#!/usr/bin/env ruby
require 'optparse'
require 'rubygems'

$LOAD_PATH.unshift(File.expand_path(File.dirname(__FILE__) + "/../lib"))
require 'treetop'
require 'treetop/version'
require 'treetop/polyglot'

options = {}
parser = OptionParser.new do |opts|
  exts = Treetop::Polyglot::VALID_GRAMMAR_EXT.collect { |i| '.' + i }

  opts.banner = "Treetop Parsing Expression Grammar (PEG) Comand Line Compiler"
  opts.define_head "Usage: tt [options] grammar_file[#{exts.join('|')}] ..."
  opts.separator ''
  opts.separator 'Examples:'
  opts.separator '  tt foo.tt               # 1 grammar -> 1 parser source'
  opts.separator '  tt foo bar.treetop      # 2 grammars -> 2 separate parsers'
  opts.separator '  tt -o alt_name.rb foo   # alternately named output file'
  opts.separator ''
  opts.separator ''
  opts.separator 'NOTE: while treetop grammar files *must* have one of the following'
  opts.separator 'filename extensions, the extension name is not required when calling'
  opts.separator 'the compiler with grammar file names.'
  opts.separator ''
  opts.separator "  Valid extensions: #{exts.join(', ')}"
  opts.separator ''
  opts.separator ''
  opts.separator 'Options:'

  opts.on('-o', '--output FILENAME', 'Write parser source to FILENAME') do |fn|
    options[:out_file] = fn
  end

  opts.on('-f', '--force', 'Overwrite existing output file(s)') do
    options[:force] = true
  end

  opts.on_tail('-v', '--version', 'Show Treetop version') do
    puts "Treetop v#{Treetop::VERSION::STRING}"
    exit
  end

  opts.on_tail('-h', '--help', 'Show this help message') do
    puts opts
    exit
  end

end
file_list = parser.parse!

# check options and arg constraints
if file_list.empty? || (options[:out_file] && file_list.size > 1)
  puts parser
  exit 1
end

def grammar_exist?(filename)
  if File.extname(filename).empty?
    Treetop::Polyglot::VALID_GRAMMAR_EXT.each do |ext|
      fn_ext = "#{filename}.#{ext}"
      return true if File.exist?(fn_ext) && !File.zero?(fn_ext)
    end
  end
  File.exist?(filename) && !File.zero?(filename)
end

def full_grammar_filename(filename)
  return filename if !File.extname(filename).empty?
  Treetop::Polyglot::VALID_GRAMMAR_EXT.each do |ext|
    fn_ext = "#{filename}.#{ext}"
    return fn_ext if File.exist?(fn_ext) && !File.zero?(fn_ext)
  end
end

def protect_output?(filename, forced=false)
  if !forced and
      File.exist?(filename) and
      File.open(filename) { |f| ![(f.gets rescue ''), (f.gets rescue '')].include? Treetop::Compiler::AUTOGENERATED }
    puts "ERROR: '#{filename}' output already exists; skipping compilation...\n"
    return true
  end
  false
end

compiler = Treetop::Compiler::GrammarCompiler.new

while !file_list.empty?
  treetop_file = file_list.shift

  # handle nonexistent and existent grammar files mixed together
  if !grammar_exist?(treetop_file)
    puts "ERROR: input grammar file '#{treetop_file}' does not exist; continuing...\n"
    next
  end

  # try to compile
  treetop_file = full_grammar_filename(treetop_file)
  std_output_file = treetop_file.gsub(Treetop::Polyglot::VALID_GRAMMAR_EXT_REGEXP, '.rb')

  if options[:out_file]
    # explicit output file name option; never overwrite unless forced
    next if protect_output?(options[:out_file], options[:force])
    compiler.compile(treetop_file, options[:out_file])
  else
    # compile one input file from input file list option; never overwrite unless forced
    next if protect_output?(std_output_file, options[:force])
    compiler.compile(treetop_file)
  end

end
