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()
    ymd := fmt.Sprintf("%d%02d%d", date.Year(), int(date.Month()), 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:           "1250000000",
        SecretId:        os.Getenv("SECRETID"),  // The user's SecretId. It is recommended to use sub-account keys and follow the principle of least privilege for authorization to reduce usage risks. For obtaining sub-account keys, refer to https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        SecretKey:       os.Getenv("SECRETKEY"), // The user's SecretKey. It is recommended to use sub-account keys and follow the principle of least privilege for authorization to reduce usage risks. For obtaining sub-account keys, refer to https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        Proxy:           os.Getenv("Proxy"),
        DurationSeconds: 1800,
        Bucket:          "test-1250000000",
        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)

        // Convert the field names to camelCase
        key := toLowerCamel(field.Name)

        // Process nested structs
        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 {
            // Process basic types
            result[key] = fieldValue.Interface()
        }
    }

    return result
}

// Convert to camelCase format (first letter lowercase)
func toLowerCamel(s string) string {
    if s == "" {
        return s
    }

    // Process all-uppercase words (e.g., ID)
    if strings.ToUpper(s) == s {
        return strings.ToLower(s)
    }

    // Regular camelCase conversion
    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(
        // Obtain keys through environment variables. The os.Getenv method retrieves environment variables.
        config.SecretId,  //os.Getenv("SECRETID"),  // The user's SecretId. It is recommended to use sub-account keys and follow the principle of least privilege for authorization to reduce usage risks. For obtaining sub-account keys, refer to https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        config.SecretKey, //os.Getenv("SECRETKEY"),                 // The user's SecretKey. It is recommended to use sub-account keys and follow the principle of least privilege for authorization to reduce usage risks. For obtaining sub-account keys, refer to https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1
        nil,
        // sts.Host("sts.internal.tencentcloudapi.com"), // Set the domain name. The default domain name is sts.tencentcloudapi.com
        // sts.Scheme("http"),      // Set the protocol. The default is https. Obtaining temporary sts keys on the public cloud does not allow http. Set http only for special scenarios.
    )

    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("Illegal file. Upload is prohibited.")
        }
    }

    if permission.LimitContentType {
        condition["string_like_if_exist"] = map[string]interface{}{
            // Only uploads with a content-type of image are allowed.
            "cos:content-type": "image/*",
        }
    }

    // 3. Limit the upload file size
    if permission.LimitContentLength {
        condition["numeric_less_than_equal"] = map[string]interface{}{
            // The upload size limit cannot exceed 5 MB (applicable only to simple uploads).
            "cos:content-length": 5 * 1024 * 1024,
        }
    }

    key := generateCosKey(ext)
    // Policy Overview 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{
                {
                    // List of key permissions. Simple uploads and multipart uploads require the following permissions. For other permission lists, see https://www.tencentcloud.com/document/product/436/31923?from_cn_redirect=1
                    Action: config.AllowActions,
                    Effect: "allow",
                    Resource: []string{
                        // Change this to the allowed path prefix. You can determine the specific upload path based on your website's user login status. Examples: a.jpg, a/*, or * (Using the wildcard * poses significant security risks. Evaluate its use carefully.)
                        // The bucket naming format is BucketName-APPID. The bucket entered here must follow this format.
                        "qcs::cos:ap-guangzhou:uid/" + config.appId + ":" + config.Bucket + "/" + key,
                    },
                    // Start building the condition
                    // For detailed configuration rules of conditions and the condition types supported by COS, refer to https://www.tencentcloud.com/document/product/436/71306?from_cn_redirect=1
                    Condition: condition,
                },
            },
        },
    }

    // case 1: Request a Temporary Key
    res, err := c.GetCredential(opt)
    if err != nil {
        return nil, err
    }
    // Convert to a camelCase 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("Failed to request temporary key: %v\\n", err)
        return // Exit based on the context
    }

    // Type-assert credentials as map[string]interface{}
    credentials, ok := result["credentials"].(map[string]interface{})
    if !ok {
        fmt.Println("Invalid credential format")
        return
    }
    // Obtain fields with type checking
    tak, tok := credentials["tmpSecretID"].(string)
    tsk, tskok := credentials["tmpSecretKey"].(string)
    token, tokenok := credentials["sessionToken"].(string)
    if !tok || !tskok || !tokenok {
        fmt.Println("Temporary credential field is missing or has an incorrect type")
        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{},
    }
	// The token must be placed in the header when making a request.
    opt.Header.Add("x-cos-security-token", token)
    signature := c.Object.GetSignature(ctx, http.MethodPut, name, tak, tsk, time.Hour, opt, true)
    data := make(map[string]string)

    // Add token and sign
    data["securityToken"] = token
    data["authorization"] = signature
    data["cosHost"] = host
    data["cosKey"] = name
    // Convert to JSON
    jsonData, err := json.MarshalIndent(data, "", "  ")
    if err != nil {
        fmt.Println("JSON encoding failed:", err)
        return
    }
    fmt.Println(string(jsonData))
}