import { NextRequest } from "next/server";
import fsp from "node:fs/promises";
import { findVideosForCode, getVideoIndex, rescanVideoIndex } from "@/lib/video";
import { getAppSetting } from "@/lib/db/appSettings";
import { probeDuration } from "@/lib/video/duration";
import { assertLocalRequest } from "@/lib/api/localOnly";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

/**
 * HLS playlist generator. Returns an m3u8 with N segment URLs covering
 * the full video duration. Segments are produced on demand by the
 * sibling /segment endpoint (each one is a fresh NVENC transcode of a
 * fixed time window). Player (hls.js) requests segments as needed for
 * playback and seeking.
 */
const SEGMENT_SECONDS = 6;

export async function GET(req: NextRequest, ctx: { params: Promise<{ code: string }> }) {
  const blocked = assertLocalRequest(req);
  if (blocked) return blocked;

  const { code } = await ctx.params;
  const decoded = decodeURIComponent(code);
  const url = new URL(req.url);
  const partRaw = url.searchParams.get("part");
  const part = partRaw == null ? 0 : Math.max(0, parseInt(partRaw, 10) || 0);

  let files = findVideosForCode(decoded);
  if (files.length === 0) {
    const main = (getAppSetting("videoLibraryPath") || "").trim();
    const extras = getAppSetting("videoExtraPaths") ?? [];
    const expected = [main, ...extras].filter(Boolean);
    const idx = getVideoIndex();
    const haveAll = expected.length === idx.rootsScanned.length
      && expected.every((r, i) => r === idx.rootsScanned[i]);
    if (expected.length > 0 && !haveAll) {
      await rescanVideoIndex();
      files = findVideosForCode(decoded);
    }
  }
  if (files.length === 0) return new Response("not found", { status: 404 });
  const file = files[Math.min(part, files.length - 1)];

  try {
    await fsp.stat(file.abs);
  } catch {
    return new Response("not found", { status: 404 });
  }

  const duration = await probeDuration(file.abs, req.signal);
  if (duration == null) {
    return new Response("ffprobe failed", { status: 500 });
  }

  const segCount = Math.ceil(duration / SEGMENT_SECONDS);
  const lines: string[] = [
    "#EXTM3U",
    "#EXT-X-VERSION:3",
    `#EXT-X-TARGETDURATION:${SEGMENT_SECONDS}`,
    "#EXT-X-MEDIA-SEQUENCE:0",
    "#EXT-X-PLAYLIST-TYPE:VOD",
  ];
  for (let i = 0; i < segCount; i++) {
    const remaining = duration - i * SEGMENT_SECONDS;
    const segDur = Math.min(SEGMENT_SECONDS, remaining);
    lines.push(`#EXTINF:${segDur.toFixed(3)},`);
    // Relative URL — resolves against the playlist URL's directory.
    // Playlist is at /api/video-hls/[code]/playlist, so its directory is
    // /api/video-hls/[code]/ and `segment?...` resolves to the sibling.
    lines.push(`segment?part=${part}&i=${i}`);
  }
  lines.push("#EXT-X-ENDLIST");

  return new Response(lines.join("\n"), {
    status: 200,
    headers: {
      "Content-Type": "application/vnd.apple.mpegurl",
      "Cache-Control": "no-store",
    },
  });
}