✨ Add closestToArray and closestToList

__tests__/closestToArray_test.re

@@ -0,0 +1,87 @@
+open Jest;
+
+open Js.Date;
+
+describe("closestToArray", () => {
+  open ExpectJs;
+
+  test(
+    "returns the date from the given array closest to the given date #1", () => {
+    let date = makeWithYMD(~year=2018., ~month=0., ~date=1., ());
+
+    let a = makeWithYMD(~year=1999., ~month=0., ~date=1., ());
+    let b = makeWithYMD(~year=2018., ~month=2., ~date=1., ());
+    let c = makeWithYMD(~year=2020., ~month=4., ~date=1., ());
+    let d = makeWithYMD(~year=2022., ~month=12., ~date=1., ());
+
+    let dates = [|a, b, c, d|];
+
+    date |> ReDate.closestToArray(dates) |> expect |> toEqual(Some(b));
+  });
+
+  test(
+    "returns the date from the given array closest to the given date #2", () => {
+    let date =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=15.,
+        (),
+      );
+
+    let a =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=50.,
+        ~seconds=0.,
+        (),
+      );
+    let b =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=20.,
+        (),
+      );
+    let c =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=19.,
+        (),
+      );
+    let d =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=13.,
+        (),
+      );
+
+    let dates = [|a, b, c, d|];
+
+    date |> ReDate.closestToArray(dates) |> expect |> toEqual(Some(d));
+  });
+
+  test("returns `None` if the given array is empty", () => {
+    let date = makeWithYMD(~year=2018., ~month=0., ~date=2., ());
+    let dates = [||];
+
+    date |> ReDate.closestToArray(dates) |> expect |> toEqual(None);
+  });
+});

__tests__/closestToList_test.re

@@ -0,0 +1,85 @@
+open Jest;
+
+open Js.Date;
+
+describe("closestToList", () => {
+  open ExpectJs;
+
+  test("returns the date from the given list closest to the given date #1", () => {
+    let date = makeWithYMD(~year=2018., ~month=0., ~date=1., ());
+
+    let a = makeWithYMD(~year=1999., ~month=0., ~date=1., ());
+    let b = makeWithYMD(~year=2018., ~month=2., ~date=1., ());
+    let c = makeWithYMD(~year=2020., ~month=4., ~date=1., ());
+    let d = makeWithYMD(~year=2022., ~month=12., ~date=1., ());
+
+    let dates = [a, b, c, d];
+
+    date |> ReDate.closestToList(dates) |> expect |> toEqual(Some(b));
+  });
+
+  test("returns the date from the given list closest to the given date #2", () => {
+    let date =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=15.,
+        (),
+      );
+
+    let a =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=50.,
+        ~seconds=0.,
+        (),
+      );
+    let b =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=20.,
+        (),
+      );
+    let c =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=19.,
+        (),
+      );
+    let d =
+      makeWithYMDHMS(
+        ~year=2019.,
+        ~month=0.,
+        ~date=1.,
+        ~hours=8.,
+        ~minutes=45.,
+        ~seconds=13.,
+        (),
+      );
+
+    let dates = [a, b, c, d];
+
+    date |> ReDate.closestToList(dates) |> expect |> toEqual(Some(d));
+  });
+
+  test("returns `None` if the given list is empty", () => {
+    let date = makeWithYMD(~year=2018., ~month=0., ~date=2., ());
+    let dates = [];
+
+    date |> ReDate.closestToList(dates) |> expect |> toEqual(None);
+  });
+});

src/ReDate.re

@@ -31,6 +31,11 @@ type differenceIn =
   | Years
   | CalendarYears;
 
+type closestTo = {
+  distance: option(float),
+  date: option(Js.Date.t),
+};
+
 module Milliseconds = {
   let second = 1000;
 
@@ -268,6 +273,22 @@ module Internal = {
 
   let lastDayOfMonth = date =>
     date |> makeLastDayOfMonth |> makeDateWithStartOfDayHours;
+
+  let closestTo = (date, acc, dateToCompare) => {
+    let distance =
+      Js.Math.abs_float(
+        (date |> Js.Date.getTime) -. (dateToCompare |> Js.Date.getTime),
+      );
+    let result = {date: Some(dateToCompare), distance: Some(distance)};
+
+    Belt.Option.mapWithDefault(acc.distance, result, minDistance =>
+      distance < minDistance ? result : acc
+    );
+  };
+
+  let defaultClosestToDate = {date: None, distance: None};
+
+  let retrieveClosestToDate = currentDate => currentDate.date;
 };
 
 /* ——[Common helpers]——————————— */
@@ -335,6 +356,18 @@ let endOfSecond = date =>
 let isSameSecond = (fst, snd) =>
   fst |> startOfSecond |> isEqual(snd |> startOfSecond);
 
+let closestToArray = (datesToCompare, date) =>
+  Internal.(
+    Belt.Array.reduce(datesToCompare, defaultClosestToDate, closestTo(date))
+    |> retrieveClosestToDate
+  );
+
+let closestToList = (datesToCompare, date) =>
+  Internal.(
+    Belt.List.reduce(datesToCompare, defaultClosestToDate, closestTo(date))
+    |> retrieveClosestToDate
+  );
+
 /* ——[Minute helpers]——————————— */
 
 let addMinutes = (minutes, date) =>

src/ReDate.rei

@@ -48,6 +48,10 @@ let isValid:
   ) =>
   bool;
 
+let closestToArray: (array(Js.Date.t), Js.Date.t) => option(Js.Date.t);
+
+let closestToList: (list(Js.Date.t), Js.Date.t) => option(Js.Date.t);
+
 /* ——[Second helpers]——————————— */
 
 let addSeconds: (int, Js.Date.t) => Js.Date.t;