import {
  prepareProcessOwnershipInspection,
  systemProcessOwnershipHost,
} from "./ProcessOwnershipObservation.js";
import { DarwinProcessOwnershipInspectionError } from "./DarwinProcessRunTokenReader.js";
import type { Readable, Writable } from "node:stream";
import { pipeline } from "node:stream/promises";

import type {
  OwnedProviderProcessSpawnOptions,
  ProviderProcessSnapshot,
  ProviderProcessStopResult,
  SpawnedOwnedProviderProcess,
} from "./ProviderProcess.js";
import {
  ProviderProcessSupervisor,
  spawnOwnedProviderProcess,
} from "./ProviderProcess.js";
import {
  cleanupOwnedProcessGroup,
  type OwnedProcessGroup,
  type ProcessCleanupFailure,
} from "./ProcessOwnership.js";
import { ABORTED, waitForAbortable } from "./AbortablePromise.js";
import {
  ProviderStartupDeadline,
  waitForAbortableDelay,
} from "./ProviderDeadline.js";

/** A short-lived command failed its lifecycle or complete-output contract. */
export class OwnedCommandFailure extends Error {
  readonly #cancellation: { readonly reason: unknown } | undefined;

  /** Opaque caller reason observed by the owner, distinct from physical causes. */
  get cancellation(): { readonly reason: unknown } | undefined {
    return this.#cancellation;
  }
  readonly processError: Error | undefined;
  readonly cleanupResult: ProcessCleanupFailure | undefined;
  readonly collectionFailure: boolean;
  readonly preparationFailure:
    | DarwinProcessOwnershipInspectionError
    | undefined;

  constructor(
    readonly reason: "cancelled" | "timeout" | "output-limit" | "process",
    message: string,
    readonly snapshot: ProviderProcessSnapshot | null = null,
    readonly cleanupFailure: string | null = null,
    options?: ErrorOptions & {
      readonly cancellation?: { readonly reason: unknown } | undefined;
      readonly processError?: Error | undefined;
      readonly cleanupResult?: ProcessCleanupFailure;
      readonly collectionFailure?: boolean;
      readonly preparationFailure?: DarwinProcessOwnershipInspectionError;
    },
    readonly resources: readonly string[] = [],
    readonly cleanupOwner?: ProviderProcessSupervisor,
  ) {
    super(message, options);
    this.#cancellation =
      options?.cancellation === undefined
        ? undefined
        : { reason: options.cancellation.reason };
    this.processError = options?.processError;
    this.cleanupResult = options?.cleanupResult;
    this.collectionFailure = options?.collectionFailure ?? false;
    this.preparationFailure = options?.preparationFailure;
  }
}

/** Report recorded launch identities; these labels do not authorize signaling. */
export const ownedCommandResources = (
  ownership: OwnedProcessGroup,
  directory?: string,
): readonly string[] => [
  ownership.runId,
  ...(directory === undefined ? [] : [directory]),
  `pid:${ownership.leaderPid}`,
  `process-group:${ownership.processGroupId}`,
];

/** Output handling for one owned command. */
interface OwnedCommandLimits {
  /** Retained stderr bytes, plus stdout bytes unless a sink consumes stdout. */
  readonly diagnosticBytes: number;
  /** Accept an ordinary nonzero exit after output closes without other process errors. */
  readonly acceptNonZeroExit?: boolean;
  /** Interpret complete physical output synchronously before awaited final cleanup. */
  readonly observeCompleted?: (snapshot: ProviderProcessSnapshot) => void;
  /**
   * Receives stdout instead of the retained snapshot, for output parsed as it
   * arrives. The command completes only after the sink finishes. The sink
   * records its own rejections and keeps accepting, so the command's outcome
   * stays authoritative; a failing stream is a collection failure.
   */
  readonly stdout?: Writable;
}

/** Keep independently bounded macOS helper compilation outside a short command deadline.
 * Other platforms still prepare inside runOwnedCommand: Linux ps has no separate deadline.
 */
export const prepareOwnedCommand = async (
  signal?: AbortSignal,
): Promise<void> => {
  if (systemProcessOwnershipHost.platform !== "darwin") return;
  try {
    signal?.throwIfAborted();
    await prepareProcessOwnershipInspection(signal);
  } catch (cause: unknown) {
    throwCommandPreparationFailure(
      cause,
      signal,
      signal?.aborted === true ? "cancelled" : undefined,
    );
  }
};

/** Both preparation stages preserve physical failures, opaque cancellation and exact owners. */
function throwCommandPreparationFailure(
  cause: unknown,
  signal: AbortSignal | undefined,
  interruption: "cancelled" | "timeout" | undefined,
): never {
  // A caller's raw abort reason remains opaque even if it is a typed error.
  const preparationFailure =
    cause instanceof DarwinProcessOwnershipInspectionError &&
    !(signal?.aborted === true && cause === signal.reason)
      ? cause
      : undefined;
  // Preparation owns its physical outcome and any retained helper resources.
  if (
    preparationFailure !== undefined &&
    preparationFailure.cancellation === undefined
  )
    throw preparationFailure;
  if (interruption !== undefined)
    throw new OwnedCommandFailure(
      interruption,
      interruption === "cancelled"
        ? "Command cancelled during ownership preparation."
        : "Command deadline elapsed during ownership preparation.",
      null,
      null,
      {
        cause,
        ...(interruption === "cancelled"
          ? {
              cancellation: { reason: signal?.reason },
            }
          : {}),
        ...(preparationFailure === undefined ? {} : { preparationFailure }),
      },
    );
  throw cause;
}

/** Execute a single owned process with independent cleanup and bounded diagnostic retention. */
export const runOwnedCommand = async (
  spawn: OwnedProviderProcessSpawnOptions,
  limits: OwnedCommandLimits & { readonly timeoutMs: number },
  options: {
    readonly signal?: AbortSignal | undefined;
    /** Synchronously accept unresolved cleanup ownership; execution still returns its original outcome. Must not throw. */
    readonly retainCleanup?: (
      owner: ProviderProcessSupervisor,
      result: Extract<ProviderProcessStopResult, { status: "incomplete" }>,
    ) => void;
    readonly launcher?: (
      input: OwnedProviderProcessSpawnOptions,
    ) => Promise<SpawnedOwnedProviderProcess>;
  } = {},
): Promise<ProviderProcessSnapshot> => {
  const callerSignal = options.signal ?? spawn.signal;
  if (callerSignal?.aborted)
    throw new OwnedCommandFailure(
      "cancelled",
      "Command cancelled before launch.",
      null,
      null,
      { cancellation: { reason: callerSignal.reason } },
    );
  const deadline = new ProviderStartupDeadline(limits.timeoutMs, callerSignal);
  try {
    return await collectOwnedCommand(
      spawn,
      limits,
      options.launcher ?? spawnOwnedProviderProcess,
      deadline,
      callerSignal,
      options.retainCleanup,
    );
  } finally {
    deadline.dispose();
  }
};

const collectOwnedCommand = async (
  spawn: OwnedProviderProcessSpawnOptions,
  limits: OwnedCommandLimits,
  launcher: (
    input: OwnedProviderProcessSpawnOptions,
  ) => Promise<SpawnedOwnedProviderProcess>,
  deadline: ProviderStartupDeadline,
  callerSignal?: AbortSignal,
  retainCleanup?: (
    owner: ProviderProcessSupervisor,
    result: Extract<ProviderProcessStopResult, { status: "incomplete" }>,
  ) => void,
): Promise<ProviderProcessSnapshot> => {
  const signal = deadline.signal;
  let launched: SpawnedOwnedProviderProcess;
  try {
    launched = await launcher({
      ...spawn,
      signal,
    });
  } catch (cause: unknown) {
    throwCommandPreparationFailure(cause, signal, deadline.interruption);
  }
  let exceeded = false;
  let outputLimitObservedBeforeInterruption = false;
  let processFailure: string | undefined;
  let processError: Error | undefined;
  let processFailureBeforeInterruption:
    | {
        readonly message: string;
        readonly processError: Error | undefined;
        readonly collectionFailure: boolean;
      }
    | undefined;
  const supervisor = new ProviderProcessSupervisor(
    {
      ...launched,
      ownsProcessLifetime: true,
      cleanup:
        launched.cleanup ??
        (() => cleanupOwnedProcessGroup(launched.ownership)),
    },
    {
      captureStdout: limits.stdout === undefined,
      maxDiagnosticBytes: limits.diagnosticBytes,
      onDiagnostic: (event) => {
        if (event.type === "output" && event.truncated === true) {
          exceeded = true;
          if (deadline.interruption === undefined)
            outputLimitObservedBeforeInterruption = true;
        }
        if (event.type === "error") {
          processFailure ??= event.message;
          processError ??= event.cause;
          if (deadline.interruption === undefined)
            processFailureBeforeInterruption ??= {
              message: processFailure,
              processError,
              collectionFailure: true,
            };
        }
        if (event.type === "exit" && deadline.interruption === undefined) {
          const acceptedNonzeroExit =
            limits.acceptNonZeroExit === true &&
            event.code !== null &&
            event.code !== 0 &&
            event.signal === null;
          if (
            event.signal !== null ||
            (event.code !== null && event.code !== 0 && !acceptedNonzeroExit)
          )
            processFailureBeforeInterruption ??= {
              message:
                "Command failed; inspect its exit status and diagnostics.",
              processError: undefined,
              collectionFailure: false,
            };
        }
      },
    },
  );
  // A command that fails or is interrupted destroys its sink with its stdout.
  const abandoned = new AbortController();
  const consumed = consumeStdout(
    launched.process.stdout,
    limits.stdout,
    AbortSignal.any([signal, abandoned.signal]),
  );
  void consumed.then((failed) => {
    processFailure ??= failed;
    if (failed !== undefined && deadline.interruption === undefined)
      processFailureBeforeInterruption ??= {
        message: processFailure ?? failed,
        processError,
        collectionFailure: true,
      };
  });
  let failure: OwnedCommandFailure | undefined;
  const throwInterruptionOrObservedFailure = (
    interruption: "cancelled" | "timeout" | undefined,
    snapshot: ProviderProcessSnapshot | null = null,
  ): void => {
    if (interruption === undefined) return;
    if (outputLimitObservedBeforeInterruption)
      throw new OwnedCommandFailure(
        "output-limit",
        "Command diagnostic output exceeded its complete-output budget.",
        snapshot,
      );
    if (processFailureBeforeInterruption !== undefined)
      throw new OwnedCommandFailure(
        "process",
        processFailureBeforeInterruption.message,
        snapshot,
        null,
        {
          processError: processFailureBeforeInterruption.processError,
          collectionFailure: processFailureBeforeInterruption.collectionFailure,
        },
      );
    throw new OwnedCommandFailure(
      interruption,
      interruption === "cancelled"
        ? "Command cancelled."
        : "Command deadline elapsed.",
      snapshot,
      null,
      interruption === "cancelled"
        ? { cancellation: { reason: signal.reason } }
        : undefined,
    );
  };
  try {
    while (!(await supervisor.waitForOutputClose(10))) {
      throwInterruptionOrObservedFailure(deadline.interruption);
      if (exceeded)
        throw new OwnedCommandFailure(
          "output-limit",
          "Command diagnostic output exceeded its complete-output budget.",
        );
      if (processFailure !== undefined)
        throw new OwnedCommandFailure("process", processFailure, null, null, {
          processError,
          collectionFailure: true,
        });
      await waitForAbortableDelay(25, signal);
    }
    // Output has closed, but the sink may still be parsing what it buffered.
    const sinkFailure = await waitForAbortable(consumed, signal);
    if (sinkFailure !== ABORTED) processFailure ??= sinkFailure;
    const snapshot = supervisor.snapshot();
    throwInterruptionOrObservedFailure(deadline.interruption, snapshot);
    if (exceeded)
      throw new OwnedCommandFailure(
        "output-limit",
        "Command diagnostic output exceeded its complete-output budget.",
        snapshot,
      );
    const acceptedNonzeroExit =
      limits.acceptNonZeroExit === true &&
      snapshot.exitCode !== null &&
      snapshot.exitCode !== undefined &&
      snapshot.exitCode !== 0 &&
      snapshot.signal === null;
    if (
      processFailure !== undefined ||
      ((snapshot.exitCode !== 0 || snapshot.signal !== null) &&
        !acceptedNonzeroExit)
    )
      throw new OwnedCommandFailure(
        "process",
        processFailure ??
          "Command failed; inspect its exit status and diagnostics.",
        snapshot,
        null,
        { processError, collectionFailure: processFailure !== undefined },
      );
    limits.observeCompleted?.(snapshot);
  } catch (cause: unknown) {
    failure =
      cause instanceof OwnedCommandFailure
        ? cause
        : new OwnedCommandFailure(
            "process",
            "Command collection failed.",
            null,
            null,
            { cause },
          );
  }
  // A finished sink ignores this; an unfinished one is destroyed.
  abandoned.abort();
  const stopped = await supervisor.stop();
  const snapshot = supervisor.snapshot();
  const cancellation =
    failure?.cancellation ??
    (callerSignal?.aborted ? { reason: callerSignal.reason } : undefined);
  if (stopped.status === "incomplete" && retainCleanup !== undefined)
    retainCleanup(supervisor, stopped);
  else if (stopped.status === "incomplete")
    throw new OwnedCommandFailure(
      failure?.reason ?? "process",
      failure?.message ?? "Command cleanup failed.",
      snapshot,
      stopped.reason,
      {
        cancellation,
        ...(failure === undefined
          ? {}
          : { cause: failure, processError: failure.processError }),
        ...(stopped.cleanupResult === undefined
          ? {}
          : { cleanupResult: stopped.cleanupResult }),
        ...(failure?.collectionFailure === true
          ? { collectionFailure: true }
          : {}),
      },
      ownedCommandResources(launched.ownership, spawn.cwd),
      supervisor,
    );
  if (failure !== undefined)
    throw new OwnedCommandFailure(
      failure.reason,
      failure.message,
      snapshot,
      failure.cleanupFailure,
      {
        cause: failure,
        cancellation,
        processError: failure.processError,
        ...(failure.cleanupResult === undefined
          ? {}
          : { cleanupResult: failure.cleanupResult }),
        ...(failure.collectionFailure ? { collectionFailure: true } : {}),
      },
      failure.resources,
    );
  if (callerSignal?.aborted)
    throw new OwnedCommandFailure(
      "cancelled",
      "Command cancelled.",
      snapshot,
      null,
      {
        cancellation: { reason: callerSignal.reason },
      },
    );
  return snapshot;
};

/**
 * Pipe stdout into its sink until `signal` aborts, which destroys both; settles
 * with a failure message, never rejects.
 */
const consumeStdout = (
  stdout: Readable | null,
  sink: Writable | undefined,
  signal: AbortSignal,
): Promise<string | undefined> => {
  if (sink === undefined) return Promise.resolve(undefined);
  if (stdout === null) {
    sink.destroy();
    return Promise.resolve("stdout stream is unavailable");
  }
  return pipeline(stdout, sink, { signal }).then(
    () => undefined,
    (cause: unknown) =>
      `stdout stream failed: ${cause instanceof Error ? cause.message : String(cause)}`,
  );
};