import { Injectable, inject } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import { catchError, map } from 'rxjs/operators';

// 支付凭证识别结果接口
export interface PaymentVoucherRecognitionResult {
  success: boolean;
  amount?: number;
  paymentDate?: Date;
  paymentMethod?: string;
  payerName?: string;
  payerAccount?: string;
  receiverName?: string;
  receiverAccount?: string;
  transactionNumber?: string;
  confidence: number;
  extractedText?: string;
  error?: string;
}

// 支付凭证文件信息接口
export interface PaymentVoucherFile {
  id: string;
  fileName: string;
  fileType: string;
  fileSize: number;
  fileUrl: string;
  previewUrl?: string;
  uploadDate: Date;
}

@Injectable({
  providedIn: 'root'
})
export class PaymentVoucherRecognitionService {
  private http = inject(HttpClient);

  /**
   * 识别支付凭证图片或PDF文件
   * @param file 支付凭证文件
   * @returns 识别结果的可观察对象
   */
  recognizePaymentVoucher(file: File): Observable<PaymentVoucherRecognitionResult> {
    // 检查文件类型
    if (!this.isSupportedFileType(file.type)) {
      return of({
        success: false,
        confidence: 0,
        error: '不支持的文件类型。请上传图片(JPG, PNG, GIF)或PDF文件。'
      });
    }

    // 检查文件大小（限制为10MB）
    if (file.size > 10 * 1024 * 1024) {
      return of({
        success: false,
        confidence: 0,
        error: '文件大小不能超过10MB。'
      });
    }

    // 在实际应用中，这里会调用OCR API服务
    // 目前先模拟识别过程
    return this.simulateRecognition(file);
  }

  /**
   * 批量识别支付凭证
   * @param files 支付凭证文件数组
   * @returns 批量识别结果的可观察对象
   */
  async recognizePaymentVouchers(files: File[]): Promise<PaymentVoucherRecognitionResult[]> {
    const recognitionPromises = files.map(file => 
      this.recognizePaymentVoucher(file).toPromise()
    );

    const results = await Promise.all(recognitionPromises);
    return results.filter(result => result !== undefined) as PaymentVoucherRecognitionResult[];
  }

  /**
   * 检查是否支持的文件类型
   * @param fileType 文件MIME类型
   */
  private isSupportedFileType(fileType: string): boolean {
    const supportedTypes = [
      'image/jpeg',
      'image/png', 
      'image/gif',
      'application/pdf'
    ];
    return supportedTypes.includes(fileType);
  }

  /**
   * 模拟支付凭证识别过程
   * @param file 支付凭证文件
   */
  private simulateRecognition(file: File): Observable<PaymentVoucherRecognitionResult> {
    return new Observable(observer => {
      // 模拟处理延迟
      setTimeout(() => {
        try {
          // 根据文件名和类型生成模拟识别结果
          const fileName = file.name.toLowerCase();
          
          // 模拟不同的识别场景
          if (fileName.includes('alipay') || fileName.includes('支付宝')) {
            observer.next(this.generateAlipayResult(file));
          } else if (fileName.includes('wechat') || fileName.includes('微信')) {
            observer.next(this.generateWechatResult(file));
          } else if (fileName.includes('bank') || fileName.includes('银行')) {
            observer.next(this.generateBankTransferResult(file));
          } else {
            observer.next(this.generateGenericResult(file));
          }
          
          observer.complete();
        } catch (error) {
          observer.next({
            success: false,
            confidence: 0,
            error: `识别过程中发生错误: ${error}`
          });
          observer.complete();
        }
      }, 2000); // 2秒延迟模拟处理时间
    });
  }

  /**
   * 生成支付宝支付凭证识别结果
   */
  private generateAlipayResult(file: File): PaymentVoucherRecognitionResult {
    const amount = Math.round(Math.random() * 10000 + 1000); // 1000-11000之间的随机金额
    const confidence = Math.random() * 0.3 + 0.7; // 70%-100%的置信度
    
    return {
      success: true,
      amount,
      paymentDate: new Date(),
      paymentMethod: '支付宝',
      payerName: '付款人***',
      payerAccount: 'alipay***@xxx.com',
      receiverName: '收款人***',
      receiverAccount: 'alipay***@xxx.com',
      transactionNumber: `ALP${Date.now().toString().slice(-8)}`,
      confidence,
      extractedText: `支付宝交易凭证 金额: ${amount}元 交易时间: ${new Date().toLocaleString()}`
    };
  }

  /**
   * 生成微信支付凭证识别结果
   */
  private generateWechatResult(file: File): PaymentVoucherRecognitionResult {
    const amount = Math.round(Math.random() * 5000 + 500); // 500-5500之间的随机金额
    const confidence = Math.random() * 0.3 + 0.7; // 70%-100%的置信度
    
    return {
      success: true,
      amount,
      paymentDate: new Date(),
      paymentMethod: '微信支付',
      payerName: '微信用户***',
      payerAccount: 'wxid_***',
      receiverName: '商户***',
      receiverAccount: 'mch_***',
      transactionNumber: `WX${Date.now().toString().slice(-8)}`,
      confidence,
      extractedText: `微信支付凭证 金额: ${amount}元 交易时间: ${new Date().toLocaleString()}`
    };
  }

  /**
   * 生成银行转账凭证识别结果
   */
  private generateBankTransferResult(file: File): PaymentVoucherRecognitionResult {
    const amount = Math.round(Math.random() * 20000 + 2000); // 2000-22000之间的随机金额
    const confidence = Math.random() * 0.2 + 0.8; // 80%-100%的置信度
    
    return {
      success: true,
      amount,
      paymentDate: new Date(),
      paymentMethod: '银行转账',
      payerName: '付款人***',
      payerAccount: '6222********1234',
      receiverName: '收款人***',
      receiverAccount: '6222********5678',
      transactionNumber: `BANK${Date.now().toString().slice(-8)}`,
      confidence,
      extractedText: `银行转账凭证 金额: ${amount}元 交易时间: ${new Date().toLocaleString()}`
    };
  }

  /**
   * 生成通用支付凭证识别结果
   */
  private generateGenericResult(file: File): PaymentVoucherRecognitionResult {
    const amount = Math.round(Math.random() * 15000 + 1000); // 1000-16000之间的随机金额
    const confidence = Math.random() * 0.4 + 0.6; // 60%-100%的置信度
    
    const methods = ['支付宝', '微信支付', '银行转账', '现金'];
    const paymentMethod = methods[Math.floor(Math.random() * methods.length)];
    
    return {
      success: true,
      amount,
      paymentDate: new Date(),
      paymentMethod,
      payerName: '付款人***',
      receiverName: '收款人***',
      confidence,
      extractedText: `支付凭证 金额: ${amount}元 支付方式: ${paymentMethod} 交易时间: ${new Date().toLocaleString()}`
    };
  }

  /**
   * 验证识别结果的可信度
   * @param result 识别结果
   * @param expectedAmount 预期金额（可选）
   */
  validateRecognitionResult(
    result: PaymentVoucherRecognitionResult, 
    expectedAmount?: number
  ): { isValid: boolean; reasons: string[] } {
    const reasons: string[] = [];
    
    if (!result.success) {
      reasons.push('识别失败');
      return { isValid: false, reasons };
    }
    
    if (result.confidence < 0.7) {
      reasons.push(`置信度过低: ${(result.confidence * 100).toFixed(1)}%`);
    }
    
    if (!result.amount || result.amount <= 0) {
      reasons.push('金额识别无效');
    }
    
    if (expectedAmount && result.amount && Math.abs(result.amount - expectedAmount) > expectedAmount * 0.1) {
      reasons.push(`识别金额与预期金额差异过大`);
    }
    
    if (!result.paymentDate) {
      reasons.push('支付日期识别失败');
    }
    
    if (!result.paymentMethod) {
      reasons.push('支付方式识别失败');
    }
    
    return {
      isValid: reasons.length === 0,
      reasons
    };
  }

  /**
   * 格式化金额显示
   * @param amount 金额
   */
  formatAmount(amount: number): string {
    return new Intl.NumberFormat('zh-CN', {
      style: 'currency',
      currency: 'CNY'
    }).format(amount);
  }

  /**
   * 获取支持的文件类型描述
   */
  getSupportedFileTypesDescription(): string {
    return '支持的文件类型: JPG, PNG, GIF图片或PDF文件，最大10MB';
  }

  /**
   * 获取支持的文件类型列表
   */
  getSupportedFileTypes(): string[] {
    return [
      'image/jpeg',
      'image/png', 
      'image/gif',
      'application/pdf'
    ];
  }

  /**
   * 验证文件
   * @param file 要验证的文件
   */
  validateFile(file: File): { isValid: boolean; error?: string } {
    if (!this.isSupportedFileType(file.type)) {
      return {
        isValid: false,
        error: '不支持的文件类型。请上传图片(JPG, PNG, GIF)或PDF文件。'
      };
    }

    if (file.size > 10 * 1024 * 1024) {
      return {
        isValid: false,
        error: '文件大小不能超过10MB。'
      };
    }

    return { isValid: true };
  }
}