import type { AnalysisPartialObservation } from "../domain/analysisErrorBase.js";
import {
  AnalysisCancelledError,
  AnalysisTimeoutError,
} from "../domain/analysisErrorCore.js";
import {
  DEFAULT_NATIVE_UI_DEADLINE_MS,
  nativeDeadlineRecovery,
} from "../domain/native/nativeDeadlines.js";

type Interruption =
  | { readonly kind: "caller"; readonly reason: unknown }
  | { readonly kind: "deadline"; readonly reason: unknown };

/** Tracks whether the caller or the owned operation deadline stopped UI work. */
export class NativeUiInterruptionControl {
  readonly signal: AbortSignal;
  #controller = new AbortController();
  #interruption: Interruption | undefined;
  #caller: AbortSignal | undefined;
  #deadline: AbortSignal;
  #deadlineMs: number;
  #onCallerAbort = (): void => {
    this.#interrupt("caller", this.#caller?.reason);
  };
  #onDeadlineAbort = (): void => {
    this.#interrupt("deadline", this.#deadline.reason);
  };

  /** Selected `native_ui_deadline_ms`, including the omitted default. */
  get deadlineMs(): number {
    return this.#deadlineMs;
  }

  constructor(
    caller: AbortSignal | undefined,
    deadline: AbortSignal,
    deadlineMs = DEFAULT_NATIVE_UI_DEADLINE_MS,
  ) {
    this.#caller = caller;
    this.#deadline = deadline;
    this.#deadlineMs = deadlineMs;
    this.signal = this.#controller.signal;

    // Match AbortSignal.any's iterable priority when both are already aborted.
    if (caller?.aborted) this.#interrupt("caller", caller.reason);
    else if (deadline.aborted) this.#interrupt("deadline", deadline.reason);
    else {
      caller?.addEventListener("abort", this.#onCallerAbort, { once: true });
      deadline.addEventListener("abort", this.#onDeadlineAbort, {
        once: true,
      });
    }
  }

  /**
   * A helper subprocess reached the selected deadline before the abort signal
   * settled. Caller cancellation already recorded on this control stays primary.
   */
  deadlineFailure(
    operation: string,
    partialObservation?: AnalysisPartialObservation,
  ): AnalysisTimeoutError | AnalysisCancelledError {
    if (this.#interruption === undefined)
      this.#interrupt("deadline", this.#deadline.reason);
    const error = this.error(operation, partialObservation);
    if (error === undefined)
      throw new Error("UI deadline failure requires an interruption.");
    return error;
  }

  error(
    operation: string,
    partialObservation?: AnalysisPartialObservation,
  ): AnalysisCancelledError | AnalysisTimeoutError | undefined {
    const interruption = this.#interruption;
    if (interruption === undefined) return undefined;
    return interruption.kind === "deadline"
      ? new AnalysisTimeoutError(operation, this.#deadlineMs, {
          cause: interruption.reason,
          partialObservation,
          ...nativeDeadlineRecovery({
            timeoutMs: this.#deadlineMs,
            setting: "native_ui_deadline_ms",
            cliFlag: "--native-ui-deadline-ms",
            defaultMs: DEFAULT_NATIVE_UI_DEADLINE_MS,
            phase: "native UI observation deadline",
            detail: " A partial observation may already be retained.",
            unchanged:
              "The 67108864-byte scenario output allowance and the 180000 ms cap on one wait step have no runtime override.",
          }),
        })
      : new AnalysisCancelledError(operation, {
          cause: interruption.reason,
          partialObservation,
        });
  }

  dispose(): void {
    this.#caller?.removeEventListener("abort", this.#onCallerAbort);
    this.#deadline.removeEventListener("abort", this.#onDeadlineAbort);
  }

  #interrupt(kind: Interruption["kind"], reason: unknown): void {
    if (this.#interruption !== undefined) return;
    this.#interruption = { kind, reason };
    this.#controller.abort(reason);
  }
}