save work

Author: cherylEnkidu

google-cloud-firestore/src/main/java/com/google/cloud/firestore/Pipeline.java

@@ -41,6 +41,7 @@
 import com.google.cloud.firestore.pipeline.stages.AddFields;
 import com.google.cloud.firestore.pipeline.stages.Aggregate;
 import com.google.cloud.firestore.pipeline.stages.AggregateOptions;
+import com.google.cloud.firestore.pipeline.stages.DefineStage;
 import com.google.cloud.firestore.pipeline.stages.Distinct;
 import com.google.cloud.firestore.pipeline.stages.FindNearest;
 import com.google.cloud.firestore.pipeline.stages.FindNearestOptions;
@@ -55,6 +56,7 @@
 import com.google.cloud.firestore.pipeline.stages.Sort;
 import com.google.cloud.firestore.pipeline.stages.Stage;
 import com.google.cloud.firestore.pipeline.stages.StageUtils;
+import com.google.cloud.firestore.pipeline.stages.SubcollectionSource;
 import com.google.cloud.firestore.pipeline.stages.Union;
 import com.google.cloud.firestore.pipeline.stages.Unnest;
 import com.google.cloud.firestore.pipeline.stages.UnnestOptions;
@@ -261,6 +263,51 @@ public Pipeline addFields(Selectable field, Selectable... additionalFields) {
                     .toArray(new Selectable[0]))));
   }
 
+  /**
+   * Initializes a pipeline scoped to a subcollection.
+   *
+   * @param path The path of the subcollection.
+   * @return A new {@code Pipeline} instance scoped to the subcollection.
+   */
+  @BetaApi
+  public static Pipeline subcollection(String path) {
+    return new Pipeline(null, new SubcollectionSource(path));
+  }
+
+  /**
+   * Adds new fields or redefines existing fields in the output documents by
+   * evaluating given expressions.
+   *
+   * @param expressions The expressions to define or redefine fields using
+   *                    {@link AliasedExpression}.
+   * @return A new Pipeline object with this stage appended to the stage list.
+   */
+  @BetaApi
+  public Pipeline define(Selectable... expressions) {
+    return append(
+        new DefineStage(PipelineUtils.selectablesToMap(expressions)));
+  }
+
+  /**
+   * Converts the pipeline into an array expression.
+   *
+   * @return A new {@link Expression} representing the pipeline as an array.
+   */
+  @BetaApi
+  public Expression toArrayExpression() {
+    return Expression.rawExpression("array", Expression.pipeline(this));
+  }
+
+  /**
+   * Converts the pipeline into a scalar expression.
+   *
+   * @return A new {@link Expression} representing the pipeline as a scalar.
+   */
+  @BetaApi
+  public Expression toScalarExpression() {
+    return Expression.rawExpression("scalar", Expression.pipeline(this));
+  }
+
   /**
    * Remove fields from outputs of previous stages.
    *

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/Expression.java

@@ -24,6 +24,7 @@
 import com.google.cloud.firestore.FieldPath;
 import com.google.cloud.firestore.FieldValue;
 import com.google.cloud.firestore.GeoPoint;
+import com.google.cloud.firestore.Pipeline;
 import com.google.cloud.firestore.VectorValue;
 import com.google.common.collect.ImmutableList;
 import com.google.firestore.v1.Value;
@@ -227,6 +228,7 @@ public static Expression currentTimestamp() {
     return new FunctionExpression("current_timestamp", ImmutableList.of());
   }
 
+
   /**
    * Creates an expression that returns a default value if an expression evaluates to an absent
    * value.
@@ -4796,4 +4798,86 @@ public final Expression collectionId() {
   public final Expression type() {
     return type(this);
   }
+
+  /**
+   * Creates an expression that represents the current document being processed.
+   *
+   * @return An {@link Expression} representing the current document.
+   */
+  @BetaApi
+  public static Expression currentDocument() {
+    return new FunctionExpression("current_document", ImmutableList.of());
+  }
+
+  /**
+   * Creates an expression that retrieves the value of a variable bound via
+   * pipeline definitions.
+   *
+   * @param name The name of the variable to retrieve.
+   * @return An {@link Expression} representing the variable's value.
+   */
+  @BetaApi
+  public static Expression variable(String name) {
+    return new Variable(name);
+  }
+
+  /**
+   * Accesses a field/property of the expression (useful when the expression
+   * evaluates to a Map or Document).
+   *
+   * @param expression The expression evaluating to a map/document.
+   * @param key        The key of the field to access.
+   * @return An {@link Expression} representing the value of the field.
+   */
+  @BetaApi
+  public static Expression field(Expression expression, String key) {
+    return new FunctionExpression("field", ImmutableList.of(expression, constant(key)));
+  }
+
+  /**
+   * Creates an expression that evaluates to the provided pipeline.
+   *
+   * @param pipeline The pipeline to use as an expression.
+   * @return A new {@link Expression} representing the pipeline value.
+   */
+  @InternalApi
+  public static Expression pipeline(Pipeline pipeline) {
+    return new PipelineValueExpression(pipeline);
+  }
+
+  /**
+   * Internal expression representing a variable reference.
+   *
+   * <p>
+   * This evaluates to the value of a variable defined in a pipeline context.
+   */
+  static class Variable extends Expression {
+    private final String name;
+
+    Variable(String name) {
+      this.name = name;
+    }
+
+    @Override
+    public Value toProto() {
+      return Value.newBuilder().setVariableReferenceValue(name).build();
+    }
+  }
+
+  /**
+   * Internal expression representing a pipeline value.
+   */
+  static class PipelineValueExpression extends Expression {
+    private final Pipeline pipeline;
+
+    PipelineValueExpression(Pipeline pipeline) {
+      this.pipeline = pipeline;
+    }
+
+    @Override
+    public Value toProto() {
+      return pipeline.toProtoValue();
+    }
+  }
+
 }