{ config, lib, pkgs, utils, ... }:
with lib;
let
  cfg = config.services.kubo;

  settingsFormat = pkgs.formats.json {};

  kuboFlags = utils.escapeSystemdExecArgs (
    optional cfg.autoMount "--mount" ++
    optional cfg.enableGC "--enable-gc" ++
    optional (cfg.serviceFdlimit != null) "--manage-fdlimit=false" ++
    optional (cfg.defaultMode == "offline") "--offline" ++
    optional (cfg.defaultMode == "norouting") "--routing=none" ++
    cfg.extraFlags
  );

  profile =
    if cfg.localDiscovery
    then "local-discovery"
    else "server";

  splitMulitaddr = addrRaw: lib.tail (lib.splitString "/" addrRaw);

  multiaddrToListenStream = addrRaw:
    let
      addr = splitMulitaddr addrRaw;
      s = builtins.elemAt addr;
    in
    if s 0 == "ip4" && s 2 == "tcp"
    then "${s 1}:${s 3}"
    else if s 0 == "ip6" && s 2 == "tcp"
    then "[${s 1}]:${s 3}"
    else if s 0 == "unix"
    then "/${lib.concatStringsSep "/" (lib.tail addr)}"
    else null; # not valid for listen stream, skip

  multiaddrToListenDatagram = addrRaw:
    let
      addr = splitMulitaddr addrRaw;
      s = builtins.elemAt addr;
    in
    if s 0 == "ip4" && s 2 == "udp"
    then "${s 1}:${s 3}"
    else if s 0 == "ip6" && s 2 == "udp"
    then "[${s 1}]:${s 3}"
    else null; # not valid for listen datagram, skip

  multiaddrsFunc = f: addrsRaw: if builtins.isString addrsRaw then let out = f addrsRaw; in lib.optional (out != null) out else lib.filter (x: x != null) (map f addrsRaw);

  multiaddrsToListenStream = multiaddrsFunc multiaddrToListenStream;
  multiaddrsToListenDatagram = multiaddrsFunc multiaddrToListenDatagram;

in
{

  ###### interface

  options = {

    services.kubo = {

      enable = mkEnableOption (lib.mdDoc "Interplanetary File System (WARNING: may cause severe network degredation)");

      package = mkOption {
        type = types.package;
        default = pkgs.kubo;
        defaultText = literalExpression "pkgs.kubo";
        description = lib.mdDoc "Which Kubo package to use.";
      };

      user = mkOption {
        type = types.str;
        default = "ipfs";
        description = lib.mdDoc "User under which the Kubo daemon runs";
      };

      group = mkOption {
        type = types.str;
        default = "ipfs";
        description = lib.mdDoc "Group under which the Kubo daemon runs";
      };

      dataDir = mkOption {
        type = types.str;
        default =
          if versionAtLeast config.system.stateVersion "17.09"
          then "/var/lib/ipfs"
          else "/var/lib/ipfs/.ipfs";
        defaultText = literalExpression ''
          if versionAtLeast config.system.stateVersion "17.09"
          then "/var/lib/ipfs"
          else "/var/lib/ipfs/.ipfs"
        '';
        description = lib.mdDoc "The data dir for Kubo";
      };

      defaultMode = mkOption {
        type = types.enum [ "online" "offline" "norouting" ];
        default = "online";
        description = lib.mdDoc "systemd service that is enabled by default";
      };

      autoMount = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc "Whether Kubo should try to mount /ipfs and /ipns at startup.";
      };

      autoMigrate = mkOption {
        type = types.bool;
        default = true;
        description = lib.mdDoc "Whether Kubo should try to run the fs-repo-migration at startup.";
      };

      ipfsMountDir = mkOption {
        type = types.str;
        default = "/ipfs";
        description = lib.mdDoc "Where to mount the IPFS namespace to";
      };

      ipnsMountDir = mkOption {
        type = types.str;
        default = "/ipns";
        description = lib.mdDoc "Where to mount the IPNS namespace to";
      };

      enableGC = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc "Whether to enable automatic garbage collection";
      };

      emptyRepo = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc "If set to true, the repo won't be initialized with help files";
      };

      settings = mkOption {
        type = lib.types.submodule {
          freeformType = settingsFormat.type;

          options = {
            Addresses.API = mkOption {
              type = types.oneOf [ types.str (types.listOf types.str) ];
              default = "/ip4/127.0.0.1/tcp/5001";
              description = lib.mdDoc "Where Kubo exposes its API to";
            };

            Addresses.Gateway = mkOption {
              type = types.oneOf [ types.str (types.listOf types.str) ];
              default = "/ip4/127.0.0.1/tcp/8080";
              description = lib.mdDoc "Where the IPFS Gateway can be reached";
            };

            Addresses.Swarm = mkOption {
              type = types.oneOf [ types.str (types.listOf types.str) ];
              default = [
                "/ip4/0.0.0.0/tcp/4001"
                "/ip6/::/tcp/4001"
                "/ip4/0.0.0.0/udp/4001/quic"
                "/ip6/::/udp/4001/quic"
              ];
              description = lib.mdDoc "Where Kubo listens for incoming p2p connections";
            };
          };
        };
        description = lib.mdDoc ''
          Attrset of daemon configuration to set using {command}`ipfs config`, every time the daemon starts.
          See [https://github.com/ipfs/kubo/blob/master/docs/config.md](https://github.com/ipfs/kubo/blob/master/docs/config.md) for reference.
          Keep in mind that this configuration is stateful; i.e., unsetting anything in here does not reset the value to the default!
        '';
        default = { };
        example = {
          Datastore.StorageMax = "100GB";
          Discovery.MDNS.Enabled = false;
          Bootstrap = [
            "/ip4/128.199.219.111/tcp/4001/ipfs/QmSoLSafTMBsPKadTEgaXctDQVcqN88CNLHXMkTNwMKPnu"
            "/ip4/162.243.248.213/tcp/4001/ipfs/QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm"
          ];
          Swarm.AddrFilters = null;
        };

      };

      extraFlags = mkOption {
        type = types.listOf types.str;
        description = lib.mdDoc "Extra flags passed to the Kubo daemon";
        default = [ ];
      };

      localDiscovery = mkOption {
        type = types.bool;
        description = lib.mdDoc ''Whether to enable local discovery for the Kubo daemon.
          This will allow Kubo to scan ports on your local network. Some hosting services will ban you if you do this.
        '';
        default = false;
      };

      serviceFdlimit = mkOption {
        type = types.nullOr types.int;
        default = null;
        description = lib.mdDoc "The fdlimit for the Kubo systemd unit or `null` to have the daemon attempt to manage it";
        example = 64 * 1024;
      };

      startWhenNeeded = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc "Whether to use socket activation to start Kubo when needed.";
      };

    };
  };

  ###### implementation

  config = mkIf cfg.enable {
    environment.systemPackages = [ cfg.package ];
    environment.variables.IPFS_PATH = cfg.dataDir;

    # https://github.com/lucas-clemente/quic-go/wiki/UDP-Receive-Buffer-Size
    boot.kernel.sysctl."net.core.rmem_max" = mkDefault 2500000;

    programs.fuse = mkIf cfg.autoMount {
      userAllowOther = true;
    };

    users.users = mkIf (cfg.user == "ipfs") {
      ipfs = {
        group = cfg.group;
        home = cfg.dataDir;
        createHome = false;
        uid = config.ids.uids.ipfs;
        description = "IPFS daemon user";
        packages = [
          pkgs.kubo-migrator
        ];
      };
    };

    users.groups = mkIf (cfg.group == "ipfs") {
      ipfs.gid = config.ids.gids.ipfs;
    };

    systemd.tmpfiles.rules = [
      "d '${cfg.dataDir}' - ${cfg.user} ${cfg.group} - -"
    ] ++ optionals cfg.autoMount [
      "d '${cfg.ipfsMountDir}' - ${cfg.user} ${cfg.group} - -"
      "d '${cfg.ipnsMountDir}' - ${cfg.user} ${cfg.group} - -"
    ];

    # The hardened systemd unit breaks the fuse-mount function according to documentation in the unit file itself
    systemd.packages = if cfg.autoMount
      then [ cfg.package.systemd_unit ]
      else [ cfg.package.systemd_unit_hardened ];

    services.kubo.settings = mkIf cfg.autoMount {
      Mounts.FuseAllowOther = lib.mkDefault true;
      Mounts.IPFS = lib.mkDefault cfg.ipfsMountDir;
      Mounts.IPNS = lib.mkDefault cfg.ipnsMountDir;
    };

    systemd.services.ipfs = {
      path = [ "/run/wrappers" cfg.package ];
      environment.IPFS_PATH = cfg.dataDir;

      preStart = ''
        if [[ ! -f "$IPFS_PATH/config" ]]; then
          ipfs init ${optionalString cfg.emptyRepo "-e"} --profile=${profile}
        else
          # After an unclean shutdown this file may exist which will cause the config command to attempt to talk to the daemon. This will hang forever if systemd is holding our sockets open.
          rm -vf "$IPFS_PATH/api"
      '' + optionalString cfg.autoMigrate ''
        ${pkgs.kubo-migrator}/bin/fs-repo-migrations -to '${cfg.package.repoVersion}' -y
      '' + ''
          ipfs --offline config profile apply ${profile} >/dev/null
        fi
      '' + ''
        ipfs --offline config show \
          | ${pkgs.jq}/bin/jq '. * $settings' --argjson settings ${
              escapeShellArg (builtins.toJSON cfg.settings)
            } \
          | ipfs --offline config replace -
      '';
      serviceConfig = {
        ExecStart = [ "" "${cfg.package}/bin/ipfs daemon ${kuboFlags}" ];
        User = cfg.user;
        Group = cfg.group;
        StateDirectory = "";
        ReadWritePaths = optionals (!cfg.autoMount) [ "" cfg.dataDir ];
      } // optionalAttrs (cfg.serviceFdlimit != null) { LimitNOFILE = cfg.serviceFdlimit; };
    } // optionalAttrs (!cfg.startWhenNeeded) {
      wantedBy = [ "default.target" ];
    };

    systemd.sockets.ipfs-gateway = {
      wantedBy = [ "sockets.target" ];
      socketConfig = {
        ListenStream =
          let
            fromCfg = multiaddrsToListenStream cfg.settings.Addresses.Gateway;
          in
          [ "" ] ++ fromCfg;
        ListenDatagram =
          let
            fromCfg = multiaddrsToListenDatagram cfg.settings.Addresses.Gateway;
          in
          [ "" ] ++ fromCfg;
      };
    };

    systemd.sockets.ipfs-api = {
      wantedBy = [ "sockets.target" ];
      # We also include "%t/ipfs.sock" because there is no way to put the "%t"
      # in the multiaddr.
      socketConfig.ListenStream =
        let
          fromCfg = multiaddrsToListenStream cfg.settings.Addresses.API;
        in
        [ "" "%t/ipfs.sock" ] ++ fromCfg;
    };
  };

  meta = {
    maintainers = with lib.maintainers; [ Luflosi ];
  };

  imports = [
    (mkRenamedOptionModule [ "services" "ipfs" "enable" ] [ "services" "kubo" "enable" ])
    (mkRenamedOptionModule [ "services" "ipfs" "package" ] [ "services" "kubo" "package" ])
    (mkRenamedOptionModule [ "services" "ipfs" "user" ] [ "services" "kubo" "user" ])
    (mkRenamedOptionModule [ "services" "ipfs" "group" ] [ "services" "kubo" "group" ])
    (mkRenamedOptionModule [ "services" "ipfs" "dataDir" ] [ "services" "kubo" "dataDir" ])
    (mkRenamedOptionModule [ "services" "ipfs" "defaultMode" ] [ "services" "kubo" "defaultMode" ])
    (mkRenamedOptionModule [ "services" "ipfs" "autoMount" ] [ "services" "kubo" "autoMount" ])
    (mkRenamedOptionModule [ "services" "ipfs" "autoMigrate" ] [ "services" "kubo" "autoMigrate" ])
    (mkRenamedOptionModule [ "services" "ipfs" "ipfsMountDir" ] [ "services" "kubo" "ipfsMountDir" ])
    (mkRenamedOptionModule [ "services" "ipfs" "ipnsMountDir" ] [ "services" "kubo" "ipnsMountDir" ])
    (mkRenamedOptionModule [ "services" "ipfs" "gatewayAddress" ] [ "services" "kubo" "settings" "Addresses" "Gateway" ])
    (mkRenamedOptionModule [ "services" "ipfs" "apiAddress" ] [ "services" "kubo" "settings" "Addresses" "API" ])
    (mkRenamedOptionModule [ "services" "ipfs" "swarmAddress" ] [ "services" "kubo" "settings" "Addresses" "Swarm" ])
    (mkRenamedOptionModule [ "services" "ipfs" "enableGC" ] [ "services" "kubo" "enableGC" ])
    (mkRenamedOptionModule [ "services" "ipfs" "emptyRepo" ] [ "services" "kubo" "emptyRepo" ])
    (mkRenamedOptionModule [ "services" "ipfs" "extraConfig" ] [ "services" "kubo" "settings" ])
    (mkRenamedOptionModule [ "services" "ipfs" "extraFlags" ] [ "services" "kubo" "extraFlags" ])
    (mkRenamedOptionModule [ "services" "ipfs" "localDiscovery" ] [ "services" "kubo" "localDiscovery" ])
    (mkRenamedOptionModule [ "services" "ipfs" "serviceFdlimit" ] [ "services" "kubo" "serviceFdlimit" ])
    (mkRenamedOptionModule [ "services" "ipfs" "startWhenNeeded" ] [ "services" "kubo" "startWhenNeeded" ])
    (mkRenamedOptionModule [ "services" "kubo" "extraConfig" ] [ "services" "kubo" "settings" ])
    (mkRenamedOptionModule [ "services" "kubo" "gatewayAddress" ] [ "services" "kubo" "settings" "Addresses" "Gateway" ])
    (mkRenamedOptionModule [ "services" "kubo" "apiAddress" ] [ "services" "kubo" "settings" "Addresses" "API" ])
    (mkRenamedOptionModule [ "services" "kubo" "swarmAddress" ] [ "services" "kubo" "settings" "Addresses" "Swarm" ])
  ];
}