#!/usr/bin/env bash
set -Eeuo pipefail
IFS=$'\n\t'

readonly PROGRAM="ochenstarik-smm-emergency"
readonly STATE_DIR="/var/lib/ochenstarik-server-monitor-manager"
readonly ETC_DIR="/etc/ochenstarik-server-monitor-manager"
readonly MARKER="$STATE_DIR/mesh/emergency-disabled"
readonly CONTROL_UNIT="ochenstarik-smm-control.service"
readonly AGENT_UNIT="ochenstarik-smm-agent.service"
readonly FIREWALL_UNIT="ochenstarik-smm-firewall.service"
readonly WIREGUARD_UNIT="wg-quick@smm0.service"
readonly NFT_FAMILY="inet"
readonly NFT_TABLE="ochenstarik_smm"

fail() { printf '%s: %s\n' "$PROGRAM" "$*" >&2; exit 78; }
log() { printf '%s: %s\n' "$PROGRAM" "$*"; }

usage() {
    cat <<'EOF'
Local Server Monitor Manager emergency recovery

Usage:
  ochenstarik-smm-emergency status
  ochenstarik-smm-emergency mesh-disable
  ochenstarik-smm-emergency mesh-enable
  ochenstarik-smm-emergency firewall-restore

Commands use only Server Monitor Manager-owned units, interface and nftables
table. They do not modify the host SSH service or unrelated firewall rules.
EOF
}

require_root() {
    [[ ${EUID:-$(id -u)} -eq 0 ]] || fail "this action must run as root (use sudo)"
}

unit_state() {
    local unit="$1"
    if systemctl list-unit-files "$unit" --no-legend 2>/dev/null | grep -q "^$unit"; then
        systemctl is-active "$unit" 2>/dev/null || true
    else
        printf '%s\n' "not-installed"
    fi
}

show_status() {
    local unit
    for unit in "$CONTROL_UNIT" "$AGENT_UNIT" "$FIREWALL_UNIT" "$WIREGUARD_UNIT"; do
        printf '%s: %s\n' "$unit" "$(unit_state "$unit")"
    done
    if command -v ip >/dev/null 2>&1 && ip link show smm0 >/dev/null 2>&1; then
        printf '%s\n' "mesh-interface: present"
    else
        printf '%s\n' "mesh-interface: absent"
    fi
    if command -v nft >/dev/null 2>&1 && nft list table "$NFT_FAMILY" "$NFT_TABLE" >/dev/null 2>&1; then
        printf '%s\n' "mesh-firewall: loaded"
    else
        printf '%s\n' "mesh-firewall: absent"
    fi
    [[ -f "$MARKER" ]] && printf '%s\n' "emergency-lock: active" || printf '%s\n' "emergency-lock: inactive"
    printf '%s\n' "backups:"
    find "$STATE_DIR/bootstrap-backups" -maxdepth 1 -type f \
        \( -name '*.tar.gz' -o -name '*.empty' \) -printf '  %f\n' 2>/dev/null | sort -r | head -n 10 || true
}

delete_project_firewall() {
    if command -v nft >/dev/null 2>&1; then
        nft delete table "$NFT_FAMILY" "$NFT_TABLE" 2>/dev/null || true
    fi
}

mesh_disable() {
    require_root
    systemctl disable --now "$WIREGUARD_UNIT" 2>/dev/null || true
    systemctl disable --now "$FIREWALL_UNIT" 2>/dev/null || true
    delete_project_firewall
    install -d -m 0700 "$(dirname "$MARKER")"
    printf '%s\n' "$(date -u +%Y-%m-%dT%H:%M:%SZ)" >"$MARKER"
    chmod 0600 "$MARKER"
    log "Mesh disabled locally; Control and SSH were not changed."
}

restore_project_firewall() {
    require_root
    [[ -f "$ETC_DIR/mesh.nft" ]] || fail "managed firewall configuration is missing"
    command -v nft >/dev/null 2>&1 || fail "nft is unavailable"
    if ! nft list table "$NFT_FAMILY" "$NFT_TABLE" >/dev/null 2>&1; then
        nft --check -f "$ETC_DIR/mesh.nft"
    fi
    delete_project_firewall
    if ! nft -f "$ETC_DIR/mesh.nft"; then
        systemctl disable --now "$WIREGUARD_UNIT" 2>/dev/null || true
        fail "managed firewall restore failed; Mesh was disabled to fail closed"
    fi
    if systemctl list-unit-files "$FIREWALL_UNIT" --no-legend 2>/dev/null | grep -q "^$FIREWALL_UNIT"; then
        systemctl enable "$FIREWALL_UNIT" >/dev/null
    fi
    log "Base deny-by-default Mesh firewall restored; Control must reconcile active Links."
}

mesh_enable() {
    require_root
    [[ -f /etc/wireguard/smm0.conf ]] || fail "WireGuard smm0 configuration is missing"
    if [[ -f "$ETC_DIR/mesh.nft" ]]; then
        restore_project_firewall
    fi
    systemctl enable "$WIREGUARD_UNIT" >/dev/null
    systemctl restart "$WIREGUARD_UNIT"
    rm -f -- "$MARKER"
    log "Mesh enabled locally."
}

main() {
    local action="${1:-help}"
    shift || true
    [[ $# -eq 0 ]] || fail "unexpected arguments"
    case "$action" in
        help|-h|--help) usage ;;
        status) show_status ;;
        mesh-disable) mesh_disable ;;
        mesh-enable) mesh_enable ;;
        firewall-restore) restore_project_firewall ;;
        *) fail "unknown action: $action" ;;
    esac
}

main "$@"