# inspired from https://nixos.wiki/wiki/Virtualization_in_NixOS
{ config, pkgs, lib, ... }@args:
let
  pools = {
    niximages = {
      type = "dir";
      target = "/etc/libvirtd/base-images";
    };
    buildbot-disks = rec {
      preStart = ''
        mkdir -p ${target}
      '';
      type = "dir";
      target = "/var/lib/libvirt/images/buildbot-disks";
    };
    zfspool = {
      # pool-define-as --name zfspool --source-name zpool/libvirt --type zfs
      type = "zfs";
      xml = ''
        <source>
          <name>zpool/libvirt</name>
        </source>
      '';
    };
  };
  networks = {
    immae = {
      bridgeNumber = "1";
      ipRange = "192.168.100";
    };
  };
  guests = {
    caldance = {
      pool = "zfspool";
      cpus = "1";
      memory = "2";
      network = "immae";
      diskSize = "10GiB";
      extraDevicesXML = ''
        <filesystem type="mount">
          <source dir="/var/lib/caldance"/>
          <target dir="home"/>
        </filesystem>
      '';
    };
    buildbot = {
      pool = "zfspool";
      cpus = "1";
      memory = "3";
      network = "immae";
      diskSize = "10GiB";
      destroyVolumeOnExit = true;
    };
  };
  toImage = f: "${import ./vms/base_image.nix f (args // { myEnv = config.myEnv; })}/nixos.qcow2";
in
{
  environment.etc."libvirtd/base-images/nixos.qcow2".source = toImage ./vms/base_configuration.nix;
  environment.etc."libvirtd/base-images/buildbot.qcow2".source = toImage ./vms/buildbot_configuration.nix;
  systemd.services = lib.mapAttrs' (name: guest: lib.nameValuePair "libvirtd-guest-${name}" {
    after = [ "libvirtd.service" "libvirtd-pool-${guest.pool}.service" "libvirtd-network-${guest.network}.service" ];
    requires = [ "libvirtd.service" "libvirtd-pool-${guest.pool}.service" "libvirtd-network-${guest.network}.service" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = "yes";
    };
    script =
      let
        xml = pkgs.writeText "libvirt-guest-${name}.xml"
        ''
          <domain type="kvm">
            <name>${name}</name>
            <uuid>UUID</uuid>
            <memory unit="GiB">${guest.memory}</memory>
            <vcpu>${guest.cpus}</vcpu>
            <os>
              <type arch="x86_64">hvm</type>
            </os>
            <devices>
              <emulator>/run/current-system/sw/bin/qemu-system-x86_64</emulator>
              <disk type="volume">
                <source pool="${guest.pool}" volume="guest-${name}" />
                <target dev="vda" bus="virtio"/>
              </disk>
              ${guest.extraDevicesXML or ""}
              <input type="keyboard" bus="usb"/>
              <graphics type="vnc" port="-1" autoport="yes"/>
              <interface type="network">
                <source network="${guest.network}" />
              </interface>
            </devices>
            <features>
              <acpi/>
            </features>
          </domain>
        '';
      in
      guest.preStart or "" + ''
        if ! ${pkgs.libvirt}/bin/virsh vol-key 'guest-${name}' --pool ${guest.pool} &> /dev/null; then
          ${pkgs.libvirt}/bin/virsh vol-create-as --pool ${guest.pool} --name 'guest-${name}' --capacity '${guest.diskSize}'
          volume_path=$(${pkgs.libvirt}/bin/virsh vol-path --pool ${guest.pool} --vol 'guest-${name}')
          ${pkgs.qemu}/bin/qemu-img convert /etc/libvirtd/base-images/nixos.qcow2 $volume_path
        fi
        uuid="$(${pkgs.libvirt}/bin/virsh domuuid '${name}' || true)"
        ${pkgs.libvirt}/bin/virsh define <(sed "s/UUID/$uuid/" '${xml}')
        ${pkgs.libvirt}/bin/virsh start '${name}'
      '';
    preStop = ''
      ${pkgs.libvirt}/bin/virsh shutdown '${name}'
      let "timeout = $(date +%s) + 10"
      while [ "$(${pkgs.libvirt}/bin/virsh list --name | grep --count '^${name}$')" -gt 0 ]; do
        if [ "$(date +%s)" -ge "$timeout" ]; then
          # Meh, we warned it...
          ${pkgs.libvirt}/bin/virsh destroy '${name}'
        else
          # The machine is still running, let's give it some time to shut down
          sleep 0.5
        fi
      done
    '' + lib.optionalString (guest.destroyVolumeOnExit or false) ''
        if ${pkgs.libvirt}/bin/virsh vol-key 'guest-${name}' --pool ${guest.pool} &> /dev/null; then
          ${pkgs.libvirt}/bin/virsh vol-wipe --pool ${guest.pool} --vol 'guest-${name}' || true
          ${pkgs.libvirt}/bin/virsh vol-delete --pool ${guest.pool} --vol 'guest-${name}'
        fi
    '';
  }) guests // (lib.mapAttrs' (name: network: lib.nameValuePair "libvirtd-network-${name}" {
    after = [ "libvirtd.service" ];
    requires = [ "libvirtd.service" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = "yes";
    };
    script = let
      xml = pkgs.writeText "libvirt-network-${name}.xml" ''
        <network>
          <name>${name}</name>
          <uuid>UUID</uuid>
          <forward mode='nat' />
          <bridge name='virbr${network.bridgeNumber}' />
          <domain name='${name}' localOnly='yes'/>
          <ip address='${network.ipRange}.1' netmask='255.255.255.0'>
            <dhcp>
              <range start='${network.ipRange}.2' end='${network.ipRange}.254'/>
            </dhcp>
          </ip>
        </network>
      '';
    in ''
      uuid="$(${pkgs.libvirt}/bin/virsh net-uuid '${name}' || true)"
      ${pkgs.libvirt}/bin/virsh net-define <(sed "s/UUID/$uuid/" '${xml}')
      ${pkgs.libvirt}/bin/virsh net-start '${name}'
    '';
    preStop = ''
      ${pkgs.libvirt}/bin/virsh net-destroy '${name}'
    '';
  }) networks) // (lib.mapAttrs' (name: pool: lib.nameValuePair "libvirtd-pool-${name}" {
    after = [ "libvirtd.service" ];
    requires = [ "libvirtd.service" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = "yes";
    };
    script = let
      xml = pkgs.writeText "libvirt-pool-${name}.xml" ''
        <pool type="${pool.type}">
          <name>${name}</name>
          <uuid>UUID</uuid>
          ${pool.xml or ""}
          ${if pool ? target then ''
            <target>
              <path>${pool.target}</path>
            </target>
          '' else ""}
        </pool>
      '';
    in pool.preStart or "" + ''
      uuid="$(${pkgs.libvirt}/bin/virsh pool-uuid '${name}' || true)"
      ${pkgs.libvirt}/bin/virsh pool-define <(sed "s/UUID/$uuid/" '${xml}')
      ${pkgs.libvirt}/bin/virsh pool-start '${name}' || true
    '';
  }) pools);
}