package cache

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

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

	"github.com/fraktal/mev-beta/bindings/uniswap"
	"github.com/fraktal/mev-beta/internal/logger"
)

// ReserveData holds cached reserve information for a pool
type ReserveData struct {
	Reserve0      *big.Int
	Reserve1      *big.Int
	Liquidity     *big.Int // For UniswapV3
	SqrtPriceX96  *big.Int // For UniswapV3
	Tick          int      // For UniswapV3
	LastUpdated   time.Time
	IsV3          bool
}

// ReserveCache provides cached access to pool reserves with TTL
type ReserveCache struct {
	client      *ethclient.Client
	logger      *logger.Logger
	cache       map[common.Address]*ReserveData
	cacheMutex  sync.RWMutex
	ttl         time.Duration
	cleanupStop chan struct{}

	// Metrics
	hits   uint64
	misses uint64
}

// NewReserveCache creates a new reserve cache with the specified TTL
func NewReserveCache(client *ethclient.Client, logger *logger.Logger, ttl time.Duration) *ReserveCache {
	rc := &ReserveCache{
		client:      client,
		logger:      logger,
		cache:       make(map[common.Address]*ReserveData),
		ttl:         ttl,
		cleanupStop: make(chan struct{}),
		hits:        0,
		misses:      0,
	}

	// Start background cleanup goroutine
	go rc.cleanupExpiredEntries()

	return rc
}

// Get retrieves cached reserve data for a pool, or nil if not cached/expired
func (rc *ReserveCache) Get(poolAddress common.Address) *ReserveData {
	rc.cacheMutex.RLock()
	defer rc.cacheMutex.RUnlock()

	data, exists := rc.cache[poolAddress]
	if !exists {
		rc.misses++
		return nil
	}

	// Check if expired
	if time.Since(data.LastUpdated) > rc.ttl {
		rc.misses++
		return nil
	}

	rc.hits++
	return data
}

// GetOrFetch retrieves reserve data from cache, or fetches from RPC if not cached
func (rc *ReserveCache) GetOrFetch(ctx context.Context, poolAddress common.Address, isV3 bool) (*ReserveData, error) {
	// Try cache first
	if cached := rc.Get(poolAddress); cached != nil {
		return cached, nil
	}

	// Cache miss - fetch from RPC
	var data *ReserveData
	var err error

	if isV3 {
		data, err = rc.fetchV3Reserves(ctx, poolAddress)
	} else {
		data, err = rc.fetchV2Reserves(ctx, poolAddress)
	}

	if err != nil {
		return nil, fmt.Errorf("failed to fetch reserves for %s: %w", poolAddress.Hex(), err)
	}

	// Cache the result
	rc.Set(poolAddress, data)

	return data, nil
}

// fetchV2Reserves queries UniswapV2 pool reserves via RPC
func (rc *ReserveCache) fetchV2Reserves(ctx context.Context, poolAddress common.Address) (*ReserveData, error) {
	// Create contract binding
	pairContract, err := uniswap.NewIUniswapV2Pair(poolAddress, rc.client)
	if err != nil {
		return nil, fmt.Errorf("failed to bind V2 pair contract: %w", err)
	}

	// Call getReserves()
	reserves, err := pairContract.GetReserves(&bind.CallOpts{Context: ctx})
	if err != nil {
		return nil, fmt.Errorf("getReserves() call failed: %w", err)
	}

	data := &ReserveData{
		Reserve0:    reserves.Reserve0, // Already *big.Int from contract binding
		Reserve1:    reserves.Reserve1, // Already *big.Int from contract binding
		LastUpdated: time.Now(),
		IsV3:        false,
	}

	return data, nil
}

// fetchV3Reserves queries UniswapV3 pool state via RPC
func (rc *ReserveCache) fetchV3Reserves(ctx context.Context, poolAddress common.Address) (*ReserveData, error) {
	// For UniswapV3, we need to query slot0() and liquidity()
	// This requires the IUniswapV3Pool binding

	// Check if we have a V3 pool binding available
	// For now, return an error indicating V3 needs implementation
	// TODO: Implement V3 reserve calculation from slot0() and liquidity()

	return nil, fmt.Errorf("V3 reserve fetching not yet implemented - needs IUniswapV3Pool binding")
}

// Set stores reserve data in the cache
func (rc *ReserveCache) Set(poolAddress common.Address, data *ReserveData) {
	rc.cacheMutex.Lock()
	defer rc.cacheMutex.Unlock()

	data.LastUpdated = time.Now()
	rc.cache[poolAddress] = data
}

// Invalidate removes a pool's cached data (for event-driven invalidation)
func (rc *ReserveCache) Invalidate(poolAddress common.Address) {
	rc.cacheMutex.Lock()
	defer rc.cacheMutex.Unlock()

	delete(rc.cache, poolAddress)
	rc.logger.Debug(fmt.Sprintf("Invalidated cache for pool %s", poolAddress.Hex()))
}

// InvalidateMultiple removes multiple pools' cached data at once
func (rc *ReserveCache) InvalidateMultiple(poolAddresses []common.Address) {
	rc.cacheMutex.Lock()
	defer rc.cacheMutex.Unlock()

	for _, addr := range poolAddresses {
		delete(rc.cache, addr)
	}

	rc.logger.Debug(fmt.Sprintf("Invalidated cache for %d pools", len(poolAddresses)))
}

// Clear removes all cached data
func (rc *ReserveCache) Clear() {
	rc.cacheMutex.Lock()
	defer rc.cacheMutex.Unlock()

	rc.cache = make(map[common.Address]*ReserveData)
	rc.logger.Info("Cleared reserve cache")
}

// GetMetrics returns cache performance metrics
func (rc *ReserveCache) GetMetrics() (hits, misses uint64, hitRate float64, size int) {
	rc.cacheMutex.RLock()
	defer rc.cacheMutex.RUnlock()

	total := rc.hits + rc.misses
	if total > 0 {
		hitRate = float64(rc.hits) / float64(total) * 100.0
	}

	return rc.hits, rc.misses, hitRate, len(rc.cache)
}

// cleanupExpiredEntries runs in background to remove expired cache entries
func (rc *ReserveCache) cleanupExpiredEntries() {
	ticker := time.NewTicker(rc.ttl / 2) // Cleanup at half the TTL interval
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			rc.performCleanup()
		case <-rc.cleanupStop:
			return
		}
	}
}

// performCleanup removes expired entries from cache
func (rc *ReserveCache) performCleanup() {
	rc.cacheMutex.Lock()
	defer rc.cacheMutex.Unlock()

	now := time.Now()
	expiredCount := 0

	for addr, data := range rc.cache {
		if now.Sub(data.LastUpdated) > rc.ttl {
			delete(rc.cache, addr)
			expiredCount++
		}
	}

	if expiredCount > 0 {
		rc.logger.Debug(fmt.Sprintf("Cleaned up %d expired cache entries", expiredCount))
	}
}

// Stop halts the background cleanup goroutine
func (rc *ReserveCache) Stop() {
	close(rc.cleanupStop)
}

// CalculateV3ReservesFromState calculates effective reserves for V3 pool from liquidity and price
// This is a helper function for when we have liquidity and sqrtPriceX96 but need reserve values
func CalculateV3ReservesFromState(liquidity, sqrtPriceX96 *big.Int) (*big.Int, *big.Int) {
	// For UniswapV3, reserves are not stored directly but can be approximated from:
	// reserve0 = liquidity / sqrt(price)
	// reserve1 = liquidity * sqrt(price)

	// Convert sqrtPriceX96 to sqrtPrice (divide by 2^96)
	q96 := new(big.Float).SetInt(new(big.Int).Exp(big.NewInt(2), big.NewInt(96), nil))
	sqrtPriceFloat := new(big.Float).SetInt(sqrtPriceX96)
	sqrtPrice := new(big.Float).Quo(sqrtPriceFloat, q96)

	liquidityFloat := new(big.Float).SetInt(liquidity)

	// Calculate reserve0 = liquidity / sqrtPrice
	reserve0Float := new(big.Float).Quo(liquidityFloat, sqrtPrice)

	// Calculate reserve1 = liquidity * sqrtPrice
	reserve1Float := new(big.Float).Mul(liquidityFloat, sqrtPrice)

	// Convert back to big.Int
	reserve0 := new(big.Int)
	reserve1 := new(big.Int)
	reserve0Float.Int(reserve0)
	reserve1Float.Int(reserve1)

	return reserve0, reserve1
}