tune-basic-toolset/src/patch.tool.js

Basic toolset for tune

const fs = require('fs').promises;

// Patch tool to apply custom diffs marked with <<<<<<< ORIGINAL and >>>>>>> UPDATED
// Handles patches with context and applies only the segments between markers.

module.exports = async function patch({ text, filename }, ctx) {
  // Regex to match each patch block
  // Be lenient about the number of conflict marker characters because some
  // environments may trim one or more > or < characters.
  const patchRegex = /<{6,}\s*ORIGINAL[^\n]*\n([\s\S]*?)=+\n([\s\S]*?)>{6,}\s*UPDATED[^\n]*(?:\n|$)/g;
  const patches = [];
  let match;

  // Extract all old/new segments
  while ((match = patchRegex.exec(text)) !== null) {
    const oldPart = match[1].replace(/^\n+|\n+$/g, "");
    const newPart = match[2].replace(/^\n+|\n+$/g, "");
    patches.push({ oldPart, newPart });
  }

  if (patches.length === 0) {
    return "No valid patch segments found";
  }

  let fileContent = await ctx.read(filename);

  for (const { oldPart, newPart } of patches) {
    // Escape regex special chars in oldPart.
    // Do NOT relax all whitespace to \s+; that can swallow preceding newlines.
    // Only normalize line endings so CRLF in patches can match LF in files.
    let escaped = oldPart.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
    escaped = escaped.replace(/\r?\n/g, "\\r?\\n");
    const oldRegex = new RegExp(escaped, "g");

    // Perform replacement using a function to avoid replacement string ambiguities
    fileContent = fileContent.replace(oldRegex, () => newPart);
  }

  await ctx.write(filename, fileContent);
  return "patched";
};