# Nick's web site: Export public keys for the Web Key Directory
#
# Copyright © 2022 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/>.

module WKD
    require 'open3'

    @@gpg2 = "/usr/bin/gpg"
    @@wksclient = "/usr/libexec/gpg-wks-client"

    def WKD.gpg2; @@gpg2 end
    def WKD.gpg2=(x); @@gpg2 = x end
    def WKD.wksclient; @@wksclient end
    def WKD.wksclient=(x); @@wksclient = x end

    # Return a list list of all UIDs known from the given GPG keyrings.
    def WKD.uids_from_keyrings(*args)
        uids = {}

        Open3.popen2(@@gpg2,
            "--no-default-keyring", "--with-colons", "--list-keys",
            *args.map { |x| "--keyring=" + (x['/'] ? x : "./" + x) }
        ) do |stdin, stdout, result|
            stdin.close
            stdout.each do |line|
                fields = line.split(":")
                next if fields[0] != "uid"
                fields[9].gsub!(/\\x../) { |x| x[2..].hex.chr }
                uids[fields[9]] = true
            end
            stdout.close

            raise "gpg failed" unless result.value.success?
        end

        return uids.keys
    end

    # Given a list of UIDs, return a dictionary where the keys are UIDs
    # and the values are the WKS hash.
    def WKD.hashes_from_uids(*args)
        wkd_hash = {}

        consume_output = Proc.new do |s|
            while l = s.slice!(/([^\n]*)\n/) do
                hash, uid = l.chomp.split(nil, 2)
                wkd_hash[uid] = hash
            end
        end

        Open3.popen2(@@wksclient,
            "--print-wkd-hash"
        ) do |stdin, stdout, result|
            buf = ""
            args.flatten.each do |uid|
                stdin.puts(uid)
                stdin.flush

                loop do
                    buf += stdout.read_nonblock(100)
                    consume_output.call(buf)
                rescue EOFError, IO::WaitReadable
                    break
                end
            end
            stdin.close

            loop do
                buf += stdout.readpartial(100)
                consume_output.call(buf)
            rescue EOFError
                break
            end
            stdout.close

            raise "gpg-wks-client failed" unless result.value.success?
        end

        return wkd_hash
    end

end

# Call during preprocessing to create items for each unique UID found in the
# given keyring items.  The items have the identifier /gpg/UID and the content
# is the same UID.  The items are created with the :keyrings attribute set to
# the list of keyring files and :wkd_hash is for the Web Key Directory.
def create_wkd_items(keyring_items)
    keyring_files = {}
    [*keyring_items].each { |item| keyring_files[item.raw_filename] = true }

    wkd = WKD.hashes_from_uids(WKD.uids_from_keyrings(*keyring_files.keys))
    wkd.each do |uid, hash|
        attrs = {
            keyrings: keyring_files.keys,
            wkd_hash: hash
        }
        @items.create(uid, attrs, "/gpg/" + uid)
    end
end

# Convert items created by create_wkd_items into real GPG keyrings.
class WKDExport < Nanoc::Filter
    identifier :wkd_export
    type :text => :binary

    def run(content, params = {})
        args = @item[:keyrings].map { |x|
            "--keyring=" + (x['/'] ? x : "./" + x)
        };
        args.append("--armor") if params[:armor]

        dummy, result = Open3.capture2(WKD.gpg2, "--export",
            "--no-default-keyring", "--output=" + output_filename,
            *args, content.chomp)
        raise "gpg failed" unless result.success?
    end
end