import * as plugins from '../plugins.js';
import { BaseUpstream } from '../upstream/classes.baseupstream.js';
import type {
  IProtocolUpstreamConfig,
  IUpstreamFetchContext,
  IUpstreamResult,
  IUpstreamRegistryConfig,
} from '../upstream/interfaces.upstream.js';
import type { IOciManifest, IOciImageIndex, ITagList } from './interfaces.oci.js';

/**
 * OCI-specific upstream implementation.
 *
 * Handles:
 * - Manifest fetching (image manifests and index manifests)
 * - Blob proxying (layers, configs)
 * - Tag list fetching
 * - Content-addressable caching (blobs are immutable)
 * - Docker Hub authentication flow
 */
export class OciUpstream extends BaseUpstream {
  protected readonly protocolName = 'oci';

  /** Local registry base path for URL building */
  private readonly localBasePath: string;

  constructor(
    config: IProtocolUpstreamConfig,
    localBasePath: string = '/oci',
    logger?: plugins.smartlog.Smartlog,
  ) {
    super(config, logger);
    this.localBasePath = localBasePath;
  }

  /**
   * Fetch a manifest from upstream registries.
   */
  public async fetchManifest(
    repository: string,
    reference: string,
  ): Promise<{ manifest: IOciManifest | IOciImageIndex; contentType: string; digest: string } | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'oci',
      resource: repository,
      resourceType: 'manifest',
      path: `/v2/${repository}/manifests/${reference}`,
      method: 'GET',
      headers: {
        'accept': [
          'application/vnd.oci.image.manifest.v1+json',
          'application/vnd.oci.image.index.v1+json',
          'application/vnd.docker.distribution.manifest.v2+json',
          'application/vnd.docker.distribution.manifest.list.v2+json',
          'application/vnd.docker.distribution.manifest.v1+json',
        ].join(', '),
      },
      query: {},
    };

    const result = await this.fetch(context);

    if (!result || !result.success) {
      return null;
    }

    let manifest: IOciManifest | IOciImageIndex;
    if (Buffer.isBuffer(result.body)) {
      manifest = JSON.parse(result.body.toString('utf8'));
    } else {
      manifest = result.body;
    }

    const contentType = result.headers['content-type'] || 'application/vnd.oci.image.manifest.v1+json';
    const digest = result.headers['docker-content-digest'] || '';

    return { manifest, contentType, digest };
  }

  /**
   * Check if a manifest exists in upstream (HEAD request).
   */
  public async headManifest(
    repository: string,
    reference: string,
  ): Promise<{ exists: boolean; contentType?: string; digest?: string; size?: number } | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'oci',
      resource: repository,
      resourceType: 'manifest',
      path: `/v2/${repository}/manifests/${reference}`,
      method: 'HEAD',
      headers: {
        'accept': [
          'application/vnd.oci.image.manifest.v1+json',
          'application/vnd.oci.image.index.v1+json',
          'application/vnd.docker.distribution.manifest.v2+json',
          'application/vnd.docker.distribution.manifest.list.v2+json',
        ].join(', '),
      },
      query: {},
    };

    const result = await this.fetch(context);

    if (!result) {
      return null;
    }

    if (!result.success) {
      return { exists: false };
    }

    return {
      exists: true,
      contentType: result.headers['content-type'],
      digest: result.headers['docker-content-digest'],
      size: result.headers['content-length'] ? parseInt(result.headers['content-length'], 10) : undefined,
    };
  }

  /**
   * Fetch a blob from upstream registries.
   */
  public async fetchBlob(repository: string, digest: string): Promise<Buffer | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'oci',
      resource: repository,
      resourceType: 'blob',
      path: `/v2/${repository}/blobs/${digest}`,
      method: 'GET',
      headers: {
        'accept': 'application/octet-stream',
      },
      query: {},
    };

    const result = await this.fetch(context);

    if (!result || !result.success) {
      return null;
    }

    return Buffer.isBuffer(result.body) ? result.body : Buffer.from(result.body);
  }

  /**
   * Check if a blob exists in upstream (HEAD request).
   */
  public async headBlob(
    repository: string,
    digest: string,
  ): Promise<{ exists: boolean; size?: number } | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'oci',
      resource: repository,
      resourceType: 'blob',
      path: `/v2/${repository}/blobs/${digest}`,
      method: 'HEAD',
      headers: {},
      query: {},
    };

    const result = await this.fetch(context);

    if (!result) {
      return null;
    }

    if (!result.success) {
      return { exists: false };
    }

    return {
      exists: true,
      size: result.headers['content-length'] ? parseInt(result.headers['content-length'], 10) : undefined,
    };
  }

  /**
   * Fetch the tag list for a repository.
   */
  public async fetchTags(repository: string, n?: number, last?: string): Promise<ITagList | null> {
    const query: Record<string, string> = {};
    if (n) query.n = n.toString();
    if (last) query.last = last;

    const context: IUpstreamFetchContext = {
      protocol: 'oci',
      resource: repository,
      resourceType: 'tags',
      path: `/v2/${repository}/tags/list`,
      method: 'GET',
      headers: {
        'accept': 'application/json',
      },
      query,
    };

    const result = await this.fetch(context);

    if (!result || !result.success) {
      return null;
    }

    let tagList: ITagList;
    if (Buffer.isBuffer(result.body)) {
      tagList = JSON.parse(result.body.toString('utf8'));
    } else {
      tagList = result.body;
    }

    return tagList;
  }

  /**
   * Override URL building for OCI-specific handling.
   * OCI registries use /v2/ prefix and may require special handling for Docker Hub.
   */
  protected buildUpstreamUrl(
    upstream: IUpstreamRegistryConfig,
    context: IUpstreamFetchContext,
  ): string {
    let baseUrl = upstream.url;

    // Remove trailing slash
    if (baseUrl.endsWith('/')) {
      baseUrl = baseUrl.slice(0, -1);
    }

    // Handle Docker Hub special case
    // Docker Hub uses registry-1.docker.io but library images need special handling
    if (baseUrl.includes('docker.io') || baseUrl.includes('registry-1.docker.io')) {
      // For library images (e.g., "nginx" -> "library/nginx")
      const pathParts = context.path.match(/^\/v2\/([^\/]+)\/(.+)$/);
      if (pathParts) {
        const [, repository, rest] = pathParts;
        // If repository doesn't contain a slash, it's a library image
        if (!repository.includes('/')) {
          return `${baseUrl}/v2/library/${repository}/${rest}`;
        }
      }
    }

    return `${baseUrl}${context.path}`;
  }

  /**
   * Override header building for OCI-specific authentication.
   * OCI registries may require token-based auth obtained from a separate endpoint.
   */
  protected buildHeaders(
    upstream: IUpstreamRegistryConfig,
    context: IUpstreamFetchContext,
  ): Record<string, string> {
    const headers = super.buildHeaders(upstream, context);

    // OCI registries typically use Docker-Distribution-API-Version header
    headers['docker-distribution-api-version'] = 'registry/2.0';

    return headers;
  }
}