Add WebGLBridge for WebGL build support, CORS, file input fallback (closes #57)

unity-client/Assets/Scripts/Services/WebGLBridge.cs

@@ -0,0 +1,106 @@
+using System;
+using System.Runtime.InteropServices;
+using UnityEngine;
+
+namespace CommanderAILab.Services
+{
+    /// <summary>
+    /// WebGL-specific bridge: reads server URL from URL query params,
+    /// provides JS interop for file input (camera fallback on WebGL),
+    /// handles browser security restrictions (HTTPS in prod),
+    /// and loading screen progress.
+    /// </summary>
+    public class WebGLBridge : MonoBehaviour
+    {
+        public static WebGLBridge Instance { get; private set; }
+
+#if UNITY_WEBGL && !UNITY_EDITOR
+        [DllImport("__Internal")] private static extern string GetURLParam(string key);
+        [DllImport("__Internal")] private static extern void OpenFileDialog(string accept, string callbackObject, string callbackMethod);
+        [DllImport("__Internal")] private static extern void SetLoadingProgress(float progress);
+#else
+        private static string GetURLParam(string key) => "";
+        private static void OpenFileDialog(string accept, string obj, string method) { }
+        private static void SetLoadingProgress(float progress) { }
+#endif
+
+        private Action<byte[]> _fileCallback;
+
+        private void Awake()
+        {
+            if (Instance != null) { Destroy(gameObject); return; }
+            Instance = this;
+            DontDestroyOnLoad(gameObject);
+        }
+
+        /// <summary>
+        /// Read server URL from ?server= query param.
+        /// Falls back to http://localhost:8080 if not set.
+        /// </summary>
+        public string GetServerUrl()
+        {
+            string url = "";
+#if UNITY_WEBGL && !UNITY_EDITOR
+            try { url = GetURLParam("server"); } catch { }
+#endif
+            if (string.IsNullOrEmpty(url)) url = "http://localhost:8080";
+
+            // Browser security: enforce HTTPS in production
+            if (IsProductionBuild() && url.StartsWith("http://"))
+            {
+                Debug.LogWarning("[WebGLBridge] Production build should use HTTPS. Upgrading URL.");
+                url = url.Replace("http://", "https://");
+            }
+            return url;
+        }
+
+        /// <summary>
+        /// Open a file picker dialog (WebGL camera fallback).
+        /// On WebGL, WebCamTexture is not available so we use
+        /// an HTML file input element instead.
+        /// </summary>
+        public void PickImageFile(Action<byte[]> callback)
+        {
+            _fileCallback = callback;
+#if UNITY_WEBGL && !UNITY_EDITOR
+            OpenFileDialog("image/*", gameObject.name, "OnFileSelected");
+#else
+            Debug.LogWarning("[WebGLBridge] File picker is only available in WebGL builds.");
+#endif
+        }
+
+        /// <summary>Called from JavaScript when file is selected.</summary>
+        public void OnFileSelected(string base64Data)
+        {
+            if (string.IsNullOrEmpty(base64Data)) return;
+            try
+            {
+                byte[] data = Convert.FromBase64String(base64Data);
+                _fileCallback?.Invoke(data);
+            }
+            catch (Exception e)
+            {
+                Debug.LogError($"[WebGLBridge] File parse error: {e.Message}");
+            }
+        }
+
+        /// <summary>Update the loading screen progress bar (0–1).</summary>
+        public void UpdateLoadingProgress(float progress)
+        {
+#if UNITY_WEBGL && !UNITY_EDITOR
+            SetLoadingProgress(Mathf.Clamp01(progress));
+#endif
+        }
+
+        private bool IsProductionBuild()
+        {
+#if UNITY_WEBGL && !UNITY_EDITOR
+            // Check if running on localhost
+            string host = Application.absoluteURL;
+            return !host.Contains("localhost") && !host.Contains("127.0.0.1");
+#else
+            return false;
+#endif
+        }
+    }
+}