# Syncthing Module
#
# Declarative Syncthing configuration for NixOS.
# This wraps the built-in syncthing module with sensible defaults.
#
# Usage:
#   services.syncthing-managed.enable = true;
#   services.syncthing-managed.user = "youruser";
#   services.syncthing-managed.devices.laptop.id = "DEVICE-ID-HERE";
#   services.syncthing-managed.folders.documents.path = "~/Documents";

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

with lib;

let
  cfg = config.services.syncthing-managed;
in {
  options.services.syncthing-managed = {
    enable = mkEnableOption "managed Syncthing file synchronization";

    user = mkOption {
      type = types.str;
      description = "User to run Syncthing as.";
      example = "alice";
    };

    group = mkOption {
      type = types.str;
      default = "users";
      description = "Group to run Syncthing as.";
    };

    dataDir = mkOption {
      type = types.str;
      default = "/home/${cfg.user}";
      defaultText = literalExpression ''"/home/''${cfg.user}"'';
      description = "Default directory for Syncthing data.";
    };

    configDir = mkOption {
      type = types.str;
      default = "/home/${cfg.user}/.config/syncthing";
      defaultText = literalExpression ''"/home/''${cfg.user}/.config/syncthing"'';
      description = "Directory for Syncthing configuration.";
    };

    guiAddress = mkOption {
      type = types.str;
      default = "127.0.0.1:8384";
      description = "Address for the Syncthing web GUI.";
    };

    openFirewall = mkOption {
      type = types.bool;
      default = true;
      description = "Whether to open the firewall for Syncthing.";
    };

    devices = mkOption {
      type = types.attrsOf (types.submodule {
        options = {
          id = mkOption {
            type = types.str;
            description = "Device ID (from syncthing CLI or GUI).";
            example = "XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX";
          };

          name = mkOption {
            type = types.nullOr types.str;
            default = null;
            description = "Friendly name for the device.";
          };

          addresses = mkOption {
            type = types.listOf types.str;
            default = [ "dynamic" ];
            description = "Addresses to connect to this device.";
          };

          autoAcceptFolders = mkOption {
            type = types.bool;
            default = false;
            description = "Automatically accept shared folders from this device.";
          };
        };
      });
      default = {};
      description = "Syncthing devices to connect to.";
      example = literalExpression ''
        {
          laptop = {
            id = "XXXXXXX-...";
            name = "My Laptop";
          };
          server = {
            id = "YYYYYYY-...";
            addresses = [ "tcp://server.local:22000" ];
          };
        }
      '';
    };

    folders = mkOption {
      type = types.attrsOf (types.submodule ({ name, ... }: {
        options = {
          path = mkOption {
            type = types.str;
            description = "Local path to sync.";
            example = "~/Documents";
          };

          devices = mkOption {
            type = types.listOf types.str;
            default = attrNames cfg.devices;
            defaultText = literalExpression "attrNames cfg.devices";
            description = "Devices to share this folder with.";
          };

          id = mkOption {
            type = types.str;
            default = name;
            description = "Unique folder ID.";
          };

          type = mkOption {
            type = types.enum [ "sendreceive" "sendonly" "receiveonly" ];
            default = "sendreceive";
            description = ''
              Folder type:
              - sendreceive: Full two-way sync (default)
              - sendonly: Only send changes, ignore remote changes
              - receiveonly: Only receive changes, don't send local changes
            '';
          };

          versioning = mkOption {
            type = types.nullOr (types.submodule {
              options = {
                type = mkOption {
                  type = types.enum [ "simple" "staggered" "trashcan" "external" ];
                  default = "simple";
                  description = "Versioning type.";
                };

                params = mkOption {
                  type = types.attrsOf types.str;
                  default = { keep = "5"; };
                  description = "Versioning parameters.";
                };
              };
            });
            default = null;
            description = "Versioning configuration for this folder.";
            example = literalExpression ''
              {
                type = "staggered";
                params = {
                  cleanInterval = "3600";
                  maxAge = "31536000";
                };
              }
            '';
          };

          ignorePerms = mkOption {
            type = types.bool;
            default = false;
            description = "Ignore permission changes.";
          };

          rescanInterval = mkOption {
            type = types.int;
            default = 3600;
            description = "How often to rescan the folder (seconds). 0 to disable.";
          };

          fsWatcherEnabled = mkOption {
            type = types.bool;
            default = true;
            description = "Use filesystem watcher for real-time sync.";
          };
        };
      }));
      default = {};
      description = "Folders to synchronize.";
      example = literalExpression ''
        {
          documents = {
            path = "~/Documents";
            devices = [ "laptop" "desktop" ];
            versioning = { type = "simple"; params.keep = "5"; };
          };
          music = {
            path = "~/Music";
            type = "receiveonly";  # Don't upload changes
          };
        }
      '';
    };

    extraOptions = mkOption {
      type = types.attrs;
      default = {};
      description = "Extra options to pass to services.syncthing.settings.";
    };
  };

  config = mkIf cfg.enable {
    services.syncthing = {
      enable = true;
      user = cfg.user;
      group = cfg.group;
      dataDir = cfg.dataDir;
      configDir = cfg.configDir;
      guiAddress = cfg.guiAddress;

      overrideDevices = true;  # Declarative device management
      overrideFolders = true;  # Declarative folder management

      settings = {
        devices = mapAttrs (name: device: {
          inherit (device) id addresses autoAcceptFolders;
          name = if device.name != null then device.name else name;
        }) cfg.devices;

        folders = mapAttrs (name: folder: {
          inherit (folder) path id type ignorePerms rescanInterval fsWatcherEnabled;
          devices = folder.devices;
          versioning = if folder.versioning != null then folder.versioning else {};
        }) cfg.folders;

        options = {
          urAccepted = -1;  # Disable usage reporting
          relaysEnabled = true;
          globalAnnounceEnabled = true;
          localAnnounceEnabled = true;
        } // cfg.extraOptions;
      };
    };

    # Open firewall if requested
    networking.firewall = mkIf cfg.openFirewall {
      allowedTCPPorts = [ 22000 ];  # Syncthing protocol
      allowedUDPPorts = [ 22000 21027 ];  # Syncthing + discovery
    };

    # Convenience alias
    environment.systemPackages = [
      (pkgs.writeShellScriptBin "st" ''
        # Syncthing shortcut
        case "$1" in
          status)
            ${pkgs.syncthing}/bin/syncthing cli show system
            ;;
          scan)
            ${pkgs.syncthing}/bin/syncthing cli scan --all
            ;;
          errors)
            ${pkgs.syncthing}/bin/syncthing cli errors
            ;;
          *)
            echo "Usage: st {status|scan|errors}"
            ;;
        esac
      '')
    ];
  };
}