// Copyright 2026 Alibaba Group
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package app

import (
	"strings"

	apperrors "github.com/DingTalk-Real-AI/dingtalk-workspace-cli/internal/errors"
)

type serverFailureClass struct {
	message   string
	reason    string
	origin    string
	stage     string
	hint      string
	actions   []string
	operation string
	retryable *bool
}

func classifyServerFailure(message, serverKey, tool string, diag apperrors.ServerDiagnostics) (serverFailureClass, bool) {
	code := strings.ToUpper(strings.TrimSpace(diag.ServerErrorCode))
	detail := strings.ToLower(strings.TrimSpace(diag.TechnicalDetail))
	text := strings.ToLower(strings.TrimSpace(message))
	combined := text + " " + detail

	if code == "999" &&
		(strings.Contains(combined, "nullpointerexception") || strings.Contains(combined, "system error")) {
		classified := serverFailureClass{
			message: message,
			reason:  "upstream_internal_error",
			origin:  "dingtalk_api",
			stage:   "upstream_execution",
			hint:    "上游服务发生内部异常；请保留 Trace ID 和 Server Code，确认操作结果后再决定是否重试。",
			actions: []string{
				"检查目标资源的当前状态，确认本次操作是否已经生效",
				"状态未确认前不要直接重试写操作",
				"持续失败时携带 Trace ID 和 Server Code 联系服务端排查",
			},
		}
		if strings.EqualFold(strings.TrimSpace(serverKey), "todo") &&
			strings.EqualFold(strings.TrimSpace(tool), "create_personal_todo") {
			retryable := false
			classified.operation = "todo/create_personal_todo"
			classified.retryable = &retryable
			classified.hint = "待办服务发生内部异常，创建结果未知；请先查询是否已创建相同待办，再决定是否重试。"
			classified.actions = []string{
				"查询近期由自己创建的待办，核对标题、执行人和截止时间",
				"确认没有创建成功后再重新提交",
				"持续失败时携带 Trace ID 和 Server Code 联系服务端排查",
			}
		}
		return classified, true
	}

	if code == "NETWORK_ERROR" ||
		strings.Contains(detail, "statuscode.unavailable") ||
		strings.Contains(detail, "connection refused") {
		classified := serverFailureClass{
			message: "MCP 后端依赖暂时不可用",
			reason:  "backend_dependency_unavailable",
			origin:  "mcp_gateway",
			stage:   "backend_dependency",
			hint:    "请求参数无需修改；请使用相同参数稍后重试。持续失败时请提供 Trace ID 排查 MCP 服务。",
			actions: []string{
				"使用相同参数重试一次",
				"持续失败时保留 Trace ID 并排查 MCP 后端依赖",
			},
		}
		if strings.Contains(detail, "querytoolmeta") {
			classified.message = "MCP 后端元数据服务暂时不可用"
			classified.stage = "tool_metadata_lookup"
		}
		return classified, true
	}

	if code == "PARAM_ERROR" ||
		strings.Contains(text, "opencid or cid is required") ||
		strings.Contains(text, "openconversationid") && strings.Contains(text, "required") {
		return serverFailureClass{
			message: message,
			reason:  "invalid_request",
			origin:  "dingtalk_api",
			stage:   "tool_validation",
			hint:    "请求未通过后端参数校验；请核对当前 leaf Help/Schema 和稳定 ID 类型后重试。",
		}, true
	}

	return serverFailureClass{}, false
}

func newServerFailureAPIError(
	message string,
	fallbackReason string,
	fallbackHint string,
	serverKey string,
	tool string,
	diag apperrors.ServerDiagnostics,
) error {
	opts := []apperrors.Option{
		apperrors.WithOperation("tools/call"),
		apperrors.WithReason(fallbackReason),
		apperrors.WithServerKey(serverKey),
		apperrors.WithHint(fallbackHint),
		apperrors.WithActions("运行 dws doctor 检查登录态、网络和本地环境；持续失败时保留 Trace ID 和 Server Code"),
		apperrors.WithServerDiag(diag),
	}
	if classified, ok := classifyServerFailure(message, serverKey, tool, diag); ok {
		message = classified.message
		opts = append(opts,
			apperrors.WithReason(classified.reason),
			apperrors.WithOrigin(classified.origin),
			apperrors.WithFailureStage(classified.stage),
			apperrors.WithHint(classified.hint),
			apperrors.WithActions(classified.actions...),
		)
		if classified.operation != "" {
			opts = append(opts, apperrors.WithOperation(classified.operation))
		}
		if classified.retryable != nil {
			opts = append(opts, apperrors.WithRetryable(*classified.retryable))
		}
	}
	return apperrors.NewAPI(message, opts...)
}

func serverFailureReason(err error, fallback string) string {
	typed, ok := err.(*apperrors.Error)
	if ok && strings.TrimSpace(typed.Reason) != "" {
		return typed.Reason
	}
	return fallback
}