Add 'Burger Discounts' chapter

docs/.vitepress/config.js

@@ -37,6 +37,7 @@ export default defineConfig({
           { text: 'Better Burgers', link: '/better-burgers/' },
           { text: 'Sandwich Tests', link: '/sandwich-tests/' },
           { text: 'Cram Tests', link: '/cram-tests/' },
+          { text: 'Burger Discounts', link: '/burger-discounts/' },
         ]
       }
     ],

docs/burger-discounts/Discount.re

@@ -0,0 +1,252 @@
+let _ =
+  (items: array(Item.t)) => {
+    let burgers =
+      items
+      // #region type-annotate-argument
+      |> Js.Array.filter(~f=(item: Item.t) =>
+           switch (item) {
+           | Burger(_) => true
+           | Sandwich(_)
+           | Hotdog => false
+           }
+         );
+    // #endregion type-annotate-argument
+    ignore(burgers);
+  };
+
+let _ =
+  (items: array(Item.t)) => {
+    let burgers =
+      items
+      // #region full-name-constructors
+      |> Js.Array.filter(~f=item =>
+           switch (item) {
+           | Item.Burger(_) => true
+           | Item.Sandwich(_)
+           | Item.Hotdog => false
+           }
+         );
+    // #endregion full-name-constructors
+    ignore(burgers);
+  };
+
+let _ =
+  (items: array(Item.t)) => {
+    let burgers =
+      items
+      // #region full-name-constructor
+      |> Js.Array.filter(~f=item =>
+           switch (item) {
+           | Item.Burger(_) => true
+           | Sandwich(_)
+           | Hotdog => false
+           }
+         );
+    // #endregion full-name-constructor
+    ignore(burgers);
+  };
+
+let _ =
+  (items: array(Item.t)) => {
+    let burgers =
+      items
+      // #region full-name-fun
+      |> Js.Array.filter(
+           ~f=
+             fun
+             | Item.Burger(_) => true
+             | Sandwich(_)
+             | Hotdog => false,
+         );
+    // #endregion full-name-fun
+    ignore(burgers);
+  };
+
+let _ =
+  (items: array(Item.t)) => {
+    // #region swap-function-order
+    items
+    |> Js.Array.filter(~f=item =>
+         switch (item) {
+         | Item.Burger(_) => true
+         | Sandwich(_)
+         | Hotdog => false
+         }
+       )
+    |> Js.Array.sortInPlaceWith(~f=(item1, item2) =>
+         - compare(Item.toPrice(item1), Item.toPrice(item2))
+       )
+    // #endregion swap-function-order
+    |> ignore;
+  };
+
+let _ = {
+  let burgers: array(Item.t) = [||];
+
+  // #region match-on-tuple
+  switch (burgers[0], burgers[1]) {
+  | (Burger(_), Burger(cheaperBurger)) =>
+    Some(Item.Burger.toPrice(cheaperBurger))
+  | _ => None
+  };
+  // #endregion match-on-tuple
+};
+
+let _ = {
+  let burgers: array(Item.t) = [||];
+
+  // #region check-array-length
+  Js.Array.length(burgers) < 2
+    ? None
+    : (
+      switch (burgers[0], burgers[1]) {
+      | (Burger(_), Burger(cheaperBurger)) =>
+        Some(Item.Burger.toPrice(cheaperBurger))
+      | _ => None
+      }
+    );
+  // #endregion check-array-length
+};
+
+let _ = {
+  let burgers: array(Item.t) = [||];
+
+  // #region catch-exception
+  switch (burgers[0], burgers[1]) {
+  | exception _ => None
+  | (Burger(_), Burger(cheaperBurger)) =>
+    Some(Item.Burger.toPrice(cheaperBurger))
+  | _ => None
+  };
+  // #endregion catch-exception
+};
+
+module Array = {
+  // #region module-array
+  // Safe array access function
+  let get: (array('a), int) => option('a) =
+    (array, index) =>
+      switch (index) {
+      | index when index < 0 || index >= Js.Array.length(array) => None
+      | index => Some(Stdlib.Array.get(array, index))
+      };
+  // #endregion module-array
+};
+
+let _ = {
+  let burgers: array(Item.t) = [||];
+
+  // #region custom-array-get
+  switch (burgers[0], burgers[1]) {
+  | (Some(Burger(_)), Some(Burger(cheaperBurger))) =>
+    Some(Item.Burger.toPrice(cheaperBurger))
+  | _ => None
+  };
+  // #endregion custom-array-get
+};
+
+// #region improved-get-free-burger
+// Buy 2 burgers, get 1 free
+let getFreeBurger = (items: array(Item.t)) => {
+  let burgers =
+    items
+    |> Js.Array.filter(~f=item =>
+         switch (item) {
+         | Item.Burger(_) => true
+         | Sandwich(_)
+         | Hotdog => false
+         }
+       )
+    |> Js.Array.map(~f=Item.toPrice)
+    |> Js.Array.sortInPlaceWith(~f=(x, y) => - compare(x, y));
+
+  switch (burgers[0], burgers[1]) {
+  | (Some(_), Some(cheaperPrice)) => Some(cheaperPrice)
+  | (None | Some(_), None | Some(_)) => None
+  };
+};
+// #endregion improved-get-free-burger
+
+// #region get-half-off-one
+// Buy 1+ burger with 1 of every topping, get half off
+let getHalfOff = (items: array(Item.t)) => {
+  let meetsCondition =
+    items
+    |> Js.Array.some(
+         ~f=
+           fun
+           | Item.Burger({
+               lettuce: true,
+               tomatoes: true,
+               onions: 1,
+               cheese: 1,
+               bacon: 1,
+             }) =>
+             true
+           | Burger(_)
+           | Sandwich(_)
+           | Hotdog => false,
+       );
+
+  switch (meetsCondition) {
+  | false => None
+  | true =>
+    let total =
+      items
+      |> Js.Array.reduce(~init=0.0, ~f=(total, item) =>
+           total +. Item.toPrice(item)
+         );
+    Some(total /. 2.0);
+  };
+};
+// #endregion get-half-off-one
+ignore(getHalfOff);
+
+// #region get-half-off
+// Buy 1+ burger with 1+ of every topping, get half off
+let getHalfOff = (items: array(Item.t)) => {
+  let meetsCondition =
+    items
+    |> Js.Array.some(
+         ~f=
+           fun
+           | Item.Burger({
+               lettuce: true,
+               tomatoes: true,
+               onions,
+               cheese,
+               bacon,
+             })
+               when onions > 0 && cheese > 0 && bacon > 0 =>
+             true
+           | Burger(_)
+           | Sandwich(_)
+           | Hotdog => false,
+       );
+
+  switch (meetsCondition) {
+  | false => None
+  | true =>
+    let total =
+      items
+      |> Js.Array.reduce(~init=0.0, ~f=(total, item) =>
+           total +. Item.toPrice(item)
+         );
+    Some(total /. 2.0);
+  };
+};
+// #endregion get-half-off
+
+let _ =
+  name => {
+    // #region return-variant-at-end
+    let result =
+      name
+      |> String.split_on_char(' ')
+      |> List.map(String.map(c => c |> Char.code |> (+)(1) |> Char.chr))
+      |> String.concat(" ")
+      |> String.cat("Hello, ");
+
+    Some(result);
+    // #endregion return-variant-at-end
+  };

docs/burger-discounts/DiscountTests.re

@@ -0,0 +1,122 @@
+// #region first-three
+open Fest;
+
+test("0 burgers, no discount", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Hotdog,
+         Sandwich(Ham),
+         Sandwich(Turducken),
+       |]),
+       None,
+     )
+);
+
+test("1 burger, no discount", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Hotdog,
+         Sandwich(Ham),
+         Burger({
+           lettuce: false,
+           onions: 0,
+           cheese: 0,
+           tomatoes: false,
+           bacon: 0,
+         }),
+       |]),
+       None,
+     )
+);
+
+test("2 burgers of same price, discount", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Hotdog,
+         Burger({
+           lettuce: false,
+           onions: 0,
+           cheese: 0,
+           tomatoes: false,
+           bacon: 0,
+         }),
+         Sandwich(Ham),
+         Burger({
+           lettuce: false,
+           onions: 0,
+           cheese: 0,
+           tomatoes: false,
+           bacon: 0,
+         }),
+       |]),
+       Some(15.),
+     )
+);
+// #endregion first-three
+
+// #region burger-record
+let burger: Item.Burger.t = {
+  lettuce: false,
+  onions: 0,
+  cheese: 0,
+  tomatoes: false,
+  bacon: 0,
+};
+// #endregion burger-record
+
+// #region refactor-use-burger-record
+test("1 burger, no discount", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|Hotdog, Sandwich(Ham), Burger(burger)|]),
+       None,
+     )
+);
+
+test("2 burgers of same price, discount", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Hotdog,
+         Burger(burger),
+         Sandwich(Ham),
+         Burger(burger),
+       |]),
+       Some(15.),
+     )
+);
+// #endregion refactor-use-burger-record
+
+// #region different-price-test
+test("2 burgers of different price, discount of cheaper one", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Hotdog,
+         Burger({...burger, tomatoes: true}), // 15.05
+         Sandwich(Ham),
+         Burger({...burger, bacon: 2}) // 16.00
+       |]),
+       Some(15.05),
+     )
+);
+// #endregion different-price-test
+
+// #region three-burgers
+test("3 burgers of different price, return Some(15.15)", () =>
+  expect
+  |> equal(
+       Discount.getFreeBurger([|
+         Burger(burger), // 15
+         Hotdog,
+         Burger({...burger, tomatoes: true, cheese: 1}), // 15.15
+         Sandwich(Ham),
+         Burger({...burger, bacon: 2}) // 16.00
+       |]),
+       Some(15.15),
+     )
+);
+// #endregion three-burgers