@flowscripter/mpeg-sdl-parser/src/ast/factory/getExpressionStatement.ts

ISO/IEC 14496-34 Syntactic Description Language (MPEG SDL) parser implemented in TypeScript

import { Text } from "@codemirror/state";
import type { TreeCursor } from "@lezer/common";
import { InternalParseError } from "../../ParseError";
import {
  getChildNodesAndTokens,
  isAbstractNode,
} from "../../util/nodeFactoryUtils";
import type { AbstractExpression } from "../node/AbstractExpression";
import { NodeKind } from "../node/enum/node_kind";
import type { Identifier } from "../node/Identifier";
import type { Token } from "../token/Token";
import type { NumberLiteral } from "../node/NumberLiteral";
import { ExpressionStatement } from "../node/ExpressionStatement";

export function getExpressionStatement(
  cursor: TreeCursor,
  text: Text,
): ExpressionStatement {
  const childNodesAndTokens = getChildNodesAndTokens(cursor, text);

  let expression: AbstractExpression | Identifier | NumberLiteral | undefined;
  let semicolonPunctuator: Token | undefined;

  for (const childNodeOrToken of childNodesAndTokens) {
    if (isAbstractNode(childNodeOrToken)) {
      if (childNodeOrToken.nodeKind === NodeKind.EXPRESSION) {
        expression = childNodeOrToken as AbstractExpression;
      } else {
        throw new InternalParseError(
          `Unexpected node kind: ${NodeKind[childNodeOrToken.nodeKind]}`,
        );
      }
    } else {
      if (childNodeOrToken.text === ";") {
        semicolonPunctuator = childNodeOrToken;
      } else {
        throw new InternalParseError(
          `Unexpected token: ${childNodeOrToken.text}`,
        );
      }
    }
  }

  if (expression === undefined) {
    throw new InternalParseError("Expected argument expression to be defined");
  }
  if (semicolonPunctuator === undefined) {
    throw new InternalParseError(
      "Expected argument semicolonPunctuator to be defined",
    );
  }
  return new ExpressionStatement(
    expression,
    semicolonPunctuator,
  );
}