#!/usr/bin/env bash
# `scripts/discord-service.sh render|install|uninstall|status [<binding>]`:
# the systemd user unit that supervises `scripts/discord.sh run <binding>`.
# The template is packages/discord/systemd/mosaic-discord@.service.in; the
# rendered unit is mosaic-discord@.service in the systemd user directory, one
# instance per binding (mosaic-discord@<binding>). Nothing here reads the
# binding or the token. See packages/discord/README.md, "Service unit".
#
#   render                       print the rendered unit on stdout
#   install [--dir DIR] [--no-reload]
#                                write the unit (write to a temp file, then
#                                rename) and run `systemctl --user daemon-reload`
#   uninstall [--dir DIR] [--no-reload]
#                                remove the unit; refuses while an instance is active
#   status <binding>             unit state, STOP and run.lock for one binding
#
# Exit codes: 0 ok, 1 operation failed, 4 usage.
set -euo pipefail
REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
TEMPLATE="$REPO/packages/discord/systemd/mosaic-discord@.service.in"
UNIT_NAME="mosaic-discord@.service"
USAGE="usage: scripts/discord-service.sh render | install [--dir DIR] [--no-reload] | uninstall [--dir DIR] [--no-reload] | status <binding>"

die() { echo "discord-service: $*" >&2; exit 1; }
usage() { echo "$USAGE" >&2; exit 4; }

render() {
    [ -f "$TEMPLATE" ] || die "template missing: $TEMPLATE"
    local node_dir
    node_dir="$(dirname "$(command -v node || true)")"
    [ -n "$node_dir" ] && [ "$node_dir" != "." ] || die "node not found on PATH"
    local path="/usr/local/bin:/usr/bin:/bin"
    case ":$path:" in *":$node_dir:"*) ;; *) path="$node_dir:$path" ;; esac
    case "$REPO" in *@*|*'|'*) die "repository path contains a character the template cannot carry: $REPO" ;; esac
    sed -e "s|@REPO@|$REPO|g" -e "s|@PATH@|$path|g" "$TEMPLATE"
}

# Parse --dir and --no-reload for install and uninstall.
UNIT_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user"
RELOAD=1
parse_flags() {
    while [ $# -gt 0 ]; do
        case "$1" in
            --dir) [ $# -ge 2 ] || usage; UNIT_DIR="$2"; shift 2 ;;
            --no-reload) RELOAD=0; shift ;;
            *) usage ;;
        esac
    done
}

install_unit() {
    parse_flags "$@"
    mkdir -p "$UNIT_DIR"
    local target="$UNIT_DIR/$UNIT_NAME" tmp
    tmp="$(mktemp "$UNIT_DIR/.$UNIT_NAME.XXXXXX")"
    render > "$tmp"
    chmod 0644 "$tmp"
    if [ -f "$target" ] && cmp -s "$tmp" "$target"; then
        rm -f "$tmp"
        echo "unchanged: $target"
    else
        mv -f "$tmp" "$target"
        echo "written: $target"
    fi
    if [ "$RELOAD" = 1 ]; then
        systemctl --user daemon-reload || die "daemon-reload failed"
        echo "daemon-reload done"
    fi
    cat <<MSG
next, for one binding:
  systemctl --user enable --now mosaic-discord@<binding>   start now and at login
  systemctl --user status mosaic-discord@<binding>
  journalctl --user -u mosaic-discord@<binding> -f          the connector's log
  systemctl --user stop mosaic-discord@<binding>            SIGTERM; restartable
  scripts/discord.sh stop <binding>                         the brake: writes STOP, the unit stays down until STOP is removed
survive logout and reboot only with lingering on: loginctl enable-linger $USER
MSG
}

uninstall_unit() {
    parse_flags "$@"
    local target="$UNIT_DIR/$UNIT_NAME"
    if [ "$RELOAD" = 1 ]; then
        local active
        active="$(systemctl --user list-units --no-legend --plain 'mosaic-discord@*' 2>/dev/null | awk '$3 == "active" || $3 == "activating" || $3 == "deactivating" {print $1}')"
        [ -z "$active" ] || die "refusing: instance(s) still running: $(echo "$active" | tr '\n' ' ')stop them first"
    fi
    if [ -f "$target" ]; then
        rm -f "$target"
        echo "removed: $target"
    else
        echo "absent: $target"
    fi
    if [ "$RELOAD" = 1 ]; then
        systemctl --user daemon-reload || die "daemon-reload failed"
        echo "daemon-reload done"
    fi
}

status_unit() {
    [ $# -eq 1 ] || usage
    local binding="$1"
    case "$binding" in ''|*[!A-Za-z0-9_-]*) die "binding name must be [A-Za-z0-9_-]+" ;; esac
    local unit="mosaic-discord@$binding.service"
    echo "unit: $unit"
    echo "  enabled: $(systemctl --user is-enabled "$unit" 2>&1 || true)"
    echo "  active:  $(systemctl --user is-active "$unit" 2>&1 || true)"
    systemctl --user show "$unit" -p MainPID -p NRestarts -p ExecMainStartTimestamp -p Result 2>/dev/null | sed 's/^/  /'
    local config="${XDG_CONFIG_HOME:-$HOME/.config}/mosaic-dev/config.json"
    local data_root
    data_root="$(node -e 'const c=JSON.parse(require("fs").readFileSync(process.argv[1],"utf8")); process.stdout.write(String(c.dataRoot||""))' "$config" 2>/dev/null || true)"
    if [ -z "$data_root" ]; then
        echo "  journal: dataRoot not readable from $config"
        return 0
    fi
    data_root="${data_root/#\~/$HOME}"
    local dir="$data_root/discord/$binding"
    if [ -f "$dir/STOP" ]; then
        echo "  STOP: present ($(tail -n 1 "$dir/STOP"))"
    else
        echo "  STOP: absent"
    fi
    if [ -d "$dir/run.lock" ]; then
        echo "  run.lock: present$( [ -f "$dir/run.lock/owner.json" ] && printf ' (owner pid %s)' "$(node -e 'process.stdout.write(String(JSON.parse(require("fs").readFileSync(process.argv[1],"utf8")).pid))' "$dir/run.lock/owner.json" 2>/dev/null || echo '?')" )"
    else
        echo "  run.lock: absent"
    fi
}

[ $# -ge 1 ] || usage
cmd="$1"; shift
case "$cmd" in
    render) [ $# -eq 0 ] || usage; render ;;
    install) install_unit "$@" ;;
    uninstall) uninstall_unit "$@" ;;
    status) status_unit "$@" ;;
    -h|--help) echo "$USAGE" ;;
    *) usage ;;
esac