package main

import (
	"context"
	"log"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/gin-gonic/gin"

	"monica-go-completion-backend/internal/api"
	"monica-go-completion-backend/internal/completion"
	"monica-go-completion-backend/internal/lsp"
)

type config struct {
	Port         string
	GoplsPath    string
	WorkspaceDir string
	AllowOrigin  string
}

func main() {
	cfg := loadConfig()

	lspClient, err := lsp.NewClient(context.Background(), cfg.GoplsPath, cfg.WorkspaceDir)
	if err != nil {
		log.Fatalf("create gopls client failed: %v", err)
	}
	defer func() {
		_ = lspClient.Close()
	}()

	completionService := completion.NewService(lspClient)

	router := gin.New()
	router.Use(gin.Logger())
	router.Use(gin.Recovery())
	router.Use(corsMiddleware(cfg.AllowOrigin))
	api.RegisterRoutes(router, completionService)

	server := &http.Server{
		Addr:         ":" + cfg.Port,
		Handler:      router,
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 30 * time.Second,
		IdleTimeout:  60 * time.Second,
	}

	go func() {
		log.Printf("completion backend listening on :%s", cfg.Port)
		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("http server failed: %v", err)
		}
	}()

	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
	<-sigCh

	shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	if err := server.Shutdown(shutdownCtx); err != nil {
		log.Printf("http shutdown failed: %v", err)
	}
}

func loadConfig() config {
	cwd, err := os.Getwd()
	if err != nil {
		cwd = "."
	}
	return config{
		Port:         getenv("PORT", "8080"),
		GoplsPath:    getenv("GOPLS_PATH", "gopls"),
		WorkspaceDir: getenv("WORKSPACE_DIR", cwd),
		AllowOrigin:  getenv("CORS_ALLOW_ORIGIN", "*"),
	}
}

func getenv(key, fallback string) string {
	v := os.Getenv(key)
	if v == "" {
		return fallback
	}
	return v
}

func corsMiddleware(allowOrigin string) gin.HandlerFunc {
	return func(c *gin.Context) {
		c.Header("Access-Control-Allow-Origin", allowOrigin)
		c.Header("Access-Control-Allow-Methods", "GET,POST,OPTIONS")
		c.Header("Access-Control-Allow-Headers", "Content-Type,Authorization")

		if c.Request.Method == http.MethodOptions {
			c.AbortWithStatus(http.StatusNoContent)
			return
		}
		c.Next()
	}
}