package holders

import (
	"context"
	"fmt"
	"log"
	"math/big"
	"strings"
	"sync"
	"time"

	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/ethclient"
	"github.com/gothinkster/golang-gin-realworld-example-app/models"
	db "github.com/gothinkster/golang-gin-realworld-example-app/common"
)

// Config holds scanner configuration
type Config struct {
	ChainID          int
	RPCURL           string
	YTVaults         []VaultConfig
	YTLPAddress      string
	DeploymentBlocks DeploymentBlocks
	PollInterval     time.Duration
	BatchSize        int64
}

type VaultConfig struct {
	Name        string
	Address     string
	DeployBlock uint64
}

type DeploymentBlocks struct {
	YTLP uint64
}

// Scanner handles blockchain event scanning
type Scanner struct {
	config          Config
	client          *ethclient.Client
	lastScannedBlock uint64
	isScanning      bool
	mu              sync.Mutex

	// Address tracking
	ytAddresses map[string]map[string]int64 // vault -> address -> firstSeen
	lpAddresses map[string]int64            // address -> firstSeen
}

// Event topics
var (
	transferEventTopic = crypto.Keccak256Hash([]byte("Transfer(address,address,uint256)"))
)

// NewScanner creates a new blockchain scanner
func NewScanner(config Config) (*Scanner, error) {
	client, err := ethclient.Dial(config.RPCURL)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to Ethereum client: %w", err)
	}

	return &Scanner{
		config:      config,
		client:      client,
		ytAddresses: make(map[string]map[string]int64),
		lpAddresses: make(map[string]int64),
	}, nil
}

// loadStateFromDB loads the last scanned block from database
func (s *Scanner) loadStateFromDB() uint64 {
	database := db.GetDB()
	var state models.ScannerState
	result := database.Where("chain_id = ? AND scanner_type = ?", s.config.ChainID, "holder").First(&state)
	if result.Error != nil {
		return 0
	}
	return state.LastScannedBlock
}

// saveStateToDB persists the last scanned block to database
func (s *Scanner) saveStateToDB(block uint64) {
	database := db.GetDB()
	state := models.ScannerState{
		ScannerType:      "holder",
		ChainID:          s.config.ChainID,
		LastScannedBlock: block,
	}
	database.Where("chain_id = ? AND scanner_type = ?", s.config.ChainID, "holder").Assign(state).FirstOrCreate(&state)
	database.Model(&state).Update("last_scanned_block", block)
}

// loadAddressesFromDB restores in-memory address maps from holder_snapshots
func (s *Scanner) loadAddressesFromDB() {
	database := db.GetDB()
	var snapshots []models.HolderSnapshot
	database.Where("chain_id = ?", s.config.ChainID).Find(&snapshots)

	for _, snap := range snapshots {
		switch snap.TokenType {
		case "ytLP":
			s.lpAddresses[snap.HolderAddress] = snap.FirstSeen
		default:
			for _, vault := range s.config.YTVaults {
				if vault.Name == snap.TokenType {
					if s.ytAddresses[vault.Address] == nil {
						s.ytAddresses[vault.Address] = make(map[string]int64)
					}
					s.ytAddresses[vault.Address][snap.HolderAddress] = snap.FirstSeen
				}
			}
		}
	}
	log.Printf("▶️  从数据库加载了 %d 个历史地址", len(snapshots))
}

// Start begins the scanning process
func Start(config Config) error {
	scanner, err := NewScanner(config)
	if err != nil {
		return err
	}

	log.Println("=== Holder Scanner Started ===")
	log.Printf("RPC: %s\n", config.RPCURL)
	log.Printf("Poll Interval: %v\n", config.PollInterval)

	// Check if we can resume from a previous scan
	lastBlock := scanner.loadStateFromDB()
	if lastBlock > 0 {
		log.Printf("▶️  发现上次扫描记录，从区块 %d 续扫...", lastBlock)
		scanner.loadAddressesFromDB()
		scanner.lastScannedBlock = lastBlock
	} else {
		// Fresh start: full initial scan from deploy blocks
		log.Println("📊 首次扫描，从部署区块开始...")
		startTime := time.Now()
		if err := scanner.scanAll(context.Background(), true); err != nil {
			return fmt.Errorf("initial scan failed: %w", err)
		}
		log.Printf("✓ 初始扫描完成，耗时 %v\n", time.Since(startTime))
	}

	// Start polling
	ticker := time.NewTicker(config.PollInterval)
	defer ticker.Stop()

	log.Printf("⏰ 开始轮询，每 %v 扫一次新区块...\n", config.PollInterval)

	for range ticker.C {
		if err := scanner.incrementalScan(context.Background()); err != nil {
			log.Printf("✗ Incremental scan error: %v\n", err)
		}
	}

	return nil
}

// minUint64 returns the smaller of two uint64 values.
func minUint64(a, b uint64) uint64 {
	if a < b {
		return a
	}
	return b
}

// scanBatch scans ALL contract types for a single block range [fromBlock, toBlock].
// The range must be ≤ BatchSize. After this call, every contract has been scanned to toBlock.
func (s *Scanner) scanBatch(ctx context.Context, fromBlock, toBlock uint64) {
	log.Printf("  [Batch] Scanning blocks %d → %d\n", fromBlock, toBlock)
	s.scanYTVaultTransfers(ctx, fromBlock, toBlock)
	s.scanYTLPTransfers(ctx, fromBlock, toBlock)
	s.scanSwapEvents(ctx, fromBlock, toBlock)

	// Checkpoint: all contracts have been scanned up to toBlock
	s.mu.Lock()
	s.lastScannedBlock = toBlock
	s.mu.Unlock()
	s.saveStateToDB(toBlock)
}

// scanAll performs a full scan from deployment blocks, saving a checkpoint after every batch.
// All contract types are scanned together per batch, so the checkpoint is always safe.
func (s *Scanner) scanAll(ctx context.Context, isInitial bool) error {
	s.mu.Lock()
	if s.isScanning {
		s.mu.Unlock()
		return fmt.Errorf("scan already in progress")
	}
	s.isScanning = true
	s.mu.Unlock()

	defer func() {
		s.mu.Lock()
		s.isScanning = false
		s.mu.Unlock()
	}()

	latestBlock, err := s.client.BlockNumber(ctx)
	if err != nil {
		return err
	}
	log.Printf("Current block: %d\n", latestBlock)

	// Determine the earliest block we need to scan across all contracts
	startBlock := s.lastScannedBlock + 1
	if isInitial {
		startBlock = latestBlock // will be lowered below
		for _, v := range s.config.YTVaults {
			startBlock = minUint64(startBlock, v.DeployBlock)
		}
		if s.config.YTLPAddress != "" && s.config.DeploymentBlocks.YTLP > 0 {
			startBlock = minUint64(startBlock, s.config.DeploymentBlocks.YTLP)
		}
	}
	if startBlock > latestBlock {
		log.Printf("📌 No new blocks to scan (startBlock %d > latestBlock %d)\n", startBlock, latestBlock)
		return nil
	}

	log.Printf("📊 Scanning blocks %d → %d in batches of %d\n", startBlock, latestBlock, s.config.BatchSize)

	// Outer loop: one checkpoint per batch, all contracts scanned together
	for batchFrom := startBlock; batchFrom <= latestBlock; {
		batchTo := minUint64(batchFrom+uint64(s.config.BatchSize)-1, latestBlock)
		s.scanBatch(ctx, batchFrom, batchTo)
		batchFrom = batchTo + 1

		// Rate limiting between batches
		if batchFrom <= latestBlock {
			time.Sleep(100 * time.Millisecond)
		}
	}

	// Balance snapshots: run once after all event scanning is done
	log.Printf("📊 Updating balance snapshots...\n")
	for _, vault := range s.config.YTVaults {
		if err := s.saveYTHolders(ctx, vault); err != nil {
			log.Printf("  [Snapshot] %s error: %v", vault.Name, err)
		}
	}
	if err := s.saveYTLPHolders(ctx); err != nil {
		log.Printf("  [Snapshot] ytLP error: %v", err)
	}

	log.Printf("📌 Scan complete. Last scanned block: %d\n", latestBlock)
	return nil
}

// incrementalScan scans new blocks since last scan.
// Incremental ranges are small (seconds of blocks), so a single batch suffices.
func (s *Scanner) incrementalScan(ctx context.Context) error {
	s.mu.Lock()
	if s.isScanning {
		s.mu.Unlock()
		log.Println("⏰ Skipping scan (previous scan still running)")
		return nil
	}
	s.isScanning = true
	lastBlock := s.lastScannedBlock
	s.mu.Unlock()

	defer func() {
		s.mu.Lock()
		s.isScanning = false
		s.mu.Unlock()
	}()

	latestBlock, err := s.client.BlockNumber(ctx)
	if err != nil {
		return err
	}

	if latestBlock <= lastBlock {
		log.Printf("⏰ [%s] No new blocks (current: %d)\n", time.Now().Format("15:04:05"), latestBlock)
		return nil
	}

	log.Printf("\n%s\n", strings.Repeat("=", 60))
	log.Printf("⏰ [%s] Found new blocks %d → %d\n", time.Now().Format("15:04:05"), lastBlock+1, latestBlock)
	log.Printf("%s\n", strings.Repeat("=", 60))

	startTime := time.Now()
	fromBlock := lastBlock + 1

	// Incremental range may exceed BatchSize if server was down for a while; use batches
	for batchFrom := fromBlock; batchFrom <= latestBlock; {
		batchTo := minUint64(batchFrom+uint64(s.config.BatchSize)-1, latestBlock)
		s.scanBatch(ctx, batchFrom, batchTo)
		batchFrom = batchTo + 1
		if batchFrom <= latestBlock {
			time.Sleep(100 * time.Millisecond)
		}
	}

	// Update balance snapshots
	for _, vault := range s.config.YTVaults {
		if err := s.saveYTHolders(ctx, vault); err != nil {
			log.Printf("  [Snapshot] %s error: %v", vault.Name, err)
		}
	}
	if err := s.saveYTLPHolders(ctx); err != nil {
		log.Printf("  [Snapshot] ytLP error: %v", err)
	}

	log.Printf("✓ Incremental scan completed in %v\n", time.Since(startTime))
	return nil
}

// scanYTVaultTransfers scans Transfer events for all YT vaults in the given block range.
// fromBlock/toBlock must already be a single batch (≤ BatchSize blocks).
// Each vault skips blocks before its own deployBlock.
// Does NOT save balance snapshots (call saveYTHolders separately after all batches complete).
func (s *Scanner) scanYTVaultTransfers(ctx context.Context, fromBlock, toBlock uint64) error {
	for _, vault := range s.config.YTVaults {
		// Skip if vault not yet deployed in this range
		if vault.DeployBlock > toBlock {
			continue
		}
		effectiveFrom := fromBlock
		if vault.DeployBlock > effectiveFrom {
			effectiveFrom = vault.DeployBlock
		}

		logs, err := s.queryBlockRange(ctx, common.HexToAddress(vault.Address), transferEventTopic, effectiveFrom, toBlock)
		if err != nil {
			log.Printf("  [Transfer] %s query error: %v", vault.Name, err)
			continue
		}

		if s.ytAddresses[vault.Address] == nil {
			s.ytAddresses[vault.Address] = make(map[string]int64)
		}

		for _, l := range logs {
			toAddress := common.BytesToAddress(l.Topics[2].Bytes()).Hex()
			if toAddress == "0x0000000000000000000000000000000000000000" {
				continue
			}
			if _, exists := s.ytAddresses[vault.Address][toAddress]; !exists {
				block, err := s.client.BlockByNumber(ctx, big.NewInt(int64(l.BlockNumber)))
				if err == nil {
					s.ytAddresses[vault.Address][toAddress] = int64(block.Time())
				}
			}
		}
	}
	return nil
}

// scanYTLPTransfers scans Transfer events for the YT LP token in the given block range.
// Does NOT save balance snapshots (call saveYTLPHolders separately after all batches complete).
func (s *Scanner) scanYTLPTransfers(ctx context.Context, fromBlock, toBlock uint64) error {
	if s.config.YTLPAddress == "" {
		return nil
	}
	lpDeployBlock := s.config.DeploymentBlocks.YTLP
	if lpDeployBlock > toBlock {
		return nil
	}
	effectiveFrom := fromBlock
	if lpDeployBlock > effectiveFrom {
		effectiveFrom = lpDeployBlock
	}

	logs, err := s.queryBlockRange(ctx, common.HexToAddress(s.config.YTLPAddress), transferEventTopic, effectiveFrom, toBlock)
	if err != nil {
		log.Printf("  [Transfer] ytLP query error: %v", err)
		return nil
	}

	for _, l := range logs {
		toAddress := common.BytesToAddress(l.Topics[2].Bytes()).Hex()
		if toAddress == "0x0000000000000000000000000000000000000000" {
			continue
		}
		if _, exists := s.lpAddresses[toAddress]; !exists {
			block, err := s.client.BlockByNumber(ctx, big.NewInt(int64(l.BlockNumber)))
			if err == nil {
				s.lpAddresses[toAddress] = int64(block.Time())
			}
		}
	}
	return nil
}


// queryBlockRange queries logs for a single block range (no internal batching).
// The caller is responsible for keeping the range within RPC limits (BatchSize).
func (s *Scanner) queryBlockRange(ctx context.Context, contractAddr common.Address, topic common.Hash, fromBlock, toBlock uint64) ([]types.Log, error) {
	query := ethereum.FilterQuery{
		FromBlock: big.NewInt(int64(fromBlock)),
		ToBlock:   big.NewInt(int64(toBlock)),
		Addresses: []common.Address{contractAddr},
		Topics:    [][]common.Hash{{topic}},
	}
	logs, err := s.client.FilterLogs(ctx, query)
	if err != nil {
		return nil, fmt.Errorf("failed to query logs [%d-%d]: %w", fromBlock, toBlock, err)
	}
	return logs, nil
}

// queryLogsInBatches queries logs in batches to avoid RPC limits.
// Used only by incremental scans where range size is unpredictable.
func (s *Scanner) queryLogsInBatches(ctx context.Context, contractAddr common.Address, topic common.Hash, fromBlock, toBlock uint64) ([]types.Log, error) {
	var allLogs []types.Log
	currentBlock := fromBlock

	log.Printf("    Querying blocks %d -> %d (total: %d blocks)\n", fromBlock, toBlock, toBlock-fromBlock+1)

	for currentBlock <= toBlock {
		endBlock := currentBlock + uint64(s.config.BatchSize)
		if endBlock > toBlock {
			endBlock = toBlock
		}

		log.Printf("    Querying blocks %d - %d...\n", currentBlock, endBlock)

		logs, err := s.queryBlockRange(ctx, contractAddr, topic, currentBlock, endBlock)
		if err != nil {
			return nil, err
		}

		allLogs = append(allLogs, logs...)
		log.Printf("    ✓ Got %d events\n", len(logs))

		currentBlock = endBlock + 1

		// Rate limiting
		if currentBlock <= toBlock {
			time.Sleep(100 * time.Millisecond)
		}
	}

	log.Printf("    Total: %d events\n\n", len(allLogs))
	return allLogs, nil
}

// saveYTHolders queries balances and saves to database
func (s *Scanner) saveYTHolders(ctx context.Context, vault VaultConfig) error {
	// ERC20 balanceOf ABI
	balanceOfABI, _ := abi.JSON(strings.NewReader(`[{"constant":true,"inputs":[{"name":"account","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]`))

	database := db.GetDB()
	now := time.Now().Unix()
	holders := 0
	totalAddresses := len(s.ytAddresses[vault.Address])

	contractAddr := common.HexToAddress(vault.Address)
	log.Printf("📞 [%s] 开始查询 %d 个地址的余额", vault.Name, totalAddresses)
	log.Printf("📍 [%s] 合约地址: %s", vault.Name, vault.Address)

	processedCount := 0
	errorCount := 0
	zeroBalanceCount := 0

	for address, firstSeen := range s.ytAddresses[vault.Address] {
		processedCount++

		// Call balanceOf
		data, err := balanceOfABI.Pack("balanceOf", common.HexToAddress(address))
		if err != nil {
			log.Printf("❌ [%s] Pack balanceOf 失败: %s - %v", vault.Name, address, err)
			errorCount++
			continue
		}

		result, err := s.client.CallContract(ctx, ethereum.CallMsg{
			To:   &contractAddr,
			Data: data,
		}, nil)
		if err != nil {
			log.Printf("❌ [%s] CallContract 失败: %s - %v", vault.Name, address, err)
			errorCount++
			continue
		}

		balance := new(big.Int).SetBytes(result)

		// Log balance query result
		if processedCount <= 5 || balance.Cmp(big.NewInt(0)) > 0 {
			log.Printf("   [%s] 地址: %s, 余额: %s", vault.Name, address[:10]+"...", balance.String())
		}

		if balance.Cmp(big.NewInt(0)) == 0 {
			zeroBalanceCount++
			continue
		}

		holders++

		// Upsert to database: create if not exists, only update balance/last_updated if exists
		holder := models.HolderSnapshot{
			HolderAddress: address,
			TokenType:     vault.Name,
			TokenAddress:  vault.Address,
			Balance:       balance.String(),
			ChainID:       s.config.ChainID,
			FirstSeen:     firstSeen,
			LastUpdated:   now,
		}
		var existing models.HolderSnapshot
		res := database.Where("holder_address = ? AND token_type = ?", address, vault.Name).First(&existing)
		if res.Error != nil {
			database.Create(&holder)
		} else {
			database.Model(&existing).Updates(map[string]interface{}{
				"balance":      balance.String(),
				"last_updated": now,
			})
		}
	}

	log.Printf("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━")
	log.Printf("📊 [%s] 查询完成统计:", vault.Name)
	log.Printf("   • 总地址数: %d", totalAddresses)
	log.Printf("   • 已处理: %d", processedCount)
	log.Printf("   • 余额>0: %d ✅", holders)
	log.Printf("   • 余额=0: %d", zeroBalanceCount)
	log.Printf("   • 错误数: %d", errorCount)
	log.Printf("   • 已保存到数据库: %d", holders)
	log.Printf("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━\n")
	return nil
}

// saveYTLPHolders saves ytLP holders to database
func (s *Scanner) saveYTLPHolders(ctx context.Context) error {
	balanceOfABI, _ := abi.JSON(strings.NewReader(`[{"constant":true,"inputs":[{"name":"account","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]`))

	database := db.GetDB()
	now := time.Now().Unix()
	holders := 0
	totalAddresses := len(s.lpAddresses)

	contractAddr := common.HexToAddress(s.config.YTLPAddress)
	log.Printf("📞 [ytLP] 开始查询 %d 个地址的余额", totalAddresses)
	log.Printf("📍 [ytLP] 合约地址: %s", s.config.YTLPAddress)

	processedCount := 0
	errorCount := 0
	zeroBalanceCount := 0

	for address, firstSeen := range s.lpAddresses {
		processedCount++

		data, err := balanceOfABI.Pack("balanceOf", common.HexToAddress(address))
		if err != nil {
			log.Printf("❌ [ytLP] Pack balanceOf 失败: %s - %v", address, err)
			errorCount++
			continue
		}

		result, err := s.client.CallContract(ctx, ethereum.CallMsg{
			To:   &contractAddr,
			Data: data,
		}, nil)
		if err != nil {
			log.Printf("❌ [ytLP] CallContract 失败: %s - %v", address, err)
			errorCount++
			continue
		}

		balance := new(big.Int).SetBytes(result)

		// Log balance query result
		if processedCount <= 5 || balance.Cmp(big.NewInt(0)) > 0 {
			log.Printf("   [ytLP] 地址: %s, 余额: %s", address[:10]+"...", balance.String())
		}

		if balance.Cmp(big.NewInt(0)) == 0 {
			zeroBalanceCount++
			continue
		}

		holders++

		holder := models.HolderSnapshot{
			HolderAddress: address,
			TokenType:     "ytLP",
			TokenAddress:  s.config.YTLPAddress,
			Balance:       balance.String(),
			ChainID:       s.config.ChainID,
			FirstSeen:     firstSeen,
			LastUpdated:   now,
		}
		var existing models.HolderSnapshot
		res := database.Where("holder_address = ? AND token_type = ?", address, "ytLP").First(&existing)
		if res.Error != nil {
			database.Create(&holder)
		} else {
			database.Model(&existing).Updates(map[string]interface{}{
				"balance":      balance.String(),
				"last_updated": now,
			})
		}
	}

	log.Printf("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━")
	log.Printf("📊 [ytLP] 查询完成统计:")
	log.Printf("   • 总地址数: %d", totalAddresses)
	log.Printf("   • 已处理: %d", processedCount)
	log.Printf("   • 余额>0: %d ✅", holders)
	log.Printf("   • 余额=0: %d", zeroBalanceCount)
	log.Printf("   • 错误数: %d", errorCount)
	log.Printf("   • 已保存到数据库: %d", holders)
	log.Printf("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━\n")
	return nil
}