export function getApiHeaders(): Record<string, string> {
  const saved = localStorage.getItem("patent_api_settings");
  if (!saved) return {};
  try {
    const settings = JSON.parse(saved);
    if (settings) {
      return {
        "x-user-api-provider": settings.defaultProvider || settings.provider || "gemini",
        "x-user-gemini-api-key": settings.geminiApiKey || "",
        "x-user-gemini-model": settings.geminiModel || "",
        "x-user-deepseek-api-key": settings.deepseekApiKey || "",
        "x-user-deepseek-base-url": settings.deepseekBaseUrl || "",
        "x-user-deepseek-model": settings.deepseekModel || "",
        // Backward compatibility
        "x-user-api-key": settings.apiKey || "",
        "x-user-api-base-url": settings.baseUrl || "",
        "x-user-api-model": settings.model || "",
      };
    }
  } catch (e) {
    console.error("Failed to load custom API settings", e);
  }
  return {};
}

export async function customFetch(input: RequestInfo | URL, init?: RequestInit & { timeout?: number }): Promise<Response> {
  const url = typeof input === "string" ? input : (input instanceof URL ? input.href : (input && "url" in input ? input.url : ""));
  
  const timeoutMs = init?.timeout ?? (url.includes("/api/") ? 40000 : undefined);
  
  let controller: AbortController | null = null;
  let timeoutId: any = null;
  
  if (timeoutMs) {
    controller = new AbortController();
    timeoutId = setTimeout(() => {
      if (controller) controller.abort();
    }, timeoutMs);
    init = init || {};
    init.signal = controller.signal;
  }
  
  if (url.includes("/api/")) {
    const customHeaders = getApiHeaders();
    if (Object.keys(customHeaders).length > 0) {
      init = init || {};
      const newHeaders = new Headers(init.headers || {});
      Object.entries(customHeaders).forEach(([key, val]) => {
        if (val) {
          newHeaders.set(key, val);
        }
      });
      init.headers = newHeaders;
    }
  }
  
  try {
    const response = await fetch(input, init);
    if (timeoutId) clearTimeout(timeoutId);
    return response;
  } catch (error: any) {
    if (timeoutId) clearTimeout(timeoutId);
    if (error.name === "AbortError") {
      throw new Error("请求超时：AI 接口响应时间过长。请稍后重试，或检查页面右上角「API设置」以配置更稳定的专属 API Key。");
    }
    throw error;
  }
}

/**
 * Parses PDF files entirely in the client browser using pdfjs-dist via CDN.
 * This completely avoids sending large binary files through the reverse proxy,
 * bypassing any "413 Request Entity Too Large" errors.
 */
export async function parsePdfClient(file: File): Promise<string> {
  return new Promise((resolve, reject) => {
    const executeParsing = async () => {
      try {
        const pdfjsLib = (window as any).pdfjsLib;
        if (!pdfjsLib) {
          throw new Error("浏览器中未加载 pdfjsLib 组件");
        }
        
        // Use matching worker CDN link
        pdfjsLib.GlobalWorkerOptions.workerSrc = "https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js";
        
        const arrayBuffer = await file.arrayBuffer();
        const loadingTask = pdfjsLib.getDocument({ data: arrayBuffer });
        const pdfDoc = await loadingTask.promise;
        
        let textContent = "";
        for (let i = 1; i <= pdfDoc.numPages; i++) {
          const page = await pdfDoc.getPage(i);
          const textObj = await page.getTextContent();
          const pageText = textObj.items
            .map((item: any) => item.str)
            .join(" ");
          textContent += pageText + "\n";
        }
        
        if (textContent.trim().length < 5) {
          throw new Error("未在 PDF 中提取到有效文本。该文件可能为扫描件、图片、或已加密。建议在页面右上角「API设置」中配置您个人的专属 Google Gemini Key 启用多模态 OCR 识别，或直接复制文本发送。");
        }
        
        resolve(textContent);
      } catch (err: any) {
        reject(err);
      }
    };

    if ((window as any).pdfjsLib) {
      executeParsing();
    } else {
      const script = document.createElement("script");
      script.src = "https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js";
      script.onload = () => {
        executeParsing();
      };
      script.onerror = () => {
        reject(new Error("加载在线 PDF 解析组件失败，请检查您的网络。"));
      };
      document.head.appendChild(script);
    }
  });
}

/**
 * Parses DOCX files entirely in the client browser using mammoth.js via CDN.
 */
export async function parseDocxClient(file: File): Promise<string> {
  return new Promise((resolve, reject) => {
    const executeParsing = async () => {
      try {
        const mammoth = (window as any).mammoth;
        if (!mammoth) {
          throw new Error("浏览器中未加载 mammoth 组件");
        }
        const arrayBuffer = await file.arrayBuffer();
        const result = await mammoth.extractRawText({ arrayBuffer });
        if (result.value && result.value.trim().length > 0) {
          resolve(result.value);
        } else {
          throw new Error("Word 文档中未提取到有效文本");
        }
      } catch (err: any) {
        reject(err);
      }
    };

    if ((window as any).mammoth) {
      executeParsing();
    } else {
      const script = document.createElement("script");
      script.src = "https://cdnjs.cloudflare.com/ajax/libs/mammoth/1.6.0/mammoth.browser.min.js";
      script.onload = () => {
        executeParsing();
      };
      script.onerror = () => {
        reject(new Error("加载在线 Word 解析组件失败，请检查您的网络。"));
      };
      document.head.appendChild(script);
    }
  });
}