#!/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 [--copy ID [--copies DIR]] [--pm] [--claude PATH] | install [--copy ID [--copies DIR]] [--pm] [--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
COPY_ID=""
COPIES="${XDG_DATA_HOME:-$HOME/.local/share}/mosaic-stack/copies"
PM=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: $TEMPLATE"
    local root="$REPO"
    if [ -n "$COPY_ID" ]; then
        [[ "$COPY_ID" =~ ^[0-9a-f]{40}$ ]] || die "--copy must be a full 40-character commit id"
        case "$COPIES" in /*) ;; *) die "copies directory must be absolute" ;; esac
        case "$COPIES" in *[!A-Za-z0-9/._+-]*) die "copies directory contains a character the unit cannot carry" ;; esac
        root="$COPIES/$COPY_ID"
        [ -f "$root/scripts/mosaic" ] || die "no copy $COPY_ID in $COPIES"
    fi
    local pm_flags=""
    [ "$PM" = 0 ] || pm_flags=" --pm"
    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@|$root|g" -e "s|@PATH@|$path|g" -e "s|@PM_FLAGS@|$pm_flags|g" -e "s|^@CLAUDE_ENV@$|$claude|" "$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 ;;
            --copy) [ $# -ge 2 ] || usage; COPY_ID="$2"; shift 2 ;;
            --copies) [ $# -ge 2 ] || usage; COPIES="$2"; shift 2 ;;
            --pm) PM=1; shift ;;
            --claude) [ $# -ge 2 ] || usage; CLAUDE_BIN="$2"; CLAUDE_SET=1; shift 2 ;;
            *) usage ;;
        esac
    done
}

# Inspect effective unit metadata: drop-ins can override the installed template.
# Any failed read refuses before a write, including --no-reload installations.
install_guard() {
    local out unit file
    out="$(systemctl --user list-units --all --no-legend --plain 'mosaic-bus@*.service' 2>/dev/null)" || die "refusing: systemctl --user list-units failed, so the bus state is unknown; nothing was changed"
    while read -r unit load state rest; do
        [[ "$unit" == mosaic-bus@*.service ]] || continue
        case "$state" in inactive|failed) ;; *) die "refusing: $unit is running ($state); Jason or Mos stops it first, then install, then start it" ;; esac
    done <<< "$out"
    # systemctl show rejects a template name. The lookup-path scan also
    # covers stopped/unloaded instances that list-units does not enumerate.
    local paths directory dropdir content
    paths="$(systemd-analyze --user unit-paths 2>/dev/null)" || die "refusing: systemd-analyze --user unit-paths failed; drop-in paths are unknown; nothing was changed"
    [ -n "$paths" ] || die "refusing: systemd unit paths are unknown; nothing was changed"
    while IFS= read -r directory; do
        [ -n "$directory" ] || continue
        case "$directory" in /*) ;; *) die "refusing: invalid systemd unit path $directory; nothing was changed" ;; esac
        [ -e "$directory" ] || [ -L "$directory" ] || continue
        [ -d "$directory" ] && [ -r "$directory" ] && [ -x "$directory" ] || die "refusing: cannot inspect unit path $directory; nothing was changed"
        # * includes the empty instance, i.e. mosaic-bus@.service.d.
        for dropdir in "$directory"/mosaic-bus@*.service.d; do
            [ -e "$dropdir" ] || [ -L "$dropdir" ] || continue
            [ -d "$dropdir" ] && [ -r "$dropdir" ] && [ -x "$dropdir" ] || die "refusing: cannot inspect drop-ins $dropdir; nothing was changed"
            for file in "$dropdir"/*.conf; do
                [ -e "$file" ] || [ -L "$file" ] || continue
                content="$(cat "$file" 2>/dev/null)" || die "refusing: cannot read drop-in $file; nothing was changed"
                if grep -Eq '^[[:space:]]*(ExecStart|WorkingDirectory)[[:space:]]*=' <<< "$content"; then
                    die "refusing: drop-in $file overrides ExecStart or WorkingDirectory; Mos removes it first and reloads systemd"
                fi
            done
        done
    done <<< "$paths"
}

install_unit() {
    parse_flags "$@"
    install_guard
    mkdir -p "$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 ] && [ -z "$COPY_ID" ] && [ "$PM" = 0 ] || usage
    local target="$UNIT_DIR/$UNIT_NAME"
    local out active
    out="$(systemctl --user list-units --all --no-legend --plain 'mosaic-bus@*.service' 2>/dev/null)" || die "refusing: systemctl read failed; nothing was changed"
    active="$(awk '$3 != "inactive" && $3 != "failed" {print $1}' <<< "$out")"
    [ -z "$active" ] || die "refusing: instance(s) still running: $active; Jason or Mos stops them first"
    if [ -f "$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 "$unit" -p MainPID -p NRestarts -p ExecMainStartTimestamp -p Result -p Environment 2>/dev/null | sed 's/^/  /'
    local effective root exec_start drops copy=checkout
    effective="$(systemctl --user show "$unit" -p LoadState -p WorkingDirectory -p ExecStart -p DropInPaths 2>/dev/null)" || die "cannot read effective unit $unit"
    root="$(sed -n 's/^WorkingDirectory=//p' <<< "$effective")"
    exec_start="$(sed -n 's/^ExecStart=//p' <<< "$effective")"
    drops="$(sed -n 's/^DropInPaths=//p' <<< "$effective")"
    if [[ "${root##*/}" =~ ^[0-9a-f]{40}$ ]] && [ -f "$root/scripts/mosaic" ];then copy="${root##*/}";fi
    echo "tree: ${root:-absent}"
    echo "copy: $copy"
    if [[ "$exec_start" =~ [[:space:]]--pm([[:space:];]|$) ]];then echo 'pm: on';else echo 'pm: off';fi
    echo "drop-ins: ${drops:-none}"
    local head
    head="$(git -C "$REPO" rev-parse refs/heads/refactor 2>/dev/null || true)"
    if [ "$copy" != checkout ] && [ "$head" != "$copy" ];then echo "refactor: ${head:-unknown} (another commit)";else echo "refactor: ${head:-unknown}";fi
    "$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
                --copy) [ $# -ge 2 ] || usage; COPY_ID="$2"; shift 2 ;;
                --copies) [ $# -ge 2 ] || usage; COPIES="$2"; shift 2 ;;
                --pm) PM=1; shift ;;
                --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