import { isCacheInvalidationTopic } from "./cache-invalidation.ts";
import {
  defineQueryNamespaceIdentity,
  queryNamespaceIdentityKey,
  type QueryNamespaceIdentity,
} from "./query-keys.ts";

declare const queryInvalidationTopicBrand: unique symbol;

/**
 * Opaque registry-issued invalidation identity. The brand prevents feature
 * code from accidentally passing a concrete query-key string to the mutation
 * bridge.
 */
export type QueryInvalidationTopic = string &
  Readonly<{ [queryInvalidationTopicBrand]: true }>;

export function defineQueryInvalidationTopic(
  value: string,
): QueryInvalidationTopic {
  if (!isCacheInvalidationTopic(value)) {
    throw new TypeError("Query invalidation topic is invalid.");
  }
  return value as QueryInvalidationTopic;
}

/**
 * §12.2. Many-to-many topic/namespace registry.
 *
 * Topics stay opaque on the wire; the registry is what turns one received topic
 * into the local namespaces that must revalidate. Bounds are checked at startup
 * so a fan-out explosion cannot be introduced at runtime.
 */
export const INVALIDATION_REGISTRY_BOUNDS = Object.freeze({
  maxTopics: 256,
  maxNamespaces: 256,
  maxEdges: 1_024,
  maxTopicFanOut: 64,
  maxNamespaceFanIn: 64,
  maxIdBytes: 80,
});

export type InvalidationRegistryEdge = Readonly<{
  topicId: string;
  namespace: QueryNamespaceIdentity;
}>;

export interface InvalidationRegistry {
  readonly topics: readonly string[];
  readonly namespaces: readonly QueryNamespaceIdentity[];
  readonly edges: readonly InvalidationRegistryEdge[];
}

export type InvalidationRegistryIndex = Readonly<{
  namespacesForTopic: ReadonlyMap<
    string,
    readonly QueryNamespaceIdentity[]
  >;
  topicsForNamespace: ReadonlyMap<string, readonly string[]>;
}>;

export type InvalidationTopicVersionDefinition = Readonly<{
  topicId: string;
  topicVersion: number;
}>;

function hasControlCharacter(value: string): boolean {
  for (const character of value) {
    const codePoint = character.codePointAt(0) ?? 0;
    if (codePoint <= 0x1f || codePoint === 0x7f) return true;
  }
  return false;
}

/**
 * Rejects duplicates, orphan topics and orphan namespaces at startup. An edge
 * that points at an unregistered endpoint is a composition defect, not a
 * runtime condition to be tolerated.
 */
export function indexInvalidationRegistry(
  registry: InvalidationRegistry,
): InvalidationRegistryIndex {
  const bounds = INVALIDATION_REGISTRY_BOUNDS;
  const encoder = new TextEncoder();
  const assertId = (value: string, label: string) => {
    if (
      typeof value !== "string" ||
      value.length === 0 ||
      hasControlCharacter(value) ||
      encoder.encode(value).byteLength > bounds.maxIdBytes
    ) {
      throw new TypeError(`Invalidation registry ${label} is invalid.`);
    }
  };

  if (
    registry.topics.length > bounds.maxTopics ||
    registry.namespaces.length > bounds.maxNamespaces ||
    registry.edges.length > bounds.maxEdges
  ) {
    throw new TypeError("Invalidation registry exceeds its bounds.");
  }

  const topics = new Set<string>();
  for (const topic of registry.topics) {
    assertId(topic, "topic");
    if (topics.has(topic)) {
      throw new TypeError(`Duplicate invalidation topic: ${topic}`);
    }
    topics.add(topic);
  }
  const namespaces = new Map<string, QueryNamespaceIdentity>();
  for (const namespace of registry.namespaces) {
    let namespaceKey: string;
    let namespaceSnapshot: QueryNamespaceIdentity;
    try {
      namespaceSnapshot = defineQueryNamespaceIdentity(
        namespace.namespaceId,
        namespace.namespaceVersion,
      );
      namespaceKey = queryNamespaceIdentityKey(namespaceSnapshot);
    } catch (error) {
      throw new TypeError("Invalidation registry namespace is invalid.", {
        cause: error,
      });
    }
    if (namespaces.has(namespaceKey)) {
      throw new TypeError(`Duplicate invalidation namespace: ${namespaceKey}`);
    }
    namespaces.set(namespaceKey, namespaceSnapshot);
  }

  const namespacesForTopic = new Map<string, QueryNamespaceIdentity[]>();
  const topicsForNamespace = new Map<string, string[]>();
  const seenEdges = new Map<string, Set<string>>();
  for (const edge of registry.edges) {
    let namespaceKey: string;
    try {
      namespaceKey = queryNamespaceIdentityKey(edge.namespace);
    } catch (error) {
      throw new TypeError("Invalidation registry namespace is invalid.", {
        cause: error,
      });
    }
    const registeredNamespace = namespaces.get(namespaceKey);
    if (!topics.has(edge.topicId) || !registeredNamespace) {
      throw new TypeError("Invalidation edge references an unknown endpoint.");
    }
    const seenNamespaces = seenEdges.get(edge.topicId) ?? new Set<string>();
    if (seenNamespaces.has(namespaceKey)) {
      throw new TypeError("Duplicate invalidation edge.");
    }
    seenNamespaces.add(namespaceKey);
    seenEdges.set(edge.topicId, seenNamespaces);

    const fanOut = namespacesForTopic.get(edge.topicId) ?? [];
    fanOut.push(registeredNamespace);
    if (fanOut.length > bounds.maxTopicFanOut) {
      throw new TypeError(`Invalidation topic fan-out exceeded: ${edge.topicId}`);
    }
    namespacesForTopic.set(edge.topicId, fanOut);

    const fanIn = topicsForNamespace.get(namespaceKey) ?? [];
    fanIn.push(edge.topicId);
    if (fanIn.length > bounds.maxNamespaceFanIn) {
      throw new TypeError(
        `Invalidation namespace fan-in exceeded: ${namespaceKey}`,
      );
    }
    topicsForNamespace.set(namespaceKey, fanIn);
  }

  for (const topic of topics) {
    if (!namespacesForTopic.has(topic)) {
      throw new TypeError(`Orphan invalidation topic: ${topic}`);
    }
  }
  for (const namespaceKey of namespaces.keys()) {
    if (!topicsForNamespace.has(namespaceKey)) {
      throw new TypeError(`Orphan invalidation namespace: ${namespaceKey}`);
    }
  }

  return Object.freeze({
    namespacesForTopic: new Map(
      [...namespacesForTopic].map(([key, value]) => [
        key,
        Object.freeze([...value]) as readonly QueryNamespaceIdentity[],
      ]),
    ),
    topicsForNamespace: new Map(
      [...topicsForNamespace].map(([key, value]) => [
        key,
        Object.freeze([...value]) as readonly string[],
      ]),
    ),
  });
}

/** Projects the graph's wire-only topic versions and rejects composition drift. */
export function indexInvalidationTopicVersions(
  registry: Pick<InvalidationRegistry, "topics">,
  definitions: readonly InvalidationTopicVersionDefinition[],
): ReadonlyMap<string, number> {
  if (
    registry.topics.length > INVALIDATION_REGISTRY_BOUNDS.maxTopics ||
    definitions.length > INVALIDATION_REGISTRY_BOUNDS.maxTopics
  ) {
    throw new TypeError("Invalidation topic version registry exceeds its bounds.");
  }
  const registeredTopics = new Set(registry.topics);
  if (
    registeredTopics.size !== registry.topics.length ||
    definitions.length !== registeredTopics.size
  ) {
    throw new TypeError("Invalidation topic version registry is inconsistent.");
  }

  const versions = new Map<string, number>();
  for (const definition of definitions) {
    if (
      !isCacheInvalidationTopic(definition.topicId) ||
      !registeredTopics.has(definition.topicId) ||
      !Number.isSafeInteger(definition.topicVersion) ||
      definition.topicVersion < 1 ||
      versions.has(definition.topicId)
    ) {
      throw new TypeError("Invalidation topic version registry is invalid.");
    }
    versions.set(definition.topicId, definition.topicVersion);
  }
  return versions;
}

export type QueryMutationLease = Readonly<{
  /**
   * Releases one local mutation fence. Remote hints coalesced while the fence
   * was held are applied once after the final lease for each topic is released.
   */
  release(): Promise<void>;
}>;

/**
 * Presentation-side facade for server-state invalidation.
 *
 * The caller knows only registry-issued topics. Query keys, BroadcastChannel
 * envelopes and browser transports stay inside the query infrastructure.
 */
export interface QueryInvalidationCoordinator {
  invalidate(topics: readonly QueryInvalidationTopic[]): Promise<void>;
  beginMutation(topics: readonly QueryInvalidationTopic[]): QueryMutationLease;
  /**
   * Local verified lifecycle only. A remote invalidation hint is never allowed
   * to clear the complete cache.
   */
  resetLocal(): Promise<void>;
  dispose(): void;
}