import type {
  PrimaryCompletionReceiptSupervisor,
  PrimaryCompletionReceiptSupervisorOptions,
  PrimaryCompletionReceiptSupervisorSummary,
} from './primaryCompletionReceiptSupervisor';
import type { PrimaryRunRecoveryCursor } from '../ports/primaryRunRecoverySource';

export const MIN_COMPLETION_RECEIPT_INTERVAL_MS = 250;
export const MAX_COMPLETION_RECEIPT_INTERVAL_MS = 24 * 60 * 60 * 1_000;
export const MAX_COMPLETION_RECEIPT_INITIAL_DELAY_MS = 24 * 60 * 60 * 1_000;
export const MAX_COMPLETION_RECEIPT_STOP_TIMEOUT_MS = 60_000;

interface ScheduledTimer {
  unref?: () => void;
}

export interface CompletionReceiptLifecycleScheduler {
  setTimeout(callback: () => void, delayMs: number): ScheduledTimer;
  clearTimeout(timer: ScheduledTimer): void;
}

export interface PrimaryCompletionReceiptLifecycleOptions {
  intervalMs: number;
  initialDelayMs?: number;
  stopTimeoutMs?: number;
  cycle?: PrimaryCompletionReceiptSupervisorOptions;
  scheduler?: CompletionReceiptLifecycleScheduler;
  onCycle?: (summary: PrimaryCompletionReceiptSupervisorSummary) => void;
  onError?: (error: unknown) => void;
}

export type PrimaryCompletionReceiptStopResult = 'drained' | 'timed_out';

const defaultScheduler: CompletionReceiptLifecycleScheduler = {
  setTimeout(callback, delayMs) {
    return setTimeout(callback, delayMs);
  },
  clearTimeout(timer) {
    clearTimeout(timer as ReturnType<typeof setTimeout>);
  },
};

function assertIntegerBetween(
  name: string,
  value: number,
  minimum: number,
  maximum: number,
): void {
  if (!Number.isSafeInteger(value) || value < minimum || value > maximum) {
    throw new RangeError(`${name} must be between ${minimum} and ${maximum}`);
  }
}

/** Explicit, non-overlapping receipt polling for small edge deployments. */
export class PrimaryCompletionReceiptLifecycle {
  private readonly intervalMs: number;
  private readonly initialDelayMs: number;
  private readonly stopTimeoutMs: number;
  private readonly cycleOptions: Omit<
    PrimaryCompletionReceiptSupervisorOptions,
    'cursor'
  >;
  private readonly scheduler: CompletionReceiptLifecycleScheduler;
  private readonly onCycle?: (
    summary: PrimaryCompletionReceiptSupervisorSummary,
  ) => void;
  private readonly onError?: (error: unknown) => void;
  private started = false;
  private timer?: ScheduledTimer;
  private inFlight?: Promise<void>;
  private resumeCursor?: PrimaryRunRecoveryCursor;

  constructor(
    private readonly supervisor: Pick<
      PrimaryCompletionReceiptSupervisor,
      'run'
    >,
    options: PrimaryCompletionReceiptLifecycleOptions,
  ) {
    this.intervalMs = options.intervalMs;
    this.initialDelayMs = options.initialDelayMs ?? 0;
    this.stopTimeoutMs = options.stopTimeoutMs ?? 5_000;
    this.cycleOptions = {
      ...(options.cycle?.pageSize === undefined
        ? {}
        : { pageSize: options.cycle.pageSize }),
      ...(options.cycle?.maxPages === undefined
        ? {}
        : { maxPages: options.cycle.maxPages }),
    };
    this.resumeCursor =
      options.cycle?.cursor === undefined
        ? undefined
        : { ...options.cycle.cursor };
    this.scheduler = options.scheduler ?? defaultScheduler;
    this.onCycle = options.onCycle;
    this.onError = options.onError;
    assertIntegerBetween(
      'intervalMs',
      this.intervalMs,
      MIN_COMPLETION_RECEIPT_INTERVAL_MS,
      MAX_COMPLETION_RECEIPT_INTERVAL_MS,
    );
    assertIntegerBetween(
      'initialDelayMs',
      this.initialDelayMs,
      0,
      MAX_COMPLETION_RECEIPT_INITIAL_DELAY_MS,
    );
    assertIntegerBetween(
      'stopTimeoutMs',
      this.stopTimeoutMs,
      1,
      MAX_COMPLETION_RECEIPT_STOP_TIMEOUT_MS,
    );
  }

  start(): boolean {
    if (this.started || this.inFlight) return false;
    this.started = true;
    this.schedule(this.initialDelayMs);
    return true;
  }

  async stop(): Promise<PrimaryCompletionReceiptStopResult> {
    this.started = false;
    if (this.timer) {
      this.scheduler.clearTimeout(this.timer);
      this.timer = undefined;
    }
    const inFlight = this.inFlight;
    if (!inFlight) return 'drained';

    let timeout: ReturnType<typeof setTimeout> | undefined;
    const result = await Promise.race<PrimaryCompletionReceiptStopResult>([
      inFlight.then(() => 'drained' as const),
      new Promise<'timed_out'>((resolve) => {
        timeout = setTimeout(() => resolve('timed_out'), this.stopTimeoutMs);
      }),
    ]);
    if (timeout) clearTimeout(timeout);
    return result;
  }

  private schedule(delayMs: number): void {
    if (!this.started || this.timer) return;
    const timer = this.scheduler.setTimeout(() => {
      if (this.timer === timer) this.timer = undefined;
      this.run();
    }, delayMs);
    this.timer = timer;
    timer.unref?.();
  }

  private run(): void {
    if (!this.started || this.inFlight) return;
    const inFlight = this.supervisor
      .run({
        ...this.cycleOptions,
        ...(this.resumeCursor === undefined
          ? {}
          : { cursor: { ...this.resumeCursor } }),
      })
      .then((summary) => {
        this.resumeCursor =
          summary.remaining && summary.nextCursor
            ? { ...summary.nextCursor }
            : undefined;
        this.notifyCycle(summary);
      })
      .catch((error) => this.notifyError(error))
      .then(() => undefined)
      .finally(() => {
        if (this.inFlight === inFlight) this.inFlight = undefined;
        if (this.started) this.schedule(this.intervalMs);
      });
    this.inFlight = inFlight;
  }

  private notifyCycle(
    summary: PrimaryCompletionReceiptSupervisorSummary,
  ): void {
    try {
      this.onCycle?.(summary);
    } catch (error) {
      this.notifyError(error);
    }
  }

  private notifyError(error: unknown): void {
    try {
      this.onError?.(error);
    } catch {
      // Diagnostics must never create another scheduler failure loop.
    }
  }
}