package errors

import (
	"fmt"
	"net/http"
	"sync"
)

//根据 code 默认展示信息的接口
var (
	unknownCoder defaultCoder = defaultCoder{1, http.StatusInternalServerError, "An internal server error occurred", "http://github.com/marmotedu/errors/README.md"}
)

// 定义错误代码详细信息定义接口
// 因为最终返回的内容为   定义接口
//举例:
/*
Identifer(状态码对应const) |   Code    | HTTP Code |     Description
  ErrSucess（内部使用）       100001        200             OK  (外部展示)
  ErrSecretNotFound         110102        404           Secret not found
地址:
https://static001.geekbang.org/resource/image/b5/95/b58ff5b9455d13fc397fdf5228ea7195.png?wh=1441x1518
*/

//定义 Code 接口
type Coder interface {
	// 对应HTTP的状态码
	HTTPStatus() int
	// err对应的状态码
	Code() int
	// code对应的错误描述(面向用户)
	String() string
	// 详情文档
	Reference() string
}

type defaultCoder struct {
	HTTPCode   int
	C          int //字段名和方法名不能相同
	CodeString string
	Ref        string
}

// 实现 Coder 接口
func (d defaultCoder) HTTPStatus() int {
	if d.HTTPCode == 0 {
		return 500
	}
	return d.HTTPCode
}

func (d defaultCoder) Code() int {
	return d.C
}

func (d defaultCoder) String() string    { return d.CodeString }
func (d defaultCoder) Reference() string { return d.Ref }

// 定义Coder集合
var coders = map[int]Coder{}
var rw sync.RWMutex

//然后进行注册
func Register(c Coder) {
	if c.Code() == 0 { //验证 code 是否存在
		panic("code `0` is reserved by `github.com/marmotedu/errors` as unknownCode error code")
	}
	rw.Lock()
	defer rw.Unlock()
	coders[c.Code()] = c
}

func MustRegister(c Coder) {
	//先进行判断是否含有 若有则进行panic
	if c.Code() == 0 { //验证 code 是否存在
		panic("code `0` is reserved by `github.com/marmotedu/errors` as unknownCode error code")
	}
	rw.Lock()
	defer rw.Unlock()
	if _, ok := coders[c.Code()]; ok {
		panic(fmt.Sprintf("code: %d already exist", c.Code()))
	}
	coders[c.Code()] = c
}

//得到 err 对应的 Coder接口
func ParseCoder(err error) Coder {
	if err == nil {
		return nil
	}

	if v, ok := err.(*withCode); ok {
		if coder, ok := coders[v.code]; ok {
			return coder
		}
	}

	return unknownCoder
}

//判断withCode是否存在
func IsCode(err error, code int) bool {
	if v, ok := err.(*withCode); ok {
		if v.code == code {
			return true
		}
		if v.cause != nil {
			return IsCode(v.cause, code)
		}
		return false
	}
	return false
}

func init() {
	//初始化默认的code
	coders[unknownCoder.Code()] = unknownCoder
}