#! /bin/sh

own_dir="$(cd "$(dirname "$0")"; sh -c pwd)"

main_file="$1"
main_dir="$(cd "$(dirname "$main_file")" ; sh -c pwd)"
file_name="$(basename "$main_file")"
defs_file="$main_dir"/src-info-for-"$file_name"
src_file="$main_dir"/src-for-"$file_name"
new_src_file="$main_dir"/updated-src-for-"$file_name"

forcedUrl="$2"

defs_dir="$("$own_dir"/attrset-to-dir.sh "$defs_file")"
src_defs_dir="$("$own_dir"/attrset-to-dir.sh "$src_file")"

getAttr () {
    file="$defs_dir"/"$1"
    data="$( ( [ -f "$file" ] && cat "$file" ) || echo "$2" )"
    echo "attribute $1 obtained as: [[$data]]" >&2
    echo "$data"
}

if [ -z "$forcedUrl" ] ; then
    freshUrl="$("$own_dir"/urls-from-page.sh "$(getAttr downloadPage)" |
      egrep "$(getAttr sourceRegexp '.*[.]tar[.].*')" | 
      sh -c "$(getAttr choiceCommand 'head -1')")"

    echo "Found download link: $freshUrl" >&2
else
    freshUrl="$forcedUrl"
fi

if [ x"$freshUrl" = x"$(cat "$src_defs_dir"/advertisedUrl)" ]; then
    echo "Source link not changed" >&2
    exit
fi

version="$(echo "$freshUrl" | 
  sed -re "$(getAttr versionExtractorSedScript \
    's/.*-([0-9.]+)[.].*/\1/')")"

mirrorUrl="$(echo "$freshUrl" | 
  sed -r -e "$(getAttr versionReferenceCreator \
    's/-([0-9.]+)[.]/-${version}./')" |
  sed -r -e "$(getAttr mirrorSedScript)")"

hash=$(nix-prefetch-url "$freshUrl")

cat << EOF > "$new_src_file"
rec {
  advertisedUrl="$freshUrl";
  version = "$version";
  url="$mirrorUrl";
  hash = "$hash";
}
EOF