import type { ZodType, z } from 'zod/v4';
import { ZodError } from 'zod/v4';
import { logger } from '../../logger/index.ts';
import { ExternalHostError } from '../../types/errors/external-host-error.ts';
import type { PackageCacheNamespace } from '../../util/cache/package/types.ts';
import type { CachedOptions } from '../../util/cache/package/with-cache.ts';
import { withCache } from '../../util/cache/package/with-cache.ts';
import type { HttpBase } from '../../util/http/http.ts';
import { Http, HttpError } from '../../util/http/index.ts';
import type { HttpOptions } from '../../util/http/types.ts';
import { coerceObject } from '../../util/object.ts';
import type {
  DatasourceApi,
  DigestConfig,
  GetReleasesConfig,
  PostprocessReleaseConfig,
  PostprocessReleaseResult,
  RegistryStrategy,
  Release,
  ReleaseResult,
  SourceUrlSupport,
} from './types.ts';

/**
 * The options accepted by the JSON methods of the http client `H`:
 * `HttpOptions` for the plain client, and the client's own options type for a
 * specialised one such as `GithubHttp`.
 */
type JsonOptions<H extends Http> =
  H extends HttpBase<infer Opts, any> ? Opts : HttpOptions;

export abstract class Datasource<
  H extends Http = Http,
> implements DatasourceApi {
  public readonly id: string;

  /**
   * The package cache namespace used by {@link Datasource.cached}.
   * Defaults to `datasource-<id>`, which must be registered in
   * `packageCacheNamespaces`.
   */
  protected readonly cacheNamespace: PackageCacheNamespace;

  /**
   * A subclass that narrows `H` to a specialised client (`GithubHttp`,
   * `GitlabHttp`, ...) must construct that client itself and pass it as
   * `http`, since this constructor can only build the plain `Http` default.
   */
  protected constructor(id: string, http?: H) {
    this.id = id;
    this.http = http ?? (new Http(id) as H);
    this.cacheNamespace = `datasource-${id}` as PackageCacheNamespace;
  }

  caching: boolean | undefined;

  defaultConfig: Record<string, unknown> | undefined;

  getDefaultRegistryUrls(_packageName: string): string[] | undefined {
    return undefined;
  }

  supportsCustomRegistry(_packageName: string): boolean {
    return true;
  }

  defaultVersioning?: string | undefined;

  registryStrategy: RegistryStrategy = 'first';

  releaseTimestampSupport = false;
  releaseTimestampNote?: string | undefined;

  sourceUrlSupport: SourceUrlSupport = 'none';
  sourceUrlNote?: string | undefined;

  protected readonly http: H;

  abstract getReleases(
    getReleasesConfig: GetReleasesConfig,
  ): Promise<ReleaseResult | null>;

  /**
   * `newValue` may be `undefined`, for example when only the digest of the
   * current value is being resolved. Implementations must handle that case
   * explicitly, for example by resolving the digest of a default branch or
   * by returning `null`.
   */
  getDigest?(config: DigestConfig, newValue?: string): Promise<string | null>;

  postprocessRelease?(
    config: PostprocessReleaseConfig,
    release: Release,
  ): Promise<PostprocessReleaseResult>;

  handleHttpErrors(_err: HttpError): void {
    // intentionally empty
  }

  /**
   * Caches the result of `fn` in the datasource cache namespace.
   *
   * Same as {@link withCache}, except that `namespace` defaults to
   * {@link Datasource.cacheNamespace}.
   */
  protected cached<T>(
    options: Omit<CachedOptions, 'namespace'> & {
      namespace?: PackageCacheNamespace;
    },
    fn: () => T | Promise<T>,
  ): Promise<T> {
    return withCache(
      { ...options, namespace: options.namespace ?? this.cacheNamespace },
      fn,
    );
  }

  /**
   * Requests `url` and returns the response body validated by `schema`.
   *
   * Every error, a response that fails validation included, goes through
   * {@link Datasource.handleGenericErrors} and therefore fails the lookup. Use
   * it when a malformed response must be treated as an error; use
   * {@link Datasource.fetchJsonOrNull} when it should count as "no data from
   * this registry" instead.
   */
  protected async fetchJson<Schema extends ZodType<any, any, any>>(
    url: string,
    schema: Schema,
    options?: JsonOptions<H>,
  ): Promise<z.infer<Schema>> {
    const httpOptions = coerceObject(options) as HttpOptions;
    try {
      const { body } = await this.http.getJson(url, httpOptions, schema);
      return body;
    } catch (err) {
      this.handleGenericErrors(err);
    }
  }

  /**
   * Same as {@link Datasource.fetchJson}, except that a response which fails
   * schema validation is logged and reported as `null`.
   *
   * Use it when a malformed response means "no data from this registry" rather
   * than a failed lookup. Every other error still goes through
   * {@link Datasource.handleGenericErrors}.
   */
  protected async fetchJsonOrNull<Schema extends ZodType<any, any, any>>(
    url: string,
    schema: Schema,
    options?: JsonOptions<H>,
  ): Promise<z.infer<Schema> | null> {
    try {
      return await this.fetchJson(url, schema, options);
    } catch (err) {
      if (err instanceof ZodError) {
        logger.debug(
          { err, datasource: this.id, url },
          'Ignoring response that failed schema validation',
        );
        return null;
      }

      throw err;
    }
  }

  protected handleGenericErrors(err: Error): never {
    if (err instanceof ExternalHostError) {
      throw err;
    }

    if (err instanceof HttpError) {
      this.handleHttpErrors(err);

      const statusCode = err.response?.statusCode;
      if (
        statusCode &&
        (statusCode === 429 || (statusCode >= 500 && statusCode < 600))
      ) {
        throw new ExternalHostError(err);
      }
    }

    throw err;
  }
}