/* ingest.js — copy a GGUF from a URL into OPFS in an engine's own layout, streaming: HTTP Range requests of
 * ≤1 GiB, each unit transformed and written while the next bytes arrive (at most 8 writes in flight). OPFS quota
 * grows with what is written, so files grow by writes rather than one up-front truncate. The manifest is written
 * incomplete first and complete last, so an interrupted ingest is never taken as valid. After each range request the
 * manifest records the first unit not yet written; a later call with the same key and the same GGUF header resumes
 * from there instead of from byte 0.
 * Extracted from LocalMind's qwen3_moe_ssd.js (2026-10-05); `root` and `format` are new options (LocalMind
 * passes 'localmind-ssd' and its own format string).
 *
 *   const manifest = await ingestGguf({ url, key, plan: { layout, units }, onProgress });
 *   // OPFS: <root>/<key>/{header.bin, dense.bin, experts.bin, manifest.json}
 */

import { OpfsWriter, readOpfsText, writeOpfsText, removeOpfs } from './opfs-reader.js';
import { parseGguf, splitQ8, splitQ4, Q8_BLOCK, Q4_BLOCK } from './gguf.js';

export const ROOT = 'diskformer';
export const FORMAT = 'diskformer-gguf/1';

// ── Ingest: GGUF (over HTTP Range, or a local file) → OPFS, in the engine layout ──
export const storeKey = (file) => file.replace(/\.gguf$/i, '').toLowerCase().replace(/[^a-z0-9._-]+/g, '-');

export async function readHeader(url, fetchFn, signal) {
  let n = 16 << 20;
  for (;;) {
    const r = await fetchFn(url, { headers: { Range: `bytes=0-${n - 1}` }, signal, cache: 'no-store' });
    if (!r.ok) throw new Error(`GGUF header fetch: HTTP ${r.status}`);
    const h = (name) => (r.headers && r.headers.get ? r.headers.get(name) : null);
    const total = /\/(\d+)\s*$/.exec(h('content-range') || '');
    const file = { size: total ? Number(total[1]) : null, etag: h('etag') };   // for the resume identity
    const u8 = new Uint8Array(await r.arrayBuffer());
    try { return { gguf: parseGguf(u8), bytes: u8, file }; } catch (e) { if (!e.needBytes) throw e; n = e.needBytes; }
  }
}

// A local file as the source: a fetch-shaped function that answers ingestGguf's Range requests from a Blob (a GGUF
// the user picked, e.g. from a Hugging Face or LM Studio cache), so nothing is downloaded. Pass it as `fetch`.
// No ETag: an interrupted ingest resumes from the same file (same header and size), never from a download's state.
export function fileFetch(blob) {
  return async (_url, { headers = {}, signal } = {}) => {
    if (signal) signal.throwIfAborted();
    const m = /^bytes=(\d+)-(\d+)$/.exec(headers.Range || '');
    if (!m) throw new Error('fileFetch: only Range requests (bytes=a-b) are supported');
    const start = Number(m[1]), end = Math.min(Number(m[2]), blob.size - 1);
    if (start > end) return new Response(null, { status: 416, headers: { 'content-range': `bytes */${blob.size}` } });
    return new Response(blob.slice(start, end + 1), { status: 206, headers: { 'content-range': `bytes ${start}-${end}/${blob.size}` } });
  };
}

// FNV-1a, for the resume identity: over bytes (the GGUF header) or a string (the plan's output layout).
const fnv = (at, n) => { let h = 0x811c9dc5; for (let i = 0; i < n; i++) h = Math.imul(h ^ at(i), 0x01000193) >>> 0; return `${n}:${h.toString(16)}`; };
const bytesId = (u8) => fnv((i) => u8[i], u8.length);
const textId = (s) => fnv((i) => s.charCodeAt(i), s.length);

// plan.layout(gguf) → { experts: { file, bytes, … }, dense: { file, bytes, tensors } }: where every kept byte goes.
// plan.units(gguf, layout) → sorted units { src, len, file: 'dense' | 'experts', raw } or { …, kind?: 'q4', q, s }:
// byte ranges of the GGUF, each small enough to transform in memory (raw copies, or Q8_0 / Q4_0 blocks split
// into a value plane at q and an f16-scale plane at s).
// An interrupted ingest resumes only when the GGUF header, the plan's output layout, and the source's size and ETag
// (when the server sends them) match its checkpoint; otherwise it starts over. `rangeBytes` and `io` are for tests:
// smaller range requests, and fake OPFS files.
export async function ingestGguf({ url, key, plan, root = ROOT, format = FORMAT, fetch: fetchFn = fetch, onProgress = () => {}, signal, source = {},
  rangeBytes = 1 << 30, io = { OpfsWriter, readOpfsText, writeOpfsText } }) {
  if (!plan || !plan.layout || !plan.units) throw new Error('ingestGguf: plan { layout, units } is required');
  const t0 = performance.now();
  const { gguf, bytes: headerBuf, file } = await readHeader(url, fetchFn, signal);
  const layout = plan.layout(gguf);
  const dir = `${root}/${key}`;
  const storage = typeof navigator !== 'undefined' && navigator.storage;
  const est = storage && storage.estimate ? await storage.estimate() : {};
  const persisted = storage && storage.persist ? await storage.persist().catch(() => false) : false;
  const needed = layout.experts.bytes + layout.dense.bytes;
  onProgress({ status: 'ingest-plan', needed, quota: est.quota, usage: est.usage, persisted });
  const quotaLog = [{ written: 0, quota: est.quota, usage: est.usage }];
  const units = plan.units(gguf, layout);
  const identity = [bytesId(headerBuf.subarray(0, gguf.dataStart)), textId(JSON.stringify([layout, units])), file.size ?? '', file.etag ?? ''].join('|');
  let prior = null;
  try { prior = JSON.parse(await io.readOpfsText(`${dir}/manifest.json`) || 'null'); } catch (_) { prior = null; }
  const r0 = prior && !prior.complete && prior.format === format && prior.resume;
  const startUnit = r0 && r0.identity === identity && r0.unit > 0 && r0.unit < units.length ? r0.unit : 0;
  const checkpoint = (unit) => io.writeOpfsText(`${dir}/manifest.json`, JSON.stringify({ format, complete: false, resume: { identity, unit } }));

  // Stream the data section in order. Units are filled from the response chunks, transformed,
  // and written while the next bytes arrive (at most `maxWrites` writes in flight).
  const first = units[0].src, last = units[units.length - 1].src + units[units.length - 1].len;
  const resumedFrom = units[startUnit].src - first;
  const maxUnit = units.reduce((m, u) => Math.max(m, u.len), 0);
  let ui = startUnit, fill = 0, unitBuf = new Uint8Array(maxUnit);
  const writers = {};
  const release = async (name) => { const w = writers[name]; delete writers[name]; await w.close(); };
  const inflight = new Set(); const maxWrites = 8;
  const spare = [];
  const getBuf = (n) => { const i = spare.findIndex((b) => b.byteLength >= n); return i >= 0 ? spare.splice(i, 1)[0] : new ArrayBuffer(n); };
  const queue = async (w, buf, len, at) => {
    while (inflight.size >= maxWrites) await Promise.race(inflight);
    const p = w.writeOwned(buf, len, at).then((b) => { inflight.delete(p); if (spare.length < 16) spare.push(b); });
    p.catch(() => {});       // a failed write surfaces through the race above or the final Promise.all
    inflight.add(p);
  };
  let done = resumedFrom, written = 0;
  const flushUnit = async (u) => {
    const src = unitBuf.subarray(0, u.len);
    const w = writers[u.file];
    if (u.raw !== undefined) {
      const b = getBuf(u.len); new Uint8Array(b, 0, u.len).set(src);
      await queue(w, b, u.len, u.raw); written += u.len; return;
    }
    const q4 = u.kind === 'q4', blk = q4 ? Q4_BLOCK : Q8_BLOCK, qPer = q4 ? 16 : 32;
    const nb = u.len / blk;
    const qb = getBuf(nb * qPer), sb = getBuf(nb * 2);
    (q4 ? splitQ4 : splitQ8)(src, new Uint8Array(qb, 0, nb * qPer), new Uint8Array(sb, 0, nb * 2));
    await queue(w, qb, nb * qPer, u.q);
    await queue(w, sb, nb * 2, u.s);
    written += nb * blk;
  };
  try {
    if (!startUnit) {
      await checkpoint(0);
      // Header bytes, for the tokenizer and metadata at every later load.
      writers.header = await io.OpfsWriter.open(`${dir}/header.bin`, { truncate: true });
      await writers.header.write(headerBuf.subarray(0, gguf.dataStart), 0);
      await release('header');
    } else {
      onProgress({ status: 'ingest-resume', unit: startUnit, units: units.length, loaded: resumedFrom, total: last - first });
    }
    // No up-front truncate to full size: a fresh origin's quota is ~10 GiB and grows with what is
    // actually written (measured 2026-10-02), so a single 30.8 GB extension would be refused. The
    // writes below grow each file by at most one layer's records (~642 MB) at a time.
    writers.dense = await io.OpfsWriter.open(`${dir}/dense.bin`, { truncate: !startUnit });
    writers.experts = await io.OpfsWriter.open(`${dir}/experts.bin`, { truncate: !startUnit });
    // Sequential range requests of rangeBytes (1 GiB) keep any one response bounded.
    let pos = units[startUnit].src;
    for (let start = pos; start < last; start += rangeBytes) {
      const end = Math.min(last, start + rangeBytes) - 1;
      const r = await fetchFn(url, { headers: { Range: `bytes=${start}-${end}` }, signal, cache: 'no-store' });
      if (r.status !== 206) throw new Error(`GGUF range ${start}-${end}: HTTP ${r.status}`);
      const reader = r.body.getReader();
      for (;;) {
        const { done: eof, value } = await reader.read();
        if (eof) break;
        let off = 0;
        while (off < value.byteLength && ui < units.length) {
          const u = units[ui];
          if (pos < u.src) { const skip = Math.min(u.src - pos, value.byteLength - off); pos += skip; off += skip; continue; }
          const take = Math.min(u.len - fill, value.byteLength - off);
          unitBuf.set(value.subarray(off, off + take), fill);
          fill += take; off += take; pos += take;
          if (fill === u.len) { await flushUnit(u); ui++; fill = 0; }
        }
        done = pos - first;
        onProgress({ status: 'ingest', loaded: done, total: last - first, resumedFrom, written, secs: (performance.now() - t0) / 1000 });
        if (written - quotaLog[quotaLog.length - 1].written > 4 * 2 ** 30 && storage && storage.estimate) {
          const e = await storage.estimate();
          quotaLog.push({ written, quota: e.quota, usage: e.usage });
        }
      }
      // Every unit before ui is written: flush, then record ui as the resume point.
      if (ui < units.length) {
        await Promise.all(inflight);
        await writers.dense.flush(); await writers.experts.flush();
        await checkpoint(ui);
      }
    }
    if (ui !== units.length) throw new Error(`ingest ended early: ${ui} of ${units.length} units`);
    await Promise.all(inflight);
    await release('dense');
    await release('experts');
  } catch (e) {
    // Release every file still open, so a retry in this page can reopen them and resume.
    await Promise.allSettled([...inflight]);
    await Promise.allSettled(Object.keys(writers).map(release));
    throw e;
  }
  const manifest = {
    format, complete: true, ingestedAt: new Date().toISOString(),
    source: { url, ...source, dataStart: gguf.dataStart, headerBytes: gguf.headerBytes },
    ingestSecs: (performance.now() - t0) / 1000, resumedAtUnit: startUnit || undefined, quotaBefore: est.quota, persisted, quotaLog,
    ...layout,
  };
  await io.writeOpfsText(`${dir}/manifest.json`, JSON.stringify(manifest));
  return manifest;
}

// Ingest progress as hosts read it: a 'weights' event with byte counts. The spread goes first, so the
// event's own status ('ingest') cannot overwrite 'weights' (LocalMind's 2026-10-04 bug: a host's load
// watchdog, seeing no progress, killed a 37 GB first download).
export function ingestProgress(e) {
  return e && e.status === 'ingest' ? { ...e, status: 'weights', loaded: e.loaded, total: e.total } : e;
}

export async function removeStore(key, { root = ROOT } = {}) { await removeOpfs(`${root}/${key}`); }