package mysql

import (
	"fmt"
	"net/url"
)

// Config holds MySQL connection settings. Required fields must be supplied
// by the caller; optional fields have production-safe defaults via [DefaultConfig].
//
// Note on Collation: go-sql-driver v1.8.x negotiates the connection collation
// via a 1-byte handshake ID (max 255). MariaDB 11.4+ collations such as
// utf8mb4_uca1400_as_cs carry IDs > 255 and cannot be set through the DSN
// collation parameter. Set the desired collation at the database/table level
// in your schema migrations instead.
type Config struct {
	Host            string `env:"EINHERJAR_MYSQL_HOST,required"`
	Port            int    `env:"EINHERJAR_MYSQL_PORT"                  envDefault:"3306"`
	User            string `env:"EINHERJAR_MYSQL_USER,required"`
	Password        string `env:"EINHERJAR_MYSQL_PASSWORD,required"`
	Name            string `env:"EINHERJAR_MYSQL_NAME,required"`
	MaxConns        int    `env:"EINHERJAR_MYSQL_MAX_CONNS"             envDefault:"5"`
	MinConns        int    `env:"EINHERJAR_MYSQL_MIN_CONNS"             envDefault:"2"`
	MaxConnLifetime string `env:"EINHERJAR_MYSQL_MAX_CONN_LIFETIME"     envDefault:"1h"`
	MaxConnIdleTime string `env:"EINHERJAR_MYSQL_MAX_CONN_IDLE_TIME"    envDefault:"30m"`
	// Charset is the connection character set. Defaults to "utf8mb4".
	Charset string `env:"EINHERJAR_MYSQL_CHARSET" envDefault:"utf8mb4"`
	// Loc is the IANA timezone name for time.Time ↔ MySQL DATETIME conversion. Defaults to "UTC".
	Loc string `env:"EINHERJAR_MYSQL_LOC" envDefault:"UTC"`
	// ParseTime controls whether DATE/DATETIME columns are mapped to time.Time. Defaults to "true".
	ParseTime string `env:"EINHERJAR_MYSQL_PARSE_TIME" envDefault:"true"`
}

// DefaultConfig returns a Config with all optional fields set to production-safe defaults.
// Callers must supply Host, Port, User, Password, and Name.
func DefaultConfig() Config {
	return Config{
		Port:            3306,
		MaxConns:        5,
		MinConns:        2,
		MaxConnLifetime: "1h",
		MaxConnIdleTime: "30m",
		Charset:         "utf8mb4",
		Loc:             "UTC",
		ParseTime:       "true",
	}
}

// DSN constructs a MySQL DSN from the configuration.
func (c Config) DSN() string {
	charset := c.Charset
	if charset == "" {
		charset = "utf8mb4"
	}
	loc := c.Loc
	if loc == "" {
		loc = "UTC"
	}
	parseTime := c.ParseTime
	if parseTime == "" {
		parseTime = "true"
	}
	q := url.Values{}
	q.Set("charset", charset)
	q.Set("loc", loc)
	q.Set("parseTime", parseTime)
	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?%s",
		c.User, c.Password, c.Host, c.Port, c.Name, q.Encode())
}