Parse time references

[dcastro]

Clarification and motivation

We need to be able to parse references to points in time from Slack messages.

See the parseTimeRefs and TimeReference

A TimeReference should always contain a "time of day", which can be expressed using a 12-hour format:

Does 10am work for you?

That doesn't work for me, what about 10:30 AM?

Or a 24-hour format:

I can only be there at 16:00

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It may also contain a reference to a certain day.

That reference can be expressed as:

• "today" / "tomorrow" / "yesterday"

  10am tomorrow today at 3pm

• a number of days from today

  10am in 2 days

• a day of the week

  tuesday at 3pm at 3pm on tuesday

• a day of the month

  at 11am on the 4th

• a day of the month + a month

  at 11am on the 4th of April at 11am on April 4 at 11am on 4 April

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It may also contain a reference to a certain timezone or timezone abbreviation or offset.

• Timezone. See tzNameLabelMap for a list of all available timezone names.

  9am in europe/london

• Timezone abbreviation. For simplicity, we should consider any all-uppercase 2-5 letter word a timezone abbreviation (except AM and PM, of course). Validation of the timezone abbreviation will happen in a separate issue.

  2pm CST

• Offset.

  10am UTC+03:00 10am UTC+3

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A slack message may contain more than one reference, e.g.:

Let's meet between 10am and 11:30am

Acceptance criteria

• The parseTimeRefs function has been implemented and is able to parse the examples above.
• We don't need to be able to support all examples in one go - it's fine to submit a PR with support for some cases, and then iterate on that.