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"use strict";
const Collapser = require("./collapser");
class ArrayPropertyCollapser extends Collapser {
isInitTypeValid(init) {
return init.isArrayExpression();
}
isExpressionTypeValid(expr) {
return expr.isAssignmentExpression();
}
getExpressionChecker(objName, checkReference) {
return expr => {
// checks expr is of form:
// foo[num] = rval
const left = expr.get("left");
if (!left.isMemberExpression()) {
return false;
}
const obj = left.get("object"),
prop = left.get("property");
if (!obj.isIdentifier() || obj.node.name !== objName) {
return false;
}
const checkIndex = num => Number.isInteger(num) && num >= 0;
if (!(prop.isNumericLiteral() || prop.isStringLiteral()) || !checkIndex(Number(prop.node.value))) {
return false;
}
const right = expr.get("right");
if (checkReference(right)) {
return false;
}
return true;
};
}
extractAssignment(expr) {
return [expr.node.left.property.value, expr.get("right")];
}
addSuccessfully(t, [index, rval], init) {
const elements = init.elements;
for (let i = elements.length; i <= index; i++) {
elements.push(null);
}
if (elements[index] !== null) {
return false;
}
elements[index] = rval.node;
return true;
}
isSizeSmaller({
newInit,
oldInit,
varDecl,
assignments,
statements
}) {
const anyUndefined = args => args.some(a => a === undefined); // We make an inexact calculation of how much space we save.
// It's inexact because we don't know how whitespaces will get minimized,
// and other factors.
if (anyUndefined([statements[statements.length - 1].node.end, varDecl.node.end])) {
return false;
}
const statementsLength = statements[statements.length - 1].node.end - varDecl.node.end; // Approx. formula of the change in `init`'s length =
// (# commas added) + (size of all the new rvals added), where
// # commas added = (difference between the lengths of the old and new arrays)
const numCommaAdded = newInit.elements.length - oldInit.elements.length;
if (anyUndefined(assignments.map(([, rval]) => rval.node.end)) || anyUndefined(assignments.map(([, rval]) => rval.node.start))) {
return false;
}
const sizeOfRvals = assignments.map(([, rval]) => rval.node.end - rval.node.start + 1).reduce((a, b) => a + b, 0); // add 1 for space in front // sum
return numCommaAdded + sizeOfRvals < statementsLength;
}
}
module.exports = ArrayPropertyCollapser;
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