// Evaluate the production compiler constructor; its checked build is a prerequisite.
import assert from "node:assert/strict";
import fs from "node:fs/promises";
import os from "node:os";
import path from "node:path";
import { spawnSync } from "node:child_process";
import { createHash } from "node:crypto";

const config = JSON.parse(await fs.readFile(process.argv[2], "utf8"));
const output = process.argv[3];
const scratch = await fs.mkdtemp(path.join(os.tmpdir(), "protocol-source-"));
const source = path.join(scratch, "source");
const nixString = (value) => JSON.stringify(value).replaceAll("${", "\\${");
async function writable(directory) {
  await fs.chmod(directory, 0o700);
  for (const item of await fs.readdir(directory, { withFileTypes: true })) {
    const file = path.join(directory, item.name);
    if (item.isDirectory()) await writable(file);
    else {
      const info = await fs.stat(file);
      await fs.chmod(file, info.mode & 0o111 ? 0o700 : 0o600);
    }
  }
}
function identity() {
  const expression = `let
    pkgs = import (/. + ${nixString(config.nixpkgs)}) { system = ${nixString(config.system)}; };
    compiler = import ((/. + ${nixString(source)}) + "/default.nix") {
      inherit pkgs;
      nixpkgsNarHash = builtins.appendContext ${nixString(config.nixpkgsNarHash)}
        (builtins.fromJSON ${nixString(JSON.stringify(config.narHashContext))});
    };
  in {
    derivation = compiler.drvPath;
    yarn = compiler.yarn-freestanding.drvPath;
    source = toString compiler.src;
    metadata = (import ((/. + ${nixString(source)}) + "/source-qualification-metadata.nix")) compiler;
  }`;
  const result = spawnSync(
    "nix",
    [
      "--store",
      "local?root=" + process.env.QUIXOS_PROTOCOL_EVALUATION_STORE,
      "eval",
      "--offline",
      "--impure",
      "--json",
      "--expr",
      expression,
    ],
    { encoding: "utf8", timeout: 30000, maxBuffer: 1048576 },
  );
  assert.equal(result.status, 0, result.error?.message ?? result.stderr);
  return JSON.parse(result.stdout);
}
function summarized(value) {
  const text = JSON.stringify(value) ?? "undefined";
  return text.length < 500
    ? value
    : {
        bytes: Buffer.byteLength(text),
        sha256: createHash("sha256").update(text).digest("hex"),
        prefix: text.slice(0, 180),
      };
}
function structuralDifferences(actual, expected, field = "", result = []) {
  if (JSON.stringify(actual) === JSON.stringify(expected)) return result;
  if (
    Array.isArray(actual) &&
    Array.isArray(expected) &&
    [...actual, ...expected].every((x) => typeof x === "string")
  ) {
    result.push({
      field,
      onlyActual: actual.filter((x) => !expected.includes(x)),
      onlyExpected: expected.filter((x) => !actual.includes(x)),
      actualCount: actual.length,
      expectedCount: expected.length,
      sequenceChanged: true,
    });
  } else if (
    actual &&
    expected &&
    typeof actual === "object" &&
    typeof expected === "object" &&
    !Array.isArray(actual) &&
    !Array.isArray(expected)
  ) {
    for (const key of new Set([...Object.keys(actual), ...Object.keys(expected)]))
      structuralDifferences(actual[key], expected[key], field ? field + "." + key : key, result);
  } else {
    const difference = { field, actual: summarized(actual), expected: summarized(expected) };
    if (typeof actual === "string" && typeof expected === "string" && Math.max(actual.length, expected.length) >= 500) {
      let offset = 0;
      while (offset < actual.length && offset < expected.length && actual[offset] === expected[offset]) offset++;
      difference.offset = offset;
      difference.actualExcerpt = actual.slice(Math.max(0, offset - 80), offset + 200);
      difference.expectedExcerpt = expected.slice(Math.max(0, offset - 80), offset + 200);
    }
    result.push(difference);
  }
  return result;
}
function baselineDifference(baseline) {
  const { metadata, ...identities } = baseline;
  console.log(
    "PROTOCOL_SOURCE_BASELINE: " +
      JSON.stringify({
        actual: identities,
        expected: config.expected,
        expectedSource: config.expectedSource,
        evaluatorVersion: config.evaluatorVersion,
        pinnedNixVersion: config.pinnedNixVersion,
        narHashContext: config.narHashContext,
      }),
  );
  console.log(
    "PROTOCOL_SOURCE_BASELINE_DIFF: " +
      JSON.stringify(structuralDifferences(metadata, config.expectedMetadata)).slice(0, 10000),
  );
}
async function edit(file, mutate, check) {
  const before = await fs.readFile(file, "utf8");
  try {
    await fs.writeFile(file, mutate(before));
    await check();
  } finally {
    await fs.writeFile(file, before);
  }
}
const cases = [];
async function record(name, check) {
  await check();
  cases.push(name);
  console.log("PROTOCOL_SOURCE_INPUT: " + name);
}
try {
  await fs.cp(config.source, source, { recursive: true });
  await writable(source);
  const baseline = identity();
  if (baseline.derivation !== config.expected) baselineDifference(baseline);
  await record("real production compiler and generated Yarn launcher identities", async () => {
    assert.equal(baseline.derivation, config.expected);
    assert.equal(baseline.yarn, config.yarn);
  });
  for (const file of ["README.md", "flake.nix", "default.nix", "yarn-project.nix"]) {
    await record(file + " commentary preserves compiler identity", () =>
      edit(
        path.join(source, file),
        (text) => text + (file.endsWith(".nix") ? "\n# source qualification\n" : "\nSource qualification.\n"),
        async () => assert.deepEqual(identity(), baseline),
      ),
    );
  }
  await record("new documentation preserves compiler identity", async () => {
    const file = path.join(source, "NOTES.md");
    try {
      await fs.writeFile(file, "qualification\n");
      assert.deepEqual(identity(), baseline);
    } finally {
      await fs.rm(file, { force: true });
    }
  });
  async function compilerOnly() {
    const changed = identity();
    assert.notEqual(changed.derivation, baseline.derivation);
    assert.equal(changed.yarn, baseline.yarn);
  }
  for (const file of [
    "src/capability-language/cli.ts",
    "test/emit-managed.ts",
    "grammar/QuixosCapability.g4",
    "proto/quixos/refs.proto",
    "nix/check-package.mjs",
    "package.json",
    "yarn.lock",
    ".yarnrc.yml",
    ".yarn/plugins/yarn-plugin-nixify.cjs",
    "tsconfig.json",
    "tsconfig.build.json",
    "tsconfig.test.json",
  ]) {
    await record(file + " remains a compiler input", () =>
      edit(path.join(source, file), (text) => text + "\n", compilerOnly),
    );
  }
  for (const file of ["src/future.ts", "test/future.ts", "nix/future.nix"]) {
    await record(file + " is included without a file inventory update", async () => {
      const target = path.join(source, file);
      try {
        await fs.writeFile(target, "qualification\n");
        await compilerOnly();
      } finally {
        await fs.rm(target, { force: true });
      }
    });
  }
  await record("executable recipe changes invalidate compiler identity", () =>
    edit(
      path.join(source, "default.nix"),
      (text) => {
        assert(text.includes("runHook preBuild"));
        return text.replace("runHook preBuild", "runHook preBuild\n    echo qualification");
      },
      compilerOnly,
    ),
  );
  await record("selected generated archive pin remains a compiler input", () =>
    edit(
      path.join(source, "yarn-project.nix"),
      (text) => {
        const changedHash = "sha512-" + Buffer.alloc(64, 0x42).toString("base64");
        const pattern = /("@types\/node@npm:[^\n]+hash = ")[^"]+(";)/;
        assert(pattern.test(text));
        return text.replace(pattern, (_, before, after) => before + changedHash + after);
      },
      async () => {
        await compilerOnly();
        assert.equal(identity().source, baseline.source);
      },
    ),
  );
  await record("installed Nixpkgs trust identity remains a compiler input", async () => {
    const previous = config.nixpkgsNarHash;
    try {
      config.nixpkgsNarHash = "sha256-" + Buffer.alloc(32, 0x42).toString("base64");
      assert.notEqual(config.nixpkgsNarHash, previous);
      await compilerOnly();
      assert.equal(identity().source, baseline.source);
    } finally {
      config.nixpkgsNarHash = previous;
    }
  });
  assert.deepEqual(identity(), baseline, "Every private mutation was restored");
  await fs.mkdir(output, { recursive: true });
  await fs.writeFile(
    path.join(output, "protocol-source.json"),
    JSON.stringify(
      {
        codec: "quixos-protocol-source-qualification/1",
        derivation: baseline.derivation,
        yarn: baseline.yarn,
        source: baseline.source,
        cases,
        metadataContext: config.narHashContext,
        evaluatorVersion: config.evaluatorVersion,
        pinnedNixVersion: config.pinnedNixVersion,
        nestedBuilds: false,
        guestExecution: false,
      },
      null,
      2,
    ) + "\n",
  );
} finally {
  await fs.rm(scratch, { recursive: true, force: true });
}