package config

import (
	"errors"
	"fmt"
	"os"
	"reflect"
	"strconv"
	"strings"
)

func getEnvVar(value reflect.Value, rtype reflect.Type, counter int, prefix string) error {
	if value.Kind() != reflect.Ptr {
		return errors.New("not a pointer value")
	}
	f := reflect.StructField{}
	if counter != -1 {
		f = rtype.Field(counter)
	}
	value = reflect.Indirect(value)
	fName := strings.ToUpper(f.Name)
	if prefix != "" {
		prefix = strings.TrimLeft(prefix, "_")
	}

	env := os.Getenv(prefix + fName)
	if err := selector(env, &value); err != nil {
		return fmt.Errorf("could set value: %w", err)
	}
	if value.Kind() == reflect.Struct {
		for i := 0; i < value.NumField(); i++ {
			if err := getEnvVar(value.Field(i).Addr(), value.Type(), i, prefix+fName+"_"); err != nil {
				return fmt.Errorf("could not apply env var: %w", err)
			}
		}
	}
	return nil
}

func parseToStruct(value reflect.Value, rtype reflect.Type, counter int, prefix string, index map[string]string) error {
	if value.Kind() != reflect.Ptr {
		return errors.New("not a pointer value")
	}
	f := reflect.StructField{}
	if counter != -1 {
		f = rtype.Field(counter)
	}
	value = reflect.Indirect(value)
	fName := strings.ToLower(f.Name)
	if prefix != "" {
		prefix = strings.TrimLeft(prefix, ".")
	}

	env := index[prefix+fName]
	if err := selector(env, &value); err != nil {
		return fmt.Errorf("could set value: %w", err)
	}
	if value.Kind() == reflect.Struct {
		for i := 0; i < value.NumField(); i++ {
			if err := parseToStruct(value.Field(i).Addr(), value.Type(), i, prefix+fName+".", index); err != nil {
				return fmt.Errorf("could not apply env var: %w", err)
			}
		}
	}
	return nil
}

func selector(env string, value *reflect.Value) error {
	if env != "" {
		//nolint:exhaustive
		switch value.Kind() {
		case reflect.Int:
			envI, err := strconv.Atoi(env)
			if err != nil {
				return fmt.Errorf("could not parse to int: %w", err)
			}
			value.SetInt(int64(envI))
		case reflect.String:
			value.SetString(env)
		case reflect.Bool:
			envB, err := strconv.ParseBool(env)
			if err != nil {
				return fmt.Errorf("could not parse bool: %w", err)
			}
			value.SetBool(envB)
		}
	}
	return nil
}