// Cross-Chain Verification Service (CCVL)
// Chain header validation
// Sovereign signature verification
// Hash commitment verification
// Multi-chain consensus

import prisma from '@/shared/database/prisma';
import { v4 as uuidv4 } from 'uuid';
import { createHash } from 'crypto';


export interface ChainHeaderRequest {
  chainType: string;
  chainId: string;
  blockNumber?: string;
  blockHash: string;
  previousBlockHash?: string;
  timestamp: Date;
}

export class CrossChainVerificationService {
  /**
   * Verify chain header (CCVL)
   */
  async verifyChainHeader(
    header: ChainHeaderRequest,
    settlementId: string
  ): Promise<boolean> {
    // Create chain header record
    const headerId = `CH-${uuidv4()}`;

    const chainHeader = await prisma.chainHeader.create({
      data: {
        headerId,
        settlementId,
        chainType: header.chainType,
        chainId: header.chainId,
        blockNumber: header.blockNumber || null,
        blockHash: header.blockHash,
        previousBlockHash: header.previousBlockHash || null,
        timestamp: header.timestamp,
        verificationStatus: 'pending',
      },
    });

    // Verify chain header
    const isValid = await this.validateChainHeader(chainHeader.headerId);

    // Update verification status
    await prisma.chainHeader.update({
      where: { headerId },
      data: {
        verificationStatus: isValid ? 'verified' : 'rejected',
        verifiedAt: isValid ? new Date() : null,
      },
    });

    return isValid;
  }

  /**
   * Validate chain header
   */
  private async validateChainHeader(headerId: string): Promise<boolean> {
    const header = await prisma.chainHeader.findUnique({
      where: { headerId },
    });

    if (!header) {
      return false;
    }

    // Verify block hash
    const expectedHash = this.calculateBlockHash(header);
    if (header.blockHash !== expectedHash) {
      return false;
    }

    // Verify chain linkage (if previous block exists)
    if (header.previousBlockHash) {
      const previousHeader = await prisma.chainHeader.findFirst({
        where: {
          chainType: header.chainType,
          chainId: header.chainId,
          blockHash: header.previousBlockHash,
        },
      });

      if (!previousHeader) {
        return false;
      }
    }

    return true;
  }

  /**
   * Calculate block hash
   */
  private calculateBlockHash(header: any): string {
    const data = {
      chainType: header.chainType,
      chainId: header.chainId,
      blockNumber: header.blockNumber,
      previousBlockHash: header.previousBlockHash,
      timestamp: header.timestamp.toISOString(),
    };

    return createHash('sha3-256')
      .update(JSON.stringify(data))
      .digest('hex');
  }

  /**
   * Verify sovereign signature
   */
  async verifySovereignSignature(
    chainId: string,
    signature: string,
    data: string
  ): Promise<boolean> {
    // In production, this would verify against HSM-stored keys
    // For now, verify signature exists
    if (!signature) {
      return false;
    }

    // Get sovereign identity
    const identity = await prisma.sovereignIdentity.findFirst({
      where: {
        identityType: 'Settlement',
        status: 'active',
      },
    });

    return !!identity;
  }

  /**
   * Verify hash commitment
   */
  async verifyHashCommitment(
    commitmentHash: string,
    data: Record<string, unknown>
  ): Promise<boolean> {
    const dataString = JSON.stringify(data);
    const expectedHash = createHash('sha3-256')
      .update(dataString)
      .digest('hex');

    return commitmentHash === expectedHash;
  }

  /**
   * Verify multi-chain consensus
   */
  async verifyMultiChainConsensus(
    settlementId: string
  ): Promise<boolean> {
    // Get all chain headers for settlement
    const headers = await prisma.chainHeader.findMany({
      where: {
        settlementId,
      },
    });

    if (headers.length === 0) {
      return false;
    }

    // Verify all headers are verified
    const allVerified = headers.every(
      (h) => h.verificationStatus === 'verified'
    );

    return allVerified;
  }

  /**
   * Get chain headers for settlement
   */
  async getChainHeaders(settlementId: string) {
    return await prisma.chainHeader.findMany({
      where: { settlementId },
    });
  }
}

export const crossChainVerificationService = new CrossChainVerificationService();

