{ config, pkgs, lib, flakeRoot, ... }:
let
  repoWallpaperDir = flakeRoot + "/assets/conf/desktop/wallpaper";

  userRelRoot = "nixos_conf/wallpaperstuff";
  userAbsRoot = "${config.home.homeDirectory}/${userRelRoot}";

  picturesDir = "${userAbsRoot}/pictures";
  currentDir  = "${userAbsRoot}/current";

  scriptRel = "hypr/scripts/wpaperd-workspace-1to9.sh";
  wpaperdConfRel = "wpaperd/config.toml";
  wpaperdConfAbs = "${config.xdg.configHome}/${wpaperdConfRel}";
in
{
  home.packages = [
    pkgs.wpaperd
    pkgs.socat
    pkgs.jq
    pkgs.coreutils
  ];

  # Copy wallpapers from repo → ~/nixos_conf/wallpaperstuff
  home.file."${userRelRoot}" = {
    source = repoWallpaperDir;
    recursive = true;
  };

  # Create a correct wpaperd config.
  # - [default] sets stretch globally
  # - [any] acts as fallback for outputs not explicitly listed (wpaperd-output(5))
  # - Per-output sections point at CURRENT/<MON>.jpg (symlinks the script updates)
  #
  # NOTE: This is safe even if you add/remove monitors: [any] keeps things working.
  xdg.configFile."${wpaperdConfRel}".text = ''
    [default]
    mode = "stretch"

    [any]
    path = "${picturesDir}/wallpaper1.jpg"

    [eDP-1]
    path = "${currentDir}/eDP-1.jpg"

    [DP-1]
    path = "${currentDir}/DP-1.jpg"
  '';

  # Listener: on focused monitor change, update CURRENT/<MON>.jpg -> pictures/wallpaperN.jpg
  xdg.configFile."${scriptRel}" = {
    executable = true;
    text = ''
      #!/usr/bin/env bash
      set -euo pipefail

      log() { echo "[wpaperd-ws] $*" >&2; }

      PICTURES="${picturesDir}"
      CURRENT="${currentDir}"
      CONF="${wpaperdConfAbs}"

      : "''${XDG_RUNTIME_DIR:?XDG_RUNTIME_DIR not set}"
      : "''${HYPRLAND_INSTANCE_SIGNATURE:?HYPRLAND_INSTANCE_SIGNATURE not set}"
      SOCK="''${XDG_RUNTIME_DIR}/hypr/''${HYPRLAND_INSTANCE_SIGNATURE}/.socket2.sock"

      mkdir -p "$CURRENT" "$(dirname "$CONF")"

      # Wait for Hyprland socket so the service doesn't exit too early
      for i in $(seq 1 120); do
        [[ -S "$SOCK" ]] && break
        sleep 0.1
      done
      [[ -S "$SOCK" ]] || { log "Hyprland socket not found: $SOCK"; exit 1; }

      ws_num() {
        local w="''${1%%:*}"
        [[ "$w" =~ ^[0-9]+$ ]] || return 1
        printf '%s\n' "$w"
      }

      img_for_ws() {
        local n="$1"
        case "$n" in
          1|2|3|4|5|6|7|8|9) printf '%s/wallpaper%s.jpg\n' "$PICTURES" "$n" ;;
          *) return 1 ;;
        esac
      }

      ensure_link_for() {
        local mon="$1"
        local ws="$2"

        local n img
        n="$(ws_num "$ws")" || return 0
        img="$(img_for_ws "$n")" || return 0

        if [[ ! -f "$img" ]]; then
          log "Missing image for ws=$n: $img"
          return 0
        fi

        ln -sf "$img" "$CURRENT/$mon.jpg"
        log "Link: $CURRENT/$mon.jpg -> $img"
      }

      reload() {
        # wpaperctl reload-wallpaper exists on v1.2.1
        ${pkgs.wpaperd}/bin/wpaperctl reload-wallpaper >/dev/null 2>&1 || true
      }

      apply_initial() {
        ${pkgs.hyprland}/bin/hyprctl -j monitors \
          | ${pkgs.jq}/bin/jq -r '.[] | "\(.name)\t\(.activeWorkspace.name)"' \
          | while IFS=$'\t' read -r mon ws; do
              [[ -n "$mon" && -n "$ws" ]] || continue
              ensure_link_for "$mon" "$ws" || true
            done
        reload
      }

      handle_line() {
        case "$1" in
          focusedmon\>\>*)
            # focusedmon>>MONNAME,WORKSPACENAME
            local payload="''${1#focusedmon>>}"
            local mon="''${payload%%,*}"
            local ws="''${payload#*,}"
            [[ -n "$mon" && -n "$ws" ]] || return 0
            ensure_link_for "$mon" "$ws" || true
            reload
            ;;
        esac
      }

      apply_initial
      log "Listening on $SOCK"
      exec ${pkgs.socat}/bin/socat -U - "UNIX-CONNECT:$SOCK" \
        | while IFS= read -r line; do
            handle_line "$line" || true
          done
    '';
  };

  # Start wpaperd (reads XDG_CONFIG_HOME/wpaperd/config.toml by default)
  systemd.user.services.wpaperd = {
    Unit = {
      Description = "wpaperd wallpaper daemon";
      After = [ "graphical-session.target" ];
      PartOf = [ "graphical-session.target" ];
    };
    Service = {
      ExecStart = "${pkgs.wpaperd}/bin/wpaperd";
      Restart = "on-failure";
      RestartSec = 1;
    };
    Install.WantedBy = [ "graphical-session.target" ];
  };

  # Listener service
  systemd.user.services.wpaperd-workspace-wallpapers = {
    Unit = {
      Description = "Set wallpaper per monitor based on workspace number (1..9)";
      After = [ "graphical-session.target" "wpaperd.service" ];
      PartOf = [ "graphical-session.target" ];
    };
    Service = {
      ExecStart = "${pkgs.bash}/bin/bash ${config.xdg.configHome}/${scriptRel}";
      Restart = "on-failure";
      RestartSec = 1;
    };
    Install.WantedBy = [ "graphical-session.target" ];
  };
}