feat: on-demand section creation & 0.3.0.

deno.json

@@ -1,6 +1,6 @@
 {
   "name": "@textplace/core",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "exports": "./mod.ts",
   "imports": {
     "@deno/dnt": "jsr:@deno/dnt@^0.41.3"

logic/board.ts

@@ -9,15 +9,7 @@ import { applyChange, createSection } from "./section.ts";
 import type { BoardChange } from "../types/change.ts";
 
 export function createBoard(config: BoardConfig): BoardData {
-  const sections: SectionData[][] = Array(config.ySections)
+  return { config, sections: [] };
-    .fill(0)
-    .map((_, sy) =>
-      Array(config.xSections)
-        .fill(0)
-        .map((_, sx) => createSection({ sx, sy }, config))
-    );
-
-  return { config, sections };
 }
 
 export function locateSection(
@@ -30,9 +22,38 @@ export function locateSection(
   };
 }
 
+/**
+ * Get a section from board.
+ *
+ * If the section does not exist yet, it will be created and (optionally) added to `board`.
+ */
+export function getSectionOnBoard(
+  { sx, sy }: SectionPosition,
+  board: BoardData,
+  options: {
+    /**
+     * Whether the section data is only used for reading.
+     *
+     * If `true`, this function will return an empty section configured with default values, but will not add it to the board data to save storage.
+     */
+    readOnly: boolean;
+  } = { readOnly: false },
+): SectionData {
+  let section: SectionData;
+  if (!board.sections[sy] && !options.readOnly) board.sections[sy] = [];
+
+  if (!board.sections[sy]?.[sx]) {
+    section = createSection({ sx, sy }, board.config);
+    if (!options.readOnly) board.sections[sy][sx] = section;
+  } else {
+    section = board.sections[sy][sx];
+  }
+  return section;
+}
+
 export function applyChangeOnBoard(change: BoardChange, board: BoardData) {
-  const { sx, sy } = locateSection(change, board.config);
+  const sPos = locateSection(change, board.config);
-  const section = board.sections[sy][sx];
+  const section = getSectionOnBoard(sPos, board);
   applyChange(change, section);
 }
 
@@ -59,8 +80,8 @@ export function renderFullBoard(data: BoardData): FullBoard {
         continue;
       }
 
-      const { sx, sy } = locateSection({ x, y }, data.config);
+      const sPos = locateSection({ x, y }, data.config);
-      const section = data.sections[sy][sx];
+      const section = getSectionOnBoard(sPos, data, { readOnly: true });
       const xInSection = x % data.config.sectionWidth;
       const yInSection = y % data.config.sectionHeight;
 

tests/board.test.ts

@@ -3,7 +3,11 @@ import {
   assertEquals,
 } from "https://deno.land/std@0.224.0/assert/mod.ts";
 
-import { createBoard, renderFullBoard } from "../logic/board.ts";
+import {
+  createBoard,
+  getSectionOnBoard,
+  renderFullBoard,
+} from "../logic/board.ts";
 import type { BoardData } from "../types/board.ts";
 import { checkFullBoard } from "./checkFullBoard.ts";
 import { locateSection } from "../logic/board.ts";
@@ -14,8 +18,8 @@ Deno.test("board", async (t) => {
 
   await t.step("createBoard", () => {
     board = createBoard({
-      xSections: 2,
+      xSections: 3,
-      ySections: 2,
+      ySections: 3,
       sectionWidth: 4,
       sectionHeight: 3,
       defaultCh: " ",
@@ -24,17 +28,8 @@ Deno.test("board", async (t) => {
       defaultWidth: 1,
     });
 
-    assertEquals(board.sections.length, 2);
+    // Sections are created on demand.
-    assertEquals(board.sections[0].length, 2);
+    assertEquals(board.sections.length, 0);
-    assertEquals(board.sections[0][0].offsetX, 0);
-    assertEquals(board.sections[0][0].offsetY, 0);
-    assertEquals(board.sections[0][1].offsetX, 4);
-    assertEquals(board.sections[0][1].offsetY, 0);
-    assertEquals(board.sections[1].length, 2);
-    assertEquals(board.sections[1][0].offsetX, 0);
-    assertEquals(board.sections[1][0].offsetY, 3);
-    assertEquals(board.sections[1][1].offsetX, 4);
-    assertEquals(board.sections[1][1].offsetY, 3);
   });
 
   await t.step("locateSection", () => {
@@ -73,10 +68,53 @@ Deno.test("board", async (t) => {
     assertEquals(board.sections[1][1].ch[2][0], "嘛");
   });
 
+  await t.step("getSectionOnBoard: existing section", () => {
+    assert(board);
+
+    const section = getSectionOnBoard({ sx: 1, sy: 1 }, board, {
+      readOnly: true,
+    });
+    assertEquals(section.ch[0][0], "嘛");
+    assertEquals(section.color[0][0], "F");
+    assertEquals(section.bgColor[0][0], "0");
+    assertEquals(section.width[0][0], 2);
+  });
+
+  await t.step("getSectionOnBoard: non-existing row", () => {
+    assert(board);
+
+    const section = getSectionOnBoard({ sx: 1, sy: 2 }, board, {
+      readOnly: true,
+    });
+    assertEquals(section.ch[0][0], " ");
+    assertEquals(section.color[0][0], "F");
+    assertEquals(section.bgColor[0][0], "0");
+    assertEquals(section.width[0][0], 1);
+  });
+
+  await t.step("getSectionOnBoard: non-existing section", () => {
+    assert(board);
+
+    const section = getSectionOnBoard({ sx: 2, sy: 1 }, board, {
+      readOnly: true,
+    });
+    assertEquals(section.ch[0][0], " ");
+    assertEquals(section.color[0][0], "F");
+    assertEquals(section.bgColor[0][0], "0");
+    assertEquals(section.width[0][0], 1);
+  });
+
   await t.step("renderFullBoard", () => {
     assert(board);
 
     const rendered = renderFullBoard(board);
     checkFullBoard(rendered);
   });
+
+  await t.step("on-demand creation: only changed sections are saved", () => {
+    assert(board);
+
+    assertEquals(board.sections.length, 2);
+    assertEquals(board.sections[0].length, 2);
+  });
 });