package reflect

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

var (
	allowTags = []string{"json", "yaml", "xml", "name"}
)

var (
	ErrValueAssociated = errors.New("value cannot be associated")
)

func findField(v reflect.Value, field string) reflect.Value {
	var (
		pos       int
		tagValue  string
		refType   reflect.Type
		fieldType reflect.StructField
	)
	refType = v.Type()
	for i := 0; i < refType.NumField(); i++ {
		fieldType = refType.Field(i)
		for _, tagName := range allowTags {
			tagValue = fieldType.Tag.Get(tagName)
			if tagValue == "" {
				continue
			}
			if pos = strings.IndexByte(tagValue, ','); pos != -1 {
				tagValue = tagValue[:pos]
			}
			if tagValue == field {
				return v.Field(i)
			}
		}
	}
	return v.FieldByName(field)
}

func Assign(variable reflect.Value, value interface{}) (err error) {
	return safeAssignment(variable, value)
}

func safeAssignment(variable reflect.Value, value interface{}) (err error) {
	var (
		n    int64
		un   uint64
		fn   float64
		kind reflect.Kind
	)
	rv := reflect.ValueOf(value)
	kind = variable.Kind()
	if kind != reflect.Slice && kind != reflect.Array && kind != reflect.Map && kind == rv.Kind() {
		variable.Set(rv)
		return
	}
	switch kind {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetInt(rv.Int())
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetInt(int64(rv.Uint()))
		case reflect.Float32, reflect.Float64:
			variable.SetInt(int64(rv.Float()))
		case reflect.String:
			if n, err = strconv.ParseInt(rv.String(), 10, 64); err == nil {
				variable.SetInt(n)
			}
		default:
			err = fmt.Errorf("integer value can not assign %s", rv.Kind())
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetUint(uint64(rv.Int()))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetUint(rv.Uint())
		case reflect.Float32, reflect.Float64:
			variable.SetUint(uint64(rv.Float()))
		case reflect.String:
			if un, err = strconv.ParseUint(rv.String(), 10, 64); err == nil {
				variable.SetUint(un)
			}
		default:
			err = fmt.Errorf("unsigned integer value can not assign %s", rv.Kind())
		}
	case reflect.Float32, reflect.Float64:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetFloat(float64(rv.Int()))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetFloat(float64(rv.Uint()))
		case reflect.Float32, reflect.Float64:
			variable.SetFloat(rv.Float())
		case reflect.String:
			if fn, err = strconv.ParseFloat(rv.String(), 64); err == nil {
				variable.SetFloat(fn)
			}
		default:
			err = fmt.Errorf("decimal value can not assign %s", rv.Kind())
		}
	case reflect.String:
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			variable.SetString(strconv.FormatInt(rv.Int(), 10))
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			variable.SetString(strconv.FormatUint(rv.Uint(), 10))
		case reflect.Float32, reflect.Float64:
			variable.SetString(strconv.FormatFloat(rv.Float(), 'f', -1, 64))
		case reflect.String:
			variable.SetString(rv.String())
		default:
			variable.SetString(fmt.Sprint(value))
		}
	case reflect.Interface:
		variable.Set(rv)
	default:
		err = fmt.Errorf("unsupported kind %s", kind)
	}
	return
}

func Set(hacky interface{}, field string, value interface{}) (err error) {
	var (
		n        int
		refField reflect.Value
	)
	refVal := reflect.ValueOf(hacky)
	if refVal.Kind() == reflect.Ptr {
		refVal = reflect.Indirect(refVal)
	}
	if refVal.Kind() != reflect.Struct {
		return fmt.Errorf("%s kind is %v", refVal.Type().String(), refField.Kind())
	}
	refField = findField(refVal, field)
	if !refField.IsValid() {
		return fmt.Errorf("%s field `%s` not found", refVal.Type(), field)
	}
	rv := reflect.ValueOf(value)
	fieldKind := refField.Kind()
	if fieldKind != reflect.Slice && fieldKind != reflect.Array && fieldKind != reflect.Map && fieldKind == rv.Kind() {
		refField.Set(rv)
		return
	}
	switch fieldKind {
	case reflect.Struct:
		if rv.Kind() != reflect.Map {
			return ErrValueAssociated
		}
		keys := rv.MapKeys()
		subVal := reflect.New(refField.Type())
		for _, key := range keys {
			pv := rv.MapIndex(key)
			if key.Kind() == reflect.String {
				if err = Set(subVal.Interface(), key.String(), pv.Interface()); err != nil {
					return err
				}
			}
		}
		refField.Set(subVal.Elem())
	case reflect.Ptr:
		elemType := refField.Type()
		if elemType.Elem().Kind() != reflect.Struct {
			return ErrValueAssociated
		} else {
			if rv.Kind() != reflect.Map {
				return ErrValueAssociated
			}
			keys := rv.MapKeys()
			subVal := reflect.New(elemType.Elem())
			for _, key := range keys {
				pv := rv.MapIndex(key)
				if key.Kind() == reflect.String {
					if err = Set(subVal.Interface(), key.String(), pv.Interface()); err != nil {
						return err
					}
				}
			}
			refField.Set(subVal)
		}
	case reflect.Map:
		if rv.Kind() != reflect.Map {
			return ErrValueAssociated
		}
		targetValue := reflect.MakeMap(refField.Type())
		keys := rv.MapKeys()
		for _, key := range keys {
			pv := rv.MapIndex(key)
			kVal := reflect.New(refField.Type().Key())
			eVal := reflect.New(refField.Type().Elem())
			if err = safeAssignment(kVal.Elem(), key.Interface()); err != nil {
				return ErrValueAssociated
			}
			if refField.Type().Elem().Kind() == reflect.Struct {
				if pv.Elem().Kind() != reflect.Map {
					return ErrValueAssociated
				}
				subKeys := pv.Elem().MapKeys()
				for _, subKey := range subKeys {
					subVal := pv.Elem().MapIndex(subKey)
					if subKey.Kind() == reflect.String {
						if err = Set(eVal.Interface(), subKey.String(), subVal.Interface()); err != nil {
							return err
						}
					}
				}
				targetValue.SetMapIndex(kVal.Elem(), eVal.Elem())
			} else {
				if err = safeAssignment(eVal.Elem(), pv.Interface()); err != nil {
					return ErrValueAssociated
				}
				targetValue.SetMapIndex(kVal.Elem(), eVal.Elem())
			}
		}
		refField.Set(targetValue)
	case reflect.Array, reflect.Slice:
		n = 0
		innerType := refField.Type().Elem()
		if rv.Kind() == reflect.Array || rv.Kind() == reflect.Slice {
			if innerType.Kind() == reflect.Struct {
				sliceVar := reflect.MakeSlice(refField.Type(), rv.Len(), rv.Len())
				for i := 0; i < rv.Len(); i++ {
					srcVal := rv.Index(i)
					if srcVal.Kind() != reflect.Map {
						return ErrValueAssociated
					}
					dstVal := reflect.New(innerType)
					keys := srcVal.MapKeys()
					for _, key := range keys {
						kv := srcVal.MapIndex(key)
						if key.Kind() == reflect.String {
							if err = Set(dstVal.Interface(), key.String(), kv.Interface()); err != nil {
								return
							}
						}
					}
					sliceVar.Index(n).Set(dstVal.Elem())
					n++
				}
				refField.Set(sliceVar.Slice(0, n))
			} else if innerType.Kind() == reflect.Ptr {
				sliceVar := reflect.MakeSlice(refField.Type(), rv.Len(), rv.Len())
				for i := 0; i < rv.Len(); i++ {
					srcVal := rv.Index(i)
					if srcVal.Kind() != reflect.Map {
						return ErrValueAssociated
					}
					dstVal := reflect.New(innerType.Elem())
					keys := srcVal.MapKeys()
					for _, key := range keys {
						kv := srcVal.MapIndex(key)
						if key.Kind() == reflect.String {
							if err = Set(dstVal.Interface(), key.String(), kv.Interface()); err != nil {
								return
							}
						}
					}
					sliceVar.Index(n).Set(dstVal)
					n++
				}
				refField.Set(sliceVar.Slice(0, n))
			} else {
				sliceVar := reflect.MakeSlice(refField.Type(), rv.Len(), rv.Len())
				for i := 0; i < rv.Len(); i++ {
					srcVal := rv.Index(i)
					dstVal := reflect.New(innerType).Elem()
					if err = safeAssignment(dstVal, srcVal.Interface()); err != nil {
						return
					}
					sliceVar.Index(n).Set(dstVal)
					n++
				}
				refField.Set(sliceVar.Slice(0, n))
			}
		}
	default:
		err = safeAssignment(refField, value)
	}
	return
}