implement runtime cache for Crunchyroll.browse()

app/src/main/java/org/mosad/teapod/parser/crunchyroll/Crunchyroll.kt

@@ -67,7 +67,7 @@ object Crunchyroll {
     private var signature = ""
     private var keyPairID = ""
 
-    private val browsingCache = arrayListOf<Item>()
+    private val browsingCache = hashMapOf<String, BrowseResult>()
 
     /**
      * Load the pai token, see:
@@ -286,18 +286,29 @@ object Crunchyroll {
             parameters.add("categories" to categories.joinToString(",") { it.str })
         }
 
-        val browseResult: BrowseResult = try {
-            requestGet(browseEndpoint, parameters)
-        }catch (ex: SerializationException) {
-            Log.e(TAG, "SerializationException in browse().", ex)
-            NoneBrowseResult
+        // fetch result if not already cached
+        if (browsingCache.contains(parameters.toString())) {
+            Log.d(TAG, "browse result cached: $parameters")
+        } else {
+            Log.d(TAG, "browse result not cached, fetching: $parameters")
+            val browseResult: BrowseResult = try {
+                requestGet(browseEndpoint, parameters)
+            }catch (ex: SerializationException) {
+                Log.e(TAG, "SerializationException in browse().", ex)
+                NoneBrowseResult
+            }
+
+            // if the cache has more than 100 entries clear it, so it doesn't become a memory problem
+            // Note: this value is totally guessed and should be replaced by a properly researched value
+            if (browsingCache.size > 100) {
+                browsingCache.clear()
+            }
+
+            // add results to cache
+            browsingCache[parameters.toString()] = browseResult
         }
 
-        // add results to cache TODO improve
-        browsingCache.clear()
-        browsingCache.addAll(browseResult.items)
-
-        return browseResult
+        return browsingCache[parameters.toString()] ?: NoneBrowseResult
     }
 
     /**