import { readFile } from "node:fs/promises";
import { inflateRawSync } from "node:zlib";
import { describe, expect, it } from "vitest";

/** Mirrors hub/src/capability/pbank.ts zip reader contracts. */
function listZipEntries(buffer: Buffer) {
  let eocd = -1;
  const minEocd = Math.max(0, buffer.length - (22 + 0xffff));
  for (let i = buffer.length - 22; i >= minEocd; i -= 1) {
    if (buffer.readUInt32LE(i) === 0x06054b50) {
      eocd = i;
      break;
    }
  }
  if (eocd < 0) throw new Error("missing eocd");
  const totalEntries = buffer.readUInt16LE(eocd + 10);
  const centralOffset = buffer.readUInt32LE(eocd + 16);
  const entries: Array<{ name: string; method: number; compressedSize: number; uncompressedSize: number; localHeaderOffset: number }> = [];
  let offset = centralOffset;
  for (let i = 0; i < totalEntries; i += 1) {
    const method = buffer.readUInt16LE(offset + 10);
    const compressedSize = buffer.readUInt32LE(offset + 20);
    const uncompressedSize = buffer.readUInt32LE(offset + 24);
    const nameLen = buffer.readUInt16LE(offset + 28);
    const extraLen = buffer.readUInt16LE(offset + 30);
    const commentLen = buffer.readUInt16LE(offset + 32);
    const localHeaderOffset = buffer.readUInt32LE(offset + 42);
    const nameStart = offset + 46;
    const name = buffer.subarray(nameStart, nameStart + nameLen).toString("utf8");
    entries.push({ name, method, compressedSize, uncompressedSize, localHeaderOffset });
    offset = nameStart + nameLen + extraLen + commentLen;
  }
  return entries;
}

function inflateZipEntry(buffer: Buffer, entry: { method: number; compressedSize: number; uncompressedSize: number; localHeaderOffset: number }) {
  const local = entry.localHeaderOffset;
  const nameLen = buffer.readUInt16LE(local + 26);
  const extraLen = buffer.readUInt16LE(local + 28);
  const dataStart = local + 30 + nameLen + extraLen;
  const compressed = buffer.subarray(dataStart, dataStart + entry.compressedSize);
  if (entry.method === 0) return Buffer.from(compressed);
  if (entry.method === 8) return Buffer.from(inflateRawSync(compressed));
  throw new Error(`method ${entry.method}`);
}

describe("pbank zip reader contract", () => {
  it("lists and inflates deflated entries without host unzip", async () => {
    const zip = await readFile(new URL("./fixtures/pbank-mini.zip", import.meta.url));
    const entries = listZipEntries(zip);
    expect(entries.map((e) => e.name).sort()).toEqual(["fig/a.png", "hello.txt"]);
    const hello = entries.find((e) => e.name === "hello.txt")!;
    const text = inflateZipEntry(zip, hello).toString("utf8");
    expect(text).toBe("hello pbank\n");
  });
});