package server

import (
	"ai-chat-service/chat-server/data"
	metrics_bus "ai-chat-service/chat-server/metrics-bus"
	"ai-chat-service/pkg/config"
	"ai-chat-service/pkg/log"
	"ai-chat-service/proto"
	"ai-chat-service/services/embedding"
	"ai-chat-service/services/faiss"
	"context"
	"encoding/json"
	"io"
	"strconv"

	"github.com/golang/protobuf/jsonpb"
	"github.com/google/uuid"
	"github.com/sashabaranov/go-openai"
)

const (
	replySourceSemanticMatch = "semantic_match"
	replySourceLLM           = "llm"
)

type chatService struct {
	proto.UnimplementedChatServer
	config     *config.Config
	log        log.ILogger
	data       data.IChatRecordsData
	embedder   embedding.Embedder
	faiss      faiss.Client
	busMetrics *metrics_bus.BusMetrics
}

func NewChatService(data data.IChatRecordsData, embedder embedding.Embedder, faissClient faiss.Client, config *config.Config, log log.ILogger, busMetrics *metrics_bus.BusMetrics) proto.ChatServer {
	return &chatService{
		config:     config,
		log:        log,
		data:       data,
		embedder:   embedder,
		faiss:      faissClient,
		busMetrics: busMetrics,
	}
}

func (s *chatService) ChatCompletion(ctx context.Context, in *proto.ChatCompletionRequest) (*proto.ChatCompletionResponse, error) {
	app := s.newApp(in)

	ok, msg, err := app.sensitive(in)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return nil, err
	}
	if !ok {
		s.busMetrics.SensitiveQuestionsTotalCounter.Inc()
		res := app.buildChatCompletionResponse(msg)
		promptTokens, tokenErr := app.countMessageTokens(openai.ChatMessageRoleUser, in.Message)
		if tokenErr != nil {
			s.log.Error(tokenErr)
			return res, nil
		}
		usage, tokenErr := app.buildUsage(promptTokens, msg)
		if tokenErr != nil {
			s.log.Error(tokenErr)
			return res, nil
		}
		res.Usage = usage
		return res, nil
	}

	keywords := app.keywords(in)
	if len(keywords) > 0 {
		s.busMetrics.KeywordsQuestionsTotalCounter.Inc()
	}

	req, _, currTokens, _, err := app.buildChatCompletionRequest(in, false)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return nil, err
	}

	questionEmbedding, cachedRecord := s.searchCachedAnswer(ctx, in.Message)
	if cachedRecord != nil {
		res := app.buildChatCompletionResponse(cachedRecord.Answer)
		res.Usage = app.buildZeroUsage()
		res.Source = replySourceSemanticMatch
		return res, nil
	}

	client := app.getOpenaiClient()
	resp, err := client.CreateChatCompletion(ctx, req)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		s.log.Error(err)
		return nil, err
	}

	res := &proto.ChatCompletionResponse{}
	bytes, err := json.Marshal(resp)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return nil, err
	}
	if err = jsonpb.UnmarshalString(string(bytes), res); err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return nil, err
	}

	answer := ""
	if len(resp.Choices) > 0 {
		answer = resp.Choices[0].Message.Content
	}
	usage, tokenErr := app.buildUsage(currTokens, answer)
	if tokenErr != nil {
		s.log.Error(tokenErr)
	} else {
		res.Usage = usage
	}
	res.Source = replySourceLLM

	if len(resp.Choices) > 0 {
		if err = s.persistQA(ctx, questionEmbedding, in.Message, answer); err != nil {
			s.log.Error(err)
		} else {
			s.busMetrics.QuestionsTotalCounter.Inc()
		}
	}
	return res, nil
}

func (s *chatService) ChatCompletionStream(in *proto.ChatCompletionRequest, stream proto.Chat_ChatCompletionStreamServer) error {
	app := s.newApp(in)

	ok, msg, err := app.sensitive(in)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return err
	}
	if !ok {
		s.busMetrics.SensitiveQuestionsTotalCounter.Inc()
		resID := uuid.New().String()
		start := app.buildChatCompletionStreamResponse(resID, "", "")
		if err = stream.Send(start); err != nil {
			return err
		}
		for _, res := range app.buildChatCompletionStreamResponseList(resID, msg) {
			if err = stream.Send(res); err != nil {
				return err
			}
		}
		final := app.buildChatCompletionStreamResponse(resID, "", "stop")
		promptTokens, tokenErr := app.countMessageTokens(openai.ChatMessageRoleUser, in.Message)
		if tokenErr != nil {
			s.log.Error(tokenErr)
		} else {
			usage, tokenErr := app.buildUsage(promptTokens, msg)
			if tokenErr != nil {
				s.log.Error(tokenErr)
			} else {
				final.Usage = usage
			}
		}
		return stream.Send(final)
	}

	keywords := app.keywords(in)
	if len(keywords) > 0 {
		s.busMetrics.KeywordsQuestionsTotalCounter.Inc()
	}

	req, _, currTokens, _, err := app.buildChatCompletionRequest(in, true)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return err
	}

	questionEmbedding, cachedRecord := s.searchCachedAnswer(stream.Context(), in.Message)
	if cachedRecord != nil {
		start := app.buildChatCompletionStreamResponse(cachedRecord.ID, "", "")
		start.Source = replySourceSemanticMatch
		if err = stream.Send(start); err != nil {
			return err
		}
		for _, res := range app.buildChatCompletionStreamResponseList(cachedRecord.ID, cachedRecord.Answer) {
			if err = stream.Send(res); err != nil {
				return err
			}
		}
		final := app.buildChatCompletionStreamResponse(cachedRecord.ID, "", "stop")
		final.Source = replySourceSemanticMatch
		final.Usage = app.buildZeroUsage()
		return stream.Send(final)
	}

	client := app.getOpenaiClient()
	chatStream, err := client.CreateChatCompletionStream(stream.Context(), req)
	if err != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		s.log.Error(err)
		return err
	}
	defer chatStream.Close()

	completionContent := ""
	responseID := ""
	for {
		resp, err := chatStream.Recv()
		if err != nil && err != io.EOF {
			s.busMetrics.ErrQuestionsTotalCounter.Inc()
			s.log.Error(err)
			return err
		}
		if err == io.EOF {
			break
		}
		if resp.ID != "" {
			responseID = resp.ID
		}
		completionContent += resp.Choices[0].Delta.Content

		res := &proto.ChatCompletionStreamResponse{}
		bytes, err := json.Marshal(resp)
		if err != nil {
			s.busMetrics.ErrQuestionsTotalCounter.Inc()
			return err
		}
		if err = jsonpb.UnmarshalString(string(bytes), res); err != nil {
			s.busMetrics.ErrQuestionsTotalCounter.Inc()
			return err
		}
		res.Source = replySourceLLM
		if err = stream.Send(res); err != nil {
			return err
		}
	}

	usage, tokenErr := app.buildUsage(currTokens, completionContent)
	if tokenErr != nil {
		s.busMetrics.ErrQuestionsTotalCounter.Inc()
		return tokenErr
	}
	if responseID == "" {
		responseID = uuid.New().String()
	}
	final := app.buildChatCompletionStreamResponse(responseID, "", "stop")
	final.Usage = usage
	final.Source = replySourceLLM
	if err = stream.Send(final); err != nil {
		return err
	}

	if err = s.persistQA(stream.Context(), questionEmbedding, in.Message, completionContent); err != nil {
		s.log.Error(err)
	} else {
		s.busMetrics.QuestionsTotalCounter.Inc()
	}
	return nil
}

func (s *chatService) searchCachedAnswer(ctx context.Context, question string) ([]float32, *data.ChatRecord) {
	embeddingVector, err := s.embedder.Embed(ctx, question)
	if err != nil {
		s.log.Error(err)
		return nil, nil
	}

	searchRes, err := s.faiss.Search(ctx, embeddingVector, s.config.Faiss.SearchK)
	if err != nil {
		s.log.Error(err)
		return embeddingVector, nil
	}
	if searchRes == nil || len(searchRes.IDs) == 0 || len(searchRes.SimilarityScores) == 0 {
		return embeddingVector, nil
	}
	limit := len(searchRes.IDs)
	if len(searchRes.SimilarityScores) < limit {
		limit = len(searchRes.SimilarityScores)
	}
	for i := 0; i < limit; i++ {
		if searchRes.IDs[i] < 0 || searchRes.SimilarityScores[i] < s.config.Faiss.SimilarityThreshold {
			continue
		}
		record, err := s.data.GetById(strconv.FormatInt(searchRes.IDs[i], 10))
		if err != nil {
			s.log.Error(err)
			return embeddingVector, nil
		}
		if record != nil {
			return embeddingVector, record
		}
	}
	return embeddingVector, nil
}

func (s *chatService) persistQA(ctx context.Context, questionEmbedding []float32, question, answer string) error {
	if len(questionEmbedding) == 0 {
		vector, err := s.embedder.Embed(ctx, question)
		if err != nil {
			return err
		}
		questionEmbedding = vector
	}
	id, err := s.faiss.Insert(ctx, questionEmbedding)
	if err != nil {
		return err
	}
	return s.data.Add(&data.ChatRecord{
		ID:       id,
		Question: question,
		Answer:   answer,
	})
}