Add micro-blog exercise

config.json

@@ -47,6 +47,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "micro-blog",
+        "name": "Micro Blog",
+        "uuid": "45dc52f5-2e84-4a52-8272-bb4b1e36b43b",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "collatz-conjecture",
         "name": "Collatz Conjecture",

exercises/practice/micro-blog/.docs/instructions.append.md

@@ -0,0 +1,5 @@
+## Reserved Memory
+
+The buffer for the UTF-8 input string uses bytes 64-319 of linear memory.
+
+The input string can be modified in place if desired.

exercises/practice/micro-blog/.docs/instructions.md

@@ -0,0 +1,37 @@
+# Instructions
+
+You have identified a gap in the social media market for very very short posts.
+Now that Twitter allows 280 character posts, people wanting quick social media updates aren't being served.
+You decide to create your own social media network.
+
+To make your product noteworthy, you make it extreme and only allow posts of 5 or less characters.
+Any posts of more than 5 characters should be truncated to 5.
+
+To allow your users to express themselves fully, you allow Emoji and other Unicode.
+
+The task is to truncate input strings to 5 characters.
+
+## Text Encodings
+
+Text stored digitally has to be converted to a series of bytes.
+There are 3 ways to map characters to bytes in common use.
+
+- **ASCII** can encode English language characters.
+  All characters are precisely 1 byte long.
+- **UTF-8** is a Unicode text encoding.
+  Characters take between 1 and 4 bytes.
+- **UTF-16** is a Unicode text encoding.
+  Characters are either 2 or 4 bytes long.
+
+UTF-8 and UTF-16 are both Unicode encodings which means they're capable of representing a massive range of characters including:
+
+- Text in most of the world's languages and scripts
+- Historic text
+- Emoji
+
+UTF-8 and UTF-16 are both variable length encodings, which means that different characters take up different amounts of space.
+
+Consider the letter 'a' and the emoji '😛'.
+In UTF-16 the letter takes 2 bytes but the emoji takes 4 bytes.
+
+The trick to this exercise is to use APIs designed around Unicode characters (codepoints) instead of Unicode codeunits.

exercises/practice/micro-blog/.eslintrc

@@ -0,0 +1,18 @@
+{
+  "root": true,
+  "extends": "@exercism/eslint-config-javascript",
+  "env": {
+    "jest": true
+  },
+  "overrides": [
+    {
+      "files": [
+        "*.spec.js"
+      ],
+      "excludedFiles": [
+        "custom.spec.js"
+      ],
+      "extends": "@exercism/eslint-config-javascript/maintainers"
+    }
+  ]
+}

exercises/practice/micro-blog/.meta/config.json

@@ -0,0 +1,26 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "micro-blog.wat"
+    ],
+    "test": [
+      "micro-blog.spec.js"
+    ],
+    "example": [
+      ".meta/proof.ci.wat"
+    ],
+    "invalidator": [
+      "package.json"
+    ]
+  },
+  "blurb": "Given an input string, truncate it to 5 characters.",
+  "custom": {
+    "version.tests.compatibility": "jest-27",
+    "flag.tests.task-per-describe": false,
+    "flag.tests.may-run-long": false,
+    "flag.tests.includes-optional": false
+  }
+}

exercises/practice/micro-blog/.meta/proof.ci.wat

@@ -0,0 +1,82 @@
+(module
+  (memory (export "mem") 1)
+
+  ;;
+  ;; Truncate UTF-8 input string to 5 characters
+  ;;
+  ;; @param {i32} offset - The offset of the input string in linear memory
+  ;; @param {i32} length - The length of the input string in linear memory
+  ;;
+  ;; @returns {(i32,i32)} - The offset and length of the truncated string in linear memory
+  ;;
+  (func (export "truncate") (param $offset i32) (param $length i32) (result i32 i32)
+
+    (local $index i32)
+    (local $stop i32)
+    (local $remaining i32)
+    (local $byte i32)
+    (local $step i32)
+
+    (local.set $index (local.get $offset))
+    (local.set $stop
+      (i32.add
+        (local.get $offset)
+        (local.get $length)
+      )
+    )
+    (local.set $remaining (i32.const 5))
+
+    (loop
+      (if (i32.or (i32.eqz (local.get $remaining))
+                  (i32.eq (local.get $index) (local.get $stop)))
+        (then (return (local.get $offset)
+                      (i32.sub (local.get $index) (local.get $offset)))
+        )
+      )
+
+      (local.set
+        $remaining
+        (i32.sub
+          (local.get $remaining)
+          (i32.const 1)
+        )
+      )
+
+      (local.set $byte (i32.load8_u (local.get $index)))
+
+      (if (i32.eq (i32.const 0xf0) (i32.and (i32.const 0xf0) (local.get $byte)))
+        (then
+          (local.set $step (i32.const 4))
+        )
+        (else
+          (if (i32.eq (i32.const 0xe0) (i32.and (i32.const 0xe0) (local.get $byte)))
+            (then
+              (local.set $step (i32.const 3))
+            )
+            (else
+              (if (i32.eq (i32.const 0xc0) (i32.and (i32.const 0xc0) (local.get $byte)))
+                (then
+                  (local.set $step (i32.const 2))
+                )
+                (else
+                  (local.set $step (i32.const 1))
+                )
+              )
+            )
+          )
+        )
+      )
+
+      (local.set
+        $index
+        (i32.add
+          (local.get $index)
+          (local.get $step)
+        )
+      )
+
+      (br 0)
+    )
+    (unreachable)
+  )
+)

exercises/practice/micro-blog/.meta/tests.toml

@@ -0,0 +1,46 @@
+# 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.
+
+[b927b57f-7c98-42fd-8f33-fae091dc1efc]
+description = "English language short"
+
+[a3fcdc5b-0ed4-4f49-80f5-b1a293eac2a0]
+description = "English language long"
+
+[01910864-8e15-4007-9c7c-ac956c686e60]
+description = "German language short (broth)"
+
+[f263e488-aefb-478f-a671-b6ba99722543]
+description = "German language long (bear carpet → beards)"
+
+[0916e8f1-41d7-4402-a110-b08aa000342c]
+description = "Bulgarian language short (good)"
+
+[bed6b89c-03df-4154-98e6-a61a74f61b7d]
+description = "Greek language short (health)"
+
+[485a6a70-2edb-424d-b999-5529dbc8e002]
+description = "Maths short"
+
+[8b4b7b51-8f48-4fbe-964e-6e4e6438be28]
+description = "Maths long"
+
+[71f4a192-0566-4402-a512-fe12878be523]
+description = "English and emoji short"
+
+[6f0f71f3-9806-4759-a844-fa182f7bc203]
+description = "Emoji short"
+
+[ce71fb92-5214-46d0-a7f8-d5ba56b4cc6e]
+description = "Emoji long"
+
+[5dee98d2-d56e-468a-a1f2-121c3f7c5a0b]
+description = "Royal Flush?"

exercises/practice/micro-blog/.npmrc

@@ -0,0 +1 @@
+audit=false

exercises/practice/micro-blog/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Exercism
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

exercises/practice/micro-blog/babel.config.js

@@ -0,0 +1,4 @@
+export default {
+  presets: ["@exercism/babel-preset-javascript"],
+  plugins: [],
+};

exercises/practice/micro-blog/micro-blog.spec.js

@@ -0,0 +1,126 @@
+import { compileWat, WasmRunner } from "@exercism/wasm-lib";
+
+let wasmModule;
+let currentInstance;
+
+beforeAll(async () => {
+  try {
+    const watPath = new URL("./micro-blog.wat", import.meta.url);
+    const { buffer } = await compileWat(watPath);
+    wasmModule = await WebAssembly.compile(buffer);
+  } catch (err) {
+    console.log(`Error compiling *.wat: \n${err}`);
+    process.exit(1);
+  }
+});
+
+function truncate(input) {
+  const inputBufferOffset = 64;
+  const inputBufferCapacity = 256;
+
+  const inputLengthEncoded = new TextEncoder().encode(input).length;
+  if (inputLengthEncoded > inputBufferCapacity) {
+    throw new Error(
+      `String is too large for buffer of size ${inputBufferCapacity} bytes`
+    );
+  }
+
+  currentInstance.set_mem_as_utf8(inputBufferOffset, inputLengthEncoded, input);
+
+  // Pass offset and length to WebAssembly function
+  const [outputOffset, outputLength] = currentInstance.exports.truncate(
+    inputBufferOffset,
+    inputLengthEncoded
+  );
+
+  // Decode JS string from returned offset and length
+  return currentInstance.get_mem_as_utf8(outputOffset, outputLength);
+}
+
+describe("Truncate", () => {
+  beforeEach(async () => {
+    currentInstance = null;
+    if (!wasmModule) {
+      return Promise.reject();
+    }
+    try {
+      currentInstance = await new WasmRunner(wasmModule);
+      return Promise.resolve();
+    } catch (err) {
+      console.log(`Error instantiating WebAssembly module: ${err}`);
+      return Promise.reject();
+    }
+  });
+
+  test("English language short", () => {
+    const expected = "Hi";
+    const actual = truncate("Hi");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("English language long", () => {
+    const expected = "Hello";
+    const actual = truncate("Hello there");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("German language short (broth)", () => {
+    const expected = "brühe";
+    const actual = truncate("brühe");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("German language long (bear carpet → beards)", () => {
+    const expected = "Bärte";
+    const actual = truncate("Bärteppich");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Bulgarian language short (good)", () => {
+    const expected = "Добър";
+    const actual = truncate("Добър");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Greek language short (health)", () => {
+    const expected = "υγειά";
+    const actual = truncate("υγειά");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Maths short", () => {
+    const expected = "a=πr²";
+    const actual = truncate("a=πr²");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Maths long", () => {
+    const expected = "∅⊊ℕ⊊ℤ";
+    const actual = truncate("∅⊊ℕ⊊ℤ⊊ℚ⊊ℝ⊊ℂ");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("English and emoji short", () => {
+    const expected = "Fly 🛫";
+    const actual = truncate("Fly 🛫");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Emoji short", () => {
+    const expected = "💇";
+    const actual = truncate("💇");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Emoji long", () => {
+    const expected = "❄🌡🤧🤒🏥";
+    const actual = truncate("❄🌡🤧🤒🏥🕰😀");
+    expect(actual).toEqual(expected);
+  });
+
+  xtest("Royal Flush?", () => {
+    const expected = "🃎🂸🃅🃋🃍";
+    const actual = truncate("🃎🂸🃅🃋🃍🃁🃊");
+    expect(actual).toEqual(expected);
+  });
+});