#! /bin/sh -e

name="$1"
[ -n "$name" ] || { echo "no name"; exit 1; }

cpan -D "$name" > cpan-info

url="$(echo $(cat cpan-info | sed '6!d'))"
[ -n "$url" ] || { echo "no URL"; exit 1; }
url="mirror://cpan/authors/id/$url"
echo "URL = $url" >&2

version=$(cat cpan-info | grep 'CPAN: ' | awk '{ print $2 }')
echo "VERSION = $version"

declare -a xs=($(PRINT_PATH=1 nix-prefetch-url "$url"))
hash=${xs[0]}
path=${xs[1]}
echo "HASH = $hash" >&2

namedash="$(echo $name | sed s/::/-/g)-$version"

attr=$(echo $name | sed s/:://g)

rm -rf cpan_tmp
mkdir cpan_tmp
tar xf "$path" -C cpan_tmp

shopt -s nullglob
meta=$(echo cpan_tmp/*/META.json)
if [ -z "$meta" ]; then
    yaml=$(echo cpan_tmp/*/META.yml)
    [ -n "$yaml" ] || { echo "no meta file"; exit 1; }
    meta=$(echo $yaml | sed s/\.yml$/.json/)
    perl -e '
      use YAML;
      use JSON;
      local $/;
      $x = YAML::Load(<>);
      print encode_json $x;
    ' < $yaml > $meta
fi

description="$(json abstract < $meta | perl -e '$x = <>; print uc(substr($x, 0, 1)), substr($x, 1);')"
homepage="$(json resources.homepage < $meta)"
if [ -z "$homepage" ]; then
    #homepage="$(json meta-spec.url < $meta)"
    true
fi

license="$(json license < $meta | json -a 2> /dev/null || true)"
if [ -z "$license" ]; then
    license="$(json -a license < $meta)"
fi
license="$(echo $license | sed s/perl_5/perl5/)"

f() {
    local type="$1"
    perl -e '
      use JSON;
      local $/;
      $x = decode_json <>;
      if (defined $x->{prereqs}) {
        $x2 = $x->{prereqs}->{'$type'}->{requires};
      } elsif ("'$type'" eq "runtime") {
        $x2 = $x->{requires};
      } elsif ("'$type'" eq "configure") {
        $x2 = $x->{configure_requires};
      } elsif ("'$type'" eq "build") {
        $x2 = $x->{build_requires};
      }
      foreach my $y (keys %{$x2}) {
        next if $y eq "perl";
        eval "use $y;";
        if (!$@) {
          print STDERR "skipping Perl-builtin module $y\n";
          next;
        }
        print $y, "\n";
      };
    ' < $meta | sed s/:://g
}

confdeps=$(f configure)
builddeps=$(f build)
testdeps=$(f test)
runtimedeps=$(f runtime)

buildInputs=$(echo $(for i in $confdeps $builddeps $testdeps; do echo $i; done | sort | uniq))
propagatedBuildInputs=$(echo $(for i in $runtimedeps; do echo $i; done | sort | uniq))

echo "===" >&2

cat <<EOF
  $attr = buildPerlPackage {
    name = "$namedash";
    src = fetchurl {
      url = $url;
      sha256 = "$hash";
    };
EOF
if [ -n "$buildInputs" ]; then
    cat <<EOF
    buildInputs = [ $buildInputs ];
EOF
fi
if [ -n "$propagatedBuildInputs" ]; then
    cat <<EOF
    propagatedBuildInputs = [ $propagatedBuildInputs ];
EOF
fi
cat <<EOF
    meta = {
      homepage = $homepage;
      description = "$description";
      license = "$license";
    };
  };
EOF