fanctrl

#!/bin/sh

set -e

# $1: temperature in tenths of a degree (e.g. 282 = 28.2°C)
# returns rounded interpolated int
lerp_fan_speed()
{
	temp=$1
	low_temp=
	high_temp=
	low_speed=
	high_speed=

	while IFS='=' read -r t speed # get proper range
	do
		[ -n "$t" ] || continue

		# Curve temperatures are specified in whole degrees.
		t=$((t * 10))

		if [ "$t" -le "$temp" ] &&
			{ [ -z "$low_temp" ] || [ "$t" -gt "$low_temp" ]; }; then
			low_temp=$t
			low_speed=$speed
		fi

		if [ "$t" -ge "$temp" ] &&
			{ [ -z "$high_temp" ] || [ "$t" -lt "$high_temp" ]; }; then
			high_temp=$t
			high_speed=$speed
		fi
	done <<EOF
$FAN_CURVE
EOF

	if [ -z "$low_temp" ]; then # Below the lowest curve point.
		echo "$high_speed"
	elif [ -z "$high_temp" ] || [ "$high_temp" -eq "$low_temp" ]; then 	# At or above the highest curve point, or exact curve point.
		echo "$low_speed"
	else # Linear interpolation rounded to the nearest integer.
		numerator=$(( (high_speed - low_speed) * (temp - low_temp) ))
		denominator=$(( high_temp - low_temp ))

		speed=$(( (numerator + denominator / 2) / denominator ))
		echo $((low_speed + speed))
	fi
}

evl()
{
	# echo "evl: [$*]" >&2
	exec "$AWK" "BEGIN { print $* }"
}

SET_FAN_SPEED_CMD="$SCRIPT_DIR/commands/set-fan-speed"

if [ ! -x "$SET_FAN_SPEED_CMD" ]; then
	echo "Error: $SET_FAN_SPEED_CMD is not present. Try creating it or use existing one with use.sh"
	exit 1
fi

for f in "$SCRIPT_DIR"/includes/* "$SCRIPT_DIR"/includes/.*; do
	# shellcheck source=/dev/null
	[ -f "$f" ] && . "$f"
done

cd "$SCRIPT_DIR" 

prev_speed=0
for fan in "$SCRIPT_DIR"/fans/*
do
	fan_name=${fan##*/}
	if [ "$fan_name" != "${fan_name#_}" ] || [ ! -f "$fan" ]; then # skip disabled fans (_ prefix) and anything that isn't an actual fan config file
		continue
	fi

	# shellcheck source=/dev/null
	. "$fan"
	# echo "$SENSOR_CMD" "$FAN_CURVE"

	if [ -z "$SENSOR_CMD" ]; then
		echo "Error: SENSOR_CMD is not specified for fan '$fan_name', skipping..."
		continue
	fi

	if [ -z "$FAN_CURVE" ]; then
		echo "Error: FAN_CURVE is not specified for fan '$fan_name', skipping..."
		continue
	fi

	temp=$(eval "$SENSOR_CMD")
	if [ -z "$temp" ]; then
		continue
	fi

	# Convert sensor temperature to tenths of a degree.
	int_part=${temp%%.*}
	frac_part=${temp#*.}

	if [ "$frac_part" = "$temp" ]; then
		frac_part=0
	else
		frac_part=${frac_part%?}
	fi

	int_temp=$((int_part * 10 + frac_part))

	speed=$(lerp_fan_speed "$int_temp")
	if [ -n "$NEIGHBOR_FAN_OFFSET" ] && [ "$prev_speed" -eq "$speed" ]; then
		speed="$((speed + NEIGHBOR_FAN_OFFSET))"
	fi

	cache_file="$CACHE_DIR/$fan_name"
	if [ -f "$cache_file" ]; then
		read -r cached_speed < "$cache_file"
		if [ "$cached_speed" -eq "$speed" ]; then
			prev_speed=$speed
			continue
		fi
	fi

	# clamp for safety, in case the curve is misconfigured
	if [ "$speed" -lt "${DEFAULT_MIN_SPEED:-5}" ]; then
		speed=${DEFAULT_MIN_SPEED:-5}
	elif [ "$speed" -gt "${DEFAULT_MAX_SPEED:-100}" ]; then
		speed=${DEFAULT_MAX_SPEED:-100}
	fi

	# echo "Set fan '$fan_name' to $speed% ($SENSOR_CMD: $temp)"

	"$SET_FAN_SPEED_CMD" "$fan_name" "$speed"
	echo "$speed" > "$cache_file"

	prev_speed=$speed
done