message
  = segments
segments
  = head:msh tail:(newline segment:segment { return segment; })* {
    tail.unshift(head);
    return tail;
  }
msh
  = "MSH" fs:field_separator cs:component_separator fr:field_repeat_delimiter ec:escape_character ss:subcomponent_separator tail:(field_separator field:field { return field; })* {
    tail.unshift([['MSH']], [[ cs + fr + ec + ss ]]);
    return tail;
  }
segment
  = head:field tail:(field_separator field:field { return field; })* {
    tail.unshift(head);
    return tail;
  }
field
  = head:component tail:(component_separator component:component { return component;} )* {
    tail.unshift(head);
    return tail;
  }
component
  = head:subcomponent tail:(subcomponent_separator subcomponent:subcomponent { return subcomponent; })* {
    tail.unshift(head);
    return tail;
  }
subcomponent
  = content:(!(subcomponent_separator / component_separator / field_separator / newline) char:char { return char; } )* {
    return content.join('');
  }
char =
  .
escape_character
  = "\<%=escape%>"
field_repeat_delimiter
  = "<%=repeat%>"
field_separator
  = "<%=fields%>"
component_separator
  = "<%=components%>"
newline
  = [\r\n]+
subcomponent_separator
  = "<%=subcomponents%>"