package service

import (
	"context"
	"fmt"
	"io"

	"github.com/topfans/backend/services/aiChatService/model"
)

// DifyStreamReaderAdapter 适配 DifyStreamReader → StreamReader 接口
// DifyStreamReader.Next() returns (content, done, convID)
// StreamReader.Next()   returns (content, done, error)
type DifyStreamReaderAdapter struct {
	reader *DifyStreamReader
}

func (a *DifyStreamReaderAdapter) Next() (string, bool, error) {
	content, done, _ := a.reader.Next()
	return content, done, nil
}

func (a *DifyStreamReaderAdapter) Close() error {
	return a.reader.Close()
}

// DifyAdapter Dify 适配器：适配 DifyClient → StreamReader 接口
// 将 BuildPrompt 输出的 []model.Message 转换为 Dify StreamRequest
type DifyAdapter struct {
	difyClient     *DifyClient
	conversationID string
}

// NewDifyAdapter 创建 Dify 适配器
func NewDifyAdapter(difyClient *DifyClient) *DifyAdapter {
	return &DifyAdapter{
		difyClient: difyClient,
	}
}

// StreamChat 将 []model.Message 转换为 Dify 流式调用
// messages 的最后一条必须是 user 消息（当前输入）
// Dify Workflow 端点不维护多轮上下文，需要通过 inputs.query 传入完整对话文本
func (s *DifyAdapter) StreamChat(ctx context.Context, messages []model.Message) (StreamReader, error) {
	if len(messages) == 0 {
		return nil, fmt.Errorf("empty messages")
	}

	// 取最后一条作为当前 query
	lastMsg := messages[len(messages)-1]
	if lastMsg.Role != "user" {
		return nil, fmt.Errorf("last message must be user role")
	}

	req := StreamRequest{
		Query:          lastMsg.Content,
		ConversationID: s.conversationID,
	}

	reader, err := s.difyClient.StreamChat(ctx, req)
	if err != nil {
		return nil, err
	}

	return &DifyStreamReaderAdapter{reader: reader}, nil
}

// 确保接口实现正确
var _ StreamReader = (*DifyStreamReaderAdapter)(nil)
var _ io.Closer = (*DifyStreamReaderAdapter)(nil)