JS: Support multiple cursors

js/src/__tests__/index.test.ts

@@ -159,10 +159,12 @@ describe('Basin', () => {
 		basin.setCursor({ jsonPath: 'list[0]', p: -1 })
 		basin.setCursor({ jsonPath: 'list[1]', p: -1 }, '1')
 		basin.setCursor({ jsonPath: 'list[2]', p: -1 }, '2')
-		expect(basin.write("there")).to.deep.equal({ list: ["Hello there", "Hi ", "Hey "] })
-		expect(basin.write("guy", '1')).to.deep.equal({ list: ["Hello there", "Hi you", "Hey "] })
-		expect(basin.write("you", '2')).to.deep.equal({ list: ["Hello there", "Hi you", "Hey you"] })
-		expect(basin.write(".", '1')).to.deep.equal({ list: ["Hello there.", "Hi you.", "Hey you"] })
-		expect(basin.write("!", '2')).to.deep.equal({ list: ["Hello there.", "Hi you.", "Hey you!"] })
+		expect(basin.write("there")).to.deep.equal(["Hello there", "Hi ", "Hey "])
+		expect(basin.write("guy", '1')).to.deep.equal(["Hello there", "Hi guy", "Hey "])
+		expect(basin.write("you", '2')).to.deep.equal(["Hello there", "Hi guy", "Hey you"])
+		expect(basin.write(".")).to.deep.equal(["Hello there.", "Hi guy", "Hey you"] )
+		expect(basin.write(".", '1')).to.deep.equal(["Hello there.", "Hi guy.", "Hey you"] )
+		expect(basin.write("!", '2')).to.deep.equal(["Hello there.", "Hi guy.", "Hey you!"])
+		expect(basin.items).to.deep.equal({ list: ["Hello there.", "Hi guy.", "Hey you!"] })
 	})
 })

js/src/index.ts

@@ -43,17 +43,18 @@ export class BasinCursor {
  * @typeparam T The type of values (top level) that will be modified.
  */
 export class Basin<T> {
-	private _currentKey?: T
+	private readonly _cursors = new Map<string | null | undefined, BasinCursor>()
+	private readonly _keys = new Map<string | null | undefined, string>()
 
 	/**
 	 * @param items The items to contain. If not provided, an empty object will be created.
 	 * @param _cursor The cursor to use. If not provided, then it must be provided later by calling {@link setCursor}.
 	 */
 	public constructor(
 		public items: any = {},
-		private _cursor?: BasinCursor) {
-		if (_cursor !== undefined) {
-			this.setCursor(_cursor)
+		cursor?: BasinCursor) {
+		if (cursor !== undefined) {
+			this.setCursor(cursor)
 		}
 	}
 
@@ -86,7 +87,7 @@ export class Basin<T> {
 	 * @param cursor The cursor to use.
 	 */
 	public setCursor(cursor: BasinCursor, label?: string): void {
-		this._cursor = cursor
+		this._cursors.set(label, cursor)
 		if (cursor.j !== undefined) {
 			cursor.jsonPath = cursor.j
 			delete cursor.j
@@ -103,7 +104,7 @@ export class Basin<T> {
 		const expressions = jp.parse(cursor.jsonPath!)
 		for (const expression of expressions) {
 			if (expression.expression.type !== 'root') {
-				this._currentKey = expression.expression.value
+				this._keys.set(label, expression.expression.value)
 				break
 			}
 		}
@@ -117,7 +118,7 @@ export class Basin<T> {
 	 */
 	public write(value?: any, cursorLabel?: string): T {
 		// For efficiency, assume the cursor is set.
-		const cursor = this._cursor!
+		const cursor = this._cursors.get(cursorLabel)!
 		const position = cursor.position
 		const jsonPath = cursor.jsonPath!
 		if (typeof position !== 'number') {
@@ -152,6 +153,7 @@ export class Basin<T> {
 			})
 		}
 
-		return this.items[this._currentKey]
+		const key = this._keys.get(cursorLabel)!
+		return this.items[key]
 	}
 }