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args/lib/src/usage.dart

Index: args/lib/src/usage.dart
diff --git a/args/lib/src/usage.dart b/args/lib/src/usage.dart
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-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library args.src.usage;
-
-import 'dart:math';
-
-import '../args.dart';
-
-/// Takes an [ArgParser] and generates a string of usage (i.e. help) text for
-/// its defined options.
-///
-/// Internally, it works like a tabular printer. The output is divided into
-/// three horizontal columns, like so:
-///
-///     -h, --help  Prints the usage information
-///     |  |        |                                 |
-///
-/// It builds the usage text up one column at a time and handles padding with
-/// spaces and wrapping to the next line to keep the cells correctly lined up.
-class Usage {
-  static const NUM_COLUMNS = 3; // Abbreviation, long name, help.
-
-  /// A list of the [Option]s intermingled with [String] separators.
-  final List optionsAndSeparators;
-
-  /// The working buffer for the generated usage text.
-  StringBuffer buffer;
-
-  /// The column that the "cursor" is currently on.
-  ///
-  /// If the next call to [write()] is not for this column, it will correctly
-  /// handle advancing to the next column (and possibly the next row).
-  int currentColumn = 0;
-
-  /// The width in characters of each column.
-  List<int> columnWidths;
-
-  /// The number of sequential lines of text that have been written to the last
-  /// column (which shows help info).
-  ///
-  /// We track this so that help text that spans multiple lines can be padded
-  /// with a blank line after it for separation. Meanwhile, sequential options
-  /// with single-line help will be compacted next to each other.
-  int numHelpLines = 0;
-
-  /// How many newlines need to be rendered before the next bit of text can be
-  /// written.
-  ///
-  /// We do this lazily so that the last bit of usage doesn't have dangling
-  /// newlines. We only write newlines right *before* we write some real
-  /// content.
-  int newlinesNeeded = 0;
-
-  Usage(this.optionsAndSeparators);
-
-  /// Generates a string displaying usage information for the defined options.
-  /// This is basically the help text shown on the command line.
-  String generate() {
-    buffer = new StringBuffer();
-
-    calculateColumnWidths();
-
-    for (var optionOrSeparator in optionsAndSeparators) {
-      if (optionOrSeparator is String) {
-        // Ensure that there's always a blank line before a separator.
-        if (buffer.isNotEmpty) buffer.write("\n\n");
-        buffer.write(optionOrSeparator);
-        newlinesNeeded = 1;
-        continue;
-      }
-
-      var option = optionOrSeparator as Option;
-      if (option.hide) continue;
-
-      write(0, getAbbreviation(option));
-      write(1, getLongOption(option));
-
-      if (option.help != null) write(2, option.help);
-
-      if (option.allowedHelp != null) {
-        var allowedNames = option.allowedHelp.keys.toList(growable: false);
-        allowedNames.sort();
-        newline();
-        for (var name in allowedNames) {
-          write(1, getAllowedTitle(name));
-          write(2, option.allowedHelp[name]);
-        }
-        newline();
-      } else if (option.allowed != null) {
-        write(2, buildAllowedList(option));
-      } else if (option.defaultValue != null) {
-        if (option.isFlag && option.defaultValue == true) {
-          write(2, '(defaults to on)');
-        } else if (!option.isFlag) {
-          write(2, '(defaults to "${option.defaultValue}")');
-        }
-      }
-
-      // If any given option displays more than one line of text on the right
-      // column (i.e. help, default value, allowed options, etc.) then put a
-      // blank line after it. This gives space where it's useful while still
-      // keeping simple one-line options clumped together.
-      if (numHelpLines > 1) newline();
-    }
-
-    return buffer.toString();
-  }
-
-  String getAbbreviation(Option option) {
-    if (option.abbreviation != null) {
-      return '-${option.abbreviation}, ';
-    } else {
-      return '';
-    }
-  }
-
-  String getLongOption(Option option) {
-    var result;
-    if (option.negatable) {
-      result = '--[no-]${option.name}';
-    } else {
-      result = '--${option.name}';
-    }
-
-    if (option.valueHelp != null) result += "=<${option.valueHelp}>";
-
-    return result;
-  }
-
-  String getAllowedTitle(String allowed) {
-    return '      [$allowed]';
-  }
-
-  void calculateColumnWidths() {
-    int abbr = 0;
-    int title = 0;
-    for (var option in optionsAndSeparators) {
-      if (option is! Option) continue;
-      if (option.hide) continue;
-
-      // Make room in the first column if there are abbreviations.
-      abbr = max(abbr, getAbbreviation(option).length);
-
-      // Make room for the option.
-      title = max(title, getLongOption(option).length);
-
-      // Make room for the allowed help.
-      if (option.allowedHelp != null) {
-        for (var allowed in option.allowedHelp.keys) {
-          title = max(title, getAllowedTitle(allowed).length);
-        }
-      }
-    }
-
-    // Leave a gutter between the columns.
-    title += 4;
-    columnWidths = [abbr, title];
-  }
-
-  void newline() {
-    newlinesNeeded++;
-    currentColumn = 0;
-    numHelpLines = 0;
-  }
-
-  void write(int column, String text) {
-    var lines = text.split('\n');
-
-    // Strip leading and trailing empty lines.
-    while (lines.length > 0 && lines[0].trim() == '') {
-      lines.removeRange(0, 1);
-    }
-
-    while (lines.length > 0 && lines[lines.length - 1].trim() == '') {
-      lines.removeLast();
-    }
-
-    for (var line in lines) {
-      writeLine(column, line);
-    }
-  }
-
-  void writeLine(int column, String text) {
-    // Write any pending newlines.
-    while (newlinesNeeded > 0) {
-      buffer.write('\n');
-      newlinesNeeded--;
-    }
-
-    // Advance until we are at the right column (which may mean wrapping around
-    // to the next line.
-    while (currentColumn != column) {
-      if (currentColumn < NUM_COLUMNS - 1) {
-        buffer.write(padRight('', columnWidths[currentColumn]));
-      } else {
-        buffer.write('\n');
-      }
-      currentColumn = (currentColumn + 1) % NUM_COLUMNS;
-    }
-
-    if (column < columnWidths.length) {
-      // Fixed-size column, so pad it.
-      buffer.write(padRight(text, columnWidths[column]));
-    } else {
-      // The last column, so just write it.
-      buffer.write(text);
-    }
-
-    // Advance to the next column.
-    currentColumn = (currentColumn + 1) % NUM_COLUMNS;
-
-    // If we reached the last column, we need to wrap to the next line.
-    if (column == NUM_COLUMNS - 1) newlinesNeeded++;
-
-    // Keep track of how many consecutive lines we've written in the last
-    // column.
-    if (column == NUM_COLUMNS - 1) {
-      numHelpLines++;
-    } else {
-      numHelpLines = 0;
-    }
-  }
-
-  String buildAllowedList(Option option) {
-    var allowedBuffer = new StringBuffer();
-    allowedBuffer.write('[');
-    bool first = true;
-    for (var allowed in option.allowed) {
-      if (!first) allowedBuffer.write(', ');
-      allowedBuffer.write(allowed);
-      if (allowed == option.defaultValue) {
-        allowedBuffer.write(' (default)');
-      }
-      first = false;
-    }
-    allowedBuffer.write(']');
-    return allowedBuffer.toString();
-  }
-}
-
-/// Pads [source] to [length] by adding spaces at the end.
-String padRight(String source, int length) {
-  final result = new StringBuffer();
-  result.write(source);
-
-  while (result.length < length) {
-    result.write(' ');
-  }
-
-  return result.toString();
-}