/**
 * Bereitet Bilder und Videos fuer das Medienverzeichnis auf, bevor sie
 * hochgeladen werden (docs/MEDIEN.md):
 *
 *   pnpm media:optimize <eingabe-ordner> [ausgabe-ordner]
 *
 * - Videos (.mp4, .mov, .m4v, .webm) → "<name>.web.mp4": laengste Seite
 *   hoechstens 1920 px, H.264, Index am Dateianfang (faststart), damit der
 *   Browser sofort abspielen kann statt erst die ganze Datei zu laden.
 *   Headervideos ohne Ton. Fehlt ein Vorschaubild, wird eins erzeugt.
 *   Die Seite nimmt automatisch die .web.mp4, wenn sie daneben liegt.
 * - Bilder groesser als noetig werden verkleinert (Logo 1600 px, sonst
 *   2560 px laengste Seite), kleinere unveraendert kopiert.
 *
 * Ausgabe standardmaessig in "<eingabe-ordner>-web" mit gleicher
 * Ordnerstruktur; diesen Inhalt ins Medienverzeichnis kopieren. Bereits
 * aufbereitete Dateien (neuer als das Original) werden uebersprungen.
 */
import { spawn } from "node:child_process";
import { copyFile, mkdir, readdir, stat } from "node:fs/promises";
import path from "node:path";
import ffmpegPath from "ffmpeg-static";
import sharp from "sharp";

const VIDEO_EXTS = new Set([".mp4", ".mov", ".m4v", ".webm"]);
const IMAGE_EXTS = new Set([".jpg", ".jpeg", ".png", ".webp"]);
const MAX_VIDEO_EDGE = 1920;
const MAX_IMAGE_EDGE = 2560;
const MAX_LOGO_EDGE = 1600;
const POSTER_SECOND = 1;

async function* walk(dir: string): AsyncGenerator<string> {
  for (const entry of await readdir(dir, { withFileTypes: true })) {
    const full = path.join(dir, entry.name);
    if (entry.isDirectory()) yield* walk(full);
    else if (entry.isFile()) yield full;
  }
}

async function isFresh(output: string, input: string): Promise<boolean> {
  try {
    return (await stat(output)).mtimeMs >= (await stat(input)).mtimeMs;
  } catch {
    return false;
  }
}

async function exists(file: string): Promise<boolean> {
  return stat(file).then(
    () => true,
    () => false,
  );
}

function ffmpeg(args: string[]): Promise<void> {
  const binary = ffmpegPath as unknown as string | null;
  if (!binary) throw new Error("ffmpeg-static liefert fuer dieses System kein ffmpeg.");
  return new Promise((resolve, reject) => {
    const child = spawn(binary, ["-hide_banner", "-loglevel", "error", "-stats", "-y", ...args], { stdio: ["ignore", "inherit", "inherit"] });
    child.on("error", reject);
    child.on("exit", (code) => (code === 0 ? resolve() : reject(new Error(`ffmpeg endete mit Code ${code}`))));
  });
}

/** Laengste Seite auf MAX_VIDEO_EDGE begrenzen, nie vergroessern, gerade Masse fuer H.264. */
const SCALE_FILTER = `scale='if(gte(iw,ih),min(${MAX_VIDEO_EDGE},iw),-2)':'if(gte(iw,ih),-2,min(${MAX_VIDEO_EDGE},ih))'`;

async function hasPoster(input: string, base: string): Promise<boolean> {
  const dir = path.dirname(input);
  const name = path.basename(base);
  for (const ext of IMAGE_EXTS) {
    if (await exists(path.join(dir, `${name}${ext}`))) return true;
  }
  return false;
}

async function optimizeVideo(input: string, outDir: string, base: string): Promise<string[]> {
  const output = path.join(outDir, `${base}.web.mp4`);
  const written: string[] = [];
  if (!(await isFresh(output, input))) {
    const silent = base.toLowerCase() === "header";
    await ffmpeg([
      "-i", input,
      "-vf", SCALE_FILTER,
      "-c:v", "libx264", "-preset", "slow", "-crf", "23", "-profile:v", "high", "-pix_fmt", "yuv420p",
      "-maxrate", "6M", "-bufsize", "12M",
      ...(silent ? ["-an"] : ["-c:a", "aac", "-b:a", "128k"]),
      "-movflags", "+faststart",
      output,
    ]);
    written.push(output);
  }
  const poster = path.join(outDir, `${base}.jpg`);
  if (!(await hasPoster(input, base)) && !(await isFresh(poster, input))) {
    await ffmpeg(["-ss", String(POSTER_SECOND), "-i", input, "-frames:v", "1", "-vf", SCALE_FILTER, "-q:v", "3", poster]);
    written.push(poster);
  }
  return written;
}

async function optimizeImage(input: string, output: string): Promise<string[]> {
  if (await isFresh(output, input)) return [];
  const isLogo = path.basename(input).toLowerCase().startsWith("logo");
  const limit = isLogo ? MAX_LOGO_EDGE : MAX_IMAGE_EDGE;
  const meta = await sharp(input).metadata();
  if (Math.max(meta.width ?? 0, meta.height ?? 0) <= limit) {
    await copyFile(input, output);
    return [output];
  }
  const resized = sharp(input).rotate().resize(limit, limit, { fit: "inside", withoutEnlargement: true });
  const ext = path.extname(input).toLowerCase();
  if (ext === ".png") await resized.png({ compressionLevel: 9 }).toFile(output);
  else if (ext === ".webp") await resized.webp({ quality: 82 }).toFile(output);
  else await resized.jpeg({ quality: 82, mozjpeg: true }).toFile(output);
  return [output];
}

function megabytes(bytes: number): string {
  return `${(bytes / 1_048_576).toFixed(1)} MB`;
}

async function main(): Promise<void> {
  const [inputArg, outputArg] = process.argv.slice(2);
  if (!inputArg) {
    console.error("Aufruf: pnpm media:optimize <eingabe-ordner> [ausgabe-ordner]");
    process.exitCode = 2;
    return;
  }
  const inputDir = path.resolve(inputArg);
  const outputDir = path.resolve(outputArg ?? `${inputDir}-web`);
  if (outputDir === inputDir) throw new Error("Ausgabe-Ordner muss sich vom Eingabe-Ordner unterscheiden.");

  let before = 0;
  let after = 0;
  for await (const input of walk(inputDir)) {
    const rel = path.relative(inputDir, input);
    const ext = path.extname(rel).toLowerCase();
    if (!VIDEO_EXTS.has(ext) && !IMAGE_EXTS.has(ext)) continue;
    if (rel.toLowerCase().endsWith(".web.mp4")) continue;
    const outDir = path.join(outputDir, path.dirname(rel));
    await mkdir(outDir, { recursive: true });
    console.log(`→ ${rel}`);
    const written = VIDEO_EXTS.has(ext)
      ? await optimizeVideo(input, outDir, path.basename(rel, path.extname(rel)))
      : await optimizeImage(input, path.join(outDir, path.basename(rel)));
    if (written.length === 0) {
      console.log("  bereits aktuell");
      continue;
    }
    const inSize = (await stat(input)).size;
    const outSize = (await Promise.all(written.map((f) => stat(f)))).reduce((sum, s) => sum + s.size, 0);
    before += inSize;
    after += outSize;
    console.log(`  ${megabytes(inSize)} → ${megabytes(outSize)}: ${written.map((f) => path.relative(outputDir, f)).join(", ")}`);
  }
  console.log(`Fertig: ${megabytes(before)} → ${megabytes(after)}. Inhalt von ${outputDir} ins Medienverzeichnis kopieren.`);
}

main().catch((error: unknown) => {
  console.error(`Abbruch: ${error instanceof Error ? error.message : String(error)}`);
  process.exitCode = 1;
});