"""Memory capsule: zero-backend shareable export (spec M17, lane G).

Contract: :func:`build_capsule` writes a self-contained bundle to ``out_dir`` (default
``config.CAPSULE_DIR``):

- copy ``frontend/dist`` (error clearly if missing — tell the user to ``npm run build``);
- copy media from ``config.RAW_DIR``;
- bake every read-only API response to files at the *same relative paths*
  (``api/manifest``, ``api/events``, ``api/anchors``, ``api/beats``,
  ``api/videos/{id}/poses``, ``api/pointcloud``, ``api/splat``, ``api/audio/{id}`` —
  extracting audio via ``ingest.extract_audio_hq`` if not yet cached);
- inject ``<script>window.__F4D_API_BASE__=""</script>`` into the copied ``index.html``;
- set ``"capsule": true`` in the baked manifest (the frontend hides all write UI);
- ship a stdlib ``serve.py`` in the bundle root that serves with HTTP Range support
  (video seeking needs 206s; plain ``http.server`` can't — pitfall #4).

Skip what doesn't exist (no splat -> no ``api/splat``) — degrade, don't block.
Returns a summary dict (bundle path, file count, bytes) for the CLI log.

Layout mirror (why paths look the way they do): the frontend resolves every URL as
``API_BASE + path`` with API_BASE == "" in a capsule, so requests hit the bundle root:
``fetch("/api/manifest")`` (no extension — bake the file extension-less; serve.py maps
extension-less ``api/*`` files to a JSON content type), ``video.src = "/media/<filename>"``
(manifest ``url`` fields are ``/media/{filename}`` — media files are copied under
``media/``), PLY loader hits ``/api/pointcloud``, the WebAudio clock fetches
``/api/audio/{id}``. Saved camera paths (M16) are read-only in a capsule, so
``api/paths`` + ``api/paths/{id}`` are baked too — the load dropdown keeps working.
"""

from __future__ import annotations

import json
import logging
import shutil
from pathlib import Path

from festival4d import config, db

log = logging.getLogger("festival4d.capsule")

# Injected verbatim (phase-5 contract #5): a runtime override that beats the build-time
# VITE_API_BASE, turning the same dist bundle zero-backend. Must land in index.html before
# the app module reads it (modules are deferred, but we inject ahead of the first <script>
# anyway so execution order is obvious).
_API_BASE_SNIPPET = '<script>window.__F4D_API_BASE__=""</script>'


# ---------------------------------------------------------------------------
# serve.py shipped in the bundle root (stdlib-only, Range-capable — pitfall #4)
# ---------------------------------------------------------------------------
SERVE_PY = r'''#!/usr/bin/env python3
"""Serve this Festival 4D memory capsule locally.

Plain `python -m http.server` cannot answer HTTP Range requests, and <video>
seeking needs 206 partial responses — so the capsule ships this tiny stdlib
server instead. No dependencies beyond Python 3.8+.

    python serve.py [--port 8080] [--host 127.0.0.1]

Then open http://127.0.0.1:8080/ in a browser.
"""
import argparse
import os
import re
from functools import partial
from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer

ROOT = os.path.dirname(os.path.abspath(__file__))

_RANGE = re.compile(r"bytes=(\d*)-(\d*)$")


class _Slice:
    """File wrapper that reads at most `length` bytes (the body of a 206)."""

    def __init__(self, f, length):
        self._f = f
        self._left = length

    def read(self, n=-1):
        if self._left <= 0:
            return b""
        if n < 0 or n > self._left:
            n = self._left
        data = self._f.read(n)
        self._left -= len(data)
        return data

    def close(self):
        self._f.close()


class RangeHandler(SimpleHTTPRequestHandler):
    protocol_version = "HTTP/1.1"

    def guess_type(self, path):
        # Baked API responses are extension-less files at the live API's relative
        # paths; give them the content types the live server would have used.
        url = self.path.split("?", 1)[0].split("#", 1)[0].lstrip("/")
        if "." not in url.rsplit("/", 1)[-1]:
            if url.startswith("api/audio/"):
                return "audio/mp4"
            if url in ("api/pointcloud", "api/splat"):
                return "application/octet-stream"
            if url.startswith("api/"):
                return "application/json"
        return super().guess_type(path)

    def send_head(self):
        path = self.translate_path(self.path)
        if os.path.isdir(path):
            # Directory -> index.html (the SPA entry), stock behavior.
            return super().send_head()
        try:
            f = open(path, "rb")
        except OSError:
            self.send_error(404, "File not found")
            return None
        try:
            size = os.fstat(f.fileno()).st_size
            start, end, status = 0, size - 1, 200
            m = _RANGE.match(self.headers.get("Range", "").strip())
            if m and (m.group(1) or m.group(2)):
                if m.group(1):
                    start = int(m.group(1))
                    if m.group(2):
                        end = min(int(m.group(2)), size - 1)
                else:  # suffix form: bytes=-N (the final N bytes)
                    start = max(size - int(m.group(2)), 0)
                if start >= size:
                    self.send_response(416)
                    self.send_header("Content-Range", "bytes */%d" % size)
                    self.send_header("Content-Length", "0")
                    self.end_headers()
                    f.close()
                    return None
                status = 206
            self.send_response(status)
            self.send_header("Content-Type", self.guess_type(path))
            self.send_header("Accept-Ranges", "bytes")
            self.send_header("Content-Length", str(end - start + 1))
            if status == 206:
                self.send_header("Content-Range", "bytes %d-%d/%d" % (start, end, size))
            self.end_headers()
            f.seek(start)
            return _Slice(f, end - start + 1)
        except Exception:
            f.close()
            raise


def main():
    ap = argparse.ArgumentParser(description="Serve this Festival 4D capsule (Range-capable).")
    ap.add_argument("--host", default="127.0.0.1")
    ap.add_argument("--port", type=int, default=8080)
    args = ap.parse_args()
    handler = partial(RangeHandler, directory=ROOT)
    httpd = ThreadingHTTPServer((args.host, args.port), handler)
    print("Festival 4D capsule -> http://%s:%d/" % (args.host, args.port))
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        pass


if __name__ == "__main__":
    main()
'''


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------
def _bake_json(path: Path, obj) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(json.dumps(obj, indent=2))


def _inject_api_base(index_html: Path) -> None:
    """Insert the runtime API-base override into the copied index.html."""
    html = index_html.read_text()
    if "__F4D_API_BASE__" in html:
        return  # already injected (rebuild over an old bundle copy)
    i = html.find("<script")
    if i == -1:
        i = html.find("</head>")
    if i != -1:
        html = html[:i] + _API_BASE_SNIPPET + "\n    " + html[i:]
    else:  # no <script> and no </head> — degenerate page; prepend
        html = _API_BASE_SNIPPET + "\n" + html
    index_html.write_text(html)


def _prepare_out_dir(out: Path) -> None:
    """Refuse to clobber a directory that isn't (or wasn't) a capsule."""
    if not out.exists():
        return
    contents = list(out.iterdir())
    is_previous_capsule = (out / "serve.py").exists() or (out / "index.html").exists()
    if contents and not is_previous_capsule:
        raise RuntimeError(
            f"output dir {out} exists and does not look like a previous capsule — "
            "refusing to overwrite; pass an empty/new --out"
        )
    shutil.rmtree(out)


def _summary(out: Path) -> dict:
    files = [p for p in out.rglob("*") if p.is_file()]
    return {
        "bundle": str(out),
        "files": len(files),
        "bytes": sum(p.stat().st_size for p in files),
    }


# ---------------------------------------------------------------------------
# Entry point
# ---------------------------------------------------------------------------
def build_capsule(out_dir: str | Path | None = None,
                  dist_dir: str | Path | None = None) -> dict:
    """Build the static shareable bundle (see module doc).

    ``dist_dir`` overrides the frontend build location (default
    ``<repo>/frontend/dist``) — used by tests to point at a fabricated dist.
    """
    # The API module is the single source of truth for response shapes — its route
    # functions are plain callables returning the exact dicts the live server sends,
    # so baking through them can never drift from the frozen contract.
    from festival4d import api, ingest

    dist = Path(dist_dir) if dist_dir is not None else config.REPO_ROOT / "frontend" / "dist"
    if not (dist / "index.html").exists():
        raise RuntimeError(
            f"frontend build not found at {dist} — run `cd frontend && npm run build` first"
        )

    out = Path(out_dir) if out_dir is not None else config.CAPSULE_DIR
    _prepare_out_dir(out)

    db.init_engine()
    db.init_db()
    videos = db.get_videos()

    # 1. Frontend bundle + runtime API-base override.
    shutil.copytree(dist, out)
    _inject_api_base(out / "index.html")

    # 2. Media (only the files the manifest references — RAW_DIR may hold strays).
    media_dir = out / "media"
    media_dir.mkdir(parents=True, exist_ok=True)
    for v in videos:
        src = config.RAW_DIR / v.filename
        if src.exists():
            shutil.copy2(src, media_dir / v.filename)
        else:
            log.warning("capsule: source video missing, skipped: %s", src)

    # 3. Baked read-only API responses, at the SAME relative paths the live API serves
    #    (extension-less on purpose — the frontend fetches e.g. `${API_BASE}/api/manifest`).
    api_dir = out / "api"
    manifest = api.manifest()
    manifest["capsule"] = True       # frontend hides all write UI (contract #5)
    manifest["has_capture"] = False  # capture routes never exist in a static bundle
    _bake_json(api_dir / "manifest", manifest)
    _bake_json(api_dir / "events", api.get_events())
    _bake_json(api_dir / "anchors", api.get_anchors())
    for v in videos:
        _bake_json(api_dir / "videos" / str(v.id) / "poses", api.video_poses(v.id))

    # Saved camera paths (M16) — read-only in a capsule, so the load dropdown still works.
    # A filesystem can't hold both a FILE `api/paths` and per-id files under `api/paths/`,
    # so the listing is baked as the directory's index.html: GET /api/paths gets the stock
    # 301 -> /api/paths/ -> index.html (fetch follows redirects), and serve.py's URL-based
    # content-type override still labels it application/json.
    _bake_json(api_dir / "paths" / "index.html", api.get_paths())
    for p in db.get_paths():
        _bake_json(api_dir / "paths" / str(p.id), api.get_path(p.id))

    # Optional artifacts: bake when present, silently omit when not (the frontend already
    # handles the 404s serve.py will answer for the missing files — degrade, don't block).
    if config.BEATS_JSON.exists():
        _bake_json(api_dir / "beats", json.loads(config.BEATS_JSON.read_text()))
    if config.POINTS_PLY.exists():
        api_dir.mkdir(parents=True, exist_ok=True)
        shutil.copy2(config.POINTS_PLY, api_dir / "pointcloud")
    if config.SPLAT_PLY.exists():
        api_dir.mkdir(parents=True, exist_ok=True)
        shutil.copy2(config.SPLAT_PLY, api_dir / "splat")

    # 4. Soundtracks for the WebAudio master clock: reuse the live server's lazy cache,
    #    extracting on demand exactly like GET /api/audio/{id} would have.
    import subprocess

    for v in videos:
        src = config.RAW_DIR / v.filename
        cached = config.AUDIO_HQ_DIR / f"{v.id}.m4a"
        if src.exists() and (not cached.exists() or cached.stat().st_mtime < src.stat().st_mtime):
            try:
                ingest.extract_audio_hq(src, cached)
            except (subprocess.CalledProcessError, RuntimeError, OSError) as exc:
                log.warning("capsule: no extractable audio for video %s: %s", v.id, exc)
        if cached.exists():
            audio_out = api_dir / "audio" / str(v.id)
            audio_out.parent.mkdir(parents=True, exist_ok=True)
            shutil.copy2(cached, audio_out)

    # 5. The Range-capable server (pitfall #4).
    serve_py = out / "serve.py"
    serve_py.write_text(SERVE_PY)
    serve_py.chmod(serve_py.stat().st_mode | 0o111)

    summary = _summary(out)
    log.info("capsule: baked %(files)d files (%(bytes)d bytes) at %(bundle)s", summary)
    return summary