#!/usr/bin/env bash

set -e

bail() {
    echo "Error: $@" >&2
    echo "Exiting..." >&2
    exit 1
}

map_range() {
    VALUE="$1"
    MIN_INPUT="$2"
    MAX_INPUT="$3"
    INPUT_RANGE=$(( $MAX_INPUT - $MIN_INPUT ))
    MIN_OUTPUT="$4"
    MAX_OUTPUT="$5"
    OUTPUT_RANGE=$(( $MAX_OUTPUT - $MIN_OUTPUT ))

    echo $(( ($VALUE - $MIN_INPUT) * $OUTPUT_RANGE / $INPUT_RANGE  + $MIN_OUTPUT ))
}

clamp() {
    VALUE="$1"

    MIN="$2"
    MAX="$3"

    VALUE=$VALUE
    if [ "$VALUE" -gt $MAX ]; then
        VALUE=$MAX
    elif [ "$VALUE" -lt $MIN ]; then
        VALUE=$MIN
    fi

    echo $VALUE
}

cleanup() {
    echo "Setting controll to auto" >&2
    if test -f "$HWMON/pwm1_enable"; then
        echo 2 > "$HWMON/pwm1_enable"
    fi
}
trap cleanup EXIT INT

usage() {
    echo "Usage: $0 <device> <min-temp> <max-temp> <min-fan> <max-fan>" >&2
    echo "Example: $0 /sys/class/drm/card1/device 60 100 10 80" >&2
    exit 1
}

parse_cli() {
    if test -n "$AMDGPU_FAN_CRONTROL_DEBUG"; then
        echo parse_cli "$@" >&2
    fi

    DEVICE="$1" # eg: /sys/class/drm/card1/device
    HWMON=$(echo "$DEVICE"/hwmon/hwmon*)
    TEMP_INPUT="$HWMON/temp2_input"

    TEMP_MIN="$2"
    TEMP_MAX="$3"

    PWM_MIN_PCT="$4"
    PWM_MAX_PCT="$5"
}

validate_variables() {
    if ! [ -d "$HWMON" ]; then
        bail "Invalid drm-device: '$HWMON' is not a directory"
    fi

    if ! [ -f "$TEMP_INPUT" ]; then
        bail "Error: Could not find hotspot temperature at '$TEMP_INPUT'"
    fi

    if [ -z "$TEMP_MIN" -o -z "$TEMP_MAX" -o -z "$PWM_MIN_PCT" -o -z "$PWM_MAX_PCT" ];then
        usage
    fi
}

setup() {
    PWM_MIN=$(map_range $PWM_MIN_PCT 0 100 0 255)
    PWM_MAX=$(map_range $PWM_MAX_PCT 0 100 0 255)

    echo "Running..." >&2

    if test -n "$AMDGPU_FAN_CRONTROL_DEBUG"; then
        echo "TEMP_MIN=$TEMP_MIN°C" >&2
        echo "TEMP_MAX=$TEMP_MAX°C" >&2
        echo "FAN_MIN=$PWM_MIN_PCT% (PWM=$PWM_MIN)" >&2
        echo "FAN_MAX=$PWM_MAX_PCT% (PWM=$PWM_MAX)" >&2
    fi

    # Set fan control mode to manual, this will be reverted in the cleanup trap
    echo 1 > "$HWMON/pwm1_enable"

    PREV_PWM=0
}

main_loop() {
    TEMPERATURE_RAW=$(cat "$TEMP_INPUT")
    TEMPERATURE="$(( $TEMPERATURE_RAW / 1000 ))" # 60_000 = 60°C

    # Calculate the fan speed we would want to reach given infinite time
    TARGET_PWM=$(map_range $TEMPERATURE $TEMP_MIN $TEMP_MAX $PWM_MIN $PWM_MAX)

    # Calculate an appropriate amount to "walk" in the direction of target fan speed
    DIFFERENCE=$(( $TARGET_PWM - $PREV_PWM ))
    ADJUSTMENT=$(( $DIFFERENCE * 20 / 100 ))

    NEXT_PWM=$(( $PREV_PWM + $ADJUSTMENT ))

    NEXT_PWM=$(clamp $NEXT_PWM $PWM_MIN $PWM_MAX)
    NEXT_PWM_PCT=$(map_range $NEXT_PWM 0 255 0 100 )

    if test -n "$AMDGPU_FAN_CRONTROL_DEBUG"; then
        for var in \
            "Temperature=$TEMPERATURE°C" \
            "Fan speed=$NEXT_PWM_PCT%" \
        ; do
            echo -en "$var\t"
        done
        echo
    fi

    # Apply the new fan speed
    echo "$NEXT_PWM" > "$HWMON/pwm1"

    # Wait for next iteratino
    PREV_PWM="$NEXT_PWM"
    sleep .1s
}

main() {
    parse_cli "$@"
    validate_variables
    setup
    while true; do
        main_loop
    done
}

main "$@"