/**
 * ADR-0027: Alibaba Cloud Document Mind (docmind) client.
 *
 * Uses the official @alicloud/docmind-api20220711 SDK to call the document
 * parsing (large model version) API. The API is asynchronous:
 *   1. SubmitDocParserJobAdvance — upload local file as a stream, get job id
 *   2. QueryDocParserStatus — poll until data.status === "success";
 *      the markdown output URL is returned in outputFormatResult
 *   3. Download markdown from OSS, extract and download referenced images
 *
 * Pricing (2025-07, aliyun docmind):
 *   - 图文文档基础链路: 0.02元/页
 *   - 图文文档增强链路 (含公式 LaTeX): 0.04元/页
 *   - 视频: 0.002元/秒
 *   - 音频: 0.00035元/秒
 */
import $DocmindClient, {
  SubmitDocParserJobAdvanceRequest,
  QueryDocParserStatusRequest,
} from "@alicloud/docmind-api20220711";
import { RuntimeOptions } from "@alicloud/tea-util";
import { createReadStream } from "node:fs";
import { basename } from "node:path";
import type { CapabilitySecretPayload } from "./types.js";

/** A single extracted image downloaded from the markdown's OSS image URLs. */
export interface DocmindExtractedImage {
  readonly filename: string;
  readonly data: Uint8Array;
}

/** The structured result of parsing one document. */
export interface DocmindParseResult {
  readonly markdown: string;
  readonly images: readonly DocmindExtractedImage[];
  readonly pageCount: number;
  readonly costUsd: number | null;
  readonly requestId: string | null;
}

export interface DocmindParseOptions {
  readonly inputFilePath: string;
}

export interface CapabilityProviderClient {
  parse(credential: CapabilitySecretPayload, options: DocmindParseOptions): Promise<DocmindParseResult>;
}

export class DocmindClientError extends Error {
  constructor(
    message: string,
    readonly code: "docmind_unreachable" | "docmind_rejected" | "docmind_invalid_response" | "docmind_no_output" | "docmind_timeout",
    readonly upstreamStatus?: number,
  ) {
    super(message);
    this.name = "DocmindClientError";
  }
}

/** Cost per page in USD (0.04 CNY/page ≈ 0.0056 USD). */
const COST_PER_PAGE_USD = 0.0056;
const POLL_INTERVAL_MS = 10_000;
const POLL_TIMEOUT_MS = 5 * 60_000;

type DocmindConfig = ConstructorParameters<typeof $DocmindClient.default>[0];

export class AliyunDocmindClient implements CapabilityProviderClient {
  async parse(credential: CapabilitySecretPayload, options: DocmindParseOptions): Promise<DocmindParseResult> {
    const config: DocmindConfig = {
      endpoint: credential.endpoint,
      accessKeyId: credential.accessKeyId,
      accessKeySecret: credential.accessKeySecret,
      type: "access_key",
      regionId: "cn-hangzhou",
    } as DocmindConfig;
    const client = new $DocmindClient.default(config);

    // 1. Submit job with local file as a ReadStream (not a Buffer — the SDK
    //    serializes Buffers as JSON {type:"Buffer",data:[...]} which the API
    //    can't read; a Stream is uploaded as multipart form data).
    const fileName = basename(options.inputFilePath);
    const fileStream = createReadStream(options.inputFilePath);
    const advanceRequest = new SubmitDocParserJobAdvanceRequest({
      fileUrlObject: fileStream,
      fileName,
      outputFormat: ["markdown"],
      formulaEnhancement: true,
    });
    const runtime = new RuntimeOptions({});
    let submitResponse;
    try {
      submitResponse = await client.submitDocParserJobAdvance(advanceRequest, runtime);
    } catch (e) {
      throw new DocmindClientError(
        e instanceof Error ? e.message : String(e),
        "docmind_unreachable",
      );
    }
    const jobId = submitResponse.body?.data?.id;
    if (jobId === undefined || jobId === null || jobId === "") {
      throw new DocmindClientError("docmind submit returned no job id", "docmind_invalid_response");
    }

    // 2. Poll QueryDocParserStatus until data.status === "success" or "fail".
    const deadline = Date.now() + POLL_TIMEOUT_MS;
    let status = "";
    let markdownUrl: string | null = null;
    let pageCount = 0;
    while (Date.now() < deadline) {
      await sleep(POLL_INTERVAL_MS);
      const statusReq = new QueryDocParserStatusRequest({ id: jobId });
      const statusResponse = await client.queryDocParserStatus(statusReq);
      const body = statusResponse.body as {
        data?: {
          status?: string;
          pageCountEstimate?: number;
          outputFormatResult?: Array<{ outputFileUrl?: string; outputType?: string }>;
        };
      };
      status = body.data?.status ?? "";
      if (status === "success") {
        const mdResult = body.data?.outputFormatResult?.find((r) => r.outputType === "markdown");
        markdownUrl = mdResult?.outputFileUrl ?? null;
        pageCount = body.data?.pageCountEstimate ?? 0;
        break;
      }
      if (status === "fail") {
        throw new DocmindClientError(`docmind job ${jobId} failed`, "docmind_rejected");
      }
    }
    if (status !== "success") {
      throw new DocmindClientError(`docmind job ${jobId} timed out (status: ${status})`, "docmind_timeout");
    }
    if (markdownUrl === null) {
      throw new DocmindClientError("docmind returned no markdown output URL", "docmind_no_output");
    }

    // 3. Download the markdown file from OSS.
    let markdown: string;
    try {
      const mdResp = await fetch(markdownUrl);
      if (!mdResp.ok) {
        throw new DocmindClientError(`failed to download markdown: HTTP ${mdResp.status}`, "docmind_unreachable");
      }
      markdown = await mdResp.text();
    } catch (e) {
      if (e instanceof DocmindClientError) throw e;
      throw new DocmindClientError(
        e instanceof Error ? e.message : String(e),
        "docmind_unreachable",
      );
    }
    if (markdown === "") {
      throw new DocmindClientError("docmind returned empty markdown", "docmind_no_output");
    }

    // 4. Download images referenced in the markdown (OSS URLs).
    //    Markdown contains ![filename](http://...oss.../image.png?...) entries.
    //    We rewrite them to local relative paths and download the images.
    const images: DocmindExtractedImage[] = [];
    const imageRefRegex = /!\[([^\]]*)\]\((https?:\/\/[^)]+)\)/g;
    const localMarkdown = markdown.replace(imageRefRegex, (match, altText: string, url: string) => {
      const idx = images.findIndex((img) => img.filename === extractFilename(altText, url, images.length));
      if (idx >= 0) {
        const img = images[idx]!;
        return `![${altText}](${img.filename})`;
      }
      return match;
    });

    // Collect all image URLs first, then download.
    const imageUrls: Array<{ url: string; altText: string }> = [];
    let match: RegExpExecArray | null;
    const collectRegex = /!\[([^\]]*)\]\((https?:\/\/[^)]+)\)/g;
    while ((match = collectRegex.exec(markdown)) !== null) {
      imageUrls.push({ url: match[2]!, altText: match[1]! });
    }

    for (let i = 0; i < imageUrls.length; i++) {
      const { url, altText } = imageUrls[i]!;
      const filename = extractFilename(altText, url, i);
      try {
        const imgResp = await fetch(url);
        if (!imgResp.ok) continue;
        const data = new Uint8Array(await imgResp.arrayBuffer());
        images.push({ filename, data });
      } catch {
        // Best-effort: skip images that fail to download.
      }
    }

    // Rewrite markdown with local image paths.
    let finalMarkdown = markdown;
    let imageIdx = 0;
    finalMarkdown = finalMarkdown.replace(imageRefRegex, (match, altText: string, _url: string) => {
      if (imageIdx < images.length) {
        const img = images[imageIdx]!;
        imageIdx++;
        return `![${altText}](${img.filename})`;
      }
      return match;
    });

    if (pageCount === 0) {
      pageCount = Math.max(1, images.length);
    }
    const costUsd = (pageCount > 0 ? pageCount : 1) * COST_PER_PAGE_USD;

    return { markdown: finalMarkdown, images, pageCount, costUsd, requestId: jobId };
  }
}

function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => {
    setTimeout(resolve, ms);
  });
}

/** Derive a clean filename from the alt text or URL. */
function extractFilename(altText: string, url: string, index: number): string {
  // Try alt text first (docmind often puts the original filename).
  if (altText !== "" && altText.length < 100) {
    const cleaned = altText.replace(/[^a-zA-Z0-9._-]/g, "_");
    if (cleaned.length > 0) return cleaned;
  }
  // Fall back to URL path.
  const urlPath = new URL(url).pathname;
  const base = basename(urlPath);
  if (base !== "" && base !== "/") return base;
  return `image_${index + 1}.png`;
}