import { createHash } from "node:crypto";
import { mkdtemp, readdir, readFile, rm } from "node:fs/promises";
import { tmpdir } from "node:os";
import path from "node:path";
import { gzipSync } from "node:zlib";
import { createMigrationModule } from "./migration-module-fixture.js";

/**
 * Test-only builders for Ekklesia Module Package v1 archives (ADR 0049). They write ustar archives
 * by hand so a test can produce exactly what the canonical packager never would: links, device
 * nodes, traversal, a second top-level directory, a corrupted payload.
 */

export type FixtureEntryType = "file" | "directory" | "symlink" | "hardlink" | "character" | "fifo";

export interface FixtureEntry {
  readonly path: string;
  readonly type?: FixtureEntryType;
  readonly mode?: number;
  readonly data?: Uint8Array | string;
  readonly linkname?: string;
}

const typeflags: Readonly<Record<FixtureEntryType, string>> = {
  character: "3",
  directory: "5",
  fifo: "6",
  file: "0",
  hardlink: "1",
  symlink: "2",
};

function octal(value: number, width: number): string {
  return `${value.toString(8).padStart(width - 1, "0")}\u0000`;
}

function header(entry: FixtureEntry, size: number): Buffer {
  const block = Buffer.alloc(512);
  const name =
    entry.type === "directory" && !entry.path.endsWith("/") ? `${entry.path}/` : entry.path;
  let prefix = "";
  let base = name;
  if (Buffer.byteLength(name) > 100) {
    const split = name.lastIndexOf("/", name.length - 2);
    prefix = name.slice(0, split);
    base = name.slice(split + 1);
  }
  block.write(base, 0, 100, "latin1");
  block.write(octal(entry.mode ?? (entry.type === "directory" ? 0o755 : 0o644), 8), 100, "latin1");
  block.write(octal(0, 8), 108, "latin1");
  block.write(octal(0, 8), 116, "latin1");
  block.write(octal(size, 12), 124, "latin1");
  block.write(octal(0, 12), 136, "latin1");
  block.write("        ", 148, "latin1");
  block.write(typeflags[entry.type ?? "file"], 156, "latin1");
  block.write(entry.linkname ?? "", 157, 100, "latin1");
  block.write("ustar\u000000", 257, "latin1");
  block.write(prefix, 345, 155, "latin1");
  let checksum = 0;
  for (const byte of block) {
    checksum += byte;
  }
  block.write(`${checksum.toString(8).padStart(6, "0")}\u0000 `, 148, "latin1");
  return block;
}

/** A gzip-compressed ustar archive of exactly these entries, in this order. */
export function tarGz(entries: readonly FixtureEntry[]): Buffer {
  const parts: Buffer[] = [];
  for (const entry of entries) {
    const data =
      entry.type === undefined || entry.type === "file"
        ? Buffer.from(entry.data ?? "")
        : Buffer.alloc(0);
    parts.push(header(entry, data.length), data, Buffer.alloc((512 - (data.length % 512)) % 512));
  }
  parts.push(Buffer.alloc(1024));
  return gzipSync(Buffer.concat(parts), { level: 9 });
}

export function sha256(data: Uint8Array | string): string {
  return createHash("sha256").update(data).digest("hex");
}

export interface PackageFixtureOptions {
  readonly id?: string;
  readonly version?: string;
  readonly serverSource?: string;
  readonly schemaSource?: string;
  readonly manifest?: (manifest: Record<string, unknown>) => Record<string, unknown>;
  readonly runtimePackage?: Record<string, unknown>;
  readonly metadata?: (metadata: Record<string, unknown>) => Record<string, unknown>;
  /** Changes the payload after its digests were computed. */
  readonly tamper?: (files: Map<string, Buffer>) => void;
  /** Entries appended after the package's own, under any path. */
  readonly extraEntries?: readonly FixtureEntry[];
}

export interface PackageFixture {
  readonly archive: Buffer;
  readonly sha256: string;
}

async function readTree(root: string): Promise<Map<string, Buffer>> {
  const files = new Map<string, Buffer>();
  for (const entry of await readdir(root, { recursive: true, withFileTypes: true })) {
    if (entry.isFile()) {
      const absolute = path.join(entry.parentPath, entry.name);
      files.set(path.relative(root, absolute).split(path.sep).join("/"), await readFile(absolute));
    }
  }
  return files;
}

/**
 * A valid any-target package of a minimal module: a server stub with no imports, one migration, a
 * notices file, the generated runtime package.json, and complete metadata. Every option changes one
 * thing, so a test can break exactly the rule it is about.
 */
export async function modulePackageFixture(
  options: PackageFixtureOptions = {},
): Promise<PackageFixture> {
  const id = options.id ?? "example";
  const version = options.version ?? "0.1.0";
  const scratch = await mkdtemp(path.join(tmpdir(), "ekklesia-package-fixture-"));
  let files: Map<string, Buffer>;
  try {
    const created = await createMigrationModule(scratch, id, {
      ...(options.schemaSource === undefined ? {} : { schemaSource: options.schemaSource }),
      serverSource:
        options.serverSource ??
        `export default { id: ${JSON.stringify(id)}, version: ${JSON.stringify(version)}, register() {} };\n`,
    });
    files = await readTree(created.moduleDirectory);
  } finally {
    await rm(scratch, { force: true, recursive: true });
  }

  const manifest = JSON.parse(
    files.get("ekklesia.module.json")?.toString("utf8") ?? "{}",
  ) as Record<string, unknown>;
  files.set(
    "ekklesia.module.json",
    Buffer.from(
      `${JSON.stringify(options.manifest ? options.manifest(manifest) : { ...manifest, version }, null, 2)}\n`,
    ),
  );
  files.set(
    "package.json",
    Buffer.from(
      `${JSON.stringify(
        options.runtimePackage ?? {
          name: `@test/module-${id}`,
          version,
          private: true,
          type: "module",
          ekklesia: { layer: "module" },
        },
        null,
        2,
      )}\n`,
    ),
  );
  files.set("THIRD_PARTY_NOTICES", Buffer.from("No third-party software is included.\n"));

  const listed = [...files.entries()]
    .sort(([left], [right]) => (left < right ? -1 : left > right ? 1 : 0))
    .map(([filePath, data]) => ({ path: filePath, size: data.length, sha256: sha256(data) }));
  const baseMetadata: Record<string, unknown> = {
    packageFormat: 1,
    module: { id, version },
    target: "any",
    runtime: { node: ">=20" },
    provenance: {
      revision: "86ae907f59458508e3277666cdd214f5bd7c1078",
      packager: { name: "@ekklesia/module-pack", version: "0.1.2" },
    },
    incorporates: { "@ekklesia/module-sdk": "0.1.2" },
    files: listed,
  };
  const metadata = options.metadata ? options.metadata(baseMetadata) : baseMetadata;
  options.tamper?.(files);

  const directories = new Set<string>([id]);
  for (const filePath of files.keys()) {
    const segments = filePath.split("/");
    for (let index = 1; index < segments.length; index += 1) {
      directories.add(`${id}/${segments.slice(0, index).join("/")}`);
    }
  }
  const all = new Map<string, FixtureEntry>();
  for (const directory of directories) {
    all.set(directory, { path: directory, type: "directory" });
  }
  for (const [filePath, data] of files) {
    all.set(`${id}/${filePath}`, { path: `${id}/${filePath}`, data });
  }
  all.set(`${id}/ekklesia.package.json`, {
    path: `${id}/ekklesia.package.json`,
    data: `${JSON.stringify(metadata, null, 2)}\n`,
  });
  const ordered = [...all.values()].sort((left, right) =>
    left.path < right.path ? -1 : left.path > right.path ? 1 : 0,
  );
  const archive = tarGz([...ordered, ...(options.extraEntries ?? [])]);
  return { archive, sha256: sha256(archive) };
}