feat(skill/date_time): days countdown

skills/utilities/date_time/config/en.json

@@ -23,12 +23,26 @@
         "What is this week's number?",
         "What week of the year are we?"
       ]
+    },
+    "days_countdown": {
+      "type": "logic",
+      "utterance_samples": [
+        "How many days left until 1st July?",
+        "What is the number of days remaining until December 25th?",
+        "In how many days will it be February 10th?"
+      ]
     }
   },
   "answers": {
     "current_date_time": [
       "It is %weekday%, %month% %day%, %year%, and it is %hours%:%minutes%:%seconds%."
     ],
-    "current_week_number": ["It is the %week_number% week of the year."]
+    "current_week_number": ["It is the %week_number% week of the year."],
+    "days_countdown": [
+      "There are %days% days between %month1% %day1%, %year1% and %month2% %day2%, %year2%."
+    ],
+    "days_countdown_error": [
+      "I'm sorry, I didn't understand the date you said."
+    ]
   }
 }

skills/utilities/date_time/src/actions/current_week_number.ts

@@ -3,7 +3,7 @@ import { leon } from '@sdk/leon'
 
 import { format } from 'numerable'
 
-const ONE_DAY_MILLISECONDS = 1_000 * 60 * 60 * 24
+import { ONE_DAY_MILLISECONDS } from '../lib/constants'
 
 /**
  * Get the week number (1-52) for a given date.

skills/utilities/date_time/src/actions/days_countdown.ts

@@ -0,0 +1,60 @@
+import type {
+  ActionFunction,
+  ActionParams,
+  BuiltInDateRangeEntity
+} from '@sdk/types'
+import { leon } from '@sdk/leon'
+
+import { ONE_DAY_MILLISECONDS } from '../lib/constants'
+
+const isBuiltInDateRangeEntity = (
+  entity: ActionParams['current_entities'][number]
+): entity is BuiltInDateRangeEntity => {
+  return entity.entity === 'daterange'
+}
+
+/**
+ * Calculate the number of days between two dates.
+ * @example daysBetween(new Date(2020, 0, 1), new Date(2020, 0, 1)) // 0
+ * @example daysBetween(new Date(2020, 0, 1), new Date(2020, 0, 2)) // 1
+ */
+const daysBetween = (date1: Date, date2: Date): number => {
+  const differenceMilliseconds = Math.abs(date1.getTime() - date2.getTime())
+  return Math.round(differenceMilliseconds / ONE_DAY_MILLISECONDS)
+}
+
+export const run: ActionFunction = async function (params) {
+  const { current_entities } = params
+
+  let futureDateString: string | null = null
+
+  for (const entity of current_entities) {
+    if (isBuiltInDateRangeEntity(entity)) {
+      const { futureEndDate } = entity.resolution
+      futureDateString = futureEndDate
+      break
+    }
+  }
+
+  if (futureDateString == null) {
+    return await leon.answer({
+      key: 'days_countdown_error'
+    })
+  }
+
+  const currentDate = new Date()
+  const futureDate = new Date(futureDateString)
+  const daysCountdown = daysBetween(currentDate, futureDate)
+  await leon.answer({
+    key: 'days_countdown',
+    data: {
+      days: daysCountdown,
+      month1: currentDate.toLocaleString(params.lang, { month: 'long' }),
+      day1: currentDate.getDate(),
+      year1: currentDate.getFullYear(),
+      month2: futureDate.toLocaleString(params.lang, { month: 'long' }),
+      day2: futureDate.getDate(),
+      year2: futureDate.getFullYear()
+    }
+  })
+}

skills/utilities/date_time/src/lib/constants.ts

@@ -0,0 +1 @@
+export const ONE_DAY_MILLISECONDS = 1_000 * 60 * 60 * 24