{- This file is part of Vervis.
-
- Written in 2016 by fr33domlover <fr33domlover@riseup.net>.
-
- ♡ Copying is an act of love. Please copy, reuse and share.
-
- The author(s) have dedicated all copyright and related and neighboring
- rights to this software to the public domain worldwide. This software is
- distributed without any warranty.
-
- You should have received a copy of the CC0 Public Domain Dedication along
- with this software. If not, see
- <http://creativecommons.org/publicdomain/zero/1.0/>.
-}
-- | Representation and display of events times between seconds and years ago.
-- Currently the display is in terms of how much time passed since the event,
-- but more display modes can be added.
module Data.EventTime.Local
( -- * Event time types
TimeUnit (..)
, TimeAgo (..)
, EventTime (..)
-- * Conversion from time types
-- ** Interval conversion
-- *** Typeclass
, IntervalToEventTime (..)
-- *** Human friendly conversion adapters
, RoundDown (..)
, RoundNear (..)
, RoundDownWait (..)
, RoundNearWait (..)
, FriendlyConvert (..)
-- ** Time conversion
, SpecToEventTime (..)
-- * Display
, showEventTime
)
where
import Prelude
import Data.Text (Text, snoc)
import Text.Blaze (ToMarkup (..))
import qualified Formatting as F
-------------------------------------------------------------------------------
-- Event time types
-------------------------------------------------------------------------------
data TimeUnit = Second | Minute | Hour | Day | Week | Month | Year
data TimeAgo = TimeAgo
{ taUnit :: TimeUnit
, taCount :: Int
}
data EventTime = Now | Ago TimeAgo | Never
instance ToMarkup EventTime where
toMarkup = toMarkup . showEventTime
-------------------------------------------------------------------------------
-- Conversion from time types
-------------------------------------------------------------------------------
-- | Given a time interval representing how much time passed since an event, it
-- can be converted into an 'EventTime'. This is a class for time interval
-- types which support such a conversion.
--
-- There is a default convetion for mapping time intervals to the human
-- friendly event time form. Other conventions can be easily added by defining
-- newtype wrappers for new conventions and making them instances of this
-- class. The purpose of the default convention if to make the actual human
-- friendly conventions easy to implement on top, and isn't expected to be
-- useful directly for display in UI.
--
-- The default convention works like this:
--
-- (1) Use a 1 step higher resolution unit that you normally would, but don't
-- use weeks and months at all (express years in days)
-- (2) Round downwards. Rounding to the closest integer is fine too and makes
-- the error smaller, but since higher resolution units are used, the
-- difference is small while rounding down is quicker to implement (integer
-- division does it for free).
--
-- The conversions made using this mechanism aren't accurate, e.g. they don't
-- necessarily take into account that in some years there are 29 days in
-- February and so on, but these are small details which don't have a visible
-- effect on the human friendly display of event times. And even if in some
-- corner case they do, you can always implement an 'IntervalToEventTime'
-- instance for your specific needs.
--
-- Additional conventions:
--
-- * A duration of less than 1 second means 'Now'.
-- * Some time interval types may have a way to express "never", e.g. by using
-- a very high duration. But either way, this is just optional extra.
--
-- Here's an example for the default convention:
--
-- > -- Interval | Event time
-- > -- ============ + ==========
-- > -- 0 | Now
-- > -- 0.5 second | Now
-- > -- 1 second | 1 second
-- > -- 1 minute | 60 seconds
-- > -- 59 minutes | 3599 seconds
-- > -- 1 hour | 60 minutes
-- > -- 23 hours | 1380 minutes
-- > -- 1 day | 24 hours
-- > -- 364 days | 8736 hours
-- > -- 1 year | 365 days
-- > -- 10 years | 3650 days
-- > -- 100 years | 36500 days
class IntervalToEventTime i where
intervalToEventTime :: i -> EventTime
instance IntervalToEventTime EventTime where
intervalToEventTime = id
-- | Human friendly event time conversion. Renders a time interval rounded
-- down. Example:
--
-- > -- Interval | Event time
-- > -- ==================== + ==========
-- > -- 11 months | 11 months
-- > -- 1 year | 1 year
-- > -- 1 year and 1 month | 1 year
-- > -- 1 year and 6 months | 1 year
-- > -- 1 year and 7 months | 1 year
-- > -- 1 year and 11 months | 1 year -- still rounds down to 1 year
-- > -- 2 years | 2 years
-- > -- 2 years and 1 month | 2 years
newtype RoundDown a = RoundDown a
instance IntervalToEventTime a => IntervalToEventTime (RoundDown a) where
intervalToEventTime (RoundDown a) =
let orig = intervalToEventTime a
in case orig of
Ago ta -> case ta of
TimeAgo Second n ->
if n < 60
then orig
else Ago $ TimeAgo Minute $ n `div` 60
TimeAgo Minute n ->
if n < 60
then orig
else Ago $ TimeAgo Hour $ n `div` 60
TimeAgo Hour n
| n < 24 -> orig
| n < 24 * 7 -> Ago $ TimeAgo Day $ n `div` 24
| n < 24 * 31 -> Ago $ TimeAgo Week $ n `div` (24 * 7)
| otherwise -> Ago $ TimeAgo Month $ n `div` (24 * 30)
TimeAgo Day n -> Ago $ TimeAgo Year $ n `div` 365
_ -> orig
_ -> orig
-- | Human friendly event time conversion. Renders a time interval rounded to
-- the nearest whole unit. Example:
--
-- > -- Interval | Event time
-- > -- ==================== + ==========
-- > -- 11 months | 11 months
-- > -- 1 year | 1 year
-- > -- 1 year and 1 month | 1 year
-- > -- 1 year and 6 months | 1 year
-- > -- 1 year and 7 months | 2 years -- already rounds up to 2 years
-- > -- 1 year and 11 months | 2 years
-- > -- 2 years | 2 years
-- > -- 2 years and 1 month | 2 years
newtype RoundNear a = RoundNear a
-- | Human friendly event time conversion. Renders a time interval rounded
-- down, but switches unit only when the previous unit reaches 2 (instead
-- of 1). Example:
--
-- > -- Interval | Event time
-- > -- ==================== + ==========
-- > -- 11 months | 11 months
-- > -- 1 year | 12 months
-- > -- 1 year and 1 month | 12 months
-- > -- 1 year and 6 months | 18 months
-- > -- 1 year and 7 months | 19 months
-- > -- 1 year and 11 months | 23 months -- still counts in months
-- > -- 2 years | 2 years
-- > -- 2 years and 1 month | 2 years
-- > -- 2 year and 11 months | 2 year -- still rounds down to 2 years
-- > -- 3 years | 3 years
-- > -- 3 years and 1 month | 3 years
newtype RoundDownWait a = RoundDownWait a
instance IntervalToEventTime a => IntervalToEventTime (RoundDownWait a) where
intervalToEventTime (RoundDownWait a) =
let orig = intervalToEventTime a
in case orig of
Ago ta -> case ta of
TimeAgo Second n ->
if n < 60 * 2
then orig
else Ago $ TimeAgo Minute $ n `div` 60
TimeAgo Minute n ->
if n < 60 * 2
then orig
else Ago $ TimeAgo Hour $ n `div` 60
TimeAgo Hour n
| n < 24 * 2 -> orig
| n < 24 * 14 -> Ago $ TimeAgo Day $ n `div` 24
| n < 24 * 62 -> Ago $ TimeAgo Week $ n `div` (24 * 7)
| otherwise -> Ago $ TimeAgo Month $ n `div` (24 * 30)
TimeAgo Day n ->
if n < 365 * 2
then Ago $ TimeAgo Month $ n `div` 30
else Ago $ TimeAgo Year $ n `div` 365
_ -> orig
_ -> orig
-- | Human friendly event time conversion. Renders a time interval rounded to
-- the nearest whole unit, but switches unit only when the previous unit
-- reaches 2 (instead of 1). Example:
--
-- > -- Interval | Event time
-- > -- ==================== + ==========
-- > -- 11 months | 11 months
-- > -- 1 year | 12 months
-- > -- 1 year and 1 month | 12 months
-- > -- 1 year and 6 months | 18 months
-- > -- 1 year and 7 months | 19 months
-- > -- 1 year and 11 months | 23 months -- still counts in months
-- > -- 2 years | 2 years
-- > -- 2 years and 1 month | 2 years
-- > -- 1 year and 6 months | 2 years
-- > -- 1 year and 7 months | 3 years -- already rounds up to 3 years
-- > -- 2 year and 11 months | 3 year
-- > -- 3 years | 3 years
-- > -- 3 years and 1 month | 3 years
newtype RoundNearWait a = RoundNearWait a
-- | Human friendly event time conversion. This is simply an alias to one of
-- the newtypes above. If you don't have a specific preference, this is a safe
-- defauly.
newtype FriendlyConvert a = FriendlyConvert a
instance IntervalToEventTime a => IntervalToEventTime (FriendlyConvert a) where
intervalToEventTime (FriendlyConvert a) =
intervalToEventTime (RoundDownWait a)
-- | Convert a specification of the current time into event time. This adds two
-- step on top of conversion of an interval (which is what
-- 'IntervalToEventTime' does):
--
-- (1) Get the current time
-- (2) Determine the interval between the event's time and the current time
--
-- There's also a limitation to a specific conversion mode. I need to fix this.
-- Possible solutions:
--
-- * ( ) Add fields or classes for time difference functions and typing a spec
-- type to its difference type
-- * ( ) Turn the adapters into functions of type EventTime -> EventTime
-- * (x) Make EventTime an instance of IntervalToEventTime
class SpecToEventTime s where
specToEventTime :: s -> IO EventTime
specsToEventTimes :: Functor t => t s -> IO (t EventTime)
-------------------------------------------------------------------------------
-- Display
-------------------------------------------------------------------------------
showSingle :: TimeUnit -> Text
showSingle tu =
case tu of
Second -> "second"
Minute -> "minute"
Hour -> "hour"
Day -> "day"
Week -> "week"
Month -> "month"
Year -> "year"
showPlural :: TimeUnit -> Text
showPlural tu = showSingle tu `snoc` 's'
showTimeUnit :: TimeUnit -> Int -> Text
showTimeUnit tu 1 = showSingle tu
showTimeUnit tu _ = showPlural tu
showTimeAgo :: TimeAgo -> Text
showTimeAgo (TimeAgo u n) =
F.sformat (F.int F.% " " F.% F.stext F.% " ago") n (showTimeUnit u n)
showEventTime :: EventTime -> Text
showEventTime Now = "Now"
showEventTime (Ago ta) = showTimeAgo ta
showEventTime Never = "Never"