[BACKEND] Initialize Go backend structure and dependencies (#23)

server/middleware/cors.go

@@ -0,0 +1,100 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// CORSConfig holds the configuration for the CORS middleware
+type CORSConfig struct {
+	AllowedOrigins   []string
+	AllowedMethods   []string
+	AllowedHeaders   []string
+	AllowCredentials bool
+	MaxAge           int
+}
+
+// DefaultCORSConfig returns the default CORS configuration
+func DefaultCORSConfig() *CORSConfig {
+	return &CORSConfig{
+		AllowedOrigins:   []string{"*"},
+		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS", "PATCH"},
+		AllowedHeaders:   []string{"Content-Type", "Authorization", "X-Requested-With", "Accept", "Origin"},
+		AllowCredentials: false,
+		MaxAge:           86400, // 24 hours
+	}
+}
+
+// CORS returns a Gin middleware handler for CORS (Cross-Origin Resource Sharing)
+func CORS() gin.HandlerFunc {
+	return CORSWithConfig(DefaultCORSConfig())
+}
+
+// CORSWithConfig returns a Gin middleware handler for CORS with custom configuration
+func CORSWithConfig(config *CORSConfig) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		origin := c.GetHeader("Origin")
+		
+		// Check if the origin is allowed
+		if len(config.AllowedOrigins) > 0 && config.AllowedOrigins[0] != "*" {
+			allowed := false
+			for _, allowedOrigin := range config.AllowedOrigins {
+				if origin == allowedOrigin {
+					allowed = true
+					break
+				}
+			}
+			if !allowed {
+				c.AbortWithStatusJSON(403, gin.H{
+					"error": "origin not allowed",
+				})
+				return
+			}
+		}
+		
+		// Set CORS headers
+		if len(config.AllowedOrigins) > 0 {
+			if config.AllowedOrigins[0] == "*" {
+				c.Header("Access-Control-Allow-Origin", "*")
+			} else {
+				c.Header("Access-Control-Allow-Origin", origin)
+			}
+		}
+		
+		c.Header("Access-Control-Allow-Methods", joinStringSlice(config.AllowedMethods, ", "))
+		c.Header("Access-Control-Allow-Headers", joinStringSlice(config.AllowedHeaders, ", "))
+		
+		if config.AllowCredentials {
+			c.Header("Access-Control-Allow-Credentials", "true")
+		}
+		
+		c.Header("Access-Control-Max-Age", stringFromInt(config.MaxAge))
+		
+		// Handle preflight requests
+		if c.Request.Method == "OPTIONS" {
+			c.AbortWithStatus(204)
+			return
+		}
+		
+		c.Next()
+	}
+}
+
+// Helper function to join a slice of strings
+func joinStringSlice(slice []string, sep string) string {
+	if len(slice) == 0 {
+		return ""
+	}
+	result := slice[0]
+	for i := 1; i < len(slice); i++ {
+		result += sep + slice[i]
+	}
+	return result
+}
+
+// Helper function to convert int to string
+func stringFromInt(n int) string {
+	if n == 0 {
+		return ""
+	}
+	return string(rune('0'+n%10)) + stringFromInt(n/10)
+}