import type {
  SignageJsonValue,
  SignageProviderDiscoveryRequest,
  SignageProviderItemDescriptor,
  SignageProviderRefreshRequest,
  SignageProviderRegistration,
  SignageProviderResolution,
  SignageProviderResolveRequest,
  SignageProviderSourceDescriptor,
} from "../../src/server/providers/contract.js";

/**
 * A **test-only** content provider, standing in for the real modules that do not exist yet.
 *
 * It is not an installed module, it has no manifest, and nothing about it is reachable from a
 * running Signage: it lives under `tests/`, and the only way it enters the system is a test calling
 * the same `register` a real provider module would call from its own `start` hook.
 *
 * The point is to prove the seam with something that behaves like the three real providers will:
 * an announcements-shaped provider that cycles continuously, and trivia- and scripture-shaped
 * providers that refuse to repeat until their pool is exhausted. **Signage implements none of those
 * policies** — that is the whole demonstration.
 */

export interface FixtureItem {
  readonly id: string;
  readonly label: string;
  /** Payload for the default audience. */
  readonly payload: Record<string, SignageJsonValue>;
  /** Payload for one specific audience, when this item has one. */
  readonly audiencePayloads?: Readonly<Record<string, Record<string, SignageJsonValue>>>;
  readonly availableUntil?: string | null;
  readonly durationMs?: number;
}

export type FixtureRepeatPolicy =
  /** Announcements: cycle the active set forever, in order, wrapping when it runs out. */
  | "cycle"
  /** Trivia and Scripture: never repeat until every currently available item has appeared. */
  | "no-repeat-until-exhausted";

export interface FixtureProviderOptions {
  readonly providerId: string;
  readonly sourceId: string;
  readonly sourceLabel: string;
  readonly items: readonly FixtureItem[];
  readonly policy: FixtureRepeatPolicy;
  readonly defaultDurationMs?: number;
  readonly contractVersion?: string;
  readonly rendererVersion?: string;
}

export interface FixtureProvider {
  readonly registration: SignageProviderRegistration;
  /** Every item id this provider has handed out, in order, across every scope. */
  readonly served: string[];
  /** Every `resolveNext` request it received, so a test can prove what Signage supplied. */
  readonly resolveRequests: SignageProviderResolveRequest[];
  readonly refreshRequests: SignageProviderRefreshRequest[];
  /** Replace the available set at run time — an announcement expiring, a question pool refilling. */
  setItems(items: readonly FixtureItem[]): void;
  /** Make the next `n` calls fail the way a briefly unavailable provider does. */
  failNext(count: number): void;
  /** Make every call hang, so the deadline is what ends it. */
  hang(hanging: boolean): void;
  /** Declare one item explicitly gone. */
  withdraw(itemId: string): void;
  /** Change an item's payload without changing which item it is — a cancellation, a countdown. */
  reviseItem(itemId: string, payload: Record<string, SignageJsonValue>): void;
}

export function createFixtureProvider(options: FixtureProviderOptions): FixtureProvider {
  let items = [...options.items];
  const revisions = new Map<string, number>();
  const withdrawn = new Set<string>();
  /** Per selection scope: which items have already been served in the current pass. This is the
   * provider's own state, exactly where the contract says it belongs — Signage stores none of it. */
  const seen = new Map<string, Set<string>>();
  const cursors = new Map<string, number>();
  const served: string[] = [];
  const resolveRequests: SignageProviderResolveRequest[] = [];
  const refreshRequests: SignageProviderRefreshRequest[] = [];
  let failures = 0;
  let hanging = false;

  function guard(): void {
    if (failures > 0) {
      failures -= 1;
      throw new Error("fixture provider is briefly unavailable");
    }
  }

  function available(at: string): readonly FixtureItem[] {
    const instant = Date.parse(at);
    return items.filter((item) => {
      if (withdrawn.has(item.id)) {
        return false;
      }
      if (typeof item.availableUntil !== "string") {
        return true;
      }
      return instant < Date.parse(item.availableUntil);
    });
  }

  function revisionOf(item: FixtureItem): string {
    return String(revisions.get(item.id) ?? 1);
  }

  function resolutionFor(item: FixtureItem): SignageProviderResolution {
    const variants = [
      { audienceKey: null, payload: item.payload },
      ...Object.entries(item.audiencePayloads ?? {}).map(([audienceKey, payload]) => ({
        audienceKey,
        payload,
      })),
    ];
    return {
      availableUntil: item.availableUntil ?? null,
      itemId: item.id,
      itemRevision: revisionOf(item),
      variants,
      ...(item.durationMs === undefined ? {} : { durationMs: item.durationMs }),
    };
  }

  function pickNext(scope: string, at: string): FixtureItem | null {
    const pool = available(at);
    if (pool.length === 0) {
      return null;
    }
    if (options.policy === "cycle") {
      const index = cursors.get(scope) ?? 0;
      const item = pool[index % pool.length] as FixtureItem;
      cursors.set(scope, index + 1);
      return item;
    }
    // No repeat until exhausted: only when every currently available item has appeared does the
    // pass reset. An item added mid-pass joins the current pass rather than waiting for the next.
    let usedInPass = seen.get(scope);
    if (!usedInPass) {
      usedInPass = new Set<string>();
      seen.set(scope, usedInPass);
    }
    let remaining = pool.filter((item) => !usedInPass.has(item.id));
    if (remaining.length === 0) {
      usedInPass.clear();
      remaining = [...pool];
    }
    const item = remaining[0] as FixtureItem;
    usedInPass.add(item.id);
    return item;
  }

  const registration: SignageProviderRegistration = {
    contractVersion: options.contractVersion ?? "1.0.0",
    defaultDurationMs: options.defaultDurationMs ?? 5000,

    listItems(request: SignageProviderDiscoveryRequest): readonly SignageProviderItemDescriptor[] {
      guard();
      return available(request.at).map((item) => ({
        id: item.id,
        label: item.label,
        ...(item.availableUntil === undefined ? {} : { availableUntil: item.availableUntil }),
      }));
    },

    listSources(): readonly SignageProviderSourceDescriptor[] {
      guard();
      return [{ id: options.sourceId, label: options.sourceLabel }];
    },

    providerId: options.providerId,
    providerVersion: "1.0.0",

    async refresh(
      request: SignageProviderRefreshRequest,
    ): Promise<SignageProviderResolution | null> {
      refreshRequests.push(request);
      if (hanging) {
        await new Promise(() => undefined);
      }
      guard();
      if (withdrawn.has(request.itemId)) {
        // Explicitly gone — distinct from "nothing right now", and Signage removes it at the next
        // safe boundary rather than mid-slide.
        return {
          itemId: request.itemId,
          itemRevision: revisionOf({ id: request.itemId } as FixtureItem),
          variants: [{ audienceKey: null, payload: { withdrawn: true } }],
          withdrawn: true,
        };
      }
      const item = available(request.at).find((candidate) => candidate.id === request.itemId);
      return item ? resolutionFor(item) : null;
    },

    renderer: {
      contributionId: `${options.providerId}.slide`,
      contributionVersion: options.rendererVersion ?? "1.0.0",
    },

    async resolveNext(
      request: SignageProviderResolveRequest,
    ): Promise<SignageProviderResolution | null> {
      resolveRequests.push(request);
      if (hanging) {
        await new Promise(() => undefined);
      }
      guard();
      if (request.sourceId !== options.sourceId) {
        return null;
      }
      const item = pickNext(request.selectionScopeId, request.at);
      if (!item) {
        return null;
      }
      served.push(item.id);
      return resolutionFor(item);
    },
  };

  return {
    failNext(count: number): void {
      failures = count;
    },
    hang(value: boolean): void {
      hanging = value;
    },
    refreshRequests,
    registration,
    resolveRequests,
    reviseItem(itemId: string, payload: Record<string, SignageJsonValue>): void {
      items = items.map((item) => (item.id === itemId ? { ...item, payload } : item));
      revisions.set(itemId, (revisions.get(itemId) ?? 1) + 1);
    },
    served,
    setItems(next: readonly FixtureItem[]): void {
      items = [...next];
    },
    withdraw(itemId: string): void {
      withdrawn.add(itemId);
    },
  };
}

/** The three provider shapes the real modules will have, so a test can name them the way an operator
 * would. Nothing about their policies lives in Signage. */
export function announcementsFixture(): FixtureProvider {
  return createFixtureProvider({
    items: [
      { id: "welcome", label: "Welcome", payload: { headline: "Welcome" } },
      {
        audiencePayloads: { online: { headline: "Watching from home" } },
        id: "greeting",
        label: "Greeting",
        payload: { headline: "Good morning" },
      },
      { id: "giving", label: "Giving", payload: { headline: "Giving" } },
      { id: "kids", label: "Kids check-in", payload: { headline: "Kids check-in" } },
    ],
    policy: "cycle",
    providerId: "fixture.announcements",
    sourceId: "active-slides",
    sourceLabel: "Active announcements",
  });
}

export function triviaFixture(): FixtureProvider {
  return createFixtureProvider({
    items: [
      { id: "q1", label: "Question 1", payload: { question: "one" } },
      { id: "q2", label: "Question 2", payload: { question: "two" } },
      { id: "q3", label: "Question 3", payload: { question: "three" } },
    ],
    policy: "no-repeat-until-exhausted",
    providerId: "fixture.trivia",
    sourceId: "open-questions",
    sourceLabel: "Open questions",
  });
}

export function scriptureFixture(): FixtureProvider {
  return createFixtureProvider({
    items: [
      { id: "psalm-23", label: "Psalm 23", payload: { reference: "Psalm 23" } },
      { id: "john-3", label: "John 3", payload: { reference: "John 3" } },
    ],
    policy: "no-repeat-until-exhausted",
    providerId: "fixture.scripture",
    sourceId: "reading-plan",
    sourceLabel: "Reading plan",
  });
}