package errors

import (
	"encoding/json"
)

const (
	// maxErrorBodyLength defines the maximum length of an error message to be stored or returned.
	maxErrorBodyLength = 2048
)

type upstreamErrorDetail struct {
	Message string `json:"message"`
	Status  string `json:"status"`
}

type upstreamErrorPayload struct {
	Error upstreamErrorDetail `json:"error"`
}

// ParseUpstreamError attempts to parse a structured error message from an upstream response body
func ParseUpstreamError(body []byte) (message string, status string) {
	if len(body) == 0 {
		return "Upstream returned an empty error body", ""
	}
	// 优先级 1: 尝试解析 OpenAI 兼容接口返回的 `[{"error": {...}}]` 数组格式
	var arrayPayload []upstreamErrorPayload
	if err := json.Unmarshal(body, &arrayPayload); err == nil && len(arrayPayload) > 0 {
		detail := arrayPayload[0].Error
		return truncateString(detail.Message, maxErrorBodyLength), detail.Status
	}
	// 优先级 2: 尝试解析 Gemini 原生接口可能返回的 `{"error": {...}}` 单个对象格式
	var singlePayload upstreamErrorPayload
	if err := json.Unmarshal(body, &singlePayload); err == nil && singlePayload.Error.Message != "" {
		detail := singlePayload.Error
		return truncateString(detail.Message, maxErrorBodyLength), detail.Status
	}
	// 最终回退: 对于无法识别的 JSON 或纯文本错误
	return truncateString(string(body), maxErrorBodyLength), ""
}

// truncateString remains unchanged.
func truncateString(s string, maxLength int) string {
	if len(s) > maxLength {
		return s[:maxLength]
	}
	return s
}