package database

import (
	"fmt"
	"os"
	"time"

	"github.com/prometheus/client_golang/prometheus"
)

// Config represents the database configuration structure
type Config struct {
	// MySQL configuration (use this OR Postgres, not both)
	MySQL *MySQLConfig `yaml:"mysql,omitempty"`
	// Postgres configuration (use this OR MySQL, not both)
	Postgres *PostgresConfig `yaml:"postgres,omitempty"`

	// Legacy flat PostgreSQL format (deprecated, for backward compatibility only)
	// If neither MySQL nor Postgres is set, these fields will be used for PostgreSQL
	User    string `yaml:"user,omitempty"`
	Pass    string `yaml:"pass,omitempty"`
	Host    string `yaml:"host,omitempty"`
	Port    uint16 `yaml:"port,omitempty"`
	Name    string `yaml:"name,omitempty"`
	SSLMode string `yaml:"sslmode,omitempty"`
}

// MySQLConfig represents the MySQL database configuration
type MySQLConfig struct {
	DSN    string `yaml:"dsn" default:"" flag:"dsn" usage:"Database DSN"`
	User   string `yaml:"user" default:"" flag:"user"`
	Pass   string `yaml:"pass" default:"" flag:"pass"`
	DBName string `yaml:"name,omitempty"` // Optional database name override
}

// PostgresConfig represents the PostgreSQL database configuration
type PostgresConfig struct {
	User    string `yaml:"user"`
	Pass    string `yaml:"pass"`
	Host    string `yaml:"host"`
	Port    uint16 `yaml:"port"`
	Name    string `yaml:"name"`
	SSLMode string `yaml:"sslmode"`
}

// DBConfig is a legacy alias for MySQLConfig
type DBConfig = MySQLConfig

// Validate ensures the configuration is valid and unambiguous
func (c *Config) Validate() error {
	hasMySQL := c.MySQL != nil
	hasPostgres := c.Postgres != nil
	hasLegacy := c.User != "" || c.Host != "" || c.Port != 0 || c.Name != ""

	count := 0
	if hasMySQL {
		count++
	}
	if hasPostgres {
		count++
	}
	if hasLegacy {
		count++
	}

	if count == 0 {
		return fmt.Errorf("no database configuration provided")
	}
	if count > 1 {
		return fmt.Errorf("multiple database configurations provided (only one allowed)")
	}

	return nil
}

// ConfigOptions allows customization of database opening behavior
type ConfigOptions struct {
	// ConfigFiles is a list of config file paths to search for database configuration
	ConfigFiles []string

	// EnablePoolMonitoring enables connection pool metrics collection
	EnablePoolMonitoring bool

	// PrometheusRegisterer for metrics collection. If nil, no metrics are collected.
	PrometheusRegisterer prometheus.Registerer

	// Connection pool settings
	MaxOpenConns    int
	MaxIdleConns    int
	ConnMaxLifetime time.Duration
}

// getConfigFiles returns the list of config files to search for database configuration.
// If DATABASE_CONFIG_FILE environment variable is set, it returns that single file.
// Otherwise, it returns the default paths.
func getConfigFiles() []string {
	if configFile := os.Getenv("DATABASE_CONFIG_FILE"); configFile != "" {
		return []string{configFile}
	}
	return []string{"database.yaml", "/vault/secrets/database.yaml"}
}

// DefaultConfigOptions returns the standard configuration options used by API package
func DefaultConfigOptions() ConfigOptions {
	return ConfigOptions{
		ConfigFiles:          getConfigFiles(),
		EnablePoolMonitoring: true,
		PrometheusRegisterer: prometheus.DefaultRegisterer,
		MaxOpenConns:         25,
		MaxIdleConns:         10,
		ConnMaxLifetime:      3 * time.Minute,
	}
}

// MonitorConfigOptions returns configuration options optimized for Monitor package
func MonitorConfigOptions() ConfigOptions {
	return ConfigOptions{
		ConfigFiles:          getConfigFiles(),
		EnablePoolMonitoring: false, // Monitor doesn't need metrics
		PrometheusRegisterer: nil,   // No Prometheus dependency
		MaxOpenConns:         10,
		MaxIdleConns:         5,
		ConnMaxLifetime:      3 * time.Minute,
	}
}