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 { IPackument, INpmVersion } from './interfaces.npm.js';

/**
 * NPM-specific upstream implementation.
 *
 * Handles:
 * - Package metadata (packument) fetching
 * - Tarball proxying
 * - Scoped package routing (@scope/* patterns)
 * - NPM-specific URL rewriting
 */
export class NpmUpstream extends BaseUpstream {
  protected readonly protocolName = 'npm';

  /** Local registry URL for rewriting tarball URLs */
  private readonly localRegistryUrl: string;

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

  /**
   * Fetch a packument from upstream registries.
   */
  public async fetchPackument(packageName: string): Promise<IPackument | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'npm',
      resource: packageName,
      resourceType: 'packument',
      path: `/${encodeURIComponent(packageName).replace('%40', '@')}`,
      method: 'GET',
      headers: {
        'accept': 'application/json',
      },
      query: {},
    };

    const result = await this.fetch(context);

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

    // Parse and process packument
    let packument: IPackument;
    if (Buffer.isBuffer(result.body)) {
      packument = JSON.parse(result.body.toString('utf8'));
    } else {
      packument = result.body;
    }

    // Rewrite tarball URLs to point to local registry
    packument = this.rewriteTarballUrls(packument);

    return packument;
  }

  /**
   * Fetch a specific version from upstream registries.
   */
  public async fetchVersion(packageName: string, version: string): Promise<INpmVersion | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'npm',
      resource: packageName,
      resourceType: 'version',
      path: `/${encodeURIComponent(packageName).replace('%40', '@')}/${version}`,
      method: 'GET',
      headers: {
        'accept': 'application/json',
      },
      query: {},
    };

    const result = await this.fetch(context);

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

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

    // Rewrite tarball URL
    if (versionData.dist?.tarball) {
      versionData.dist.tarball = this.rewriteSingleTarballUrl(
        packageName,
        versionData.version,
        versionData.dist.tarball,
      );
    }

    return versionData;
  }

  /**
   * Fetch a tarball from upstream registries.
   */
  public async fetchTarball(packageName: string, version: string): Promise<Buffer | null> {
    // First, try to get the tarball URL from packument
    const packument = await this.fetchPackument(packageName);
    let tarballPath: string;

    if (packument?.versions?.[version]?.dist?.tarball) {
      // Extract path from original (upstream) tarball URL
      const tarballUrl = packument.versions[version].dist.tarball;
      try {
        const url = new URL(tarballUrl);
        tarballPath = url.pathname;
      } catch {
        // Fallback to standard NPM tarball path
        tarballPath = this.buildTarballPath(packageName, version);
      }
    } else {
      tarballPath = this.buildTarballPath(packageName, version);
    }

    const context: IUpstreamFetchContext = {
      protocol: 'npm',
      resource: packageName,
      resourceType: 'tarball',
      path: tarballPath,
      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);
  }

  /**
   * Search packages in upstream registries.
   */
  public async search(text: string, size: number = 20, from: number = 0): Promise<any | null> {
    const context: IUpstreamFetchContext = {
      protocol: 'npm',
      resource: '*',
      resourceType: 'search',
      path: '/-/v1/search',
      method: 'GET',
      headers: {
        'accept': 'application/json',
      },
      query: {
        text,
        size: size.toString(),
        from: from.toString(),
      },
    };

    const result = await this.fetch(context);

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

    if (Buffer.isBuffer(result.body)) {
      return JSON.parse(result.body.toString('utf8'));
    }

    return result.body;
  }

  /**
   * Build the standard NPM tarball path.
   */
  private buildTarballPath(packageName: string, version: string): string {
    // NPM uses: /{package}/-/{package-name}-{version}.tgz
    // For scoped packages: /@scope/name/-/name-version.tgz
    if (packageName.startsWith('@')) {
      const [scope, name] = packageName.split('/');
      return `/${scope}/${name}/-/${name}-${version}.tgz`;
    } else {
      return `/${packageName}/-/${packageName}-${version}.tgz`;
    }
  }

  /**
   * Rewrite all tarball URLs in a packument to point to local registry.
   */
  private rewriteTarballUrls(packument: IPackument): IPackument {
    if (!packument.versions) {
      return packument;
    }

    const rewritten = { ...packument };
    rewritten.versions = {};

    for (const [version, versionData] of Object.entries(packument.versions)) {
      const newVersionData = { ...versionData };
      if (newVersionData.dist?.tarball) {
        newVersionData.dist = {
          ...newVersionData.dist,
          tarball: this.rewriteSingleTarballUrl(
            packument.name,
            version,
            newVersionData.dist.tarball,
          ),
        };
      }
      rewritten.versions[version] = newVersionData;
    }

    return rewritten;
  }

  /**
   * Rewrite a single tarball URL to point to local registry.
   */
  private rewriteSingleTarballUrl(
    packageName: string,
    version: string,
    _originalUrl: string,
  ): string {
    // Generate local tarball URL
    // Format: {localRegistryUrl}/{package}/-/{package-name}-{version}.tgz
    const safeName = packageName.replace('@', '').replace('/', '-');
    return `${this.localRegistryUrl}/${packageName}/-/${safeName}-${version}.tgz`;
  }

  /**
   * Override URL building for NPM-specific handling.
   */
  protected buildUpstreamUrl(
    upstream: IUpstreamRegistryConfig,
    context: IUpstreamFetchContext,
  ): string {
    // NPM registries often don't have trailing slashes
    let baseUrl = upstream.url;
    if (baseUrl.endsWith('/')) {
      baseUrl = baseUrl.slice(0, -1);
    }

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