feat(http_server): add solution for exercise 31_http_server (#50)

Author: sidharth-chauhan

internal/exercises/solutions/31_http_server/http_server.go

@@ -0,0 +1,47 @@
+package http_server
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"strings"
+)
+
+// helloHandler handles requests to paths beginning with /hello/.
+// It extracts the first path segment after /hello/ and responds
+// with "Hello, {name}!\n". If no name is provided, it returns
+// a 400 Bad Request response.
+func helloHandler(w http.ResponseWriter, r *http.Request) {
+	name := strings.TrimPrefix(r.URL.Path, "/hello/")
+
+	// Only take the first segment if multiple are present (e.g., /hello/a/b → "a").
+	if i := strings.IndexByte(name, '/'); i >= 0 {
+		name = name[:i]
+	}
+
+	// Handle the case where no name is given (e.g., /hello/).
+	if name == "" {
+		http.Error(w, "name required", http.StatusBadRequest)
+		return
+	}
+
+	// Respond with plain text greeting.
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	fmt.Fprintf(w, "Hello, %s!\n", name)
+}
+
+// init registers the /hello/ route when the package is loaded.
+// This ensures the handler is available even when tests start
+// their own server without calling StartServer.
+func init() {
+	http.HandleFunc("/hello/", helloHandler)
+}
+
+// StartServer starts an HTTP server on port :8080 using the
+// default multiplexer. Any server error is logged instead of
+// being silently ignored.
+func StartServer() {
+	if err := http.ListenAndServe(":8080", nil); err != nil {
+		log.Printf("http server stopped: %v", err)
+	}
+}