package config

import (
	"fmt"
	"os"
	"regexp"

	"gopkg.in/yaml.v3"
)

type Config struct {
	Database DatabaseConfig `yaml:"database"`
	AI       AIConfig       `yaml:"ai"`
	Security SecurityConfig `yaml:"security"`
	GRPC     GRPCConfig     `yaml:"grpc"`
	Logging  LoggingConfig  `yaml:"logging"`
}

type DatabaseConfig struct {
	Host     string `yaml:"host"`
	Port     int    `yaml:"port"`
	Name     string `yaml:"name"`
	User     string `yaml:"user"`
	Password string `yaml:"password"`
	SSLMode  string `yaml:"ssl_mode"`
	MaxConns int    `yaml:"max_conns"`
	MinConns int    `yaml:"min_conns"`
}

type AIConfig struct {
	OpenAIKey     string `yaml:"openai_key"`
	PerplexityKey string `yaml:"perplexity_key"`
}

type SecurityConfig struct {
	JWTSecret    string `yaml:"jwt_secret"`
	CryptoSecret string `yaml:"crypto_secret"`
}

type GRPCConfig struct {
	Port           int `yaml:"port"`
	MaxConnections int `yaml:"max_connections"`
}

type LoggingConfig struct {
	Level string `yaml:"level"`
}

func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	data = []byte(expandEnvWithDefaults(string(data)))

	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
	}

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

	return &cfg, nil
}

func expandEnvWithDefaults(s string) string {
	re := regexp.MustCompile(`\$\{([^:}]+):([^}]*)\}`)
	result := re.ReplaceAllStringFunc(s, func(match string) string {
		parts := re.FindStringSubmatch(match)
		if len(parts) != 3 {
			return match
		}
		envVar := parts[1]
		defaultVal := parts[2]
		if val := os.Getenv(envVar); val != "" {
			return val
		}
		return defaultVal
	})
	return os.ExpandEnv(result)
}

func (c *Config) validate() error {
	if c.Database.Host == "" {
		return fmt.Errorf("database host is required")
	}
	if c.Database.Name == "" {
		return fmt.Errorf("database name is required")
	}
	if c.Database.User == "" {
		return fmt.Errorf("database user is required")
	}
	if c.Database.Password == "" {
		return fmt.Errorf("database password is required")
	}
	if c.Security.JWTSecret == "" {
		return fmt.Errorf("JWT secret is required")
	}
	if c.Security.CryptoSecret == "" {
		return fmt.Errorf("crypto secret is required")
	}
	return nil
}

func (c *Config) DatabaseURL() string {
	return fmt.Sprintf("postgres://%s:%s@%s:%d/%s?sslmode=%s",
		c.Database.User, c.Database.Password, c.Database.Host, c.Database.Port, c.Database.Name, c.Database.SSLMode)
}