package config

import (
	"fmt"
	"net/url"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

// Config represents the application configuration
type Config struct {
	Arbitrum  ArbitrumConfig  `yaml:"arbitrum"`
	Bot       BotConfig       `yaml:"bot"`
	Uniswap   UniswapConfig   `yaml:"uniswap"`
	Log       LogConfig       `yaml:"log"`
	Database  DatabaseConfig  `yaml:"database"`
	Ethereum  EthereumConfig  `yaml:"ethereum"`
	Contracts ContractsConfig `yaml:"contracts"`
	Arbitrage ArbitrageConfig `yaml:"arbitrage"`
}

// ArbitrumConfig represents the Arbitrum node configuration
type ArbitrumConfig struct {
	// Primary RPC endpoint
	RPCEndpoint string `yaml:"rpc_endpoint"`
	// WebSocket endpoint for Arbitrum node (optional)
	WSEndpoint string `yaml:"ws_endpoint"`
	// Chain ID for Arbitrum (42161 for mainnet)
	ChainID int64 `yaml:"chain_id"`
	// Rate limiting configuration for RPC endpoint
	RateLimit RateLimitConfig `yaml:"rate_limit"`
	// Fallback RPC endpoints
	FallbackEndpoints []EndpointConfig `yaml:"fallback_endpoints"`
}

// EndpointConfig represents a fallback RPC endpoint configuration
type EndpointConfig struct {
	// RPC endpoint URL
	URL string `yaml:"url"`
	// Rate limiting configuration for this endpoint
	RateLimit RateLimitConfig `yaml:"rate_limit"`
}

// RateLimitConfig represents rate limiting configuration
type RateLimitConfig struct {
	// Maximum requests per second
	RequestsPerSecond int `yaml:"requests_per_second"`
	// Maximum concurrent requests
	MaxConcurrent int `yaml:"max_concurrent"`
	// Burst size for rate limiting
	Burst int `yaml:"burst"`
}

// BotConfig represents the bot configuration
type BotConfig struct {
	// Enable or disable the bot
	Enabled bool `yaml:"enabled"`
	// Polling interval in seconds
	PollingInterval int `yaml:"polling_interval"`
	// Minimum profit threshold in USD
	MinProfitThreshold float64 `yaml:"min_profit_threshold"`
	// Gas price multiplier (for faster transactions)
	GasPriceMultiplier float64 `yaml:"gas_price_multiplier"`
	// Maximum number of concurrent workers for processing
	MaxWorkers int `yaml:"max_workers"`
	// Buffer size for channels
	ChannelBufferSize int `yaml:"channel_buffer_size"`
	// Timeout for RPC calls in seconds
	RPCTimeout int `yaml:"rpc_timeout"`
}

// UniswapConfig represents the Uniswap configuration
type UniswapConfig struct {
	// Factory contract address
	FactoryAddress string `yaml:"factory_address"`
	// Position manager contract address
	PositionManagerAddress string `yaml:"position_manager_address"`
	// Supported fee tiers
	FeeTiers []int64 `yaml:"fee_tiers"`
	// Cache configuration for pool data
	Cache CacheConfig `yaml:"cache"`
}

// CacheConfig represents caching configuration
type CacheConfig struct {
	// Enable or disable caching
	Enabled bool `yaml:"enabled"`
	// Cache expiration time in seconds
	Expiration int `yaml:"expiration"`
	// Maximum cache size
	MaxSize int `yaml:"max_size"`
}

// LogConfig represents the logging configuration
type LogConfig struct {
	// Log level (debug, info, warn, error)
	Level string `yaml:"level"`
	// Log format (json, text)
	Format string `yaml:"format"`
	// Log file path (empty for stdout)
	File string `yaml:"file"`
}

// DatabaseConfig represents the database configuration
type DatabaseConfig struct {
	// Database file path
	File string `yaml:"file"`
	// Maximum number of open connections
	MaxOpenConnections int `yaml:"max_open_connections"`
	// Maximum number of idle connections
	MaxIdleConnections int `yaml:"max_idle_connections"`
}

// EthereumConfig represents the Ethereum account configuration
type EthereumConfig struct {
	// Private key for transaction signing
	PrivateKey string `yaml:"private_key"`
	// Account address
	AccountAddress string `yaml:"account_address"`
	// Gas price multiplier (for faster transactions)
	GasPriceMultiplier float64 `yaml:"gas_price_multiplier"`
}

// ContractsConfig represents the smart contract addresses
type ContractsConfig struct {
	// Arbitrage executor contract address
	ArbitrageExecutor string `yaml:"arbitrage_executor"`
	// Flash swapper contract address
	FlashSwapper string `yaml:"flash_swapper"`
	// Authorized caller addresses
	AuthorizedCallers []string `yaml:"authorized_callers"`
	// Authorized DEX addresses
	AuthorizedDEXes []string `yaml:"authorized_dexes"`
}

// Load loads the configuration from a file
func Load(filename string) (*Config, error) {
	// Read the config file
	data, err := os.ReadFile(filename)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	// Expand environment variables in the raw YAML
	expandedData := expandEnvVars(string(data))

	// Parse the YAML
	var config Config
	if err := yaml.Unmarshal([]byte(expandedData), &config); err != nil {
		return nil, fmt.Errorf("failed to parse config file: %w", err)
	}

	// Override with environment variables if they exist
	config.OverrideWithEnv()

	return &config, nil
}

// expandEnvVars expands ${VAR} and $VAR patterns in the given string
func expandEnvVars(s string) string {
	// Pattern to match ${VAR} and $VAR
	envVarPattern := regexp.MustCompile(`\$\{([^}]+)\}|\$([A-Za-z_][A-Za-z0-9_]*)`)

	return envVarPattern.ReplaceAllStringFunc(s, func(match string) string {
		var varName string

		// Handle ${VAR} format
		if strings.HasPrefix(match, "${") && strings.HasSuffix(match, "}") {
			varName = match[2 : len(match)-1]
		} else if strings.HasPrefix(match, "$") {
			// Handle $VAR format
			varName = match[1:]
		}

		// Get environment variable value
		if value := os.Getenv(varName); value != "" {
			return value
		}

		// Return empty string if environment variable is not set
		// This prevents invalid YAML when variables are missing
		return ""
	})
}

// OverrideWithEnv overrides configuration with environment variables
func (c *Config) OverrideWithEnv() {
	// Override RPC endpoint
	if rpcEndpoint := os.Getenv("ARBITRUM_RPC_ENDPOINT"); rpcEndpoint != "" {
		c.Arbitrum.RPCEndpoint = rpcEndpoint
	}

	// Override WebSocket endpoint
	if wsEndpoint := os.Getenv("ARBITRUM_WS_ENDPOINT"); wsEndpoint != "" {
		c.Arbitrum.WSEndpoint = wsEndpoint
	}

	// Override fallback endpoints from environment
	if fallbackEndpoints := os.Getenv("ARBITRUM_FALLBACK_ENDPOINTS"); fallbackEndpoints != "" {
		endpoints := strings.Split(fallbackEndpoints, ",")
		c.Arbitrum.FallbackEndpoints = make([]EndpointConfig, 0, len(endpoints))
		for _, endpoint := range endpoints {
			endpoint = strings.TrimSpace(endpoint)
			if endpoint != "" {
				c.Arbitrum.FallbackEndpoints = append(c.Arbitrum.FallbackEndpoints, EndpointConfig{
					URL: endpoint,
					RateLimit: RateLimitConfig{
						RequestsPerSecond: 100,
						MaxConcurrent:     10,
						Burst:             20,
					},
				})
			}
		}
	}

	// Override rate limit settings
	if rps := os.Getenv("RPC_REQUESTS_PER_SECOND"); rps != "" {
		if val, err := strconv.Atoi(rps); err == nil {
			c.Arbitrum.RateLimit.RequestsPerSecond = val
		}
	}

	if maxConcurrent := os.Getenv("RPC_MAX_CONCURRENT"); maxConcurrent != "" {
		if val, err := strconv.Atoi(maxConcurrent); err == nil {
			c.Arbitrum.RateLimit.MaxConcurrent = val
		}
	}

	// Override bot settings
	if maxWorkers := os.Getenv("BOT_MAX_WORKERS"); maxWorkers != "" {
		if val, err := strconv.Atoi(maxWorkers); err == nil {
			c.Bot.MaxWorkers = val
		}
	}

	if channelBufferSize := os.Getenv("BOT_CHANNEL_BUFFER_SIZE"); channelBufferSize != "" {
		if val, err := strconv.Atoi(channelBufferSize); err == nil {
			c.Bot.ChannelBufferSize = val
		}
	}

	// Override Ethereum settings
	if privateKey := os.Getenv("ETHEREUM_PRIVATE_KEY"); privateKey != "" {
		c.Ethereum.PrivateKey = privateKey
	}

	if accountAddress := os.Getenv("ETHEREUM_ACCOUNT_ADDRESS"); accountAddress != "" {
		c.Ethereum.AccountAddress = accountAddress
	}

	if gasPriceMultiplier := os.Getenv("ETHEREUM_GAS_PRICE_MULTIPLIER"); gasPriceMultiplier != "" {
		if val, err := strconv.ParseFloat(gasPriceMultiplier, 64); err == nil {
			c.Ethereum.GasPriceMultiplier = val
		}
	}

	// Override contract addresses
	if arbitrageExecutor := os.Getenv("CONTRACT_ARBITRAGE_EXECUTOR"); arbitrageExecutor != "" {
		c.Contracts.ArbitrageExecutor = arbitrageExecutor
	}

	if flashSwapper := os.Getenv("CONTRACT_FLASH_SWAPPER"); flashSwapper != "" {
		c.Contracts.FlashSwapper = flashSwapper
	}
}

// ValidateEnvironmentVariables validates all required environment variables
func (c *Config) ValidateEnvironmentVariables() error {
	// Validate RPC endpoint
	if c.Arbitrum.RPCEndpoint == "" {
		return fmt.Errorf("ARBITRUM_RPC_ENDPOINT environment variable is required")
	}

	if err := validateRPCEndpoint(c.Arbitrum.RPCEndpoint); err != nil {
		return fmt.Errorf("invalid ARBITRUM_RPC_ENDPOINT: %w", err)
	}

	// Validate WebSocket endpoint if provided
	if c.Arbitrum.WSEndpoint != "" {
		if err := validateRPCEndpoint(c.Arbitrum.WSEndpoint); err != nil {
			return fmt.Errorf("invalid ARBITRUM_WS_ENDPOINT: %w", err)
		}
	}

	// Validate Ethereum private key
	if c.Ethereum.PrivateKey == "" {
		return fmt.Errorf("ETHEREUM_PRIVATE_KEY environment variable is required")
	}

	// Validate account address
	if c.Ethereum.AccountAddress == "" {
		return fmt.Errorf("ETHEREUM_ACCOUNT_ADDRESS environment variable is required")
	}

	// Validate contract addresses
	if c.Contracts.ArbitrageExecutor == "" {
		return fmt.Errorf("CONTRACT_ARBITRAGE_EXECUTOR environment variable is required")
	}

	if c.Contracts.FlashSwapper == "" {
		return fmt.Errorf("CONTRACT_FLASH_SWAPPER environment variable is required")
	}

	// Validate numeric values
	if c.Arbitrum.RateLimit.RequestsPerSecond < 0 {
		return fmt.Errorf("RPC_REQUESTS_PER_SECOND must be non-negative")
	}

	if c.Arbitrum.RateLimit.MaxConcurrent < 0 {
		return fmt.Errorf("RPC_MAX_CONCURRENT must be non-negative")
	}

	if c.Bot.MaxWorkers <= 0 {
		return fmt.Errorf("BOT_MAX_WORKERS must be positive")
	}

	if c.Bot.ChannelBufferSize < 0 {
		return fmt.Errorf("BOT_CHANNEL_BUFFER_SIZE must be non-negative")
	}

	if c.Ethereum.GasPriceMultiplier < 0 {
		return fmt.Errorf("ETHEREUM_GAS_PRICE_MULTIPLIER must be non-negative")
	}

	return nil
}

// validateRPCEndpoint validates RPC endpoint URL for security and format
func validateRPCEndpoint(endpoint string) error {
	if endpoint == "" {
		return fmt.Errorf("RPC endpoint cannot be empty")
	}

	u, err := url.Parse(endpoint)
	if err != nil {
		return fmt.Errorf("invalid RPC endpoint URL: %w", err)
	}

	// Check for valid schemes
	switch u.Scheme {
	case "http", "https", "ws", "wss":
		// Valid schemes
	default:
		return fmt.Errorf("invalid RPC scheme: %s (must be http, https, ws, or wss)", u.Scheme)
	}

	// Check for localhost/private networks in production
	if strings.Contains(u.Hostname(), "localhost") || strings.Contains(u.Hostname(), "127.0.0.1") {
		// Allow localhost only if explicitly enabled
		if os.Getenv("MEV_BOT_ALLOW_LOCALHOST") != "true" {
			return fmt.Errorf("localhost RPC endpoints not allowed in production (set MEV_BOT_ALLOW_LOCALHOST=true to override)")
		}
	}

	// Validate hostname is not empty
	if u.Hostname() == "" {
		return fmt.Errorf("RPC endpoint must have a valid hostname")
	}

	return nil
}

// ArbitrageConfig represents the arbitrage service configuration
type ArbitrageConfig struct {
	// Enable or disable arbitrage service
	Enabled bool `yaml:"enabled"`

	// Contract addresses
	ArbitrageContractAddress string `yaml:"arbitrage_contract_address"`
	FlashSwapContractAddress string `yaml:"flash_swap_contract_address"`

	// Profitability settings
	MinProfitWei           int64   `yaml:"min_profit_wei"`
	MinROIPercent          float64 `yaml:"min_roi_percent"`
	MinSignificantSwapSize int64   `yaml:"min_significant_swap_size"`
	SlippageTolerance      float64 `yaml:"slippage_tolerance"`

	// Scanning configuration
	MinScanAmountWei int64 `yaml:"min_scan_amount_wei"`
	MaxScanAmountWei int64 `yaml:"max_scan_amount_wei"`

	// Gas configuration
	MaxGasPriceWei int64 `yaml:"max_gas_price_wei"`

	// Execution limits
	MaxConcurrentExecutions  int `yaml:"max_concurrent_executions"`
	MaxOpportunitiesPerEvent int `yaml:"max_opportunities_per_event"`

	// Timing settings
	OpportunityTTL      time.Duration `yaml:"opportunity_ttl"`
	MaxPathAge          time.Duration `yaml:"max_path_age"`
	StatsUpdateInterval time.Duration `yaml:"stats_update_interval"`

	// Pool discovery configuration
	PoolDiscoveryConfig PoolDiscoveryConfig `yaml:"pool_discovery"`
}

// PoolDiscoveryConfig represents pool discovery service configuration
type PoolDiscoveryConfig struct {
	// Enable or disable pool discovery
	Enabled bool `yaml:"enabled"`

	// Block range to scan for new pools
	BlockRange uint64 `yaml:"block_range"`

	// Polling interval for new pools
	PollingInterval time.Duration `yaml:"polling_interval"`

	// DEX factory addresses to monitor
	FactoryAddresses []string `yaml:"factory_addresses"`

	// Minimum liquidity threshold for pools
	MinLiquidityWei int64 `yaml:"min_liquidity_wei"`

	// Cache configuration
	CacheSize int           `yaml:"cache_size"`
	CacheTTL  time.Duration `yaml:"cache_ttl"`
}