Golang错误信息本地化与国际化处理

// errors/codes.go
package errors

const (
    ErrUserNotFound    = "USER_NOT_FOUND"
    ErrInvalidInput    = "INVALID_INPUT"
    ErrDatabaseConnect = "DB_CONNECT_FAILED"
    // ... 其他错误码
)

// i18n/locales/en.json
// {
//     "USER_NOT_FOUND": "User with ID '{{.ID}}' not found.",
//     "INVALID_INPUT": "Invalid input: field '{{.Field}}' is required.",
//     "DB_CONNECT_FAILED": "Failed to connect to the database."
// }

// i18n/locales/zh.json
// {
//     "USER_NOT_FOUND": "ID为'{{.ID}}'的用户未找到。",
//     "INVALID_INPUT": "输入无效：字段'{{.Field}}'是必填项。",
//     "DB_CONNECT_FAILED": "数据库连接失败。"
// }

// i18n/i18n.go (一个简化的i18n包)
package i18n

import (
    "bytes"
    "encoding/json"
    "fmt"
    "html/template" // 或 text/template
    "io/ioutil"
    "path/filepath"
    "sync"
)

var (
    translations = make(map[string]map[string]string) // lang -> code -> msg
    mu           sync.RWMutex
    defaultLang  = "en" // 默认语言
)

// LoadTranslations 从指定目录加载所有翻译文件
func LoadTranslations(dir string) error {
    mu.Lock()
    defer mu.Unlock()

    files, err := ioutil.ReadDir(dir)
    if err != nil {
        return fmt.Errorf("failed to read translation directory: %w", err)
    }

    for _, file := range files {
        if file.IsDir() {
            continue
        }
        lang := file.Name()[:len(file.Name())-len(filepath.Ext(file.Name()))] // 从文件名获取语言，如 "en"

        filePath := filepath.Join(dir, file.Name())
        data, err := ioutil.ReadFile(filePath)
        if err != nil {
            return fmt.Errorf("failed to read translation file %s: %w", filePath, err)
        }

        var langMap map[string]string
        if err := json.Unmarshal(data, &langMap); err != nil {
            return fmt.Errorf("failed to unmarshal translation file %s: %w", filePath, err)
        }
        translations[lang] = langMap
    }
    return nil
}

// T 翻译错误码到指定语言的消息，并填充参数
func T(lang, code string, args map[string]interface{}) string {
    mu.RLock()
    defer mu.RUnlock()

    // 尝试获取指定语言的翻译
    langMap, ok := translations[lang]
    if !ok {
        // 如果指定语言不存在，回退到默认语言
        langMap, ok = translations[defaultLang]
        if !ok {
            return fmt.Sprintf("Translation system not initialized or default language '%s' missing.", defaultLang)
        }
    }

    // 尝试获取指定错误码的翻译
    msg, ok := langMap[code]
    if !ok {
        // 如果指定语言中没有该错误码，尝试从默认语言中获取
        msg, ok = translations[defaultLang][code]
        if !ok {
            return fmt.Sprintf("Translation missing for code '%s' in language '%s'.", code, lang)
        }
    }

    // 使用模板填充参数
    if len(args) > 0 {
        tmpl, err := template.New("msg").Parse(msg)
        if err != nil {
            // 模板解析失败，返回原始消息或一个错误提示
            return fmt.Sprintf("Error parsing template for code '%s': %v. Original: %s", code, err, msg)
        }
        var buf bytes.Buffer
        if err := tmpl.Execute(&buf, args); err != nil {
            // 模板执行失败
            return fmt.Sprintf("Error executing template for code '%s': %v. Original: %s", code, err, msg)
        }
        return buf.String()
    }
    return msg
}