konduktor/go/internal/extension/routing.go

package extension

import (
	"context"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	"github.com/konduktor/konduktor/internal/logging"
	"github.com/konduktor/konduktor/internal/proxy"
)

// RoutingExtension handles request routing based on patterns
type RoutingExtension struct {
	BaseExtension
	exactRoutes  map[string]RouteConfig
	regexRoutes  []*regexRoute
	defaultRoute *RouteConfig
	staticDir    string
}

// RouteConfig holds configuration for a route
type RouteConfig struct {
	ProxyPass       string
	Root            string
	IndexFile       string
	Return          string
	ContentType     string
	Headers         []string
	CacheControl    string
	SPAFallback     bool
	ExcludePatterns []string
	Timeout         float64
}

type regexRoute struct {
	pattern       *regexp.Regexp
	config        RouteConfig
	caseSensitive bool
	originalExpr  string
}

// NewRoutingExtension creates a new routing extension
func NewRoutingExtension(config map[string]interface{}, logger *logging.Logger) (Extension, error) {
	ext := &RoutingExtension{
		BaseExtension: NewBaseExtension("routing", 50, logger), // Middle priority
		exactRoutes:   make(map[string]RouteConfig),
		regexRoutes:   make([]*regexRoute, 0),
		staticDir:     "./static",
	}

	logger.Debug("Routing extension config", "config", config)

	// Parse regex_locations from config
	if locations, ok := config["regex_locations"].(map[string]interface{}); ok {
		logger.Debug("Found regex_locations", "count", len(locations))
		for pattern, routeCfg := range locations {
			logger.Debug("Adding route", "pattern", pattern)
			if rc, ok := routeCfg.(map[string]interface{}); ok {
				ext.addRoute(pattern, parseRouteConfig(rc))
			}
		}
	} else {
		logger.Warn("No regex_locations found in config", "config_keys", getKeys(config))
	}

	// Parse static_dir if provided
	if staticDir, ok := config["static_dir"].(string); ok {
		ext.staticDir = staticDir
	}

	return ext, nil
}

func parseRouteConfig(cfg map[string]interface{}) RouteConfig {
	rc := RouteConfig{
		IndexFile: "index.html",
	}

	if v, ok := cfg["proxy_pass"].(string); ok {
		rc.ProxyPass = v
	}
	if v, ok := cfg["root"].(string); ok {
		rc.Root = v
	}
	if v, ok := cfg["index_file"].(string); ok {
		rc.IndexFile = v
	}
	if v, ok := cfg["return"].(string); ok {
		rc.Return = v
	}
	if v, ok := cfg["content_type"].(string); ok {
		rc.ContentType = v
	}
	if v, ok := cfg["cache_control"].(string); ok {
		rc.CacheControl = v
	}
	if v, ok := cfg["spa_fallback"].(bool); ok {
		rc.SPAFallback = v
	}
	if v, ok := cfg["timeout"].(float64); ok {
		rc.Timeout = v
	}

	// Parse headers
	if headers, ok := cfg["headers"].([]interface{}); ok {
		for _, h := range headers {
			if header, ok := h.(string); ok {
				rc.Headers = append(rc.Headers, header)
			}
		}
	}

	// Parse exclude_patterns
	if patterns, ok := cfg["exclude_patterns"].([]interface{}); ok {
		for _, p := range patterns {
			if pattern, ok := p.(string); ok {
				rc.ExcludePatterns = append(rc.ExcludePatterns, pattern)
			}
		}
	}

	return rc
}

func (e *RoutingExtension) addRoute(pattern string, config RouteConfig) {
	switch {
	case pattern == "__default__":
		e.defaultRoute = &config

	case strings.HasPrefix(pattern, "="):
		// Exact match
		path := strings.TrimPrefix(pattern, "=")
		e.exactRoutes[path] = config

	case strings.HasPrefix(pattern, "~*"):
		// Case-insensitive regex
		expr := strings.TrimPrefix(pattern, "~*")
		re, err := regexp.Compile("(?i)" + expr)
		if err != nil {
			e.logger.Error("Invalid regex pattern", "pattern", pattern, "error", err)
			return
		}
		e.regexRoutes = append(e.regexRoutes, &regexRoute{
			pattern:       re,
			config:        config,
			caseSensitive: false,
			originalExpr:  expr,
		})

	case strings.HasPrefix(pattern, "~"):
		// Case-sensitive regex
		expr := strings.TrimPrefix(pattern, "~")
		re, err := regexp.Compile(expr)
		if err != nil {
			e.logger.Error("Invalid regex pattern", "pattern", pattern, "error", err)
			return
		}
		e.regexRoutes = append(e.regexRoutes, &regexRoute{
			pattern:       re,
			config:        config,
			caseSensitive: true,
			originalExpr:  expr,
		})
	}
}

// ProcessRequest handles the request routing
func (e *RoutingExtension) ProcessRequest(ctx context.Context, w http.ResponseWriter, r *http.Request) (bool, error) {
	path := r.URL.Path

	// 1. Check exact routes (ignore request path for proxy)
	if config, ok := e.exactRoutes[path]; ok {
		return e.handleRoute(w, r, config, nil, true)
	}

	// 2. Check regex routes
	for _, route := range e.regexRoutes {
		match := route.pattern.FindStringSubmatch(path)
		if match != nil {
			params := make(map[string]string)
			names := route.pattern.SubexpNames()
			for i, name := range names {
				if i > 0 && name != "" && i < len(match) {
					params[name] = match[i]
				}
			}
			return e.handleRoute(w, r, route.config, params, false)
		}
	}

	// 3. Check default route
	if e.defaultRoute != nil {
		return e.handleRoute(w, r, *e.defaultRoute, nil, false)
	}

	return false, nil
}

func (e *RoutingExtension) handleRoute(w http.ResponseWriter, r *http.Request, config RouteConfig, params map[string]string, exactMatch bool) (bool, error) {
	// Handle "return" directive
	if config.Return != "" {
		return e.handleReturn(w, config)
	}

	// Handle proxy_pass
	if config.ProxyPass != "" {
		return e.handleProxy(w, r, config, params, exactMatch)
	}

	// Handle static files with root
	if config.Root != "" {
		return e.handleStatic(w, r, config)
	}

	// Handle SPA fallback
	if config.SPAFallback {
		return e.handleSPAFallback(w, r, config)
	}

	return false, nil
}

func (e *RoutingExtension) handleReturn(w http.ResponseWriter, config RouteConfig) (bool, error) {
	parts := strings.SplitN(config.Return, " ", 2)
	statusCode := 200
	body := "OK"

	if len(parts) >= 1 {
		switch parts[0] {
		case "200":
			statusCode = 200
		case "201":
			statusCode = 201
		case "301":
			statusCode = 301
		case "302":
			statusCode = 302
		case "400":
			statusCode = 400
		case "404":
			statusCode = 404
		case "500":
			statusCode = 500
		}
	}
	if len(parts) >= 2 {
		body = parts[1]
	}

	contentType := "text/plain"
	if config.ContentType != "" {
		contentType = config.ContentType
	}

	w.Header().Set("Content-Type", contentType)
	w.WriteHeader(statusCode)
	w.Write([]byte(body))
	return true, nil
}

func (e *RoutingExtension) handleProxy(w http.ResponseWriter, r *http.Request, config RouteConfig, params map[string]string, exactMatch bool) (bool, error) {
	target := config.ProxyPass

	// Check if target URL contains parameter placeholders
	hasParams := strings.Contains(target, "{") && strings.Contains(target, "}")

	// Substitute params in target URL
	for key, value := range params {
		target = strings.ReplaceAll(target, "{"+key+"}", value)
	}

	// Create proxy config
	// IgnoreRequestPath=true when:
	// - exact match route (=/path)
	// - target URL had parameter substitutions (the target path is fully specified)
	proxyConfig := &proxy.Config{
		Target:            target,
		Headers:           make(map[string]string),
		IgnoreRequestPath: exactMatch || hasParams,
	}

	// Set timeout if specified
	if config.Timeout > 0 {
		proxyConfig.Timeout = time.Duration(config.Timeout * float64(time.Second))
	}

	// Parse headers
	clientIP := getClientIP(r)
	for _, header := range config.Headers {
		parts := strings.SplitN(header, ": ", 2)
		if len(parts) == 2 {
			value := parts[1]
			// Substitute params
			for key, pValue := range params {
				value = strings.ReplaceAll(value, "{"+key+"}", pValue)
			}
			// Substitute special variables
			value = strings.ReplaceAll(value, "$remote_addr", clientIP)
			proxyConfig.Headers[parts[0]] = value
		}
	}

	p, err := proxy.New(proxyConfig, e.logger)
	if err != nil {
		e.logger.Error("Failed to create proxy", "target", target, "error", err)
		http.Error(w, "Bad Gateway", http.StatusBadGateway)
		return true, nil
	}

	p.ProxyRequest(w, r, params)
	return true, nil
}

func (e *RoutingExtension) handleStatic(w http.ResponseWriter, r *http.Request, config RouteConfig) (bool, error) {
	path := r.URL.Path

	// Handle index file for root or directory paths
	if path == "/" || strings.HasSuffix(path, "/") {
		path = "/" + config.IndexFile
	}

	// Get absolute path for root dir
	absRoot, err := filepath.Abs(config.Root)
	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return true, nil
	}

	filePath := filepath.Join(absRoot, filepath.Clean("/"+path))
	cleanPath := filepath.Clean(filePath)

	// Prevent directory traversal
	if !strings.HasPrefix(cleanPath+string(filepath.Separator), absRoot+string(filepath.Separator)) {
		http.Error(w, "Forbidden", http.StatusForbidden)
		return true, nil
	}

	// Check if file exists
	if _, err := os.Stat(filePath); os.IsNotExist(err) {
		return false, nil // Let other handlers try
	}

	// Set cache control header
	if config.CacheControl != "" {
		w.Header().Set("Cache-Control", config.CacheControl)
	}

	// Set custom headers
	for _, header := range config.Headers {
		parts := strings.SplitN(header, ": ", 2)
		if len(parts) == 2 {
			w.Header().Set(parts[0], parts[1])
		}
	}

	http.ServeFile(w, r, filePath)
	return true, nil
}

func (e *RoutingExtension) handleSPAFallback(w http.ResponseWriter, r *http.Request, config RouteConfig) (bool, error) {
	path := r.URL.Path

	// Check exclude patterns
	for _, pattern := range config.ExcludePatterns {
		if strings.HasPrefix(path, pattern) {
			return false, nil
		}
	}

	root := config.Root
	if root == "" {
		root = e.staticDir
	}

	indexFile := config.IndexFile
	if indexFile == "" {
		indexFile = "index.html"
	}

	filePath := filepath.Join(root, indexFile)
	if _, err := os.Stat(filePath); os.IsNotExist(err) {
		return false, nil
	}

	http.ServeFile(w, r, filePath)
	return true, nil
}

func getClientIP(r *http.Request) string {
	// Check X-Forwarded-For header first
	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
		parts := strings.Split(xff, ",")
		return strings.TrimSpace(parts[0])
	}

	// Check X-Real-IP header
	if xri := r.Header.Get("X-Real-IP"); xri != "" {
		return xri
	}

	// Fall back to RemoteAddr
	ip := r.RemoteAddr
	if idx := strings.LastIndex(ip, ":"); idx != -1 {
		ip = ip[:idx]
	}
	return ip
}

// GetMetrics returns routing metrics
func (e *RoutingExtension) GetMetrics() map[string]interface{} {
	return map[string]interface{}{
		"exact_routes": len(e.exactRoutes),
		"regex_routes": len(e.regexRoutes),
		"has_default":  e.defaultRoute != nil,
	}
}

func getKeys(m map[string]interface{}) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	return keys
}