package mapstructure

import (

	"errors"

	"reflect"

	"strconv"

	"strings"

	"time"

)

// typedDecodeHook takes a raw DecodeHookFunc (an interface{}) and turns

// it into the proper DecodeHookFunc type, such as DecodeHookFuncType.

func typedDecodeHook(h DecodeHookFunc) DecodeHookFunc {

	// Create variables here so we can reference them with the reflect pkg

	var f1 DecodeHookFuncType

	var f2 DecodeHookFuncKind

	// Fill in the variables into this interface and the rest is done

	// automatically using the reflect package.

	potential := []interface{}{f1, f2}

	v := reflect.ValueOf(h)

	vt := v.Type()

	for _, raw := range potential {

		pt := reflect.ValueOf(raw).Type()

		if vt.ConvertibleTo(pt) {

			return v.Convert(pt).Interface()

		}

	}

	return nil

}

// DecodeHookExec executes the given decode hook. This should be used

// since it'll naturally degrade to the older backwards compatible DecodeHookFunc

// that took reflect.Kind instead of reflect.Type.

func DecodeHookExec(

	raw DecodeHookFunc,

	from reflect.Type, to reflect.Type,

	data interface{}) (interface{}, error) {

	switch f := typedDecodeHook(raw).(type) {

	case DecodeHookFuncType:

		return f(from, to, data)

	case DecodeHookFuncKind:

		return f(from.Kind(), to.Kind(), data)

	default:

		return nil, errors.New("invalid decode hook signature")

	}

}

// ComposeDecodeHookFunc creates a single DecodeHookFunc that

// automatically composes multiple DecodeHookFuncs.

//

// The composed funcs are called in order, with the result of the

// previous transformation.

func ComposeDecodeHookFunc(fs ...DecodeHookFunc) DecodeHookFunc {

	return func(

		f reflect.Type,

		t reflect.Type,

		data interface{}) (interface{}, error) {

		var err error

		for _, f1 := range fs {

			data, err = DecodeHookExec(f1, f, t, data)

			if err != nil {

				return nil, err

			}

			// Modify the from kind to be correct with the new data

			f = nil

			if val := reflect.ValueOf(data); val.IsValid() {

				f = val.Type()

			}

		}

		return data, nil

	}

}

// StringToSliceHookFunc returns a DecodeHookFunc that converts

// string to []string by splitting on the given sep.

func StringToSliceHookFunc(sep string) DecodeHookFunc {

	return func(

		f reflect.Kind,

		t reflect.Kind,

		data interface{}) (interface{}, error) {

		if f != reflect.String || t != reflect.Slice {

			return data, nil

		}

		raw := data.(string)

		if raw == "" {

			return []string{}, nil

		}

		return strings.Split(raw, sep), nil

	}

}

// StringToTimeDurationHookFunc returns a DecodeHookFunc that converts

// strings to time.Duration.

func StringToTimeDurationHookFunc() DecodeHookFunc {

	return func(

		f reflect.Type,

		t reflect.Type,

		data interface{}) (interface{}, error) {

		if f.Kind() != reflect.String {

			return data, nil

		}

		if t != reflect.TypeOf(time.Duration(5)) {

			return data, nil

		}

		// Convert it by parsing

		return time.ParseDuration(data.(string))

	}

}

// StringToTimeHookFunc returns a DecodeHookFunc that converts

// strings to time.Time.

func StringToTimeHookFunc(layout string) DecodeHookFunc {

	return func(

		f reflect.Type,

		t reflect.Type,

		data interface{}) (interface{}, error) {

		if f.Kind() != reflect.String {

			return data, nil

		}

		if t != reflect.TypeOf(time.Time{}) {

			return data, nil

		}

		// Convert it by parsing

		return time.Parse(layout, data.(string))

	}

}

// WeaklyTypedHook is a DecodeHookFunc which adds support for weak typing to

// the decoder.

//

// Note that this is significantly different from the WeaklyTypedInput option

// of the DecoderConfig.

func WeaklyTypedHook(

	f reflect.Kind,

	t reflect.Kind,

	data interface{}) (interface{}, error) {

	dataVal := reflect.ValueOf(data)

	switch t {

	case reflect.String:

		switch f {

		case reflect.Bool:

			if dataVal.Bool() {

				return "1", nil

			}

			return "0", nil

		case reflect.Float32:

			return strconv.FormatFloat(dataVal.Float(), 'f', -1, 64), nil

		case reflect.Int:

			return strconv.FormatInt(dataVal.Int(), 10), nil

		case reflect.Slice:

			dataType := dataVal.Type()

			elemKind := dataType.Elem().Kind()

			if elemKind == reflect.Uint8 {

				return string(dataVal.Interface().([]uint8)), nil

			}

		case reflect.Uint:

			return strconv.FormatUint(dataVal.Uint(), 10), nil

		}

	}

	return data, nil

}