Progress on canvas module

src/lib/painter/canvas.ts

@@ -1,4 +1,6 @@
 import { type CursorPos } from 'node:readline'
+import { type Either, fold, type Left, left, right } from '../util/basic/either'
+import { PaintCursorError } from './errors'
 
 // Cursor stuffs
 interface CursorPosX {
@@ -11,14 +13,35 @@ interface CursorPosY {
   readonly value: number
 }
 
-const cursorPosX = (x: number): CursorPosX => ({_tag: 'X', value: x})
+type CursorPosVal = (str: 'X' | 'Y') => (x: number) => CursorPosX | CursorPosY
+const cursorPosVal: CursorPosVal = str => x => ({_tag: str, value: x})
 
-const cursorPosY = (x: number): CursorPosY => ({_tag: 'Y', value: x})
+type IsCursorPos = (x: 'X' | 'Y') => (y: CursorPosX | CursorPosY) => boolean
-
-type IsCursorPos =
-  (x: 'X' | 'Y') => (y: CursorPosX | CursorPosY) => boolean
 const isCursorPos: IsCursorPos = x => y => y._tag === x
 
+const cursorPos = (x: number) => (y: number): CursorPos => ({rows: x, cols: y})
+
+// Cursor Position
+type SafeCursorPos =
+  (x: CursorPosX | CursorPosY) =>
+    (y: CursorPosX | CursorPosY) => Either<CursorPos, Error>
+const safeCursorPos: SafeCursorPos = (x) => y => {
+  return isCursorPos('X')(x) && isCursorPos('Y')(y)
+    ? right(cursorPos(x.value)(y.value))
+    : isCursorPos('Y')(x) && isCursorPos('X')(y)
+    ? right(cursorPos(y.value)(x.value))
+    : left(
+      new PaintCursorError(
+        `Both arguments provided were of the same axis, or otherwise invalid.`,
+        {x, y},
+      ),
+    )
+}
+
+console.log(
+  safeCursorPos(cursorPosVal('X')(5))(cursorPosVal('X')(7)),
+)
+
 // Tagged types
 interface CanvasOrigin {
   readonly _tag: 'Origin'
@@ -30,15 +53,23 @@ interface CanvasEnd {
   readonly value: CursorPos
 }
 
+type CanvasOriginConstructor = (x: SafeCursorPos) => Either<CanvasOrigin, E>
+const canvasOrigin = (x: CursorPos): CanvasOrigin => ({
+  _tag: 'Origin',
+  value: x,
+})
+
+const canvasEnd = (x: CursorPos): CanvasEnd => ({
+  _tag: 'End',
+  value: x,
+})
+
 // Canvas type using tagged positions
 type Canvas = {
   origin: CanvasOrigin,
   end: CanvasEnd,
 }
 
-// Cursor Position
-// const cursorPos: CursorPos = ()
-
 // Constructor helpers
 const origin = (pos: CursorPos): CanvasOrigin => ({
   _tag: 'Origin',
@@ -51,11 +82,10 @@ const end = (pos: CursorPos): CanvasEnd => ({
 })
 
 // Curried canvas creator with type safety
-const canvas =
+const canvas = (origin: CanvasOrigin) => (end: CanvasEnd): Canvas => ({
-  (origin: CanvasOrigin) => (end: CanvasEnd): Canvas => ({
+  origin,
-    origin,
+  end,
-    end,
+})
-  })
 
 // Usage with proper type safety
 const myCanvas = canvas(origin({rows: 3, cols: 1}))(

src/lib/painter/errors.ts

@@ -0,0 +1,12 @@
+export class PaintCursorError extends Error {
+  cursorX
+  cursorY
+
+  constructor(message: string, {x, y}: {x: unknown, y: unknown}) {
+    super(message)
+
+    this.name = this.constructor.name
+    this.cursorX = !x ? 'No data' : x
+    this.cursorY = !y ? 'No data' : y
+  }
+}