apps/backend/src/services/embeddings/LocalGPUEmbeddings.ts

import { spawn, ChildProcess } from 'child_process';
import path from 'path';
import { EmbeddingProvider } from './EmbeddingService.js';
import { logger } from '../../utils/logger.js';

import { fileURLToPath } from 'url';

// ESM/CJS compatible directory logic
const currentDir = typeof import.meta !== 'undefined' && import.meta.url
  ? path.dirname(fileURLToPath(import.meta.url))
  : process.cwd(); // Fallback for CJS if specific __dirname is tricky, usually path.dirname(__filename) but __filename is also issue. 
// Better: assume ESM for this modern app or just use process.cwd() relative path if needed but finding built script is safer.


export class LocalGPUEmbeddingsProvider implements EmbeddingProvider {
  name = 'local-gpu';
  dimensions = 384; // Default for all-MiniLM-L6-v2

  private process: ChildProcess | null = null;
  private isReady: boolean = false;
  private pendingRequests: Map<number, { resolve: (val: any) => void; reject: (err: any) => void }> = new Map();
  private requestCounter: number = 0;
  private cleanup: () => void = () => { }; // Dynamic cleanup callback

  async initialize(): Promise<void> {
    if (this.isReady) return;

    return new Promise((resolve, reject) => {
      try {
        const scriptPath = path.join(currentDir, 'gpu_bridge.py');
        logger.info(`🔌 Starting GPU Bridge: python3 ${scriptPath}`);

        this.process = spawn('python3', [scriptPath]);

        // Handle stdout (Responses)
        this.process.stdout?.on('data', (data) => {
          const lines = data.toString().split('\n');
          for (const line of lines) {
            if (!line.trim()) continue;

            try {
              const response = JSON.parse(line);

              // Initial Ready Signal
              if (response.status === 'ready') {
                logger.info(`🚀 GPU Bridge Ready on device: ${response.device}`);
                this.isReady = true;
                resolve();
                continue;
              }

              // We are using a simple FIFO queue for now since we write/read sequentially
              // For a more robust solution with concurrency, we'd need Request IDs
              // But for this implementation, we assume one request at a time via the Service lock
              // or we rely on the strictly ordered stdio.

              // NOTE: This simplified implementation assumes sequential processing (awaiting each call)
              // which matches the current usage in EmbeddingService.

            } catch (e) {
              logger.error(`GPU Bridge parse error: ${e} [Line: ${line}]`);
            }
          }
        });

        // Handle stderr (Logs)
        this.process.stderr?.on('data', (data) => {
          logger.info(`[GPU-Bridge] ${data.toString().trim()}`);
        });

        this.process.on('error', (err) => {
          logger.error('❌ Failed to start GPU Bridge process:', err);
          reject(err);
        });

        this.process.on('exit', (code) => {
          logger.warn(`⚠️ GPU Bridge process exited with code ${code}`);
          this.isReady = false;
        });

        // Timeout backup
        setTimeout(() => {
          if (!this.isReady) {
            // If it takes too long, we might just be downloading the model (can take time)
            // So we don't reject immediately, but warn.
            logger.warn('⏳ GPU Bridge taking longer than expected (model download?)...');
          }
        }, 10000);

      } catch (error) {
        reject(error);
      }
    });
  }

  // Helper to execute a single request-response cycle
  // Since we are using stdio, we need to be careful about concurrency.
  // Ideally, we wrap this in a mutex, but Node.js is single threaded event loop.
  // We just need to ensure we don't interleave writes before reads are done.
  private async execute<T>(payload: any): Promise<T> {
    if (!this.process || !this.isReady) {
      await this.initialize();
    }

    return new Promise((resolve, reject) => {
      // Simple one-off listener for the next line of output
      // This assumes strictly sequential execution provided by the await in the caller
      const listener = (data: Buffer) => {
        const lines = data.toString().split('\n').filter(l => l.trim());
        for (const line of lines) {
          try {
            const response = JSON.parse(line);
            // Ignore status messages if they appear late
            if (response.status) continue;

            if (response.error) {
              this.cleanup();
              reject(new Error(response.error));
            } else {
              this.cleanup();
              resolve(response);
            }
            return; // Handled
          } catch (e) {
            // partial line? wait for next chunk
          }
        }
      };

      const cleanup = () => {
        this.process?.stdout?.off('data', listener);
        this.cleanup = () => { }; // prevent double call
      };
      // Store cleanup on this scope so the listener callback can call it
      (this as any).cleanup = cleanup;

      this.process!.stdout!.on('data', listener);
      this.process!.stdin!.write(JSON.stringify(payload) + '\n');
    });
  }

  async generateEmbedding(text: string): Promise<number[]> {
    const response = await this.execute<{ embedding: number[] }>({ text });
    return response.embedding;
  }

  async generateEmbeddings(texts: string[]): Promise<number[][]> {
    const response = await this.execute<{ embeddings: number[][] }>({ texts });
    return response.embeddings;
  }
}