feat(jmespath): add abstract syntax tree definition

packages/jmespath/src/ast.ts

@@ -0,0 +1,299 @@
+import type { JSONValue } from '@aws-lambda-powertools/commons/types';
+import type { Node } from './types.js';
+
+/**
+ * AST node representing a comparator expression.
+ *
+ * A comparator expression is a binary expression that compares two values.
+ *
+ * @param name The name of the comparator
+ * @param first The left-hand side of the comparator
+ * @param second The right-hand side of the comparator
+ */
+const comparator = (name: string, first: Node, second: Node): Node => ({
+  type: 'comparator',
+  children: [first, second],
+  value: name,
+});
+
+/**
+ * AST node representing the current node.
+ *
+ * The current node is a reference to the current value being processed.
+ * In JMESPath, the current node is represented by the `@` symbol.
+ */
+const currentNode = (): Node => ({
+  type: 'current',
+  children: [],
+});
+
+/**
+ * AST node representing an expression reference.
+ *
+ * An expression reference is a reference to another expression.
+ * In JMESPath, an expression reference is represented by the `&` symbol.
+ *
+ * @param expression The expression to reference
+ */
+const expref = (expression: Node): Node => ({
+  type: 'expref',
+  children: [expression],
+});
+
+/**
+ * AST node representing a function expression.
+ *
+ * A function expression is a reference to a function and its arguments.
+ * The JMESPath specification defines a set of built-in functions that can
+ * be used in expressions like `length(@)`, `map(@, &foo)`, etc.
+ *
+ * Custom functions can be added by extending the `Functions` class.
+ *
+ * @param name The name of the function
+ * @param args The arguments to the function
+ */
+const functionExpression = (name: string, args: Node[]): Node => ({
+  type: 'function_expression',
+  children: args,
+  value: name,
+});
+
+/**
+ * AST node representing a field reference.
+ *
+ * A field reference is a reference to a field in an object.
+ */
+const field = (name: JSONValue): Node => ({
+  type: 'field',
+  children: [],
+  value: name,
+});
+
+/**
+ * AST node representing a filter projection.
+ *
+ * A filter projection is a binary expression that filters the left-hand side
+ * based on the right-hand side.
+ *
+ * In JMESPath, a filter projection is represented by the `[]` operator.
+ * For example, `people[?age > 18]` filters the `people` array based on the
+ * `age` field.
+ *
+ * @param left The left-hand side of the filter projection
+ * @param right The right-hand side of the filter projection
+ * @param comparator The comparator to use for the filter
+ */
+const filterProjection = (left: Node, right: Node, comparator: Node): Node => ({
+  type: 'filter_projection',
+  children: [left, right, comparator],
+});
+
+/**
+ * AST node representing a flatten expression.
+ *
+ * A flatten expression is a unary expression that flattens an array of arrays
+ * into a single array.
+ *
+ * In JMESPath, a flatten expression is represented by the `[]` operator.
+ * For example, `people[].name` flattens the `people` array and returns the
+ * `name` field of each object in the array.
+ *
+ * @param node The node to flatten
+ */
+const flatten = (node: Node): Node => ({
+  type: 'flatten',
+  children: [node],
+});
+
+/**
+ * AST node representing an identity expression.
+ */
+const identity = (): Node => ({ type: 'identity', children: [] });
+
+/**
+ * AST node representing an index reference.
+ *
+ * An index reference is a reference to an index in an array.
+ * For example, `people[0]` references the first element in the `people` array.
+ *
+ * @param index The index to reference
+ */
+const index = (index: JSONValue): Node => ({
+  type: 'index',
+  value: index,
+  children: [],
+});
+
+/**
+ * AST node representing an index expression.
+ *
+ * An index expression holds the index and the children of the expression.
+ *
+ * @param children The children of the index expression
+ */
+const indexExpression = (children: Node[]): Node => ({
+  type: 'index_expression',
+  children: children,
+});
+
+/**
+ * AST node representing a key-value pair.
+ *
+ * @param keyName The name of the key
+ * @param node The value of the key
+ */
+const keyValPair = (keyName: JSONValue, node: Node): Node => ({
+  type: 'key_val_pair',
+  children: [node],
+  value: keyName,
+});
+
+/**
+ * AST node representing a literal value.
+ *
+ * A literal value is a value that is not a reference to another node.
+ *
+ * @param literalValue The value of the literal
+ */
+const literal = (literalValue: JSONValue): Node => ({
+  type: 'literal',
+  value: literalValue,
+  children: [],
+});
+
+/**
+ * AST node representing a multi-select object.
+ *
+ * A multi-select object is a reference to multiple nodes in an object.
+ *
+ * @param nodes
+ */
+const multiSelectObject = (nodes: Node[]): Node => ({
+  type: 'multi_select_object',
+  children: nodes,
+});
+
+/**
+ * AST node representing a multi-select list.
+ *
+ * @param nodes
+ */
+const multiSelectList = (nodes: Node[]): Node => ({
+  type: 'multi_select_list',
+  children: nodes,
+});
+
+/**
+ * AST node representing an or expression.
+ *
+ * @param left The left-hand side of the or expression
+ * @param right The right-hand side of the or expression
+ */
+const orExpression = (left: Node, right: Node): Node => ({
+  type: 'or_expression',
+  children: [left, right],
+});
+
+/**
+ * AST node representing an and expression.
+ *
+ * @param left The left-hand side of the and expression
+ * @param right The right-hand side of the and expression
+ */
+const andExpression = (left: Node, right: Node): Node => ({
+  type: 'and_expression',
+  children: [left, right],
+});
+
+/**
+ * AST node representing a not expression.
+ *
+ * @param left The left-hand side of the not expression
+ * @param right The right-hand side of the not expression
+ */
+const notExpression = (expr: Node): Node => ({
+  type: 'not_expression',
+  children: [expr],
+});
+
+/**
+ * AST node representing a pipe expression.
+ *
+ * @param left The left-hand side of the pipe expression
+ * @param right The right-hand side of the pipe expression
+ */
+const pipe = (left: Node, right: Node): Node => ({
+  type: 'pipe',
+  children: [left, right],
+});
+
+/**
+ * AST node representing a projection.
+ *
+ * @param left The left-hand side of the projection
+ * @param right The right-hand side of the projection
+ */
+const projection = (left: Node, right: Node): Node => ({
+  type: 'projection',
+  children: [left, right],
+});
+
+/**
+ * AST node representing a subexpression.
+ *
+ * @param children The children of the subexpression
+ */
+const subexpression = (children: Node[]): Node => ({
+  type: 'subexpression',
+  children: children,
+});
+
+/**
+ * AST node representing a slice.
+ *
+ * A slice is a reference to a range of values in an array.
+ *
+ * @param start The start of the slice
+ * @param end The end of the slice
+ * @param step The step of the slice
+ */
+const slice = (start: JSONValue, end: JSONValue, step: JSONValue): Node => ({
+  type: 'slice',
+  children: [start as Node, end as Node, step as Node],
+});
+
+/**
+ * AST node representing a value projection.
+ *
+ * @param left The left-hand side of the value projection
+ * @param right The right-hand side of the value projection
+ */
+const valueProjection = (left: Node, right: Node): Node => ({
+  type: 'value_projection',
+  children: [left, right],
+});
+
+export {
+  andExpression,
+  comparator,
+  currentNode,
+  expref,
+  field,
+  filterProjection,
+  flatten,
+  functionExpression,
+  identity,
+  index,
+  indexExpression,
+  keyValPair,
+  literal,
+  multiSelectObject,
+  multiSelectList,
+  notExpression,
+  orExpression,
+  pipe,
+  projection,
+  slice,
+  subexpression,
+  valueProjection,
+};