package main

import (
	"bufio"
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"hub.gaomia.site/titor/YunShu/pkg/mdprint"
)

var (
	llmOnce  sync.Once
	llmHost  = "https://ark.cn-beijing.volces.com/api/v3/chat/completions"
	llmModel = "doubao-seed-2-0-pro-260215"
	llmKey   = ""
)

func loadLLMConfig() {
	llmOnce.Do(func() {
		cfg, err := LoadConfig()
		if err == nil {
			if cfg.LLM.Host != "" {
				llmHost = cfg.LLM.Host
			}
			if cfg.LLM.Model != "" {
				llmModel = cfg.LLM.Model
			}
			if cfg.LLM.Key != "" {
				llmKey = cfg.LLM.Key
			}
		}

		if v := os.Getenv("LLM_ENDPOINT"); v != "" {
			llmHost = v
		}
		if v := os.Getenv("LLM_MODEL"); v != "" {
			llmModel = v
		}
		if v := os.Getenv("LLM_API_KEY"); v != "" {
			llmKey = v
		}
		if v := os.Getenv("OPENAI_API_KEY"); v != "" && llmKey == "" {
			llmKey = v
		}
	})
}

// GetLLMKey 获取 API Key，优先使用已加载的密钥
func GetLLMKey() (string, error) {
	loadLLMConfig()
	if llmKey == "" {
		return "", fmt.Errorf("未配置 API Key。请运行 'weather-cia onboard' 初始化，或设置 LLM_API_KEY 环境变量")
	}
	return llmKey, nil
}

// CallLLM 调用大模型 API（兼容 OpenAI Chat Completion 格式）
func CallLLM(messages []Message, toolDefs []ToolDef) (*OpenAIResponse, error) {
	loadLLMConfig()
	apiKey, err := GetLLMKey()
	if err != nil {
		return nil, err
	}

	start := time.Now()

	reqBody := map[string]interface{}{
		"model":    llmModel,
		"messages": messages,
	}

	// 注册工具定义
	if len(toolDefs) > 0 {
		tools := make([]OpenAITool, 0, len(toolDefs))
		for _, td := range toolDefs {
			tools = append(tools, OpenAITool{
				Type: "function",
				Function: OpenAIToolFunc{
					Name:        td.Name,
					Description: td.Description,
					Parameters:  td.Parameters,
				},
			})
		}
		reqBody["tools"] = tools
		reqBody["tool_choice"] = "auto"
	}

	body, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("序列化请求失败: %w", err)
	}

	req, err := http.NewRequest("POST", llmHost, bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %w", err)
	}

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

	client := &http.Client{Timeout: 120 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求 LLM 失败: %w", err)
	}
	defer resp.Body.Close()

	respData, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("读取响应失败: %w", err)
	}

	if resp.StatusCode != 200 {
		var errResp OpenAIErrorResponse
		if json.Unmarshal(respData, &errResp) == nil && errResp.Error.Message != "" {
			return nil, fmt.Errorf("LLM API 错误 [%s]: %s", errResp.Error.Type, errResp.Error.Message)
		}
		return nil, fmt.Errorf("LLM API 返回 HTTP %d: %s", resp.StatusCode, string(respData))
	}

	var result OpenAIResponse
	if err := json.Unmarshal(respData, &result); err != nil {
		return nil, fmt.Errorf("解析响应失败: %w", err)
	}

	if len(result.Choices) == 0 {
		return nil, fmt.Errorf("LLM 返回空结果")
	}

	if result.Usage.TotalTokens > 0 {
		infoLog("LLM 调用完成",
			"tokens", result.Usage.TotalTokens,
			"duration", time.Since(start).Round(time.Millisecond*100).String(),
		)
	}
	return &result, nil
}

// ============================================================
// 流式输出 (SSE)
// ============================================================

type accumulatedToolCall struct {
	ID   string
	Type string
	Name string
	Args string
}

type sseChunk struct {
	ID      string      `json:"id"`
	Object  string      `json:"object"`
	Created int64       `json:"created"`
	Model   string      `json:"model"`
	Choices []sseChoice `json:"choices"`
	Usage   *OpenAIUsage `json:"usage,omitempty"`
}

type sseChoice struct {
	Index        int         `json:"index"`
	Delta        sseDelta    `json:"delta"`
	FinishReason *string     `json:"finish_reason"`
}

type sseDelta struct {
	Role      string              `json:"role,omitempty"`
	Content   string              `json:"content,omitempty"`
	ToolCalls []sseToolCallDelta  `json:"tool_calls,omitempty"`
}

type sseToolCallDelta struct {
	Index    int                        `json:"index"`
	ID       string                     `json:"id,omitempty"`
	Type     string                     `json:"type,omitempty"`
	Function *sseToolCallFunctionDelta  `json:"function,omitempty"`
}

type sseToolCallFunctionDelta struct {
	Name      string `json:"name,omitempty"`
	Arguments string `json:"arguments,omitempty"`
}

// CallLLMStream 流式调用 LLM，按 \n\n 段落边界缓冲后通过 mdprint 渲染到 stdout
func CallLLMStream(messages []Message, toolDefs []ToolDef) (*OpenAIResponse, error) {
	loadLLMConfig()
	apiKey, err := GetLLMKey()
	if err != nil {
		return nil, err
	}

	start := time.Now()

	reqBody := map[string]any{
		"model":    llmModel,
		"messages": messages,
		"stream":   true,
	}

	if len(toolDefs) > 0 {
		tools := make([]OpenAITool, 0, len(toolDefs))
		for _, td := range toolDefs {
			tools = append(tools, OpenAITool{
				Type: "function",
				Function: OpenAIToolFunc{
					Name:        td.Name,
					Description: td.Description,
					Parameters:  td.Parameters,
				},
			})
		}
		reqBody["tools"] = tools
		reqBody["tool_choice"] = "auto"
	}

	body, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("序列化请求失败: %w", err)
	}

	req, err := http.NewRequest("POST", llmHost, bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %w", err)
	}

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

	client := &http.Client{Timeout: 120 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求 LLM 失败: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		respData, _ := io.ReadAll(resp.Body)
		var errResp OpenAIErrorResponse
		if json.Unmarshal(respData, &errResp) == nil && errResp.Error.Message != "" {
			return nil, fmt.Errorf("LLM API 错误 [%s]: %s", errResp.Error.Type, errResp.Error.Message)
		}
		return nil, fmt.Errorf("LLM API 返回 HTTP %d: %s", resp.StatusCode, string(respData))
	}

	reader := bufio.NewReader(resp.Body)
	var fullContent strings.Builder
	var blockBuf strings.Builder
	toolCallAccums := make(map[int]*accumulatedToolCall)
	var responseID, responseModel string
	var responseCreated int64
	var usage *OpenAIUsage

	for {
		line, err := reader.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, fmt.Errorf("读取流响应失败: %w", err)
		}

		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		if !strings.HasPrefix(line, "data: ") {
			continue
		}

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

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

		if responseID == "" && chunk.ID != "" {
			responseID = chunk.ID
		}
		if responseModel == "" && chunk.Model != "" {
			responseModel = chunk.Model
		}
		if responseCreated == 0 && chunk.Created != 0 {
			responseCreated = chunk.Created
		}
		if chunk.Usage != nil {
			usage = chunk.Usage
		}

		for _, choice := range chunk.Choices {
			delta := choice.Delta

			if delta.Content != "" {
				fullContent.WriteString(delta.Content)
				blockBuf.WriteString(delta.Content)
				tryFlushBlocks(&blockBuf)
			}

			for _, tc := range delta.ToolCalls {
				acc, ok := toolCallAccums[tc.Index]
				if !ok {
					acc = &accumulatedToolCall{}
					toolCallAccums[tc.Index] = acc
				}
				if tc.ID != "" {
					acc.ID = tc.ID
				}
				if tc.Type != "" {
					acc.Type = tc.Type
				}
				if tc.Function != nil {
					if tc.Function.Name != "" {
						acc.Name = tc.Function.Name
					}
					acc.Args += tc.Function.Arguments
				}
			}
		}
	}

	// 流结束，刷残段
	if blockBuf.Len() > 0 {
		mdprint.Print(blockBuf.String())
	}

	// 重建响应
	var choice OpenAIChoice

	if len(toolCallAccums) > 0 {
		var tcs []ToolCall
		for i := 0; i < len(toolCallAccums); i++ {
			acc := toolCallAccums[i]
			if acc == nil {
				continue
			}
			tcs = append(tcs, ToolCall{
				ID:   acc.ID,
				Type: acc.Type,
				Function: ToolCallFunction{
					Name:      acc.Name,
					Arguments: acc.Args,
				},
			})
		}
		choice.Message.ToolCalls = tcs
	} else {
		content := fullContent.String()
		if content != "" {
			choice.Message.Content = &content
		}
	}

	result := &OpenAIResponse{
		ID:      responseID,
		Object:  "chat.completion",
		Created: responseCreated,
		Model:   responseModel,
		Choices: []OpenAIChoice{choice},
	}

	if usage != nil && usage.TotalTokens > 0 {
		result.Usage = *usage
		infoLog("LLM 调用完成",
			"tokens", usage.TotalTokens,
			"duration", time.Since(start).Round(time.Millisecond*100).String(),
		)
	}

	return result, nil
}

// tryFlushBlocks 检测 blockBuf 中是否有完整的 Markdown block（以 \n\n 为界）
// 有则通过 mdprint 渲染到 stdout，剩余残段留在 buf 中继续缓冲
func tryFlushBlocks(buf *strings.Builder) {
	content := buf.String()
	idx := strings.LastIndex(content, "\n\n")
	if idx < 0 {
		return
	}

	complete := strings.TrimRight(content[:idx], "\n\r\t ")
	if complete == "" {
		return
	}

	mdprint.Print(complete)

	remainder := content[idx+2:]
	buf.Reset()
	if remainder != "" {
		buf.WriteString(remainder)
	}
}