Improved GET requests

- Uses custom HttpClient
- Callback for HTTPS certificate errors
- Major code refactor = cleaner code!
- All response validation is performed in the API now!

lib/api.dart

@@ -165,44 +165,19 @@ class InvenTreeAPI {
 
     print("Connecting to ${apiUrl} -> ${username}:${password}");
 
-    var response = await get("").timeout(Duration(seconds: 10)).catchError((error) {
+    // Request the /api/ endpoint - response is a json object
-
+    var response = await get("");
-      print("Error connecting to server: ${error.toString()}");
-
-      if (error is SocketException) {
-        showServerError(
-            I18N.of(context).connectionRefused,
-            error.toString());
-        return null;
-      } else if (error is TimeoutException) {
-        showTimeoutError(context);
-        return null;
-      } else {
-        // Unknown error type - re-throw
-        throw error;
-      }
-    });
 
+    // Null response means something went horribly wrong!
     if (response == null) {
-      // Null (or error) response: Show dialog and exit
       return false;
     }
 
-    if (response.statusCode != 200) {
-      // Any status code other than 200!
 
-      showStatusCodeError(response.statusCode);
+    print("Response from server: ${response}");
-
-      // TODO: Interpret the error codes and show custom message?
-      return false;
-    }
-
-    var data = json.decode(response.body);
-
-    print("Response from server: $data");
 
     // We expect certain response from the server
-    if (!data.containsKey("server") || !data.containsKey("version") || !data.containsKey("instance")) {
+    if (!response.containsKey("server") || !response.containsKey("version") || !response.containsKey("instance")) {
 
       showServerError(
         "Missing Data",
@@ -213,11 +188,11 @@ class InvenTreeAPI {
     }
 
     // Record server information
-    _version = data["version"];
+    _version = response["version"];
-    instance = data['instance'] ?? '';
+    instance = response['instance'] ?? '';
 
     // Default API version is 1 if not provided
-    _apiVersion = data['apiVersion'] as int ?? 1;
+    _apiVersion = response['apiVersion'] as int ?? 1;
 
     if (_apiVersion < _minApiVersion) {
 
@@ -245,14 +220,7 @@ class InvenTreeAPI {
 
     print("Requesting token from server");
 
-    response = await get(_URL_GET_TOKEN).timeout(Duration(seconds: 10)).catchError((error) {
+    response = await get(_URL_GET_TOKEN);
-
-      print("Error requesting token:");
-      print(error);
-
-      response = null;
-
-    });
 
     if (response == null) {
       showServerError(
@@ -263,13 +231,7 @@ class InvenTreeAPI {
       return false;
     }
 
-    if (response.statusCode != 200) {
+    if (!response.containsKey("token")) {
-      showStatusCodeError(response.statusCode);
-      return false;
-    } else {
-      var data = json.decode(response.body);
-
-      if (!data.containsKey("token")) {
       showServerError(
           I18N.of(OneContext().context).tokenMissing,
           "Access token missing from response"
@@ -279,7 +241,7 @@ class InvenTreeAPI {
     }
 
     // Return the received token
-      _token = data["token"];
+    _token = response["token"];
     print("Received token - $_token");
 
     // Request user role information
@@ -287,7 +249,7 @@ class InvenTreeAPI {
 
     // Ok, probably pretty good...
     return true;
-    };
+
   }
 
   bool disconnectFromServer() {
@@ -348,33 +310,20 @@ class InvenTreeAPI {
     // Note: 2021-02-27 this "roles" feature for the API was just introduced.
     // Any 'older' version of the server allows any API method for any logged in user!
     // We will return immediately, but request the user roles in the background
-    await get(_URL_GET_ROLES).timeout(
-        Duration(seconds: 10)).catchError((error) {
-      print("Error requesting roles:");
-      print(error);
-    }).then((response) {
 
-      print("Response status: ${response.statusCode}");
+    var response = await get(_URL_GET_ROLES);
 
-      if (response.statusCode == 200) {
+    // Null response from server
+    if (response == null) {
+      print("null response requesting user roles");
+      return;
+    }
 
-        // Convert response to JSON representation
+    if (response.containsKey('roles')) {
-
-        try {
-          var data = json.decode(response.body);
-
-          if (data.containsKey('roles')) {
       // Save a local copy of the user roles
-            roles = data['roles'];
+      roles = response['roles'];
     }
   }
-        on FormatException {
-          // Old server has re-directed away from the API
-        }
-      } else {
-      }
-    });
-  }
 
   bool checkPermission(String role, String permission) {
     /*
@@ -454,11 +403,42 @@ class InvenTreeAPI {
     );
   }
 
-  // Perform a GET request
+  HttpClient _client(bool allowBadCert) {
-  Future<http.Response> get(String url, {Map<String, String> params}) async {
+
+    var client = new HttpClient();
+
+    client.badCertificateCallback = ((X509Certificate cert, String host, int port) {
+      // TODO - Introspection of actual certificate?
+
+      if (allowBadCert) {
+        return true;
+      } else {
+        showServerError(
+          I18N.of(OneContext().context).serverCertificateError,
+          "Server HTTPS certificate invalid"
+        );
+        return false;
+      }
+
+      return allowBadCert;
+    });
+
+    // Set the connection timeout
+    client.connectionTimeout = Duration(seconds: 30);
+
+    return client;
+  }
+
+  /**
+   * Perform a HTTP GET request
+   * Returns a json object (or null if did not complete)
+   */
+  Future<dynamic> get(String url, {Map<String, String> params}) async {
     var _url = makeApiUrl(url);
     var _headers = defaultHeaders();
 
+    print("GET: ${_url}");
+
     // If query parameters are supplied, form a query string
     if (params != null && params.isNotEmpty) {
       String query = '?';
@@ -475,7 +455,80 @@ class InvenTreeAPI {
 
     print("GET: " + _url);
 
-    return http.get(_url, headers: _headers);
+    var client = _client(true);
+
+    print("Created client");
+
+    HttpClientRequest request = await client.getUrl(Uri.parse(_url));
+
+    // Set headers
+    request.headers.set(HttpHeaders.contentTypeHeader, 'application/json');
+    if (profile != null) {
+      request.headers.set(
+          HttpHeaders.authorizationHeader,
+          _authorizationHeader(profile.username, profile.password)
+      );
+    }
+
+    print("Created request: ${request.uri}");
+
+    HttpClientResponse response = await request.close()
+    .timeout(Duration(seconds: 30))
+    .catchError((error) {
+      print("GET request returned error");
+      print("URL: ${_url}");
+      print("Error: ${error.toString()}");
+
+      var ctx = OneContext().context;
+
+      if (error is SocketException) {
+        showServerError(
+            I18N.of(ctx).connectionRefused,
+            error.toString()
+        );
+      } else if (error is TimeoutException) {
+        showTimeoutError(ctx);
+      } else {
+        showServerError(
+            I18N.of(ctx).serverError,
+            error.toString()
+        );
+      }
+
+      return null;
+    });
+
+    // A null response means something has gone wrong...
+    if (response == null) {
+      print("null response from GET ${_url}");
+      return null;
+    }
+
+    // Check the status code of the response
+    if (response.statusCode != 200) {
+      showStatusCodeError(response.statusCode);
+      return null;
+    }
+
+    // Convert the body of the response to a JSON object
+    String body = await response.transform(utf8.decoder).join();
+
+    try {
+      var data = json.decode(body);
+
+      return data;
+
+    } on FormatException {
+
+      print("JSON format exception!");
+      print("${body}");
+
+      showServerError(
+        "Format Exception",
+        "JSON data format exception:\n${body}"
+      );
+      return null;
+    }
   }
 
   Map<String, String> defaultHeaders() {
@@ -496,6 +549,7 @@ class InvenTreeAPI {
 
   String _authorizationHeader(String username, String password) {
     if (_token.isNotEmpty) {
+      print("Using TOKEN: ${_token}");
       return "Token $_token";
     } else {
       return "Basic " + base64Encode(utf8.encode('${username}:${password}'));

lib/inventree/model.dart

@@ -166,39 +166,13 @@ class InvenTreeModel {
    */
   Future<bool> reload(BuildContext context) async {
 
-    var response = await api.get(url, params: defaultGetFilters())
+    var response = await api.get(url, params: defaultGetFilters());
-      .timeout(Duration(seconds: 10))
-      .catchError((e) {
-
-          if (e is SocketException) {
-            showServerError(
-              I18N.of(context).connectionRefused,
-              e.toString()
-            );
-          }
-          else if (e is TimeoutException) {
-            showTimeoutError(context);
-          } else {
-            // Re-throw the error
-            throw e;
-          }
-
-          return null;
-    });
     
     if (response == null) {
       return false;
     }
 
-    if (response.statusCode != 200) {
+    jsondata = response;
-      showStatusCodeError(response.statusCode);
-      print("Error retrieving data");
-      return false;
-    }
-
-    final Map<String, dynamic> data = json.decode(response.body);
-
-    jsondata = data;
 
     return true;
   }
@@ -265,34 +239,13 @@ class InvenTreeModel {
 
     print("GET: $addr ${params.toString()}");
 
-    var response = await api.get(addr, params: params)
+    var response = await api.get(addr, params: params);
-        .timeout(Duration(seconds: 10))
-        .catchError((e) {
-
-          if (e is SocketException) {
-            showServerError(I18N.of(context).connectionRefused, e.toString());
-          }
-          else if (e is TimeoutException) {
-            showTimeoutError(context);
-          } else {
-            // Re-throw the error
-            throw e;
-          }
-          return null;
-      });
 
     if (response == null) {
       return null;
     }
 
-    if (response.statusCode != 200) {
+    return createFromJson(response);
-      showStatusCodeError(response.statusCode);
-      return null;
-    }
-
-    final data = json.decode(response.body);
-
-    return createFromJson(data);
   }
 
   Future<InvenTreeModel> create(BuildContext context, Map<String, dynamic> data) async {
@@ -353,41 +306,21 @@ class InvenTreeModel {
     params["limit"] = "${limit}";
     params["offset"] = "${offset}";
 
-    var response = await api.get(URL, params: params)
+    var response = await api.get(URL, params: params);
-        .timeout(Duration(seconds: 10))
-        .catchError((error) {
-      if (error is SocketException) {
-        showServerError(
-            I18N
-                .of(OneContext().context)
-                .connectionRefused,
-            error.toString()
-        );
-      }
-
-      return null;
-    });
 
     if (response == null) {
       return null;
     }
 
-    if (response.statusCode != 200) {
-      showStatusCodeError(response.statusCode);
-      return null;
-    }
-
     // Construct the response
     InvenTreePageResponse page = new InvenTreePageResponse();
 
-    final data = json.decode(response.body);
+    if (response.containsKey("count") && response.containsKey("results")) {
-
+       page.count = response["count"] as int;
-    if (data.containsKey("count") && data.containsKey("results")) {
-       page.count = data["count"] as int;
 
        page.results = [];
 
-       for (var result in data["results"]) {
+       for (var result in response["results"]) {
          page.addResult(createFromJson(result));
        }
 
@@ -417,50 +350,20 @@ class InvenTreeModel {
 
     print("LIST: $URL ${params.toString()}");
 
-    // TODO - Add "timeout"
+    var response = await api.get(URL, params: params);
-    // TODO - Add error catching
-
-    var response = await api.get(URL, params:params)
-      .timeout(Duration(seconds: 10))
-      .catchError((e) {
-
-        if (e is SocketException) {
-          showServerError(
-              I18N.of(context).connectionRefused,
-              e.toString()
-          );
-        }
-        else if (e is TimeoutException) {
-          showTimeoutError(context);
-        } else {
-          // Re-throw the error
-          throw e;
-        }
-
-        return null;
-    });
-
-    if (response == null) {
-      return null;
-    }
 
     // A list of "InvenTreeModel" items
     List<InvenTreeModel> results = new List<InvenTreeModel>();
 
-    if (response.statusCode != 200) {
+    if (response == null) {
-      showStatusCodeError(response.statusCode);
-
-      // Return empty list
       return results;
     }
 
-    final data = json.decode(response.body);
-
     // TODO - handle possible error cases:
     // - No data receieved
     // - Data is not a list of maps
 
-    for (var d in data) {
+    for (var d in response) {
 
       // Create a new object (of the current class type
       InvenTreeModel obj = createFromJson(d);