Add 4th Color to Appointments Table

Add the 4th Option(App+).php

// Add the 4th Option to the array 
function get_classes() {
        return apply_filters( 'app_box_class_names',
        array(
                'free'                  => __('Free', 'appointments'),
                'busy'                  => __('Busy', 'appointments'),
                'notpossible'   => __('Not possible', 'appointments'),
                // Add the option and description here
                'free_but_collision' => __(‘Free, but Collision', 'appointments')
                )
        );
}

App+ 4th Color Table.php

/**
* Special thanks to member Peter who contributed this
* check only if outside working hours (based on is_service_possible_function)
* Check if the time is inside working hours
* @return bool
*/

function is_service_outside_working_hours( $ccs, $cce, $capacity ) {

// If this cell exceeds app limit then return false
if ( $this->get_app_limit() < ceil( ( $ccs - $this->local_time ) /86400 ) )
        return false;

$result = $this->get_service( $this->service );
if ( !$result !== null ) {
        $duration = $result->duration;
        if( !$duration )
                return true; // This means min time will be applied. No need to look

        // The same for break time
        if ( isset( $this->options["allow_overwork_break"] ) && 'yes' == $this->options["allow_overwork_break"] )
                $allow_overwork_break = true;
        else
                $allow_overwork_break = false;

        // Now look where our working hour ends

        $days = wp_cache_get('app-open_times-for-' . $this->worker);
        if (!$days) {
                // Preprocess and cache workhours
                // Look where our working hour ends
                $result_days = $this->get_work_break($this->location, $this->worker, 'open');
                if ($result_days && is_object($result_days) && !empty($result_days->hours)) $days = maybe_unserialize($result_days->hours);
                if ($days) wp_cache_set('app-open_times-for-' . $this->worker, $days);
        }
        if (!is_array($days) || empty($days)) return true;

        // If overwork is allowed, lets mark this
        if ( isset( $this->options["allow_overwork"] ) && 'yes' == $this->options["allow_overwork"] )
                $allow_overwork = true;
        else
                $allow_overwork = false;

        // What is the name of this day?
        $this_days_name = date("l", $ccs );
        // This days midnight
        $this_day = date("d F Y", $ccs );
        // Will the service exceed or working time?
        $css_plus_duration = $ccs + ($duration *60);

        foreach( $days as $day_name=>$day ) {
                if ( $day_name == $this_days_name && isset( $day["active"] ) && 'yes' == $day["active"] ) {

                        // Special case: End time is 00:00
                        $end_mil = $this->to_military( $day["end"] );
                        if ( '00:00' == $end_mil )
                                $end_mil = '24:00';

                        if ( $allow_overwork ) {
                                if ( $ccs >= $this->str2time( $this_day, $end_mil ) )
                                        return false;
                        }
                        else if (  $ccs > $this->str2time( $this_day, $end_mil ) ) {
                                        return false;
                        }                            
                        else if (  $css_plus_duration > $this->str2time( $this_day, $end_mil ) ) {
                                        return true;
                        }

                        // We need to check a special case where schedule starts on eg 4pm, but our work starts on 4:30pm.
                        if ( $ccs < strtotime( $this_day . " " . $this->to_military( $day["start"] ) , $this->local_time ) )
                                return false;
                }
        }

        }
    return true;
}      

Improve Logic.php

# Line #2371 in `Appointments.php` changed from: 
# ======================== 
                      else if ( !$this->is_service_possible( $ccs, $cce, $capacity ) ) 
                              $class_name = 'notpossible service_notpossible'; 
                            
# changed to: 
#============= 
                      // Then check if the time window is inside working hours
                      else if ( !$this->is_service_outside_working_hours( $ccs, $cce, $capacity ) ) 
                            $class_name = 'notpossible'; 
                      // Then check if we have enough time to fulfill this app 
                      else if ( !$this-> is_service_possible( $ccs, $cce, $capacity ) ) 
                            $class_name = 'free_but_collision';

New is_possible function.php

# changed "is_possible fuction" to two independent functions (used in step 2) to check working hours and pre-appointment collisions independently

/**
 * Special thanks to member Peter who contributed this
 * Edited by moving the working hour checks to independent function 'is_service_outside_working_hours' below
 * Check if time is enough for this service
 * e.g if we are working until 6pm, it is not possible to take an app with 60 mins duration at 5:30pm
 * Please note that "not possible" is an exception
 * @return bool
 */
function is_service_possible( $ccs, $cce, $capacity ) {

        $result = $this->get_service( $this->service );
        if ( !$result !== null ) {
                $duration = $result->duration;
                if( !$duration )
                        return true; // This means min time will be applied. No need to look

            // The same for break time
            if ( isset( $this->options["allow_overwork_break"] ) && 'yes' == $this->options["allow_overwork_break"] )
                    $allow_overwork_break = true;
            else
                    $allow_overwork_break = false;

            // Check for further appointments or breaks on this day, if this is a lasting appointment
            if ( $duration > $this->get_min_time() ) {
                $step = ceil( $duration/$this->get_min_time() );
                $min_secs = $this->get_min_time() *60;
                if ( $step < 20 ) { // Let's not exaggerate !
                    for ( $n =1; $n < $step; $n++ ) {
                        if ( $this->is_busy( $ccs + $n * $min_secs, $ccs + ($n+1) * $min_secs, $capacity ) )
                                return false; // There is an appointment in the predeeding times
                        // We can check breaks here too
                        if ( !$allow_overwork_break ) {
                                if ( $this->is_break( $ccs + $n * $min_secs, $ccs + ($n+1) * $min_secs ) )
                                        return false; // There is a break in the predeeding times
                        }
                    }
                }
            }


        // Now look where our working hour ends

        $days = wp_cache_get('app-open_times-for-' . $this->worker);
        if (!$days) {
                // Preprocess and cache workhours
                // Look where our working hour ends
                $result_days = $this->get_work_break($this->location, $this->worker, 'open');
                if ($result_days && is_object($result_days) && !empty($result_days->hours)) $days = maybe_unserialize($result_days->hours);
                if ($days) wp_cache_set('app-open_times-for-' . $this->worker, $days);
        }
        if (!is_array($days) || empty($days)) return true;

        // If overwork is allowed, lets mark this
        if ( isset( $this->options["allow_overwork"] ) && 'yes' == $this->options["allow_overwork"] )
                $allow_overwork = true;
        else
                $allow_overwork = false;

        // What is the name of this day?
        $this_days_name = date("l", $ccs );
        // This days midnight
        $this_day = date("d F Y", $ccs );
        // Will the service exceed or working time?
        $css_plus_duration = $ccs + ($duration *60);

        foreach( $days as $day_name=>$day ) {
            if ( $day_name == $this_days_name && isset( $day["active"] ) && 'yes' == $day["active"] ) {

                // Special case: End time is 00:00
                $end_mil = $this->to_military( $day["end"] );
                if ( '00:00' == $end_mil )
                        $end_mil = '24:00';

                if ( $allow_overwork ) {
                        if ( $ccs >= $this->str2time( $this_day, $end_mil ) )
                                return false;
                }               
                else if (  $css_plus_duration > $this->str2time( $this_day, $end_mil ) ) {
                                return false;
                }
                // We need to check a special case where schedule starts on eg 4pm, but our work starts on 4:30pm.
                if ( $ccs < strtotime( $this_day . " " . $this->to_military( $day["start"] ) , $this->local_time ) )
                        return false;
            }
        }


        }
        return true;
}