// Package apierr defines the bilingual error response type used across all API modules.
// Error messages follow the desensitisation rules: no "VPN" / "翻墙" / "科学上网" wording.
package apierr

import (
	"encoding/json"
	"net/http"
)

// Error is the canonical API error body: {code, message_zh, message_en}.
type Error struct {
	Code      string `json:"code"`
	MessageZH string `json:"message_zh"`
	MessageEn string `json:"message_en"`
}

func (e *Error) Error() string { return e.Code + ": " + e.MessageEn }

// Standard code-module errors.
var (
	ErrInvalidCode = &Error{
		Code:      "INVALID_CODE",
		MessageZH: "激活码格式无效，请检查后重试",
		MessageEn: "Invalid code format, please verify and try again",
	}
	ErrCodeNotFound = &Error{
		Code:      "CODE_NOT_FOUND",
		MessageZH: "激活码无效或已使用",
		MessageEn: "Code not found or already used",
	}
	ErrCodeRedeemed = &Error{
		Code:      "CODE_REDEEMED",
		MessageZH: "该激活码已被其他账户使用",
		MessageEn: "This code has already been redeemed by another account",
	}
	ErrCodeVoid = &Error{
		Code:      "CODE_VOID",
		MessageZH: "该激活码已失效",
		MessageEn: "This code is no longer valid",
	}
	ErrRateLimited = &Error{
		Code:      "RATE_LIMITED",
		MessageZH: "操作过于频繁，请稍后再试",
		MessageEn: "Too many attempts, please try again later",
	}
	ErrLocked = &Error{
		Code:      "ACCOUNT_LOCKED",
		MessageZH: "账户已临时锁定，请1小时后重试",
		MessageEn: "Account temporarily locked, please retry in 1 hour",
	}
	ErrInternal = &Error{
		Code:      "INTERNAL_ERROR",
		MessageZH: "服务器内部错误，请稍后重试",
		MessageEn: "Internal server error, please try again later",
	}
	ErrBadRequest = &Error{
		Code:      "BAD_REQUEST",
		MessageZH: "请求参数有误",
		MessageEn: "Invalid request parameters",
	}

	// Webhook-specific errors.
	ErrWebhookSignature = &Error{
		Code:      "WEBHOOK_INVALID_SIGNATURE",
		MessageZH: "签名校验失败",
		MessageEn: "Invalid webhook signature",
	}
	ErrWebhookTimestamp = &Error{
		Code:      "WEBHOOK_TIMESTAMP_EXPIRED",
		MessageZH: "请求时间戳超出允许窗口",
		MessageEn: "Webhook timestamp outside allowed window",
	}
	ErrWebhookReplay = &Error{
		Code:      "WEBHOOK_REPLAY",
		MessageZH: "重复请求已忽略",
		MessageEn: "Duplicate webhook request ignored",
	}
)

// WriteJSON writes the given status code and error body as JSON.
func WriteJSON(w http.ResponseWriter, status int, e *Error) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(e)
}