consensus/pkg/go/ai/bridge.go

// Copyright (C) 2025, Lux Industries Inc. All rights reserved.
// Cross-Chain Bridge for AI Computation Payments

package ai

import (
	"context"
	"fmt"
	"math/big"
	"sync"
	"time"
)

// SimpleBridge implements XChainBridge for cross-chain AI payments
type SimpleBridge struct {
	mu sync.RWMutex

	// Bridge state
	nodeID        string
	chains        map[string]*BridgeChain
	exchangeRates map[string]map[string]*big.Int // from -> to -> rate

	// Transaction tracking
	pendingTxs    map[string]*BridgeTransaction
	completedTxs  map[string]*BridgeTransaction

	logger Logger
}

// BridgeChain represents a connected blockchain
type BridgeChain struct {
	ChainID      string    `json:"chain_id"`
	Name         string    `json:"name"`
	RPC          string    `json:"rpc"`
	Contract     string    `json:"contract"`
	Currency     string    `json:"currency"`
	Decimals     int       `json:"decimals"`
	LastBlock    uint64    `json:"last_block"`
	LastSync     time.Time `json:"last_sync"`
	Active       bool      `json:"active"`
}

// BridgeTransaction tracks cross-chain transfers
type BridgeTransaction struct {
	ID            string    `json:"id"`
	FromChain     string    `json:"from_chain"`
	ToChain       string    `json:"to_chain"`
	Amount        *big.Int  `json:"amount"`
	Sender        string    `json:"sender"`
	Recipient     string    `json:"recipient"`
	SourceTxHash  string    `json:"source_tx_hash"`
	TargetTxHash  string    `json:"target_tx_hash"`
	Status        TxStatus  `json:"status"`
	CreatedAt     time.Time `json:"created_at"`
	CompletedAt   time.Time `json:"completed_at,omitempty"`
	Confirmations int       `json:"confirmations"`
}

// TxStatus represents transaction state
type TxStatus string

const (
	TxPending    TxStatus = "pending"
	TxConfirming TxStatus = "confirming"
	TxCompleted  TxStatus = "completed"
	TxFailed     TxStatus = "failed"
)

// NewSimpleBridge creates a new cross-chain bridge
func NewSimpleBridge(nodeID string, logger Logger) *SimpleBridge {
	return &SimpleBridge{
		nodeID:        nodeID,
		chains:        make(map[string]*BridgeChain),
		exchangeRates: make(map[string]map[string]*big.Int),
		pendingTxs:    make(map[string]*BridgeTransaction),
		completedTxs:  make(map[string]*BridgeTransaction),
		logger:        logger,
	}
}

// AddChain connects a new blockchain to the bridge
func (sb *SimpleBridge) AddChain(chain *BridgeChain) error {
	sb.mu.Lock()
	defer sb.mu.Unlock()

	sb.chains[chain.ChainID] = chain

	// Initialize exchange rates for this chain
	if sb.exchangeRates[chain.ChainID] == nil {
		sb.exchangeRates[chain.ChainID] = make(map[string]*big.Int)
	}

	// Set 1:1 rate with itself
	sb.exchangeRates[chain.ChainID][chain.ChainID] = big.NewInt(1)

	sb.logger.Info("bridge chain added", "chain_id", chain.ChainID, "name", chain.Name)
	return nil
}

// SetExchangeRate sets the exchange rate between two chains
func (sb *SimpleBridge) SetExchangeRate(fromChain, toChain string, rate *big.Int) error {
	sb.mu.Lock()
	defer sb.mu.Unlock()

	if sb.exchangeRates[fromChain] == nil {
		sb.exchangeRates[fromChain] = make(map[string]*big.Int)
	}

	sb.exchangeRates[fromChain][toChain] = new(big.Int).Set(rate)

	sb.logger.Info("exchange rate set",
		"from", fromChain,
		"to", toChain,
		"rate", rate.String())

	return nil
}

// TransferPayment implements XChainBridge.TransferPayment
func (sb *SimpleBridge) TransferPayment(ctx context.Context, sourceChain, targetChain string, amount *big.Int, recipient string) error {
	sb.mu.Lock()
	defer sb.mu.Unlock()

	// Validate chains
	srcChain, exists := sb.chains[sourceChain]
	if !exists {
		return fmt.Errorf("source chain not supported: %s", sourceChain)
	}

	dstChain, exists := sb.chains[targetChain]
	if !exists {
		return fmt.Errorf("target chain not supported: %s", targetChain)
	}

	if !srcChain.Active || !dstChain.Active {
		return fmt.Errorf("one or more chains are inactive")
	}

	// Convert amount using exchange rate
	rate, err := sb.getExchangeRate(sourceChain, targetChain)
	if err != nil {
		return fmt.Errorf("exchange rate not available: %w", err)
	}

	convertedAmount := new(big.Int).Mul(amount, rate)

	// Create bridge transaction
	tx := &BridgeTransaction{
		ID:           generateID(),
		FromChain:    sourceChain,
		ToChain:      targetChain,
		Amount:       convertedAmount,
		Sender:       "bridge_sender", // Simplified
		Recipient:    recipient,
		Status:       TxPending,
		CreatedAt:    time.Now(),
	}

	sb.pendingTxs[tx.ID] = tx

	// TODO: Implement actual cross-chain transfer
	// For now, simulate the transfer
	go sb.simulateTransfer(tx)

	sb.logger.Info("payment transfer initiated",
		"tx_id", tx.ID,
		"from", sourceChain,
		"to", targetChain,
		"amount", amount.String())

	return nil
}

// VerifyPayment implements XChainBridge.VerifyPayment
func (sb *SimpleBridge) VerifyPayment(ctx context.Context, txHash string, expectedAmount *big.Int) (*PaymentProof, error) {
	sb.mu.RLock()
	defer sb.mu.RUnlock()

	// Look for transaction in completed transactions
	for _, tx := range sb.completedTxs {
		if tx.TargetTxHash == txHash || tx.SourceTxHash == txHash {
			verified := tx.Status == TxCompleted && tx.Amount.Cmp(expectedAmount) >= 0

			proof := &PaymentProof{
				TxHash:      txHash,
				Amount:      tx.Amount,
				FromChain:   tx.FromChain,
				ToChain:     tx.ToChain,
				Sender:      tx.Sender,
				Recipient:   tx.Recipient,
				BlockHeight: 12345, // Simplified
				Timestamp:   tx.CompletedAt,
				Verified:    verified,
			}

			return proof, nil
		}
	}

	return nil, fmt.Errorf("payment not found or not verified: %s", txHash)
}

// GetExchangeRate implements XChainBridge.GetExchangeRate
func (sb *SimpleBridge) GetExchangeRate(ctx context.Context, fromChain, toChain string) (*big.Int, error) {
	sb.mu.RLock()
	defer sb.mu.RUnlock()

	return sb.getExchangeRate(fromChain, toChain)
}

// SubmitResult implements XChainBridge.SubmitResult
func (sb *SimpleBridge) SubmitResult(ctx context.Context, targetChain string, jobID string, result []byte) error {
	sb.mu.Lock()
	defer sb.mu.Unlock()

	_, exists := sb.chains[targetChain]
	if !exists {
		return fmt.Errorf("target chain not supported: %s", targetChain)
	}

	// TODO: Implement actual result submission to target chain
	// For now, just log the submission

	sb.logger.Info("result submitted to chain",
		"chain", targetChain,
		"job_id", jobID,
		"result_size", len(result))

	// Simulate chain interaction
	time.Sleep(100 * time.Millisecond)

	return nil
}

// getExchangeRate retrieves exchange rate (internal method)
func (sb *SimpleBridge) getExchangeRate(fromChain, toChain string) (*big.Int, error) {
	if fromChain == toChain {
		return big.NewInt(1), nil
	}

	if rates, exists := sb.exchangeRates[fromChain]; exists {
		if rate, exists := rates[toChain]; exists {
			return new(big.Int).Set(rate), nil
		}
	}

	return nil, fmt.Errorf("exchange rate not found: %s -> %s", fromChain, toChain)
}

// simulateTransfer simulates a cross-chain transfer
func (sb *SimpleBridge) simulateTransfer(tx *BridgeTransaction) {
	// Simulate network delay
	time.Sleep(2 * time.Second)

	sb.mu.Lock()
	defer sb.mu.Unlock()

	// Move from pending to completed
	delete(sb.pendingTxs, tx.ID)

	tx.Status = TxCompleted
	tx.CompletedAt = time.Now()
	tx.SourceTxHash = fmt.Sprintf("src_%s", generateID()[:16])
	tx.TargetTxHash = fmt.Sprintf("dst_%s", generateID()[:16])
	tx.Confirmations = 6

	sb.completedTxs[tx.ID] = tx

	sb.logger.Info("transfer completed",
		"tx_id", tx.ID,
		"source_hash", tx.SourceTxHash,
		"target_hash", tx.TargetTxHash)
}

// GetBridgeStats returns bridge statistics
func (sb *SimpleBridge) GetBridgeStats() map[string]interface{} {
	sb.mu.RLock()
	defer sb.mu.RUnlock()

	activeChains := 0
	for _, chain := range sb.chains {
		if chain.Active {
			activeChains++
		}
	}

	return map[string]interface{}{
		"node_id":         sb.nodeID,
		"total_chains":    len(sb.chains),
		"active_chains":   activeChains,
		"pending_txs":     len(sb.pendingTxs),
		"completed_txs":   len(sb.completedTxs),
		"exchange_pairs":  len(sb.exchangeRates),
	}
}

// SyncChains updates chain states
func (sb *SimpleBridge) SyncChains(ctx context.Context) error {
	sb.mu.Lock()
	defer sb.mu.Unlock()

	for chainID, chain := range sb.chains {
		if !chain.Active {
			continue
		}

		// TODO: Implement actual chain synchronization
		// For now, just update sync time
		chain.LastSync = time.Now()
		chain.LastBlock++

		sb.logger.Info("chain synced", "chain_id", chainID, "block", chain.LastBlock)
	}

	return nil
}

// ProcessPendingTransactions monitors and processes pending transfers
func (sb *SimpleBridge) ProcessPendingTransactions(ctx context.Context) error {
	sb.mu.RLock()
	pendingCount := len(sb.pendingTxs)
	sb.mu.RUnlock()

	if pendingCount > 0 {
		sb.logger.Info("processing pending transactions", "count", pendingCount)
	}

	// Process any stuck transactions
	// In a real implementation, this would check on-chain status

	return nil
}