How to detect if dates are consecutive in Rails? - ruby-on-rails

Question

I'm looking to check for consecutive dates and display them differently if they are consecutive.
I'm working with Garage Sales that have multiple dates per sale. I'd like to then cycle through each date, and group any consecutive dates to display as a group: Ex: Apr 28 - Apr 30
I also need to account for non-consecutive dates:
Ex: Apr 15, Apr 28 - 30
Additionally, weekly dates need to be recognized as non-consecutive (so basically avoid step checks):
Ex: Apr 16, Apr 23, Apr 30
So far, I'm taking each date that hasn't passed & ordering them properly.
garage_sale_dates.where("date > ?",Time.now).order(:date)
Thanks for any help! Let me know if any other info is needed.

Answer 1

You can use the slice_before method of Enumerable
dates = [Date.yesterday, Date.today, Date.tomorrow, Date.parse('2016-05-01'), Date.parse('2016-05-02'), Date.parse('2016-05-05')]
# => [Wed, 27 Apr 2016, Thu, 28 Apr 2016, Fri, 29 Apr 2016, Sun, 01 May 2016, Mon, 02 May 2016, Thu, 05 May 2016]
prev = dates.first
dates.slice_before { |d| prev, prev2 = d, prev; prev2 + 1.day != d }.to_a
# => [[Wed, 27 Apr 2016, Thu, 28 Apr 2016, Fri, 29 Apr 2016], [Sun, 01 May 2016, Mon, 02 May 2016], [Thu, 05 May 2016]]
Then you can simply join the 2-or-more-element arrays from the result with "-", and leave the single element arrays intact:
prev = dates.first
dates.slice_before { |d| prev, prev2 = d, prev; prev2 + 1.day != d }.
map{|d| d.size > 1 ? "#{d.first.to_s} - #{d.last.to_s}" : d.first.to_s }
# => ["2016-04-27 - 2016-04-29", "2016-05-01 - 2016-05-02", "2016-05-05"]
There is even a commented example in the docs that is technically equivalent to yours (but deals with integers, not dates).

Answer 2

a simple script would do the trick
def date_list(dates)
result = []
dates.each do |date|
if result.empty? || (date - result.last.last).to_i != 1
result << [date]
else
result.last << date
end
end
result
end
# make sure dates is an array of dates
dates = [Thu, 28 Apr 2016, Fri, 29 Apr 2016, Sun, 01 May 2016, Mon, 02 May 2016, Tue, 03 May 2016, Thu, 05 May 2016, Fri, 06 May 2016, Sat, 07 May 2016, Sun, 08 May 2016]
#this would give you an array of date ranges that you wanted
date_list(dates)
=> [
[Thu, 28 Apr 2016, Fri, 29 Apr 2016],
[Sun, 01 May 2016, Mon, 02 May 2016, Tue, 03 May 2016],
[Thu, 05 May 2016, Fri, 06 May 2016, Sat, 07 May 2016, Sun, 08 May 2016]
]

Answer 3

I found a simpler solution using chunk_while method (available from Ruby 2.4.6).
Based on BoraMa answer:
dates = [Date.yesterday, Date.today, Date.tomorrow, Date.parse('2020-05-01'), Date.parse('2020-05-02'), Date.parse('2020-05-05')]
# => [Thu, 26 Mar 2020, Fri, 27 Mar 2020, Sat, 28 Mar 2020, Fri, 01 May 2020, Sat, 02 May 2020, Tue, 05 May 2020]
dates.chunk_while { |date_before, date_after| (date_after - date_before).to_i == 1 }.to_a
# => [[Thu, 26 Mar 2020, Fri, 27 Mar 2020, Sat, 28 Mar 2020], [Fri, 01 May 2020, Sat, 02 May 2020], [Tue, 05 May 2020]]
I think is more readable and it needs less steps to get same result.

Answer 4

Using a Date you can do the subtraction, it would be something like:
date1 = 1.day.ago
date2 = 2.day.ago
(date1.to_date - date2.to_date).to_i
=> 1

Answer 5

Adding onto Matouš Borák's answer, if you want to change the date format such that it would match what was asked in the question i.e. Apr 15, Apr 28 - 30
dates = [Date.yesterday, Date.today, Date.tomorrow, Date.parse('2021-10-01'), Date.parse('2021-10-02'), Date.parse('2021-10-05')]
# => [Wed, 01 Sep 2021, Thu, 02 Sep 2021, Fri, 03 Sep 2021, Fri, 01 Oct 2021, Sat, 02 Oct 2021, Tue, 05 Oct 2021]
prev = dates.first
dates.slice_before { |d| prev, prev2 = d, prev; prev2 + 1.day != d }.
map{|d| d.size > 1 ? "#{d.first.strftime('%b %d')} - #{d.last.strftime('%d')}" : d.first.strftime('%b %d') }
# => ["Sep 01 - 03", "Oct 01 - 02", "Oct 05"]