var notification = {
        id: uuidHex(),
        recipient_type: recipientType,
        recipient_name: cleanText(recipientName, "Recipient", 120),
        recipient_contact: normalizeContact(recipientContact),
        document_id: record.id,
        document_title: record.filename,
        event: event,
        message: cleanText(message, "", 1000),
        created_at: now(),
        read_at: null
      };
      if (!Array.isArray(data.notifications)) data.notifications = [];
      data.notifications.push(notification);
      addActivity(
        record,
        "notification",
        "System",
        "Queued notification for " + notification.recipient_name + ": " + notification.message,
        notification.created_at
      );
      return notification;
    }

    // ------------------------------------------------------------- responses

    function jsonResponse(payload, status) {
      return {
        status: status || 200,
        headers: { "Content-Type": "application/json; charset=utf-8" },
        body: JSON.stringify(payload)
      };
    }

    function errorResponse(message, status) {
      return jsonResponse({ error: message }, status || 400);
    }

    function notFound(message) {
      return errorResponse(message || "Not found.", 404);
    }

    function parseJsonBody(body) {
      // app.py read_json_body(): an empty body is {}, malformed JSON is a 400.
      if (body === null || body === undefined || body === "") return {};
      if (isPlainObject(body)) return body;
      try {
        var parsed = JSON.parse(body);
        return isPlainObject(parsed) ? parsed : {};
      } catch (error) {
        throw apiError("Request body must be valid JSON.", 400);
      }
    }

    // -------------------------------------------------------------- handlers

    function handleDocumentsIndex() {
      return loadDb().then(function (data) {
        var documents = data.documents.map(function (record) {
          return publicDocument(record, false);
        });
        return jsonResponse({ documents: sortByDesc(documents, "updated_at") });
      });
    }

    function handleReviewersIndex() {
      return loadDb().then(function (data) {
        var reviewers = data.reviewers.map(publicReviewer);
        return jsonResponse({
          reviewers: sortByAsc(reviewers, function (reviewer) {
            return String(reviewer.name).toLowerCase();
          })
        });
      });
    }

    function handleNotificationsIndex() {
      return loadDb().then(function (data) {
        var notifications = sortByDesc(data.notifications.map(publicNotification), "created_at");
        var unread = notifications.filter(function (item) { return !item.read_at; }).length;
        return jsonResponse({ notifications: notifications, unread_count: unread });
      });
    }

    function handleDocumentDetail(documentId) {
      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");
        return jsonResponse(publicDocument(record, true));
      });
    }

    function handleDownload(documentId) {
      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");
        return Promise.resolve(store.getUpload(record.stored_name)).then(function (bytes) {
          if (!bytes) return notFound("Original upload is missing.");
          var extension = extensionOf(record.filename);
          return {
            status: 200,
            headers: {
              "Content-Type": DOWNLOAD_TYPES[extension] || "application/octet-stream",
              "Content-Disposition": 'attachment; filename="' + record.filename + '"'
            },
            bytes: bytes,
            filename: record.filename
          };
        });
      });
    }

    /** app.py handle_upload(). */
    function handleUpload(upload) {
      if (!upload || !upload.bytes) throw apiError("Upload cannot be empty.", 400);
      // app.py measures Content-Length, so its 5 MB ceiling covers the whole
      // multipart request - the file plus a few hundred bytes of part headers.
      // There is no request here, so the file itself is what gets measured,
      // which makes this marginally more permissive for a file within a few
      // hundred bytes of the limit.
      if (upload.bytes.length > MAX_UPLOAD_BYTES) {
        throw apiError("Upload is too large. Maximum size is 5 MB.", 400);
      }

      var fields = upload.fields || {};
      var filename = sanitizeFilename(upload.filename);
      var extension = extensionOf(filename);
      if (ALLOWED_EXTENSIONS.indexOf(extension) === -1) {
        return Promise.resolve(
          errorResponse("Unsupported file type. Upload TXT, MD, or DOCX.", 415)
        );
      }
      if (upload.bytes.length === 0) throw apiError("Uploaded file is empty.", 400);

      return extractText(filename, upload.bytes, inflateRaw).then(function (text) {
        if (!text) throw apiError("No readable text was found in the document.", 400);

        var documentId = uuidHex();
        var storedName = documentId + extension;

        return Promise.resolve(store.putUpload(storedName, upload.bytes)).then(function () {
          var timestamp = now();
          var owner = ownerFromPayload({
            name: fields.owner_name || fields.owner,
            email: fields.owner_email,
            slack: fields.owner_slack,
            teams: fields.owner_teams
          });
          var record = {
            id: documentId,
            filename: filename,
            stored_name: storedName,
            extension: extension,
            status: "uploaded",
            created_at: timestamp,
            updated_at: timestamp,
            reviewed_at: null,
            approved_at: null,
            word_count: countWords(text),
            text: text,
            findings: [],
            comments: [],
            owner: owner,
            assignments: [],
            activity: []
          };
          addActivity(record, "uploaded", owner.name, "Uploaded " + filename + ".", timestamp);

          return loadDb().then(function (data) {
            data.documents.push(record);
            return saveDb(data).then(function () {
              return jsonResponse(publicDocument(record, true), 201);
            });
          });
        });
      });
    }

    /** app.py handle_review(). */
    function handleReview(documentId) {
      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");
        var result = analyzeDocument(record.text || "", now);
        record.findings = result.findings;
        record.reviewed_at = result.reviewed_at;
        record.word_count = result.word_count;
        if (record.status !== "approved") record.status = "in_review";
        record.updated_at = now();
        addActivity(record, "review_run", "System", "Ran the local rubric review.", result.reviewed_at);
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_comment(). */
    function handleComment(documentId, body) {
      var payload = parseJsonBody(body);
      var text = cleanText(payload.body, "", 2000);
      var author = cleanText(payload.author, "Reviewer", 80);
      if (!text) throw apiError("Comment body is required.", 400);

      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");

        var timestamp = now();
        if (!Array.isArray(record.comments)) record.comments = [];
        record.comments.push({
          id: uuidHex(),
          author: author,
          body: text,
          created_at: timestamp
        });
        record.updated_at = timestamp;
        addActivity(record, "comment_added", author, "Commented: " + text.slice(0, 120), timestamp);
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_status(). */
    function handleStatus(documentId, status) {
      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");

        var owner = isPlainObject(record.owner) ? record.owner : {};
        record.status = status;
        record.updated_at = now();
        if (status === "approved") {
          record.approved_at = now();
          addActivity(record, "approved", owner.name || "Owner", "Owner approved the document.");
        } else {
          record.approved_at = null;
          addActivity(record, "changes_requested", owner.name || "Owner", "Owner requested changes.");
        }
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_create_reviewer(). */
    function handleCreateReviewer(body) {
      var payload = parseJsonBody(body);
      var timestamp = now();
      var reviewer = reviewerPayload(payload, null);
      reviewer.id = uuidHex();
      reviewer.created_at = timestamp;
      reviewer.updated_at = timestamp;
      return loadDb().then(function (data) {
        data.reviewers.push(reviewer);
        return saveDb(data).then(function () {
          return jsonResponse(publicReviewer(reviewer), 201);
        });
      });
    }

    /** app.py handle_update_reviewer(). */
    function handleUpdateReviewer(reviewerId, body) {
      return loadDb().then(function (data) {
        var reviewer = findReviewer(data, reviewerId);
        if (!reviewer) return notFound("Reviewer not found.");
        var updated = reviewerPayload(parseJsonBody(body), reviewer);
        Object.keys(updated).forEach(function (key) {
          reviewer[key] = updated[key];
        });
        reviewer.updated_at = now();
        return saveDb(data).then(function () {
          return jsonResponse(publicReviewer(reviewer));
        });
      });
    }

    /** app.py handle_delete_reviewer(). */
    function handleDeleteReviewer(reviewerId) {
      return loadDb().then(function (data) {
        var before = data.reviewers.length;
        data.reviewers = data.reviewers.filter(function (reviewer) {
          return reviewer.id !== reviewerId;
        });
        if (data.reviewers.length === before) return notFound("Reviewer not found.");
        return saveDb(data).then(function () {
          return jsonResponse({ ok: true });
        });
      });
    }

    /** app.py handle_assign_reviewers(). */
    function handleAssignReviewers(documentId, body) {
      var payload = parseJsonBody(body);
      var requested = payload.reviewer_ids === undefined ? [] : payload.reviewer_ids;
      if (!Array.isArray(requested)) throw apiError("reviewer_ids must be a list.", 400);

      var reviewerIds = [];
      requested.forEach(function (item) {
        var id = pyStr(item);
        if (!id.trim()) return;
        if (reviewerIds.indexOf(id) === -1) reviewerIds.push(id);
      });

      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) return notFound("Document not found.");

        var reviewersById = {};
        data.reviewers.forEach(function (reviewer) {
          reviewersById[reviewer.id] = reviewer;
        });
        var missing = reviewerIds.filter(function (id) {
          return !hasOwn(reviewersById, id);
        });
        if (missing.length) {
          throw apiError("One or more selected reviewers no longer exists.", 400);
        }

        var existingById = {};
        (record.assignments || []).forEach(function (assignment) {
          existingById[assignment.reviewer_id] = assignment;
        });

        var assignments = [];
        var created = [];
        reviewerIds.forEach(function (id) {
          if (hasOwn(existingById, id)) {
            assignments.push(existingById[id]);
          } else {
            var assignment = buildAssignment(reviewersById[id]);
            assignments.push(assignment);
            created.push(assignment);
          }
        });
        record.assignments = assignments;

        var timestamp = now();
        record.updated_at = timestamp;
        if (reviewerIds.length) {
          record.status = "in_review";
          var names = assignments.map(function (assignment) {
            return assignment.reviewer_name;
          }).join(", ");
          addActivity(record, "reviewers_assigned", record.owner.name, "Assigned reviewers: " + names + ".", timestamp);
        } else {
          record.status = record.reviewed_at ? "in_review" : "uploaded";
          record.approved_at = null;
          addActivity(record, "reviewers_assigned", record.owner.name, "Cleared reviewer assignments.", timestamp);
        }

        created.forEach(function (assignment) {
          var message =
            "Please review " + record.filename + " in SimpleDocReview. " +
            "Open the local app, select the document, and respond as " + assignment.reviewer_name + ".";
          createNotification(
            data,
            record,
            "reviewer",
            assignment.reviewer_name,
            assignment.reviewer_contact,
            "review_assigned",
            message
          );
        });

        recalculateDocumentStatus(record);
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /**
     * app.py require_assignment().
     *
     * Note the status quirk this preserves: a missing document reaches the
     * client as a 400 here, not the 404 that GET /api/documents/<id> returns,
     * because upstream raises ValueError rather than replying directly.
     */
    function requireAssignment(documentId, payload) {
      var reviewerId = cleanText(payload.reviewer_id, "", 80);
      if (!reviewerId) throw apiError("Reviewer is required.", 400);
      return loadDb().then(function (data) {
        var record = findDocument(data, documentId);
        if (!record) throw apiError("Document not found.", 400);
        var assignment = findAssignment(record, reviewerId);
        if (!assignment) throw apiError("Reviewer is not assigned to this document.", 400);
        return { data: data, record: record, assignment: assignment };
      });
    }

    /** app.py handle_reviewer_comment(). */
    function handleReviewerComment(documentId, body) {
      var payload = parseJsonBody(body);
      return requireAssignment(documentId, payload).then(function (context) {
        var data = context.data;
        var record = context.record;
        var assignment = context.assignment;
        var text = cleanText(payload.body, "", 2000);
        var signature = cleanText(payload.signature, assignment.reviewer_name, 120);
        if (!text) throw apiError("Comment body is required.", 400);

        var timestamp = now();
        var comment = {
          id: uuidHex(),
          author: signature,
          reviewer_id: assignment.reviewer_id,
          body: text,
          created_at: timestamp
        };
        if (!Array.isArray(assignment.comments)) assignment.comments = [];
        assignment.comments.push(comment);
        if (assignment.status !== "approved" && assignment.status !== "changes_requested") {
          assignment.status = "commented";
        }
        assignment.updated_at = timestamp;
        migrateAssignment(assignment);
        if (!Array.isArray(record.comments)) record.comments = [];
        record.comments.push(comment);
        record.updated_at = timestamp;
        addActivity(record, "reviewer_comment", signature, "Commented: " + text.slice(0, 120), timestamp);
        createNotification(
          data,
          record,
          "owner",
          record.owner.name,
          record.owner,
          "reviewer_comment",
          signature + " commented on " + record.filename + ": " + text.slice(0, 180)
        );
        recalculateDocumentStatus(record);
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_reviewer_approve(). */
    function handleReviewerApprove(documentId, body) {
      var payload = parseJsonBody(body);
      return requireAssignment(documentId, payload).then(function (context) {
        var data = context.data;
        var record = context.record;
        var assignment = context.assignment;
        var signature = cleanText(payload.signature, "", 120);
        if (!signature) throw apiError("Approval name or initials are required.", 400);

        var wasFinal = record.status === "approved";
        var timestamp = now();
        assignment.status = "approved";
        assignment.approval_name = signature;
        assignment.approval_initials = cleanText(payload.initials || signature, "", 24);
        assignment.approved_at = timestamp;
        assignment.updated_at = timestamp;
        migrateAssignment(assignment);
        record.updated_at = timestamp;
        addActivity(record, "reviewer_approved", signature, "Approved as " + signature + ".", timestamp);
        recalculateDocumentStatus(record);
        if (record.status === "approved" && !wasFinal) {
          addActivity(
            record,
            "approved",
            "System",
            "All assigned reviewers approved the document.",
            record.approved_at
          );
        }
        createNotification(
          data,
          record,
          "owner",
          record.owner.name,
          record.owner,
          "reviewer_approved",
          signature + " approved " + record.filename + "."
        );
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_reviewer_request_changes(). */
    function handleReviewerRequestChanges(documentId, body) {
      var payload = parseJsonBody(body);
      return requireAssignment(documentId, payload).then(function (context) {
        var data = context.data;
        var record = context.record;
        var assignment = context.assignment;
        var text = cleanText(payload.body, "", 2000);
        var signature = cleanText(payload.signature, assignment.reviewer_name, 120);
        if (!text) throw apiError("A change request note is required.", 400);

        var timestamp = now();
        assignment.status = "changes_requested";
        assignment.approved_at = null;
        assignment.approval_name = "";
        assignment.approval_initials = "";
        assignment.updated_at = timestamp;
        var comment = {
          id: uuidHex(),
          author: signature,
          reviewer_id: assignment.reviewer_id,
          body: text,
          created_at: timestamp
        };
        if (!Array.isArray(assignment.comments)) assignment.comments = [];
        assignment.comments.push(comment);
        migrateAssignment(assignment);
        if (!Array.isArray(record.comments)) record.comments = [];
        record.comments.push(comment);
        record.updated_at = timestamp;
        recalculateDocumentStatus(record);
        addActivity(
          record,
          "reviewer_changes_requested",
          signature,
          "Requested changes: " + text.slice(0, 120),
          timestamp
        );
        createNotification(
          data,
          record,
          "owner",
          record.owner.name,
          record.owner,
          "reviewer_changes_requested",
          signature + " requested changes on " + record.filename + ": " + text.slice(0, 180)
        );
        return saveDb(data).then(function () {
          return jsonResponse(publicDocument(record, true));
        });
      });
    }

    /** app.py handle_notification_read(). */
    function handleNotificationRead(notificationId) {
      return loadDb().then(function (data) {
        var notification = data.notifications.filter(function (item) {
          return item.id === notificationId;
        })[0];
        if (!notification) return notFound("Notification not found.");
        notification.read_at = notification.read_at || now();
        return saveDb(data).then(function () {
          return jsonResponse(publicNotification(notification));
        });
      });
    }

    // ----------------------------------------------------------------- router
    // Mirrors app.py's do_GET / do_POST / do_PUT / do_DELETE dispatch, in the
    // same order, so an unmatched path produces the same 404 body.

    function pathParts(pathname) {
      return String(pathname)
        .split("?")[0]
        .split("#")[0]
        .split("/")
        .filter(function (part) { return part.length > 0; })
        .map(function (part) { return decodeURIComponent(part); });
    }

    function route(method, pathname, body) {
      var parts = pathParts(pathname);
      var verb = String(method || "GET").toUpperCase();

      if (verb === "GET") {
        if (parts.length === 2 && parts[0] === "api") {
          if (parts[1] === "documents") return handleDocumentsIndex();
          if (parts[1] === "reviewers") return handleReviewersIndex();
          if (parts[1] === "notifications") return handleNotificationsIndex();
        }
        if (parts.length === 3 && parts[0] === "api" && parts[1] === "documents") {
          return handleDocumentDetail(parts[2]);
        }
        if (parts.length === 4 && parts[0] === "api" && parts[1] === "documents" && parts[3] === "download") {
          return handleDownload(parts[2]);
        }
        return Promise.resolve(notFound());
      }

      if (verb === "POST") {
        if (parts.length === 2 && parts[0] === "api" && parts[1] === "upload") {
          return handleUpload(body);
        }
        if (parts.length === 2 && parts[0] === "api" && parts[1] === "reviewers") {
          return handleCreateReviewer(body);
        }
        if (parts.length === 4 && parts[0] === "api" && parts[1] === "notifications" && parts[3] === "read") {
          return handleNotificationRead(parts[2]);
        }
        if (parts.length === 4 && parts[0] === "api" && parts[1] === "documents") {
          var documentId = parts[2];
          var action = parts[3];
          if (action === "review") return handleReview(documentId);
          if (action === "comments") return handleComment(documentId, body);
          if (action === "approve") return handleStatus(documentId, "approved");
          if (action === "request-changes") return handleStatus(documentId, "changes_requested");
          if (action === "assign-reviewers") return handleAssignReviewers(documentId, body);
          if (action === "reviewer-comment") return handleReviewerComment(documentId, body);
          if (action === "reviewer-approve") return handleReviewerApprove(documentId, body);
          if (action === "reviewer-request-changes") return handleReviewerRequestChanges(documentId, body);
        }
        return Promise.resolve(notFound());
      }

      if (verb === "PUT") {
        if (parts.length === 3 && parts[0] === "api" && parts[1] === "reviewers") {
          return handleUpdateReviewer(parts[2], body);
        }
        return Promise.resolve(notFound());
      }

      if (verb === "DELETE") {
        if (parts.length === 3 && parts[0] === "api" && parts[1] === "reviewers") {
          return handleDeleteReviewer(parts[2]);
        }
        return Promise.resolve(notFound());
      }

      return Promise.resolve(notFound());
    }

    // One request at a time. app.py serializes on the file it rewrites; here
    // every handler is a read-modify-write against the same store, and the app
    // fires three GETs in parallel on load, so interleaving them would let one
    // response overwrite another's changes.
    var queue = Promise.resolve();

    function handle(method, pathname, body) {
      var result = queue.then(function () {
        return Promise.resolve()
          .then(function () {
            return route(method, pathname, body);
          })
          .catch(function (error) {
            if (error && error.apiStatus) {
              return errorResponse(error.message, error.apiStatus);
            }
            throw error;
          });
      });
      // Keep the chain alive even when a request rejects, and never let a
      // rejection here surface as an unhandled promise.
      queue = result.then(function () { return undefined; }, function () { return undefined; });
      return result;
    }

    return {
      handle: handle,
      isApiPath: function (pathname) {
        var parts = pathParts(pathname);
        return parts[0] === "api";
      },
      // Exposed for the parity tests and for debugging in the browser console.
      internals: {
        analyzeDocument: function (text) { return analyzeDocument(text, now); },
        extractText: function (filename, bytes) { return extractText(filename, bytes, inflateRaw); },
        sanitizeFilename: sanitizeFilename,
        decodeTextBytes: decodeTextBytes,
        cleanText: cleanText,
        countWords: countWords,
        publicDocument: publicDocument,
        loadDb: loadDb
      }
    };
  }

  return {
    createApi: createApi,
    MAX_UPLOAD_BYTES: MAX_UPLOAD_BYTES,
    ALLOWED_EXTENSIONS: ALLOWED_EXTENSIONS,
    STATUS_LABELS: STATUS_LABELS,
    ASSIGNMENT_LABELS: ASSIGNMENT_LABELS,
    defaultNow: defaultNow,
    defaultUuidHex: defaultUuidHex,
    defaultInflateRaw: defaultInflateRaw,
    sanitizeFilename: sanitizeFilename,
    decodeTextBytes: decodeTextBytes,
    cleanText: cleanText
  };
});