# Nick's web site: imgresize filter.  Helper for resizing images during site
# compilations for thumbnails, etc.
#
# Copyright © 2016, 2020 Nick Bowler
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

class ImgResize < Nanoc::Filter
    identifier :imgresize
    type       :binary

    def fetch_from_cache(filename, params)
        return unless params[:cache]

        cachefile = File.join(@config[:output_dir], params[:cache])
        begin
            s = File.stat(cachefile)
        rescue Errno::ENOENT
            return
        end

        return unless s.mtime >= File.stat(filename).mtime

        begin
            File.link(cachefile, output_filename)
        rescue
            FileUtils.copy_file(cachefile, output_filename)
        end

        return true
    end

    def run(filename, params = {})
        w = if params[:width] then params[:width].to_i end
        h = if params[:height] then params[:height].to_i end
        scale = [w, h && "x", h].join

        args = ["-scale", scale, filename]
        case filename
        when /\.jpg$/
            args << "-quality" << "85"
        end
        args << output_filename

        unless fetch_from_cache(filename, params)
            system('gm', 'convert', *args)
        end
    end
end