refactor: 重构项目架构，拆分代码到模块化目录

将单文件tts_server.go重构为模块化项目结构，拆分出common、dto、middleware、router、controller、service、adapter、setting等目录，优化代码组织提升可维护性

controller/tts.go

@@ -0,0 +1,174 @@
+package controller
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/volcano-tts/tts-api/adapter/volcano"
+	"github.com/volcano-tts/tts-api/common"
+	"github.com/volcano-tts/tts-api/dto"
+	"github.com/volcano-tts/tts-api/middleware"
+	"github.com/volcano-tts/tts-api/service"
+	"github.com/volcano-tts/tts-api/setting"
+)
+
+var volcanoClient *volcano.HTTPClient
+
+func InitController() {
+	volcanoClient = volcano.NewHTTPClient()
+}
+
+func OpenaiTTSHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	if !middleware.ValidateAPIKey(r) {
+		middleware.SendJSONError(w, http.StatusUnauthorized, "Invalid API key provided.", "invalid_request_error", "invalid_api_key")
+		return
+	}
+
+	if setting.TTSConfigErr != nil {
+		middleware.SendJSONError(w, http.StatusServiceUnavailable, "TTS service configuration error. Please check environment variables and restart the service.", "configuration_error", "service_unavailable")
+		return
+	}
+
+	select {
+	case middleware.ConcurrencySem <- struct{}{}:
+		defer func() { <-middleware.ConcurrencySem }()
+	default:
+		log.Printf("警告: 已达到最大并发请求数限制，拒绝请求 - 客户端IP: %s", middleware.GetClientIP(r))
+		middleware.SendJSONError(w, http.StatusServiceUnavailable, "Server is busy, maximum concurrent requests reached. Please try again later.", "concurrency_limit_error", "max_concurrent_requests")
+		return
+	}
+
+	clientIP := middleware.GetClientIP(r)
+	if !middleware.GlobalRateLimiter.Allow(clientIP) {
+		log.Printf("警告: 已超过IP速率限制，拒绝请求 - 客户端IP: %s", clientIP)
+		middleware.SendJSONError(w, http.StatusTooManyRequests, "Rate limit exceeded. Please try again later.", "rate_limit_error", "rate_limit_exceeded")
+		return
+	}
+
+	r.Body = http.MaxBytesReader(w, r.Body, common.MaxRequestBodySize)
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		if strings.Contains(err.Error(), "request body too large") {
+			return
+		}
+		http.Error(w, "Failed to read request body", http.StatusBadRequest)
+		return
+	}
+
+	var req dto.OpenAITTSRequest
+	if err := json.Unmarshal(body, &req); err != nil {
+		http.Error(w, "Invalid JSON", http.StatusBadRequest)
+		return
+	}
+
+	if req.Input == "" {
+		http.Error(w, "Input text is required", http.StatusBadRequest)
+		return
+	}
+
+	if len(req.Input) > common.MaxTextLength {
+		http.Error(w, fmt.Sprintf("Input text too long (max %d characters)", common.MaxTextLength), http.StatusBadRequest)
+		return
+	}
+
+	speed := req.Speed
+	if speed <= 0 {
+		speed = common.DefaultSpeed
+	}
+	if speed < common.MinSpeed {
+		speed = common.MinSpeed
+	}
+	if speed > common.MaxSpeed {
+		speed = common.MaxSpeed
+	}
+
+	ttsStart := time.Now()
+	result, err := volcano.Synthesis(&setting.TTSConfig, volcanoClient, req.Input, speed)
+	duration := time.Since(ttsStart)
+
+	if err != nil {
+		service.GlobalStats.AddRequest(false, duration, err.Error())
+		http.Error(w, "TTS synthesis failed", http.StatusInternalServerError)
+		return
+	}
+
+	service.GlobalStats.AddRequest(true, duration, "")
+
+	w.Header().Set("Content-Type", "audio/wav")
+	w.Header().Set("Content-Length", fmt.Sprintf("%d", len(result.AudioData)))
+	w.Header().Set("X-Request-Id", result.ReqID)
+	w.WriteHeader(http.StatusOK)
+	w.Write(result.AudioData)
+}
+
+func HealthHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+
+	if setting.TTSConfigErr != nil {
+		w.WriteHeader(http.StatusServiceUnavailable)
+	} else {
+		w.WriteHeader(http.StatusOK)
+	}
+
+	totalRequests, successfulRequests, failedRequests, totalResponseTime, recentResponseTimes, lastErrors := service.GlobalStats.GetSnapshot()
+
+	var errorRate float64
+	if totalRequests > 0 {
+		errorRate = float64(failedRequests) / float64(totalRequests) * 100
+	}
+
+	var avgResponseTime float64
+	if totalRequests > 0 {
+		avgResponseTime = totalResponseTime.Seconds() * 1000 / float64(totalRequests)
+	}
+
+	envCheckStatus := setting.CheckEnvironmentVariables()
+	allEnvVarsSet := envCheckStatus["all_required_vars_set"].(bool)
+
+	status := "ok"
+	if !allEnvVarsSet {
+		status = "configuration_error"
+	}
+
+	response := dto.HealthResponse{
+		Status:    status,
+		Service:   "ByteDance TTS to OpenAI API Adapter",
+		Version:   "2.0.0 (v3 API)",
+		Uptime:    fmt.Sprintf("%.0f seconds", time.Since(startTime).Seconds()),
+		StartTime: startTime.Format(time.RFC3339),
+		Memory:    service.GetMemoryInfo(),
+		APIStats: dto.APIStatsResponse{
+			TotalRequests:         int(totalRequests),
+			SuccessfulRequests:    successfulRequests,
+			FailedRequests:        failedRequests,
+			ErrorRatePercent:      fmt.Sprintf("%.2f", errorRate),
+			AvgResponseTimeMs:     fmt.Sprintf("%.2f", avgResponseTime),
+			RecentResponseTimesMs: recentResponseTimes,
+		},
+		Errors: dto.ErrorResponse{
+			RecentErrorsCount: len(lastErrors),
+		},
+		ConfigStatus: dto.ConfigStatusResponse{
+			AllRequiredVarsSet: allEnvVarsSet,
+			ConfigError:        setting.TTSConfigErr != nil,
+		},
+	}
+
+	json.NewEncoder(w).Encode(response)
+}
+
+var startTime time.Time
+
+func SetStartTime(t time.Time) {
+	startTime = t
+}