HTML template framework prototype

main.dart

import 'dart:mirrors';

class ElementBuilder {
  final String tag;
  
  ElementBuilder(this.tag);
  
  dynamic noSuchMethod(Invocation invocation) {
    final pArgs = invocation.positionalArguments;
    
    List<String> classes = [];
    List children = [];
    var id = '';
    var text = '';
    
    // Figure out classes and IDs.
    if (pArgs.isNotEmpty) {
      // Try to parse first argument as class or ID.
      String first = pArgs.first.toString();
      final idPattern = new RegExp(r'#([a-z-]+)(?:.|$)');
      final classPattern = new RegExp(r'\.([a-z-]+)(?:.|$)');
      final idMatch = idPattern.matchAsPrefix(first);
      if (idMatch != null) {
        id = idMatch.group(1);
        first = first.substring(id.length + 1);
      }
      
      do {
        final classMatch = classPattern.matchAsPrefix(first);
        
        if (classMatch == null) {
          id = '';
          classes.clear();
          text = first;
          break;
        } else {
          classes.add(classMatch.group(1));
          first = first.substring(classes.last.length + 1);
        }
      } while (first.isNotEmpty);
      
      if (text.isEmpty && pArgs.length > 1) {
        if (pArgs[1] is List) {
          children = pArgs[1];
        } else {
          text = pArgs[1].toString();
        }
      }
    }
    
    final named = invocation.namedArguments;
    final attrs = new Map<String, String>.fromIterable(named.keys,
      key: (sym) => MirrorSystem.getName(sym).replaceAll('_', ''),
      value: (sym) => named[sym].toString());
  
    if (id.isNotEmpty) {
      attrs['id'] = id;
    }
    if (classes.isNotEmpty) {
      attrs['class'] = classes.join(' ');
    }
    
    attrs.remove('c');
    
    final akeys = attrs.keys.toList();
    final attrsStr = new List<String>.generate(akeys.length,
      (i) => '${akeys[i]}="${attrs[akeys[i]]}"').join(' ');
      
    final childrenSymbol = new Symbol('c');
    if (named.containsKey(childrenSymbol)) {
      children = new List.from(named[childrenSymbol]);
    }
      
    // Process children (that is, collapse lists into each other).
    var containedLists = true;
    while (containedLists) {
      containedLists = false;
      for (var i = 0; i < children.length; i++) {
        if (children[i] is List) {
          containedLists = true;
          final list = children.removeAt(i);
          
          // Insert all items of this list at this position,
          // and move the index forward.
          children.insertAll(i, list);
          i += list.length - 1;
        }
      }
    }
    
    final open = akeys.isEmpty ? tag : '$tag $attrsStr';
    if (children.isNotEmpty) {
      return '<$open>${children.join()}</$tag>';
    } else if (text.isNotEmpty) {
      return '<$open>$text</$tag>';
    } else {
      return '<$open />';
    }
  }
}

final div = new ElementBuilder('div');

main() {
  print(div('.container', [
      [
        div('#mydiv.hello', 'Hello World!', stuff: 'a'),
        div('#mydiv.hello.hi', 'Hello World!', arst: 'a')
      ]
    ])
  );
}