import { mkdir, readFile, writeFile } from "node:fs/promises";
import { createHash } from "node:crypto";
import { unzipSync } from "fflate";
export const assetsRoot = ".cache/minecraft/1.21.11";
const completionMarker = `${assetsRoot}/.minegeo-assets.json`;
const requiredAssets = [
  "blockstates/grass_block.json",
  "blockstates/stone.json",
  "models/block/block.json",
  "models/block/cube.json",
  "models/block/cube_all.json",
  "textures/block/grass_block_top.png",
  "textures/block/dirt.png",
  "textures/block/stone.png",
  "textures/block/water_still.png",
];
async function assetsReady() {
  try {
    const marker = JSON.parse(await readFile(completionMarker, "utf8"));
    if (
      marker.format !== "minegeo-assets/v2" ||
      marker.minecraftVersion !== "1.21.11" ||
      !marker.files
    )
      return false;
    // A blockstate alone is insufficient: interrupted setup can leave models
    // and textures absent. The marker is only written after all extraction.
    for (const asset of requiredAssets) {
      const bytes = await readFile(`${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() {
  if (await assetsReady()) return;
  console.log(
    "Preparing Minecraft 1.21.11 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 === "1.21.11");
  if (!entry) throw new Error("Official Minecraft 1.21.11 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-1.21.11.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 ${response.status}`,
      );
    jar = Buffer.from(await response.arrayBuffer());
    if (
      createHash("sha1").update(jar).digest("hex") !==
      version.downloads.client.sha1
    )
      throw new Error(
        "Minecraft client checksum mismatch; downloaded assets were not saved",
      );
    await writeFile(jarPath, jar);
  }
  const entries = unzipSync(jar, {
    filter: (f) =>
      /^assets\/minecraft\/(models|blockstates|textures\/block)\//.test(
        f.name,
      ) && /\.(json|png|mcmeta)$/.test(f.name),
  });
  for (const [name, bytes] of Object.entries(entries)) {
    const path = `${assetsRoot}/${name}`;
    await mkdir(path.slice(0, path.lastIndexOf("/")), { recursive: true });
    await writeFile(path, bytes);
  }
  // Completion is recorded last, so a killed extraction is repaired next time.
  await writeFile(
    completionMarker,
    JSON.stringify({
      format: "minegeo-assets/v2",
      minecraftVersion: "1.21.11",
      clientSha1: version.downloads.client.sha1,
      files: Object.keys(entries).length,
    }),
  );
  if (!(await assetsReady()))
    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.`,
  );
}