In memory text editor improvements (#2526)

Added more tests. 
Fixed a bug with positionAt using crlf. 
General cleanup and simplification

## Checklist

- [x] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [/] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [/] I have not broken the cheatsheet

Author: AndreasArvidsson

packages/common/src/ide/inMemoryTextDocument/InMemoryTextDocument.ts

@@ -59,48 +59,43 @@ export class InMemoryTextDocument implements TextDocument {
   lineAt(lineOrPosition: number | Position): TextLine {
     const value =
       typeof lineOrPosition === "number" ? lineOrPosition : lineOrPosition.line;
-    const index = Math.min(Math.max(value, 0), this.lineCount - 1);
+    const index = clamp(value, 0, this.lineCount - 1);
     return this._lines[index];
   }
 
   offsetAt(position: Position): number {
-    if (position.isBefore(this._lines[0].range.start)) {
+    if (position.line < 0) {
       return 0;
     }
-    if (position.isAfter(this._lines.at(-1)!.range.end)) {
+    if (position.line > this._lines.length - 1) {
       return this._text.length;
     }
 
-    let offset = 0;
+    const line = this._lines[position.line];
 
-    for (const line of this._lines) {
-      if (position.line === line.lineNumber) {
-        return offset + Math.min(position.character, line.range.end.character);
-      }
-      offset += line.text.length + line.eolLength;
-    }
-
-    throw Error(`Couldn't find offset for position ${position}`);
+    return line.offset + clamp(position.character, 0, line.text.length);
   }
 
   positionAt(offset: number): Position {
-    if (offset < 0) {
-      return this._lines[0].range.start;
+    if (offset <= 0) {
+      return this.range.start;
     }
     if (offset >= this._text.length) {
-      return this._lines.at(-1)!.range.end;
+      return this.range.end;
     }
 
-    let currentOffset = 0;
+    const line = this._lines.find(
+      (line) => offset < line.offset + line.lengthIncludingEol,
+    );
 
-    for (const line of this._lines) {
-      if (currentOffset + line.text.length >= offset) {
-        return new Position(line.lineNumber, offset - currentOffset);
-      }
-      currentOffset += line.text.length + line.eolLength;
+    if (line == null) {
+      throw Error(`Couldn't find line for offset ${offset}`);
     }
 
-    throw Error(`Couldn't find position for offset ${offset}`);
+    return new Position(
+      line.lineNumber,
+      Math.min(offset - line.offset, line.text.length),
+    );
   }
 
   getText(range?: Range): string {
@@ -122,16 +117,22 @@ export class InMemoryTextDocument implements TextDocument {
 function createLines(text: string): InMemoryTextLine[] {
   const documentParts = text.split(/(\r?\n)/g);
   const result: InMemoryTextLine[] = [];
+  let offset = 0;
 
   for (let i = 0; i < documentParts.length; i += 2) {
-    result.push(
-      new InMemoryTextLine(
-        result.length,
-        documentParts[i],
-        documentParts[i + 1],
-      ),
+    const line = new InMemoryTextLine(
+      result.length,
+      offset,
+      documentParts[i],
+      documentParts[i + 1],
     );
+    result.push(line);
+    offset += line.lengthIncludingEol;
   }
 
   return result;
 }
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(Math.max(value, min), max);
+}

packages/common/src/ide/inMemoryTextDocument/InMemoryTextLine.ts

@@ -9,15 +9,16 @@ export class InMemoryTextLine implements TextLine {
   readonly firstNonWhitespaceCharacterIndex: number;
   readonly lastNonWhitespaceCharacterIndex: number;
   readonly isEmptyOrWhitespace: boolean;
-  readonly eolLength: number;
+  readonly lengthIncludingEol: number;
 
   constructor(
     public lineNumber: number,
+    public offset: number,
     public text: string,
     eol: string | undefined,
   ) {
     this.isEmptyOrWhitespace = /^\s*$/.test(text);
-    this.eolLength = eol?.length ?? 0;
+    this.lengthIncludingEol = text.length + (eol?.length ?? 0);
     const start = new Position(lineNumber, 0);
     const end = new Position(lineNumber, text.length);
     const endIncludingLineBreak =

packages/common/src/ide/inMemoryTextDocument/test/InMemoryTextDocument.test.ts

@@ -62,6 +62,7 @@ suite("InMemoryTextDocument", () => {
     assert.equal(document.offsetAt(new Position(0, 0)), 0);
     assert.equal(document.offsetAt(new Position(0, 7)), 7);
     assert.equal(document.offsetAt(new Position(0, 100)), 7);
+    assert.equal(document.offsetAt(new Position(1, -100)), 8);
     assert.equal(document.offsetAt(new Position(1, 0)), 8);
     assert.equal(document.offsetAt(new Position(1, 2)), 10);
     assert.equal(document.offsetAt(new Position(2, 0)), 17);
@@ -74,11 +75,21 @@ suite("InMemoryTextDocument", () => {
 
     assert.equal(document.positionAt(-1), "0:0");
     assert.equal(document.positionAt(0).toString(), "0:0");
+    assert.equal(document.positionAt(6).toString(), "0:6");
     assert.equal(document.positionAt(7).toString(), "0:7");
     assert.equal(document.positionAt(8).toString(), "1:0");
     assert.equal(document.positionAt(10).toString(), "1:2");
     assert.equal(document.positionAt(17).toString(), "2:0");
     assert.equal(document.positionAt(document.text.length).toString(), "2:0");
     assert.equal(document.positionAt(100).toString(), "2:0");
   });
+
+  test("positionAt CRLF", () => {
+    const document = createTestDocument("a\r\nb");
+
+    assert.equal(document.positionAt(0).toString(), "0:0");
+    assert.equal(document.positionAt(1).toString(), "0:1");
+    assert.equal(document.positionAt(2).toString(), "0:1");
+    assert.equal(document.positionAt(3).toString(), "1:0");
+  });
 });

packages/common/src/ide/inMemoryTextDocument/test/InMemoryTextDocumentEdit.test.ts

@@ -9,20 +9,23 @@ suite("InMemoryTextDocument.edit", () => {
     const document = createTestDocument(text);
     document.edit([{ range: new Range(0, 0, 0, 5), text: "goodbye" }]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "goodbye\nworld");
   });
 
   test("remove", () => {
     const document = createTestDocument(text);
     document.edit([{ range: new Range(0, 0, 1, 0), text: "" }]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "world");
   });
 
   test("insert", () => {
     const document = createTestDocument(text);
     document.edit([{ range: new Range(0, 5, 0, 5), text: "!" }]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "hello!\nworld");
   });
 
@@ -35,6 +38,7 @@ suite("InMemoryTextDocument.edit", () => {
       { range: new Range(0, 0, 0, 0), text: "ccc" },
     ]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "aaabbbccc");
 
     assert.equal(changes[0].range.toString(), "0:0-0:0");
@@ -53,6 +57,7 @@ suite("InMemoryTextDocument.edit", () => {
       { range: new Range(0, 0, 0, 5), text: "goodbye" },
     ]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "goodbye!\norld");
   });
 
@@ -63,6 +68,7 @@ suite("InMemoryTextDocument.edit", () => {
       { range: new Range(0, 1, 1, 1), text: "" },
     ]);
 
+    assert.equal(document.version, 1);
     assert.equal(document.text, "orld");
     assert.equal(changes.length, 1);
     assert.equal(changes[0].range.toString(), "0:0-1:1");