package ai

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
)

const AliyunBaseURL = "https://dashscope.aliyuncs.com/compatible-mode/v1"
const AliyunAppURLTemplate = "https://dashscope.aliyuncs.com/api/v2/apps/agent/%s/compatible-mode/v1"

type AliyunClient struct {
	apiKey  string
	model   string
	appID   string
	baseURL string
}

func NewAliyunClient(cfg *Config) *AliyunClient {
	model := cfg.Model
	if model == "" {
		model = "qwen-turbo"
	}

	client := &AliyunClient{
		apiKey: cfg.APIKey,
		model:  model,
		appID:  cfg.AppID,
	}

	if cfg.AppID != "" {
		client.baseURL = fmt.Sprintf(AliyunAppURLTemplate, cfg.AppID)
	} else {
		client.baseURL = AliyunBaseURL
	}

	return client
}

type aliyunRequest struct {
	Model          string    `json:"model"`
	Messages       []Message `json:"messages"`
	Stream         bool      `json:"stream,omitempty"`
	EnableThinking bool      `json:"enable_thinking,omitempty"`
	ThinkingBudget int       `json:"thinking_budget,omitempty"`
}

type aliyunResponse struct {
	ID      string `json:"id"`
	Choices []struct {
		Index   int `json:"index"`
		Message struct {
			Role             string `json:"role"`
			Content          string `json:"content"`
			ReasoningContent string `json:"reasoning_content"`
		} `json:"message"`
		Delta struct {
			Content          string `json:"content"`
			ReasoningContent string `json:"reasoning_content"`
		} `json:"delta"`
		FinishReason string `json:"finish_reason"`
	} `json:"choices"`
	Error *struct {
		Message string `json:"message"`
		Code    string `json:"code"`
	} `json:"error"`
}

func (c *AliyunClient) Chat(ctx context.Context, messages []Message) (string, error) {
	if c.apiKey == "" {
		return "", fmt.Errorf("阿里云 API Key 未配置")
	}

	filteredMessages := messages
	if c.appID != "" {
		filteredMessages = filterSystemMessages(messages)
	}

	reqBody := aliyunRequest{
		Model:    c.model,
		Messages: filteredMessages,
		Stream:   false,
	}

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+"/chat/completions", bytes.NewReader(body))
	if err != nil {
		return "", err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+c.apiKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("调用AI服务失败: %v", err)
	}
	defer resp.Body.Close()

	var result aliyunResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", fmt.Errorf("解析AI响应失败: %v", err)
	}

	if result.Error != nil {
		return "", fmt.Errorf("AI服务错误: %s", result.Error.Message)
	}

	if len(result.Choices) == 0 {
		return "", fmt.Errorf("AI未返回有效响应")
	}

	return result.Choices[0].Message.Content, nil
}

func (c *AliyunClient) ChatStream(ctx context.Context, messages []Message, writer io.Writer) error {
	if c.apiKey == "" {
		return fmt.Errorf("阿里云 API Key 未配置")
	}

	filteredMessages := messages
	if c.appID != "" {
		filteredMessages = filterSystemMessages(messages)
	}

	// 启用思考过程（与原 server 一致）
	reqBody := aliyunRequest{
		Model:          c.model,
		Messages:       filteredMessages,
		Stream:         true,
		EnableThinking: true,  // 启用思考过程
		ThinkingBudget: 2048,  // 思考过程最大 token 数
	}

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+"/chat/completions", bytes.NewReader(body))
	if err != nil {
		return err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+c.apiKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		respBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("AI服务返回错误: %s", string(respBody))
	}

	reader := bufio.NewReader(resp.Body)
	isThinking := false

	for {
		line, err := reader.ReadString('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}

		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "data:") {
			data := strings.TrimPrefix(line, "data:")
			data = strings.TrimSpace(data)
			if data == "[DONE]" {
				break
			}

			var streamResp aliyunResponse
			if err := json.Unmarshal([]byte(data), &streamResp); err != nil {
				continue
			}

			if len(streamResp.Choices) > 0 {
				choice := streamResp.Choices[0]

				if choice.Delta.ReasoningContent != "" {
					if !isThinking {
						sseData := "data: {\"type\":\"thinking_start\"}\n\n"
						writer.Write([]byte(sseData))
						if flusher, ok := writer.(http.Flusher); ok {
							flusher.Flush()
						}
						isThinking = true
					}
					sseData := fmt.Sprintf("data: {\"type\":\"thinking\",\"content\":%s}\n\n", jsonEscape(choice.Delta.ReasoningContent))
					writer.Write([]byte(sseData))
					if flusher, ok := writer.(http.Flusher); ok {
						flusher.Flush()
					}
				}

				if choice.Delta.Content != "" {
					if isThinking {
						sseData := "data: {\"type\":\"thinking_end\"}\n\n"
						writer.Write([]byte(sseData))
						if flusher, ok := writer.(http.Flusher); ok {
							flusher.Flush()
						}
						isThinking = false
					}
					sseData := fmt.Sprintf("data: {\"type\":\"content\",\"content\":%s}\n\n", jsonEscape(choice.Delta.Content))
					writer.Write([]byte(sseData))
					if flusher, ok := writer.(http.Flusher); ok {
						flusher.Flush()
					}
				}
			}
		}
	}

	return nil
}

func jsonEscape(s string) string {
	b, _ := json.Marshal(s)
	return string(b)
}

func filterSystemMessages(messages []Message) []Message {
	filtered := make([]Message, 0, len(messages))
	for _, msg := range messages {
		if msg.Role != "system" {
			filtered = append(filtered, msg)
		}
	}
	return filtered
}