// Second Thoughts — front end.
// Conversation state lives only in this tab's memory: no localStorage, no
// analytics, nothing written to disk. Closing the tab ends it.

const scroll = document.getElementById("scroll");
const thread = document.getElementById("thread");
const form = document.getElementById("composer");
const input = document.getElementById("msg");
const sendBtn = document.getElementById("send");
const starters = document.getElementById("starters");
const startersLabel = document.getElementById("starters-label");
const optional = document.getElementById("optional");
const hint = document.getElementById("hint");

const path = document.getElementById("path");

/** @type {{role: "user"|"assistant", content: string}[]} */
const messages = [];
let busy = false;

// Practice mode. `mode` is sent with each request; "practice_end" is a
// one-shot note that the person stopped, so the model returns to listening.
const practice = { active: false, step: 0, draft: "", endNote: false, breathed: false };

const MARKER = /\[\[step:(\d|done)\]\]/g;
// Hide markers from the person, including one still arriving mid-stream.
function visible(text) {
  return text.replace(MARKER, "").replace(/\[\[[^\]]*$/, "").trimEnd();
}

function atBottom() {
  return scroll.scrollHeight - scroll.scrollTop - scroll.clientHeight < 80;
}

function scrollDown() {
  scroll.scrollTop = scroll.scrollHeight;
}

function bubble(kind, text) {
  const el = document.createElement("div");
  el.className = `bubble bubble--${kind}`;
  el.textContent = text;
  thread.appendChild(el);
  scrollDown();
  return el;
}

function typingIndicator() {
  const el = document.createElement("div");
  el.className = "bubble bubble--them";
  el.innerHTML = '<span class="typing"><span></span><span></span><span></span></span>';
  thread.appendChild(el);
  scrollDown();
  return el;
}

// Once the conversation starts, the starter prompts have done their job. The
// optional doors are the exception — both act on what was already shared, so
// they only become useful now. Dock them instead of dropping them.
function retireStarters() {
  for (const el of [starters, startersLabel, hint]) {
    if (el) el.remove();
  }
  if (optional) optional.classList.add("optional--docked");
}

function fromTemplate(id) {
  const node = document.getElementById(id).content.firstElementChild.cloneNode(true);
  thread.appendChild(node);
  scrollDown();
  return node;
}

function renderPath() {
  for (const li of path.querySelectorAll("li")) {
    const n = Number(li.dataset.step);
    li.classList.toggle("is-done", n < practice.step);
    li.classList.toggle("is-current", n === practice.step);
    if (n === practice.step) li.setAttribute("aria-current", "step");
    else li.removeAttribute("aria-current");
  }
}

function setPractice(active) {
  practice.active = active;
  path.hidden = !active;
  optional.hidden = active;
  if (active) path.classList.add("optional--docked");
  renderPath();
}

function beginPractice() {
  Object.assign(practice, { step: 1, draft: "", endNote: false, breathed: false });
  setPractice(true);
  send("I'd like to practice saying it to someone.");
}

function stopPractice() {
  setPractice(false);
  practice.endNote = true;
  bubble("notice", "Practice stopped. That counts — you can start again anytime, or just keep talking here.");
}

function finishPractice() {
  setPractice(false);
  const card = fromTemplate("practice-done");
  if (practice.draft) {
    card.querySelector(".pcard__draft").hidden = false;
    card.querySelector(".pcard__quote").textContent = practice.draft;
  }
}

// Apply the step marker from a finished reply.
function advance(reply) {
  const marks = [...reply.matchAll(MARKER)];
  if (!practice.active || !marks.length) return;
  const mark = marks[marks.length - 1][1];
  if (mark === "done") return finishPractice();
  practice.step = Number(mark);
  renderPath();
  if (practice.step === 4 && !practice.breathed) {
    practice.breathed = true;
    fromTemplate("breathe");
  }
}

function setBusy(state) {
  busy = state;
  sendBtn.disabled = state;
  input.disabled = state;
  if (!state) input.focus();
}

function autoGrow() {
  input.style.height = "auto";
  input.style.height = `${Math.min(input.scrollHeight, 120)}px`;
}

async function send(text) {
  const content = text.trim();
  if (!content || busy) return;

  retireStarters();
  bubble("you", content);
  messages.push({ role: "user", content });

  // What they say while on "Say it" is the draft they get to keep.
  if (practice.active && practice.step === 2) practice.draft = content;

  let mode;
  if (practice.active) mode = "practice";
  else if (practice.endNote) mode = "practice_end";
  practice.endNote = false;

  input.value = "";
  autoGrow();
  setBusy(true);

  const pending = typingIndicator();
  let reply = "";
  let target = null;

  const fail = (message) => {
    pending.remove();
    if (target) target.remove();
    bubble("notice", message);
    // Drop the unanswered turn so a retry doesn't double up.
    messages.pop();
  };

  try {
    const res = await fetch("/api/chat", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ messages, mode }),
    });

    if (!res.ok || !res.body) {
      let message = "I couldn't reach the other side of this just now. Try again in a moment.";
      try {
        const body = await res.json();
        if (body && body.error) message = body.error;
      } catch (_) {
        /* keep the default */
      }
      fail(message);
      setBusy(false);
      return;
    }

    const reader = res.body.getReader();
    const decoder = new TextDecoder();
    let buffer = "";
    let failed = false;

    while (true) {
      const { value, done } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });
      const chunks = buffer.split("\n\n");
      buffer = chunks.pop() || "";

      for (const chunk of chunks) {
        const line = chunk.trim();
        if (!line.startsWith("data:")) continue;

        let event;
        try {
          event = JSON.parse(line.slice(5).trim());
        } catch (_) {
          continue;
        }

        if (event.type === "delta") {
          const stick = atBottom();
          if (!target) {
            pending.remove();
            target = bubble("them", "");
          }
          reply += event.text;
          target.textContent = visible(reply);
          if (stick) scrollDown();
        } else if (event.type === "error") {
          fail(event.message);
          failed = true;
        }
      }
    }

    if (failed) {
      setBusy(false);
      return;
    }

    pending.remove();
    if (reply.trim()) {
      // Keep markers in history so the model can see where the steps stand.
      messages.push({ role: "assistant", content: reply });
      advance(reply);
    } else if (!target) {
      fail("I went quiet there, which wasn't intentional. Try sending that again.");
    }
  } catch (_) {
    fail("The connection dropped. Whatever you typed is still yours — try again when you're ready.");
  } finally {
    setBusy(false);
  }
}

form.addEventListener("submit", (e) => {
  e.preventDefault();
  send(input.value);
});

// Enter sends; Shift+Enter makes a new line. On touch keyboards the return
// key should insert a newline instead, so people can write more than a line.
input.addEventListener("keydown", (e) => {
  const touch = window.matchMedia("(pointer: coarse)").matches;
  if (e.key === "Enter" && !e.shiftKey && !touch) {
    e.preventDefault();
    send(input.value);
  }
});

input.addEventListener("input", autoGrow);

for (const btn of document.querySelectorAll("[data-send]")) {
  btn.addEventListener("click", () => send(btn.dataset.send));
}

document.addEventListener("click", (e) => {
  const btn = e.target.closest("[data-action]");
  if (!btn || busy) return;
  const action = btn.dataset.action;
  if (action === "practice-intro") {
    retireStarters();
    fromTemplate("practice-intro");
  } else if (action === "practice-begin") {
    btn.closest(".pcard").classList.add("pcard--started");
    btn.remove();
    beginPractice();
  } else if (action === "practice-stop") {
    stopPractice();
  } else if (action === "copy-draft") {
    navigator.clipboard?.writeText(practice.draft).then(
      () => { btn.textContent = "Copied"; },
      () => { btn.textContent = "Couldn't copy — select the text instead"; },
    );
  }
});

// "How this space works" sheet.
for (const btn of document.querySelectorAll("[data-open]")) {
  btn.addEventListener("click", () => document.getElementById(btn.dataset.open).showModal());
}
for (const dlg of document.querySelectorAll("dialog")) {
  dlg.querySelector("[data-close]").addEventListener("click", () => dlg.close());
  // Tapping the dimmed backdrop closes it too.
  dlg.addEventListener("click", (e) => { if (e.target === dlg) dlg.close(); });
}