From 0556f2694a1a8ab24f6640e33c2d510ad48e3b10 Mon Sep 17 00:00:00 2001
From: shayan javani <25373436+massivefermion@users.noreply.github.com>
Date: Wed, 11 Oct 2023 07:46:39 +0330
Subject: [PATCH] added the book-store exercise

---
 config.json                                   | 150 +++++++----------
 .../practice/book-store/.docs/instructions.md |  61 +++++++
 exercises/practice/book-store/.gitignore      |   4 +
 .../practice/book-store/.meta/config.json     |  23 +++
 .../practice/book-store/.meta/example.gleam   |  40 +++++
 .../practice/book-store/.meta/tests.toml      |  64 ++++++++
 exercises/practice/book-store/gleam.toml      |  11 ++
 exercises/practice/book-store/manifest.toml   |  25 +++
 .../practice/book-store/src/book_store.gleam  |   3 +
 .../book-store/test/book_store_test.gleam     | 151 ++++++++++++++++++
 10 files changed, 438 insertions(+), 94 deletions(-)
 create mode 100644 exercises/practice/book-store/.docs/instructions.md
 create mode 100644 exercises/practice/book-store/.gitignore
 create mode 100644 exercises/practice/book-store/.meta/config.json
 create mode 100644 exercises/practice/book-store/.meta/example.gleam
 create mode 100644 exercises/practice/book-store/.meta/tests.toml
 create mode 100644 exercises/practice/book-store/gleam.toml
 create mode 100644 exercises/practice/book-store/manifest.toml
 create mode 100644 exercises/practice/book-store/src/book_store.gleam
 create mode 100644 exercises/practice/book-store/test/book_store_test.gleam

diff --git a/config.json b/config.json
index 0c6833a89..0b8d57459 100644
--- a/config.json
+++ b/config.json
@@ -16,7 +16,7 @@
     "highlightjs_language": "gleam"
   },
   "test_runner": {
-    "average_run_time": 3
+    "average_run_time": 3.0
   },
   "files": {
     "solution": [
@@ -560,8 +560,7 @@
         "name": "Forth",
         "uuid": "8176ac78-d4fd-475f-ac8b-e205ca7b3a77",
         "difficulty": 9,
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "strings",
@@ -645,8 +644,7 @@
         "slug": "protein-translation",
         "name": "Protein Translation",
         "uuid": "612395a5-238e-4be0-8ce0-4ac66f57056e",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1012,8 +1010,7 @@
         "slug": "alphametics",
         "name": "Alphametics",
         "uuid": "5aef7d9d-3939-4014-8102-a7262fdde754",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "sets",
@@ -1062,8 +1059,7 @@
         "slug": "acronym",
         "name": "Acronym",
         "uuid": "21946b94-c304-4a10-a6b6-b9fd5bbe9966",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "labelled-arguments",
           "regular-expressions",
@@ -1204,8 +1200,7 @@
         "slug": "prime-factors",
         "name": "Prime Factors",
         "uuid": "00d1a428-99c4-4175-bee2-e05fc034528f",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "lists",
@@ -1218,8 +1213,7 @@
         "slug": "run-length-encoding",
         "name": "Run-Length Encoding",
         "uuid": "22298714-cc36-49b7-8e70-cfb91ff42112",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "strings",
@@ -1233,8 +1227,7 @@
         "slug": "grains",
         "name": "Grains",
         "uuid": "b5b9be18-9141-4176-8f8c-3dd14d14bed5",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "case-expressions",
@@ -1247,8 +1240,7 @@
         "slug": "nucleotide-count",
         "name": "Nucleotide count",
         "uuid": "3b7e1bbf-08b2-4e0e-ba5d-5a887deb4817",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "results",
@@ -1262,8 +1254,7 @@
         "slug": "hamming",
         "name": "Hamming",
         "uuid": "64a40995-c380-4233-a7af-98498dbc5c2d",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "strings",
@@ -1277,8 +1268,7 @@
         "slug": "proverb",
         "name": "Proverb",
         "uuid": "d2288ce0-3ef4-4a79-8e21-bf5624b5ab27",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "strings",
@@ -1290,8 +1280,7 @@
         "slug": "high-scores",
         "name": "High Scores",
         "uuid": "af720091-1352-4e07-96d2-0868588601f2",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "ints",
@@ -1303,8 +1292,7 @@
         "slug": "allergies",
         "name": "Allergies",
         "uuid": "f829a1af-0eaf-4880-b1d8-cd2cb3753fb0",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "lists",
@@ -1318,8 +1306,7 @@
         "name": "Twelve Days",
         "uuid": "583b74dc-2c5c-48f8-85c2-c90623507682",
         "difficulty": 3,
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1331,8 +1318,7 @@
         "slug": "etl",
         "name": "ETL",
         "uuid": "1655d9f6-6199-4462-85bd-a5da5f25d30a",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "maps",
           "lists",
@@ -1345,8 +1331,7 @@
         "slug": "queen-attack",
         "name": "Queen Attack",
         "uuid": "9caa195e-2273-4096-9aee-26ab5658e7f7",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "custom-types",
           "case-expressions",
@@ -1359,8 +1344,7 @@
         "slug": "sublist",
         "name": "Sublist",
         "uuid": "6d4933cc-0845-4992-93ee-54f79a79fc5a",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "case-expressions",
@@ -1374,8 +1358,7 @@
         "slug": "rotational-cipher",
         "name": "Rotational Cipher",
         "uuid": "2e7fdb4d-3e75-4dc2-9fb7-ee1a9e1950f9",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "ints",
@@ -1387,8 +1370,7 @@
         "slug": "change",
         "name": "Change",
         "uuid": "8dc8aceb-fe74-415c-bf4b-956840155272",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "results",
@@ -1401,8 +1383,7 @@
         "slug": "flatten-array",
         "name": "Flatten Array",
         "uuid": "efdf70a3-57e6-474a-9fc2-09f26bb609b6",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "custom-types",
@@ -1415,8 +1396,7 @@
         "slug": "all-your-base",
         "name": "All Your Base",
         "uuid": "e9332e6f-a7e5-4f30-825c-64af0a278a70",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "lists",
@@ -1430,8 +1410,7 @@
         "slug": "knapsack",
         "name": "Knapsack",
         "uuid": "6e889724-656e-4f0c-aba1-08f103490e9d",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "custom-types",
@@ -1460,8 +1439,7 @@
         "slug": "dnd-character",
         "name": "D&D Character",
         "uuid": "65d80b55-02f0-4d40-a530-79843553252f",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "custom-types",
@@ -1473,8 +1451,7 @@
         "slug": "isbn-verifier",
         "name": "ISBN Verifier",
         "uuid": "d12ac283-8ca4-4b40-919a-9588e1e52d50",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "ints",
@@ -1504,8 +1481,7 @@
         "slug": "atbash-cipher",
         "name": "Atbash Cipher",
         "uuid": "3c850415-92fa-4019-b776-aaab30675680",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1518,8 +1494,7 @@
         "slug": "square-root",
         "name": "Square Root",
         "uuid": "700f44e5-13a3-4e97-aad5-d383e25f9f9b",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "bools",
@@ -1547,8 +1522,7 @@
         "slug": "simple-cipher",
         "name": "Simple Cipher",
         "uuid": "37dd415b-1d67-434d-8705-19295d1438b8",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "iterators",
           "strings",
@@ -1562,8 +1536,7 @@
         "slug": "crypto-square",
         "name": "Crypto Square",
         "uuid": "5bf01e81-b30a-4210-b1ed-1edbf3d28ab1",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "lists",
@@ -1576,8 +1549,7 @@
         "slug": "affine-cipher",
         "name": "Affine Cipher",
         "uuid": "594b6c1a-0a4c-4463-9535-62056c71404e",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1593,8 +1565,7 @@
         "slug": "house",
         "name": "House",
         "uuid": "21421905-a33c-4040-9f09-78726b5d1167",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1607,8 +1578,7 @@
         "slug": "connect",
         "name": "Connect",
         "uuid": "89c6bf7a-5cd8-4254-b3e0-1457a5390b46",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "maps",
@@ -1624,8 +1594,7 @@
         "slug": "clock",
         "name": "Clock",
         "uuid": "ad9cc1bd-d99b-4f43-941c-8e09b43801af",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "strings",
@@ -1638,8 +1607,7 @@
         "slug": "killer-sudoku-helper",
         "name": "Killer Sudoku Helper",
         "uuid": "4c6ed017-a02b-4826-a111-ef9733b7d315",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "ints",
@@ -1651,8 +1619,7 @@
         "slug": "luhn",
         "name": "Luhn",
         "uuid": "a66bbefd-db5a-44d0-ab4b-73d871756f08",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1667,8 +1634,7 @@
         "slug": "wordy",
         "name": "Wordy",
         "uuid": "5031033b-bd21-4563-ae18-59ad02f4c489",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "results",
           "strings",
@@ -1684,8 +1650,7 @@
         "slug": "largest-series-product",
         "name": "Largest Series Product",
         "uuid": "34293b12-1d94-43d9-a9cb-27b8bff92d67",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "case-expressions",
           "ints",
@@ -1698,8 +1663,7 @@
         "slug": "minesweeper",
         "name": "Minesweeper",
         "uuid": "abbeeb8f-6ec1-4f57-86fc-2e18b3a62e29",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1713,8 +1677,7 @@
         "slug": "say",
         "name": "Say",
         "uuid": "753fff04-5a64-4c3f-afd2-beee7e27efe8",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "case-expressions",
@@ -1728,8 +1691,7 @@
         "slug": "saddle-points",
         "name": "Saddle Points",
         "uuid": "e1103441-9391-4760-829b-1ec412762fab",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "custom-types",
           "lists",
@@ -1742,18 +1704,15 @@
         "slug": "secret-handshake",
         "name": "Secret Handshake",
         "uuid": "22461f35-684d-4f75-9399-d07a4f483bdd",
-        "practices": [
-        ],
-        "prerequisites": [
-        ],
+        "practices": [],
+        "prerequisites": [],
         "difficulty": 2
       },
       {
         "slug": "matrix",
         "name": "Matrix",
         "uuid": "6fc59193-bc31-40af-902a-b13ad926bbb3",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "lists",
           "strings",
@@ -1766,8 +1725,7 @@
         "slug": "grade-school",
         "name": "Grade School",
         "uuid": "836dddea-2a02-434f-a886-c8e1c429268f",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "maps",
           "results",
@@ -1783,8 +1741,7 @@
         "slug": "variable-length-quantity",
         "name": "Variable Length Quantity",
         "uuid": "f7e33664-ea30-4885-8961-4aa984a1341d",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "bit-strings",
           "case-expressions",
@@ -1798,8 +1755,7 @@
         "slug": "ocr-numbers",
         "name": "OCR Numbers",
         "uuid": "0ac6ba02-b2c0-4c81-8ca0-31c49a340e23",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "lists",
@@ -1813,8 +1769,7 @@
         "slug": "pig-latin",
         "name": "Pig Latin",
         "uuid": "dbc455de-1845-49f9-b5b5-082350e12811",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "strings",
           "case-expressions",
@@ -1826,14 +1781,21 @@
         "slug": "nth-prime",
         "name": "Nth Prime",
         "uuid": "fda0001e-51b5-4041-a08a-2cb7dfef0f1c",
-        "practices": [
-        ],
+        "practices": [],
         "prerequisites": [
           "ints",
           "iterators",
           "recursion"
         ],
         "difficulty": 3
+      },
+      {
+        "slug": "book-store",
+        "name": "TODO",
+        "uuid": "c251e29f-de8a-4e98-b005-f600fe3ae4f9",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
       }
     ]
   },
@@ -2068,4 +2030,4 @@
     "used_for/scripts",
     "used_for/web_development"
   ]
-}
+}
\ No newline at end of file
diff --git a/exercises/practice/book-store/.docs/instructions.md b/exercises/practice/book-store/.docs/instructions.md
new file mode 100644
index 000000000..54403f17b
--- /dev/null
+++ b/exercises/practice/book-store/.docs/instructions.md
@@ -0,0 +1,61 @@
+# Instructions
+
+To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts on multiple book purchases.
+
+One copy of any of the five books costs $8.
+
+If, however, you buy two different books, you get a 5% discount on those two books.
+
+If you buy 3 different books, you get a 10% discount.
+
+If you buy 4 different books, you get a 20% discount.
+
+If you buy all 5, you get a 25% discount.
+
+Note that if you buy four books, of which 3 are different titles, you get a 10% discount on the 3 that form part of a set, but the fourth book still costs $8.
+
+Your mission is to write code to calculate the price of any conceivable shopping basket (containing only books of the same series), giving as big a discount as possible.
+
+For example, how much does this basket of books cost?
+
+- 2 copies of the first book
+- 2 copies of the second book
+- 2 copies of the third book
+- 1 copy of the fourth book
+- 1 copy of the fifth book
+
+One way of grouping these 8 books is:
+
+- 1 group of 5 (1st, 2nd,3rd, 4th, 5th)
+- 1 group of 3 (1st, 2nd, 3rd)
+
+This would give a total of:
+
+- 5 books at a 25% discount
+- 3 books at a 10% discount
+
+Resulting in:
+
+- 5 × (100% - 25%) × $8 = 5 × $6.00 = $30.00, plus
+- 3 × (100% - 10%) × $8 = 3 × $7.20 = $21.60
+
+Which equals $51.60.
+
+However, a different way to group these 8 books is:
+
+- 1 group of 4 books (1st, 2nd, 3rd, 4th)
+- 1 group of 4 books (1st, 2nd, 3rd, 5th)
+
+This would give a total of:
+
+- 4 books at a 20% discount
+- 4 books at a 20% discount
+
+Resulting in:
+
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60, plus
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60
+
+Which equals $51.20.
+
+And $51.20 is the price with the biggest discount.
diff --git a/exercises/practice/book-store/.gitignore b/exercises/practice/book-store/.gitignore
new file mode 100644
index 000000000..170cca981
--- /dev/null
+++ b/exercises/practice/book-store/.gitignore
@@ -0,0 +1,4 @@
+*.beam
+*.ez
+build
+erl_crash.dump
diff --git a/exercises/practice/book-store/.meta/config.json b/exercises/practice/book-store/.meta/config.json
new file mode 100644
index 000000000..4c5cff5ec
--- /dev/null
+++ b/exercises/practice/book-store/.meta/config.json
@@ -0,0 +1,23 @@
+{
+  "authors": [
+    "massivefermion"
+  ],
+  "files": {
+    "solution": [
+      "src/book_store.gleam"
+    ],
+    "test": [
+      "test/book_store_test.gleam"
+    ],
+    "example": [
+      ".meta/example.gleam"
+    ],
+    "invalidator": [
+      "gleam.toml",
+      "manifest.toml"
+    ]
+  },
+  "blurb": "To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.",
+  "source": "Inspired by the harry potter kata from Cyber-Dojo.",
+  "source_url": "https://cyber-dojo.org"
+}
diff --git a/exercises/practice/book-store/.meta/example.gleam b/exercises/practice/book-store/.meta/example.gleam
new file mode 100644
index 000000000..af83f7715
--- /dev/null
+++ b/exercises/practice/book-store/.meta/example.gleam
@@ -0,0 +1,40 @@
+import gleam/int
+import gleam/list
+import gleam/float
+
+pub fn lowest_price(books: List(Int)) -> Float {
+  books
+  |> list.fold(
+    [#(1, 0), #(2, 0), #(3, 0), #(4, 0), #(5, 0)],
+    fn(acc, book) {
+      let assert Ok(current) = list.key_find(acc, book)
+      list.key_set(acc, book, current + 1)
+    },
+  )
+  |> list.map(fn(item) { item.1 })
+  |> list.sort(int.compare)
+  |> calculate(0.0)
+}
+
+fn calculate(counts: List(Int), acc: Float) -> Float {
+  case counts {
+    [0, 0, 0, 0, a] -> acc +. int.to_float(a) *. 800.0
+
+    [0, 0, 0, a, b] -> calculate([0, 0, 0, a - 1, b - 1], acc +. 2.0 *. 760.0)
+
+    [0, 0, a, b, c] ->
+      calculate([0, 0, a - 1, b - 1, c - 1], acc +. 3.0 *. 720.0)
+
+    [0, a, b, c, d] ->
+      calculate([0, a - 1, b - 1, c - 1, d - 1], acc +. 4.0 *. 640.0)
+
+    [a, b, c, d, e] ->
+      float.min(
+        calculate([a - 1, b - 1, c - 1, d - 1, e - 1], acc +. 5.0 *. 600.0),
+        calculate(
+          list.sort([a, b - 1, c - 1, d - 1, e - 1], int.compare),
+          acc +. 4.0 *. 640.0,
+        ),
+      )
+  }
+}
diff --git a/exercises/practice/book-store/.meta/tests.toml b/exercises/practice/book-store/.meta/tests.toml
new file mode 100644
index 000000000..4b7ce98be
--- /dev/null
+++ b/exercises/practice/book-store/.meta/tests.toml
@@ -0,0 +1,64 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[17146bd5-2e80-4557-ab4c-05632b6b0d01]
+description = "Only a single book"
+
+[cc2de9ac-ff2a-4efd-b7c7-bfe0f43271ce]
+description = "Two of the same book"
+
+[5a86eac0-45d2-46aa-bbf0-266b94393a1a]
+description = "Empty basket"
+
+[158bd19a-3db4-4468-ae85-e0638a688990]
+description = "Two different books"
+
+[f3833f6b-9332-4a1f-ad98-6c3f8e30e163]
+description = "Three different books"
+
+[1951a1db-2fb6-4cd1-a69a-f691b6dd30a2]
+description = "Four different books"
+
+[d70f6682-3019-4c3f-aede-83c6a8c647a3]
+description = "Five different books"
+
+[78cacb57-911a-45f1-be52-2a5bd428c634]
+description = "Two groups of four is cheaper than group of five plus group of three"
+
+[f808b5a4-e01f-4c0d-881f-f7b90d9739da]
+description = "Two groups of four is cheaper than groups of five and three"
+
+[fe96401c-5268-4be2-9d9e-19b76478007c]
+description = "Group of four plus group of two is cheaper than two groups of three"
+
+[68ea9b78-10ad-420e-a766-836a501d3633]
+description = "Two each of first four books and one copy each of rest"
+
+[c0a779d5-a40c-47ae-9828-a340e936b866]
+description = "Two copies of each book"
+
+[18fd86fe-08f1-4b68-969b-392b8af20513]
+description = "Three copies of first book and two each of remaining"
+
+[0b19a24d-e4cf-4ec8-9db2-8899a41af0da]
+description = "Three each of first two books and two each of remaining books"
+
+[bb376344-4fb2-49ab-ab85-e38d8354a58d]
+description = "Four groups of four are cheaper than two groups each of five and three"
+
+[5260ddde-2703-4915-b45a-e54dbbac4303]
+description = "Check that groups of four are created properly even when there are more groups of three than groups of five"
+
+[b0478278-c551-4747-b0fc-7e0be3158b1f]
+description = "One group of one and four is cheaper than one group of two and three"
+
+[cf868453-6484-4ae1-9dfc-f8ee85bbde01]
+description = "One group of one and two plus three groups of four is cheaper than one group of each size"
diff --git a/exercises/practice/book-store/gleam.toml b/exercises/practice/book-store/gleam.toml
new file mode 100644
index 000000000..dc13bdb0c
--- /dev/null
+++ b/exercises/practice/book-store/gleam.toml
@@ -0,0 +1,11 @@
+name = "book_store"
+version = "0.1.0"
+
+[dependencies]
+gleam_bitwise = "~> 1.3"
+gleam_otp = "~> 0.7"
+gleam_stdlib = "~> 0.31"
+simplifile = "~> 0.1"
+
+[dev-dependencies]
+exercism_test_runner = "~> 1.4"
diff --git a/exercises/practice/book-store/manifest.toml b/exercises/practice/book-store/manifest.toml
new file mode 100644
index 000000000..6000d0db9
--- /dev/null
+++ b/exercises/practice/book-store/manifest.toml
@@ -0,0 +1,25 @@
+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "exercism_test_runner", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_community_ansi", "simplifile", "gleam_erlang", "gleam_json", "gap", "glance", "gleam_stdlib"], otp_app = "exercism_test_runner", source = "hex", outer_checksum = "336FBF790841C2DC25EB77B35E76A09EFDB9771D7D813E0FDBC71A50CB79711D" },
+  { name = "gap", version = "0.7.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "gleam_community_ansi"], otp_app = "gap", source = "hex", outer_checksum = "AF290C27B3FAE5FE64E1B7E9C70A9E29AA0F42429C0592D375770C1C51B79D36" },
+  { name = "glance", version = "0.7.1", build_tools = ["gleam"], requirements = ["gleam_stdlib", "glexer"], otp_app = "glance", source = "hex", outer_checksum = "B646A08970990D9D7A103443C5CD46F9D4297BF05F188767777FCC14ADF395EA" },
+  { name = "gleam_bitwise", version = "1.3.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_bitwise", source = "hex", outer_checksum = "E2A46EE42E5E9110DAD67E0F71E7358CBE54D5EC22C526DD48CBBA3223025792" },
+  { name = "gleam_community_ansi", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_bitwise", "gleam_community_colour", "gleam_stdlib"], otp_app = "gleam_community_ansi", source = "hex", outer_checksum = "6E4E0CF2B207C1A7FCD3C21AA43514D67BC7004F21F82045CDCCE6C727A14862" },
+  { name = "gleam_community_colour", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "gleam_bitwise"], otp_app = "gleam_community_colour", source = "hex", outer_checksum = "D27CE357ECB343929A8CEC3FBA0B499943A47F0EE1F589EE16AFC2DC21C61E5B" },
+  { name = "gleam_erlang", version = "0.22.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "367D8B41A7A86809928ED1E7E55BFD0D46D7C4CF473440190F324AFA347109B4" },
+  { name = "gleam_json", version = "0.6.0", build_tools = ["gleam"], requirements = ["thoas", "gleam_stdlib"], otp_app = "gleam_json", source = "hex", outer_checksum = "C6CC5BEECA525117E97D0905013AB3F8836537455645DDDD10FE31A511B195EF" },
+  { name = "gleam_otp", version = "0.7.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "gleam_erlang"], otp_app = "gleam_otp", source = "hex", outer_checksum = "ED7381E90636E18F5697FD7956EECCA635A3B65538DC2BE2D91A38E61DCE8903" },
+  { name = "gleam_stdlib", version = "0.31.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "6D1BC5B4D4179B9FEE866B1E69FE180AC2CE485AD90047C0B32B2CA984052736" },
+  { name = "glexer", version = "0.6.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "glexer", source = "hex", outer_checksum = "703D2347F5180B2BCEA4D258549B0D91DACD0905010892BAC46D04D913B84D1F" },
+  { name = "simplifile", version = "0.1.14", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "10EA0207796F20488A3A166C50A189C9385333F3C9FAC187729DE7B9CE4ADDBC" },
+  { name = "thoas", version = "0.4.1", build_tools = ["rebar3"], requirements = [], otp_app = "thoas", source = "hex", outer_checksum = "4918D50026C073C4AB1388437132C77A6F6F7C8AC43C60C13758CC0ADCE2134E" },
+]
+
+[requirements]
+exercism_test_runner = { version = "~> 1.4" }
+gleam_bitwise = { version = "~> 1.3" }
+gleam_otp = { version = "~> 0.7" }
+gleam_stdlib = { version = "~> 0.31" }
+simplifile = { version = "~> 0.1" }
diff --git a/exercises/practice/book-store/src/book_store.gleam b/exercises/practice/book-store/src/book_store.gleam
new file mode 100644
index 000000000..d3198f19d
--- /dev/null
+++ b/exercises/practice/book-store/src/book_store.gleam
@@ -0,0 +1,3 @@
+pub fn lowest_price(basket: List(Int)) {
+  todo
+}
diff --git a/exercises/practice/book-store/test/book_store_test.gleam b/exercises/practice/book-store/test/book_store_test.gleam
new file mode 100644
index 000000000..cb1c329f3
--- /dev/null
+++ b/exercises/practice/book-store/test/book_store_test.gleam
@@ -0,0 +1,151 @@
+import exercism/test_runner
+import exercism/should
+import book_store
+
+pub fn main() {
+  test_runner.main()
+}
+
+pub fn only_a_single_book_test() {
+  let input = [1]
+  let output = book_store.lowest_price(input)
+  let expected = 800.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_of_the_same_book_test() {
+  let input = [2, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 1600.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn empty_basket_test() {
+  let input = []
+  let output = book_store.lowest_price(input)
+  let expected = 0.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_different_books_test() {
+  let input = [1, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 1520.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_different_books_test() {
+  let input = [1, 2, 3]
+  let output = book_store.lowest_price(input)
+  let expected = 2160.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn four_different_books_test() {
+  let input = [1, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 2560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn five_different_books_test() {
+  let input = [1, 2, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 3000.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_groups_of_four_is_cheaper_than_group_of_five_plus_group_of_three_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5120.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_groups_of_four_is_cheaper_than_groups_of_five_and_three_test() {
+  let input = [1, 1, 2, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5120.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn group_of_four_plus_group_of_two_is_cheaper_than_two_groups_of_three_test() {
+  let input = [1, 1, 2, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 4080.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_each_of_first_four_books_and_one_copy_each_of_rest_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_copies_of_each_book_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 6000.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_copies_of_first_book_and_two_each_of_remaining_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1]
+  let output = book_store.lowest_price(input)
+  let expected = 6800.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_each_of_first_two_books_and_two_each_of_remaining_books_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 7520.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn four_groups_of_four_are_cheaper_than_two_groups_each_of_five_and_three_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 5, 1, 1, 2, 2, 3, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 10_240.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn check_that_groups_of_four_are_created_properly_even_when_there_are_more_groups_of_three_than_groups_of_five_test() {
+  let input = [1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 14_560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn one_group_of_one_and_four_is_cheaper_than_one_group_of_two_and_three_test() {
+  let input = [1, 1, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 3360.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn one_group_of_one_and_two_plus_three_groups_of_four_is_cheaper_than_one_group_of_each_size_test() {
+  let input = [1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 10_000.0
+  output
+  |> should.equal(expected)
+}