json-joy
Version:
Collection of libraries for building collaborative editing apps.
73 lines (72 loc) • 2.35 kB
JavaScript
export const append = (op, component) => {
if (!component)
return;
if (!op.length) {
op.push(component);
return;
}
const lastIndex = op.length - 1;
const last = op[lastIndex];
if (typeof component === 'number') {
if (typeof last === 'number') {
if (component > 0 && last > 0)
op[lastIndex] = last + component;
else if (component < 0 && last < 0)
op[lastIndex] = last + component;
else
op.push(component);
}
else
op.push(component);
}
else if (component instanceof Uint8Array) {
if (last instanceof Uint8Array) {
const combined = new Uint8Array(last.length + component.length);
combined.set(last, 0);
combined.set(component, last.length);
op[lastIndex] = combined;
}
else
op.push(component);
}
};
export const componentLength = (component) => {
return typeof component === 'number' ? Math.abs(component) : component.length;
};
export const isDeleteComponent = (component) => {
return typeof component === 'number' && component < 0;
};
export const trim = (op) => {
if (!op.length)
return;
const last = op[op.length - 1];
const isLastRetain = typeof last === 'number' && last > 0;
if (isLastRetain)
op.pop();
};
export const normalize = (op) => {
const op2 = [];
const length = op.length;
for (let i = 0; i < length; i++)
append(op2, op[i]);
trim(op2);
return op2;
};
/**
* Extracts a full or a part of a component from an operation.
*
* @param component Component from which to extract a chunk.
* @param offset Position within the component to start from.
* @param maxLength Maximum length of the component to extract.
* @returns Full or partial component at index `index` of operation `op`.
*/
export const chunk = (component, offset, maxLength) => {
if (typeof component === 'number') {
return component > 0 ? Math.min(component - offset, maxLength) : -Math.min(-component - offset, maxLength);
}
else if (component instanceof Uint8Array) {
const end = Math.min(offset + maxLength, component.length);
return component.subarray(offset, end);
}
return component;
};