package server

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"sync/atomic"

	"github.com/gin-gonic/gin"
	"github.com/rs/zerolog/log"

	"github.com/fujin/anthropic-proxy/internal/auth"
	"github.com/fujin/anthropic-proxy/internal/config"
	"github.com/fujin/anthropic-proxy/internal/logging"
	"github.com/fujin/anthropic-proxy/internal/proxy"
	"github.com/fujin/anthropic-proxy/internal/ratelimit"
	"go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
)

type Server struct {
	httpServer *http.Server
	engine     *gin.Engine
	configPath string
	sanitizer  atomic.Pointer[proxy.Sanitizer]
	apiKeys    atomic.Pointer[map[string]struct{}]
}

func New(cfg *config.Config, pool *auth.Pool, profile *proxy.SniffedProfile, tracker *ratelimit.Tracker, metricsHandler http.Handler) *Server {
	s := &Server{configPath: "config.yaml"}

	san := proxy.NewSanitizer(cfg.Sanitize)
	s.sanitizer.Store(san)

	keys := makeKeySet(cfg.APIKeys)
	s.apiKeys.Store(&keys)

	gin.SetMode(gin.ReleaseMode)
	engine := gin.New()
	engine.Use(gin.Recovery())
	engine.Use(corsMiddleware())
	if cfg.Telemetry.Export.Enabled() {
		engine.Use(otelgin.Middleware(cfg.Telemetry.ServiceName))
	}
	engine.Use(s.authMiddleware())
	engine.Use(logging.GinRequestLogger())

	handler := proxy.HandleMessages(pool, profile, func() *proxy.Sanitizer {
		return s.sanitizer.Load()
	}, tracker)
	engine.POST("/v1/messages", handler)
	engine.POST("/messages", handler)

	if metricsHandler != nil {
		engine.GET("/metrics", gin.WrapH(metricsHandler))
	}

	engine.POST("/reload", s.handleReload())
	engine.POST("/debug/refresh", handleDebugRefresh(pool))
	engine.GET("/healthz", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{"status": "ok"})
	})
	engine.NoRoute(func(c *gin.Context) {
		log.Warn().Str("method", c.Request.Method).Str("path", c.Request.URL.Path).Msg("unmatched route")
		c.JSON(http.StatusNotFound, gin.H{"error": "not found"})
	})

	s.engine = engine
	s.httpServer = &http.Server{
		Addr:    fmt.Sprintf(":%d", cfg.Port),
		Handler: engine,
	}

	return s
}

func (s *Server) Start() error {
	return s.httpServer.ListenAndServe()
}

func (s *Server) Shutdown(ctx context.Context) error {
	return s.httpServer.Shutdown(ctx)
}

func (s *Server) handleReload() gin.HandlerFunc {
	return func(c *gin.Context) {
		cfg, err := config.Load(s.configPath)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("load config: %v", err)})
			return
		}

		san := proxy.NewSanitizer(cfg.Sanitize)
		s.sanitizer.Store(san)

		keys := makeKeySet(cfg.APIKeys)
		s.apiKeys.Store(&keys)

		log.Info().Int("tool_renames", len(cfg.Sanitize.Tools)).Int("system_rules", len(cfg.Sanitize.System)).Int("body_rules", len(cfg.Sanitize.Body)).Int("api_keys", len(cfg.APIKeys)).Msg("config reloaded")

		c.JSON(http.StatusOK, gin.H{
			"status":       "reloaded",
			"tool_renames": len(cfg.Sanitize.Tools),
			"system_rules": len(cfg.Sanitize.System),
			"body_rules":   len(cfg.Sanitize.Body),
			"api_keys":     len(cfg.APIKeys),
		})
	}
}

func handleDebugRefresh(pool *auth.Pool) gin.HandlerFunc {
	return func(c *gin.Context) {
		results := pool.RefreshAll(c.Request.Context())
		c.JSON(http.StatusOK, results)
	}
}

func makeKeySet(apiKeys []string) map[string]struct{} {
	keySet := make(map[string]struct{}, len(apiKeys))
	for _, k := range apiKeys {
		keySet[k] = struct{}{}
	}
	return keySet
}

func corsMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		c.Header("Access-Control-Allow-Origin", "*")
		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		c.Header("Access-Control-Allow-Headers", "Origin, Content-Type, Authorization, x-api-key, anthropic-version, anthropic-beta")

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

		c.Next()
	}
}

// authBypassPaths lists endpoints that do not require API key authentication.
var authBypassPaths = map[string]bool{
	"/healthz": true,
	"/reload":  true,
	"/metrics": true,
}

func (s *Server) authMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		if authBypassPaths[c.Request.URL.Path] {
			c.Next()
			return
		}

		token := ""
		if authHeader := c.GetHeader("Authorization"); authHeader != "" {
			token = strings.TrimPrefix(authHeader, "Bearer ")
		}
		if token == "" {
			token = c.GetHeader("x-api-key")
		}

		if token == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing authentication"})
			return
		}

		keys := s.apiKeys.Load()
		if _, ok := (*keys)[token]; !ok {
			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"error": "invalid api key"})
			return
		}

		c.Next()
	}
}