First implementation of 10 finger typing

tippen/src/lib/__tests__/fingers.test.ts

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+import { describe, expect, it } from "vitest";
+
+import {
+  FINGERS,
+  GRUNDSTELLUNG,
+  KEYBOARD_ROWS,
+  fingerOf,
+  handOf,
+  homeKeyOf,
+  keysInRow,
+  rowOf,
+  shiftHandFor,
+} from "../fingers";
+
+const ALPHABET = "abcdefghijklmnopqrstuvwxyzäöüß";
+
+describe("fingerOf", () => {
+  it("maps every German letter to exactly one finger", () => {
+    for (const key of ALPHABET) expect(fingerOf(key), key).not.toBeNull();
+  });
+
+  it("is case-insensitive", () => {
+    for (const key of ALPHABET) {
+      // "ß".toUpperCase() is "SS" - two characters, and not a key. `event.key` never
+      // reports that, so the single-character case is the one that has to hold.
+      const gross = key.toUpperCase();
+      if ([...gross].length !== 1) continue;
+      expect(fingerOf(gross)?.id, gross).toBe(fingerOf(key)?.id);
+    }
+  });
+
+  it("returns null for keys that are not on the layout", () => {
+    for (const key of ["Enter", "F1", "€", ""]) expect(fingerOf(key)).toBeNull();
+  });
+
+  it("assigns the Grundstellung to the eight home fingers, left to right", () => {
+    const expected = [
+      "links-klein",
+      "links-ring",
+      "links-mitte",
+      "links-zeige",
+      "rechts-zeige",
+      "rechts-mitte",
+      "rechts-ring",
+      "rechts-klein",
+    ];
+    GRUNDSTELLUNG.forEach((key, i) => expect(fingerOf(key)?.id).toBe(expected[i]));
+  });
+
+  it("gives each finger the home key it actually rests on", () => {
+    for (const key of GRUNDSTELLUNG) expect(homeKeyOf(key)).toBe(key);
+    expect(homeKeyOf(" ")).toBe(" ");
+  });
+
+  it("sends the two index fingers to their stretch keys", () => {
+    for (const key of "rtfgvb") expect(fingerOf(key)?.id).toBe("links-zeige");
+    for (const key of "zuhjnm") expect(fingerOf(key)?.id).toBe("rechts-zeige");
+  });
+});
+
+describe("hands", () => {
+  it("splits the letters into two disjoint, non-empty sets", () => {
+    const links = [...ALPHABET].filter((key) => handOf(key) === "links");
+    const rechts = [...ALPHABET].filter((key) => handOf(key) === "rechts");
+    expect(links.length).toBeGreaterThan(0);
+    expect(rechts.length).toBeGreaterThan(0);
+    expect(links.length + rechts.length).toBe(ALPHABET.length);
+    expect(links.some((key) => rechts.includes(key))).toBe(false);
+  });
+
+  it("shifts with the opposite hand", () => {
+    expect(shiftHandFor("a")).toBe("rechts");
+    expect(shiftHandFor("l")).toBe("links");
+    expect(shiftHandFor("Enter")).toBeNull();
+  });
+});
+
+describe("rows", () => {
+  it("places every letter in a row", () => {
+    for (const key of ALPHABET) expect(rowOf(key), key).not.toBeNull();
+  });
+
+  it("has the Grundstellung in the Grundreihe", () => {
+    for (const key of GRUNDSTELLUNG) expect(rowOf(key)).toBe("grund");
+  });
+
+  it("draws three rows, each with keys", () => {
+    expect(KEYBOARD_ROWS).toHaveLength(3);
+    for (const row of KEYBOARD_ROWS) expect(keysInRow(row).length).toBeGreaterThan(0);
+  });
+});
+
+describe("FINGERS", () => {
+  it("gives every finger a distinct hue so the colours can be named", () => {
+    const hues = Object.values(FINGERS).map((finger) => finger.hue);
+    expect(new Set(hues).size).toBe(hues.length);
+  });
+
+  it("keeps each finger's id and key consistent", () => {
+    for (const [id, finger] of Object.entries(FINGERS)) expect(finger.id).toBe(id);
+  });
+});