discourse/backend/blockchain/service.go

package blockchain

import (
	"context"
	"fmt"
	"log"
	"math/big"
	"os"
	"time"

	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/ethclient"
)

const (
	// MaxRetries is the maximum number of times to retry a transaction
	MaxRetries = 3

	// RetryDelay is the delay between retries in seconds
	RetryDelay = 2

	// Polygon Mumbai testnet chain ID
	PolygonMumbaiChainID = 80001

	// Polygon Amoy testnet chain ID
	PolygonAmoyChainID = 80002
)

// BlockchainService handles interactions with the Polygon blockchain
type BlockchainService struct {
	client   *ethclient.Client
	auth     *bind.TransactOpts
	contract *VoxPopContract // This will be replaced with actual contract bindings
	chainID  *big.Int
}

// NewBlockchainService creates a new blockchain service
func NewBlockchainService() (*BlockchainService, error) {
	// Get RPC URL from environment
	rpcURL := os.Getenv("POLYGON_RPC")
	if rpcURL == "" {
		return nil, fmt.Errorf("POLYGON_RPC environment variable not set")
	}

	// Connect to Polygon
	client, err := ethclient.Dial(rpcURL)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to Polygon: %v", err)
	}

	// Get private key from environment
	privateKey := os.Getenv("PRIVATE_KEY")
	if privateKey == "" {
		return nil, fmt.Errorf("PRIVATE_KEY environment variable not set")
	}

	// Parse private key
	privateKeyECDSA, err := crypto.HexToECDSA(privateKey)
	if err != nil {
		return nil, fmt.Errorf("failed to parse private key: %v", err)
	}

	// Get chain ID from environment or use default
	chainID := big.NewInt(PolygonAmoyChainID)
	if chainIDStr := os.Getenv("CHAIN_ID"); chainIDStr != "" {
		chainID.SetString(chainIDStr, 10)
	}

	// Create the transactor
	auth, err := bind.NewKeyedTransactorWithChainID(privateKeyECDSA, chainID)
	if err != nil {
		return nil, fmt.Errorf("failed to create transactor: %v", err)
	}

	// Get contract address from environment
	contractAddress := os.Getenv("CONTRACT_ADDRESS")
	if contractAddress == "" {
		return nil, fmt.Errorf("CONTRACT_ADDRESS environment variable not set")
	}

	// Create contract instance (mock for now)
	contract := &VoxPopContract{} // This will be replaced with actual contract bindings

	return &BlockchainService{
		client:   client,
		auth:     auth,
		contract: contract,
		chainID:  chainID,
	}, nil
}

// SubmitPerspective submits a perspective hash to the blockchain
func (s *BlockchainService) SubmitPerspective(hash string) (string, error) {
	log.Printf("Submitting perspective hash: %s", hash)

	// Mock implementation - in production, this would call the actual contract
	// tx, err := s.contract.SubmitPerspective(s.auth, hash)
	// if err != nil {
	//     return "", fmt.Errorf("failed to submit perspective: %v", err)
	// }

	// For now, just log and return a mock transaction hash
	mockTxHash := "0x" + hash[:64]
	log.Printf("Mock transaction submitted: %s", mockTxHash)
	return mockTxHash, nil
}

// ProposeInsight proposes a new insight
func (s *BlockchainService) ProposeInsight(insight string) (string, error) {
	log.Printf("Proposing insight: %s", insight)

	// Mock implementation - in production, this would call the actual contract
	// tx, err := s.contract.ProposeInsight(s.auth, insight)
	// if err != nil {
	//     return "", fmt.Errorf("failed to propose insight: %v", err)
	// }

	// For now, just log and return a mock transaction hash
	mockTxHash := "0x" + insight[:64]
	log.Printf("Mock transaction submitted: %s", mockTxHash)
	return mockTxHash, nil
}

// VoteOnInsight casts a vote on an insight
func (s *BlockchainService) VoteOnInsight(insightID string, vote bool) (string, error) {
	log.Printf("Voting on insight %s: %v", insightID, vote)

	// Mock implementation - in production, this would call the actual contract
	// tx, err := s.contract.VoteOnInsight(s.auth, insightID, vote)
	// if err != nil {
	//     return "", fmt.Errorf("failed to vote on insight: %v", err)
	// }

	// For now, just log and return a mock transaction hash
	mockTxHash := "0x" + insightID[:64]
	log.Printf("Mock transaction submitted: %s", mockTxHash)
	return mockTxHash, nil
}

// estimateGasAndSendTransaction estimates gas and sends a transaction with retries
func (s *BlockchainService) estimateGasAndSendTransaction(ctx context.Context, to *common.Address, data []byte) (string, error) {
	var lastErr error
	for i := 0; i < MaxRetries; i++ {
		// Get the nonce
		nonce, err := s.client.PendingNonceAt(ctx, s.auth.From)
		if err != nil {
			lastErr = err
			time.Sleep(time.Second * RetryDelay)
			continue
		}

		// Estimate gas
		gasLimit, err := s.client.EstimateGas(ctx, ethereum.CallMsg{
			From:     s.auth.From,
			To:       to,
			Gas:      0,
			GasPrice: nil,
			Value:    nil,
			Data:     data,
		})
		if err != nil {
			lastErr = err
			time.Sleep(time.Second * RetryDelay)
			continue
		}

		// Get gas price
		gasPrice, err := s.client.SuggestGasPrice(ctx)
		if err != nil {
			lastErr = err
			time.Sleep(time.Second * RetryDelay)
			continue
		}

		// Create transaction
		tx := types.NewTransaction(nonce, *to, nil, gasLimit, gasPrice, data)

		// Sign transaction
		signedTx, err := s.auth.Signer(s.auth.From, tx)
		if err != nil {
			lastErr = err
			time.Sleep(time.Second * RetryDelay)
			continue
		}

		// Send transaction
		err = s.client.SendTransaction(ctx, signedTx)
		if err != nil {
			lastErr = err
			time.Sleep(time.Second * RetryDelay)
			continue
		}

		return signedTx.Hash().Hex(), nil
	}

	return "", fmt.Errorf("failed after %d retries: %v", MaxRetries, lastErr)
}

// Close closes the blockchain connection
func (s *BlockchainService) Close() {
	if s.client != nil {
		s.client.Close()
	}
}

// VoxPopContract is a mock contract interface (to be replaced with actual contract bindings)
type VoxPopContract struct{}