import {
  type ModuleStorage,
  type ModuleStorageBody,
  ModuleStorageError,
  type ModuleStorageListOptions,
  type ModuleStorageListing,
  type ModuleStorageObject,
  type ModuleStorageObjectMetadata,
  type ModuleStoragePutOptions,
} from "@ekklesia/contracts";
import type { DiscoveredModule, ModuleStorageLookup } from "@ekklesia/core/modules";
import { createModuleStorageLookup, type StorageProvider } from "@ekklesia/core/storage";

/** Builds and drains Web streams without depending on DOM-only helper types, which this package's
 * TypeScript configuration deliberately does not load. */
function streamOf(bytes: Uint8Array): ReadableStream<Uint8Array> {
  return new ReadableStream<Uint8Array>({
    start(controller) {
      controller.enqueue(bytes);
      controller.close();
    },
  });
}

async function collect(stream: ReadableStream<Uint8Array>): Promise<Uint8Array> {
  const reader = stream.getReader();
  const chunks: Uint8Array[] = [];
  let total = 0;
  for (;;) {
    const { done, value } = await reader.read();
    if (done) {
      break;
    }
    chunks.push(value);
    total += value.byteLength;
  }
  const merged = new Uint8Array(total);
  let offset = 0;
  for (const chunk of chunks) {
    merged.set(chunk, offset);
    offset += chunk.byteLength;
  }
  return merged;
}

interface StoredObject {
  readonly bytes: Uint8Array;
  readonly contentType?: string;
  readonly lastModified: Date;
}

/**
 * An in-memory `StorageProvider` for tests that exercise **wiring, scoping, and routing** rather
 * than the S3 protocol.
 *
 * It implements the same interface the real S3 provider does, so everything above the provider seam
 * — binding resolution, the scoped facade, lifecycle eligibility, route wiring — is exercised
 * unchanged. What it deliberately does *not* reproduce is the protocol itself: real SeaweedFS
 * semantics (non-idempotent `CreateBucket`, `NoSuchKey` vs `NoSuchBucket`, ETag quoting, streaming
 * bodies) are proven against a live server in `core/tests/module-storage.integration.ts`, so this
 * double can never quietly stand in for a provider guarantee nobody checked.
 *
 * It keys everything by **physical** bucket, exactly as the real provider does, which is what lets a
 * test assert that two modules declaring the same logical name really did land in different
 * namespaces.
 */
export function createInMemoryStorageProvider(): StorageProvider & {
  readonly buckets: ReadonlyMap<string, Map<string, StoredObject>>;
  ensureBucketCalls: number;
} {
  const buckets = new Map<string, Map<string, StoredObject>>();
  const state = { ensureBucketCalls: 0 };

  const objectsIn = (physicalBucket: string): Map<string, StoredObject> => {
    const bucket = buckets.get(physicalBucket);
    if (!bucket) {
      throw new ModuleStorageError("STORAGE_BUCKET_UNAVAILABLE");
    }
    return bucket;
  };

  const metadataFor = (key: string, stored: StoredObject): ModuleStorageObjectMetadata =>
    Object.freeze({
      contentLength: stored.bytes.byteLength,
      key,
      lastModified: stored.lastModified,
      ...(stored.contentType === undefined ? {} : { contentType: stored.contentType }),
    });

  const provider: StorageProvider = {
    async close(): Promise<void> {
      // Nothing to release.
    },
    async delete(physicalBucket: string, key: string): Promise<void> {
      objectsIn(physicalBucket).delete(key);
    },
    async ensureBucket(physicalBucket: string): Promise<void> {
      state.ensureBucketCalls += 1;
      if (!buckets.has(physicalBucket)) {
        buckets.set(physicalBucket, new Map());
      }
    },
    async get(physicalBucket: string, key: string): Promise<ModuleStorageObject> {
      const stored = objectsIn(physicalBucket).get(key);
      if (!stored) {
        throw new ModuleStorageError("STORAGE_OBJECT_NOT_FOUND", key);
      }
      return Object.freeze({
        ...metadataFor(key, stored),
        body: streamOf(stored.bytes),
      });
    },
    async head(physicalBucket: string, key: string): Promise<ModuleStorageObjectMetadata> {
      const stored = objectsIn(physicalBucket).get(key);
      if (!stored) {
        throw new ModuleStorageError("STORAGE_OBJECT_NOT_FOUND", key);
      }
      return metadataFor(key, stored);
    },
    async list(
      physicalBucket: string,
      options: ModuleStorageListOptions,
    ): Promise<ModuleStorageListing> {
      const entries = [...objectsIn(physicalBucket).entries()]
        .filter(([key]) => options.prefix === undefined || key.startsWith(options.prefix))
        .sort(([left], [right]) => (left < right ? -1 : left > right ? 1 : 0));
      return Object.freeze({
        objects: Object.freeze(entries.map(([key, stored]) => metadataFor(key, stored))),
      });
    },
    async probe(): Promise<void> {
      // Always reachable.
    },
    async put(
      physicalBucket: string,
      key: string,
      body: ModuleStorageBody,
      options: ModuleStoragePutOptions,
    ): Promise<ModuleStorageObjectMetadata> {
      const bytes =
        typeof body === "string"
          ? new TextEncoder().encode(body)
          : body instanceof Uint8Array
            ? body
            : await collect(body as ReadableStream<Uint8Array>);
      const stored: StoredObject = {
        bytes,
        lastModified: new Date(0),
        ...(options.contentType === undefined ? {} : { contentType: options.contentType }),
      };
      objectsIn(physicalBucket).set(key, stored);
      return metadataFor(key, stored);
    },
  };

  return Object.assign(provider, {
    buckets: buckets as ReadonlyMap<string, Map<string, StoredObject>>,
    get ensureBucketCalls(): number {
      return state.ensureBucketCalls;
    },
  });
}

export interface ModuleStorageOption {
  readonly snapshots: ModuleStorageLookup;
  readonly providerConfigured: boolean;
}

/**
 * Builds the `createApiApp` storage option the same way `startApi` does — resolve every module's
 * declared buckets against one provider and one prefix — rather than hand-writing a map, so a test
 * can never assert against a shape the real composition would not produce.
 */
export function moduleStorageOptionFor(
  discoveredModules: readonly DiscoveredModule[],
  provider?: StorageProvider,
): ModuleStorageOption {
  return {
    providerConfigured: provider !== undefined,
    snapshots: createModuleStorageLookup(
      provider,
      "ekklesia",
      discoveredModules.map((module) => ({
        logicalBucketIds: module.manifest.storage.buckets.map((bucket) => bucket.id),
        moduleId: module.manifest.id,
      })),
    ),
  };
}

/** The storage option for a `createApiApp` caller that exercises no storage at all — the explicit
 * "this installation has no object storage" statement the required option asks for. */
export function emptyModuleStorage(): ModuleStorageOption {
  return { providerConfigured: false, snapshots: new Map<string, ModuleStorage>() };
}