FMWK-820 Add usage examples in readme

README.md

@@ -36,18 +36,61 @@ When modifying the grammar file you will need to re-generate the ANTLR sources b
 
 ## Usage examples
 
-### Filter expression
+### Parsing DSL expression
+
 ```java
-String input = "$.intBin1 > 100";
-Expression expression = ConditionTranslator.translate(input);
+import com.aerospike.dsl.api.DSLParser;
+import com.aerospike.dsl.impl.DSLParserImpl;
+
+// String DSL expression
+String input = "$.intBin1 > 100 and $.intBin2 > 100";
+// Instantiating DSL parser
+DSLParser parser = new DSLParserImpl();
+// Providing list of existing secondary indexes
+// At most only one index will be chosen based on its namespace and binValuesRatio (cardinality)
+// If cardinality of multiple indexes is the same, the index is chosen alphabetically
+List<Index> indexes = List.of(
+        Index.builder().namespace("namespace").bin("intBin1").indexType(IndexType.NUMERIC).binValuesRatio(1).build(),
+        Index.builder().namespace("namespace2").bin("intBin2").indexType(IndexType.NUMERIC).binValuesRatio(1).build()
+);
+// Parsing DSL expression
+ParsedExpression expression = parser.parseExpression(
+        // We provide expression context (it may also contain placeholders values as an optional argument)
+        ExpressionContext.of(input), 
+        // And optional index context with the required namespace and a list of existing indexes
+        IndexContext.of("namespace", indexes)
+);
 ```
-Will return the following expression:
+
+### Getting filter expression
+
 ```java
-Exp.build(
+Expression actualExp = Exp.build(
+        // Getting filter expression
+        expression.getResult().getExp()
+);
+
+// Only one filter expression because the first part has secondary index filter
+Expression expectedExp = Exp.build(
     Exp.gt(
-        Exp.intBin("intBin1"),
+        Exp.intBin("intBin2"),
         Exp.val(100))
 );
+
+assertEquals(actualExp, expectedExp);
+```
+
+### Getting secondary index filter
+
+```java
+// Getting secondary index filter
+// Only one secondary index filter can be created at most
+Filter actualFilter = expression.getResult().getFilter();
+
+// The second part has filter expression
+Filter expectedFilter = Filter.range("intBin1", 101, Long.MAX_VALUE);
+
+assertEquals(actualFilter, expectedFilter);
 ```
 
 ## License