import fs from "node:fs/promises";
import path from "node:path";
import { execFile as callback, spawn } from "node:child_process";
import { createWriteStream } from "node:fs";
import { promisify } from "node:util";
import { fileURLToPath } from "node:url";
const execFile = promisify(callback);
const environment = () => ({ ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", GIT_TERMINAL_PROMPT: "0" });
export const checkerIdentity = () =>
  process.env.QUIXOS_CHECK_GENERATOR ?? path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");

/** Checking snapshots jj, but never publishes or activates the working copy. */
export async function snapshotCommit(root: string): Promise<string> {
  const run = async (...args: string[]) =>
    (await execFile("jj", args, { cwd: root, env: environment() })).stdout.trim();
  // A single normal log snapshots the working copy and observes both values
  // from that exact revision. Separate status/log processes add no evidence.
  const [conflict, commit] = (await run("log", "--no-graph", "-r", "@", "-T", 'conflict ++ "\\n" ++ commit_id')).split(
    "\n",
  );
  if (conflict !== "false") throw new Error("Resolve source conflicts before verification");
  if (!commit || !/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(commit))
    throw new Error("Verification requires an exact jj commit");
  await execFile("git", ["diff", "--exit-code", "--no-ext-diff", "--no-textconv", commit, "--"], {
    cwd: root,
    env: environment(),
  });
  const { stdout } = await execFile("git", ["ls-files", "--others", "--exclude-standard", "-z"], { cwd: root });
  if (stdout) throw new Error("Source contains files not captured by jj; inspect jj tracking before verification");
  return commit;
}

/** Use Git's actual committed tree, never dirty overlays labelled as old pins. */
export async function checkoutCommit(root: string, commit: string, destination: string) {
  await fs.mkdir(destination, { recursive: true });
  const archive = await execFile("git", ["archive", "--format=tar", commit], {
    cwd: root,
    encoding: "buffer",
    maxBuffer: 128 * 1024 * 1024,
  });
  await new Promise<void>((resolve, reject) => {
    const child = spawn("tar", ["-xf", "-", "-C", destination], { stdio: ["pipe", "ignore", "pipe"] });
    let error = "";
    child.stderr.on("data", (chunk) => {
      error += chunk;
    });
    child.on("error", reject);
    child.on("close", (code) =>
      code === 0 ? resolve() : reject(new Error(`Cannot extract committed source: ${error}`)),
    );
    child.stdin.on("error", reject);
    child.stdin.end(archive.stdout);
  });
}

/** Shared by provisional checks, template publication and host activation.
 * The Nix derivation is the cached check; its metadata is internal provenance,
 * not a certificate authored or approved by the workspace agent.
 */
export async function buildCheckedPackage(source: string, schema: string, packageRevisionId: string): Promise<string> {
  const generator =
    process.env.QUIXOS_CHECK_GENERATOR ?? path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
  if (!/^\/nix\/store\/[^/]+$/.test(generator))
    throw new Error("Run verification with the installed Quixos tooling (its exact Nix checker is required)");
  const builder = path.join(generator, "share/checked-package.nix");
  await fs.access(builder);
  return await new Promise((resolve, reject) => {
    const child = spawn(
      "nix",
      [
        "build",
        "--impure",
        "--file",
        builder,
        "--argstr",
        "source",
        source,
        "--argstr",
        "schema",
        schema,
        "--argstr",
        "generator",
        generator,
        "--argstr",
        "packageRevisionId",
        packageRevisionId,
        "--no-link",
        "--print-out-paths",
        "-L",
      ],
      { env: environment(), stdio: ["ignore", "pipe", "inherit"] },
    );
    let output = "";
    child.stdout.on("data", (chunk) => {
      output += chunk;
    });
    child.on("error", reject);
    child.on("close", (code) => {
      const artifact = output.trim();
      if (code !== 0 || !/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+$/.test(artifact))
        reject(new Error(`Checked Nix build failed (${code}); see build diagnostics above`));
      else resolve(artifact);
    });
  });
}

/** Exact remote source DAG; the Nix checker owns schema construction and all
 * nested fetches. Keep build noise in a named log, with a bounded failure tail. */
export async function buildImmutableCandidate(
  source: { repository: string; commit: string },
  kind: "workspace" | "interface" | "package" | "build",
  logFile: string,
  contractOnly = false,
  observe?: (phase: "nixEvaluationMs" | "nixBuildMs", ms: number) => void,
  workspaceId?: string,
  platformSource?: { repository: string; commit: string; directory: string },
): Promise<string> {
  if (workspaceId !== undefined && (kind !== "workspace" || !/^[a-zA-Z0-9][a-zA-Z0-9:._-]{0,255}$/.test(workspaceId)))
    throw new Error("Instance binding requires a valid Workspace identity and a Workspace root");
  if (!/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(source.commit))
    throw new Error("An immutable candidate requires an exact commit");
  const url = new URL(source.repository);
  if (url.protocol !== "https:" || url.username || url.password || url.search || url.hash)
    throw new Error("Candidate origin must be credential-free HTTPS");
  if (
    platformSource &&
    (Object.keys(platformSource).sort().join(",") !== "commit,directory,repository" ||
      !/^[a-f0-9]{40}$/.test(platformSource.commit) ||
      !/^\/nix\/store\/[a-z0-9]{32}-[^/\s]+$/.test(platformSource.directory))
  )
    throw Error("Invalid immutable platform source input");
  const generator =
    process.env.QUIXOS_CHECK_GENERATOR ?? path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
  if (!/^\/nix\/store\/[^/]+$/.test(generator)) throw new Error("Use the installed Quixos checker");
  const builder = path.join(generator, "share/checked-candidate.nix");
  await fs.access(builder);
  const log = createWriteStream(logFile, { flags: "wx", mode: 0o600 });
  await new Promise<void>((resolve, reject) => {
    log.once("open", () => resolve());
    log.once("error", reject);
  });
  let logBytes = 0;
  const run = async (executable: string, args: string[]) =>
    await new Promise<string>((resolve, reject) => {
      let output = "",
        tail = "",
        failure: Error | undefined;
      const child = spawn(executable, args, { env: environment(), stdio: ["ignore", "pipe", "pipe"] });
      const failedLog = (error: Error) => {
        failure = error;
        child.kill();
      };
      log.on("error", failedLog);
      child.stdout.on("data", (chunk) => {
        if (failure) return;
        if (Buffer.byteLength(output) + chunk.length > 65536)
          failedLog(new Error("Candidate checker output exceeds 64 KiB"));
        else output += chunk;
      });
      child.stderr.on("data", (chunk) => {
        if (failure) return;
        logBytes += chunk.length;
        if (logBytes > 16 * 1024 * 1024) {
          failedLog(new Error("Candidate checker log exceeds 16 MiB"));
          return;
        }
        log.write(chunk);
        tail = (tail + String(chunk)).slice(-6000);
      });
      child.on("error", (error) => {
        failure = error;
      });
      child.on("close", (code) => {
        log.off("error", failedLog);
        if (failure) reject(failure);
        else if (code !== 0) reject(new Error(`Candidate Nix check failed (${code}). Full log: ${logFile}\n${tail}`));
        else resolve(output.trim());
      });
    });
  const timed = async (phase: "nixEvaluationMs" | "nixBuildMs", action: () => Promise<string>) => {
    const started = performance.now();
    try {
      return await action();
    } finally {
      observe?.(phase, Math.round(performance.now() - started));
    }
  };
  let gcDirectory: string | undefined;
  try {
    // Evaluation includes import-from-derivation builds (locks and contracts).
    // Build the resulting derivation directly, without evaluating the DAG twice.
    // Keep the derivation alive across the two processes, including concurrent
    // GC. This temporary root is removed on success and on verification failure.
    gcDirectory = await fs.mkdtemp(path.join(path.dirname(logFile), ".gc-root-"));
    const gcRoot = path.join(gcDirectory, "candidate");
    const derivation = await timed("nixEvaluationMs", async () => {
      await run("nix-instantiate", [
        builder,
        "--argstr",
        "repository",
        source.repository,
        "--argstr",
        "commit",
        source.commit,
        "--argstr",
        "kind",
        kind,
        "--argstr",
        "generator",
        generator,
        "--arg",
        "contractOnly",
        contractOnly ? "true" : "false",
        ...(workspaceId === undefined ? [] : ["--argstr", "workspaceId", workspaceId]),
        ...(platformSource ? ["--argstr", "platformSourceJSON", JSON.stringify(platformSource)] : []),
        "--add-root",
        gcRoot,
        "--indirect",
      ]);
      return await fs.readlink(gcRoot);
    });
    if (!/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+\.drv$/.test(derivation))
      throw new Error("Nix returned an invalid candidate derivation");
    const artifact = await timed("nixBuildMs", () =>
      run("nix", ["build", derivation + "^*", "--no-link", "--print-out-paths", "-L"]),
    );
    if (!/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+$/.test(artifact))
      throw new Error("Nix returned an invalid candidate artifact");
    return artifact;
  } finally {
    await new Promise<void>((resolve) => log.end(resolve));
    if (gcDirectory) await fs.rm(gcDirectory, { recursive: true, force: true });
  }
}