typescript(option): feat: added the 'unwrap' helper

Signed-off-by: prescientmoon <git@moonythm.dev>

typescript/option/src/helpers/external.ts

@@ -22,4 +22,5 @@ export * from './or'
 export * from './orLazy'
 export * from './toArray'
 export * from './toNullable'
+export * from './unwrap'
 export * from './withDefault'

typescript/option/src/helpers/unwrap.test.ts

@@ -0,0 +1,37 @@
+import { constantly, identity } from '@thi.ng/compose'
+import { expect } from 'chai'
+import { spy } from 'sinon'
+import { someX, x } from '../../test/constants'
+import { None } from '../types'
+import { unwrap } from './unwrap'
+
+describe('The unwrap helper', () => {
+    it('should return the default when given None', () => {
+        // act
+        const result = unwrap(0, constantly(1), None)
+
+        // assert
+        expect(result).to.equal(0)
+    })
+
+    describe('When given Some', () => {
+        it('should return the result of the mapper ', () => {
+            // act
+            const result = unwrap(0, constantly(1), someX)
+
+            // assert
+            expect(result).to.equal(1)
+        })
+
+        it('should pass the inner value to the mapper', () => {
+            // arrange
+            const mapper = spy(identity)
+
+            // act
+            unwrap(0, mapper, someX)
+
+            // assert
+            expect(mapper.calledWith(x)).to.be.true
+        })
+    })
+})

typescript/option/src/helpers/unwrap.ts

@@ -0,0 +1,20 @@
+import { Mapper } from '../internalTypes'
+import { Option } from '../types'
+import { withDefault } from './withDefault'
+import { map } from './map'
+
+/**
+ * Apply the function to the value in the Maybe and return it unwrapped.
+ * If the Maybe is Nothing, use the default value instead.
+ *
+ * @param _default The default value to use.
+ * @param mapper Function to apply to the inner value.
+ * @param option Option to unwrap.
+ */
+export const unwrap = <T, U>(
+    _default: U,
+    mapper: Mapper<T, U>,
+    option: Option<T>
+) => {
+    return withDefault(_default, map(mapper, option))
+}