package amp

import (
	"net"
	"net/http/httputil"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers/claude"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers/gemini"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers/openai"
	log "github.com/sirupsen/logrus"
)

// localhostOnlyMiddleware returns a middleware that dynamically checks the module's
// localhost restriction setting. This allows hot-reload of the restriction without restarting.
func (m *AmpModule) localhostOnlyMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Check current setting (hot-reloadable)
		if !m.IsRestrictedToLocalhost() {
			c.Next()
			return
		}

		// Use actual TCP connection address (RemoteAddr) to prevent header spoofing
		// This cannot be forged by X-Forwarded-For or other client-controlled headers
		remoteAddr := c.Request.RemoteAddr

		// RemoteAddr format is "IP:port" or "[IPv6]:port", extract just the IP
		host, _, err := net.SplitHostPort(remoteAddr)
		if err != nil {
			// Try parsing as raw IP (shouldn't happen with standard HTTP, but be defensive)
			host = remoteAddr
		}

		// Parse the IP to handle both IPv4 and IPv6
		ip := net.ParseIP(host)
		if ip == nil {
			log.Warnf("amp management: invalid RemoteAddr %s, denying access", remoteAddr)
			c.AbortWithStatusJSON(403, gin.H{
				"error": "Access denied: management routes restricted to localhost",
			})
			return
		}

		// Check if IP is loopback (127.0.0.1 or ::1)
		if !ip.IsLoopback() {
			log.Warnf("amp management: non-localhost connection from %s attempted access, denying", remoteAddr)
			c.AbortWithStatusJSON(403, gin.H{
				"error": "Access denied: management routes restricted to localhost",
			})
			return
		}

		c.Next()
	}
}

// noCORSMiddleware disables CORS for management routes to prevent browser-based attacks.
// This overwrites any global CORS headers set by the server.
func noCORSMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Remove CORS headers to prevent cross-origin access from browsers
		c.Header("Access-Control-Allow-Origin", "")
		c.Header("Access-Control-Allow-Methods", "")
		c.Header("Access-Control-Allow-Headers", "")
		c.Header("Access-Control-Allow-Credentials", "")

		// For OPTIONS preflight, deny with 403
		if c.Request.Method == "OPTIONS" {
			c.AbortWithStatus(403)
			return
		}

		c.Next()
	}
}

// registerManagementRoutes registers Amp management proxy routes
// These routes proxy through to the Amp control plane for OAuth, user management, etc.
// Uses dynamic middleware and proxy getter for hot-reload support.
func (m *AmpModule) registerManagementRoutes(engine *gin.Engine, baseHandler *handlers.BaseAPIHandler) {
	ampAPI := engine.Group("/api")

	// Always disable CORS for management routes to prevent browser-based attacks
	ampAPI.Use(noCORSMiddleware())

	// Apply dynamic localhost-only restriction (hot-reloadable via m.IsRestrictedToLocalhost())
	ampAPI.Use(m.localhostOnlyMiddleware())

	if m.IsRestrictedToLocalhost() {
		log.Info("amp management routes restricted to localhost only (CORS disabled)")
	} else {
		log.Warn("amp management routes are NOT restricted to localhost - this is insecure!")
	}

	// Dynamic proxy handler that uses m.getProxy() for hot-reload support
	proxyHandler := func(c *gin.Context) {
		proxy := m.getProxy()
		if proxy == nil {
			c.JSON(503, gin.H{"error": "amp upstream proxy not available"})
			return
		}
		proxy.ServeHTTP(c.Writer, c.Request)
	}

	// Management routes - these are proxied directly to Amp upstream
	ampAPI.Any("/internal", proxyHandler)
	ampAPI.Any("/internal/*path", proxyHandler)
	ampAPI.Any("/user", proxyHandler)
	ampAPI.Any("/user/*path", proxyHandler)
	ampAPI.Any("/auth", proxyHandler)
	ampAPI.Any("/auth/*path", proxyHandler)
	ampAPI.Any("/meta", proxyHandler)
	ampAPI.Any("/meta/*path", proxyHandler)
	ampAPI.Any("/ads", proxyHandler)
	ampAPI.Any("/telemetry", proxyHandler)
	ampAPI.Any("/telemetry/*path", proxyHandler)
	ampAPI.Any("/threads", proxyHandler)
	ampAPI.Any("/threads/*path", proxyHandler)
	ampAPI.Any("/otel", proxyHandler)
	ampAPI.Any("/otel/*path", proxyHandler)
	ampAPI.Any("/tab", proxyHandler)
	ampAPI.Any("/tab/*path", proxyHandler)

	// Root-level routes that AMP CLI expects without /api prefix
	// These need the same security middleware as the /api/* routes (dynamic for hot-reload)
	rootMiddleware := []gin.HandlerFunc{noCORSMiddleware(), m.localhostOnlyMiddleware()}
	engine.GET("/threads/*path", append(rootMiddleware, proxyHandler)...)
	engine.GET("/threads.rss", append(rootMiddleware, proxyHandler)...)

	// Root-level auth routes for CLI login flow
	// Amp uses multiple auth routes: /auth/cli-login, /auth/callback, /auth/sign-in, /auth/logout
	// We proxy all /auth/* to support the complete OAuth flow
	engine.Any("/auth", append(rootMiddleware, proxyHandler)...)
	engine.Any("/auth/*path", append(rootMiddleware, proxyHandler)...)

	// Google v1beta1 passthrough with OAuth fallback
	// AMP CLI uses non-standard paths like /publishers/google/models/...
	// We bridge these to our standard Gemini handler to enable local OAuth.
	// If no local OAuth is available, falls back to ampcode.com proxy.
	geminiHandlers := gemini.NewGeminiAPIHandler(baseHandler)
	geminiBridge := createGeminiBridgeHandler(geminiHandlers)
	geminiV1Beta1Fallback := NewFallbackHandler(func() *httputil.ReverseProxy {
		return m.getProxy()
	})
	geminiV1Beta1Handler := geminiV1Beta1Fallback.WrapHandler(geminiBridge)

	// Route POST model calls through Gemini bridge when a local provider exists, otherwise proxy.
	// All other methods (e.g., GET model listing) always proxy to upstream to preserve Amp CLI behavior.
	ampAPI.Any("/provider/google/v1beta1/*path", func(c *gin.Context) {
		if c.Request.Method == "POST" {
			// Attempt to extract the model name from the AMP-style path
			if path := c.Param("path"); strings.Contains(path, "/models/") {
				modelPart := path[strings.Index(path, "/models/")+len("/models/"):]
				if colonIdx := strings.Index(modelPart, ":"); colonIdx > 0 {
					modelPart = modelPart[:colonIdx]
				}
				if modelPart != "" {
					normalized, _ := util.NormalizeGeminiThinkingModel(modelPart)
					// Only handle locally when we have a provider; otherwise fall back to proxy
					if providers := util.GetProviderName(normalized); len(providers) > 0 {
						geminiV1Beta1Handler(c)
						return
					}
				}
			}
		}
		// Non-POST or no local provider available -> proxy upstream
		proxyHandler(c)
	})
}

// registerProviderAliases registers /api/provider/{provider}/... routes
// These allow Amp CLI to route requests like:
//
//	/api/provider/openai/v1/chat/completions
//	/api/provider/anthropic/v1/messages
//	/api/provider/google/v1beta/models
func (m *AmpModule) registerProviderAliases(engine *gin.Engine, baseHandler *handlers.BaseAPIHandler, auth gin.HandlerFunc) {
	// Create handler instances for different providers
	openaiHandlers := openai.NewOpenAIAPIHandler(baseHandler)
	geminiHandlers := gemini.NewGeminiAPIHandler(baseHandler)
	claudeCodeHandlers := claude.NewClaudeCodeAPIHandler(baseHandler)
	openaiResponsesHandlers := openai.NewOpenAIResponsesAPIHandler(baseHandler)

	// Create fallback handler wrapper that forwards to ampcode.com when provider not found
	// Uses m.getProxy() for hot-reload support (proxy can be updated at runtime)
	// Also includes model mapping support for routing unavailable models to alternatives
	fallbackHandler := NewFallbackHandlerWithMapper(func() *httputil.ReverseProxy {
		return m.getProxy()
	}, m.modelMapper)

	// Provider-specific routes under /api/provider/:provider
	ampProviders := engine.Group("/api/provider")
	if auth != nil {
		ampProviders.Use(auth)
	}

	provider := ampProviders.Group("/:provider")

	// Dynamic models handler - routes to appropriate provider based on path parameter
	ampModelsHandler := func(c *gin.Context) {
		providerName := strings.ToLower(c.Param("provider"))

		switch providerName {
		case "anthropic":
			claudeCodeHandlers.ClaudeModels(c)
		case "google":
			geminiHandlers.GeminiModels(c)
		default:
			// Default to OpenAI-compatible (works for openai, groq, cerebras, etc.)
			openaiHandlers.OpenAIModels(c)
		}
	}

	// Root-level routes (for providers that omit /v1, like groq/cerebras)
	// Wrap handlers with fallback logic to forward to ampcode.com when provider not found
	provider.GET("/models", ampModelsHandler) // Models endpoint doesn't need fallback (no body to check)
	provider.POST("/chat/completions", fallbackHandler.WrapHandler(openaiHandlers.ChatCompletions))
	provider.POST("/completions", fallbackHandler.WrapHandler(openaiHandlers.Completions))
	provider.POST("/responses", fallbackHandler.WrapHandler(openaiResponsesHandlers.Responses))

	// /v1 routes (OpenAI/Claude-compatible endpoints)
	v1Amp := provider.Group("/v1")
	{
		v1Amp.GET("/models", ampModelsHandler) // Models endpoint doesn't need fallback

		// OpenAI-compatible endpoints with fallback
		v1Amp.POST("/chat/completions", fallbackHandler.WrapHandler(openaiHandlers.ChatCompletions))
		v1Amp.POST("/completions", fallbackHandler.WrapHandler(openaiHandlers.Completions))
		v1Amp.POST("/responses", fallbackHandler.WrapHandler(openaiResponsesHandlers.Responses))

		// Claude/Anthropic-compatible endpoints with fallback
		v1Amp.POST("/messages", fallbackHandler.WrapHandler(claudeCodeHandlers.ClaudeMessages))
		v1Amp.POST("/messages/count_tokens", fallbackHandler.WrapHandler(claudeCodeHandlers.ClaudeCountTokens))
	}

	// /v1beta routes (Gemini native API)
	// Note: Gemini handler extracts model from URL path, so fallback logic needs special handling
	v1betaAmp := provider.Group("/v1beta")
	{
		v1betaAmp.GET("/models", geminiHandlers.GeminiModels)
		v1betaAmp.POST("/models/:action", fallbackHandler.WrapHandler(geminiHandlers.GeminiHandler))
		v1betaAmp.GET("/models/:action", geminiHandlers.GeminiGetHandler)
	}
}