#!/bin/bash
#
# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# 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.
#
# The global git config, for the drawer's git page.
#
#   gitcfg list                    git config --global -z --list
#   gitcfg set <key> <old> <new>   replace the one value equal to <old>
#   gitcfg add <key> <value>       add a value
#   gitcfg unset <key> <value>     remove the one value equal to <value>
#
# Every write goes through git config, so the file keeps its comments, layout
# and quoting. --fixed-value makes a value a literal rather than a regex, so a
# write touches one value of a multi-valued key, and the `--` before the key
# keeps a leading dash an argument rather than an option.
#
# A write prints nothing on success. On failure it prints the reason on
# stdout, for the page, and exits 1.

set -u

usage() {
    printf 'usage: %s list | set <key> <old> <new> | add <key> <value> | unset <key> <value>\n' \
           "${0##*/}" >&2
    exit 2
}

g() {
    local err
    err="$(git config --global "$@" 2>&1)" || { printf '%s\n' "${err:-git config failed}"; exit 1; }
}

# --replace-all with no value equal to <old> appends <new> and succeeds, and
# --unset of a missing value fails silently, so both check first: the file
# may have changed in the editor since the page read it.
has() {
    git config --global --fixed-value --get-all -- "$1" "$2" >/dev/null \
        || { printf '%s no longer holds that value\n' "$1"; exit 1; }
}

case "${1:-}" in
    list)  [[ $# -eq 1 ]] || usage; exec git config --global -z --list ;;
    set)   [[ $# -eq 4 ]] || usage; has "$2" "$3"; g --fixed-value --replace-all -- "$2" "$4" "$3" ;;
    add)   [[ $# -eq 3 ]] || usage; g --add -- "$2" "$3" ;;
    unset) [[ $# -eq 3 ]] || usage; has "$2" "$3"; g --fixed-value --unset -- "$2" "$3" ;;
    *)     usage ;;
esac