blomarchy/bin/blob-brightness-ddc

#!/bin/bash

# blob:summary=Show or adjust DDC/CI display brightness for a Hyprland monitor.
# blob:args=<monitor> [+N%|N%-|N%]
# blob:examples=blob-brightness-ddc DP-1 | blob-brightness-ddc DP-1 50%

monitor="${1:-}"
step="${2:-}"

[[ -n $monitor ]] || exit 1

cache_dir="${XDG_RUNTIME_DIR:-/tmp}/blob-brightness-ddc"
cache_name="${monitor//[^[:alnum:]_.-]/_}"
cache_file="$cache_dir/$cache_name.bus"
unavailable_cache_seconds=60
range_cache_seconds=10

cache_unavailable() {
  mkdir -p "$cache_dir" 2>/dev/null || true
  printf 'unavailable %s\n' "$(date +%s)" >"$cache_file" 2>/dev/null || true
}

detect_bus() {
  ddcutil --skip-ddc-checks detect --brief 2>/dev/null | awk -v monitor="$monitor" '
    /I2C bus:/ {
      bus = $NF
      sub(/^.*\/i2c-/, "", bus)
    }

    /DRM connector:/ {
      connector = $NF
      sub(/^card[0-9]+-/, "", connector)
      if (connector == monitor && bus != "") {
        print bus
        exit
      }
      bus = ""
    }
  '
}

find_bus() {
  local bus=""
  local cached_value=""
  local now=0

  if [[ -r $cache_file ]]; then
    read -r bus cached_value <"$cache_file" || true
  fi

  if [[ $bus == "unavailable" ]]; then
    now=$(date +%s)
    if [[ $cached_value =~ ^[0-9]+$ ]] && (( now - cached_value < unavailable_cache_seconds )); then
      return 1
    fi
    bus=""
    rm -f "$cache_file"
  fi

  if [[ -z $bus ]]; then
    bus="$(detect_bus)" || return 1
    if [[ ! $bus =~ ^[0-9]+$ ]]; then
      cache_unavailable
      return 1
    fi
    mkdir -p "$cache_dir" 2>/dev/null || true
    printf '%s\n' "$bus" >"$cache_file" 2>/dev/null || true
  fi

  printf '%s\n' "$bus"
}

read_vcp() {
  local bus="$1"

  ddcutil --bus "$bus" --skip-ddc-checks getvcp 10 --brief 2>/dev/null | awk '
    $1 == "VCP" && toupper($2) == "10" && $3 == "C" && $4 ~ /^[0-9]+$/ && $5 ~ /^[0-9]+$/ && $5 > 0 {
      print $4, $5
      found = 1
      exit
    }

    END { exit !found }
  '
}

read_brightness() {
  local bus=""
  local now=0
  local values=""

  bus="$(find_bus)" || return 1
  values="$(read_vcp "$bus")" || {
    rm -f "$cache_file"
    return 1
  }

  now=$(date +%s)
  mkdir -p "$cache_dir" 2>/dev/null || true
  printf '%s %s %s\n' "$bus" "${values##* }" "$now" >"$cache_file" 2>/dev/null || true
  printf '%s %s\n' "$bus" "$values"
}

bus=""
current=""
maximum=""
percent=""
range_cached_at=""

if [[ -z $step ]]; then
  read -r bus current maximum < <(read_brightness) || exit 1
  [[ -n ${bus:-} && -n ${current:-} && -n ${maximum:-} ]] || exit 1
  (( percent = (current * 100 + maximum / 2) / maximum ))
  printf '%s\n' "$percent"
  exit 0
fi

if [[ $step =~ ^([0-9]+)%$ ]]; then
  target="${BASH_REMATCH[1]}"
  range_cache_fresh=0
  if [[ -r $cache_file ]]; then
    read -r bus maximum range_cached_at <"$cache_file" || true
  fi

  if [[ $bus =~ ^[0-9]+$ && $maximum =~ ^[0-9]+$ && $range_cached_at =~ ^[0-9]+$ ]] && (( maximum > 0 )); then
    now=$(date +%s)
    if (( range_cached_at <= now && now - range_cached_at < range_cache_seconds )); then
      range_cache_fresh=1
    fi
  fi

  if (( ! range_cache_fresh )); then
    read -r bus current maximum < <(read_brightness) || exit 1
  fi
elif [[ $step =~ ^\+([0-9]+)%$ ]]; then
  read -r bus current maximum < <(read_brightness) || exit 1
  [[ -n ${bus:-} && -n ${current:-} && -n ${maximum:-} ]] || exit 1
  (( percent = (current * 100 + maximum / 2) / maximum ))
  amount="${BASH_REMATCH[1]}"
  if (( amount == 5 && percent < 5 )); then
    (( target = percent + 1 ))
  else
    (( target = percent + amount ))
  fi
elif [[ $step =~ ^([0-9]+)%-$ ]]; then
  read -r bus current maximum < <(read_brightness) || exit 1
  [[ -n ${bus:-} && -n ${current:-} && -n ${maximum:-} ]] || exit 1
  (( percent = (current * 100 + maximum / 2) / maximum ))
  amount="${BASH_REMATCH[1]}"
  if (( amount == 5 && percent <= 5 )); then
    (( target = percent - 1 ))
  else
    (( target = percent - amount ))
  fi
else
  exit 1
fi

(( target < 1 )) && target=1
(( target > 100 )) && target=100
(( raw_target = (target * maximum + 50) / 100 ))

if ! ddcutil --bus "$bus" --skip-ddc-checks --noverify setvcp 10 "$raw_target" >/dev/null 2>&1; then
  rm -f "$cache_file"
  exit 1
fi

printf '%s\n' "$target"