Improved styling and comments

main.go

@@ -1,3 +1,11 @@
+/*
+This application ensures the required environment variables are set
+Then it uses the included countersql package to test a connection to the database
+It then caches the number of unique visits in memory by querying the database
+Finally, it sets up a web server with the endpoint http://localhost:8080/
+For each unique source IP address which makes a GET request to this endpoint,
+the count of unique visitors is incremented by 1, both in the database and in memory cache.
+*/
 package main
 
 import (
@@ -12,8 +20,8 @@ import (
 )
 
 var (
-	database     countersql.Configuration
-	uniqueVisits int
+	database     countersql.Configuration // Configuration information required to connect to the database, using the countersql package
+	uniqueVisits int                      // In memory cache of unique visitors
 )
 
 // Application Startup
@@ -59,7 +67,6 @@ func init() {
 
 // HTTP Routing
 func main() {
-
 	// API Handlers
 	http.HandleFunc("/", countHandler)
 
@@ -68,10 +75,14 @@ func main() {
 
 }
 
+// HTTP handler function
 func countHandler(w http.ResponseWriter, r *http.Request) {
 	if r.Method == "GET" {
+		// CORS header change required
 		w.Header().Set("Access-Control-Allow-Origin", "*")
 		w.Write([]byte(strconv.Itoa(uniqueVisits)))
+
+		// Connect to database
 		dbConn, err := database.Connect()
 		if err != nil {
 			log.Printf("failed to connect to database: %v", err)
@@ -80,16 +91,17 @@ func countHandler(w http.ResponseWriter, r *http.Request) {
 		}
 		defer dbConn.DB.Close()
 
+		// We now get the source IP address of this request
 		var ipAddress string
-
+		// Check if we're behind a reverse proxy / WAF
 		if len(r.Header.Get("X-Forwarded-For")) > 0 {
 			ipAddress = r.Header.Get("X-Forwarded-For")
 		} else {
 			ipAddress = r.RemoteAddr
 		}
-
 		ipAddress = strings.Split(ipAddress, ":")[0]
 
+		// Check if this is the first time this IP address has visited
 		returnVisitor, err := dbConn.HasIPVisited(ipAddress)
 		if err != nil {
 			log.Printf("failed to determine if this is a return visitor, no data is being logged: %v", err)
@@ -97,9 +109,11 @@ func countHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		if returnVisitor {
+			// Log their visit
 			err = dbConn.IncrementVisitor(ipAddress)
 			log.Printf("return visitor from %s", ipAddress)
 		} else {
+			// Insert a new visitor row in the database
 			err = dbConn.AddVisitor(ipAddress)
 			uniqueVisits++
 			log.Printf("new visitor from %s", ipAddress)
@@ -110,6 +124,7 @@ func countHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 	} else {
+		// Needs to be GET method
 		w.WriteHeader(http.StatusMethodNotAllowed)
 	}
 }