{inCharset, letters, charset, BaseParser} = peasy = require '../peasy'

identifierHeadChars = '$_'+letters
endTextCharset = charset(')@'+identifierHeadChars)
identifierHeadCharset = charset(identifierHeadChars)

exports.TemplateParser = class TemplateParser extends BaseParser
  constructor: ->
    super

    [at, lpar, rpar, exclam] = for c in '@()!' then do(c=c) => @char(c)

    mayExclam = @may(exclam)

    error = (msg) => throw @data[@cur-20..@cur+20]+' '+@cur+': '+msg

    tcall = => (f = tfield()) and lpar() and (args = template()) and ((rpar() and f+'('+args+')') or error('expect )'))

    tfield = @memo(=> at() and (((id=@identifier()) and mayExclam() and 't.'+id) or error('expect @identifier')))

    field = => (id=@identifier()) and mayExclam() and "t.transform(e.#{id})"

    text = =>
      data = @data
      start = cur = @cur
      result = ''
      while 1
        c = data[cur]
        if (not c) then break
        else if c=='!'
          cur++
          c = data[cur]
          if inCharset(c, identifierHeadCharset)
            @cur = cur
            id = @identifier()
            cur = @cur
            result += id
          else if c=='!' or c=='@' or c==')'
            result += c
            cur++
          else if c
            result += '!'+c
            cur++
          else break
        else if c=='\n' then cur++; result +='\\n'
        else if inCharset(c, endTextCharset) then break
        else result += c; cur++
      if cur==start then return
      @cur = cur
      if '"' in result then "'"+result+"'"
      else '"'+result+'"'

    anySegment = @any(@orp(tcall, tfield, field, text))
    template = => (x = anySegment()) and x.join(',')
    @root = => (t = template()) and ((@eoi() and t) or error('unexpected )'))

templateParser = new TemplateParser

exports.parseTemplate = parseTemplate = (text) -> templateParser.parse(text)