#!/usr/bin/env bash
# `scripts/bus-service.sh render|install|uninstall|status [<business>]`:
# the systemd user unit that supervises `scripts/mosaic bus start <business>`
# (lead decision 70). The template is
# packages/cli/systemd/mosaic-bus.service.in; the rendered unit is
# mosaic-bus@.service in the systemd user directory, one instance per
# business (mosaic-bus@<business>). Nothing here reads a capability, the
# binding or the token. See packages/cli/README.md, "Bus host".
#
#   render [--claude PATH]       print the rendered unit on stdout
#   install [--dir DIR] [--no-reload] [--claude PATH]
#                                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 <business>            unit state, then `mosaic bus status`
#
# --claude PATH pins the Claude Code binary the unit's sessions run
# (MOSAIC_CLAUDE_BIN); without it, `command -v claude` here. The path is
# kept as given, so a symlink that tracks updates keeps tracking them.
#
# Exit codes: 0 ok, 1 operation failed, 4 usage.
set -euo pipefail
REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
TEMPLATE="$REPO/packages/cli/systemd/mosaic-bus.service.in"
UNIT_NAME="mosaic-bus@.service"
USAGE="usage: scripts/bus-service.sh render [--claude PATH] | install [--dir DIR] [--no-reload] [--claude PATH] | uninstall [--dir DIR] [--no-reload] | status <business>"

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

CLAUDE_BIN=""
CLAUDE_SET=0

# The unit's MOSAIC_CLAUDE_BIN line, or a comment when there is no claude to
# pin. systemd expands % and splits Environment= on spaces, so the path is
# held to a plain character set.
claude_line() {
    local bin
    if [ "$CLAUDE_SET" = 1 ]; then
        bin="$CLAUDE_BIN"
    else
        bin="$(command -v claude || true)"
        if [ -z "$bin" ]; then
            echo "bus-service: no claude on PATH; MOSAIC_CLAUDE_BIN left unset (--claude PATH pins one)" >&2
            echo "# MOSAIC_CLAUDE_BIN unset: no claude on PATH at install time"
            return 0
        fi
    fi
    case "$bin" in /*) ;; *) die "claude path must be absolute: $bin" ;; esac
    case "$bin" in *[!A-Za-z0-9/._+-]*) die "claude path contains a character the unit cannot carry: $bin" ;; esac
    [ -f "$bin" ] && [ -x "$bin" ] || die "claude path is not an executable file: $bin"
    echo "Environment=MOSAIC_CLAUDE_BIN=$bin"
}

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: $REPO" ;; esac
    local claude
    claude="$(claude_line)" || exit 1
    sed -e "s|@REPO@|$REPO|g" -e "s|@PATH@|$path|g" -e "s|^@CLAUDE_ENV@$|$claude|" "$TEMPLATE"
}

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 ;;
            --claude) [ $# -ge 2 ] || usage; CLAUDE_BIN="$2"; CLAUDE_SET=1; shift 2 ;;
            *) usage ;;
        esac
    done
}

install_unit() {
    parse_flags "$@"
    mkdir -p "$UNIT_DIR"
    local target="$UNIT_DIR/$UNIT_NAME" tmp unit
    unit="$(render)" || exit 1
    tmp="$(mktemp "$UNIT_DIR/.$UNIT_NAME.XXXXXX")"
    printf '%s\n' "$unit" > "$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: $target"
    fi
    local bin
    bin="$(sed -n 's/^Environment=MOSAIC_CLAUDE_BIN=//p' "$target")"
    if [ -n "$bin" ]; then
        echo "claude: $bin ($("$bin" --version 2>/dev/null | head -n 1 || true))"
    else
        echo "claude: MOSAIC_CLAUDE_BIN unset; sessions run claude from the unit's PATH"
    fi
    if [ "$RELOAD" = 1 ]; then
        systemctl --user daemon-reload || die "daemon-reload failed"
        echo "daemon-reload done"
    fi
    cat <<MSG
next, for one business (one per data root):
  mkdir -m 0700 -p <dataRoot>/notify/<business>               the notifier refuses a looser directory
  write <dataRoot>/notify/<business>/notify.json, mode 0600:
    {"notifyVersion": 1, "binding": "<discord binding>"}   or "binding": null for no DMs
  systemctl --user enable --now mosaic-bus@<business>      start now and at login
  systemctl --user status mosaic-bus@<business>
  journalctl --user -u mosaic-bus@<business> -f             the host's log
  systemctl --user stop mosaic-bus@<business>               SIGTERM; restartable
survive logout and reboot only with lingering on: loginctl enable-linger ${USER:-$(id -un)}
MSG
}

uninstall_unit() {
    parse_flags "$@"
    [ "$CLAUDE_SET" = 0 ] || usage
    local target="$UNIT_DIR/$UNIT_NAME"
    if [ "$RELOAD" = 1 ]; then
        local active
        active="$(systemctl --user list-units --no-legend --plain 'mosaic-bus@*' 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 business="$1"
    case "$business" in ''|*[!a-z0-9-]*) die "business id must be [a-z0-9-]+" ;; esac
    local unit="mosaic-bus@$business.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 "$unit" -p MainPID -p NRestarts -p ExecMainStartTimestamp -p Result -p Environment 2>/dev/null | sed 's/^/  /'
    "$REPO/scripts/mosaic" bus status | sed 's/^/  /' || true
}

[ $# -ge 1 ] || usage
cmd="$1"; shift
case "$cmd" in
    render)
        while [ $# -gt 0 ]; do
            case "$1" in
                --claude) [ $# -ge 2 ] || usage; CLAUDE_BIN="$2"; CLAUDE_SET=1; shift 2 ;;
                *) usage ;;
            esac
        done
        render ;;
    install) install_unit "$@" ;;
    uninstall) uninstall_unit "$@" ;;
    status) status_unit "$@" ;;
    -h|--help) echo "$USAGE" ;;
    *) usage ;;
esac