import { mkdir, readFile, stat, writeFile } from "node:fs/promises";
import { createHash } from "node:crypto";
import { unzipSync } from "fflate";
export const assetsRoot = ".cache/minecraft/1.21.11";
export function assetsDirectory(version = "1.21.11") {
  if (!/^(?:1\.21\.11|26\.[12](?:\.\d+)*)$/.test(version))
    throw new Error("Unsupported Minecraft asset version");
  return `.cache/minecraft/${version}`;
}
const requiredAssets = [
  "blockstates/grass_block.json",
  "blockstates/stone.json",
  "models/block/block.json",
  "models/block/cube.json",
  "models/block/cube_all.json",
  "textures/block/grass_block_top.png",
  "textures/block/dirt.png",
  "textures/block/stone.png",
  "textures/block/water_still.png",
];
async function assetsReady(minecraftVersion) {
  const assetsRoot = assetsDirectory(minecraftVersion);
  const completionMarker = `${assetsRoot}/.minegeo-assets.json`;
  try {
    const marker = JSON.parse(await readFile(completionMarker, "utf8"));
    if (
      marker.format !== "minegeo-assets/v3" ||
      marker.minecraftVersion !== minecraftVersion ||
      !marker.files ||
      !Array.isArray(marker.entries) ||
      marker.entries.length !== marker.files
    )
      return false;
    // Verify the complete extracted inventory, not just common blocks. A
    // partial cache otherwise silently drops newer or less common textures.
    let next = 0;
    await Promise.all(
      Array.from({ length: 16 }, async () => {
        while (next < marker.entries.length) {
          const entry = marker.entries[next++];
          if (
            !Array.isArray(entry) ||
            entry.length !== 2 ||
            typeof entry[0] !== "string" ||
            !/^assets\/minecraft\/(models|blockstates|textures)\/[a-z0-9_./-]+\.(json|png|mcmeta)$/.test(
              entry[0],
            ) ||
            entry[0].includes("..") ||
            !Number.isSafeInteger(entry[1]) ||
            entry[1] < 1
          )
            throw new Error("Invalid asset inventory");
          const info = await stat(`${assetsRoot}/${entry[0]}`);
          if (!info.isFile() || info.size !== entry[1])
            throw new Error("Missing asset");
        }
      }),
    );
    for (const asset of requiredAssets) {
      const bytes = await readFile(`${assetsRoot}/assets/minecraft/${asset}`);
      if (asset.endsWith(".json")) JSON.parse(bytes.toString());
      else if (
        bytes.length < 8 ||
        bytes.subarray(0, 8).toString("hex") !== "89504e470d0a1a0a"
      )
        return false;
    }
    return true;
  } catch {
    return false;
  }
}
export async function prepareAssets(minecraftVersion = "1.21.11") {
  const assetsRoot = assetsDirectory(minecraftVersion);
  const completionMarker = `${assetsRoot}/.minegeo-assets.json`;
  if (await assetsReady(minecraftVersion)) return assetsRoot;
  console.log(
    `Preparing Minecraft ${minecraftVersion} models and textures for terrain rendering…`,
  );
  const manifest = await (
    await fetch(
      "https://piston-meta.mojang.com/mc/game/version_manifest_v2.json",
      { signal: AbortSignal.timeout(60000) },
    )
  ).json();
  const entry = manifest.versions.find((v) => v.id === minecraftVersion);
  if (!entry)
    throw new Error(`Official Minecraft ${minecraftVersion} metadata missing`);
  const version = await (
    await fetch(entry.url, { signal: AbortSignal.timeout(60000) })
  ).json();
  await mkdir(".cache/minecraft", { recursive: true });
  const jarPath = `.cache/minecraft/client-${minecraftVersion}.jar`;
  let jar;
  try {
    jar = await readFile(jarPath);
  } catch {
    /* No cached client yet. */
  }
  if (
    !jar ||
    createHash("sha1").update(jar).digest("hex") !==
      version.downloads.client.sha1
  ) {
    const response = await fetch(version.downloads.client.url, {
      signal: AbortSignal.timeout(120000),
    });
    if (!response.ok)
      throw new Error(
        `Minecraft asset download failed: HTTP ${response.status}`,
      );
    jar = Buffer.from(await response.arrayBuffer());
    if (
      createHash("sha1").update(jar).digest("hex") !==
      version.downloads.client.sha1
    )
      throw new Error(
        "Minecraft client checksum mismatch; downloaded assets were not saved",
      );
    await writeFile(jarPath, jar);
  }
  const entries = unzipSync(jar, {
    filter: (f) =>
      /^assets\/minecraft\/(models|blockstates|textures)\//.test(f.name) &&
      /\.(json|png|mcmeta)$/.test(f.name),
  });
  const files = Object.entries(entries);
  const directories = new Set(
    files.map(
      ([name]) => `${assetsRoot}/${name.slice(0, name.lastIndexOf("/"))}`,
    ),
  );
  await Promise.all(
    [...directories].map((path) => mkdir(path, { recursive: true })),
  );
  let nextFile = 0;
  const writes = await Promise.allSettled(
    Array.from({ length: Math.min(16, files.length) }, async () => {
      while (nextFile < files.length) {
        const [name, bytes] = files[nextFile++];
        await writeFile(`${assetsRoot}/${name}`, bytes);
      }
    }),
  );
  const failedWrite = writes.find((result) => result.status === "rejected");
  if (failedWrite?.status === "rejected") throw failedWrite.reason;
  // Completion is recorded last, so a killed extraction is repaired next time.
  await writeFile(
    completionMarker,
    JSON.stringify({
      format: "minegeo-assets/v3",
      minecraftVersion,
      clientSha1: version.downloads.client.sha1,
      files: Object.keys(entries).length,
      entries: Object.entries(entries).map(([name, bytes]) => [
        name,
        bytes.length,
      ]),
    }),
  );
  if (!(await assetsReady(minecraftVersion)))
    throw new Error(
      "Minecraft rendering assets are incomplete or corrupt. Run npm run setup to repair them.",
    );
  console.log(
    `Prepared ${Object.keys(entries).length} verified vanilla model/texture assets.`,
  );
  return assetsRoot;
}