# `router-setup`: the generic installer. Asks for the basics on the console
# (disk, uplink and LAN interfaces, PPPoE credentials, LAN address, web UI
# password), writes them as settings.json, builds that router on the spot
# (offline: the closure of `reference` brings the sources and everything the
# build needs) and installs it with `router-install`. Everything else is done
# in the web UI afterwards.
{
  config,
  lib,
  pkgs,
  ...
}:
let
  cfg = config.router.setup;
  webui = pkgs.callPackage ../../pkgs/router-webui/package.nix { };

  setup = pkgs.writeShellApplication {
    name = "router-setup";
    runtimeInputs = [
      config.nix.package
      webui
      pkgs.coreutils
      pkgs.gawk
      pkgs.gnugrep
      pkgs.jq
      pkgs.mkpasswd
      pkgs.util-linux
      "/run/current-system/sw"
    ];
    text = ''
      usage() {
        echo "usage: router-setup [--local FILE]" >&2
        echo "  Asks a few questions, then ERASES the chosen disk and installs the router." >&2
        echo "  --local FILE  extra NixOS module for this box (installed as config/local.nix)" >&2
        exit 2
      }
      local_nix=""
      while [ $# -gt 0 ]; do
        case $1 in
          --local) shift; [ $# -gt 0 ] || usage; local_nix=$1 ;;
          *) usage ;;
        esac
        shift
      done
      [ "$(id -u)" -eq 0 ] || { echo "router-setup: must run as root" >&2; exit 1; }

      # ask VAR PROMPT [DEFAULT]
      # (Their locals must not share a name with the caller's variable.)
      ask() {
        local reply
        read -r -p "$2''${3:+ [$3]}: " reply || { echo; echo "aborted" >&2; exit 1; }
        printf -v "$1" '%s' "''${reply:-''${3:-}}"
      }
      ask_secret() {
        local reply
        read -r -s -p "$2: " reply || { echo; echo "aborted" >&2; exit 1; }
        echo >&2
        printf -v "$1" '%s' "$reply"
      }
      # choose VAR PROMPT ITEM...: by number or by name
      choose() {
        local var=$1 prompt=$2 pick="" i
        shift 2
        while :; do
          i=1
          for item in "$@"; do echo "  $i) $item" >&2; i=$((i + 1)); done
          ask pick "$prompt"
          if [[ $pick =~ ^[0-9]+$ ]] && [ "$pick" -ge 1 ] && [ "$pick" -le $# ]; then
            pick=''${!pick}
            pick=''${pick%% *}
          fi
          for item in "$@"; do
            if [ "''${item%% *}" = "$pick" ]; then
              printf -v "$var" '%s' "$pick"
              return
            fi
          done
          echo "  please pick one of the above" >&2
        done
      }
      ipv4_ok() {
        [[ $1 =~ ^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$ ]] || return 1
        for o in "''${BASH_REMATCH[@]:1}"; do [ "$o" -le 255 ] || return 1; done
      }

      # Set by ask/choose (printf -v).
      disk="" wan="" lan="" wan_type="" host="" lan_address="" ssh_key="" answer=""
      webui_password="" webui_password2=""

      echo
      echo "nixos-router setup"
      echo "=================="
      echo "A few questions; everything else can be changed later in the web UI."
      echo

      # Disks, without the medium this installer runs from.
      boot_disk=""
      if src=$(findmnt -no SOURCE /iso 2>/dev/null) && [ -n "$src" ]; then
        boot_disk=/dev/$(lsblk -no PKNAME "$src" | head -n1)
      fi
      mapfile -t disks < <(lsblk -dnpo NAME,SIZE,MODEL,TYPE | awk '$NF == "disk" { $NF = ""; print }' \
        | grep -v "^$boot_disk " || true)
      [ ''${#disks[@]} -gt 0 ] || { echo "router-setup: no disk to install to" >&2; exit 1; }
      echo "Disk to install to (it will be ERASED):"
      choose disk "Disk" "''${disks[@]}"

      nics=()
      for dev in /sys/class/net/*; do
        n=$(basename "$dev")
        [ -e "$dev/device" ] || continue
        state=$(cat "$dev/operstate" 2>/dev/null || echo "?")
        nics+=("$n  $(cat "$dev/address")  link $state")
      done
      [ ''${#nics[@]} -gt 0 ] || { echo "router-setup: no network interfaces found" >&2; exit 1; }
      echo
      echo "Interface towards the internet (WAN):"
      choose wan "WAN interface" "''${nics[@]}"
      echo
      echo "Interface for the local network (LAN):"
      choose lan "LAN interface" "''${nics[@]}"

      echo
      echo "Internet connection:"
      choose wan_type "Connection" \
        "dhcp   (behind a cable modem, an ONT or another router)" \
        "pppoe  (DSL or fibre with a username and password)"
      pppoe_user="" pppoe_password="" pppoe_vlan=""
      if [ "$wan_type" = pppoe ]; then
        while [ -z "$pppoe_user" ]; do ask pppoe_user "PPPoE username"; done
        while [ -z "$pppoe_password" ]; do ask_secret pppoe_password "PPPoE password"; done
        while :; do
          ask pppoe_vlan "VLAN ID the provider requires (empty for none)" ""
          [ -z "$pppoe_vlan" ] && break
          [[ $pppoe_vlan =~ ^[0-9]+$ ]] && [ "$pppoe_vlan" -ge 1 ] && [ "$pppoe_vlan" -le 4094 ] && break
          echo "  a number from 1 to 4094" >&2
        done
      fi
      if [ "$wan" = "$lan" ] && [ -z "$pppoe_vlan" ]; then
        echo "router-setup: WAN and LAN can only share an interface when PPPoE runs on a VLAN" >&2
        exit 1
      fi

      echo
      ask host "Host name" "router"
      while :; do
        ask lan_address "Router address on the LAN (a /24 network)" "192.168.1.1"
        ipv4_ok "$lan_address" && break
        echo "  an IPv4 address like 192.168.1.1" >&2
      done
      net=''${lan_address%.*}

      echo
      echo "Password for the web UI and for root on the console (at least 8 characters):"
      while :; do
        ask_secret webui_password "Password"
        ask_secret webui_password2 "Again"
        [ "$webui_password" = "$webui_password2" ] && [ ''${#webui_password} -ge 8 ] && break
        echo "  the passwords differ or are too short" >&2
      done
      ask ssh_key "SSH public key for root (optional, one line)" ""

      echo
      echo "Summary"
      echo "  disk:      $disk (will be erased)"
      echo "  WAN:       $wan, $wan_type''${pppoe_user:+ as $pppoe_user}''${pppoe_vlan:+ on VLAN $pppoe_vlan}"
      echo "  LAN:       $lan, $lan_address/24, DHCP $net.100 - $net.200"
      echo "  host name: $host"
      echo "  web UI:    https://$lan_address"
      ask answer "Type the disk name ($disk) to install"
      [ "$answer" = "$disk" ] || { echo "aborted" >&2; exit 1; }

      work=$(mktemp -d /run/router-setup.XXXXXX)
      chmod 0700 "$work"
      trap 'rm -rf "$work"' EXIT
      mkdir -p "$work/secrets/config"
      config=$work/secrets/config
      cp ${cfg.flake} "$config/flake.nix"
      chmod 0644 "$config/flake.nix"
      if [ -n "$local_nix" ]; then cp "$local_nix" "$config/local.nix"; fi

      keys=$( [ -n "$ssh_key" ] && jq -n --arg k "$ssh_key" '[$k]' || echo '[]')
      jq -n \
        --arg host "$host" --arg state "${cfg.stateVersion}" --argjson keys "$keys" \
        --arg wan "$wan" --arg type "$wan_type" --arg user "$pppoe_user" --arg vlan "$pppoe_vlan" \
        --arg lan "$lan" --arg addr "$lan_address" --arg net "$net" '
        {
          system: { hostName: $host, stateVersion: $state, sshKeys: $keys },
          router: {
            wan: ({ interface: $wan, ipv4: { type: $type } }
              | if $type == "pppoe" then .ipv4.pppoe = ({ username: $user, passwordFile: "/var/lib/router/pppoe-password" }
                  + (if $vlan == "" then {} else { vlan: ($vlan | tonumber) } end)) else . end),
            lans: {
              lan: {
                interface: $lan, internet: true,
                ipv4: { address: $addr },
                dhcp: { pool: { start: ($net + ".100"), end: ($net + ".200") } }
              }
            }
          }
        }' > "$config/settings.json"

      if [ "$wan_type" = pppoe ]; then
        printf '%s' "$pppoe_password" > "$work/secrets/pppoe-password"
      fi
      printf '%s\n' "$webui_password" | router-webui passwd "$work/secrets/webui-password"
      (umask 077; printf '%s\n' "$webui_password" | mkpasswd -s > "$work/secrets/root-password")

      echo
      echo ">> building the router system (no internet needed; takes a few minutes)"
      system=$(nix build --no-link --print-out-paths --out-link "$work/system" \
        "path:$config#nixosConfigurations.router.config.system.build.toplevel")
      router-install --yes --secrets "$work/secrets" --system "$system" "$disk"
      echo
      echo "After rebooting, open https://$lan_address from the LAN."
    '';
  };
in
{
  imports = [ ./install-script.nix ];

  options.router.setup = {
    flake = lib.mkOption {
      type = lib.types.path;
      description = "The configuration flake (flake.nix) installed systems are built from.";
    };
    reference = lib.mkOption {
      type = lib.types.package;
      description = ''
        A router system built the same way (`lib.mkRouterSystem`). Its closure
        is what lets the installer build the chosen configuration offline.
      '';
    };
    stateVersion = lib.mkOption {
      type = lib.types.str;
      default = config.system.nixos.release;
      description = "system.stateVersion of installed routers.";
    };
  };

  config = {
    environment.systemPackages = [ setup ];
    system.extraDependencies = [ cfg.reference ];
    nix.settings.experimental-features = [
      "nix-command"
      "flakes"
    ];
  };
}