#! /usr/bin/env nix-shell
#! nix-shell -i bash -p nix curl jq nix-prefetch-github git gnused gnugrep -I nixpkgs=.
# shellcheck shell=bash

set -eu -o pipefail

# Stackage solver to use, LTS or Nightly
# (should be capitalized like the display name)
SOLVER=LTS
TMP_TEMPLATE=update-stackage.XXXXXXX
readonly SOLVER
readonly TMP_TEMPLATE

toLower() {
    printf "%s" "$1" | tr '[:upper:]' '[:lower:]'
}

tmpfile=$(mktemp "$TMP_TEMPLATE")
tmpfile_new=$(mktemp "$TMP_TEMPLATE")

stackage_config="pkgs/development/haskell-modules/configuration-hackage2nix/stackage.yaml"

trap 'rm "${tmpfile}" "${tmpfile_new}"' 0
touch "$tmpfile" "$tmpfile_new" # Creating files here so that trap creates no errors.

curl -L -s "https://stackage.org/$(toLower "$SOLVER")/cabal.config" >"$tmpfile"
old_version=$(grep '^# Stackage' $stackage_config | sed -e 's/.\+ \([A-Za-z]\+ [0-9.-]\+\)$/\1/g')
version="$SOLVER $(sed -rn "s/^--.*http:..(www.)?stackage.org.snapshot.$(toLower "$SOLVER")-//p" "$tmpfile")"

if [[ "$old_version" == "$version" ]]; then
   echo "No new stackage version"
   exit 0 # Nothing to do
fi

echo "Updating Stackage from $old_version to $version."

# Create a simple yaml version of the file.
sed -r \
    -e '/^--/d' \
    -e 's|^constraints:||' \
    -e 's|^ +|  - |' \
    -e 's|,$||' \
    -e '/installed$/d' \
    -e '/^$/d' \
    < "${tmpfile}" | sort --ignore-case >"${tmpfile_new}"

cat > $stackage_config << EOF
# Stackage $version
# This file is auto-generated by
# maintainers/scripts/haskell/update-stackage.sh
default-package-overrides:
EOF

# Drop restrictions on some tools where we always want the latest version.
sed -r \
    -e '/ cabal2nix /d' \
    -e '/ distribution-nixpkgs /d' \
    -e '/ jailbreak-cabal /d' \
    -e '/ language-nix /d' \
    -e '/ cabal-install /d' \
    < "${tmpfile_new}" >> $stackage_config

if [[ "${1:-}" == "--do-commit" ]]; then
git add $stackage_config
git commit -F - << EOF
haskellPackages: stackage $old_version -> $version

This commit has been generated by maintainers/scripts/haskell/update-stackage.sh
EOF
fi