package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/google/generative-ai-go/genai"
	"github.com/rs/cors"
	"google.golang.org/api/iterator"
	"google.golang.org/api/option"
)

// --- 配置部分 ---

// API密钥列表 (请替换为您自己的密钥)
var apiKeys = []string{
	"AIzaSyBUIl9AisD8FHUn5HLQcriXZnF4n5MqnWU",
	"AIzaSyAId4YPsZSTLJ5_fA5BESjYxWZBzwADTJI",
	// 在此添加更多密钥
}

// 定义支持的模型信息
var supportedModels = []ModelInfo{
	{
		ID:          "gemini-2.5-flash-preview-05-20",
		Object:      "model",
		Created:     time.Now().Unix(),
		OwnedBy:     "google",
		Description: "Gemini 2.5 Flash Preview - 最新实验性模型",
	},
	{
		ID:          "gemini-2.5-flash",
		Object:      "model",
		Created:     time.Now().Unix(),
		OwnedBy:     "google",
		Description: "gemini-2.5-flash稳定经典专业模型",
	},
	{
		ID:          "gemini-2.5-pro",
		Object:      "model",
		Created:     time.Now().Unix(),
		OwnedBy:     "google",
		Description: "Gemini 2.5 Pro 专业模型",
	},
}

// 将OpenAI模型名称映射到Gemini模型名称
// 根据您的要求，键和值现在是相同的，不做任何转换。
var modelMapping = map[string]string{
	"gemini-2.5-flash-preview-05-20": "gemini-2.5-flash-preview-05-20",
	"gemini-2.5-flash":               "gemini-2.5-flash",
	"gemini-2.5-pro":                 "gemini-2.5-pro",
}

// 配置安全设置 (全部禁用)
var safetySettings = []*genai.SafetySetting{
	{
		Category:  genai.HarmCategoryHarassment,
		Threshold: genai.HarmBlockNone,
	},
	{
		Category:  genai.HarmCategoryHateSpeech,
		Threshold: genai.HarmBlockNone,
	},
	{
		Category:  genai.HarmCategorySexuallyExplicit,
		Threshold: genai.HarmBlockNone,
	},
	{
		Category:  genai.HarmCategoryDangerousContent,
		Threshold: genai.HarmBlockNone,
	},
}

const maxRetries = 3

// --- 数据结构 (用于JSON序列化/反序列化) ---

type ChatMessage struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type ChatCompletionRequest struct {
	Model       string        `json:"model"`
	Messages    []ChatMessage `json:"messages"`
	Stream      bool          `json:"stream"`
	MaxTokens   int32         `json:"max_tokens,omitempty"`
	Temperature float32       `json:"temperature,omitempty"`
	TopP        float32       `json:"top_p,omitempty"`
}

type ChatCompletionResponse struct {
	ID      string   `json:"id"`
	Object  string   `json:"object"`
	Created int64    `json:"created"`
	Model   string   `json:"model"`
	Choices []Choice `json:"choices"`
	Usage   Usage    `json:"usage"`
}

type Choice struct {
	Index        int         `json:"index"`
	Message      ChatMessage `json:"message"`
	FinishReason string      `json:"finish_reason"`
}

type Usage struct {
	PromptTokens     int `json:"prompt_tokens"`
	CompletionTokens int `json:"completion_tokens"`
	TotalTokens      int `json:"total_tokens"`
}

type ChatCompletionStreamResponse struct {
	ID      string         `json:"id"`
	Object  string         `json:"object"`
	Created int64          `json:"created"`
	Model   string         `json:"model"`
	Choices []StreamChoice `json:"choices"`
}

type StreamChoice struct {
	Index        int         `json:"index"`
	Delta        ChatMessage `json:"delta"`
	FinishReason *string     `json:"finish_reason,omitempty"`
}

type ModelInfo struct {
	ID          string `json:"id"`
	Object      string `json:"object"`
	Created     int64  `json:"created"`
	OwnedBy     string `json:"owned_by"`
	Description string `json:"description"`
}

type ModelListResponse struct {
	Object string      `json:"object"`
	Data   []ModelInfo `json:"data"`
}

// --- 核心逻辑 ---

func getRandomAPIKey() string {
	if len(apiKeys) == 0 {
		log.Fatal("API密钥列表为空，请在 `apiKeys` 变量中配置密钥。")
	}
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	return apiKeys[r.Intn(len(apiKeys))]
}

// convertMessages 将OpenAI格式的消息转换为Gemini格式的历史记录和最后一个用户的提示
func convertMessages(messages []ChatMessage) (history []*genai.Content, lastPrompt []genai.Part, systemInstruction *genai.Content) {
	if len(messages) == 0 {
		return nil, nil, nil
	}

	for i, msg := range messages {
		var role string
		if msg.Role == "system" {
			systemInstruction = &genai.Content{Parts: []genai.Part{genai.Text(msg.Content)}}
			continue
		}

		if i == len(messages)-1 && msg.Role == "user" {
			lastPrompt = append(lastPrompt, genai.Text(msg.Content))
			continue
		}

		if msg.Role == "assistant" {
			role = "model"
		} else {
			role = "user"
		}

		history = append(history, &genai.Content{
			Role:  role,
			Parts: []genai.Part{genai.Text(msg.Content)},
		})
	}
	return history, lastPrompt, systemInstruction
}

func chatCompletionsHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "仅支持POST方法", http.StatusMethodNotAllowed)
		return
	}

	var req ChatCompletionRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, fmt.Sprintf("解析请求体失败: %v", err), http.StatusBadRequest)
		return
	}

	// 根据您的要求，直接使用请求中的模型名称
	modelName := req.Model
	log.Printf("接收到模型请求: '%s'，将直接使用该名称。", modelName)


	history, lastPrompt, systemInstruction := convertMessages(req.Messages)

	var lastErr error
	usedKeys := make(map[string]bool)

	for i := 0; i < maxRetries; i++ {
		ctx := context.Background()
		apiKey := getRandomAPIKey()

		if len(usedKeys) < len(apiKeys) {
			for usedKeys[apiKey] {
				apiKey = getRandomAPIKey()
			}
		}
		usedKeys[apiKey] = true

		log.Printf("尝试第 %d 次, 使用密钥: ...%s", i+1, apiKey[len(apiKey)-4:])

		client, err := genai.NewClient(ctx, option.WithAPIKey(apiKey))
		if err != nil {
			lastErr = fmt.Errorf("创建客户端失败: %v", err)
			log.Println(lastErr)
			continue
		}
		defer client.Close()

		model := client.GenerativeModel(modelName)
		model.SystemInstruction = systemInstruction
		model.SafetySettings = safetySettings
		model.SetTemperature(req.Temperature)
		model.SetTopP(req.TopP)
		if req.MaxTokens > 0 {
			model.SetMaxOutputTokens(req.MaxTokens)
		}
		
		chat := model.StartChat()
		chat.History = history

		if req.Stream {
			err = handleStream(w, ctx, chat, lastPrompt, req.Model)
		} else {
			err = handleNonStream(w, ctx, model, chat, lastPrompt, req.Model)
		}

		if err == nil {
			return 
		}

		lastErr = err
		log.Printf("第 %d 次尝试失败: %v", i+1, err)
		time.Sleep(1 * time.Second)
	}

	http.Error(w, fmt.Sprintf("所有重试均失败: %v", lastErr), http.StatusInternalServerError)
}

func handleStream(w http.ResponseWriter, ctx context.Context, chat *genai.ChatSession, prompt []genai.Part, modelID string) error {
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	iter := chat.SendMessageStream(ctx, prompt...)
	for {
		resp, err := iter.Next()
		if err == iterator.Done {
			break
		}
		if err != nil {
			return fmt.Errorf("流式生成内容失败: %v", err)
		}

		var contentBuilder strings.Builder
		for _, part := range resp.Candidates[0].Content.Parts {
			if txt, ok := part.(genai.Text); ok {
				contentBuilder.WriteString(string(txt))
			}
		}
		
		chunk := ChatCompletionStreamResponse{
			ID:      fmt.Sprintf("chatcmpl-%d", time.Now().Unix()),
			Object:  "chat.completion.chunk",
			Created: time.Now().Unix(),
			Model:   modelID,
			Choices: []StreamChoice{
				{
					Index: 0,
					Delta: ChatMessage{
						Role:    "assistant",
						Content: contentBuilder.String(),
					},
				},
			},
		}

		var buf bytes.Buffer
		if err := json.NewEncoder(&buf).Encode(chunk); err != nil {
			return fmt.Errorf("序列化流式块失败: %v", err)
		}

		fmt.Fprintf(w, "data: %s\n\n", buf.String())
		if flusher, ok := w.(http.Flusher); ok {
			flusher.Flush()
		}
	}

	finishReason := "stop"
	doneChunk := ChatCompletionStreamResponse{
		ID:      fmt.Sprintf("chatcmpl-%d-done", time.Now().Unix()),
		Object:  "chat.completion.chunk",
		Created: time.Now().Unix(),
		Model:   modelID,
		Choices: []StreamChoice{
			{
				Index:        0,
				FinishReason: &finishReason,
			},
		},
	}
	var buf bytes.Buffer
	json.NewEncoder(&buf).Encode(doneChunk)
	fmt.Fprintf(w, "data: %s\n\n", buf.String())
	fmt.Fprintf(w, "data: [DONE]\n\n")
	if flusher, ok := w.(http.Flusher); ok {
		flusher.Flush()
	}

	return nil
}

func handleNonStream(w http.ResponseWriter, ctx context.Context, model *genai.GenerativeModel, chat *genai.ChatSession, prompt []genai.Part, modelID string) error {
	resp, err := chat.SendMessage(ctx, prompt...)
	if err != nil {
		return fmt.Errorf("生成内容失败: %v", err)
	}

	var contentBuilder strings.Builder
	if len(resp.Candidates) > 0 && resp.Candidates[0].Content != nil {
		for _, part := range resp.Candidates[0].Content.Parts {
			if txt, ok := part.(genai.Text); ok {
				contentBuilder.WriteString(string(txt))
			}
		}
	}
	
	// 计算Token
	var promptParts []genai.Part
	for _, c := range chat.History {
		promptParts = append(promptParts, c.Parts...)
	}
	promptParts = append(promptParts, prompt...)

	promptTokenCount, err := model.CountTokens(ctx, promptParts...)
	if err != nil {
		return fmt.Errorf("计算prompt tokens失败: %v", err)
	}

	completionTokenCount, err := model.CountTokens(ctx, resp.Candidates[0].Content.Parts...)
	if err != nil {
		return fmt.Errorf("计算completion tokens失败: %v", err)
	}
	
	response := ChatCompletionResponse{
		ID:      fmt.Sprintf("chatcmpl-%d", time.Now().Unix()),
		Object:  "chat.completion",
		Created: time.Now().Unix(),
		Model:   modelID,
		Choices: []Choice{
			{
				Index: 0,
				Message: ChatMessage{
					Role:    "assistant",
					Content: contentBuilder.String(),
				},
				FinishReason: "stop",
			},
		},
		Usage: Usage{
			PromptTokens:     int(promptTokenCount.TotalTokens),
			CompletionTokens: int(completionTokenCount.TotalTokens),
			TotalTokens:      int(promptTokenCount.TotalTokens) + int(completionTokenCount.TotalTokens),
		},
	}

	w.Header().Set("Content-Type", "application/json")
	return json.NewEncoder(w).Encode(response)
}


func modelsHandler(w http.ResponseWriter, r *http.Request) {
	resp := ModelListResponse{
		Object: "list",
		Data:   supportedModels,
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}

func rootHandler(w http.ResponseWriter, r *http.Request) {
	info := map[string]interface{}{
		"name":        "Gemini Official API (Go Version)",
		"version":     "1.3.0",
		"description": "Google Gemini官方API接口服务",
		"endpoints": map[string]string{
			"models": "/v1/models",
			"chat":   "/v1/chat/completions",
			"health": "/health",
		},
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(info)
}

func healthHandler(w http.ResponseWriter, r *http.Request) {
	var modelIDs []string
	for _, m := range supportedModels {
		modelIDs = append(modelIDs, m.ID)
	}
	health := map[string]interface{}{
		"status":           "healthy",
		"timestamp":        time.Now().Unix(),
		"api":              "gemini-official-go",
		"available_models": modelIDs,
		"version":          "1.3.0",
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(health)
}

func main() {
	mux := http.NewServeMux()

	mux.HandleFunc("/", rootHandler)
	mux.HandleFunc("/health", healthHandler)
	mux.HandleFunc("/v1/models", modelsHandler)
	mux.HandleFunc("/v1/chat/completions", chatCompletionsHandler)
	mux.HandleFunc("/v1/chat/completions/v1/models", modelsHandler)

	c := cors.New(cors.Options{
		AllowedOrigins:   []string{"*"},
		AllowedMethods:   []string{"GET", "POST", "OPTIONS"},
		AllowedHeaders:   []string{"*"},
		AllowCredentials: true,
	})
	handler := c.Handler(mux)

	port := "7860"
	log.Println("🚀 启动Gemini官方API服务器 (Go版本)")
	log.Printf("📊 支持的模型: %v", func() []string {
		var ids []string
		for _, m := range supportedModels {
			ids = append(ids, m.ID)
		}
		return ids
	}())
	log.Printf("🔑 已配置 %d 个API密钥", len(apiKeys))
	log.Println("🔄 支持自动重试和密钥轮换")
	log.Printf("🔗 服务器正在监听 http://0.0.0.0:%s", port)

	envKey := os.Getenv("GEMINI_API_KEY")
	if envKey != "" {
		apiKeys = strings.Split(envKey, ",")
		log.Printf("从环境变量 GEMINI_API_KEY 加载了 %d 个密钥", len(apiKeys))
	}

	if err := http.ListenAndServe(":"+port, handler); err != nil {
		log.Fatalf("启动服务器失败: %v", err)
	}
}