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Changeset: Use a generator to implement `SmartOpAssembler` 

Eventually all uses of the class will be switched to the generator.
rhansen-changeset
Richard Hansen 2021-10-11 04:10:28 -04:00
parent 2448fb8e41
commit 23e7809b4a
1 changed files with 71 additions and 44 deletions
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115
src/static/js/Changeset.js
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@ -420,6 +420,63 @@ class MergingOpAssembler {
}
}
/**
* Canonicalizes a sequence of operations. Specifically:
* - Skips no-op changes.
* - Reorders consecutive '-' and '+' operations.
* - Combines consecutive operations when possible.
*
* @param {Iterable<Op>} ops - Iterable of operations to combine.
* @param {boolean} finalize - If truthy, omits the final op if it is an attributeless keep op.
* @yields {Op} The canonicalized operations.
* @returns {Generator<Op, number>} The done value indicates how much the sequence of operations
* changes the length of the document (in characters).
*/
const canonicalizeOps = function* (ops, finalize) {
let minusOps = [];
let plusOps = [];
let keepOps = [];
let prevOpcode = '';
let lengthChange = 0;
const flushPlusMinus = function* () {
yield* exports.squashOps(minusOps, false);
minusOps = [];
yield* exports.squashOps(plusOps, false);
plusOps = [];
};
const flushKeeps = function* (finalize) {
yield* exports.squashOps(keepOps, finalize);
keepOps = [];
};
for (const op of ops) {
if (!op.opcode || !op.chars) continue;
switch (op.opcode) {
case '-':
if (prevOpcode === '=') yield* flushKeeps(false);
minusOps.push(op);
lengthChange -= op.chars;
break;
case '+':
if (prevOpcode === '=') yield* flushKeeps(false);
plusOps.push(op);
lengthChange += op.chars;
break;
case '=':
if (prevOpcode !== '=') yield* flushPlusMinus();
keepOps.push(op);
break;
}
prevOpcode = op.opcode;
}
yield* flushPlusMinus();
yield* flushKeeps(finalize);
return lengthChange;
};
/**
* Generates operations from the given text and attributes.
*
@ -465,54 +522,25 @@ const opsFromText = function* (opcode, text, attribs = '', pool = null) {
*/
class SmartOpAssembler {
constructor() {
this._assem = exports.stringAssembler();
this.clear();
}
clear() {
this._minusAssem = [];
this._plusAssem = [];
this._keepAssem = [];
this._assem.clear();
this._lastOpcode = '';
this._lengthChange = 0;
this._ops = [];
this._serialized = null;
this._lengthChange = null;
}
_flushKeeps(finalize) {
this._assem.append(exports.serializeOps(exports.squashOps(this._keepAssem, finalize)));
this._keepAssem = [];
}
_flushPlusMinus() {
this._assem.append(exports.serializeOps(exports.squashOps(this._minusAssem, false)));
this._minusAssem = [];
this._assem.append(exports.serializeOps(exports.squashOps(this._plusAssem, false)));
this._plusAssem = [];
_serialize(finalize) {
this._serialized = exports.serializeOps((function* () {
this._lengthChange = yield* canonicalizeOps(this._ops, finalize);
}).call(this));
}
append(op) {
if (!op.opcode) return;
if (!op.chars) return;
if (op.opcode === '-') {
if (this._lastOpcode === '=') {
this._flushKeeps(false);
}
this._minusAssem.push(copyOp(op));
this._lengthChange -= op.chars;
} else if (op.opcode === '+') {
if (this._lastOpcode === '=') {
this._flushKeeps(false);
}
this._plusAssem.push(copyOp(op));
this._lengthChange += op.chars;
} else if (op.opcode === '=') {
if (this._lastOpcode !== '=') {
this._flushPlusMinus();
}
this._keepAssem.push(copyOp(op));
}
this._lastOpcode = op.opcode;
this._serialized = null;
this._lengthChange = null;
this._ops.push(copyOp(op));
}
/**
@ -533,17 +561,16 @@ class SmartOpAssembler {
}
toString() {
this._flushPlusMinus();
this._flushKeeps(false);
return this._assem.toString();
if (this._serialized == null) this._serialize(false);
return this._serialized;
}
endDocument() {
this._flushPlusMinus();
this._flushKeeps(true);
this._serialize(true);
}
getLengthChange() {
if (this._lengthChange == null) this._serialize(false);
return this._lengthChange;
}
}