#!/usr/bin/env node
import { createHash } from "node:crypto";
import { spawnSync } from "node:child_process";
import { mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs";
import { dirname, join, resolve } from "node:path";

const [mode, infoArg, outputArg] = process.argv.slice(2);
if ((mode !== "cc" && mode !== "ld") || !infoArg || !outputArg) {
  console.error("usage: node link.mjs <cc|ld> <native-link-info.json> <output>");
  process.exitCode = 2;
} else {
  const info = JSON.parse(readFileSync(infoArg, "utf8"));
  if (info.schema !== "scriptc.native-link-info.v1") {
    throw new Error(`unsupported native link info schema: ${info.schema}`);
  }
  const runtimePackage = JSON.parse(
    readFileSync(join(info.runtime_pack.root, "package.json"), "utf8"),
  );
  if (
    runtimePackage.name !== info.runtime_pack.package ||
    runtimePackage.version !== info.runtime_pack.version
  ) {
    throw new Error(
      `runtime pack identity mismatch: expected ${info.runtime_pack.package}@${info.runtime_pack.version} ` +
        `at ${info.runtime_pack.root}, found ${runtimePackage.name ?? "<unnamed>"}@${runtimePackage.version ?? "<unversioned>"}`,
    );
  }
  const run = (command, args, options = {}) => {
    const result = spawnSync(command, args, { stdio: "inherit", ...options });
    if (result.error) throw result.error;
    if (result.status !== 0) throw new Error(`${command} exited ${result.status}`);
  };
  const capture = (command, args) => {
    const result = spawnSync(command, args, { encoding: "utf8" });
    if (result.error) throw result.error;
    if (result.status !== 0) throw new Error(result.stderr || `${command} exited ${result.status}`);
    return result.stdout.trim();
  };

  const infoPath = resolve(infoArg);
  const output = resolve(outputArg);
  const buildDir = join(dirname(infoPath), `.native-link-${mode}`);
  rmSync(buildDir, { recursive: true, force: true });
  mkdirSync(buildDir, { recursive: true });
  const runtimeObjects = [];
  const vendorArchives = [];
  for (const [kind, artifacts] of [["objects", info.runtime_pack.objects], ["archives", info.runtime_pack.archives]]) {
    for (const artifact of artifacts) {
      if (artifact.path.startsWith("/") || artifact.path.split(/[\\/]/).includes("..")) throw new Error("invalid runtime artifact path");
      const bytes = readFileSync(join(info.runtime_pack.root, artifact.path));
      if (bytes.length !== artifact.size || createHash("sha256").update(bytes).digest("hex") !== artifact.sha256) {
        throw new Error(`runtime pack hash mismatch: ${artifact.path}`);
      }
      const destination = join(buildDir, artifact.path);
      mkdirSync(dirname(destination), { recursive: true });
      writeFileSync(destination, bytes, { mode: 0o400 });
      (kind === "objects" ? runtimeObjects : vendorArchives).push(destination);
    }
  }

  const inputs = [
    info.program.object,
    ...info.ffi.libraries,
    ...runtimeObjects,
    ...vendorArchives,
  ];
  const libraries = info.link.system_libraries.map((name) => `-l${name}`);
  const frameworks = info.link.frameworks.flatMap((name) => ["-framework", name]);
  if (mode === "cc") {
    // Darwin compiler drivers add libSystem themselves. It remains explicit
    // in the document because a direct ld invocation must name it.
    const driverLibraries = info.link.system_libraries
      .filter((name) => name !== "System")
      .map((name) => `-l${name}`);
    run("clang", [
      ...info.link.driver_flags,
      ...inputs,
      ...driverLibraries,
      ...frameworks,
      "-o", output,
    ]);
  } else {
    const sdk = capture("xcrun", ["--sdk", "macosx", "--show-sdk-path"]);
    const sdkVersion = capture("xcrun", ["--sdk", "macosx", "--show-sdk-version"]);
    const linker = capture("xcrun", ["--sdk", "macosx", "--find", "ld"]);
    run(linker, [
      "-arch", info.target.architecture,
      "-platform_version", "macos", info.target.minimum_os, sdkVersion,
      "-syslibroot", sdk,
      ...(info.link.driver_flags.includes("-Wl,-dead_strip") ? ["-dead_strip"] : []),
      ...inputs,
      ...libraries,
      ...frameworks,
      "-o", output,
    ]);
  }
}