/**
 * DeepSeek Fetch API provider: page Markdown through one direct request, without
 * a model request.
 * @module @deepseek-ai/dsh-web-deepseek-api/fetch
 */
import type { WebFetchProvider, WebFetchRequest, WebFetchResult } from '@deepseek-ai/dsh-web'
import { DEEPSEEK_WEB_API_GUIDANCE } from './search.ts'
import {
  dispatchDeepSeekWeb, hasDeepSeekWebCredential, invalidResponse, isRecord,
  type DeepSeekWebAuth,
} from './transport.ts'

/** Stable id the Fetch API provider registers under in the fetch registry. */
export const DEEPSEEK_FETCH_API_PROVIDER_ID = 'deepseek-fetch-api'

/** Authentication and endpoint settings snapshotted for one fetch. */
export interface DeepSeekFetchApiOptions extends DeepSeekWebAuth {
  /** API base including its path prefix; `/fetch` is appended. */
  baseURL: string
}

/**
 * Fetch page Markdown through the DeepSeek Fetch API. The API reports neither the
 * target's status nor a final URL, and it fails when the target yields no usable
 * content, so a success is the requested page retrieved with HTTP 200.
 */
export class DeepSeekFetchApiProvider implements WebFetchProvider {
  readonly id = DEEPSEEK_FETCH_API_PROVIDER_ID

  /** @param resolveOptions - the options for the NEXT fetch, read once at each fetch's entry. */
  constructor(private readonly resolveOptions: () => DeepSeekFetchApiOptions) {}

  available(): boolean {
    const options = this.resolveOptions()
    return hasDeepSeekWebCredential(options) && URL.canParse(options.baseURL)
  }

  fetch(request: WebFetchRequest, signal?: AbortSignal): Promise<WebFetchResult> {
    const options = this.resolveOptions()
    return dispatchDeepSeekWeb(options, {
      endpoint: `${options.baseURL.replace(/\/+$/u, '')}/fetch`,
      body: { url: request.url },
      decode: (payload): WebFetchResult => {
        if (!isRecord(payload) || typeof payload.content !== 'string') throw invalidResponse()
        return { url: request.url, statusCode: 200, body: { kind: 'text', content: payload.content }, truncated: false }
      },
      guidance: { subject: 'Fetch', ...DEEPSEEK_WEB_API_GUIDANCE },
    }, signal)
  }
}