import { createHash } from "node:crypto";
import { constants, type BigIntStats } from "node:fs";
import { lstat, open, type FileHandle } from "node:fs/promises";
import { basename, join } from "node:path";
import type { BinaryTarget } from "../domain/binaryTargetTypes.js";
import type { InspectSignature } from "../domain/native/nativeInspection.js";
import {
  assertRegularFileActive,
  RegularFileOperationCancelled,
} from "../filesystem/RegularFile.js";
import { AnalysisError } from "../domain/analysisErrorBase.js";
import {
  AnalysisAccessDeniedError,
  AnalysisArtifactChangedError,
  AnalysisCancelledError,
  AnalysisOutputError,
  AnalysisResourceConstraintError,
} from "../domain/analysisErrorCore.js";
import { ProviderAdapterError } from "../domain/providerAdapterError.js";
import { ProviderCleanupError } from "../domain/providerCleanupError.js";
import { analysisErrorWithCleanupFailure } from "../domain/analysisErrorCleanup.js";
import { err, ok, type Result } from "../domain/result.js";
import { OwnedFileHandle } from "../filesystem/OwnedFileHandle.js";
import { ArtifactResourceScope } from "../artifacts/ArtifactResourceScope.js";
import { PrivateRuntimeRoot } from "../process/PrivateRuntimeRoot.js";
import { ArtifactReaderFailure } from "../artifacts/ArtifactReader.js";
import {
  AnalysisCleanupLease,
  AnalysisCleanupLeaseGroup,
} from "../artifacts/AnalysisCleanupLease.js";
import { bindArtifactFileCleanup } from "../artifacts/ArtifactFileOperation.js";
import type { ArtifactResourceOwner } from "../artifacts/ArtifactResourceScope.js";

import { NATIVE_MACOS_PROVIDER_IDENTITY } from "./NativeMacOSProviderMetadata.js";

type SignatureOwner = Extract<
  ArtifactResourceOwner,
  { readonly kind: "lease" }
> & {
  readonly lease: AnalysisCleanupLease;
};

/** Binding of commands to the selected executable's registered content/version. */
export interface SignatureTargetBinding {
  readonly identity: string;
  readonly snapshotPath: string;
  readonly snapshotIdentity: string;
}

const identity = (stat: BigIntStats): string =>
  [stat.dev, stat.ino, stat.size, stat.mtimeNs, stat.ctimeNs].join(":");

const changedTarget = (target: BinaryTarget, reason: string) =>
  err(
    new AnalysisArtifactChangedError("inspect_signature", target.path, reason),
  );

const signatureReadFailure = (
  target: BinaryTarget,
  cause: unknown,
): AnalysisError => {
  if (cause instanceof RegularFileOperationCancelled)
    return new AnalysisCancelledError("inspect_signature", {
      cause: cause.reason,
    });
  if (cause instanceof AnalysisError) return cause;
  const code =
    cause instanceof Error && "code" in cause ? cause.code : undefined;
  if (code === "EACCES" || code === "EPERM")
    return new AnalysisAccessDeniedError(
      "inspect_signature",
      target.path,
      code,
      { cause },
    );
  if (code === "ENOENT" || code === "ENOTDIR" || code === "ELOOP")
    return new AnalysisArtifactChangedError(
      "inspect_signature",
      target.path,
      `Registered signature target is no longer readable (${code}): ${target.path}`,
      { cause },
    );
  return new ProviderAdapterError(
    NATIVE_MACOS_PROVIDER_IDENTITY.id,
    "inspect_signature",
    {
      cause,
      diagnostics: {
        path: target.path,
        phase: "target-version-binding",
        system_code: typeof code === "string" ? code : null,
        reason: cause instanceof Error ? cause.message : String(cause),
      },
    },
  );
};

/** Inspect a digest-verified private copy, releasing it on every exit path. */
export const withSignatureTarget = async (
  target: BinaryTarget,
  resources: ArtifactResourceScope,
  inspect: (
    binding: SignatureTargetBinding,
  ) => Promise<Result<InspectSignature, AnalysisError>>,
  signal?: AbortSignal,
  createRoot: () => Promise<Pick<PrivateRuntimeRoot, "path" | "close">> = () =>
    PrivateRuntimeRoot.create({ prefix: "rea-signature-" }),
): Promise<Result<InspectSignature, AnalysisError>> => {
  try {
    return await resources.run(async () => {
      let root: Pick<PrivateRuntimeRoot, "path" | "close">;
      try {
        assertRegularFileActive(signal);
        root = await createRoot();
      } catch (cause: unknown) {
        return err(
          cause instanceof RegularFileOperationCancelled
            ? signatureReadFailure(target, cause)
            : snapshotFailure(target, "create", cause),
        );
      }
      const children = new ArtifactResourceScope();
      const owner: SignatureOwner = {
        kind: "lease",
        lease: new AnalysisCleanupLease(
          async () => {
            await children.close();
            await root.close();
          },
          {
            get cleanupResources() {
              return [...children.cleanupResources, root.path];
            },
          },
        ),
        resource: root.path,
      };
      let result: Result<InspectSignature, AnalysisError>;
      try {
        const binding = await bindSignatureTarget(
          target,
          join(root.path, basename(target.path)),
          children,
          signal,
        );
        if (!binding.ok) result = binding;
        else {
          try {
            result = await inspect(binding.value);
          } catch (cause: unknown) {
            result = err(
              new AnalysisOutputError(
                "inspect_signature",
                "Native output parsing failed",
                { cause },
              ),
            );
          }
        }
      } catch (cause: unknown) {
        result = err(signatureReadFailure(target, cause));
      }
      const cleanup = await resources.release(owner);
      if (result.ok && signal?.aborted)
        result = err(
          new AnalysisCancelledError("inspect_signature", {
            cause: signal.reason,
            partialObservation: result.value,
          }),
        );
      if (cleanup.kind === "failed") {
        const failure = signatureCleanupFailure(
          target,
          [root.path],
          cleanup.cause,
          "cleanup",
        );
        new AnalysisCleanupLeaseGroup(failure, [owner.lease]);
        return combineCleanupFailure(result, failure);
      }
      return result;
    });
  } catch (cause: unknown) {
    const retained =
      cause instanceof ArtifactReaderFailure && cause.cleanup !== undefined
        ? cause.cleanup
        : undefined;
    if (retained !== undefined) {
      const failure = signatureCleanupFailure(
        target,
        retained.resources,
        cause,
        "retry",
      );
      bindArtifactFileCleanup(cause, failure);
      return combineCleanupFailure(
        err(signatureReadFailure(target, cause)),
        failure,
      );
    }
    return err(signatureReadFailure(target, cause));
  }
};

/** Each composed error follows the exact primary and secondary cleanup owners. */
const combineCleanupFailure = <T>(
  primary: Result<T, AnalysisError>,
  cleanup: AnalysisError,
): Result<T, AnalysisError> =>
  primary.ok
    ? err(cleanup)
    : err(
        analysisErrorWithCleanupFailure(
          primary.error,
          cleanup,
          "inspect_signature",
        ).bindCleanupDependencies([primary.error, cleanup]),
      );

const signatureCleanupFailure = (
  target: BinaryTarget,
  resources: readonly string[],
  cause: unknown,
  phase: string,
): AnalysisError =>
  new ProviderCleanupError(
    NATIVE_MACOS_PROVIDER_IDENTITY.id,
    resources,
    {
      reason: cause instanceof Error ? cause.message : String(cause),
      phase: `signature-snapshot-${phase}`,
      path: target.path,
    },
    { operation: "inspect_signature", cause },
  );

const snapshotFailure = (
  target: BinaryTarget,
  phase: string,
  cause: unknown,
): AnalysisError =>
  new ProviderAdapterError(
    NATIVE_MACOS_PROVIDER_IDENTITY.id,
    "inspect_signature",
    {
      cause,
      diagnostics: {
        path: target.path,
        phase: `signature-snapshot-${phase}`,
        reason: cause instanceof Error ? cause.message : String(cause),
      },
    },
  );

const snapshotIO = async <T>(
  target: BinaryTarget,
  phase: string,
  operation: () => Promise<T>,
): Promise<T> => {
  try {
    return await operation();
  } catch (cause: unknown) {
    throw snapshotFailure(target, phase, cause);
  }
};

const copySignatureBytes = async (
  target: BinaryTarget,
  source: { readonly file: FileHandle; readonly stat: BigIntStats },
  snapshot: FileHandle,
  signal?: AbortSignal,
): Promise<string> => {
  const size = Number(source.stat.size);
  if (!Number.isSafeInteger(size))
    throw new AnalysisResourceConstraintError(
      "inspect_signature",
      "file-size",
      `Signature target size is not exactly representable: ${target.path}`,
      null,
    );
  const hash = createHash("sha256");
  const chunk = Buffer.alloc(64 * 1024);
  let position = 0;
  while (position < size) {
    assertRegularFileActive(signal);
    const { bytesRead } = await source.file.read(
      chunk,
      0,
      Math.min(chunk.length, size - position),
      position,
    );
    assertRegularFileActive(signal);
    if (bytesRead === 0)
      throw new AnalysisArtifactChangedError(
        "inspect_signature",
        target.path,
        `Signature target was truncated while hashing: ${target.path}`,
      );
    const bytes = chunk.subarray(0, bytesRead);
    hash.update(bytes);
    // writeFile retries short writes; memory remains bounded to this chunk.
    await snapshotIO(target, "write", () => snapshot.writeFile(bytes));
    position += bytesRead;
  }
  return hash.digest("hex");
};

/** Hash and copy the same descriptor bytes, without reopening the mutable path. */
const bindSignatureTarget = async (
  target: BinaryTarget,
  snapshotPath: string,
  resources: ArtifactResourceScope,
  signal?: AbortSignal,
): Promise<Result<SignatureTargetBinding, AnalysisError>> => {
  let sourceOwner: SignatureOwner | undefined;
  let snapshotOwner: SignatureOwner | undefined;
  const perform = async (): Promise<
    Result<SignatureTargetBinding, AnalysisError>
  > => {
    try {
      assertRegularFileActive(signal);
      const before = await lstat(target.path, { bigint: true });
      assertRegularFileActive(signal);
      if (!before.isFile() || before.isSymbolicLink())
        return changedTarget(
          target,
          `Signature target is no longer a regular file: ${target.path}`,
        );
      const file = await open(
        target.path,
        constants.O_RDONLY | constants.O_NOFOLLOW | constants.O_NONBLOCK,
      );
      const sourceHandle = new OwnedFileHandle(file);
      sourceOwner = {
        kind: "lease",
        resource: target.path,
        lease: new AnalysisCleanupLease(
          () => sourceHandle.close(),
          [target.path],
        ),
      };
      const opened = await file.stat({ bigint: true });
      assertRegularFileActive(signal);
      if (identity(opened) !== identity(before))
        return changedTarget(
          target,
          `Signature target changed before open: ${target.path}`,
        );
      const snapshot = await snapshotIO(target, "create-file", () =>
        open(snapshotPath, "wx", 0o600),
      );
      const snapshotHandle = new OwnedFileHandle(snapshot);
      snapshotOwner = {
        kind: "lease",
        resource: snapshotPath,
        lease: new AnalysisCleanupLease(
          () => snapshotHandle.close(),
          [snapshotPath],
        ),
      };
      const observed = await copySignatureBytes(
        target,
        { file, stat: opened },
        snapshot,
        signal,
      );
      if (observed !== target.sha256)
        return changedTarget(
          target,
          `Signature target digest changed: ${target.path}; expected ${target.sha256}, observed ${observed}`,
        );
      const after = await file.stat({ bigint: true });
      const current = await lstat(target.path, { bigint: true });
      assertRegularFileActive(signal);
      if (
        identity(after) !== identity(opened) ||
        identity(current) !== identity(opened)
      )
        return changedTarget(
          target,
          `Signature target changed while establishing its version: ${target.path}`,
        );
      await snapshotIO(target, "seal", () => snapshot.chmod(0o400));
      const snapshotOpened = await snapshot.stat({ bigint: true });
      const snapshotAtPath = await lstat(snapshotPath, { bigint: true });
      if (
        !snapshotOpened.isFile() ||
        !snapshotAtPath.isFile() ||
        snapshotAtPath.isSymbolicLink() ||
        identity(snapshotOpened) !== identity(snapshotAtPath)
      )
        return changedTarget(
          target,
          `Digest-verified signature snapshot changed while binding: ${target.path}`,
        );
      return ok({
        identity: identity(opened),
        snapshotPath,
        snapshotIdentity: identity(snapshotOpened),
      });
    } catch (cause: unknown) {
      return err(signatureReadFailure(target, cause));
    }
  };
  let result = await perform();
  const cleanupFailures: {
    readonly owner: SignatureOwner;
    readonly cause: unknown;
  }[] = [];
  for (const owner of [snapshotOwner, sourceOwner]) {
    if (owner === undefined) continue;
    const cleanup = await resources.release(owner);
    if (cleanup.kind === "failed")
      cleanupFailures.push({ owner, cause: cleanup.cause });
  }
  if (result.ok && signal?.aborted)
    result = err(
      new AnalysisCancelledError("inspect_signature", {
        cause: signal.reason,
        diagnostics: {
          snapshot_binding: {
            identity: result.value.identity,
            snapshot_path: result.value.snapshotPath,
          },
        },
      }),
    );
  if (cleanupFailures.length > 0) {
    const cause = new AggregateError(
      cleanupFailures.map(({ cause: failure }) => failure),
      "Signature snapshot file handles could not be closed",
    );
    const cleanup = signatureCleanupFailure(
      target,
      cleanupFailures.map(({ owner }) => owner.resource),
      cause,
      "close",
    );
    new AnalysisCleanupLeaseGroup(
      cleanup,
      cleanupFailures.map(({ owner }) => owner.lease),
    );
    result = combineCleanupFailure(result, cleanup);
  }
  return result;
};

/** Reject target drift across signature command captures. */
export const verifySignatureTarget = async (
  target: BinaryTarget,
  binding: SignatureTargetBinding,
  signal?: AbortSignal,
): Promise<Result<void, AnalysisError>> => {
  try {
    assertRegularFileActive(signal);
    const current = await lstat(target.path, { bigint: true });
    assertRegularFileActive(signal);
    if (!current.isFile() || identity(current) !== binding.identity)
      return changedTarget(
        target,
        `Signature target changed during inspection: ${target.path}`,
      );
    let snapshot: BigIntStats;
    try {
      snapshot = await lstat(binding.snapshotPath, { bigint: true });
    } catch (cause: unknown) {
      const code =
        cause instanceof Error && "code" in cause ? cause.code : undefined;
      if (code === "ENOENT" || code === "ENOTDIR" || code === "ELOOP")
        return changedTarget(
          target,
          `Digest-verified signature snapshot is unavailable during inspection: ${target.path}`,
        );
      return err(signatureReadFailure(target, cause));
    }
    assertRegularFileActive(signal);
    return snapshot.isFile() &&
      !snapshot.isSymbolicLink() &&
      identity(snapshot) === binding.snapshotIdentity
      ? ok(undefined)
      : changedTarget(
          target,
          `Digest-verified signature snapshot changed during inspection: ${target.path}`,
        );
  } catch (cause: unknown) {
    return err(signatureReadFailure(target, cause));
  }
};