import { Injectable, OnModuleInit } from "@nestjs/common";
import { MongoCoreService } from "src/mongo/mongo-core.service";
import { FFBProductionRepository } from "src/mongo/mongo-ffb-production.repository";
import { FFBGateway } from "./ffb.gateway";
import path from "path";
import fs from "fs";
import axios from "axios";
import { GeminiEmbeddingService } from "./gemini-embedding.service";

@Injectable()
export class FFBQueryAgentService implements OnModuleInit {
  private systemPrompt: any;
  private repo: FFBProductionRepository;

  constructor(
    private readonly mongoCore: MongoCoreService,
    private readonly gateway: FFBGateway,
    private readonly embeddingService: GeminiEmbeddingService
  ) { }

  async onModuleInit() {
    const filePath = path.join(process.cwd(), 'QueryAgent.json');
    const data = fs.readFileSync(filePath, 'utf-8');
    this.systemPrompt = JSON.parse(data);
  }

  private buildPrompt(userMessage: string, schemaFields: string[]): string {
    const examplesText = (this.systemPrompt.examples || [])
      .map(
        (ex: any) => `Q: "${ex.question}"\nA: ${JSON.stringify(ex.plan, null, 2)}`
      )
      .join('\n\n');

    return `
${this.systemPrompt.instructions}

Document fields: ${schemaFields.join(", ")}

Always include the minimal "fields" needed for computation to reduce bandwidth.

${examplesText}

Now, given the following user question, output JSON only in the format:
{ "textToBeEmbedded": string, "pipeline": [ ... ], "reasoning": string }

Q: "${userMessage}"
`;
  }


  private async callGemini(prompt: string): Promise<string> {
    const apiKey = process.env.GOOGLE_API_KEY;
    if (!apiKey) throw new Error('Missing GOOGLE_API_KEY');

    const url =
      'https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent';

    const body = { contents: [{ role: 'user', parts: [{ text: prompt }] }] };

    try {
      const response = await axios.post(url, body, {
        headers: { 'Content-Type': 'application/json', 'x-goog-api-key': apiKey },
      });

      const text =
        response.data?.candidates?.[0]?.content?.parts?.map((p: any) => p.text).join(' ') ?? '';
      if (!text) throw new Error('No text generated by Gemini');
      return text;
    } catch (err: any) {
      console.error('Failed to call Gemini:', err.response?.data || err.message);
      throw err;
    }
  }

  private sanitizeLLMOutput(text: string): string {
    let sanitized = text
      .trim()
      .replace(/^```json\s*/, '')
      .replace(/^```\s*/, '')
      .replace(/```$/, '')
      .trim();
    sanitized = sanitized.replace(/ISODate\(["'](.+?)["']\)/g, '"$1"');
    sanitized = sanitized.replace(/"\s*\$/g, '"$');
    return sanitized;
  }

  private parseLLMOutput(sanitized: string): { textToBeEmbedded: string; pipeline: any[], reasoning: string } {
    try {
      const parsed = JSON.parse(sanitized);
      if (!('pipeline' in parsed) || !Array.isArray(parsed.pipeline)) {
        throw new Error('LLM output missing pipeline array');
      }
      return parsed;
    } catch {
      try {
        return eval(`(${sanitized})`);
      } catch (err2) {
        console.error('Failed to parse LLM output even with fallback:', sanitized);
        throw new Error('LLM returned invalid JSON');
      }
    }
  }

  private async getRepo(): Promise<FFBProductionRepository> {
    if (!this.repo) {
      const db = await this.mongoCore.getDb();
      this.repo = new FFBProductionRepository(db);
      await this.repo.init();
    }
    return this.repo;
  }

  /** Main entry point: plan + conditional vector search execution */
  async query(userMessage: string): Promise<any[]> {
    // 0. Get repository first
    const repo = await this.getRepo();

    // 1. Get sample doc to dynamically inject schema fields
    const sampleDoc = await repo.findAll();
    const ffbFields = sampleDoc.length > 0 ? Object.keys(sampleDoc[0]) : [
      "productionDate",
      "site",
      "phase",
      "block",
      "weight",
      "weightUom",
      "quantity",
      "quantityUom"
    ];

    // 2. Build prompt with dynamic schema
    const promptText = this.buildPrompt(userMessage, ffbFields);

    // 3. Call LLM
    const llmResponse = await this.callGemini(promptText);

    // 4. Sanitize + parse
    const sanitized = this.sanitizeLLMOutput(llmResponse);
    const { textToBeEmbedded, pipeline, reasoning } = this.parseLLMOutput(sanitized);

    // 5. If vector search is needed, generate embedding and inject into $vectorSearch
    if (textToBeEmbedded && textToBeEmbedded.trim()) {
      const embedding = await this.embeddingService.embedText(textToBeEmbedded.trim());

      // Ensure $vectorSearch is the first stage in the pipeline
      const vectorStageIndex = pipeline.findIndex(stage => '$vectorSearch' in stage);
      if (vectorStageIndex > -1) {
        pipeline[vectorStageIndex].$vectorSearch.queryVector = embedding;
        if (vectorStageIndex !== 0) {
          // Move $vectorSearch to first stage
          const [vsStage] = pipeline.splice(vectorStageIndex, 1);
          pipeline.unshift(vsStage);
        }
      }
    }

    // 6. Prepare pipeline for frontend display (mask actual vectors)
    const pipelineForSocket = pipeline.map(stage =>
    ('$vectorSearch' in stage
      ? { ...stage, $vectorSearch: { ...stage.$vectorSearch, queryVector: '[VECTOR]' } }
      : stage)
    );

    // 7. Emit pipeline + reasoning
    this.gateway.emitAgentOutput({
      stage: 'pipeline_generated',
      rawLLMOutput: llmResponse,
      pipeline: pipelineForSocket,
      prettyPipeline: JSON.stringify(pipelineForSocket, null, 2),
      textToBeEmbedded,
      reasoning
    });

    // 8. Execute aggregation
    const results = await repo.aggregate(pipeline);

    // 9. Emit execution results
    this.gateway.emitAgentOutput({
      stage: 'pipeline_executed',
      pipeline: pipelineForSocket,
      count: results.length,
      results,
      reasoning
    });

    return results;
  }

}