package dotenv

import (
	"errors"
	"log/slog"
	"reflect"
	"strconv"
	"strings"
)

// Assign env tag matching values from envMap
func Assign[T any](c *T, envMap map[string]string) error {
	if c == nil {
		return errors.New("nil arg")
	}

	slog.Info("env map", "v", envMap)

	val := reflect.Indirect(reflect.ValueOf(c))
	name := val.Type().Name()
	for i := range val.NumField() {
		f := val.Type().Field(i)
		tag := f.Tag.Get("env")
		if tag == "" {
			continue
		}

		var v string
		var ok bool
		if multiTag := strings.Split(tag, ","); len(multiTag) > 1 {
			// multi tags like env:"DB_URL,PG_DB_URL"
			for _, mt := range multiTag {
				if v, ok = envMap[strings.TrimSpace(mt)]; ok {
					break
				}
			}
		} else {
			v, ok = envMap[tag]
		}

		if !ok {
			continue
		}

		field := val.FieldByName(f.Name)
		if !field.IsValid() {
			continue
		}

		switch f.Type.Kind() {
		case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
			if v, err := strconv.ParseInt(v, 10, 64); err != nil {
				return err
			} else {
				field.SetInt(v)
			}
		case reflect.Float32, reflect.Float64:
			if v, err := strconv.ParseFloat(v, 10); err != nil {
				return err
			} else {
				field.SetFloat(v)
			}
		case reflect.Bool:
			if strings.EqualFold(v, "true") {
				field.SetBool(true)
			} else {
				field.SetBool(false)
			}

		default:
			field.SetString(v)
		}

		if name == "" {
			slog.Info("override value from env", "field", f.Name)
		} else {
			slog.Info("override value from env", "type", name, "field", f.Name)
		}
	}

	return nil
}