OR Queries.

Add Filter.Java. Remove core/Filter.Java.
Add CompositeFilter.java.
Make the Filter class abstract.
Purely formatting change. (ran googleJavaFormat).
Added UnqualifiedFieldFilter, and `where` API.
Update core/Query.java to be "aware" of composite filters.
Fix the logic for `matches(doc)` for CompositeFilters.
Fix remaining usages.
Update RemoteSerializer.java.
Add TODO for bundles.
Add the other filter APIs.
integrate with indexing.
Respect the limit when evaluating multiple dnf terms.
Remove UnqualifiedFieldFilter. Move validation to the right place.
Don't impose limit on sub-filter queries.
Enforce limit constraint for queries with more than 1 DNF term.
Add the parsed filter to the query.

Author: ehsannas

firebase-firestore/src/main/java/com/google/firebase/firestore/DocumentReference.java

@@ -84,7 +84,7 @@ static DocumentReference forPath(ResourcePath path, FirebaseFirestore firestore)
     return new DocumentReference(DocumentKey.fromPath(path), firestore);
   }
 
-  DocumentKey getKey() {
+  public DocumentKey getKey() {
     return key;
   }
 

firebase-firestore/src/main/java/com/google/firebase/firestore/Filter.java

@@ -0,0 +1,132 @@
+package com.google.firebase.firestore;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import com.google.firebase.firestore.core.CompositeFilter;
+import com.google.firebase.firestore.core.FieldFilter;
+import com.google.firebase.firestore.core.Query;
+import com.google.firebase.firestore.model.Document;
+import java.util.Arrays;
+
+public abstract class Filter {
+  @NonNull
+  public static Filter equalTo(@NonNull String field, @Nullable Object value) {
+    return equalTo(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter equalTo(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(fieldPath.getInternalPath(), FieldFilter.Operator.EQUAL, value);
+  }
+
+  @NonNull
+  public static Filter notEqualTo(@NonNull String field, @Nullable Object value) {
+    return notEqualTo(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter notEqualTo(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(fieldPath.getInternalPath(), FieldFilter.Operator.NOT_EQUAL, value);
+  }
+
+  @NonNull
+  public static Filter greaterThan(@NonNull String field, @Nullable Object value) {
+    return greaterThan(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter greaterThan(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(
+        fieldPath.getInternalPath(), FieldFilter.Operator.GREATER_THAN, value);
+  }
+
+  @NonNull
+  public static Filter greaterThanOrEqualTo(@NonNull String field, @Nullable Object value) {
+    return greaterThanOrEqualTo(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter greaterThanOrEqualTo(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(
+        fieldPath.getInternalPath(), FieldFilter.Operator.GREATER_THAN_OR_EQUAL, value);
+  }
+
+  @NonNull
+  public static Filter lessThan(@NonNull String field, @Nullable Object value) {
+    return lessThan(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter lessThan(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(fieldPath.getInternalPath(), FieldFilter.Operator.LESS_THAN, value);
+  }
+
+  @NonNull
+  public static Filter lessThanOrEqualTo(@NonNull String field, @Nullable Object value) {
+    return lessThanOrEqualTo(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter lessThanOrEqualTo(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(
+        fieldPath.getInternalPath(), FieldFilter.Operator.LESS_THAN_OR_EQUAL, value);
+  }
+
+  @NonNull
+  public static Filter arrayContains(@NonNull String field, @Nullable Object value) {
+    return arrayContains(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter arrayContains(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(
+        fieldPath.getInternalPath(), FieldFilter.Operator.ARRAY_CONTAINS, value);
+  }
+
+  @NonNull
+  public static Filter arrayContainsAny(@NonNull String field, @Nullable Object value) {
+    return arrayContainsAny(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter arrayContainsAny(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(
+        fieldPath.getInternalPath(), FieldFilter.Operator.ARRAY_CONTAINS_ANY, value);
+  }
+
+  @NonNull
+  public static Filter in(@NonNull String field, @Nullable Object value) {
+    return in(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter in(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(fieldPath.getInternalPath(), FieldFilter.Operator.IN, value);
+  }
+
+  @NonNull
+  public static Filter notIn(@NonNull String field, @Nullable Object value) {
+    return notIn(FieldPath.fromDotSeparatedPath(field), value);
+  }
+
+  @NonNull
+  public static Filter notIn(@NonNull FieldPath fieldPath, @Nullable Object value) {
+    return FieldFilter.create(fieldPath.getInternalPath(), FieldFilter.Operator.NOT_IN, value);
+  }
+
+  @NonNull
+  public static Filter or(Filter... filters) {
+    return new CompositeFilter(Arrays.asList(filters), /*isAnd*/ false);
+  }
+
+  @NonNull
+  public static Filter and(Filter... filters) {
+    return new CompositeFilter(Arrays.asList(filters), /*isAnd*/ true);
+  }
+
+  public abstract Query apply(Query query, FirebaseFirestore firestore);
+
+  public abstract boolean matches(Document doc);
+
+  public abstract String getCanonicalId();
+}

firebase-firestore/src/main/java/com/google/firebase/firestore/FirebaseFirestore.java

@@ -761,11 +761,11 @@ FirestoreClient getClient() {
     return client;
   }
 
-  DatabaseId getDatabaseId() {
+  public DatabaseId getDatabaseId() {
     return databaseId;
   }
 
-  UserDataReader getUserDataReader() {
+  public UserDataReader getUserDataReader() {
     return userDataReader;
   }