// Copyright 2017 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

// Package gconv implements powerful and easy-to-use converting functionality for any types of variables.
package gconv

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strconv"
	"strings"
	"time"
)

// Type assert api for String().
type apiString interface {
	String() string
}

// Type assert api for Error().
type apiError interface {
	Error() string
}

const (
	gGCONV_TAG = "gconv"
)

var (
	// Empty strings.
	emptyStringMap = map[string]struct{}{
		"":      {},
		"0":     {},
		"no":    {},
		"off":   {},
		"false": {},
	}

	// Priority tags for Map*/Struct* functions.
	structTagPriority = []string{gGCONV_TAG, "c", "json"}
)

// Convert converts the variable <i> to the type <t>, the type <t> is specified by string.
// The optional parameter <params> is used for additional necessary parameter for this conversion.
// It supports common types conversion as its conversion based on type name string.
func Convert(i interface{}, t string, params ...interface{}) interface{} {
	switch t {
	case "int":
		return Int(i)
	case "int8":
		return Int8(i)
	case "int16":
		return Int16(i)
	case "int32":
		return Int32(i)
	case "int64":
		return Int64(i)
	case "uint":
		return Uint(i)
	case "uint8":
		return Uint8(i)
	case "uint16":
		return Uint16(i)
	case "uint32":
		return Uint32(i)
	case "uint64":
		return Uint64(i)
	case "float32":
		return Float32(i)
	case "float64":
		return Float64(i)
	case "bool":
		return Bool(i)
	case "string":
		return String(i)
	case "[]byte":
		return Bytes(i)
	case "[]int":
		return Ints(i)
	case "[]int32":
		return Int32s(i)
	case "[]int64":
		return Int64s(i)
	case "[]uint":
		return Uints(i)
	case "[]uint32":
		return Uint32s(i)
	case "[]uint64":
		return Uint64s(i)
	case "[]float32":
		return Float32s(i)
	case "[]float64":
		return Float64s(i)
	case "[]string":
		return Strings(i)
	default:
		return i
	}
}

// Byte converts <i> to byte.
func Byte(i interface{}) byte {
	if v, ok := i.(byte); ok {
		return v
	}
	return Uint8(i)
}

// Bytes converts <i> to []byte.
func Bytes(i interface{}) []byte {
	if i == nil {
		return nil
	}
	switch value := i.(type) {
	case string:
		return []byte(value)
	case []byte:
		return value
	default:
		return nil
	}
}

// Rune converts <i> to rune.
func Rune(i interface{}) rune {
	if v, ok := i.(rune); ok {
		return v
	}
	return rune(Int32(i))
}

// Runes converts <i> to []rune.
func Runes(i interface{}) []rune {
	if v, ok := i.([]rune); ok {
		return v
	}
	return []rune(String(i))
}

// String converts <i> to string.
// It's most common used converting function.
func String(i interface{}) string {
	if i == nil {
		return ""
	}
	switch value := i.(type) {
	case int:
		return strconv.Itoa(value)
	case int8:
		return strconv.Itoa(int(value))
	case int16:
		return strconv.Itoa(int(value))
	case int32:
		return strconv.Itoa(int(value))
	case int64:
		return strconv.FormatInt(value, 10)
	case uint:
		return strconv.FormatUint(uint64(value), 10)
	case uint8:
		return strconv.FormatUint(uint64(value), 10)
	case uint16:
		return strconv.FormatUint(uint64(value), 10)
	case uint32:
		return strconv.FormatUint(uint64(value), 10)
	case uint64:
		return strconv.FormatUint(value, 10)
	case float32:
		return strconv.FormatFloat(float64(value), 'f', -1, 32)
	case float64:
		return strconv.FormatFloat(value, 'f', -1, 64)
	case bool:
		return strconv.FormatBool(value)
	case string:
		return value
	case []byte:
		return string(value)
	case time.Time:
		if value.IsZero() {
			return ""
		}
		return value.String()
	case *time.Time:
		if value == nil {
			return ""
		}
		return value.String()
	default:
		// Empty checks.
		if value == nil {
			return ""
		}
		if f, ok := value.(apiString); ok {
			// If the variable implements the String() interface,
			// then use that interface to perform the conversion
			return f.String()
		} else if f, ok := value.(apiError); ok {
			// If the variable implements the Error() interface,
			// then use that interface to perform the conversion
			return f.Error()
		} else {
			// Reflect checks.
			rv := reflect.ValueOf(value)
			kind := rv.Kind()
			switch kind {
			case reflect.Chan,
				reflect.Map,
				reflect.Slice,
				reflect.Func,
				reflect.Ptr,
				reflect.Interface,
				reflect.UnsafePointer:
				if rv.IsNil() {
					return ""
				}
			}
			if kind == reflect.Ptr {
				return String(rv.Elem().Interface())
			}
			// Finally we use json.Marshal to convert.
			if jsonContent, err := json.Marshal(value); err != nil {
				return fmt.Sprint(value)
			} else {
				return string(jsonContent)
			}
		}
	}
}

// Bool converts <i> to bool.
// It returns false if <i> is: false, "", 0, "false", "off", "no", empty slice/map.
func Bool(i interface{}) bool {
	if i == nil {
		return false
	}
	switch value := i.(type) {
	case bool:
		return value
	case []byte:
		if _, ok := emptyStringMap[strings.ToLower(string(value))]; ok {
			return false
		}
		return true
	case string:
		if _, ok := emptyStringMap[strings.ToLower(value)]; ok {
			return false
		}
		return true
	default:
		rv := reflect.ValueOf(i)
		switch rv.Kind() {
		case reflect.Ptr:
			return !rv.IsNil()
		case reflect.Map:
			fallthrough
		case reflect.Array:
			fallthrough
		case reflect.Slice:
			return rv.Len() != 0
		case reflect.Struct:
			return true
		default:
			s := strings.ToLower(String(i))
			if _, ok := emptyStringMap[s]; ok {
				return false
			}
			return true
		}
	}
}

// Int converts <i> to int.
func Int(i interface{}) int {
	if i == nil {
		return 0
	}
	if v, ok := i.(int); ok {
		return v
	}
	return int(Int64(i))
}

// Int8 converts <i> to int8.
func Int8(i interface{}) int8 {
	if i == nil {
		return 0
	}
	if v, ok := i.(int8); ok {
		return v
	}
	return int8(Int64(i))
}

// Int16 converts <i> to int16.
func Int16(i interface{}) int16 {
	if i == nil {
		return 0
	}
	if v, ok := i.(int16); ok {
		return v
	}
	return int16(Int64(i))
}

// Int32 converts <i> to int32.
func Int32(i interface{}) int32 {
	if i == nil {
		return 0
	}
	if v, ok := i.(int32); ok {
		return v
	}
	return int32(Int64(i))
}

// Int64 converts <i> to int64.
func Int64(i interface{}) int64 {
	if i == nil {
		return 0
	}
	switch value := i.(type) {
	case int:
		return int64(value)
	case int8:
		return int64(value)
	case int16:
		return int64(value)
	case int32:
		return int64(value)
	case int64:
		return value
	case uint:
		return int64(value)
	case uint8:
		return int64(value)
	case uint16:
		return int64(value)
	case uint32:
		return int64(value)
	case uint64:
		return int64(value)
	case float32:
		return int64(value)
	case float64:
		return int64(value)
	case bool:
		if value {
			return 1
		}
		return 0
	default:
		s := String(value)
		isMinus := false
		if len(s) > 0 {
			if s[0] == '-' {
				isMinus = true
				s = s[1:]
			} else if s[0] == '+' {
				s = s[1:]
			}
		}
		// Hexadecimal
		if len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X') {
			if v, e := strconv.ParseInt(s[2:], 16, 64); e == nil {
				if isMinus {
					return -v
				}
				return v
			}
		}
		// Octal
		if len(s) > 1 && s[0] == '0' {
			if v, e := strconv.ParseInt(s[1:], 8, 64); e == nil {
				if isMinus {
					return -v
				}
				return v
			}
		}
		// Decimal
		if v, e := strconv.ParseInt(s, 10, 64); e == nil {
			if isMinus {
				return -v
			}
			return v
		}
		// Float64
		return int64(Float64(value))
	}
}

// Uint converts <i> to uint.
func Uint(i interface{}) uint {
	if i == nil {
		return 0
	}
	if v, ok := i.(uint); ok {
		return v
	}
	return uint(Uint64(i))
}

// Uint8 converts <i> to uint8.
func Uint8(i interface{}) uint8 {
	if i == nil {
		return 0
	}
	if v, ok := i.(uint8); ok {
		return v
	}
	return uint8(Uint64(i))
}

// Uint16 converts <i> to uint16.
func Uint16(i interface{}) uint16 {
	if i == nil {
		return 0
	}
	if v, ok := i.(uint16); ok {
		return v
	}
	return uint16(Uint64(i))
}

// Uint32 converts <i> to uint32.
func Uint32(i interface{}) uint32 {
	if i == nil {
		return 0
	}
	if v, ok := i.(uint32); ok {
		return v
	}
	return uint32(Uint64(i))
}

// Uint64 converts <i> to uint64.
func Uint64(i interface{}) uint64 {
	if i == nil {
		return 0
	}
	switch value := i.(type) {
	case int:
		return uint64(value)
	case int8:
		return uint64(value)
	case int16:
		return uint64(value)
	case int32:
		return uint64(value)
	case int64:
		return uint64(value)
	case uint:
		return uint64(value)
	case uint8:
		return uint64(value)
	case uint16:
		return uint64(value)
	case uint32:
		return uint64(value)
	case uint64:
		return value
	case float32:
		return uint64(value)
	case float64:
		return uint64(value)
	case bool:
		if value {
			return 1
		}
		return 0
	default:
		s := String(value)
		// Hexadecimal
		if len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X') {
			if v, e := strconv.ParseUint(s[2:], 16, 64); e == nil {
				return v
			}
		}
		// Octal
		if len(s) > 1 && s[0] == '0' {
			if v, e := strconv.ParseUint(s[1:], 8, 64); e == nil {
				return v
			}
		}
		// Decimal
		if v, e := strconv.ParseUint(s, 10, 64); e == nil {
			return v
		}
		// Float64
		return uint64(Float64(value))
	}
}

// Float32 converts <i> to float32.
func Float32(i interface{}) float32 {
	if i == nil {
		return 0
	}
	switch value := i.(type) {
	case float32:
		return value
	case float64:
		return float32(value)
	default:
		v, _ := strconv.ParseFloat(String(i), 64)
		return float32(v)
	}
}

// Float64 converts <i> to float64.
func Float64(i interface{}) float64 {
	if i == nil {
		return 0
	}
	switch value := i.(type) {
	case float32:
		return float64(value)
	case float64:
		return value
	default:
		v, _ := strconv.ParseFloat(String(i), 64)
		return v
	}
}