Date Parser

10 Points

Instructions

You have been tasked to write a service which ingests events. Each event has a date associated with it, but you notice that 3 different formats are being submitted to your service's endpoint:

"01/01/1970"
"January 1, 1970"
"Thursday, January 1, 1970"

You can see there are some similarities between each of them, and decide to write some composable regular expression patterns.

1. Match the day, month, and year from a date

Implement day/0, month/0, and year/0 to return a string pattern which, when compiled, would match the numeric components in "01/01/1970" (dd/mm/yyyy). The day and month may appear as 1 or 01 (left padded with zeroes).

"31" =~ DateParser.day() |> Regex.compile!()
# => true
"12" =~ DateParser.month() |> Regex.compile!()
# => true
"1970" =~ DateParser.year() |> Regex.compile!()
# => true

2. Match the day of the week and the month of the year

Implement day_names/0 and month_names/0 to return a string pattern which, when compiled, would match the named day of the week and the named month of the year respectively.

"Tuesday" =~ DateParser.day_names() |> Regex.compile!()
# => true
"June" =~ DateParser.month_names() |> Regex.compile!()
# => true

3. Capture the day, month, and year

Implement capture_day/0, capture_month/0, capture_year/0, capture_day_name/0, capture_month_name/0 to return a string pattern which captures the respective components to the names: "day", "month", "year", "day_name", "month_name"

DateParser.capture_month_name()
|> Regex.compile!()
|> Regex.named_captures("December")

# => %{"month_name" => "December"}

4. Combine the captures to capture the whole date

Implement capture_numeric_date/0, capture_month_name_date(), and capture_day_month_name_date/0 to return a string pattern which captures the components from part 3 using the respective date format:

numeric date - "01/01/1970"
month name date - "January 1, 1970"
day month name date - "Thursday, January 1, 1970"

DateParser.capture_numeric_date()
|> Regex.compile!()
|> Regex.named_captures("01/01/1970")

# => %{"day" => "01", "month" => "01", "year" => "1970"}

5. Narrow the capture to match only on the date

Implement match_numeric_date/0, match_month_name_date/0, and match_day_month_name_date/0 to return a compiled regular expression that only matches the date, and which can also capture the components.

"Thursday, January 1, 1970 was the Unix epoch." =~ DateParser.match_day_month_name_date()
# => false
"Thursday, January 1, 1970" =~ DateParser.match_day_month_name_date()
# => true

DateParser.match_day_month_name_date()
|> Regex.named_captures("Thursday, January 1, 1970")

# => %{
#     "day" => "1",
#     "day_name" => "Thursday",
#     "month_name" => "January",
#     "year" => "1970"
#   }

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