ShieldAI/packages/api/src/services/voiceprint/embedding.service.ts

import { spawn } from "child_process";
import { logger } from './logger';
import { voicePrintEnv } from './voiceprint.config';

const EMBEDDING_DIM = 192;
const MODEL_VERSION = "ecapa-tdnn-0.1.0-mock";

export class EmbeddingService {
  private mlServiceUrl: string;
  private initialized = false;

  constructor() {
    this.mlServiceUrl = process.env.VOICEPRINT_ML_URL || "http://localhost:8001";
  }

  async initialize(): Promise<void> {
    if (this.initialized) return;
    this.initialized = true;
    logger.info('Embedding service initialized', { mlUrl: this.mlServiceUrl, modelVersion: MODEL_VERSION });
  }

  async extract(audioBuffer: Buffer): Promise<number[]> {
    await this.initialize();
    
    const mlAvailable = await this.checkMLService();
    if (mlAvailable) {
      logger.info('Using ML service for embedding', { mlUrl: this.mlServiceUrl });
      return this.extractViaML(audioBuffer);
    }

    logger.info('Using mock embedding generation', { audioBufferLength: audioBuffer.length });
    return this.generateMockFromBuffer(audioBuffer);
  }

  async analyze(audioBuffer: Buffer): Promise<{
    confidence: number;
    detectionType: string;
    features: Record<string, number>;
    embedding: number[];
  }> {
    const embedding = await this.extract(audioBuffer);
    const confidence = this.estimateSyntheticConfidence(audioBuffer, embedding);
    const detectionType = confidence >= voicePrintEnv.SYNTHETIC_THRESHOLD ? 'synthetic_voice' : 'natural';
    const features = this.extractAnalysisFeatures(audioBuffer, embedding);

    return { confidence, detectionType, features, embedding };
  }

  getModelVersion(): string {
    return MODEL_VERSION;
  }

  private async extractViaML(audioBuffer: Buffer): Promise<number[]> {
    return new Promise((resolve, reject) => {
      const jsonInput = audioBuffer.toString("base64");
      const proc = spawn("python3", [
        "-c",
        `
import urllib.request, json, sys
req = urllib.request.Request(
    "${this.mlServiceUrl}/embedding",
    data=json.dumps({"audio": "${jsonInput.substring(0, 5000)}"}).encode(),
    headers={"Content-Type": "application/json"}
)
try:
    with urllib.request.urlopen(req, timeout=60) as resp:
        data = json.loads(resp.read())
        sys.stdout.write(json.dumps({"ok": True, "vector": data.get("embedding", []), "dim": data.get("dimension", ${EMBEDDING_DIM})}))
except Exception as e:
    sys.stdout.write(json.dumps({"ok": False, "error": str(e)}))
`,
      ]);

      let output = "";
      proc.stdout.on("data", (chunk) => { output += chunk.toString(); });
      proc.on("close", (code) => {
        try {
          const result = JSON.parse(output);
          if (result.ok && result.vector && result.vector.length === EMBEDDING_DIM) {
            resolve(result.vector);
          } else {
            resolve(this.generateMockFromBuffer(audioBuffer));
          }
        } catch {
          resolve(this.generateMockFromBuffer(audioBuffer));
        }
      });
    });
  }

  private generateMockFromBuffer(audioBuffer: Buffer): number[] {
    let hash = 0;
    const sampleSize = Math.min(audioBuffer.length, 1024);
    for (let i = 0; i < sampleSize; i += 4) {
      hash = ((hash << 5) - hash + audioBuffer.readInt32LE(i)) | 0;
    }
    const seed = Math.abs(hash);
    
    const rng = this.createRNG(seed);
    const vector: number[] = [];

    // Box-Muller transform for Gaussian distribution
    for (let i = 0; i < EMBEDDING_DIM; i += 2) {
      const u1 = rng();
      const u2 = rng();
      const mag = Math.sqrt(-2 * Math.log(u1));
      const z0 = mag * Math.cos(2 * Math.PI * u2);
      const z1 = mag * Math.sin(2 * Math.PI * u2);
      vector.push(parseFloat(z0.toFixed(6)));
      if (i + 1 < EMBEDDING_DIM) {
        vector.push(parseFloat(z1.toFixed(6)));
      }
    }

    // L2 normalize
    const norm = Math.sqrt(vector.reduce((s, v) => s + v * v, 0));
    return vector.map((v) => parseFloat((v / norm).toFixed(6)));
  }

  private estimateSyntheticConfidence(buffer: Buffer, embedding: number[]): number {
    const meanAmplitude = buffer.reduce((s, v) => s + v, 0) / buffer.length / 255;
    const meanEmbedding = embedding.reduce((s, v) => s + v, 0) / embedding.length;
    const embeddingStdDev = Math.sqrt(embedding.reduce((s, v) => s + (v - meanEmbedding) ** 2, 0) / embedding.length);

    const amplitudeScore = Math.abs(meanAmplitude - 0.5) * 2;
    const embeddingScore = 1.0 - Math.min(1.0, embeddingStdDev * 2);
    const varianceScore = Math.min(1.0, buffer.length / 10000);

    return Math.min(1.0, amplitudeScore * 0.3 + embeddingScore * 0.4 + varianceScore * 0.3);
  }

  private extractAnalysisFeatures(buffer: Buffer, embedding: number[]): Record<string, number> {
    const meanAmplitude = buffer.reduce((s, v) => s + v, 0) / buffer.length / 255;
    const zeroCrossings = buffer.reduce((count, v, i, arr) => {
      return i > 0 && ((v - 128) * (arr[i - 1] - 128) < 0) ? count + 1 : count;
    }, 0);

    return {
      mean_amplitude: meanAmplitude,
      zero_crossing_rate: zeroCrossings / buffer.length,
      embedding_energy: embedding.reduce((s, v) => s + v * v, 0),
      embedding_entropy: this.calculateEntropy(embedding),
    };
  }

  private calculateEntropy(values: number[]): number {
    const bins = 20;
    const histogram = new Array(bins).fill(0);
    const min = Math.min(...values);
    const max = Math.max(...values);
    const range = max - min || 1;

    for (const v of values) {
      const bin = Math.min(bins - 1, Math.floor(((v - min) / range) * bins));
      histogram[bin]++;
    }

    let entropy = 0;
    const total = values.length;
    for (const count of histogram) {
      if (count > 0) {
        const p = count / total;
        entropy -= p * Math.log2(p);
      }
    }
    return entropy;
  }

  private async checkMLService(): Promise<boolean> {
    return new Promise((resolve) => {
      const proc = spawn("python3", [
        "-c",
        `
import urllib.request, sys
try:
    urllib.request.urlopen("${this.mlServiceUrl}/health", timeout=2)
    sys.exit(0)
except:
    sys.exit(1)
`,
      ]);
      proc.on("close", (code) => resolve(code === 0));
    });
  }

  private createRNG(seed: number): () => number {
    return () => {
      seed = (seed * 1664525 + 1013904223) & 0xffffffff;
      return (seed >>> 0) / 0xffffffff;
    };
  }
}