class Form():
  FORM_BEGIN  = '<form method="POST">\n'
  FORM_END    = '</form>\n'
  GROUP_BEGIN = '<fieldset>\n'
  GROUP_END   = '</fieldset>\n'
  TITLE_BEGIN = '<legend>'
  TITLE_END   = '</legend>\n'
  FIELD_BEGIN = '<div>'
  FIELD_END   = '</div>\n'
  NAME_BEGIN  = '<span>'
  NAME_END    = '</span>\n'
  VALUE_BEGIN = '<div>'
  VALUE_END   = '</div>\n'
  
  BEGIN       = FORM_BEGIN + GROUP_BEGIN
  END         = GROUP_END + FORM_END
  
  def __init__(self, request):
    self.request = request
    self.answer = self.request.answer
    self.content = ''
  
  def title(self, title):
    return self.TITLE_BEGIN \
         + self.answer.te(title) \
         + self.TITLE_END
  
  def name(self, name):
    return self.NAME_BEGIN \
         + self.answer.te(name) \
         + self.NAME_END
  
  def value_raw(self, raw):
    return self.VALUE_BEGIN \
         + raw \
         + self.VALUE_END
  
  def input(self, name, type, value = None):
    type = self.answer.e(type)
    name = self.answer.e(name)
    value = self.answer.encodedfield(name) if value is None else self.answer.e(value)
    content = '<input'
    if type: content += ' type="' + type + '"'
    if name: content += ' name="' + name + '"'
    if value: content += ' value="' + value + '"'
    content += ' />'
    return content

  def checkbox(self, name, value = None):
    name = self.answer.e(name)
    value = bool(self.answer.fields.get(name) if value is None else value)
    content = '<input type="checkbox" '
    if name: content += ' name="' + name + '"'
    if value: content += ' checked'
    content += ' />'
    return content

  def select(self, name, variants, value = None):
    name = self.answer.e(name)
    value = self.answer.encodedfield(name) if value is None else self.answer.e(value)
    content = '<select'
    if name: content += ' name="' + name + '"'
    content += '>\n'
    for k, v in variants.items():
      kk = self.answer.e(k)
      if kk:
        content += '<option value="' + kk + '"'
        if kk == value: content += 'selected'
        content += '>'
        content += self.answer.te(v)
        content += '</option>\n'
    content += '</select>\n'
    return content

  def textarea(self, name, value = None):
    name = self.answer.e(name)
    value = self.answer.encodedfield(name) if value is None else self.answer.e(value)
    content = '<textarea'
    if name: content += ' name="' + name + '"'
    content += '>\n'
    content += value
    content += '</textarea>'
    return content
  
  def field_raw(self, name, raw):
    content = self.FIELD_BEGIN;
    content += self.name(name)
    content += self.value_raw(raw)
    content += self.FIELD_END;
    return content

  def add_field_raw(self, name, raw):
    self.content += self.field_raw(name, raw)

  def add_hidden(self, name, value):
    self.content += self.input(name, 'hidden', '' if value is None else value)
  def add_input(self, title, *args, **kvargs):
    self.add_field_raw(title, self.input(*args, **kvargs))
  def add_checkbox(self, title, *args, **kvargs):
    self.add_field_raw(title, self.checkbox(*args, **kvargs))
  def add_select(self, title, *args, **kvargs):
    self.add_field_raw(title, self.select(*args, **kvargs))
  def add_textarea(self, title, *args, **kvargs):
    self.add_field_raw(title, self.textarea(*args, **kvargs))
  def add_submit(self, title = 'Submit'):
    self.add_field_raw('', self.input('', 'submit', self.answer.t(title)))

  def begin(self, title, action):
    self.content += self.BEGIN
    if title: self.content += self.title(title)
    if action: self.add_hidden('action', action)
  def end(self):
    self.content += self.END