Google Calendar API算法可查找特定日期的开放时间段

Question

I'm trying to leverage Google Calendar (and Google Calendar API) for simple scheduling. I'm using PHP, MySQL and google-api-php-client. I'm looking for a algorithm or pseudocode to find open time slots.

My calendar has events for busy times such as when business is closed and for current appointments. I am able to retrieve event start and end times via two function (Events: list and Freebusy: query). Here is a example list of events for today with start time of 2016-02-19T01:00:00-07:00 and end time of 2016-02-19T23:00:00-07:00 (everything for the current day).

Business is Closed from 12:00am to 11:00am
start: "2016-02-19T00:00:00-07:00"
end: "2016-02-19T11:00:00-07:00"

Appointment from 1:30pm to 2:30pm
start: "2016-02-19T13:30:00-07:00"
end: "2016-02-19T14:30:00-07:00"

Appointment from 5:00pm to 7:00pm
start: "2016-02-19T17:00:00-07:00"
end: "2016-02-19T19:00:00-07:00"

Appointment from 9:00pm to 11:00pm
start: "2016-02-19T21:00:00-07:00"
end: "2016-02-19T23:00:00-07:00"

My open time slots based on this example event set is: 11:00am to 1:30pm, 2:30pm to 5:00pm, 7:00pm to 9:00pm and 11:00pm to 12:00am.

1. How do I find this set of times programmatically?

Ideally I would like to get a full list of events for a given day with one API call and interpret/manipulate the list instead of making many calls with specific start and end times which would give me the information I'm looking for but be very inefficient.

1. After I find the set, how do I display results in 30 minute increments i.e. available appointment start times are:

11:00,11:30,12:00,12:30,1:00,2:30,3:00,3:30,4:00,4:30,9:00,9:30,10:00,10:30,11:00,11:30

I'm having a hard time wrapping my head around working with dates/time data sets.

Here is an image of the Google Calendar. Date in question is 2/19/2016

Thank you kindly. Any source that is a result of this discussion will be posted for reference.

Answer 1

I would convert the dates to unix timestamps and calculate the difference between the start and end dates. This is how I would accomplish the first part of your question:

$events = array(
    array(
        'start' => '2016-02-19T00:00:00-07:00',
        'end' => '2016-02-19T11:00:00-07:00'
    ),
    array(
        'start' => '2016-02-19T13:30:00-07:00',
        'end' => '2016-02-19T14:30:00-07:00'
    ),
    array(
        'start' => '2016-02-19T17:00:00-07:00',
        'end' => '2016-02-19T19:00:00-07:00'
    ),
    array(
        'start' => '2016-02-19T21:00:00-07:00',
        'end' => '2016-02-19T23:00:00-07:00'
    )
);

$free_time_slots = array();
$count = count($events)-1;
$i = 0;
foreach($events as $event) {
    if ($i < $count) {
        $free_time = strtotime($events[$i+1]['start']) - strtotime($event['end']);
        $free_time_slots[] = array(
            'start' => date("F j, Y, g:i a", strtotime($event['end'])),
            'end' => date("F j, Y, g:i a", strtotime($events[$i+1]['start'])),
            'minutes' => $free_time / 60
        );
        $i++;
    }
}  
echo '<pre>';
print_r($free_time_slots);

Which will result in this:

Array
(
    [0] => Array
        (
            [start] => February 19, 2016, 11:00 am
            [end] => February 19, 2016, 1:30 pm
            [minutes] => 150
        )

    [1] => Array
        (
            [start] => February 19, 2016, 2:30 pm
            [end] => February 19, 2016, 5:00 pm
            [minutes] => 150
        )

    [2] => Array
        (
            [start] => February 19, 2016, 7:00 pm
            [end] => February 19, 2016, 9:00 pm
            [minutes] => 120
        )

)