core: Add context hinting for new feeds

RSS-Bridge currently has to guess the queried context from the data
provided by the user. This, however, can cause issues for bridges
that have multiple contexts with conflicting parameters (i.e. none).

This commit adds context hinting to queries via '&context=<context>'
which can be omitted in which case the context is determined as before.

lib/BridgeAbstract.php

@@ -194,6 +194,11 @@ protected function setInputs(array $inputs, $queriedContext){
 	 */
 	public function setDatas(array $inputs){
 
+		if(isset($inputs['context'])) { // Context hinting (optional)
+			$this->queriedContext = $inputs['context'];
+			unset($inputs['context']);
+		}
+
 		if(empty(static::PARAMETERS)) {
 
 			if(!empty($inputs)) {
@@ -218,8 +223,11 @@ function($i){ return $i['name']; }, // Just display parameter names
 			);
 		}
 
-		// Guess the paramter context from input data
-		$this->queriedContext = $validator->getQueriedContext($inputs, static::PARAMETERS);
+		// Guess the context from input data
+		if(empty($this->queriedContext)) {
+			$this->queriedContext = $validator->getQueriedContext($inputs, static::PARAMETERS);
+		}
+
 		if(is_null($this->queriedContext)) {
 			returnClientError('Required parameter(s) missing');
 		} elseif($this->queriedContext === false) {

lib/BridgeCard.php

@@ -48,13 +48,19 @@ private static function buildFormatButtons($formats) {
 	 * @param bool $isHttps If disabled, adds a warning to the form
 	 * @return string The form header
 	 */
-	private static function getFormHeader($bridgeName, $isHttps = false) {
+	private static function getFormHeader($bridgeName, $isHttps = false, $parameterName = '') {
 		$form = <<<EOD
 			<form method="GET" action="?">
 				<input type="hidden" name="action" value="display" />
 				<input type="hidden" name="bridge" value="{$bridgeName}" />
 EOD;
 
+		if(!empty($parameterName)) {
+			$form .= <<<EOD
+				<input type="hidden" name="context" value="{$parameterName}" />
+EOD;
+		}
+
 		if(!$isHttps) {
 			$form .= '<div class="secure-warning">Warning :
 This bridge is not fetching its content through a secure connection</div>';
@@ -80,7 +86,7 @@ private static function getForm($bridgeName,
 	$isHttps = false,
 	$parameterName = '',
 	$parameters = array()) {
-		$form = self::getFormHeader($bridgeName, $isHttps);
+		$form = self::getFormHeader($bridgeName, $isHttps, $parameterName);
 
 		if(count($parameters) > 0) {
 

lib/ParameterValidator.php

@@ -214,6 +214,7 @@ public function getQueriedContext($data, $parameters){
 
 		switch(array_sum($queriedContexts)) {
 		case 0: // Found no match, is there a context without parameters?
+			if(isset($data['context'])) return $data['context'];
 			foreach($queriedContexts as $context => $queried) {
 				if(is_null($queried)) {
 					return $context;