Make Interval API take seasons

See #12

src/interval.js

@@ -3,7 +3,7 @@
 const assert = require('assert')
 const ExtDate = require('./date')
 const ExtDateTime = require('./interface')
-
+const Season = require('./season')
 const V = new WeakMap()
 
 
@@ -68,7 +68,7 @@ class Interval extends ExtDateTime {
     if (value === Infinity || value === -Infinity)
       return this.values[1] = Infinity
 
-    value = ExtDate.from(value)
+    value = getDateOrSeasonFrom(value)
 
     if (value >= this.upper && this.upper != null)
       throw new RangeError(`invalid lower bound: ${value}`)
@@ -87,7 +87,7 @@ class Interval extends ExtDateTime {
     if (value === Infinity)
       return this.values[1] = Infinity
 
-    value = ExtDate.from(value)
+    value = getDateOrSeasonFrom(value)
 
     if (value <= this.lower)
       throw new RangeError(`invalid upper bound: ${value}`)
@@ -130,4 +130,12 @@ class Interval extends ExtDateTime {
   }
 }
 
+function getDateOrSeasonFrom(value) {
+  try {
+    return ExtDate.from(value)
+  } catch (de) {
+    return Season.from(value)
+  }
+}
+
 module.exports = Interval

test/interval.js

@@ -1,6 +1,6 @@
 'use strict'
 
-const { Interval, Date } = require('..')
+const { Interval, Date, Season } = require('..')
 
 describe('Interval', () => {
 
@@ -62,4 +62,21 @@ describe('Interval', () => {
     it('default', () =>
       expect(new Interval().edtf).to.eql('/'))
   })
+
+  describe('seasons (non-standard)', () => {
+    const S80 = new Interval('1980-21', '1980-24')
+
+    it('.lower', () => {
+      expect(S80.lower).to.be.instanceof(Season)
+    })
+
+    it('.edtf', () => {
+      expect(S80.toEDTF()).to.be.eql('1980-21/1980-24')
+    })
+
+    //it('includes', () => {
+    //  expect(S80.includes(new Date(1980, 8))).to.be.true
+    //  expect(S80.includes(new Season(1980, 22))).to.be.true
+    //})
+  })
 })