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

with lib;
let
  relative-hostname = "forum.test";

  strip-hash = filename: head (builtins.match "^[a-zA-Z0-9]+-(.+)$" filename);

  clean-utf8-file = filename:
    pkgs.stdenv.mkDerivation {
      name = "${strip-hash (baseNameOf filename)}.utf8";

      phases = [ "installPhase" ];

      installPhase = "iconv -c -f utf-8 -t utf-8 -o $out ${filename}";
    };

in {
  options.fudo.services.selby-forum = with types; {
    enable = mkEnableOption "Enable Selby Forum on this host.";

    state-directory = mkOption {
      type = str;
      description = "Directory at which to store Selby Forum state.";
    };

    legacy-forum-data = mkOption {
      type = path;
      description = "Path to legacy Vanilla forum data.";
    };

    external-interface = mkOption {
      type = str;
      description = "Public-facing network interface on this host.";
    };

    mail = {
      host = mkOption {
        type = str;
        description = "Mail server hostname.";
      };
    };
  };

  config = (let
    hostname = config.instance.hostname;

    cfg = config.fudo.services.selby-forum;

    host-fqdn = let host-domain = config.fudo.hosts.${hostname}.domain;
    in "${hostname}.${host-domain}";

    host-secrets = config.fudo.secrets.host-secrets.${hostname};

    parent-ip = "192.168.92.1";
    child-ip = "192.168.92.2";

    mkPasswd = name:
      pkgs.lib.passwd.stablerandom-passwd-file "selby-forum-${name}"
      "selby-forum-${name}-${config.instance.build-seed}";

    mail-user = "selby-forum";
    mail-password = mkPasswd "mail-password";

    database-name = "forum_selby_ca";
    database-user = "forum_selby_ca";

    runtime-path = "/run/selby/forum";

    domain-name = "selby.ca";
    zone-name = config.fudo.domains.${domain-name}.zone;

    forum-hostname = "${relative-hostname}.${domain-name}";

  in {
    networking = mkIf cfg.enable {
      nat = {
        enable = true;
        internalInterfaces = [ "ve-selby-forum" ];
        externalInterface = cfg.external-interface;
      };
    };

    services.nginx = mkIf cfg.enable {
      enable = true;
      recommendedOptimisation = true;
      recommendedProxySettings = true;

      virtualHosts.${forum-hostname} = {
        enableACME = true;
        forceSSL = true;
        locations."/".proxyPass = "http://${child-ip}:80";
      };
    };

    fudo = {
      # Email user
      system-users.${mail-user} = {
        description = "Selby Forum";
        ldap-hashed-password =
          pkgs.lib.passwd.hash-ldap-passwd "selby-forum-mail-passwd"
          mail-password;
      };

      zones.${zone-name}.aliases = { ${relative-hostname} = "${host-fqdn}."; };

      secrets.host-secrets.${hostname} = mkIf cfg.enable
        (let db-passwd = mkPasswd "database-password";
        in {
          selby-forum-database-password = {
            source-file = db-passwd;
            target-file = "${runtime-path}/db.passwd";
          };
          postgres-selby-forum-password = {
            source-file = db-passwd;
            target-file = "/run/postgres-users/selby-forum.passwd";
            user = config.services.postgresql.superUser;
          };
          selby-forum-admin-passwd = {
            source-file = mkPasswd "admin-password";
            target-file = "${runtime-path}/admin.passwd";
          };
          selby-forum-mail-passwd = {
            source-file = mail-password;
            target-file = "${runtime-path}/mail.passwd";
          };
          legacy-selby-forum-data = {
            source-file = "${clean-utf8-file cfg.legacy-forum-data}";
            target-file = "${runtime-path}/selby-forum-data.sql";
          };
        });

      postgresql = mkIf cfg.enable {
        local-networks = [ "192.168.92.0/30" ];
        databases.${database-name}.users = config.instance.local-admins;
        users.${database-user} = {
          password-file =
            host-secrets.postgres-selby-forum-password.target-file;
          databases.${database-name} = {
            access = "CONNECT,CREATE";
            entity-access = {
              "ALL TABLES IN SCHEMA public" = "SELECT,INSERT,UPDATE,DELETE";
              "ALL SEQUENCES IN SCHEMA public" = "SELECT,UPDATE";
            };
          };
        };
      };
    };

    systemd = mkIf cfg.enable {
      tmpfiles.rules = [ "d ${cfg.state-directory} 750 - - - -" ];

      services.discourse-prepare-selby-forum = {
        description =
          "Perform superuser tasks for Discourse, which doesn't have SU perms.";
        wantedBy = [ "container@selby-forum.service" ];
        before = [ "container@selby-forum.service" ];
        requires = [ config.fudo.postgresql.systemd-target ];
        after = [ config.fudo.postgresql.systemd-target ];
        path = with pkgs; [ postgresql ];
        serviceConfig = {
          User = config.services.postgresql.superUser;
          ExecStart =
            pkgs.writeShellScript "discourse-prepare-selby-forum.sh" ''
              psql -d ${database-name} -c "CREATE EXTENSION IF NOT EXISTS hstore;"
              psql -d ${database-name} -c "CREATE EXTENSION IF NOT EXISTS pg_trgm;"
            '';
        };
      };
    };

    containers.selby-forum = mkIf cfg.enable {
      ephemeral = true;
      privateNetwork = true;
      hostAddress = parent-ip;
      localAddress = child-ip;
      autoStart = true;

      bindMounts = {
        ${runtime-path} = {
          hostPath = runtime-path;
          isReadOnly = true;
        };
        "/var/lib/discourse" = {
          hostPath = cfg.state-directory;
          isReadOnly = false;
        };
      };

      config = { config, lib, ... }:
        let
          discourse-user = config.systemd.services.discourse.serviceConfig.User;
        in {
          networking = {
            defaultGateway = parent-ip;
            firewall.enable = false;
          };

          services.discourse = {
            enable = true;
            hostname = forum-hostname;
            enableACME = false;
            admin = {
              username = "admin";
              fullName = "Admin";
              email = "admin@selby.ca";
              passwordFile = "/etc/selby-forum/admin.passwd";
            };
            database = {
              name = database-name;
              host = parent-ip;
              username = database-user;
              passwordFile = "/etc/selby-forum/db.passwd";
            };
            mail.outgoing = {
              username = mail-user;
              passwordFile = "/etc/selby-forum/mail.passwd";
              domain = domain-name;
              forceTLS = true;
              serverAddress = cfg.mail.host;
            };
          };

          environment.etc = {
            "selby-forum/admin.passwd" = {
              source = "/run/selby/forum/admin.passwd";
              user = discourse-user;
              mode = "0400";
            };
            "selby-forum/db.passwd" = {
              source = "/run/selby/forum/db.passwd";
              user = discourse-user;
              mode = "0400";
            };
            "selby-forum/selby-forum-data.sql" = {
              source = "/run/selby/forum/selby-forum-data.sql";
              user = discourse-user;
              mode = "0400";
            };
            "selby-forum/mail.passwd" = {
              source = "/run/selby/forum/mail.passwd";
              user = discourse-user;
              mode = "0400";
            };
          };

          systemd = {
            tmpfiles.rules =
              [ "d /var/lib/discourse 700 ${discourse-user} - - -" ];

            services = {
              discourse = { after = [ "multi-user.target" ]; };

              discourse-import-selby-forum = let
                env-without-path = filterAttrs (attr: _: attr != "PATH")
                  config.systemd.services.discourse.environment;
              in {
                description = "One-off job to import Vanilla Selby Forum data.";
                path = config.systemd.services.discourse.path;
                environment = env-without-path;
                serviceConfig = {
                  User = discourse-user;
                  type = "oneshot";
                  WorkingDirectory =
                    config.systemd.services.discourse.serviceConfig.WorkingDirectory;
                  ExecStart = pkgs.writeShellScript
                    "import-vanilla-selby-forum-data.sh" ''
                      ruby script/import_scripts/vanilla.rb /etc/selby-forum/selby-forum-data.sql
                    '';
                };
              };
            };
          };
        };
    };
  });
}