import type { InstalledOfflineCommandContribution } from "./offline-command.ts";
import type { InstalledServiceWorkerSelection } from "./service-worker.ts";
import type { InstalledWebWorkerContribution } from "./web-worker.ts";

/**
 * §3.4–§3.6. Optional runtime capability selection and hosting.
 *
 * Source contribution decides what is installed. Runtime Config may only carry
 * `DEFAULT | DISABLED`, so a configuration document can never switch on a
 * capability whose source is absent.
 */

export type RuntimeCapabilityOverride = "DEFAULT" | "DISABLED";

export type RuntimeStopReason =
  | "APPLICATION_SHUTDOWN"
  | "SCOPE_FENCED"
  | "FEATURE_DISABLED"
  | "HIDDEN_POLICY"
  | "INCIDENT_CONTAINMENT";

export interface RuntimeLifecycle {
  start(): void | Promise<void>;
  stop(reason: RuntimeStopReason): void | Promise<void>;
  dispose(): void | Promise<void>;
}

/** §20.2. `FAILED -> STARTING` is never automatic. */
export type RuntimeLifecycleState =
  | "NEW"
  | "STARTING"
  | "RUNNING"
  | "STOPPING"
  | "STOPPED"
  | "FAILED"
  | "DISPOSING"
  | "DISPOSED";

/** §22.12. Health is per capability; there is no global `healthy` boolean. */
export type RuntimeHealth =
  | "AVAILABLE"
  | "DEGRADED"
  | "UNAVAILABLE"
  | "INCOMPATIBLE"
  | "DISABLED";

// §13.2. Realtime product contribution.
export type RealtimeEffectKind =
  | "INVALIDATE_TOPICS"
  | "APPLY_AUTHORITATIVE_DELTA"
  | "EPHEMERAL_NOTIFICATION";

export interface InstalledRealtimeEventEffect {
  readonly eventType: string;
  readonly mapperId: string;
  readonly effect: RealtimeEffectKind;
  readonly invalidationTopics: readonly string[];
}

export type InstalledRealtimeTransport =
  | Readonly<{ kind: "SSE"; endpointId: string }>
  | Readonly<{ kind: "WEBSOCKET"; endpointId: string }>
  | Readonly<{ kind: "POLLING"; operationId: string; intervalMs: number }>;

export interface InstalledRealtimeContribution {
  readonly contributionId: string;
  readonly featureId: string;
  readonly contractSourcePackageId: string;
  readonly streamId: string;
  readonly recoveryMode: "CURSOR" | "SNAPSHOT_ONLY" | "SESSION_REBUILD";
  readonly eventEffects: readonly InstalledRealtimeEventEffect[];
  readonly transport: InstalledRealtimeTransport;
}

export const REALTIME_CONTRIBUTION_BOUNDS = Object.freeze({
  contributions: 64,
  streams: 128,
  eventTypes: 512,
  effectsPerEvent: 8,
  invalidationTopicsPerEvent: 32,
  minimumPollingIntervalMs: 5_000,
  maximumPollingIntervalMs: 300_000,
});

export interface InstalledRuntimeCapabilities {
  readonly realtime: readonly InstalledRealtimeContribution[];
  readonly webWorkers: readonly InstalledWebWorkerContribution[];
  readonly serviceWorker: InstalledServiceWorkerSelection | null;
  readonly offlineCommands: InstalledOfflineCommandContribution | null;
}

export type CapabilityOverrideMap = Readonly<{
  REALTIME: RuntimeCapabilityOverride;
  WEB_WORKER: RuntimeCapabilityOverride;
  SERVICE_WORKER: RuntimeCapabilityOverride;
  OFFLINE_COMMANDS: RuntimeCapabilityOverride;
}>;

/**
 * The effective selection after applying runtime overrides. `serviceWorkerMode`
 * keeps the §3.6 persistent-registration exception explicit: a statically
 * `ACTIVE` worker that runtime config disables still performs exactly one
 * owned-registration lookup and at most one unregister, and deletes no cache.
 */
export type ResolvedRuntimeCapabilities = Readonly<{
  realtime: readonly InstalledRealtimeContribution[];
  webWorkers: readonly InstalledWebWorkerContribution[];
  serviceWorker: InstalledServiceWorkerSelection | null;
  serviceWorkerDisabledCleanup: boolean;
  offlineCommands: InstalledOfflineCommandContribution | null;
}>;

export function resolveRuntimeCapabilities(
  installed: InstalledRuntimeCapabilities,
  overrides: CapabilityOverrideMap,
): ResolvedRuntimeCapabilities {
  const realtimeDisabled = overrides.REALTIME === "DISABLED";
  const workersDisabled = overrides.WEB_WORKER === "DISABLED";
  const serviceWorkerDisabled = overrides.SERVICE_WORKER === "DISABLED";
  const offlineDisabled = overrides.OFFLINE_COMMANDS === "DISABLED";

  return Object.freeze({
    realtime: realtimeDisabled ? Object.freeze([]) : installed.realtime,
    webWorkers: workersDisabled ? Object.freeze([]) : installed.webWorkers,
    serviceWorker: serviceWorkerDisabled ? null : installed.serviceWorker,
    serviceWorkerDisabledCleanup:
      serviceWorkerDisabled && installed.serviceWorker?.mode === "ACTIVE",
    offlineCommands: offlineDisabled ? null : installed.offlineCommands,
  });
}

export function validateRealtimeContributions(
  contributions: readonly InstalledRealtimeContribution[],
): readonly InstalledRealtimeContribution[] {
  const bounds = REALTIME_CONTRIBUTION_BOUNDS;
  if (contributions.length > bounds.contributions) {
    throw new TypeError("Realtime contributions exceed their bound.");
  }
  const contributionIds = new Set<string>();
  const streamIds = new Set<string>();
  let eventTypeCount = 0;

  for (const contribution of contributions) {
    if (
      !contribution.contributionId ||
      contributionIds.has(contribution.contributionId)
    ) {
      throw new TypeError("Duplicate realtime contribution identity.");
    }
    contributionIds.add(contribution.contributionId);
    streamIds.add(contribution.streamId);
    if (streamIds.size > bounds.streams) {
      throw new TypeError("Realtime streams exceed their bound.");
    }

    const transport = contribution.transport;
    if (transport.kind === "POLLING") {
      if (
        !Number.isSafeInteger(transport.intervalMs) ||
        transport.intervalMs < bounds.minimumPollingIntervalMs ||
        transport.intervalMs > bounds.maximumPollingIntervalMs
      ) {
        throw new TypeError(
          `Realtime polling interval is out of range: ${contribution.contributionId}`,
        );
      }
    }

    const seenEvents = new Map<string, number>();
    for (const effect of contribution.eventEffects) {
      eventTypeCount += 1;
      if (eventTypeCount > bounds.eventTypes) {
        throw new TypeError("Realtime event types exceed their bound.");
      }
      const count = (seenEvents.get(effect.eventType) ?? 0) + 1;
      if (count > bounds.effectsPerEvent) {
        throw new TypeError(
          `Realtime effects per event exceeded: ${effect.eventType}`,
        );
      }
      seenEvents.set(effect.eventType, count);
      if (
        effect.invalidationTopics.length > bounds.invalidationTopicsPerEvent
      ) {
        throw new TypeError(
          `Realtime invalidation topics exceeded: ${effect.eventType}`,
        );
      }
      if (
        effect.effect === "INVALIDATE_TOPICS" &&
        effect.invalidationTopics.length === 0
      ) {
        throw new TypeError(
          `INVALIDATE_TOPICS effect declares no topic: ${effect.eventType}`,
        );
      }
    }
  }
  return Object.freeze([...contributions]);
}

export type RuntimeCapabilityId =
  | "REALTIME"
  | "WEB_WORKER"
  | "SERVICE_WORKER"
  | "OFFLINE_COMMANDS";

/**
 * §3.5. A bounded, serialisable view of one capability. `selected` is the
 * static SSOT count and `active` is what survived the runtime override, so the
 * difference between the two is exactly the operator's effect. An override can
 * only subtract, which is why a never-selected capability stays at zero.
 */
export type RuntimeCapabilityStatus = Readonly<{
  capabilityId: RuntimeCapabilityId;
  selected: number;
  active: number;
  override: RuntimeCapabilityOverride;
}>;

export type RuntimeCapabilitySnapshot = readonly RuntimeCapabilityStatus[];

const CAPABILITY_ORDER = Object.freeze([
  "REALTIME",
  "WEB_WORKER",
  "SERVICE_WORKER",
  "OFFLINE_COMMANDS",
] as const);

export function describeRuntimeCapabilities(
  installed: InstalledRuntimeCapabilities,
  overrides: CapabilityOverrideMap,
): RuntimeCapabilitySnapshot {
  const resolved = resolveRuntimeCapabilities(installed, overrides);
  const counts: Readonly<
    Record<RuntimeCapabilityId, Readonly<{ selected: number; active: number }>>
  > = Object.freeze({
    REALTIME: Object.freeze({
      selected: installed.realtime.length,
      active: resolved.realtime.length,
    }),
    WEB_WORKER: Object.freeze({
      selected: installed.webWorkers.length,
      active: resolved.webWorkers.length,
    }),
    SERVICE_WORKER: Object.freeze({
      selected: installed.serviceWorker === null ? 0 : 1,
      active: resolved.serviceWorker === null ? 0 : 1,
    }),
    OFFLINE_COMMANDS: Object.freeze({
      selected: installed.offlineCommands === null ? 0 : 1,
      active: resolved.offlineCommands === null ? 0 : 1,
    }),
  });

  return Object.freeze(
    CAPABILITY_ORDER.map((capabilityId) =>
      Object.freeze({
        capabilityId,
        selected: counts[capabilityId].selected,
        active: counts[capabilityId].active,
        override: overrides[capabilityId],
      }),
    ),
  );
}