package main

import (
    "context"
    "encoding/json"
    "errors"
    "fmt"
    "github.com/tencentyun/cos-go-sdk-v5"
    sts "github.com/tencentyun/qcloud-cos-sts-sdk/go"
    "math/rand"
    "net/http"
    "net/url"
    "os"
    "reflect"
    "strings"
    "time"
    "unicode"
)

type Config struct {
    filename        string
    appId           string
    SecretId        string
    SecretKey       string
    Proxy           string
    DurationSeconds int
    Bucket          string
    Region          string
    AllowActions    []string
}

type Permission struct {
    LimitExt           bool     `json:"limitExt"`
    ExtWhiteList       []string `json:"extWhiteList"`
    LimitContentType   bool     `json:"limitContentType"`
    LimitContentLength bool     `json:"limitContentLength"`
}

func generateCosKey(ext string) string {
    date := time.Now()
    m := int(date.Month()) + 1
    ymd := fmt.Sprintf("%d%02d%d", date.Year(), m, date.Day())
    r := fmt.Sprintf("%06d", rand.Intn(1000000))
    cosKey := fmt.Sprintf("file/%s/%s_%s.%s", ymd, ymd, r, ext)
    return cosKey
}

func getPermission() Permission {
    permission := Permission{
        LimitExt:           true,
        ExtWhiteList:       []string{"jpg", "jpeg", "png", "gif", "bmp"},
        LimitContentType:   false,
        LimitContentLength: false,
    }
    return permission
}

func getConfig() Config {
    config := Config{
        filename:        "test.jpg",
        appId:           "12500000000",
        SecretId:        os.Getenv("SECRETID"),  // 用户的 SecretId，建议使用子账号密钥，授权遵循最小权限指引，降低使用风险。子账号密钥获取可参考https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        SecretKey:       os.Getenv("SECRETKEY"), // 用户的 SecretKey，建议使用子账号密钥，授权遵循最小权限指引，降低使用风险。子账号密钥获取可参考https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        Proxy:           os.Getenv("Proxy"),
        DurationSeconds: 1800,
        Bucket:          "0-1253960454",
        Region:          "ap-guangzhou",
        AllowActions: []string{
            "name/cos:PutObject",
        },
    }
    return config
}

func stringInSlice(str string, list []string) bool {
    for _, v := range list {
        if v == str {
            return true
        }
    }
    return false
}

func StructToCamelMap(input interface{}) map[string]interface{} {
    v := reflect.ValueOf(input)
    if v.Kind() == reflect.Ptr {
        v = v.Elem()
    }

    result := make(map[string]interface{})
    typ := v.Type()

    for i := 0; i < v.NumField(); i++ {
        field := typ.Field(i)
        fieldValue := v.Field(i)

        // 转换字段名为小驼峰
        key := toLowerCamel(field.Name)

        // 处理嵌套结构体
        if fieldValue.Kind() == reflect.Struct ||
            (fieldValue.Kind() == reflect.Ptr && fieldValue.Elem().Kind() == reflect.Struct) {

            if fieldValue.IsNil() && fieldValue.Kind() == reflect.Ptr {
                result[key] = nil
                continue
            }

            result[key] = StructToCamelMap(fieldValue.Interface())
        } else {
            // 处理基本类型
            result[key] = fieldValue.Interface()
        }
    }

    return result
}

// 转换为小驼峰格式（首字母小写）
func toLowerCamel(s string) string {
    if s == "" {
        return s
    }

    // 处理全大写单词（如 ID）
    if strings.ToUpper(s) == s {
        return strings.ToLower(s)
    }

    // 普通小驼峰转换
    runes := []rune(s)
    runes[0] = unicode.ToLower(runes[0])
    return string(runes)
}

func getStsCredential() (map[string]interface{}, error) {
    config := getConfig()

    permission := getPermission()

    c := sts.NewClient(
        // 通过环境变量获取密钥, os.Getenv 方法表示获取环境变量
        config.SecretId,  //os.Getenv("SECRETID"),  // 用户的 SecretId，建议使用子账号密钥，授权遵循最小权限指引，降低使用风险。子账号密钥获取可参考https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        config.SecretKey, //os.Getenv("SECRETKEY"),                 // 用户的 SecretKey，建议使用子账号密钥，授权遵循最小权限指引，降低使用风险。子账号密钥获取可参考https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        nil,
        // sts.Host("sts.internal.tencentcloudapi.com"), // 设置域名, 默认域名sts.tencentcloudapi.com
        // sts.Scheme("http"),      // 设置协议, 默认为https，公有云sts获取临时密钥不允许走http，特殊场景才需要设置http
    )

    condition := make(map[string]map[string]interface{})

    segments := strings.Split(config.filename, ".")
    if len(segments) == 0 {
        //ext := ""
    }
    ext := segments[len(segments)-1]

    if permission.LimitExt {
        extInvalid := ext == "" || !stringInSlice(ext, permission.ExtWhiteList)
        if extInvalid {
            return nil, errors.New("非法文件，禁止上传")
        }
    }

    if permission.LimitContentType {
        condition["string_like_if_exist"] = map[string]interface{}{
            // 只允许上传 content-type 为图片类型
            "cos:content-type": "image/*",
        }
    }

    // 3. 限制上传文件大小
    if permission.LimitContentLength {
        condition["numeric_less_than_equal"] = map[string]interface{}{
            // 上传大小限制不能超过 5MB(只对简单上传生效)
            "cos:content-length": 5 * 1024 * 1024,
        }
    }

    key := generateCosKey(ext)
    // 策略概述 https://www.tencentcloud.com/document/product/436/18023?from_cn_redirect=1
    opt := &sts.CredentialOptions{
        DurationSeconds: int64(config.DurationSeconds),
        Region:          config.Region,
        Policy: &sts.CredentialPolicy{
            Version: "2.0",
            Statement: []sts.CredentialPolicyStatement{
                {
                    // 密钥的权限列表。简单上传和分片需要以下的权限，其他权限列表请看 https://www.tencentcloud.com/document/product/436/31923?from_cn_redirect=1
                    Action: config.AllowActions,
                    Effect: "allow",
                    Resource: []string{
                        // 这里改成允许的路径前缀，可以根据自己网站的用户登录态判断允许上传的具体路径，例子： a.jpg 或者 a/* 或者 * (使用通配符*存在重大安全风险, 请谨慎评估使用)
                        // 存储桶的命名格式为 BucketName-APPID，此处填写的 bucket 必须为此格式
                        "qcs::cos:ap-guangzhou:uid/" + config.appId + ":" + config.Bucket + "/" + key,
                    },
                    // 开始构建生效条件 condition
                    // 关于 condition 的详细设置规则和COS支持的condition类型可以参考https://www.tencentcloud.com/document/product/436/71306?from_cn_redirect=1
                    Condition: condition,
                },
            },
        },
    }

    // case 1 请求临时密钥
    res, err := c.GetCredential(opt)
    if err != nil {
        return nil, err
    }
    // 转换为小驼峰 map
    resultMap := StructToCamelMap(res)
    resultMap["bucket"] = config.Bucket
    resultMap["region"] = config.Region
    resultMap["key"] = key

    return resultMap, nil
}

func main() {
    result, err := getStsCredential()
    if err != nil {
        fmt.Printf("请求临时密钥失败: %v\\n", err)
        return // 根据上下文决定是否退出
    }

    // 类型断言 credentials 为 map[string]interface{}
    credentials, ok := result["credentials"].(map[string]interface{})
    if !ok {
        fmt.Println("凭证格式错误")
        return
    }
    // 带类型检查的字段获取
    tak, tok := credentials["tmpSecretID"].(string)
    tsk, tskok := credentials["tmpSecretKey"].(string)
    token, tokenok := credentials["sessionToken"].(string)
    if !tok || !tskok || !tokenok {
        fmt.Println("临时凭证字段缺失或类型错误")
        return
    }
    host := "https://" + result["bucket"].(string) + ".cos." + result["region"].(string) + ".myqcloud.com"
    u, _ := url.Parse(host)
    b := &cos.BaseURL{BucketURL: u}
    c := cos.NewClient(b, &http.Client{})
    name := result["key"].(string)
    ctx := context.Background()
    opt := &cos.PresignedURLOptions{
        Query:  &url.Values{},
        Header: &http.Header{},
    }
    opt.Query.Add("x-cos-security-token", token)
    signature := c.Object.GetSignature(ctx, http.MethodPut, name, "tak", "tsk", time.Hour, opt, true)
    fmt.Printf("%s\\n%s\\n%s\\n%s\\n", tak, tsk, token, signature)
    data := make(map[string]string)

    // 添加token和sign
    data["securityToken"] = token
    data["authorization"] = signature
    data["cosHost"] = host
    data["cosKey"] = name
    // 转换为JSON
    jsonData, err := json.MarshalIndent(data, "", "  ")
    if err != nil {
        fmt.Println("JSON编码失败:", err)
        return
    }
    fmt.Println(string(jsonData))
}