//
//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
//
//  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 models

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"ragflow/internal/common"
	"strings"
)

// LongCatModel implements ModelDriver for LongCat (Meituan).
type LongCatModel struct {
	baseModel BaseModel
}

// NewLongCatModel creates a new LongCat model instance.
func NewLongCatModel(baseURL map[string]string, urlSuffix URLSuffix) *LongCatModel {
	return &LongCatModel{
		baseModel: BaseModel{
			BaseURL:    baseURL,
			URLSuffix:  urlSuffix,
			httpClient: NewDriverHTTPClient(),
		},
	}
}

func (l *LongCatModel) NewInstance(baseURL map[string]string) ModelDriver {
	return NewLongCatModel(baseURL, l.baseModel.URLSuffix)
}

func (l *LongCatModel) Name() string {
	return "longcat"
}

// LongCatChatResponse mirrors the OpenAI-compatible response returned by
// LongCat's POST /openai/v1/chat/completions endpoint. Usage is always
// present on a successful response.
type LongCatChatResponse struct {
	ID      string `json:"id"`
	Object  string `json:"object"`
	Created int64  `json:"created"`
	Model   string `json:"model"`
	Choices []struct {
		Index        int    `json:"index"`
		FinishReason string `json:"finish_reason"`
		Message      struct {
			Role             string           `json:"role"`
			Content          string           `json:"content"`
			ReasoningContent string           `json:"reasoning_content"`
			ToolCalls        []map[string]any `json:"tool_calls"`
		} `json:"message"`
	} `json:"choices"`
	Usage struct {
		PromptTokens     int `json:"prompt_tokens"`
		CompletionTokens int `json:"completion_tokens"`
		TotalTokens      int `json:"total_tokens"`
	} `json:"usage"`
}

// ChatWithMessages sends multiple messages with roles and returns the response.
func (l *LongCatModel) ChatWithMessages(ctx context.Context, modelName string, messages []Message, apiConfig *APIConfig, chatModelConfig *ChatConfig, modelUsage *common.ModelUsage) (*ChatResponse, error) {
	if err := l.baseModel.APIConfigCheck(apiConfig); err != nil {
		return nil, err
	}

	if len(messages) == 0 {
		return nil, fmt.Errorf("messages is empty")
	}

	baseURL, err := l.baseModel.GetBaseURL(apiConfig)
	if err != nil {
		return nil, err
	}
	baseURL = strings.TrimSuffix(baseURL, "/")
	url := fmt.Sprintf("%s/%s", baseURL, l.baseModel.URLSuffix.Chat)

	reqBody := buildRequestBody(chatModelConfig, modelName, messages, false)
	delete(reqBody, "stop")

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	ctx, cancel := context.WithTimeout(ctx, nonStreamCallTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := l.baseModel.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	return parseChatCompletionResponse(body, chatModelConfig, modelUsage, func(body []byte, chatConfig *ChatConfig) (chatResponseParts, error) {
		var result LongCatChatResponse
		if err := json.Unmarshal(body, &result); err != nil {
			return chatResponseParts{}, fmt.Errorf("failed to parse response: %w", err)
		}
		if len(result.Choices) == 0 {
			return chatResponseParts{}, fmt.Errorf("no choices in response")
		}

		choice := &result.Choices[0]
		content := choice.Message.Content
		// LongCat-Flash-Thinking may emit all output as reasoning_content
		// with content left null/empty. That is a valid response — only
		// reject when there is neither content, reasoning, nor tool calls.
		if content == "" && choice.Message.ReasoningContent == "" && len(choice.Message.ToolCalls) == 0 {
			return chatResponseParts{}, fmt.Errorf("invalid content format")
		}

		// LongCat 2.0 returns the chain-of-thought in a
		// `reasoning_content` field on the message (OpenAI o-series shape,
		// also used by kimi-k2.6 and DeepSeek-R1). The field is typically
		// prefixed with a leading newline — trim it so callers see clean
		// reasoning. Absent or empty means no reasoning was emitted.
		reasonContent := choice.Message.ReasoningContent
		if reasonContent != "" && reasonContent[0] == '\n' {
			reasonContent = reasonContent[1:]
		}

		usage := &TokenUsage{
			PromptTokens:     result.Usage.PromptTokens,
			CompletionTokens: result.Usage.CompletionTokens,
			TotalTokens:      result.Usage.TotalTokens,
		}

		return chatResponseParts{
			RequestID:     result.ID,
			Content:       &content,
			ReasonContent: &reasonContent,
			ToolCalls:     choice.Message.ToolCalls,
			Usage:         usage,
		}, nil
	})
}

// ChatStreamlyWithSender sends messages and streams the response via the
func (l *LongCatModel) ChatStreamlyWithSender(ctx context.Context, modelName string, messages []Message, apiConfig *APIConfig, chatModelConfig *ChatConfig, modelUsage *common.ModelUsage, sender func(*string, *string) error) error {
	if err := l.baseModel.APIConfigCheck(apiConfig); err != nil {
		return err
	}

	if sender == nil {
		return fmt.Errorf("sender is required")
	}

	if len(messages) == 0 {
		return fmt.Errorf("messages is empty")
	}

	baseURL, err := l.baseModel.GetBaseURL(apiConfig)
	if err != nil {
		return err
	}
	baseURL = strings.TrimSuffix(baseURL, "/")
	url := fmt.Sprintf("%s/%s", baseURL, l.baseModel.URLSuffix.Chat)
	reqBody := buildRequestBody(chatModelConfig, modelName, messages, true)
	delete(reqBody, "stop")
	reqBody["stream_options"] = map[string]any{"include_usage": true}

	if chatModelConfig != nil {
		if chatModelConfig.Stream != nil && !*chatModelConfig.Stream {
			return fmt.Errorf("stream must be true in ChatStreamlyWithSender")
		}
		chatModelConfig.ToolCallsResult = nil
		chatModelConfig.UsageResult = nil
	}

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return fmt.Errorf("failed to marshal request: %w", err)
	}

	// SSE streams are long-lived.
	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := l.baseModel.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	sawTerminal := false
	accumulatedToolCalls := make(map[int]map[string]any)
	done, err := ParseSSEStream[map[string]interface{}](resp.Body, func(event map[string]interface{}) error {
		if apiErr, ok := event["error"]; ok {
			return fmt.Errorf("longcat: upstream stream error: %v", apiErr)
		}

		tokenUsage, found, usageErr := decodeOpenAICompatibleStreamUsage(event)
		if usageErr != nil {
			return usageErr
		}
		if found {
			applyStreamUsage(chatModelConfig, modelUsage, tokenUsage)
		}

		choices, ok := event["choices"].([]interface{})
		if !ok || len(choices) == 0 {
			return nil
		}

		firstChoice, ok := choices[0].(map[string]interface{})
		if !ok {
			return nil
		}

		delta, ok := firstChoice["delta"].(map[string]interface{})
		if !ok {
			return nil
		}

		accumulateToolCallDeltas(delta, accumulatedToolCalls)

		if r, ok := delta["reasoning_content"].(string); ok && r != "" {
			if err := sender(nil, &r); err != nil {
				return err
			}
		}

		content, ok := delta["content"].(string)
		if ok && content != "" {
			if err := sender(&content, nil); err != nil {
				return err
			}
		}

		finishReason, ok := firstChoice["finish_reason"].(string)
		if ok && finishReason != "" {
			sawTerminal = true
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("failed to scan response body: %w", err)
	}
	setSortedToolCallsResult(chatModelConfig, accumulatedToolCalls)
	if !done && !sawTerminal {
		return fmt.Errorf("longcat: stream ended before [DONE] or finish_reason")
	}

	endOfStream := "[DONE]"
	if err := sender(&endOfStream, nil); err != nil {
		return err
	}

	return nil
}

type longCatModelInfo struct {
	ID string `json:"id"`
}

type longCatListModelsResponse struct {
	Data  []ModelListItem `json:"data"`
	Error interface{}     `json:"error"`
}

const longCatMaxListModelsResponseBytes = 1 << 20

func (l *LongCatModel) ListModels(ctx context.Context, apiConfig *APIConfig) ([]ListModelResponse, error) {
	if err := l.baseModel.APIConfigCheck(apiConfig); err != nil {
		return nil, err
	}

	baseURL, err := l.baseModel.GetBaseURL(apiConfig)
	if err != nil {
		return nil, err
	}
	baseURL = strings.TrimSuffix(baseURL, "/")
	url := fmt.Sprintf("%s/%s", baseURL, l.baseModel.URLSuffix.Models)

	ctx, cancel := context.WithTimeout(ctx, nonStreamCallTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := l.baseModel.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(io.LimitReader(resp.Body, longCatMaxListModelsResponseBytes+1))
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}
	if len(body) > longCatMaxListModelsResponseBytes {
		return nil, fmt.Errorf("longcat: models response exceeds %d bytes", longCatMaxListModelsResponseBytes)
	}
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	var result longCatListModelsResponse
	if err = json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}
	if result.Error != nil {
		return nil, fmt.Errorf("longcat: upstream error: %v", result.Error)
	}
	if result.Data == nil {
		return nil, fmt.Errorf("invalid models list format")
	}

	return ParseListModel(ModelList{Models: result.Data}), nil
}

func (l *LongCatModel) CheckConnection(ctx context.Context, apiConfig *APIConfig) error {
	_, err := l.ListModels(ctx, apiConfig)
	return err
}

func (l *LongCatModel) Embed(ctx context.Context, modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig, modelUsage *common.ModelUsage) ([]EmbeddingData, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

// Rerank is not exposed by the LongCat API.
func (l *LongCatModel) Rerank(ctx context.Context, modelName *string, query string, documents []string, apiConfig *APIConfig, rerankConfig *RerankConfig, modelUsage *common.ModelUsage) (*RerankResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

// Balance is not exposed by the LongCat API.
func (l *LongCatModel) Balance(ctx context.Context, apiConfig *APIConfig) (map[string]interface{}, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

// TranscribeAudio (ASR) is not exposed by the LongCat API.
func (l *LongCatModel) TranscribeAudio(ctx context.Context, modelName *string, file *string, apiConfig *APIConfig, asrConfig *ASRConfig, modelUsage *common.ModelUsage) (*ASRResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

func (l *LongCatModel) TranscribeAudioWithSender(ctx context.Context, modelName *string, file *string, apiConfig *APIConfig, asrConfig *ASRConfig, modelUsage *common.ModelUsage, sender func(*string, *string) error) error {
	return fmt.Errorf("%s, no such method", l.Name())
}

// AudioSpeech (TTS) is not exposed by the LongCat API.
func (l *LongCatModel) AudioSpeech(ctx context.Context, modelName *string, audioContent *string, apiConfig *APIConfig, ttsConfig *TTSConfig, modelUsage *common.ModelUsage) (*TTSResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

func (l *LongCatModel) AudioSpeechWithSender(ctx context.Context, modelName *string, audioContent *string, apiConfig *APIConfig, ttsConfig *TTSConfig, modelUsage *common.ModelUsage, sender func(*string, *string) error) error {
	return fmt.Errorf("%s, no such method", l.Name())
}

func (l *LongCatModel) OCRFile(ctx context.Context, modelName *string, content []byte, url *string, apiConfig *APIConfig, ocrConfig *OCRConfig, modelUsage *common.ModelUsage) (*OCRFileResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

// ParseFile parse file
func (l *LongCatModel) ParseFile(ctx context.Context, modelName *string, content []byte, url *string, apiConfig *APIConfig, parseFileConfig *ParseFileConfig, modelUsage *common.ModelUsage) (*ParseFileResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

func (l *LongCatModel) ListTasks(ctx context.Context, apiConfig *APIConfig) ([]ListTaskStatus, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}

func (l *LongCatModel) ShowTask(ctx context.Context, taskID string, apiConfig *APIConfig) (*TaskResponse, error) {
	return nil, fmt.Errorf("%s, no such method", l.Name())
}