Function programNodeIsSimilar

core/edit/lazy/deterministic.ts:254–296

(
  programNode: Parser.SyntaxNode,
  otherNode: Parser.SyntaxNode,
)

}

function programNodeIsSimilar(
  programNode: Parser.SyntaxNode,
  otherNode: Parser.SyntaxNode,
): boolean {
  // Check purely based on whether they are similar strings
  const newLines = programNode.text.split("\n");
  const oldLines = otherNode.text.split("\n");

  // Check that there is a line that matches the start of the old range
  const oldFirstLine = oldLines[0].trim();
  let matchForOldFirstLine = -1;
  for (let i = 0; i < newLines.length; i++) {
    if (newLines[i].trim() === oldFirstLine) {
      matchForOldFirstLine = i;
      break;
    }
  }

  if (matchForOldFirstLine < 0) {
    return false;
  }

  // Check that the last lines match each other
  const oldLastLine = oldLines[oldLines.length - 1].trim();
  const newLastLine = newLines[newLines.length - 1].trim();
  if (oldLastLine !== newLastLine) {
    return false;
  }

  // Check that the number of matching lines is at least half of the shorter length
  let matchingLines = 0;
  for (let i = 0; i < Math.min(newLines.length, oldLines.length); i++) {
    if (oldLines[i].trim() === newLines[matchForOldFirstLine + i].trim()) {
      matchingLines += 1;
    }
  }

  if (matchingLines >= Math.max(newLines.length, oldLines.length) / 2) {
    return true;
  }

  return false;
}

/**
 * Determine whether two nodes are similar