fix: apply change for 2-w at alternate position

logic/section.ts

@@ -7,6 +7,11 @@ export function createSection(
   { sx, sy }: SectionPosition,
   boardConfig: BoardConfig
 ): SectionData {
+  if (boardConfig.sectionWidth % 2 !== 0)
+    throw new Error(
+      "sectionWidth must be multiple of 2 (least common multiples of all character widths)"
+    );
+
   const offsetX = sx * boardConfig.sectionWidth;
   const offsetY = sy * boardConfig.sectionHeight;
 
@@ -32,8 +37,10 @@ export function applyChange(change: BoardChange, section: SectionData) {
 
   if (change.ch) {
     const chWidth = getCharacterWidth(change.ch);
-    section.ch[yInSection][xInSection] = change.ch;
-    section.width[yInSection][xInSection] = chWidth;
+    const xCharacterOffset = xInSection % 2;
+    const offsetAdjustedXInSection = xInSection - xCharacterOffset;
+    section.ch[yInSection][offsetAdjustedXInSection] = change.ch;
+    section.width[yInSection][offsetAdjustedXInSection] = chWidth;
   }
   if (change.color) {
     section.color[yInSection][xInSection] = change.color;

tests/section.test.ts

@@ -1,9 +1,18 @@
-import { assertEquals } from "https://deno.land/std@0.224.0/assert/mod.ts";
+import {
+  assert,
+  assertEquals,
+  assertThrows,
+} from "https://deno.land/std@0.224.0/assert/mod.ts";
 
-import { createSection } from "../logic/section.ts";
+import { applyChange, createSection } from "../logic/section.ts";
+import type { SectionData } from "../types/section.ts";
 
-Deno.test("createSection", () => {
-  const section = createSection(
+Deno.test("section", async (t) => {
+  let section: SectionData | undefined;
+
+  await t.step("createSection non-lcm", () => {
+    assertThrows(() => {
+      createSection(
         { sx: 0, sy: 0 },
         {
           xSections: 2,
@@ -16,38 +25,91 @@ Deno.test("createSection", () => {
           defaultWidth: 1,
         }
       );
+    });
+  });
+
+  await t.step("createSection non-origin section", () => {
+    section = createSection(
+      { sx: 1, sy: 1 },
+      {
+        xSections: 2,
+        ySections: 2,
+        sectionWidth: 4,
+        sectionHeight: 3,
+        defaultCh: " ",
+        defaultColor: "F",
+        defaultBgColor: "0",
+        defaultWidth: 1,
+      }
+    );
+
+    assertEquals(section.offsetX, 4);
+    assertEquals(section.offsetY, 3);
+  });
+
+  await t.step("createSection", () => {
+    section = createSection(
+      { sx: 0, sy: 0 },
+      {
+        xSections: 2,
+        ySections: 2,
+        sectionWidth: 4,
+        sectionHeight: 3,
+        defaultCh: " ",
+        defaultColor: "F",
+        defaultBgColor: "0",
+        defaultWidth: 1,
+      }
+    );
 
     assertEquals(section.offsetX, 0);
     assertEquals(section.offsetY, 0);
-  assertEquals(section.ch.length, 3);
-  for (const row of section.ch) {
-    assertEquals(row.length, 3);
-    for (const ch of row) {
-      assertEquals(ch, " ");
+
+    function assertSectionContent<T>(
+      content: T[][],
+      rowCount: number,
+      columnCount: number,
+      value: T
+    ) {
+      assertEquals(content.length, rowCount);
+      for (const row of content) {
+        assertEquals(row.length, columnCount);
+        for (const item of row) {
+          assertEquals(item, value);
+        }
       }
     }
 
-  assertEquals(section.color.length, 3);
-  for (const row of section.color) {
-    assertEquals(row.length, 3);
-    for (const color of row) {
-      assertEquals(color, "F");
-    }
-  }
-
-  assertEquals(section.bgColor.length, 3);
-  for (const row of section.bgColor) {
-    assertEquals(row.length, 3);
-    for (const bgColor of row) {
-      assertEquals(bgColor, "0");
-    }
-  }
-
-  assertEquals(section.width.length, 3);
-  for (const row of section.width) {
-    assertEquals(row.length, 3);
-    for (const width of row) {
-      assertEquals(width, 1);
-    }
-  }
+    assertSectionContent(section.ch, 3, 4, " ");
+    assertSectionContent(section.color, 3, 4, "F");
+    assertSectionContent(section.bgColor, 3, 4, "0");
+    assertSectionContent(section.width, 3, 4, 1);
+  });
+
+  await t.step("applyChange 1-width", () => {
+    assert(section);
+
+    applyChange({ x: 0, y: 0, ch: "t" }, section);
+    assertEquals(section.ch[0][0], "t");
+    assertEquals(section.ch[0][1], " ");
+    assertEquals(section.width[0][0], 1);
+  });
+
+  await t.step("applyChange 2-width at a correct position", () => {
+    assert(section);
+
+    applyChange({ x: 0, y: 0, ch: "あ" }, section);
+    assertEquals(section.ch[0][0], "あ");
+    assertEquals(section.ch[0][1], " ");
+    assertEquals(section.width[0][0], 2);
+  });
+
+  await t.step("applyChange 2-width at an alternate position", () => {
+    assert(section);
+
+    applyChange({ x: 1, y: 0, ch: "あ" }, section);
+    assertEquals(section.ch[0][0], "あ");
+    assertEquals(section.ch[0][1], " ");
+    assertEquals(section.width[0][0], 2);
+  });
 });

types/board.ts

@@ -36,6 +36,11 @@ export interface CharacterPosition {
 export interface BoardConfig {
   xSections: number;
   ySections: number;
+  /**
+   * Width of each section, in display characters.
+   *
+   * Note that this must be a multiple of the least common multiple of all possible character display width (returned by `getCharacterWidth`).
+   */
   sectionWidth: number;
   sectionHeight: number;