package config

import (
	"errors"
	"fmt"
	"net"
	"os"
	"strconv"
)

type Config struct {
	HTTPAddr    string
	MySQLDSN    string
	MaxOpen     int
	MaxIdle     int
	MetricsAddr string
}

func Load() (Config, error) { return FromEnv(os.Getenv) }
func FromEnv(get func(string) string) (Config, error) {
	c := Config{HTTPAddr: get("ORBIT_HTTP_ADDR"), MySQLDSN: get("ORBIT_MYSQL_DSN"), MaxOpen: 20, MaxIdle: 5, MetricsAddr: get("ORBIT_METRICS_ADDR")}
	if c.HTTPAddr == "" {
		c.HTTPAddr = "127.0.0.1:8080"
	}
	if _, _, err := net.SplitHostPort(c.HTTPAddr); err != nil {
		return Config{}, errors.New("invalid ORBIT_HTTP_ADDR")
	}
	if c.MySQLDSN == "" {
		return Config{}, errors.New("ORBIT_MYSQL_DSN is required")
	}
	for _, field := range []struct {
		name string
		dst  *int
	}{{"ORBIT_DB_MAX_OPEN", &c.MaxOpen}, {"ORBIT_DB_MAX_IDLE", &c.MaxIdle}} {
		if raw := get(field.name); raw != "" {
			n, err := strconv.Atoi(raw)
			if err != nil || n < 0 {
				return Config{}, fmt.Errorf("%s must be a nonnegative integer", field.name)
			}
			*field.dst = n
		}
	}
	if c.MaxOpen <= 0 || c.MaxIdle > c.MaxOpen {
		return Config{}, errors.New("database pool requires 0 <= max_idle <= max_open and max_open > 0")
	}
	if c.MetricsAddr != "" {
		_, port, err := net.SplitHostPort(c.MetricsAddr)
		n, parseErr := strconv.Atoi(port)
		if err != nil || parseErr != nil || n < 0 || n > 65535 {
			return Config{}, errors.New("invalid ORBIT_METRICS_ADDR")
		}
	}
	return c, nil
}