#!/bin/bash
DEBUG="${DEBUG-0}"
FADING="${FADING-1}"

DEV_CHECK="/dev/snd/timer"


FADE_DELAY="0.05"
FADE_STEPS=5

DEFAULT_SOFTVOL=""
EXIT=0

#####################################################################
trap exit_handler SIGINT
trap exit_handler EXIT

#### softvol handling ####
exit_handler()
{
    if [[ "$EXIT" == "0" ]]; then
        EXIT=1
        if [[ "$FADING" == "1" ]]; then
            is_empty "$DEFAULT_SOFTVOL" || set_softvol "$DEFAULT_SOFTVOL"
        fi
    fi
    exit
}

set_softvol()
{
    if [[ "$(get_softvol)" != "$1" ]]; then
        debug "Setting softvol to $1"
        cmus-remote -C "set softvol=$1"
    fi
}

get_softvol()
{
    cmus-remote -Q | grep softvol | cut -f3 -d\
}

#####################################################################
#### generic output functions ####
error()
{
    echo "error: $1" > /dev/stderr
}

debug()
{
    [[ "$DEBUG" == "1" ]] && echo "debug: $1"
}

is_empty()
{
    [[ -z "$1" ]]
}

#####################################################################
#### cmus functions ####
cmus_set_volume()
{
    vol="$1"
    cmus-remote -v "$vol"
    return 0
}

cmus_get_volume()
{
    vol="$(cmus-remote -C status| grep vol_left | cut -f3 -d\   )"
    is_empty "$vol" && return 1
    echo "$vol"
    return 0
}


cmus_play()
{
    cmus-remote --play
}

cmus_stop()
{
    cmus-remote --stop
}

cmus_pause()
{
    cmus-remote --pause
}

cmus_status()
{
    cmus-remote -C status | head -n 1 | cut -f2 -d\
}

cmus_paused()
{
    [[ "$(cmus_status)" == "paused" ]]
}

cmus_playing()
{
    [[ "$(cmus_status)" == "playing" ]]
}

cmus_stopped()
{
    [[ "$(cmus_status)" == "stopped" ]]
}

cmus_running()
{
    [[ ! -z "$(cmus_pid)" ]]
}

cmus_pid()
{
    pid="$(pidof cmus 2> /dev/null)"
    is_empty "$pid" && return 1
    echo "$pid"
    return 0
}


#####################################################################
#### generic cmus functions ####
play()
{
    if cmus_paused; then
        cmus_pause
    elif cmus_stopped; then
        cmus_play
    fi
}

pause()
{
    cmus_playing && cmus_pause
}


#####################################################################
#### fading functions ####

fade_out()
{
    if [[ "$FADING" != "1" ]]; then
        pause
        return 0
    fi

    debug "fading out"
    vol="$(cmus_get_volume)"
    init_vol="$vol"
    is_empty "$vol" && return 0

    while (( vol > 0 )); do
        cmus_set_volume "$((vol-=FADE_STEPS))"
        sleep "$FADE_DELAY"
    done

    pause
    cmus_set_volume "$init_vol"

    return 0
}

fade_in()
{
    if [[ "$FADING" != "1" ]]; then
        play
        return 0
    fi

    debug "fading in"
    target_vol="$(cmus_get_volume)"
    is_empty "$target_vol" && return 0
    vol=0

    cmus_set_volume "$vol"
    play

    while (( vol < target_vol )); do
        cmus_set_volume "$vol"
        sleep "$FADE_DELAY"
        (( vol+=3 ))
    done

    cmus_set_volume "$target_vol"

    return 0
}


#####################################################################
# either cmus should be playing  or not
have_another_client()
{
    cmus="$(cmus_pid)"
    is_empty "$cmus" && ( error "cmus is not running"; exit 1 )

    pids="$(fuser "$DEV_CHECK" 2> /dev/null)"

    for i in $pids; do
        if [[ "$i" != "$cmus" ]]; then
            debug "found at least one more client pid: $i (cmus: $cmus)"
            return 0
        fi
    done

    return 1
}


# check if anything has changed on the usage of pcm devices
AUDIO_UNDEFINED=0
AUDIO_CLOSED=1
AUDIO_OPENED=2

poll_statechange()
{
    ret="$(inotifywait -q --format="% e" -e close -e open "$DEV_CHECK")"
    debug "inotifywait fired"
    # the following should be useless for now
    for i in $ret; do
        [[ "$i" == "CLOSE" ]] && return $AUDIO_CLOSED
        [[ "$i" == "OPEN" ]]  && return $AUDIO_OPENED
    done
    return $AUDIO_UNDEFINED
}


# set current state of cmus
setup_cmus()
{
    # PID of cmus
    cmus_running || ( error "cmus is not running"; exit 1 )

    if have_another_client; then
        debug "another client"
        cmus_playing && fade_out
    else
        debug "no other client"
        cmus_playing || fade_in
    fi

    return 1
}

#####################################################################
###  Main  ###
if [[ ! -e "$DEV_CHECK" ]]; then
    error "$DEV_CHECK does not exist"
    exit 1
fi

if [[ "$FADING" == "1" ]]; then
    DEFAULT_SOFTVOL="$(get_softvol)"
    if [[ "$DEFAULT_SOFTVOL" == "false" ]]; then
        set_softvol "true"
    fi
fi


while true; do
    poll_statechange &
    setup_cmus
    wait
done