hospital-log/backend/api/src/modules/proof/proof.service.ts

import {
  Injectable,
  InternalServerErrorException,
  NotFoundException,
} from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { RekammedisService } from '../rekammedis/rekammedis.service';
import { groth16, wtns } from 'snarkjs';
import path from 'path';

@Injectable()
export class ProofService {
  constructor(
    private prismaService: PrismaService,
    private rekamMedisService: RekammedisService,
  ) {}

  buildDir = path.join(__dirname, '../../../', 'dist');
  publicDir = path.join(__dirname, '../../../../', '/api/public');
  wasmPath = path.join(this.publicDir, 'circuit.wasm');
  zkeyPath = path.join(this.publicDir, 'circuit_final.zkey');
  vkeyPath = path.join(this.publicDir, 'verification_key.json');
  witnessPath = path.join(this.buildDir, 'witness.wtns');

  async calculateWitness(age: number) {
    const inputs = {
      age: age,
      threshold: 18,
    };
    await wtns.calculate(inputs, this.wasmPath, this.witnessPath);
  }

  async generateProof() {
    const { proof, publicSignals } = await groth16.prove(
      this.zkeyPath,
      this.witnessPath,
    );
    return { proof, publicSignals };
  }

  async getProof(id_visit: any) {
    const age = await this.rekamMedisService.getAgeByIdVisit(id_visit);
    if (!age) {
      throw new NotFoundException('ID Visit tidak ditemukan');
    }

    try {
      await this.calculateWitness(age);
    } catch (error) {
      console.log('Error during witness calculation:', error);
      throw new InternalServerErrorException(
        "Can't generate proof from input based on constraint. Please check the input data and try again.",
      );
    }

    const { proof, publicSignals } = await this.generateProof();

    return {
      proof: proof,
      publicSignals: publicSignals,
    };
  }
}