Add the lookup in pairs list operation to do alist search

Change-Id: Id3473ad588ebd31d5f85082c77c7380256081d02

appinventor/buildserver/build.xml

@@ -20,6 +20,7 @@
 
   <target name="tests"
           depends="BuildServerTests,YailGeneratorTests">
+
   </target>
 
   <!-- =====================================================================

appinventor/buildserver/src/com/google/appinventor/buildserver/resources/runtime.scm

@@ -1547,11 +1547,12 @@ Block name               Kawa implementation
 - add items to list       (yail-list-add-to-list! yail-list . items)
 - insert into list        (yail-list-insert-item! yail-list index item)
 - is in list?             (yail-list-member? object yail-list)
-- position  in list       (yail-list-index item list)
+- position in list       (yail-list-index item list)
 - for each                (foreach variable bodyform yail-list) [macro] [in control drawer]
 - pick random item        (yail-list-pick-random yail-list)
 - is list?                (yail-list? object)
 - is empty?               (yail-list-empty? yail-list)
+- lookup in pairs         (yail-alist-lookup key yail-list-of-pairs default)
 
 Lists in App Inventor are implemented as "Yail lists".  A Yail list is
 a Java pair whose car is a distinguished token
@@ -1919,6 +1920,44 @@ list, use the make-yail-list constructor with no arguments.
                               (inexact->exact (floor high)))))
 
 
+;;; For now, we'll represent tables as lists of pairs.
+;;; Note that these are Yail lists, and the implementation
+;;; must take account of that.   In this implementation, keys and
+;;; values can be any blocks objects.
+
+;;; Yail-alist lookup looks up the key in a list of pairs and returns resulting match.
+;;; It returns the default if the key is not in the table.
+;;; Note that we can't simply use kawa assoc here, because we are
+;;; dealing with Yail lists
+
+;;; TODO(hal):  Implement dictionaries and
+;;; integrate these with get JSON from web services.  Probably need to
+;;; make new DICTIONARY data type analogous to YailList.  Think about
+;;; any component operations that need to create dictionaries and whether we
+;;; we need a Java class similar to the YailList Java class.  Also think about
+;;; how to convert dictionaries to strings and how this interacts with printing
+;;; JSON objects and whether jsonutils.decode.
+
+(define (yail-alist-lookup key yail-list-of-pairs default)
+  (android-log 
+   (format #f "List alist lookup key is  ~A and table is ~A" key yail-list-of-pairs))
+  (let loop ((pairs-to-check (yail-list-contents yail-list-of-pairs)))
+    (cond ((null? pairs-to-check) default)
+	  ((not (pair-ok? (car pairs-to-check)))
+	   (signal-runtime-error
+	    (format #f "Lookup in pairs: the list ~A is not a well-formed list of pairs"
+		    (get-display-representation yail-list-of-pairs))
+	    "Invalid list of pairs"))
+	  ((equal? key (car (yail-list-contents (car pairs-to-check))))
+	   (cadr (yail-list-contents (car pairs-to-check))))
+	  (else (loop (cdr pairs-to-check))))))
+
+
+(define (pair-ok? candidate-pair)
+  (and (yail-list? candidate-pair)
+       (= (length (yail-list-contents candidate-pair)) 2)))
+      
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;; End of List implementation
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

appinventor/buildserver/tests/com/google/appinventor/buildserver/YailEvalTest.java

@@ -736,6 +736,57 @@ public class YailEvalTest extends TestCase {
     }
   }
 
+  /* a-list lookup */
+  public void testAListLookup1() throws Throwable {
+    String schemeInputString = "(begin " + 
+      "(define pair1 (make-yail-list \"a\" \"b\")) " +
+      "(define pair2 (make-yail-list \"aa\" \"bb\")) " +
+      "(define pairs (make-yail-list pair1 pair2)) " +
+      "(yail-alist-lookup \"aa\" pairs \"nothing\") " +
+      ")";
+    String schemeResultString = "bb";
+    assertEquals(schemeResultString, scheme.eval(schemeInputString).toString());
+  }
+
+  public void testAListLookup2() throws Throwable {
+    String schemeInputString = "(begin " + 
+      "(define pair1 (make-yail-list \"a\" \"b\")) " +
+      "(define pair2 (make-yail-list (make-yail-list 1 2) \"bb\")) " +
+      "(define pairs (make-yail-list pair1 pair2)) " +
+      "(yail-alist-lookup (make-yail-list 1  (+ 1 1)) pairs \"nothing\") " +
+      ")";
+    String schemeResultString = "bb";
+    assertEquals(schemeResultString, scheme.eval(schemeInputString).toString());
+  }
+
+  public void testAListLookup3() throws Throwable {
+    String schemeInputString = "(begin " + 
+      "(define pair1 (make-yail-list \"a\" \"b\")) " +
+      "(define pair2 (make-yail-list (make-yail-list 1 2) \"bb\")) " +
+      "(define pairs (make-yail-list pair1 pair2)) " +
+      "(yail-alist-lookup (make-yail-list \"foo\"  (+ 1 1)) pairs \"nothing\") " +
+      ")";
+    String schemeResultString = "nothing";
+    assertEquals(schemeResultString, scheme.eval(schemeInputString).toString());
+  }
+
+  public void testAListLookup4() throws Throwable {
+    /* check that this signals a runtime error for a bad pair  */
+    String schemeInnerInputString = "(begin " + 
+      "(define pair1 (make-yail-list \"a\" \"b\")) " +
+      "(define pair2 (make-yail-list (make-yail-list 1 2) \"bb\")) " +
+      "(define badpair 100) " +
+      "(define pairs (make-yail-list pair1 pair2 badpair)) " +
+      "(yail-alist-lookup (make-yail-list \"foo\"  (+ 1 1)) pairs \"nothing\") " +
+      ")";
+    String schemeInputString = "(try-catch " +
+          schemeInnerInputString +
+        " (exception com.google.appinventor.components.runtime.errors.YailRuntimeError " +
+        " \"bad pair\" " +
+        "))";
+    assertEquals("bad pair", scheme.eval(thunkify(schemeInputString)).toString());
+  }
+
   public void testListInsertionMiddle() throws Throwable {
     /* test list insertion in middle */
     String schemeInputString = "(begin " +

appinventor/components/src/com/google/appinventor/components/runtime/Web.java

@@ -595,6 +595,9 @@ public class Web extends AndroidNonvisibleComponent implements Component {
   // The object will be sanitized to produce the corresponding Yail data by call-component-method.
   // That mechanism would need to be extended if we ever change JSON decoding to produce
   // dictionaries rather than lists
+  // TOOD(hal): Provide an alternative way to decode JSON objects to dictionaries.  Maybe with 
+  // renaming this JsonTextDecodeWithPairs and making JsonTextDecode the one to use
+  // dictionaries
   public Object JsonTextDecode(String jsonText) {
     try {
       return decodeJsonText(jsonText);

appinventor/components/src/com/google/appinventor/components/runtime/util/JsonUtil.java

@@ -82,6 +82,8 @@ public class JsonUtil {
    * @throws JSONException if an element in jObject cannot be
    * converted properly.
    */
+  // TODO(hal): If we implement dictionaries, we'll need to decode Json
+  // objects to dictionaires instead.
   public static List<Object> getListFromJsonObject(JSONObject jObject) throws JSONException {
     List<Object> returnList = new ArrayList<Object>();
     Iterator<String> keys = jObject.keys();

appinventor/components/src/com/google/appinventor/components/scripts/templates/OUTPUT_FOOTER.txt

@@ -158,6 +158,8 @@
         <BlockGenusMember>list-to-csv-table</BlockGenusMember>
         <BlockGenusMember>list-from-csv-row</BlockGenusMember>
         <BlockGenusMember>list-from-csv-table</BlockGenusMember>
+        <BlockGenusMember>list-lookup-in-pairs</BlockGenusMember>
+
       </BlockDrawer>
 
       <BlockDrawer name="Math" button-color="math">

appinventor/components/src/com/google/appinventor/components/scripts/templates/OUTPUT_HEADER.txt

@@ -2058,6 +2058,35 @@ For multiple screen apps, use close screen with value rather than close screen w
       </LangSpecProperties>
     </BlockGenus>
 
+    <!-- List Lookup in Pairs Block -->
+    <BlockGenus name="list-lookup-in-pairs" decorator="call" kind="function" initlabel="lookup in pairs " color="list">
+      <description>
+        <arg-description n="1" name="key" doc-name="key">The key to look up </arg-description>
+        <arg-description n="2" name="pairs" doc-name="pairs">A list of (key value) pairs</arg-description>
+        <arg-description n="3" name="notFound" 
+                 doc-name="notFound">Value to return if there is no pair with the given key.</arg-description>
+        <text>Returns the value associated with the key in the list of pairs.</text>
+      </description>
+      <BlockConnectors>
+        <BlockConnector label="" connector-kind="plug" connector-type="poly"/>
+        <BlockConnector label="key" connector-kind="socket" connector-type="poly"/>
+        <BlockConnector label="pairs" connector-kind="socket" connector-type="poly"/>
+        <BlockConnector label="notFound" connector-kind="socket" connector-type="poly">
+          <DefaultArg genus-name="text" label="NotFound"/>
+        </BlockConnector>
+      </BlockConnectors>
+      <LangSpecProperties>
+        <LangSpecProperty key="ya-kind" value="primitive"/>
+        <LangSpecProperty key="ya-rep" value="yail-alist-lookup"/>
+        <LangSpecProperty key="type-exclude-1" value="argument"/>
+        <LangSpecProperty key="socket-exclude-1" value="key/argument"/>
+        <LangSpecProperty key="socket-allow-1" value="pairs/value"/>
+        <LangSpecProperty key="socket-allow-2" value="pairs/list"/>
+        <LangSpecProperty key="socket-allow-3" value="notFound/text"/>
+        <LangSpecProperty key="socket-allow-4" value="notFound/text"/>
+      </LangSpecProperties>
+    </BlockGenus>
+
     <!-- Math -->
 
     <!-- Greaterthan Block -->