// Certificate NFT Service
// Handles interactions with Aurora certification NFTs on the Stellar blockchain

// Note: Real blockchain integration will require proper Stellar SDK imports
// For now, we're using mock data to demonstrate the functionality

import logger from "@/lib/logger";

// Aurora Certification NFT Contract Address
const AURORA_CERT_CONTRACT = "CAE3EUNCU6XA7KH4XYPSIA6TYPUQQYVGPGSBUFOHO2KEIGCP";

class CertificateService {
  constructor() {
    // Initialize server only when needed for real blockchain integration
    // For now, we'll use mock data so we don't need the server
    this.server = null;
  }

  // Fetch all certificates owned by a wallet address
  async fetchUserCertificates(walletAddress) {
    try {
      // Validate wallet address
      if (!walletAddress || typeof walletAddress !== "string") {
        throw new Error("Invalid wallet address");
      }
      logger.info("Fetching certificates for wallet", { walletAddress });
      // TODO: Replace mock implementation with actual Stellar blockchain queries  
      // In a real implementation, this would query the blockchain
      // For now, we'll return mock data
      const mockCertificates = [
        {
          id: 1,
          tokenId: "1",
          level: "A1",
          title: "A1 English Certification",
          description: "Beginner level English proficiency certification",
          issueDate: "2024-01-15",
          imageUrl:
            "https://images.unsplash.com/photo-1507003211169-0a1dd7228f2d?w=400&h=300&fit=crop",
          metadata: {
            courseType: "Beginner",
            completionDate: "2024-01-15",
            score: 85,
            totalHours: 120,
            skills: ["Basic Grammar", "Vocabulary", "Speaking", "Listening"],
            issuer: "Aurora Learning Platform",
            blockchainTx: "tx_hash_123456789",
          },
          contractAddress: AURORA_CERT_CONTRACT,
          verified: true,
        },
        {
          id: 2,
          tokenId: "2",
          level: "B2",
          title: "B2 English Certification",
          description:
            "Upper-intermediate level English proficiency certification",
          issueDate: "2024-03-20",
          imageUrl:
            "https://images.unsplash.com/photo-1516321318423-f06f85e504b3?w=400&h=300&fit=crop",
          metadata: {
            courseType: "Intermediate",
            completionDate: "2024-03-20",
            score: 92,
            totalHours: 200,
            skills: [
              "Advanced Grammar",
              "Business English",
              "Academic Writing",
              "Presentation Skills",
            ],
            issuer: "Aurora Learning Platform",
            blockchainTx: "tx_hash_987654321",
          },
          contractAddress: AURORA_CERT_CONTRACT,
          verified: true,
        },
      ];

      // Simulate network delay
      await new Promise((resolve) => setTimeout(resolve, 1000));

      return mockCertificates;
    } catch (error) {
      console.error("Error fetching certificates:", error);
      throw new Error("Failed to fetch certificates from blockchain");
    }
  }

  // Verify certificate ownership on blockchain
  async verifyCertificateOwnership(walletAddress, tokenId) {
    try {
      logger.info("Verifying certificate ownership", {
        walletAddress,
        tokenId,
      });

      // In a real implementation, this would query the NFT contract
      // to verify ownership
      const mockVerification = {
        isOwner: true,
        tokenId,
        contractAddress: AURORA_CERT_CONTRACT,
        verificationDate: new Date().toISOString(),
        blockchainProof: `proof_${tokenId}_${Date.now()}`,
      };

      // Simulate verification delay
      await new Promise((resolve) => setTimeout(resolve, 500));

      return mockVerification;
    } catch (error) {
      console.error("Error verifying certificate ownership:", error);
      throw new Error("Failed to verify certificate ownership");
    }
  }

  // Fetch certificate metadata from blockchain
  async fetchCertificateMetadata(tokenId) {
    try {
      logger.info("Fetching metadata for token", { tokenId });

      // In a real implementation, this would query the NFT's metadata URI
      const mockMetadata = {
        name: `Aurora English Certification #${tokenId}`,
        description: "Official Aurora English proficiency certification",
        image:
          "https://images.unsplash.com/photo-1507003211169-0a1dd7228f2d?w=400&h=300&fit=crop",
        attributes: [
          { trait_type: "Level", value: "A1" },
          { trait_type: "Score", value: "85" },
          { trait_type: "Issuer", value: "Aurora Learning Platform" },
          { trait_type: "Issue Date", value: "2024-01-15" },
        ],
        external_url: "https://aurora-learning.com/certificates",
        animation_url: null,
      };

      // Simulate metadata fetch delay
      await new Promise((resolve) => setTimeout(resolve, 300));

      return mockMetadata;
    } catch (error) {
      console.error("Error fetching certificate metadata:", error);
      throw new Error("Failed to fetch certificate metadata");
    }
  }

  // Generate shareable certificate URL
  generateShareableUrl(tokenId, walletAddress) {
    const baseUrl = window.location.origin;
    return `${baseUrl}/certificate/${tokenId}?wallet=${walletAddress}`;
  }

  // Download certificate as PDF/PNG
  async downloadCertificate(certificate) {
    try {
      logger.info("Downloading certificate", { title: certificate.title });

      // In a real implementation, this would generate a PDF/PNG
      // For now, we'll simulate the download process
      await new Promise((resolve) => setTimeout(resolve, 2000));

      return {
        success: true,
        filename: `aurora-certificate-${certificate.level}-${certificate.tokenId}.pdf`,
        downloadUrl: `data:application/pdf;base64,${btoa("mock-pdf-content")}`,
      };
    } catch (error) {
      console.error("Error downloading certificate:", error);
      throw new Error("Failed to download certificate");
    }
  }

  // Get certificate analytics
  async getCertificateAnalytics(walletAddress) {
    try {
      const certificates = await this.fetchUserCertificates(walletAddress);

      const analytics = {
        totalCertificates: certificates.length,
        averageScore:
          certificates.length > 0
            ? Math.round(
                certificates.reduce(
                  (acc, cert) => acc + cert.metadata.score,
                  0
                ) / certificates.length
              )
            : 0,
        highestLevel:
          certificates.length > 0
            ? certificates.reduce((highest, cert) => {
                const levels = ["A1", "A2", "B1", "B2", "C1", "C2"];
                const currentIndex = levels.indexOf(cert.level);
                const highestIndex = levels.indexOf(highest);
                return currentIndex > highestIndex ? cert.level : highest;
              }, "A1")
            : "None",
        totalHours: certificates.reduce(
          (acc, cert) => acc + cert.metadata.totalHours,
          0
        ),
        skillsAcquired: [
          ...new Set(certificates.flatMap((cert) => cert.metadata.skills)),
        ],
        certificatesByLevel: certificates.reduce((acc, cert) => {
          acc[cert.level] = (acc[cert.level] || 0) + 1;
          return acc;
        }, {}),
      };

      return analytics;
    } catch (error) {
      console.error("Error getting certificate analytics:", error);
      throw new Error("Failed to get certificate analytics");
    }
  }

  // Verify certificate authenticity on blockchain
  async verifyCertificateAuthenticity(tokenId, contractAddress) {
    try {
      logger.info("Verifying certificate authenticity", {
        tokenId,
        contractAddress,
      });

      // In a real implementation, this would verify the certificate
      // exists on the blockchain and is issued by Aurora
      const mockVerification = {
        isAuthentic: true,
        issuer: "Aurora Learning Platform",
        contractAddress,
        tokenId,
        verificationDate: new Date().toISOString(),
        blockchainProof: `authenticity_proof_${tokenId}_${Date.now()}`,
      };

      // Simulate verification delay
      await new Promise((resolve) => setTimeout(resolve, 800));

      return mockVerification;
    } catch (error) {
      console.error("Error verifying certificate authenticity:", error);
      throw new Error("Failed to verify certificate authenticity");
    }
  }
}

export default new CertificateService();
