{ config, pkgs, ... }:
let
  wallpaperScript = pkgs.writeShellScript "update-wallpaper.sh" ''
    set -euo pipefail

    CREDENTIAL_FILE="$CREDENTIALS_DIRECTORY/login_token"
    UNSPLASH_ACCESS_KEY=$("${pkgs.coreutils}/bin/cat" "$CREDENTIAL_FILE")
    if [ -z "$UNSPLASH_ACCESS_KEY" ]; then
      echo "Error: UNSPLASH_ACCESS_KEY is empty"
      exit 1
    fi

    WALLPAPER_DIR="$HOME/.local/share/wallpapers"
    "${pkgs.coreutils}/bin/mkdir" -p "$WALLPAPER_DIR"

    TMPFILE="$("${pkgs.coreutils}/bin/mktemp")"

    echo "Fetching random Unsplash image URL..."
    URL=$("${pkgs.curl}/bin/curl" -s \
      "https://api.unsplash.com/photos/random?query=nature,landscape&orientation=landscape&client_id=$UNSPLASH_ACCESS_KEY" \
      | "${pkgs.jq}/bin/jq" -r '.urls.raw')

    if [ -z "$URL" ] || [ "$URL" = "null" ]; then
      echo "Error: could not retrieve Unsplash URL"
      exit 1
    fi

    EXT=$("${pkgs.coreutils}/bin/basename" "$URL" | "${pkgs.gawk}/bin/awk" -F. '{print tolower($NF)}')
    [[ "$EXT" =~ ^(jpg|jpeg|png)$ ]] || EXT="jpg"

    TMPFILE_EXT="$TMPFILE.$EXT"
    OUTFILE="$WALLPAPER_DIR/$("${pkgs.coreutils}/bin/date" +%Y%m%d-%H%M%S).webp"

    echo "Downloading original Unsplash image..."
    "${pkgs.curl}/bin/curl" -L --fail --retry 3 -o "$TMPFILE_EXT" "$URL"

    echo "Converting to WebP..."
    "${pkgs.libwebp}/bin/cwebp" -mt -preset photo -hint photo -metadata all -pass 10 -quiet -q 80 -m 6 "$TMPFILE_EXT" -o "$OUTFILE"
    "${pkgs.coreutils}/bin/rm" -f "$TMPFILE_EXT"

    echo "Selecting a wallpaper different from current..."
    CURRENT_WALL=$("${pkgs.hyprland}/bin/hyprctl" hyprpaper listloaded | "${pkgs.gawk}/bin/awk" '{print $NF}' || true)
    NEW_WALL=$("${pkgs.findutils}/bin/find" "$WALLPAPER_DIR" -type f ! -name "$("${pkgs.coreutils}/bin/basename" "$CURRENT_WALL")" | "${pkgs.coreutils}/bin/shuf" -n 1)

    echo "Reloading hyprpaper with: $NEW_WALL"
    "${pkgs.hyprland}/bin/hyprctl" hyprpaper reload ,"$NEW_WALL"
  '';
in
{
  # Ensure required packages are available
  home.packages = with pkgs; [
    coreutils
    curl
    findutils
    hyprland
    jq
    libwebp
  ];

  systemd.user.services."wallpaper-fetch" = {
    Unit = {
      Description = "Fetch and update 4K nature wallpaper for Hyprpaper";
    };
    Service = {
      LoadCredential = [ "login_token:${config.age.secrets.unsplash_access_key.path}" ];
      Type = "oneshot";
      ExecStart = "${wallpaperScript}";
    };
  };

  # Timer to run periodically (every 3 hours)
  systemd.user.timers."wallpaper-fetch" = {
    Unit = {
      Description = "Periodic Unsplash wallpaper fetch timer";
      After = [ "graphical-session.target" ];
      Wants = [ "network-online.target" ];
    };
    Timer = {
      OnBootSec = "2min";
      OnUnitActiveSec = "3h";
      Persistent = true;
    };
    Install = {
      WantedBy = [ "timers.target" ];
    };
  };
}