#!/usr/bin/env ruby

require 'optparse'
require 'pathname'

class LineProcessor
  MATCHERS = {
    :layout => /^layout:\s*(\S*)$/i,
    :single_line_redirect => /^redirect_\w+:\s*\S+$/i,
    :base_url => /\{\{\s*site\.baseurl\s*\}\}(\S+)/i,
    :asset_url => /\{\{\s*site\.baseurl\s*\}\}[^assets]\S*/i
  }

  attr_reader :line, :options

  def initialize(line, options = {})
    @line = line
    @options = options
  end

  def process
    @line = use_locale_layout
    @line = remove_single_line_redirects
    @line = replace_site_baseurl
    @line
  end

  def english?
    options[:lang] == 'en'
  end

  private

  def use_locale_layout
    return line if english?
    match = line.match(MATCHERS[:layout])

    if match
      "layout: #{ options[:lang] }/#{ match[1] }"
    else
      line
    end
  end

  def remove_single_line_redirects
    return line if english?
    match = line.match(MATCHERS[:single_line_redirect])

    if match
      ''
    else
      line
    end
  end

  def replace_site_baseurl
    line.gsub(MATCHERS[:base_url]) do |match|
      new_match = match =~ MATCHERS[:asset_url]
      if new_match
        match.gsub(/\{\{\s?site.baseurl\s?\}\}/, '{{ page.baseurl }}/')
      else
        match
      end
    end
  end

end

class UnsupportedMatchChecker
  UNSUPPORTED_MATCHERS = {
    :multi_line_redirect => /^redirect_\w+:(\s*-{1}\s*.*)+$/i,
    :include_template => /\{\%\s*include/i
  }

  attr_reader :warnings

  def initialize(file_contents, file_name = 'File')
    @warnings = []
    UNSUPPORTED_MATCHERS.each do |name, regex|
      if file_contents =~ regex
        @warnings << "WARNING: #{ file_name } contains #{ name } which cannot be processed"
      end
    end
  end
end

options = {}
optionparser = OptionParser.new do |opts|
  opts.banner = "Usage: #{ __FILE__ } [options] source_file"

  opts.on("--force", "Ignore warnings and continue processing the source_file") do |f|
    options[:force] = f
  end

  opts.on("-h", "--help", "Show this message") do
    puts opts
    exit
  end

  opts.on("--in-place", "Write the processed text back to the source_file") do |p|
    options[:in_place] = p
  end

  opts.on("-l", "--lang=LANG", "Two-letter language code of the source_file") do |s|
    options[:lang] = s.downcase
  end

  opts.on("-o", "--output-file=FILE", "File to write the processed text to") do |o|
    options[:output_file] = o
  end
end
optionparser.parse!

unless ARGV.length == 1
  puts optionparser.help
  exit 1
end

source_file = ARGV.shift

if options[:in_place]
  options[:output_file] = source_file
end

unless options[:force]
  source_file_contents = File.read(source_file)
  source_file_path = Pathname.new(source_file).realpath
  warnings = UnsupportedMatchChecker.new(source_file_contents, source_file_path).warnings
  if warnings.any?
    puts warnings
    puts "Use --force to ignore warnings and continue processing the file"
    exit 1
  end
end

new_contents = []

File.readlines(source_file).map do |line|
  new_contents << LineProcessor.new(line, options).process
end

if options[:output_file]
  File.open(options[:output_file], 'w') { |f| f.puts(new_contents) }
else
  puts(new_contents)
end