#!/bin/sh
# Compare the installed packages against the lists for this machine's role.
#
#   packages.sh          what is missing and what is extra
#   packages.sh install  install what is missing
#
# It never removes anything. Extra packages are reported and left alone: on a
# server, individual packages carry mail and web services, and a tool that
# tidies up on its own is a tool that eventually takes one of them down. The
# same caution is why the BookStack upgrade playbook refuses to remove
# anything either.
#
# The lists are data, not code - plain names, one per line. That is deliberate:
# they map onto home-manager and environment.systemPackages almost unchanged if
# this ever moves to Nix, whereas an install script would not.
set -eu

ROLE=$(cat "$HOME/.config/dotconfs/role" 2>/dev/null || echo desktop)
DIR="$(cd "$(dirname "$0")/../packages" 2>/dev/null && pwd)" || {
    echo "packages/ not found next to $0" >&2
    exit 1
}

# Comments and blank lines are for the reader, not the package manager.
read_list() {
    [ -f "$1" ] || return 0
    sed -E 's/#.*//' "$1" | tr -d '\r' | awk 'NF'
}

case "$(uname -s)" in
    Linux)
        command -v pacman >/dev/null 2>&1 || { echo "not an Arch machine" >&2; exit 1; }
        WANT=$(read_list "$DIR/arch-base.txt"; read_list "$DIR/arch-$ROLE.txt" || true)
        HAVE=$(pacman -Qqe)
        INSTALL="yay -S --needed --noconfirm"
        command -v yay >/dev/null 2>&1 || INSTALL="sudo pacman -S --needed"
        ;;
    Darwin)
        command -v brew >/dev/null 2>&1 || { echo "Homebrew not in PATH - is this a login shell?" >&2; exit 1; }
        WANT=$(read_list "$DIR/brew-$ROLE.txt")
        HAVE=$(brew leaves)
        INSTALL="brew install"
        ;;
    *)
        echo "unsupported platform: $(uname -s)" >&2
        exit 1
        ;;
esac

# Temporary files rather than process substitution: <(...) is not POSIX, and
# /bin/sh is dash on Debian and a POSIX-mode bash on macOS. This script has to
# run on both.
TMP=$(mktemp -d)
trap 'rm -rf "$TMP"' EXIT INT TERM
printf '%s\n' "$WANT" | awk 'NF' | sort -u > "$TMP/want"
printf '%s\n' "$HAVE" | awk 'NF' | sort -u > "$TMP/have"
MISSING=$(comm -23 "$TMP/want" "$TMP/have")
EXTRA=$(comm -13 "$TMP/want" "$TMP/have")
WANT=$(cat "$TMP/want")
HAVE=$(cat "$TMP/have")

count() { printf '%s\n' "$1" | awk 'NF' | wc -l | tr -d ' '; }

case "${1:-check}" in
    check)
        echo "role: $ROLE   wanted: $(count "$WANT")   installed: $(count "$HAVE")"
        echo
        echo "missing ($(count "$MISSING")):"
        printf '%s\n' "$MISSING" | awk 'NF' | sed 's/^/  /'
        echo
        echo "extra, not touched ($(count "$EXTRA")):"
        printf '%s\n' "$EXTRA" | awk 'NF' | sed 's/^/  /'
        ;;
    install)
        if [ -z "$(printf '%s\n' "$MISSING" | awk 'NF')" ]; then
            echo "nothing to install"
            exit 0
        fi
        echo "installing:"
        printf '%s\n' "$MISSING" | awk 'NF' | sed 's/^/  /'
        # shellcheck disable=SC2086
        $INSTALL $(printf '%s ' $MISSING)
        ;;
    *)
        echo "usage: $0 [check|install]" >&2
        exit 1
        ;;
esac