package postgres

import (
	"context"
	"fmt"
	"os"

	"github.com/jackc/pgx/v5"
)

// Config holds the database configuration.
type Config struct {
	ctx      context.Context
	Host     string
	Port     string
	User     string
	Password string
	DBName   string
	SSLMode  string
}

// ConfigOption is a functional option for Config.
type ConfigOption func(*Config)

// WithContext sets the context on the config.
func WithContext(ctx context.Context) ConfigOption {
	return func(c *Config) {
		c.ctx = ctx
	}
}

// NewConfig creates a new database configuration from environment variables.
// DB_HOST, DB_PORT, DB_USER, DB_PASSWORD, DB_SSL_MODE fall back to sensible
// defaults. DB_NAME is required and must be set in the environment.
func NewConfig(opts ...ConfigOption) *Config {
	c := &Config{
		Host:     getEnvOrDefault("DB_HOST", "localhost"),
		Port:     getEnvOrDefault("DB_PORT", "5432"),
		User:     getEnvOrDefault("DB_USER", "postgres"),
		Password: getEnvOrDefault("DB_PASSWORD", "postgres"),
		DBName:   os.Getenv("DB_NAME"),
		SSLMode:  getEnvOrDefault("DB_SSL_MODE", "disable"),
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

// DSN returns the database connection string in key=value format.
func (c *Config) DSN() string {
	return fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=%s",
		c.Host, c.Port, c.User, c.Password, c.DBName, c.SSLMode)
}

// Connect creates a new single database connection using pgx.
func (c *Config) Connect() (*pgx.Conn, error) {
	conn, err := pgx.Connect(c.Context(), c.DSN())
	if err != nil {
		return nil, fmt.Errorf("failed to connect to database: %w", err)
	}
	return conn, nil
}

// Context returns the context associated with this config, defaulting to
// context.Background() if none was set.
func (c *Config) Context() context.Context {
	if c.ctx == nil {
		c.ctx = context.Background()
	}
	return c.ctx
}

// getEnvOrDefault returns the value of an environment variable or a fallback.
func getEnvOrDefault(key, fallback string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return fallback
}