Merge pull request #719 from streamich/perf-editor-iterators

Improve and generalize character iteration in `Editor`

Author: streamich

src/json-crdt-extensions/peritext/Peritext.ts

@@ -132,7 +132,7 @@ export class Peritext<T = string> implements Printable {
     // TODO: Provide ability to attach to the end of the text?
     const str = this.str;
     const id = str.find(pos);
-    if (!id) return this.point(str.id, Anchor.After);
+    if (!id) return this.point(str.id, pos ? Anchor.Before : Anchor.After);
     return this.point(id, anchor);
   }
 

src/json-crdt-extensions/peritext/editor/Editor.ts

@@ -104,92 +104,47 @@ export class Editor<T = string> {
   }
 
   /**
-   * Returns a forward iterator through visible text, one character at a time,
-   * starting from a given chunk and offset.
+   * Returns an iterator through visible text, one `step` characters at a time,
+   * starting from a given {@link Point}.
    *
-   * @param chunk Chunk to start from.
-   * @param offset Offset in the chunk to start from.
+   * @param start The starting point.
+   * @param step Number of visible characters to skip.
    * @returns The next visible character iterator.
    */
-  public fwd0(chunk: undefined | Chunk<T>, offset: number): CharIterator<T> {
-    const str = this.txt.str;
+  public walk(start: Point<T>, step: number = 1): CharIterator<T> {
+    let point: Point<T> | undefined = start.clone();
     return () => {
-      if (!chunk) return;
-      const span = chunk.span;
-      const offsetToReturn = offset;
-      const chunkToReturn = chunk;
-      if (offset >= span) return;
-      offset++;
-      if (offset >= span) {
-        offset = 0;
-        chunk = str.next(chunk);
-        while (chunk && chunk.del) chunk = str.next(chunk);
-      }
-      return new ChunkSlice<T>(chunkToReturn, offsetToReturn, 1);
+      if (!point) return;
+      const char = step > 0 ? point.rightChar() : point.leftChar();
+      if (!char) return (point = undefined);
+      const end = point.move(step);
+      if (end) point = undefined;
+      return char;
     };
   }
 
   /**
    * Returns a forward iterator through visible text, one character at a time,
-   * starting from a given ID.
+   * starting from a given {@link Point}.
    *
-   * @param id ID to start from.
+   * @param start The starting point.
    * @param chunk Chunk to start from.
    * @returns The next visible character iterator.
    */
-  public fwd1(id: ITimestampStruct, chunk?: Chunk<T>): CharIterator<T> {
-    const str = this.txt.str;
-    const startFromStrRoot = equal(id, str.id);
-    if (startFromStrRoot) {
-      chunk = str.first();
-      while (chunk && chunk.del) chunk = str.next(chunk);
-      return this.fwd0(chunk, 0);
-    }
-    let offset: number = 0;
-    if (!chunk || !contains(chunk.id, chunk.span, id, 1)) {
-      chunk = str.findById(id);
-      if (!chunk) return () => undefined;
-      offset = id.time - chunk.id.time;
-    } else offset = id.time - chunk.id.time;
-    if (!chunk.del) return this.fwd0(chunk, offset);
-    while (chunk && chunk.del) chunk = str.next(chunk);
-    return this.fwd0(chunk, 0);
+  public fwd(start: Point<T>): CharIterator<T> {
+    return this.walk(start, 1);
   }
 
-  public bwd0(chunk: undefined | Chunk<T>, offset: number): CharIterator<T> {
-    const txt = this.txt;
-    const str = txt.str;
-    return () => {
-      if (!chunk || offset < 0) return;
-      const offsetToReturn = offset;
-      const chunkToReturn = chunk;
-      offset--;
-      if (offset < 0) {
-        chunk = str.prev(chunk);
-        while (chunk && chunk.del) chunk = str.prev(chunk);
-        if (chunk) offset = chunk.span - 1;
-      }
-      return new ChunkSlice(chunkToReturn, offsetToReturn, 1);
-    };
-  }
-
-  public bwd1(id: ITimestampStruct, chunk?: Chunk<T>): CharIterator<T> {
-    const str = this.txt.str;
-    const startFromStrRoot = equal(id, str.id);
-    if (startFromStrRoot) {
-      chunk = str.last();
-      while (chunk && chunk.del) chunk = str.prev(chunk);
-      return this.bwd0(chunk, chunk ? chunk.span - 1 : 0);
-    }
-    let offset: number = 0;
-    if (!chunk || !contains(chunk.id, chunk.span, id, 1)) {
-      chunk = str.findById(id);
-      if (!chunk) return () => undefined;
-      offset = id.time - chunk.id.time;
-    } else offset = id.time - chunk.id.time;
-    if (!chunk.del) return this.bwd0(chunk, offset);
-    while (chunk && chunk.del) chunk = str.prev(chunk);
-    return this.bwd0(chunk, chunk ? chunk.span - 1 : 0);
+  /**
+   * Returns a backward iterator through visible text, one character at a time,
+   * starting from a given {@link Point}.
+   *
+   * @param start The starting point.
+   * @param chunk Chunk to start from.
+   * @returns The previous visible character iterator.
+   */
+  public bwd(start: Point<T>): CharIterator<T> {
+    return this.walk(start, -1);
   }
 
   /**
@@ -238,10 +193,7 @@ export class Editor<T = string> {
     predicate: CharPredicate<string> = isLetter,
     firstLetterFound: boolean = false,
   ): Point<T> {
-    const firstChar = point.rightChar();
-    if (!firstChar) return point;
-    const fwd = this.fwd1(firstChar.id(), firstChar.chunk);
-    return this.skipWord(fwd, predicate, firstLetterFound) || point;
+    return this.skipWord(this.fwd(point), predicate, firstLetterFound) || point;
   }
 
   /**
@@ -260,9 +212,7 @@ export class Editor<T = string> {
     predicate: CharPredicate<string> = isLetter,
     firstLetterFound: boolean = false,
   ): Point<T> {
-    const firstChar = point.leftChar();
-    if (!firstChar) return point;
-    const bwd = this.bwd1(firstChar.id(), firstChar.chunk);
+    const bwd = this.bwd(point);
     const endPoint = this.skipWord(bwd, predicate, firstLetterFound);
     if (endPoint) endPoint.anchor = Anchor.Before;
     return endPoint || point;

src/json-crdt-extensions/peritext/editor/__tests__/Editor-iterators.spec.ts

@@ -31,7 +31,7 @@ const setup = (
 describe('.fwd1()', () => {
   test('can use string root as initial point', () => {
     const {peritext, editor} = setup();
-    const iterator = editor.fwd1(peritext.str.id);
+    const iterator = editor.fwd(peritext.pointAbsStart());
     let str = '';
     while (1) {
       const res = iterator();
@@ -44,7 +44,7 @@ describe('.fwd1()', () => {
   test('can iterate through the entire string', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointStart()!;
-    const iterator = editor.fwd1(start.id);
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -57,7 +57,7 @@ describe('.fwd1()', () => {
   test('can iterate through the entire string, starting from ABS start', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointAbsStart()!;
-    const iterator = editor.fwd1(start.id);
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -70,7 +70,7 @@ describe('.fwd1()', () => {
   test('can iterate through the entire string, with initial chunk provided', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointStart()!;
-    const iterator = editor.fwd1(start.id, start.chunk());
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -83,7 +83,7 @@ describe('.fwd1()', () => {
   test('can iterate starting in the middle of first chunk', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointAt(2);
-    const iterator = editor.fwd1(start.id);
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -96,7 +96,7 @@ describe('.fwd1()', () => {
   test('can iterate starting in the middle of first chunk, with initial chunk provided', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointAt(2);
-    const iterator = editor.fwd1(start.id, start.chunk());
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -109,7 +109,7 @@ describe('.fwd1()', () => {
   test('can iterate starting in the middle of second chunk', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointAt(6);
-    const iterator = editor.fwd1(start.id);
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -122,7 +122,7 @@ describe('.fwd1()', () => {
   test('can iterate starting in the middle of second chunk, with initial chunk provided', () => {
     const {peritext, editor} = setup();
     const start = peritext.pointAt(6);
-    const iterator = editor.fwd1(start.id, start.chunk());
+    const iterator = editor.fwd(start);
     let str = '';
     while (1) {
       const res = iterator();
@@ -140,7 +140,7 @@ describe('.fwd1()', () => {
     });
     peritext.overlay.refresh();
     const start = peritext.pointAt(0);
-    const iterator = editor.fwd1(start.id, start.chunk());
+    const iterator = editor.fwd(start);
     let str = '';
     const bools: boolean[] = [];
     while (1) {
@@ -157,7 +157,7 @@ describe('.fwd1()', () => {
 describe('.bwd1()', () => {
   test('can use string root as initial point', () => {
     const {peritext, editor} = setup();
-    const iterator = editor.bwd1(peritext.str.id);
+    const iterator = editor.bwd(peritext.pointAbsEnd());
     let str = '';
     while (1) {
       const res = iterator();
@@ -170,7 +170,7 @@ describe('.bwd1()', () => {
   test('can iterate through the entire string', () => {
     const {peritext, editor} = setup();
     const end = peritext.pointEnd()!;
-    const iterator = editor.bwd1(end.id);
+    const iterator = editor.bwd(end);
     let str = '';
     while (1) {
       const res = iterator();
@@ -183,7 +183,7 @@ describe('.bwd1()', () => {
   test('can iterate through the entire string, starting from ABS end', () => {
     const {peritext, editor} = setup();
     const end = peritext.pointAbsEnd()!;
-    const iterator = editor.bwd1(end.id);
+    const iterator = editor.bwd(end);
     let str = '';
     while (1) {
       const res = iterator();
@@ -196,7 +196,7 @@ describe('.bwd1()', () => {
   test('can iterate through the entire string, with initial chunk provided', () => {
     const {peritext, editor} = setup();
     const end = peritext.pointEnd()!;
-    const iterator = editor.bwd1(end.id, end.chunk());
+    const iterator = editor.bwd(end);
     let str = '';
     while (1) {
       const res = iterator();
@@ -208,54 +208,54 @@ describe('.bwd1()', () => {
 
   test('can iterate starting in the middle of first chunk', () => {
     const {peritext, editor} = setup();
-    const end = peritext.pointAt(2);
-    const iterator = editor.bwd1(end.id);
+    const point = peritext.pointAt(2);
+    const iterator = editor.bwd(point);
     let str = '';
     while (1) {
       const res = iterator();
       if (!res) break;
       str += res.view();
     }
-    expect(str).toBe('210');
+    expect(str).toBe('10');
   });
 
   test('can iterate starting in the middle of first chunk, with initial chunk provided', () => {
     const {peritext, editor} = setup();
-    const end = peritext.pointAt(2);
-    const iterator = editor.bwd1(end.id, end.chunk());
+    const point = peritext.pointAt(2);
+    const iterator = editor.bwd(point);
     let str = '';
     while (1) {
       const res = iterator();
       if (!res) break;
       str += res.view();
     }
-    expect(str).toBe('210');
+    expect(str).toBe('10');
   });
 
   test('can iterate starting in the middle of second chunk', () => {
     const {peritext, editor} = setup();
-    const end = peritext.pointAt(6);
-    const iterator = editor.bwd1(end.id);
+    const point = peritext.pointAt(6);
+    const iterator = editor.bwd(point);
     let str = '';
     while (1) {
       const res = iterator();
       if (!res) break;
       str += res.view();
     }
-    expect(str).toBe('6543210');
+    expect(str).toBe('543210');
   });
 
   test('can iterate starting in the middle of second chunk, with initial chunk provided', () => {
     const {peritext, editor} = setup();
-    const end = peritext.pointAt(6);
-    const iterator = editor.bwd1(end.id, end.chunk());
+    const point = peritext.pointAt(6);
+    const iterator = editor.bwd(point);
     let str = '';
     while (1) {
       const res = iterator();
       if (!res) break;
       str += res.view();
     }
-    expect(str).toBe('6543210');
+    expect(str).toBe('543210');
   });
 
   test('returns true for block split chars', () => {
@@ -266,7 +266,7 @@ describe('.bwd1()', () => {
     });
     peritext.overlay.refresh();
     const start = peritext.pointAt(3);
-    const iterator = editor.bwd1(start.id, start.chunk());
+    const iterator = editor.bwd(start);
     let str = '';
     const bools: boolean[] = [];
     while (1) {