package flyto

import (
	"errors"
	"fmt"
	"strings"
)

// errors.go - 结构化错误类型.
//
// 消费者可通过 errors.As 提取 *EngineError 获取错误码和恢复建议,
// 无需解析错误字符串.

// ErrorCode 是引擎错误码枚举.
type ErrorCode string

const (
	ErrAPIAuth          ErrorCode = "api_auth_error"
	ErrAPIRateLimit     ErrorCode = "api_rate_limit"
	ErrAPIOverloaded    ErrorCode = "api_overloaded"
	ErrAPIBadRequest    ErrorCode = "api_bad_request"
	ErrToolNotFound     ErrorCode = "tool_not_found"
	ErrToolExecution    ErrorCode = "tool_execution_error"
	ErrPermissionDenied ErrorCode = "permission_denied"
	ErrContextOverflow  ErrorCode = "context_overflow"
	ErrBudgetExceeded   ErrorCode = "budget_exceeded"
	ErrMaxTurns         ErrorCode = "max_turns_reached"
	ErrSessionNotFound  ErrorCode = "session_not_found"
	ErrSessionClosed    ErrorCode = "session_closed"
	ErrMCPConnection    ErrorCode = "mcp_connection_error"
	ErrPluginLoad       ErrorCode = "plugin_load_error"
	ErrInternal         ErrorCode = "internal_error"
	ErrStreamTruncated  ErrorCode = "stream_truncated"
)

// EngineError 是引擎统一错误类型.
type EngineError struct {
	Code       ErrorCode
	Message    string
	Detail     string
	Suggestion string
	Cause      error
	Retryable  bool
}

func (e *EngineError) Error() string {
	if e.Message != "" {
		return e.Message
	}
	return string(e.Code)
}

func (e *EngineError) Unwrap() error { return e.Cause }

var defaultSuggestions = map[ErrorCode]string{
	ErrAPIAuth:          "请检查 API Key 环境变量是否正确设置",
	ErrAPIRateLimit:     "已达到 API 速率限制，将自动重试",
	ErrAPIOverloaded:    "API 服务暂时过载，将自动重试",
	ErrAPIBadRequest:    "请求格式错误，请检查输入参数",
	ErrToolNotFound:     "请检查工具名称是否正确",
	ErrToolExecution:    "工具执行失败，请检查输入参数和工作目录",
	ErrPermissionDenied: "权限被拒绝，可通过修改权限模式或添加规则来授权",
	ErrContextOverflow:  "对话上下文已满，已自动压缩",
	ErrBudgetExceeded:   "已达到预算上限",
	ErrMaxTurns:         "已达到最大对话轮次限制",
	ErrSessionNotFound:  "指定的会话不存在",
	ErrSessionClosed:    "会话已关闭，请创建新的会话",
	ErrMCPConnection:    "MCP 服务器连接失败，请检查服务器配置",
	ErrPluginLoad:       "插件加载失败，请检查插件配置",
	ErrInternal:         "发生内部错误，请重试",
	ErrStreamTruncated:  "流式响应被中间代理截断，请检查网络代理配置",
}

var defaultRetryable = map[ErrorCode]bool{
	ErrAPIRateLimit:    true,
	ErrAPIOverloaded:   true,
	ErrMCPConnection:   true,
	ErrInternal:        true,
	ErrStreamTruncated: true,
}

// NewEngineError 创建引擎错误(使用默认 Suggestion 和 Retryable).
func NewEngineError(code ErrorCode, message string, cause error) *EngineError {
	return &EngineError{
		Code:       code,
		Message:    message,
		Suggestion: defaultSuggestions[code],
		Cause:      cause,
		Retryable:  defaultRetryable[code],
	}
}

// WrapError 将普通错误包装为 EngineError.
func WrapError(cause error, code ErrorCode, message string) *EngineError {
	if cause == nil {
		return NewEngineError(code, message, nil)
	}
	var existing *EngineError
	if errors.As(cause, &existing) {
		return &EngineError{
			Code:       code,
			Message:    message,
			Detail:     existing.Detail,
			Suggestion: defaultSuggestions[code],
			Cause:      cause,
			Retryable:  defaultRetryable[code],
		}
	}
	return &EngineError{
		Code:       code,
		Message:    message,
		Detail:     cause.Error(),
		Suggestion: defaultSuggestions[code],
		Cause:      cause,
		Retryable:  defaultRetryable[code],
	}
}

// IsRetryable 检查错误是否可重试.
func IsRetryable(err error) bool {
	if err == nil {
		return false
	}
	var e *EngineError
	if errors.As(err, &e) {
		return e.Retryable
	}
	s := err.Error()
	return strings.Contains(s, "HTTP 429") ||
		strings.Contains(s, "HTTP 529") ||
		strings.Contains(s, "connection reset") ||
		strings.Contains(s, "timeout")
}

// FormatErrorForDisplay 格式化错误供用户阅读.
func FormatErrorForDisplay(err error, verbose bool) string {
	var e *EngineError
	if !errors.As(err, &e) {
		return fmt.Sprintf("错误: %s", err.Error())
	}
	var sb strings.Builder
	sb.WriteString(fmt.Sprintf("错误: %s", e.Message))
	if e.Suggestion != "" {
		sb.WriteString(fmt.Sprintf("\n建议: %s", e.Suggestion))
	}
	if verbose && e.Detail != "" {
		sb.WriteString(fmt.Sprintf("\n详情: %s", e.Detail))
	}
	if e.Retryable {
		sb.WriteString("\n(此错误可自动重试)")
	}
	return sb.String()
}