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import {Anchor} from './constants';
import {ChunkSlice} from '../util/ChunkSlice';
import {hashId, updateId} from '../../../json-crdt/hash';
import {Position} from '../constants';
import type {AbstractRga, Chunk} from '../../../json-crdt/nodes/rga';
import type {Stateful} from '../types';
import type {Printable} from 'tree-dump/lib/types';
/**
* A "point" in a rich-text Peritext document. It is a combination of a
* character ID and an anchor. Anchor specifies the side of the character to
* which the point is attached. For example, a point with an anchor "before" .▢
* points just before the character, while a point with an anchor "after" ▢.
* points just after the character. Points attached to string characters are
* referred to as *relative* points, while points attached to the beginning or
* end of the string are referred to as *absolute* points.
*
* The *absolute* points are reference the string itself, by using the string's
* ID as the character ID. The *absolute (abs) start* references the very start
* of the string, before the first character, and even before any deleted
* characters. The *absolute (abs) end* references the very end of the string,
* after the last character, and even after any deleted characters at the end
* of the string.
*/
export class Point<T = string> implements Pick<Stateful, 'refresh'>, Printable {
constructor(
protected readonly rga: AbstractRga<T>,
public id: ITimestampStruct,
public anchor: Anchor,
) {}
/**
* Overwrites the internal state of this point with the state of the given
* point.
*
* @param point Point to copy.
*/
public set(point: Point<T>): void {
this.id = point.id;
this.anchor = point.anchor;
}
/**
* Creates a copy of this point.
*
* @returns Returns a new point with the same ID and anchor as this point.
*/
public clone(): Point<T> {
return new Point(this.rga, this.id, this.anchor);
}
public copy(mutate: (copy: Point<T>) => void): Point<T> {
const copy = this.clone();
mutate(copy);
return copy;
}
/**
* Compares two points by their character IDs and anchors. First, the character
* IDs are compared. If they are equal, the anchors are compared. The anchor
* "before" is considered less than the anchor "after".
*
* @param other The other point to compare to.
* @returns Returns 0 if the two points are equal, -1 if this point is less
* than the other point, and 1 if this point is greater than the other
* point.
*/
public cmp(other: Point<T>): -1 | 0 | 1 {
const cmp = compare(this.id, other.id);
if (cmp !== 0) return cmp;
return (this.anchor - other.anchor) as -1 | 0 | 1;
}
/**
* Compares two points by their spatial (view) location in the string. Takes
* into account not only the character position in the view, but also handles
* deleted characters, attachment anchors, and absolute points.
*
* @param other The other point to compare to.
* @returns Returns 0 if the two points are equal, negative if this point is
* less than the other point, and positive if this point is greater
* than the other point.
*/
public cmpSpatial(other: Point<T>): number {
const thisId = this.id;
const otherId = other.id;
if (this.isAbs()) {
const isStart = this.anchor === Anchor.After;
return isStart ? (other.isAbsStart() ? 0 : -1) : other.isAbsEnd() ? 0 : 1;
} else if (other.isAbs()) {
const isStart = other.anchor === Anchor.After;
return isStart ? (this.isAbsStart() ? 0 : 1) : this.isAbsEnd() ? 0 : -1;
}
const cmp0 = compare(thisId, otherId);
if (!cmp0) return this.anchor - other.anchor;
const cmp1 = this.pos() - other.pos();
if (cmp1) return cmp1;
let chunk = this.chunk();
Iif (!chunk) return cmp0;
if (containsId(chunk.id, chunk.span, otherId)) return thisId.time - otherId.time;
const rga = this.rga;
chunk = rga.next(chunk);
while (chunk) {
if (containsId(chunk.id, chunk.span, otherId)) return -1;
chunk = rga.next(chunk);
}
return 1;
}
private _chunk: Chunk<T> | undefined;
/**
* @returns Returns the chunk that contains the character referenced by the
* point, or `undefined` if the chunk is not found.
*/
public chunk(): Chunk<T> | undefined {
let chunk = this._chunk;
const id = this.id;
if (chunk) {
const chunkId = chunk.id;
const chunkIdTime = chunkId.time;
const idTime = id.time;
if (id.sid === chunkId.sid && idTime >= chunkIdTime && idTime < chunkIdTime + chunk.span) return chunk;
}
this._chunk = chunk = this.rga.findById(this.id);
return chunk;
}
/**
* @returns Returns position of the character referenced by the point.
*/
public pos(): number {
const chunk = this.chunk();
if (!chunk) return this.isAbsEnd() ? Position.AbsEnd : Position.AbsStart;
const pos = this.rga.pos(chunk);
if (chunk.del) return pos;
return pos + this.id.time - chunk.id.time;
}
/**
* @returns Returns the view position of the point, as if it is a caret in
* the text pointing between characters (0 is before the first
* character, 1 is after the first character, etc.).
*/
public viewPos(): number {
const pos = this.pos();
const isAbs = equal(this.rga.id, this.id);
if (isAbs) return this.anchor === Anchor.After ? 0 : this.rga.length();
return this.anchor === Anchor.Before ? pos : pos + 1;
}
/**
* @returns Returns `true` if the point is at the very start of the string, i.e.
* there are no visible characters before it.
*/
public isStart(): boolean {
const chunk = this.chunk();
Iif (!chunk) return true;
Iif (!chunk.del && chunk.id.time < this.id.time) return false;
const l = chunk.l;
return l ? !l.len : true;
}
/**
* Goes to the next visible character in the string. The `move` parameter
* specifies how many characters to move the cursor by. If the cursor reaches
* the end of the string, it will return `undefined`.
*
* @param skip How many characters to move by.
* @returns Next visible ID in string.
*/
public nextId(skip: number = 1): ITimestampStruct | undefined {
if (this.isAbsEnd()) return;
let remaining: number = skip;
const {id, rga} = this;
let chunk: Chunk<T> | undefined;
if (this.isAbsStart()) {
chunk = rga.first();
while (chunk && chunk.del) chunk = rga.next(chunk);
Iif (!chunk) return;
const span = chunk.span;
if (remaining <= span) return tick(chunk.id, remaining - 1);
remaining -= span;
chunk = rga.next(chunk);
} else {
chunk = this.chunk();
Iif (!chunk) return undefined;
if (!chunk.del) {
const offset = id.time - chunk.id.time;
const span = chunk.span;
if (offset + remaining < span) return tick(id, remaining);
else remaining -= span - offset - 1;
}
chunk = rga.next(chunk);
}
let lastVisibleChunk: Chunk<T> | undefined;
while (chunk && remaining >= 0) {
if (chunk.del) {
chunk = rga.next(chunk);
continue;
}
lastVisibleChunk = chunk;
const span = chunk.span;
if (remaining <= span) return remaining > 1 ? tick(chunk.id, remaining - 1) : chunk.id;
remaining -= span;
chunk = rga.next(chunk);
}
if (remaining > 0) return;
return lastVisibleChunk ? tick(lastVisibleChunk.id, lastVisibleChunk.span - 1) : undefined;
}
/**
* @returns ID of the character that is `move` characters before the
* character referenced by the point, or `undefined` if there is no
* such character.
*/
public prevId(skip: number = 1): ITimestampStruct | undefined {
if (this.isAbsStart()) return;
let remaining: number = skip;
const {id, rga} = this;
let chunk = this.chunk();
if (!chunk) return rga.id;
if (!chunk.del) {
const offset = id.time - chunk.id.time;
if (offset >= remaining) return tick(id, -remaining);
remaining -= offset;
}
chunk = rga.prev(chunk);
while (chunk) {
if (chunk.del) {
chunk = rga.prev(chunk);
continue;
}
const span = chunk.span;
if (remaining <= span) {
return tick(chunk.id, span - remaining);
}
remaining -= span;
chunk = rga.prev(chunk);
}
return;
}
/**
* Returns one character to the left of the point, or `undefined` if there
* is no such character. Skips any deleted characters. Handles absolute points.
*
* @returns A character slice to the left of the point.
*/
public leftChar(): ChunkSlice<T> | undefined {
const rga = this.rga;
if (this.isAbsEnd()) {
const res = rga.findChunk(rga.length() - 1);
Iif (!res) return;
return new ChunkSlice(res[0], res[1], 1);
}
const tmp = this.clone();
tmp.refAfter();
if (tmp.isAbsStart()) return;
const chunk = tmp.chunk();
Iif (!chunk || chunk.del) return;
const off = tmp.id.time - chunk.id.time;
return new ChunkSlice(chunk, off, 1);
}
/**
* Returns one character to the right of the point, or `undefined` if there
* is no such character. Skips any deleted characters. Handles absolute points.
*
* @returns A character slice to the right of the point.
*/
public rightChar(): ChunkSlice<T> | undefined {
const rga = this.rga;
if (this.isAbsStart()) {
const res = rga.findChunk(0);
Iif (!res) return;
return new ChunkSlice(res[0], res[1], 1);
}
const tmp = this.clone();
tmp.refBefore();
if (tmp.isAbsEnd()) return;
const chunk = tmp.chunk();
Iif (!chunk || chunk.del) return;
const off = tmp.id.time - chunk.id.time;
return new ChunkSlice(chunk, off, 1);
}
public char(): ChunkSlice<T> | undefined {
return this.anchor === Anchor.Before ? this.rightChar() : this.leftChar();
}
/**
* Checks if the point is an absolute point. An absolute point is a point that
* references the string itself, rather than a character in the string. It can
* be either the very start or the very end of the string.
*
* @returns Returns `true` if the point is an absolute point.
*/
public isAbs(): boolean {
return equal(this.id, this.rga.id);
}
/**
* @returns Returns `true` if the point is an absolute point and is anchored
* before the first character in the string.
*/
public isAbsStart(): boolean {
return this.isAbs() && this.anchor === Anchor.After;
}
/**
* @returns Returns `true` if the point is an absolute point and is anchored
* after the last character in the string.
*/
public isAbsEnd(): boolean {
return this.isAbs() && this.anchor === Anchor.Before;
}
/**
* @returns Returns `true` if the point is exactly the relative start, i.e.
* it is attached to the first visible character in the string and
* anchored "before".
*/
public isRelStart(): boolean {
if (this.anchor !== Anchor.Before) return false;
const id = this.rga.find(0);
return !!id && equal(this.id, id);
}
/**
* @returns Returns `true` if the point is exactly the relative end, i.e. it
* is attached to the last visible character in the string and
* anchored "after".
*/
public isRelEnd(): boolean {
if (this.anchor !== Anchor.After) return false;
const rga = this.rga;
const length = rga.length();
Iif (length === 0) return false;
const id = rga.find(length - 1);
return !!id && equal(this.id, id);
}
/**
* Sets the point to the absolute start of the string.
*/
public refAbsStart(): void {
this.id = this.rga.id;
this.anchor = Anchor.After;
}
/**
* Sets the point to the absolute end of the string.
*/
public refAbsEnd(): void {
this.id = this.rga.id;
this.anchor = Anchor.Before;
}
/**
* Sets the point to the relative start of the string.
*/
public refStart(): this {
this.refAbsStart();
this.refBefore();
return this;
}
/**
* Sets the point to the relative end of the string.
*/
public refEnd(): this {
this.refAbsEnd();
this.refAfter();
return this;
}
/**
* Modifies the location of the point, such that the view location remains
* the same, but ensures that it is anchored before a character. Skips any
* deleted characters (chunks), attaching the point to the next visible
* character.
*/
public refBefore(): void {
const chunk = this.chunk();
if (!chunk) {
if (this.isAbsStart()) {
const id = this.rga.find(0);
if (id) {
this.id = id;
this.anchor = Anchor.Before;
return;
}
}
this.refAbsEnd();
return;
}
if (!chunk.del && this.anchor === Anchor.Before) return;
this.anchor = Anchor.Before;
this.id = this.nextId() || this.rga.id;
}
/**
* Modifies the location of the point, such that the view location remains
* the same, but ensures that it is anchored after a character. Skips any
* deleted characters (chunks), attaching the point to the next visible
* character.
*/
public refAfter(): void {
const chunk = this.chunk();
if (!chunk) {
if (this.isAbsEnd()) {
const rga = this.rga;
const length = rga.length();
if (length !== 0) {
const id = rga.find(length - 1);
if (id) {
this.id = id;
this.anchor = Anchor.After;
return;
}
}
}
this.refAbsStart();
return;
}
if (!chunk.del && this.anchor === Anchor.After) return;
this.anchor = Anchor.After;
this.id = this.prevId() || this.rga.id;
}
/**
* Modifies the location of the point, such that the spatial location remains
* the same and tries to preserve anchor location, but ensures that the point
* references a visible (not deleted) character.
*/
public refVisible(): void {
if (this.anchor === Anchor.Before) this.refBefore();
else this.refAfter();
}
/**
* Moves point past given number of visible characters. Accepts positive
* and negative distances.
*
* @param length How many characters to move by. Positive number moves the
* point to the right, negative number moves the point to the left.
* @returns Returns `true` if the absolute end of the string is reached.
*/
public step(length: number): boolean {
if (!length) return this.isAbs();
const anchor = this.anchor;
if (anchor !== Anchor.After) this.refAfter();
if (length > 0) {
const nextId = this.nextId(length);
if (!nextId) {
this.refAbsEnd();
return true;
} else {
this.id = nextId;
if (anchor !== Anchor.After) this.refBefore();
}
} else {
const prevId = this.prevId(-length);
if (!prevId) {
this.refAbsStart();
return true;
} else {
this.id = prevId;
if (anchor !== Anchor.After) this.refBefore();
}
}
return false;
}
/**
* Moves the to the next point, which does not necessarily result in a visible
* character skip.
*
* @param length How many points to move by.
* @returns Returns `true` if the absolute end of the string is reached.
*/
public halfstep(length: number): boolean {
this.refVisible();
const isOdd = !!(length % 2);
if (isOdd) {
if (length > 0) {
length--;
if (this.anchor === Anchor.After) this.refBefore();
else if (this.isAbs()) return true;
else this.anchor = Anchor.After;
} else {
length++;
if (this.anchor === Anchor.Before) this.refAfter();
else if (this.isAbs()) return true;
else this.anchor = Anchor.Before;
}
}
return this.step(length / 2);
}
public key(): number {
return hashId(this.id) + (this.anchor ? 0 : 1);
}
// ----------------------------------------------------------------- Stateful
public refresh(): number {
return updateId(this.anchor, this.id);
}
// ---------------------------------------------------------------- Printable
public toStringName(): string {
return 'Point';
}
public toString(tab: string = '', lite?: boolean): string {
const name = lite ? '' : this.toStringName() + ' ';
const pos = this.pos();
const id = printTs(this.id);
let char: string | undefined = this.char()?.view() as string | undefined;
char = typeof char === 'string' ? JSON.stringify(char) : '▢';
const anchor = this.anchor === Anchor.Before ? '.' + char : char + '.';
return `${name}{ ${pos === Position.AbsEnd ? '∞' : pos}, ${id}, ${anchor} }`;
}
}
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