require 'set'

IGNORED_PAGES = Set['sitemap.xml']
LANGS = Set['en', 'pt', 'fr', 'eo'] # jp zh es de

module Jekyll
  class Linter < Generator
    safe true
    priority :high

    def insert_id(name, document)
      lang = document.data['lang']
      ref = document.data['ref']
      id = "#{name}:#{lang}:#{ref}"
      if @known_ids.include? id then
        raise "Duplicate ID found: '#{id}'"
      else
        @known_ids.add id
      end
    end

    def assert_unique_ids(site)
      @known_ids = Set[]
      all_documents(site) do |collection_name, document|
        insert_id collection_name, document
      end
    end

    def slugify(s)
      s.ljust(100)
        .gsub(/[()']/, '')
        .gsub(/[\W]+/, ' ')
        .strip
        .gsub(/\s\s+/, '-')
        .downcase
        .gsub(' ', '-')
        .gsub('_', '-')
    end

    def assert(value, message)
      unless value
        raise message
      end
      value
    end

    def assert_field(document, field)
      f = document.data[field]
      raise "Undefined '#{field}' for #{document.path}" unless f
      f
    end

    COLLECTION_LAYOUTS = {
      'page' => 'default',
      'slides' => 'slides',
      'articles' => 'post',
      'pastebins' => 'post',
      'tils' => 'post',
      'podcasts' => 'post',
      'screencasts' => 'post'
    }

    def assert_frontmatter_fields(name, document)
      title = assert_field document, 'title'
      lang = assert_field document, 'lang'
      ref = assert_field document, 'ref'
      layout = assert_field document, 'layout'
      date = document.date.strftime('%Y-%m-%d') unless layout == 'default'
      slug = layout == 'default' ? ref : assert_field(document, 'slug')
      extension = name == 'slides' ? 'slides' : 'md'

      unless LANGS.member? lang
        raise "Invalid lang '#{lang}' in #{document.path}"
      end

      if COLLECTION_LAYOUTS[name] != layout
        raise "Layout mismatch: expected '#{COLLECTION_LAYOUTS[name]}', got '#{layout}' for #{document.path}"
      end

      if lang == 'en'
        unless ['index', 'root', 'tils'].include? ref
          if slugify(title) != ref then
            raise "#{ref} isn't a slug of the title.\nref:        '#{ref}'\ntitle slug: '#{slugify(title)}'"
          end
        end
      end

      unless layout == 'default' then
        path = "_#{name}/#{date}-#{slug}.#{extension}"
        unless path == document.relative_path then
          raise "date/filename mismatch:\ndate+slug: #{path}\nfilename:  #{document.relative_path}"
        end

        if lang == 'en' then
          unless ref == slug then
            raise "ref/slug mismatch:\nref:  #{ref}\nslug: #{slug}"
          end
        end
      end

      if name == 'podcasts' then
        flac = "resources/podcasts/#{date}-#{slug}.flac"
        unless File.exist? flac then
          raise "Missing FLAC file '#{flac}'"
        end
      end

      if name == 'screencasts' then
        webm = "resources/screencasts/#{date}-#{slug}.webm"
        unless File.exist? webm then
          raise "Missing WebM file '#{webm}'"
        end
      end
    end

    def assert_frontmatter(site)
      all_documents(site) do |collection_name, document|
        assert_frontmatter_fields collection_name, document
      end
    end

    MEDIA_EXTENSION = {
      'podcasts' => 'flac',
      'screencasts' => 'webm'
    }

    def assert_media_metadata(site)
      site.collections.each do |name, collection|
        if ['podcasts', 'screencasts'].include? name then
          collection.docs.each do |document|
            date = document.data['date'].strftime('%Y-%m-%d')
            slug = document.data['slug']
            ext = MEDIA_EXTENSION[name]
            file =  "resources/#{name}/#{date}-#{slug}.#{ext}"
            feed_name = site.config['t'][name]['feed']['title'][document.data['lang']]
            if name == 'podcasts'
              stdout = `metaflac --export-tags-to=- #{file}`.strip.split("\n")
              expected = [
                "COMMENTS=#{site.config['url']}/#{file}",
                'ARTIST=EuAndreh',
                "DATE=#{date}",
                "TITLE=#{document.data['title']}",
                "ALBUM=#{feed_name}"
              ]
              expected.each do |metadata|
                unless stdout.include? metadata
                  tags = expected.join('\\n').gsub(/'/, "'\"'\"'")
                  add_metadata_cmd = "metaflac --remove-all #{file}\nprintf '#{tags}\\n' | metaflac --import-tags-from=- #{file}"
                  check_metadata_cmd = "metaflac --export-tags-to=- #{file}"
                  raise "Missing metadata entry '#{metadata}' in '#{file}'.\nAdd it with:\n\n#{add_metadata_cmd}\n\nCheck with:\n  #{check_metadata_cmd}"
                end
              end

              check_cover_cmd = "metaflac #{file} --export-picture-to=- | diff - static/favicon.png"
              `#{check_cover_cmd}`
              unless $?.success? then
                add_cover_cmd = "metaflac #{file} --import-picture-from=static/favicon.png"
                raise "Cover art from '#{file}' doesn't match 'static/favicon.png'.\nFix it with:\n\n#{add_cover_cmd}\n\nCheck with:\n  #{check_cover_cmd}"
              end
            elsif name == 'screencasts' then
              stdout = `mediainfo #{file} | awk -F: '/^Movie name/ { print $2 }'`.strip
              expected = document.data['title'] + ' - ' + feed_name
              unless stdout == expected then
                escaped_title = expected.gsub(/'/, "'\"'\"'")
                add_metadata_cmd = "mkvpropedit '#{file}' -e info -s title='#{escaped_title}'"
                check_metadata_cmd = "mediainfo '#{file}' | grep 'Movie name'"
                raise "Missing metadata entry 'title' in '#{file}'.\nAdd it with:\n\n#{add_metadata_cmd}\n\nCheck with:\n  #{check_metadata_cmd}"
              end
            end
          end
        end
      end
    end

    def assert_lilypond(site)
      site.config['musics'].each do |music|
        assert music['title'], "Missing 'title' in #{music}"
        assert music['composer'], "Missing 'composer' in #{music}"
        ref = assert music['ref'], "Missing 'ref' in #{music}"
        ly = "music/#{ref}.ly"
        unless File.exist? ly then
          raise "Missing '#{ly}' file present in _config.yml."
        end

        unless open(ly) { |f| f.include? "\\pointAndClickOff\n" } then
          raise "Missing '\\pointAndClickOff' in '#{ly}'"
        end
        unless open(ly) { |f| f.include? "#(ly:set-option 'embed-source-code #t)\n" } then
          raise "Missing '#(ly:set-option 'embed-source-code #t)' in '#{ly}'"
        end
      end
    end

    def generate(site)
      assert_unique_ids(site)
      assert_frontmatter(site)
      assert_media_metadata(site)
      assert_lilypond(site)
    end

    def all_documents(site)
      site.collections.each do |name, collection|
        collection.docs.each do |document|
          unless document.data['generated']
            yield name, document
          end
        end
      end

      site.pages.each do |page|
        unless IGNORED_PAGES.include? page.path
          unless page.data['generated']
            yield 'page', page
          end
        end
      end
    end
  end
end