import { createHash } from "node:crypto";
import { chmod, copyFile, mkdir, readFile, rename, rm, stat, utimes, writeFile } from "node:fs/promises";
import { basename, dirname, join, resolve } from "node:path";
import type { FrontendInputSnapshot } from "../frontend/input-tracker.js";
import { frontendInputsStillMatch, validFrontendInputSnapshot } from "../frontend/input-tracker.js";
import { compilerReleaseVersion } from "../library/sidecar.js";
import { nativeArtifactDependenciesStillMatch, type NativeArtifactDependency } from "../backend/native-toolchain.js";
import type { CompilerImplementationDependency } from "../library/compiler-self-identity.js";
import { compilerImplementationDependenciesStillMatch, compilerImplementationRoot } from "../library/compiler-self-identity.js";
import {
  cacheKey as sharedCacheKey,
  digest,
  frontendOutputExclusions,
  installBytes,
  outputPaths,
  readCachedFile,
  stampIntegrity as sharedStampIntegrity,
  stampPath as sharedStampPath,
  validNativeFeatures as validSharedNativeFeatures,
} from "../library/cache-primitives.js";

interface CachedExecutableFile {
  name: string;
  digest: string;
}

export interface EarlyExecutableNativeFeatures {
  backend: "c" | "llvm";
  /** Omitted is the historical release posture. */
  optimization?: "dev";
  llvmRefusal?: string;
  dynamic: boolean;
  regex: boolean;
  copying: boolean;
  textDecoderLegacy: boolean;
  fileHandle: boolean;
  fetch: boolean;
  netIsland: boolean;
  zlib: boolean;
  assert: boolean;
  inspect: boolean;
  dynInvoke: boolean;
  dc: boolean;
  dynAsync: boolean;
  events: boolean;
  emitter: boolean;
  symbol: boolean;
  searchParams: boolean;
  qs: boolean;
  parseArgs: boolean;
  stream: boolean;
  net: boolean;
  http: boolean;
  http2: boolean;
  dgram: boolean;
  watch: boolean;
  foreignFfi: boolean;
  nodeTest: boolean;
  tls: boolean;
  tlsCa: boolean;
}

interface EarlyExecutableCacheStamp {
  version: 1;
  key: string;
  frontend: FrontendInputSnapshot;
  files: {
    translationUnit: CachedExecutableFile;
    ir: CachedExecutableFile | null;
    executable: CachedExecutableFile | null;
  };
  nativeDependencies: NativeArtifactDependency[] | null;
  native: EarlyExecutableNativeFeatures;
  integrity: string;
}

export interface EarlyExecutableCacheOptions {
  entryPath: string;
  outDir: string;
  outPath: string;
  emitIr: boolean;
  sanitize: boolean;
  dynamic: boolean;
  backend: "auto" | "c" | "llvm";
  /** Omitted is the historical release posture and preserves v1 keys. */
  optimization?: "dev";
  npmStatic: readonly string[] | "auto" | null;
  /** Raw manifest identity: path and bytes. Native archives remain under the
   * stricter native cache's independent dependency validation. */
  ffiProfile: { path: string; bytes: Uint8Array } | null;
  target: string;
  compiler: string[];
  nativeEnvironment: string;
  nodeVersion: string;
  implementation: string;
  implementationDependencies: CompilerImplementationDependency[];
}

export type EarlyExecutableRouteOptions = Omit<
  EarlyExecutableCacheOptions,
  "implementation" | "implementationDependencies"
>;

interface EarlyExecutableRouteStamp {
  version: 1;
  key: string;
  implementation: string;
  integrity: string;
}

interface EarlyExecutableImplementationProof {
  version: 1;
  implementation: string;
  dependencies: CompilerImplementationDependency[];
  integrity: string;
}

export interface EarlyExecutableCacheHit {
  cPath: string;
  irPath?: string;
  /** True when the final executable was restored after native dependencies
   * validated. False restores only frontend artifacts and must call compileC. */
  executableRestored: boolean;
  native: EarlyExecutableNativeFeatures;
  frontend: FrontendInputSnapshot;
}

export interface EarlyExecutableCachePublish extends EarlyExecutableCacheHit {
  nativeDependencies?: NativeArtifactDependency[];
}

const BOOLEAN_NATIVE_KEYS = [
  "dynamic",
  "regex",
  "copying",
  "textDecoderLegacy",
  "fileHandle",
  "fetch",
  "netIsland",
  "zlib",
  "assert",
  "inspect",
  "dynInvoke",
  "dc",
  "dynAsync",
  "events",
  "emitter",
  "symbol",
  "searchParams",
  "qs",
  "parseArgs",
  "stream",
  "net",
  "http",
  "http2",
  "dgram",
  "watch",
  "foreignFfi",
  "nodeTest",
  "tls",
  "tlsCa",
] as const satisfies readonly (keyof EarlyExecutableNativeFeatures)[];

function validNativeFeatures(value: unknown): value is EarlyExecutableNativeFeatures {
  return validSharedNativeFeatures<EarlyExecutableNativeFeatures>(
    value,
    BOOLEAN_NATIVE_KEYS,
    (native) =>
      (native.optimization === undefined || native.optimization === "dev") &&
      (native.llvmRefusal === undefined || typeof native.llvmRefusal === "string"),
  );
}

function cacheKey(options: EarlyExecutableCacheOptions): string {
  const ffiParts: (string | Uint8Array)[] = options.ffiProfile === null
    ? ["<ffi-off>"]
    : [resolve(options.ffiProfile.path), options.ffiProfile.bytes];
  return sharedCacheKey("early-executable-v1", [
    resolve(options.entryPath),
    resolve(options.outDir),
    resolve(options.outPath),
    options.emitIr ? "emit-ir" : "no-ir",
    options.sanitize ? "sanitize" : "plain",
    options.dynamic ? "dynamic" : "static",
    options.backend,
    ...(options.optimization === "dev" ? ["optimization-dev"] : []),
    options.npmStatic === null
      ? "<npm-static-off>"
      : options.npmStatic === "auto"
        ? "<npm-static-auto>"
        : JSON.stringify(options.npmStatic),
    options.target,
    options.compiler.join("\x1f"),
    options.nativeEnvironment,
    options.nodeVersion,
    options.implementation,
    ...ffiParts,
  ]);
}

function routeKey(options: EarlyExecutableRouteOptions): string {
  const hash = createHash("sha256")
    .update("early-executable-route-v1\0")
    .update(compilerReleaseVersion()).update("\0")
    .update(compilerImplementationRoot()).update("\0")
    .update(resolve(options.entryPath)).update("\0")
    .update(resolve(options.outDir)).update("\0")
    .update(resolve(options.outPath)).update("\0")
    .update(options.emitIr ? "emit-ir" : "no-ir").update("\0")
    .update(options.sanitize ? "sanitize" : "plain").update("\0")
    .update(options.dynamic ? "dynamic" : "static").update("\0")
    .update(options.backend).update("\0");
  if (options.optimization === "dev") hash.update("optimization-dev\0");
  hash
    .update(options.npmStatic === null
      ? "<npm-static-off>"
      : options.npmStatic === "auto"
        ? "<npm-static-auto>"
        : JSON.stringify(options.npmStatic)).update("\0")
    .update(options.target).update("\0")
    .update(options.compiler.join("\x1f")).update("\0")
    .update(options.nativeEnvironment).update("\0")
    .update(options.nodeVersion).update("\0");
  if (options.ffiProfile === null) {
    hash.update("<ffi-off>");
  } else {
    hash
      .update(resolve(options.ffiProfile.path)).update("\0")
      .update(options.ffiProfile.bytes);
  }
  return hash.digest("hex");
}

function routePath(root: string, options: EarlyExecutableRouteOptions): string {
  return join(root, "early-exe-route", routeKey(options));
}

function routeIntegrity(stamp: Omit<EarlyExecutableRouteStamp, "integrity">): string {
  return createHash("sha256")
    .update("early-executable-route-stamp-v1\0")
    .update(JSON.stringify(stamp))
    .digest("hex");
}

function implementationProofPath(root: string, implementation: string): string {
  const install = createHash("sha256")
    .update("early-executable-install-v1\0")
    .update(compilerImplementationRoot())
    .digest("hex");
  return join(root, "early-exe-implementation", install, implementation);
}

function implementationProofIntegrity(
  proof: Omit<EarlyExecutableImplementationProof, "integrity">,
): string {
  return createHash("sha256")
    .update("early-executable-implementation-proof-v1\0")
    .update(JSON.stringify(proof))
    .digest("hex");
}

async function installCacheMetadata(source: string, destination: string): Promise<void> {
  await rename(source, destination).catch(async () => {
    // Windows does not replace an existing destination with rename(). Route
    // and implementation-proof files are republished on every full compile,
    // so use the same replacement fallback as the payload cache below.
    await rm(destination, { force: true });
    await rename(source, destination);
  });
}

function stampPath(root: string, options: EarlyExecutableCacheOptions): string {
  return sharedStampPath(root, "early-exe", cacheKey(options));
}

function stampIntegrity(stamp: Omit<EarlyExecutableCacheStamp, "integrity">): string {
  return sharedStampIntegrity("early-executable-stamp-v1", stamp);
}

function executableFrontendOutputExclusions(
  options: EarlyExecutableCacheOptions,
  backend: "c" | "llvm",
): ReturnType<typeof frontendOutputExclusions> {
  return frontendOutputExclusions(options, backend, "", [options.outPath]);
}

async function fileMatches(
  destination: string,
  expectedDigest: string,
  expectedMode?: number,
): Promise<boolean> {
  try {
    if (expectedMode !== undefined) {
      const info = await stat(destination);
      if (!info.isFile() || (info.mode & 0o777) !== expectedMode) return false;
    }
    return digest(await readFile(destination)) === expectedDigest;
  } catch {
    return false;
  }
}

async function installExecutable(bytes: Uint8Array, destination: string): Promise<void> {
  await mkdir(dirname(destination), { recursive: true });
  const tmp = join(
    dirname(destination),
    `.scriptc-exe-bin-${process.pid}-${Math.random().toString(36).slice(2)}`,
  );
  try {
    await writeFile(tmp, bytes, { mode: 0o600 });
    await chmod(tmp, 0o777 & ~process.umask());
    await rename(tmp, destination);
  } finally {
    await rm(tmp, { force: true }).catch(() => undefined);
  }
}

export async function readEarlyExecutableCache(
  root: string | null,
  options: EarlyExecutableCacheOptions,
): Promise<EarlyExecutableCacheHit | null> {
  if (root === null) return null;
  const path = stampPath(root, options);
  try {
    const stamp = JSON.parse(await readFile(path, "utf8")) as EarlyExecutableCacheStamp;
    const { integrity, ...unsigned } = stamp;
    if (
      stamp.version !== 1 || stamp.key !== cacheKey(options) ||
      !validFrontendInputSnapshot(stamp.frontend) || !validNativeFeatures(stamp.native) ||
      stamp.files?.translationUnit?.name !== "program.tu" ||
      !/^[0-9a-f]{64}$/.test(stamp.files.translationUnit.digest) ||
      (stamp.files.ir !== null && (
        stamp.files.ir?.name !== "program.ir.json" ||
        !/^[0-9a-f]{64}$/.test(stamp.files.ir.digest)
      )) ||
      (stamp.files.executable !== null && (
        stamp.files.executable?.name !== "program.bin" ||
        !/^[0-9a-f]{64}$/.test(stamp.files.executable.digest)
      )) ||
      (stamp.files.executable === null) !== (stamp.nativeDependencies === null) ||
      (stamp.nativeDependencies !== null && !Array.isArray(stamp.nativeDependencies)) ||
      (stamp.files.ir !== null) !== options.emitIr ||
      stampIntegrity(unsigned) !== integrity ||
      !frontendInputsStillMatch(
        stamp.frontend,
        executableFrontendOutputExclusions(options, stamp.native.backend),
      )
    ) return null;

    const directory = dirname(path);
    const [translationUnit, ir, executable] = await Promise.all([
      readCachedFile(
        join(directory, stamp.files.translationUnit.name),
        stamp.files.translationUnit.digest,
      ),
      stamp.files.ir === null
        ? Promise.resolve(null)
        : readCachedFile(join(directory, stamp.files.ir.name), stamp.files.ir.digest),
      stamp.files.executable === null
        ? Promise.resolve(null)
        : readCachedFile(
            join(directory, stamp.files.executable.name),
            stamp.files.executable.digest,
          ),
    ]);
    if (
      translationUnit === null ||
      stamp.files.ir !== null && ir === null ||
      stamp.files.executable !== null && executable === null
    ) return null;

    // Validate the native proof before restoring frontend artifacts: replacing
    // a TU can update its output directory metadata, which is itself part of
    // compileC's same-output dependency snapshot.
    let executableRestored =
      executable !== null && stamp.nativeDependencies !== null &&
      await nativeArtifactDependenciesStillMatch(stamp.nativeDependencies) &&
      // Recheck after hashing every dependency: a concurrent tool/runtime
      // update must not win the window immediately before installation.
      await nativeArtifactDependenciesStillMatch(stamp.nativeDependencies);
    const paths = outputPaths(options, stamp.native.backend);
    if (!(await fileMatches(paths.cPath, stamp.files.translationUnit.digest))) {
      await installBytes(translationUnit, paths.cPath);
    }
    await rm(paths.staleCPath, { force: true });
    if (
      ir !== null && stamp.files.ir !== null &&
      !(await fileMatches(paths.irPath, stamp.files.ir.digest))
    ) await installBytes(ir, paths.irPath);
    if (executableRestored) {
      try {
        const expectedMode = 0o777 & ~process.umask();
        if (!(await fileMatches(options.outPath, stamp.files.executable!.digest, expectedMode))) {
          await installExecutable(executable!, options.outPath);
        }
      } catch {
        executableRestored = false;
      }
    }
    const now = new Date();
    await Promise.all([
      path,
      join(directory, stamp.files.translationUnit.name),
      ...(stamp.files.ir === null ? [] : [join(directory, stamp.files.ir.name)]),
      ...(stamp.files.executable === null ? [] : [join(directory, stamp.files.executable.name)]),
    ].map((cachePath) => utimes(cachePath, now, now).catch(() => undefined)));
    return {
      cPath: paths.cPath,
      native: stamp.native,
      executableRestored,
      frontend: stamp.frontend,
      ...(ir === null ? {} : { irPath: paths.irPath }),
    };
  } catch {
    return null;
  }
}

/** Follow the exact-invocation route without hashing/importing the complete
 * compiler package. The full compiler publishes a content digest plus a
 * metadata replay proof; any implementation change turns this into a miss. */
export async function readRoutedExecutableCache(
  root: string | null,
  options: EarlyExecutableRouteOptions,
): Promise<EarlyExecutableCacheHit | null> {
  if (root === null) return null;
  try {
    const routeFile = routePath(root, options);
    const route = JSON.parse(
      await readFile(routeFile, "utf8"),
    ) as EarlyExecutableRouteStamp;
    const { integrity, ...unsigned } = route;
    if (
      route.version !== 1 ||
      !/^[0-9a-f]{64}$/.test(route.key) ||
      !/^[0-9a-f]{64}$/.test(route.implementation) ||
      routeIntegrity(unsigned) !== integrity
    ) return null;
    const proofFile = implementationProofPath(root, route.implementation);
    const proof = JSON.parse(await readFile(proofFile, "utf8")) as EarlyExecutableImplementationProof;
    const { integrity: proofIntegrity, ...proofUnsigned } = proof;
    if (
      proof.version !== 1 || proof.implementation !== route.implementation ||
      !Array.isArray(proof.dependencies) ||
      implementationProofIntegrity(proofUnsigned) !== proofIntegrity ||
      !(await compilerImplementationDependenciesStillMatch(proof.dependencies))
    ) return null;
    const complete: EarlyExecutableCacheOptions = {
      ...options,
      implementation: route.implementation,
      implementationDependencies: proof.dependencies,
    };
    if (cacheKey(complete) !== route.key) return null;
    const hit = await readEarlyExecutableCache(root, complete);
    if (hit?.executableRestored !== true) return null;
    const now = new Date();
    await Promise.all([
      routeFile,
      proofFile,
    ].map((cachePath) => utimes(cachePath, now, now).catch(() => undefined)));
    return hit;
  } catch {
    return null;
  }
}

/** Publish the lightweight lookup metadata for an already-validated payload.
 * Full-compiler cache hits call this as a repair path: route/proof files can be
 * evicted independently of the larger executable entry, and one fallback
 * lookup should make later CLI invocations lightweight again. */
export async function publishEarlyExecutableRoute(
  root: string | null,
  options: EarlyExecutableCacheOptions,
): Promise<void> {
  if (root === null) return;
  const proofDestination = implementationProofPath(root, options.implementation);
  const proofUnsigned: Omit<EarlyExecutableImplementationProof, "integrity"> = {
    version: 1,
    implementation: options.implementation,
    dependencies: options.implementationDependencies,
  };
  const proof: EarlyExecutableImplementationProof = {
    ...proofUnsigned,
    integrity: implementationProofIntegrity(proofUnsigned),
  };
  await mkdir(dirname(proofDestination), { recursive: true, mode: 0o700 });
  const proofTmp = `${proofDestination}.tmp-${process.pid}-${Math.random().toString(36).slice(2)}`;
  try {
    await writeFile(proofTmp, `${JSON.stringify(proof)}\n`, { mode: 0o600 });
    await installCacheMetadata(proofTmp, proofDestination);
  } finally {
    await rm(proofTmp, { force: true }).catch(() => undefined);
  }

  const routeOptions: EarlyExecutableRouteOptions = options;
  const routeDestination = routePath(root, routeOptions);
  const routeUnsigned: Omit<EarlyExecutableRouteStamp, "integrity"> = {
    version: 1,
    key: cacheKey(options),
    implementation: options.implementation,
  };
  const route: EarlyExecutableRouteStamp = {
    ...routeUnsigned,
    integrity: routeIntegrity(routeUnsigned),
  };
  await mkdir(dirname(routeDestination), { recursive: true, mode: 0o700 });
  const routeTmp = `${routeDestination}.tmp-${process.pid}-${Math.random().toString(36).slice(2)}`;
  try {
    await writeFile(routeTmp, `${JSON.stringify(route)}\n`, { mode: 0o600 });
    await installCacheMetadata(routeTmp, routeDestination);
  } finally {
    await rm(routeTmp, { force: true }).catch(() => undefined);
  }
}

export async function publishEarlyExecutableCache(
  root: string | null,
  options: EarlyExecutableCacheOptions,
  result: EarlyExecutableCachePublish,
): Promise<void> {
  if (root === null || !result.frontend.stable) return;
  const destination = dirname(stampPath(root, options));
  const parent = dirname(destination);
  const stage = join(
    parent,
    `.tmp-${basename(destination).slice(0, 12)}-${process.pid}-${Math.random().toString(36).slice(2)}`,
  );
  try {
    await mkdir(stage, { recursive: true, mode: 0o700 });
    const publishFile = async (source: string, name: string): Promise<CachedExecutableFile> => {
      const target = join(stage, name);
      await copyFile(source, target);
      await chmod(target, 0o600);
      return { name, digest: digest(await readFile(target)) };
    };
    const publishExecutable =
      result.nativeDependencies === undefined || !result.executableRestored
        ? Promise.resolve(null)
        : publishFile(options.outPath, "program.bin");
    const [translationUnit, ir, executable] = await Promise.all([
      publishFile(result.cPath, "program.tu"),
      result.irPath === undefined
        ? Promise.resolve(null)
        : publishFile(result.irPath, "program.ir.json"),
      publishExecutable,
    ]);
    if (!frontendInputsStillMatch(
      result.frontend,
      executableFrontendOutputExclusions(options, result.native.backend),
    )) return;
    const unsigned: Omit<EarlyExecutableCacheStamp, "integrity"> = {
      version: 1,
      key: cacheKey(options),
      frontend: result.frontend,
      files: { translationUnit, ir, executable },
      nativeDependencies: executable === null ? null : result.nativeDependencies!,
      native: result.native,
    };
    const stamp: EarlyExecutableCacheStamp = { ...unsigned, integrity: stampIntegrity(unsigned) };
    await writeFile(join(stage, "stamp.json"), `${JSON.stringify(stamp)}\n`, { mode: 0o600 });
    await mkdir(destination, { recursive: true, mode: 0o700 });
    const install = async (name: string): Promise<void> => {
      const source = join(stage, name);
      const target = join(destination, name);
      await rename(source, target).catch(async () => {
        await rm(target, { force: true });
        await rename(source, target);
      });
    };
    await install(translationUnit.name);
    if (ir !== null) await install(ir.name);
    if (executable !== null) await install(executable.name);
    await install("stamp.json");
    await publishEarlyExecutableRoute(root, options);
  } finally {
    await rm(stage, { recursive: true, force: true }).catch(() => undefined);
  }
}