#!/usr/bin/env node
// Decides which expensive CI lanes a pull request needs, from the files it changes since the merge base.
//
// Usage: node ci-lanes.mjs --base <sha> --head <sha> [--github-output]
//
// CI runs the base branch's copy of this script against the pull request's diff, so a pull request cannot widen its
// own exemptions; a change to this script runs every lane until it is on the base branch. It uses only Node and git.
//
// Lanes (each an output, true or false):
// - linux: the Linux build and test shards, the TypeScript 7 parity sweep and the smaller Linux, Windows and mobile
//   jobs. Off only when every change is documentation.
// - macos: the macOS native build, the darwin test shards and the macOS LLVM artifact jobs. On when the change touches
//   a darwin package, a path naming darwin, macOS, iOS or Mach-O, the darwin test files of scripts/ci-test-plan.mjs,
//   the LLVM helper (native/, packages/llvm-*) or the shared runtime pack code, or changed lines in packages/{runtime,compiler,cli} that mention darwin-specific APIs (__APPLE__, kqueue, Mach-O
//   and similar).
// - effects: the Effect suites. On when the change touches their harness or fixtures.
// - bootstrap: the native bootstrap seed and self-rebuild contracts. On when the change touches the bootstrap scripts,
//   the native CLI build, the cli-* packages or the self-hosting tests.
// Every lane is on when the change touches CI configuration, the workspace manifests or lockfile, vitest
// configuration, the shared test harness modules or this script, or when the diff cannot be computed. Pushes to main
// and the nightly sweep do not use this script: they run every lane.
import { execFileSync } from "node:child_process";
import { appendFileSync } from "node:fs";

const lanes = ["linux", "macos", "effects", "bootstrap"];

const everything = [
  /^\.github\//,
  /^scripts\/ci-/,
  /^scripts\/bootstrap-seed\.mjs$/,
  /^package\.json$/,
  /^pnpm-lock\.yaml$/,
  /^pnpm-workspace\.yaml$/,
  /^\.node-version$/,
  /^patches\//,
  /^vitest\.config\.ts$/,
  /^tests\/harness\/(shard\.ts|suite-lock\.mjs)$/,
  /^packages\/[^/]+\/package\.json$/,
];
const documentation = [/^docs\//, /\.mdx?$/, /^LICENSE$/, /^CHANGELOG\.md$/];
const darwinPath = /darwin|macos|ios|apple|mach-?o/i;
// Native code generation and runtime packs every platform shares.
const sharedNative = /^native\/|^packages\/(llvm-[^/]+|runtime-pack-common)\//;
const darwinFiles = [
  "packages/cli/test/bootstrap.test.ts",
  "packages/cli/test/native-link-info.test.ts",
  "packages/cli/test/native-output.test.ts",
  "packages/cli/test/runtime-pack.test.ts",
  "packages/compiler/test/debug-variables.test.ts",
  "packages/compiler/test/native-codegen-integration.test.ts",
  "packages/compiler/test/source-debugging.test.ts",
  "packages/runtime/test/string.test.ts",
  "tests/harness/ffi-callback-pool.test.ts",
  "tests/harness/ffi-catalog.test.ts",
  "tests/harness/ffi-frameworks.test.ts",
  "tests/harness/library-callbacks.test.ts",
  "tests/harness/library-dispatch.test.ts",
  "tests/harness/library-multi.test.ts",
  "tests/harness/native-object-example.test.ts",
  "tests/harness/runtime-tree-shaking.test.ts",
  "tests/harness/terminal-geometry.test.ts",
  "tests/harness/llvm-differential.test.ts",
];
const darwinLine =
  /__APPLE__|__MACH__|TARGET_OS_|kqueue|kevent|\bdarwin\b|Darwin|Mach-?O|macho|MachO|mach_|dyld|CoreFoundation|libSystem/;
const effectPath = /^tests\/(harness\/effect|fixtures\/effect)/;
const bootstrapPath =
  /^scripts\/(bootstrap-seed|ci-native-bootstrap|build-native-cli)|^packages\/cli-[^/]+\/|^tests\/harness\/(self-hosting|bootstrap-seed|ci-native-bootstrap|native-cli-packaging)/;

function git(...args) {
  return execFileSync("git", args, { encoding: "utf8", maxBuffer: 1 << 28 });
}

/** The lanes a list of changed files needs, with the reason for each lane that is on. */
export function select(files, changedLines) {
  const on = Object.fromEntries(lanes.map((lane) => [lane, false]));
  const reasons = [];
  const all = (why) => {
    for (const lane of lanes) on[lane] = true;
    reasons.push(`${why}: every lane`);
  };
  for (const file of files) {
    if (everything.some((re) => re.test(file))) {
      all(file);
      continue;
    }
    if (documentation.some((re) => re.test(file))) continue;
    on.linux = true;
    if (darwinPath.test(file) || darwinFiles.includes(file) || sharedNative.test(file)) {
      if (!on.macos) reasons.push(`${file}: macos`);
      on.macos = true;
    }
    if (effectPath.test(file)) {
      if (!on.effects) reasons.push(`${file}: effects`);
      on.effects = true;
    }
    if (bootstrapPath.test(file)) {
      if (!on.bootstrap) reasons.push(`${file}: bootstrap`);
      on.bootstrap = true;
    }
  }
  const line = changedLines.find((l) => darwinLine.test(l.text));
  if (line !== undefined && !on.macos) {
    reasons.push(`${line.file}: a changed line mentions a darwin-specific API: macos`);
    on.macos = true;
  }
  if (files.length > 0 && !on.linux) reasons.push("documentation only");
  return { on, reasons };
}

/** Added and removed lines of the C, header and TypeScript sources below packages/{runtime,compiler,cli}. */
function changedLinesOf(base, head) {
  const out = git(
    "diff",
    "-U0",
    "--no-color",
    `${base}...${head}`,
    "--",
    "packages/runtime",
    "packages/compiler",
    "packages/cli",
  );
  const lines = [];
  let file = "";
  for (const line of out.split("\n")) {
    if (line.startsWith("+++ ")) file = line.slice(6);
    else if (/^[+-](?![+-])/.test(line)) lines.push({ file, text: line.slice(1) });
  }
  return lines;
}

function main() {
  const args = process.argv.slice(2);
  const option = (name) => (args.includes(name) ? args[args.indexOf(name) + 1] : undefined);
  const base = option("--base");
  const head = option("--head") ?? "HEAD";
  let result;
  try {
    if (!base) throw new Error("no --base");
    const files = git("diff", "--name-only", "--no-color", `${base}...${head}`)
      .split("\n")
      .filter(Boolean);
    result = select(files, changedLinesOf(base, head));
  } catch (error) {
    result = {
      on: Object.fromEntries(lanes.map((lane) => [lane, true])),
      reasons: [`diff unavailable (${error.message}): every lane`],
    };
  }
  for (const lane of lanes) console.log(`${lane}=${result.on[lane]}`);
  for (const reason of result.reasons) console.log(`  ${reason}`);
  if (args.includes("--github-output") && process.env.GITHUB_OUTPUT)
    appendFileSync(
      process.env.GITHUB_OUTPUT,
      lanes.map((lane) => `${lane}=${result.on[lane]}\n`).join(""),
    );
}

if (process.argv[1] && import.meta.url === `file://${process.argv[1]}`) main();