#!/bin/bash

# blob:summary=Assign a wallpaper to one monitor, leaving the others alone
# blob:args=<--list|--clear-all|<output> <image>|<output> --clear>
# blob:examples=blob bg monitor DP-1 ~/wallpapers/astronaut2.jpg

set -e

state_dir="$HOME/.local/state/blob/backgrounds"
mkdir -p "$state_dir"

usage() {
  cat <<USAGE
Usage: blob-bg-monitor <output> <image>     assign a wallpaper to one monitor
       blob-bg-monitor <output> --clear     fall back to the global wallpaper
       blob-bg-monitor --list               show current assignments
       blob-bg-monitor --clear-all          drop every assignment

Monitors with no assignment show the global wallpaper set by blob-bg-set.
Output names are what 'hyprctl monitors' reports, such as DP-1 or eDP-1.
USAGE
}

notify_shell() {
  blob-shell -q background refresh
}

known_output() {
  hyprctl monitors all -j 2>/dev/null | jq -e --arg name "$1" 'any(.[]; .name == $name)' >/dev/null
}

case "${1-}" in
--list)
  found=false
  for link in "$state_dir"/*; do
    [[ -e $link ]] || continue
    found=true
    printf '%-12s %s\n' "$(basename "$link")" "$(readlink -f "$link")"
  done
  [[ $found == true ]] || echo "No per-monitor wallpapers assigned."
  exit 0
  ;;
--clear-all)
  rm -f "$state_dir"/*
  notify_shell
  echo "Cleared every per-monitor wallpaper."
  exit 0
  ;;
""|--help|-h)
  usage
  exit 0
  ;;
esac

output="$1"
image="${2-}"

if [[ -z $image ]]; then
  usage >&2
  exit 1
fi

if ! known_output "$output"; then
  echo "Warning: '$output' is not a connected monitor right now." >&2
fi

if [[ $image == --clear ]]; then
  rm -f "$state_dir/$output"
  notify_shell
  echo "Cleared $output; it follows the global wallpaper again."
  exit 0
fi

if [[ ! -f $image ]]; then
  echo "Not a file: $image" >&2
  exit 1
fi

ln -sfn "$(realpath "$image")" "$state_dir/$output"
notify_shell
echo "Set $output to $(basename "$image")"