Start work on expression builder for updates

lib/updateExpressionBuilder.ts

@@ -0,0 +1,34 @@
+export type ExpressionBuilderResult = {
+  UpdateExpression: string;
+  ExpressionAttributeNames: any;
+  ExpressionAttributeValues: any;
+};
+export const updateExpressionBuilder = (item: any): ExpressionBuilderResult => ({
+  UpdateExpression: internalUpdateBuilder(item),
+  ExpressionAttributeNames: internalNameBuilder(item),
+  ExpressionAttributeValues: internalValueBuilder(item),
+});
+
+const internalUpdateBuilder = (item: any): string => {
+  const itemKeys = Object.keys(item);
+
+  return `SET ${itemKeys.map((k, index) => `#field_${index} = :value_${index}`).join(', ')}`;
+};
+
+const internalNameBuilder = (item: any): any => {
+  const itemKeys = Object.keys(item);
+
+  return itemKeys.reduce(
+    (accumulator, k, index) => ({ ...accumulator, [`#field_${index}`]: k }),
+    {},
+  );
+};
+
+const internalValueBuilder = (item: any): any => {
+  const itemKeys = Object.keys(item);
+  // itemKeys.reduce((accumulator, k, index) => ({ ...accumulator, [`:value${index}`]: item[k] }), {})
+  return itemKeys.reduce(
+    (accumulator, k, index) => ({ ...accumulator, [`:value_${index}`]: item[k] }),
+    {},
+  );
+};

test/updateExpressionBuilder.unit.test.ts

@@ -0,0 +1,182 @@
+import { updateExpressionBuilder } from '../lib/updateExpressionBuilder';
+
+describe('When building an update expression', () => {
+  describe('with primitive-only properties', () => {
+    it('should return an expression builder result', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).not.toBeEmpty();
+      expect(result.ExpressionAttributeNames).toBeObject();
+      expect(result.ExpressionAttributeValues).toBeObject();
+    });
+
+    it('should add "#field_[index]" for each property', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain('#field_0');
+      expect(result.UpdateExpression).toContain('#field_1');
+      expect(result.UpdateExpression).toContain('#field_2');
+    });
+
+    it('should add ":value_[index]" for each property', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain(':value_0');
+      expect(result.UpdateExpression).toContain(':value_1');
+      expect(result.UpdateExpression).toContain(':value_2');
+    });
+
+    it('should correctly build Attribute Names', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true };
+
+      // ACT
+      const { ExpressionAttributeNames } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeNames['#field_0']).toEqual('name');
+      expect(ExpressionAttributeNames['#field_1']).toEqual('age');
+      expect(ExpressionAttributeNames['#field_2']).toEqual('isCool');
+    });
+
+    it('should correctly build Attribute Values', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true };
+
+      // ACT
+      const { ExpressionAttributeValues } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeValues[':value_0']).toEqual(item.name);
+      expect(ExpressionAttributeValues[':value_1']).toEqual(item.age);
+      expect(ExpressionAttributeValues[':value_2']).toEqual(item.isCool);
+    });
+  });
+
+  describe('with an array property', () => {
+    it('should add "#field_[index]" for the array', () => {
+      // ARRANGE
+      const item = {
+        name: 'Francisco',
+        age: 31,
+        isCool: true,
+        pursuits: ['philosophy', 'physics', 'mining'],
+      };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain('#field_3');
+    });
+
+    it('should add ":value_[index]" for the array', () => {
+      // ARRANGE
+      const item = {
+        name: 'Francisco',
+        age: 31,
+        isCool: true,
+        pursuits: ['philosophy', 'physics', 'mining'],
+      };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain(':value_3');
+    });
+
+    it('should correctly build Attribute Names', () => {
+      // ARRANGE
+      const item = {
+        name: 'Francisco',
+        age: 31,
+        isCool: true,
+        pursuits: ['philosophy', 'physics', 'mining'],
+      };
+
+      // ACT
+      const { ExpressionAttributeNames } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeNames['#field_3']).toEqual('pursuits');
+    });
+
+    it('should correctly build Attribute Values', () => {
+      // ARRANGE
+      const item = {
+        name: 'Francisco',
+        age: 31,
+        isCool: true,
+        pursuits: ['philosophy', 'physics', 'mining'],
+      };
+
+      // ACT
+      const { ExpressionAttributeValues } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeValues[':value_3']).toEqual(item.pursuits);
+    });
+  });
+
+  describe('with a map property', () => {
+    it('should add "#field_[index]" for the map', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true, company: { location: 'Argentina' } };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain('#field_3');
+    });
+
+    it('should add ":value_[index]" for the map', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true, company: { location: 'Argentina' } };
+
+      // ACT
+      const result = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(result.UpdateExpression).toContain(':value_3');
+    });
+
+    it('should correctly build Attribute Names', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true, company: { location: 'Argentina' } };
+
+      // ACT
+      const { ExpressionAttributeNames } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeNames['#field_3']).toEqual('company');
+    });
+
+    it('should correctly build Attribute Values', () => {
+      // ARRANGE
+      const item = { name: 'Francisco', age: 31, isCool: true, company: { location: 'Argentina' } };
+
+      // ACT
+      const { ExpressionAttributeValues } = updateExpressionBuilder(item);
+
+      // ASSERT
+      expect(ExpressionAttributeValues[':value_3']).toEqual(item.company);
+    });
+  });
+});