/**
 * ════════════════════════════════════════════════════════════
 * مُصادَق (Musadaq) — Gemini AI Extraction Service
 * ════════════════════════════════════════════════════════════
 * يقوم باستخراج البيانات من صور/ملفات الفواتير باستخدام Gemini.
 * يضمن تحويل البيانات غير المهيكلة إلى JSON مطابق لمعايير UBL 2.1.
 * ════════════════════════════════════════════════════════════
 */

import { Injectable, Logger, InternalServerErrorException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { GoogleGenerativeAI } from '@google/generative-ai';
import * as fs from 'fs';
import * as path from 'path';

@Injectable()
export class GeminiExtractorService {
  private readonly logger = new Logger(GeminiExtractorService.name);
  private genAI: GoogleGenerativeAI;
  private model: any;

  constructor(private configService: ConfigService) {
    const apiKey = this.configService.getOrThrow<string>('GEMINI_API_KEY');
    this.genAI = new GoogleGenerativeAI(apiKey);
    this.model = this.genAI.getGenerativeModel({
      model: this.configService.get<string>('GEMINI_MODEL', 'gemini-1.5-flash'),
    });
  }

  /**
   * استخراج البيانات من صورة الفاتورة (يدعم فواتير متعددة في ملف واحد)
   */
  async extractInvoiceData(filePath: string, storageRoot: string): Promise<any> {
    try {
      const fullPath = path.join(storageRoot, filePath);
      const fileData = fs.readFileSync(fullPath);

      const prompt = `
        You are a Jordanian tax expert. Extract all details from this file (image or PDF). 
        The file may contain ONE or MULTIPLE distinct invoices. 
        Extract EACH invoice separately.
        
        The output MUST be a strict JSON object with this schema:
        {
          "invoices": [
            {
              "invoice_number": "string",
              "invoice_date": "YYYY-MM-DD",
              "invoice_type": "cash" | "credit",
              "invoice_category": "standard" | "simplified", 
              "supplier_name": "string",
              "supplier_tin": "string (10 digits)",
              "buyer_name": "string (optional)",
              "buyer_tin": "string (optional)",
              "subtotal": number (before discount and tax),
              "discount_total": number (total discount),
              "tax_amount": number (total tax),
              "grand_total": number (final amount),
              "currency_code": "JOD",
              "lines": [
                {
                  "line_number": number,
                  "description": "string",
                  "quantity": number,
                  "unit_price": number,
                  "discount": number,
                  "tax_rate": number (e.g. 0.16 for 16%),
                  "line_total": number (quantity * unit_price - discount)
                }
              ]
            }
          ]
        }

        JoFotara Specific Rules:
        - invoice_category: "simplified" if the buyer is a regular person (no TIN), "standard" if B2B (buyer has TIN).
        - Prices in Jordan (JOD) often have 3 decimal places (e.g. 2.800).
        - Standard VAT Rate: 0.16 (16%)
        - The formula MUST hold: Subtotal - Discount + Tax = Grand Total.
        - If multiple invoices are in the PDF, ensure the "invoices" array contains all of them.
        
        Return ONLY the JSON. No markdown formatting.
      `;

      // Detect MIME type based on extension
      const ext = path.extname(filePath).toLowerCase();
      let mimeType = 'image/jpeg';
      if (ext === '.pdf') mimeType = 'application/pdf';
      else if (ext === '.png') mimeType = 'image/png';
      else if (ext === '.webp') mimeType = 'image/webp';

      const result = await this.model.generateContent([
        prompt,
        {
          inlineData: {
            data: fileData.toString('base64'),
            mimeType: mimeType,
          },
        },
      ]);

      const responseText = result.response.text();
      // Clean up markdown if any
      const cleanedJson = responseText.replace(/```json|```/g, '').trim();

      const data = JSON.parse(cleanedJson);
      return data.invoices || [];
    } catch (error: any) {
      this.logger.error(\`AI Extraction failed: \${error.message}\`);
      throw new InternalServerErrorException('AI Extraction failed');
    }
  }
}