package cache

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

	"github.com/ethereum/go-ethereum/common"

	"github.com/your-org/mev-bot/pkg/types"
)

// poolCache implements the PoolCache interface with multi-index support
type poolCache struct {
	// Primary index: address -> pool
	byAddress map[common.Address]*types.PoolInfo

	// Secondary index: token pair -> pools
	byTokenPair map[string][]*types.PoolInfo

	// Tertiary index: protocol -> pools
	byProtocol map[types.ProtocolType][]*types.PoolInfo

	// Mutex for thread safety
	mu sync.RWMutex
}

// NewPoolCache creates a new multi-index pool cache
func NewPoolCache() PoolCache {
	return &poolCache{
		byAddress:   make(map[common.Address]*types.PoolInfo),
		byTokenPair: make(map[string][]*types.PoolInfo),
		byProtocol:  make(map[types.ProtocolType][]*types.PoolInfo),
	}
}

// GetByAddress retrieves a pool by its contract address
func (c *poolCache) GetByAddress(ctx context.Context, address common.Address) (*types.PoolInfo, error) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	pool, exists := c.byAddress[address]
	if !exists {
		return nil, types.ErrPoolNotFound
	}

	return pool, nil
}

// GetByTokenPair retrieves all pools for a given token pair
func (c *poolCache) GetByTokenPair(ctx context.Context, token0, token1 common.Address) ([]*types.PoolInfo, error) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	key := makeTokenPairKey(token0, token1)
	pools := c.byTokenPair[key]

	if len(pools) == 0 {
		return []*types.PoolInfo{}, nil
	}

	// Return a copy to prevent external modification
	result := make([]*types.PoolInfo, len(pools))
	copy(result, pools)

	return result, nil
}

// GetByProtocol retrieves all pools for a given protocol
func (c *poolCache) GetByProtocol(ctx context.Context, protocol types.ProtocolType) ([]*types.PoolInfo, error) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	pools := c.byProtocol[protocol]

	if len(pools) == 0 {
		return []*types.PoolInfo{}, nil
	}

	// Return a copy to prevent external modification
	result := make([]*types.PoolInfo, len(pools))
	copy(result, pools)

	return result, nil
}

// GetByLiquidity retrieves pools sorted by liquidity (descending)
func (c *poolCache) GetByLiquidity(ctx context.Context, minLiquidity *big.Int, limit int) ([]*types.PoolInfo, error) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	// Collect all pools with sufficient liquidity
	var pools []*types.PoolInfo
	for _, pool := range c.byAddress {
		if pool.Liquidity != nil && pool.Liquidity.Cmp(minLiquidity) >= 0 {
			pools = append(pools, pool)
		}
	}

	// Sort by liquidity (descending)
	sort.Slice(pools, func(i, j int) bool {
		return pools[i].Liquidity.Cmp(pools[j].Liquidity) > 0
	})

	// Apply limit
	if limit > 0 && len(pools) > limit {
		pools = pools[:limit]
	}

	return pools, nil
}

// Add adds or updates a pool in the cache
func (c *poolCache) Add(ctx context.Context, pool *types.PoolInfo) error {
	if pool == nil {
		return fmt.Errorf("pool cannot be nil")
	}

	if err := pool.Validate(); err != nil {
		return fmt.Errorf("invalid pool: %w", err)
	}

	c.mu.Lock()
	defer c.mu.Unlock()

	// Remove old indexes if pool exists
	if oldPool, exists := c.byAddress[pool.Address]; exists {
		c.removeFromIndexes(oldPool)
	}

	// Add to primary index
	c.byAddress[pool.Address] = pool

	// Add to secondary indexes
	c.addToIndexes(pool)

	return nil
}

// Update updates pool information
func (c *poolCache) Update(ctx context.Context, address common.Address, updateFn func(*types.PoolInfo) error) error {
	c.mu.Lock()
	defer c.mu.Unlock()

	pool, exists := c.byAddress[address]
	if !exists {
		return types.ErrPoolNotFound
	}

	// Remove from indexes before update
	c.removeFromIndexes(pool)

	// Apply update
	if err := updateFn(pool); err != nil {
		// Re-add to indexes even on error to maintain consistency
		c.addToIndexes(pool)
		return err
	}

	// Validate after update
	if err := pool.Validate(); err != nil {
		// Re-add to indexes even on error
		c.addToIndexes(pool)
		return fmt.Errorf("pool invalid after update: %w", err)
	}

	// Re-add to indexes
	c.addToIndexes(pool)

	return nil
}

// Remove removes a pool from the cache
func (c *poolCache) Remove(ctx context.Context, address common.Address) error {
	c.mu.Lock()
	defer c.mu.Unlock()

	pool, exists := c.byAddress[address]
	if !exists {
		return types.ErrPoolNotFound
	}

	// Remove from all indexes
	delete(c.byAddress, address)
	c.removeFromIndexes(pool)

	return nil
}

// Count returns the total number of pools in the cache
func (c *poolCache) Count(ctx context.Context) (int, error) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	return len(c.byAddress), nil
}

// Clear removes all pools from the cache
func (c *poolCache) Clear(ctx context.Context) error {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.byAddress = make(map[common.Address]*types.PoolInfo)
	c.byTokenPair = make(map[string][]*types.PoolInfo)
	c.byProtocol = make(map[types.ProtocolType][]*types.PoolInfo)

	return nil
}

// addToIndexes adds a pool to secondary indexes
func (c *poolCache) addToIndexes(pool *types.PoolInfo) {
	// Add to token pair index
	pairKey := makeTokenPairKey(pool.Token0, pool.Token1)
	c.byTokenPair[pairKey] = append(c.byTokenPair[pairKey], pool)

	// Add to protocol index
	c.byProtocol[pool.Protocol] = append(c.byProtocol[pool.Protocol], pool)
}

// removeFromIndexes removes a pool from secondary indexes
func (c *poolCache) removeFromIndexes(pool *types.PoolInfo) {
	// Remove from token pair index
	pairKey := makeTokenPairKey(pool.Token0, pool.Token1)
	c.byTokenPair[pairKey] = removePoolFromSlice(c.byTokenPair[pairKey], pool.Address)
	if len(c.byTokenPair[pairKey]) == 0 {
		delete(c.byTokenPair, pairKey)
	}

	// Remove from protocol index
	c.byProtocol[pool.Protocol] = removePoolFromSlice(c.byProtocol[pool.Protocol], pool.Address)
	if len(c.byProtocol[pool.Protocol]) == 0 {
		delete(c.byProtocol, pool.Protocol)
	}
}

// makeTokenPairKey creates a consistent key for a token pair
func makeTokenPairKey(token0, token1 common.Address) string {
	// Always use the smaller address first for consistency
	if token0.Big().Cmp(token1.Big()) < 0 {
		return token0.Hex() + "-" + token1.Hex()
	}
	return token1.Hex() + "-" + token0.Hex()
}

// removePoolFromSlice removes a pool with the given address from a slice
func removePoolFromSlice(pools []*types.PoolInfo, address common.Address) []*types.PoolInfo {
	for i, pool := range pools {
		if pool.Address == address {
			return append(pools[:i], pools[i+1:]...)
		}
	}
	return pools
}