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

with lib;

let
  inherit (customUtils) mapFilterAttrs;

  tsigSecretName = domain: "${domain}_tsig-secret";

  cfg = config.security.acme;
  knotCfg = config.services.knot;
  
  knotDNSCredentials = domain: let
    zone = if cfg.domains.${domain}.zone == null then domain else cfg.domains.${domain}.zone;
  in pkgs.writeText "lego-credentials" ''
    EXEC_PATH=${knotDNSExec zone}/bin/update-dns.sh
    EXEC_PROPAGATION_TIMEOUT=300
    EXEC_POLLING_INTERVAL=5
  '';
  knotDNSExec = zone: pkgs.writeScriptBin "update-dns.sh" ''
    #!${pkgs.zsh}/bin/zsh -xe

    mode=$1
    fqdn=$2
    challenge=$3

    owner=''${fqdn%".${zone}."}

    commited=
    function abort() {
      [[ -n "''${commited}" ]] || ${knotCfg.cliWrappers}/bin/knotc zone-abort "${zone}"
    }

    ${knotCfg.cliWrappers}/bin/knotc zone-begin "${zone}"
    trap abort EXIT

    case "''${mode}" in
      present)
        if ${knotCfg.cliWrappers}/bin/knotc zone-get ${zone} "''${owner}" TXT; then
          ${knotCfg.cliWrappers}/bin/knotc zone-unset ${zone} "''${owner}" TXT '""'
        fi
        ${knotCfg.cliWrappers}/bin/knotc zone-set ${zone} "''${owner}" 30 TXT "''${challenge}"
        ;;
      cleanup)
        ${knotCfg.cliWrappers}/bin/knotc zone-unset ${zone} "''${owner}" TXT "''${challenge}"
        ${knotCfg.cliWrappers}/bin/knotc zone-set ${zone} "''${owner}" 30 TXT '""'
        ;;
      *)
        exit 2
        ;;
    esac

    ${knotCfg.cliWrappers}/bin/knotc zone-commit "${zone}"
    commited=yes
  '';
  
  domainOptions = {
    options = {
      wildcard = mkOption {
        type = types.bool;
        default = false;
      };
      zone = mkOption {
        type = types.nullOr types.str;
        default = null;
      };
      certCfg = mkOption {
        type = types.attrs;
        default = {};
      };
    };
  };
in {
  options = {
    security.acme = {
      domains = mkOption {
        type = types.attrsOf (types.submodule domainOptions);
        default = {};
      };
    };
  };
  
  config = {
    security.acme.domains = genAttrs ["dirty-haskell.org" "141.li" "xmpp.li" "yggdrasil.li" "praseodym.org" "rheperire.org" "kleen.li" "nights.email"] (domain: { wildcard = true; });
    
    fileSystems."/var/lib/acme" =
      { device = "surtr/safe/var-lib-acme";
        fsType = "zfs";
      };

    security.acme = {
      acceptTerms = true;
      preliminarySelfsigned = true; # DNS challenge is slow
      defaults = {
        email = "phikeebaogobaegh@141.li";
        keyType = "rsa4096"; # we don't like NIST curves
        # extraLegoFlags = ["--preferred-chain" "ISRG Root X1"];
      };
      certs =
        let
          domainAttrset = domain: let
            tsigPath = ./tsig_keys + "/${domain}";
            tsigSecret = config.sops.secrets.${tsigSecretName domain};
            isTsig = pathExists tsigPath;
            shared = {
              inherit domain;
              extraDomainNames = optional cfg.domains.${domain}.wildcard "*.${domain}";
              dnsResolver = "127.0.0.1:5353";
            };
            mkKnotc = shared // {
              dnsProvider = "exec";
              credentialsFile = knotDNSCredentials domain;
            };
            mkRFC2136 = let
              tsigInfo = readYaml tsigPath;
            in shared // {
              dnsProvider = "rfc2136";
              credentialsFile = pkgs.writeText "${domain}_credentials.env" ''
                RFC2136_NAMESERVER=127.0.0.1:53
                RFC2136_TSIG_ALGORITHM=hmac-sha256.
                RFC2136_TSIG_KEY=${domain}_acme
                RFC2136_TSIG_SECRET_FILE=${tsigSecret.path}
                RFC2136_PROPAGATION_TIMEOUT=300
                RFC2136_POLLING_INTERVAL=5
                RFC2136_TTL=300
              '';
            };
          in (if isTsig then mkRFC2136 else mkKnotc) // cfg.domains.${domain}.certCfg;
        in genAttrs (attrNames cfg.domains) domainAttrset;
    };

    sops.secrets = let
      toTSIGSecret = n: v:
        if v == "regular" || v == "symlink"
        then nameValuePair (tsigSecretName n) {
          format = "binary";
          owner = if config.security.acme.useRoot then "root" else "acme";
          group = "acme";
          sopsFile = ./tsig_keys + "/${n}";
        } else null;
    in mapFilterAttrs (_: v: v != null) toTSIGSecret (builtins.readDir ./tsig_keys);

    systemd.services =
      let
        serviceAttrset = domain: {
          after = [ "knot.service" ];
          bindsTo = [ "knot.service" ];
          serviceConfig = {
            ReadWritePaths = ["/run/knot/knot.sock"];
            SupplementaryGroups = ["knot"];
            RestrictAddressFamilies = ["AF_UNIX"];
          };
        };
      in mapAttrs' (domain: nameValuePair "acme-${domain}") (genAttrs (attrNames config.security.acme.certs) serviceAttrset);
  };
}