{ config, pkgs, lib, kubenix, ... }:

with lib;

let
  cfg = config.testing;
  parentConfig = config;

  nixosTesting = import <nixpkgs/nixos/lib/testing.nix> {
    inherit pkgs;
    system = "x86_64-linux";
  };

  kubernetesBaseConfig = { config, pkgs, lib, nodes, ... }: let
    master = findFirst
      (node: any (role: role == "master") node.config.services.kubernetes.roles)
      (throw "no master node")
      (attrValues nodes);
    extraHosts = ''
      ${master.config.networking.primaryIPAddress}  etcd.${config.networking.domain}
      ${master.config.networking.primaryIPAddress}  api.${config.networking.domain}
      ${concatMapStringsSep "\n"
        (node: let n = node.config.networking; in "${n.primaryIPAddress}  ${n.hostName}.${n.domain}")
        (attrValues nodes)}
    '';
  in {
    imports = [ <nixpkgs/nixos/modules/profiles/minimal.nix> ];

    config = mkMerge [{
      boot.postBootCommands = "rm -fr /var/lib/kubernetes/secrets /tmp/shared/*";
      virtualisation.memorySize = mkDefault 2048;
      virtualisation.cores = mkDefault 16;
      virtualisation.diskSize = mkDefault 4096;
      networking = {
        inherit extraHosts;
        domain = "my.xzy";
        nameservers = ["10.0.0.254"];
        firewall = {
          allowedTCPPorts = [
            10250 # kubelet
          ];
          trustedInterfaces = ["docker0" "cni0"];

          extraCommands = concatMapStrings  (node: ''
            iptables -A INPUT -s ${node.config.networking.primaryIPAddress} -j ACCEPT
          '') (attrValues nodes);
        };
      };
      environment.systemPackages = [ pkgs.kubectl ];
      environment.variables.KUBECONFIG = "/etc/kubernetes/cluster-admin.kubeconfig";
      services.flannel.iface = "eth1";
      services.kubernetes = {
        easyCerts = true;
        apiserver = {
          securePort = 443;
          advertiseAddress = master.config.networking.primaryIPAddress;
        };
        masterAddress = "${master.config.networking.hostName}.${master.config.networking.domain}";
      };

      systemd.extraConfig = "DefaultLimitNOFILE=1048576";
    }
    (mkIf (any (role: role == "master") config.services.kubernetes.roles) {
      networking.firewall.allowedTCPPorts = [
        443 # kubernetes apiserver
      ];
    })];
  };

  mkKubernetesSingleNodeTest = { name, testScript, extraConfiguration ? {} }:
    nixosTesting.makeTest {
      inherit name;

      nodes.kube = { config, pkgs, nodes, ... }: {
        imports = [ kubernetesBaseConfig ];
        services.kubernetes = {
          roles = ["master" "node"];
          flannel.enable = false;
          kubelet = {
            networkPlugin = "cni";
            cni.config = [{
              name = "mynet";
              type = "bridge";
              bridge = "cni0";
              addIf = true;
              ipMasq = true;
              isGateway = true;
              ipam = {
                type = "host-local";
                subnet = "10.1.0.0/16";
                gateway = "10.1.0.1";
                routes = [{
                  dst = "0.0.0.0/0";
                }];
              };
            }];
          };
        };
        networking.primaryIPAddress = mkForce "192.168.1.1";
      };

      testScript = ''
        startAll;

        $kube->waitUntilSucceeds("kubectl get node kube.my.xzy | grep -w Ready");

        ${testScript}
      '';
    };

  testOptions = {config, ...}: let
    modules = [config.module ./test.nix {
      config._module.args.test = config;
    }] ++ cfg.defaults;

    test = (kubenix.evalModules {
      check = false;
      inherit modules;
    }).config.test;

    evaled =
      if test.enable
      then builtins.trace "testing ${test.name}" (kubenix.evalModules {
        inherit modules;
      })
      else {success = false;};
  in {
    options = {
      name = mkOption {
        description = "test name";
        type = types.str;
        internal = true;
      };

      description = mkOption {
        description = "test description";
        type = types.str;
        internal = true;
      };

      enable = mkOption {
        description = "Whether to enable test";
        type = types.bool;
        internal = true;
      };

      module = mkOption {
        description = "Module defining submodule";
        type = types.unspecified;
      };

      evaled = mkOption {
        description = "Wheter test was evaled";
        type = types.bool;
        default =
          if cfg.throwError
          then if evaled.config.test.assertions != [] then true else true
          else (builtins.tryEval evaled.config.test.assertions).success;
        internal = true;
      };

      success = mkOption {
        description = "Whether test was success";
        type = types.bool;
        internal = true;
        default = false;
      };

      assertions = mkOption {
        description = "Test result";
        type = types.unspecified;
        internal = true;
        default = [];
      };

      test = mkOption {
        description = "Test derivation to run";
        type = types.nullOr types.package;
        default = null;
      };

      generated = mkOption {
        description = "Generated resources";
        type = types.nullOr types.package;
        default = null;
      };
    };

    config = mkMerge [{
      inherit (test) name description enable;
    } (mkIf config.evaled {
      inherit (evaled.config.test) assertions;
      success = all (el: el.assertion) config.assertions;
      test =
        if cfg.e2e && evaled.config.test.testScript != null
        then mkKubernetesSingleNodeTest {
          inherit (evaled.config.test) testScript;
          name = config.name;
        } else null;
      generated = mkIf (hasAttr "kubernetes" evaled.config)
        (pkgs.writeText "${config.name}-gen.json" (builtins.toJSON evaled.config.kubernetes.generated));
    })];
  };
in {
  options = {
    testing.throwError = mkOption {
      description = "Whether to throw error";
      type = types.bool;
      default = true;
    };

    testing.e2e = mkOption {
      description = "Whether to enable e2e tests";
      type = types.bool;
      default = true;
    };

    testing.defaults = mkOption {
      description = "Testing defaults";
      type = types.coercedTo types.unspecified (value: [value]) (types.listOf types.unspecified);
      example = literalExample ''{config, ...}: {
        kubernetes.version = config.kubernetes.version;
      }'';
      default = [];
    };

    testing.tests = mkOption {
      description = "Attribute set of test cases";
      default = [];
      type = types.listOf (types.coercedTo types.path (module: {inherit module;}) (types.submodule testOptions));
      apply = tests: filter (test: test.enable) tests;
    };

    testing.testsByName = mkOption {
      description = "Tests by name";
      type = types.attrsOf types.attrs;
      default = listToAttrs (map (test: nameValuePair test.name test) cfg.tests);
    };

    testing.success = mkOption {
      description = "Whether testing was a success";
      type = types.bool;
      default = all (test: test.success) cfg.tests;
    };

    testing.result = mkOption {
      description = "Testing result";
      type = types.package;
      default = pkgs.writeText "testing-report.json" (builtins.toJSON {
        success = cfg.success;
        tests = map (test: {
          inherit (test) name description evaled success test;
          assertions = moduleToAttrs test.assertions;
        }) (filter (test: test.enable) cfg.tests);
      });
    };
  };
}