# Nick's web site: imginfo filter.  Generate XML representation of image
# metadata which can be further processed into a web page.
#
# Copyright © 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 ImgInfoFilter < Nanoc::Filter
    identifier :imginfo
    type :binary => :text

    require 'exifr/jpeg'
    require 'fastimage'

    def do_variant(xml, name, item = @item, rep: :default)
        file = item.reps[rep].raw_path

        w, h = FastImage.size(file)
        sz = File.size(file)

        xml.variant {
            xml.name(name)
            xml.uri(item_uri(item, rep: rep))
            xml.width(w)
            xml.height(h)
            xml.filesize(human_filesize(sz))
        }
    end

    def run(filename, params = {})
        exif = EXIFR::JPEG.new(filename).to_hash

        b = Nokogiri::XML::Builder.new do |xml|
            xml.image {
                do_variant(xml, "Large", rep: :large)
                do_variant(xml, "Original")


                if @item[:description]
                    xml.description(:xmlns => 'http://www.w3.org/1999/xhtml') {
                        xml << @item[:description]
                    }
                end

                xml.exif {
                    exif.each do |key, value|
                        # Convert some fields to more useful forms...
                        case key
                        when :f_number, :exposure_bias_value
                            value = sprintf("%.1f", value)
                        when :focal_length
                            value = sprintf("%d\n", value)
                        when :gps_version_id
                            value = value.bytes.join(".")
                        when :exposure_program
                            case value
                            when 1 then value = "Manual"
                            when 2 then value = "Normal program"
                            when 3 then value = "Aperture priority"
                            when 4 then value = "Shutter priority"
                            end
                        when :metering_mode
                            case value
                            when 1 then value = "Average"
                            when 2 then value = "Center weighted average"
                            when 3 then value = "Spot"
                            when 4 then value = "Multi-spot"
                            when 5 then value = "Pattern"
                            when 6 then vlaue = "Partial"
                            end
                        when :flash
                            tmp = if value & 1 == 1 then "Yes" else "No" end
                            case (value >> 3) & 3
                            when 1, 2 then tmp += ", compulsory"
                            when 3 then tmp += ", auto"
                            end
                            case (value >> 1) & 3
                            when 2 then tmp += ", return light not detected"
                            when 3 then tmp += ", return light detected"
                            end
                            value = tmp
                        end

                        case value
                        when String
                            value.delete!("\x00")
                            value.strip!
                        when Time
                            # EXIF does not do timezones so don't display one
                            value = value.strftime("%Y-%m-%d %H:%M:%S")
                        end

                        xml.send((key.to_s << "_").to_sym, value.to_s)
                    end
                }
            }
        end
        b.to_xml
    end
end