Change Indentation

script

// Editor - Change Indentation

// Starts with either the selected text (extended to include the entire line(s)) or uses the entire draft's contents if there is no selection.

// Determines the shortest whitespace indentation (tabs or spaces), and then offers a choice to change the indentation.

// If both tabs and spaces are mixed, this script does its best to convert to one or the other, but doesn't handle all cases. 

// Defaults to offering options for 2-space, 4-space, or tab indentation. if you want other options, change the defaultOpts list below. "Spaces" entries must start with a number. 

(() => {

  const defaultOpts = ["Tabs", "2 spaces", "4 spaces"];

  // Return the selected lines if any
  // Otherwise, select and return entire draft contents
  const getSelectedLinesOrAllText = () => {
    const
      r = editor.getSelectedRange(),
      rl = editor.getSelectedLineRange(),
      s = r[1] > 0 
        // if there's a selection - get the selected line text
        ? editor.getTextInRange(...rl)
        : draft.content,
      // start new selection at beginning of draft if nothing was selected
      // otherwise, start selection at the beginning of selected line
      p = r[1] === 0 ? 0 : rl[0];
    // update select range
    editor.setSelectedRange(p, s.length); 
    return s;
  };

  const
    // Get current state
    lines = getSelectedLinesOrAllText().split("\n"),
    range = editor.getSelectedRange(),
    indents = lines.reduce((ls, l) => 
      (m = l.match(/^\s+/)) ? ls.concat(m) : ls, []),
    mixed = (indents.some(s => s.search("\t") !== -1)
      && indents.some(s => s.search(" ") !== -1)),
    tabs = indents.every(s => s.search(" ") === -1),
    spaces = indents.every(s => s.search("\t") === -1),
    // get the minimum length of indents with spaces
    spacesLen = tabs ? 0 
      : indents.filter(s => s.search(" ") !== -1)
        .map(s => s.length)
        .reduce((m, l) => Math.min(m, l)),
    curIndent = tabs ? "\t" : " ".repeat(spacesLen),
    curIndentName = mixed ? "Mixed tabs and spaces" 
      : (tabs ? "Tabs" : spacesLen + " spaces"),

    // Set up prompt with buttons to change indentation
    // Exclude the current indentation if its one of the defaults
    opts = defaultOpts.filter(s => s != curIndentName),
    p = opts.reduce((p, b) => {p.addButton(b);return p},
      Object.assign(Prompt.create(), 
        {title:"Switch Indentation", message:"Current: " + curIndentName}));

  if (!p.show()){
    context.cancel();
    return;
  }

  const
    newIndent = (p.buttonPressed === "Tabs") ? "\t"
      : " ".repeat(parseInt(p.buttonPressed, 10)),
    // pre-processing: in mixed tab/spaces scenario, replace each
    // tab with spaces so subsequent processing works as expected
    preProcessed = !mixed ? lines // not mixed, just return the lines
      : lines.map(l => l.replace(/^\t+/,
        m => curIndent.repeat(m.length))),
    // replace all leading whitespace with new indentation
    newText = preProcessed.map(l => l.replace(/^\s+/, 
      m => newIndent.repeat(m.length/curIndent.length))).join("\n");

  editor.setSelectedText(newText);
  editor.setSelectedRange(range[0], newText.length);

})();