monocart-coverage-reports/lib/utils/merge/range-tree.js

A code coverage tool to generate native V8 reports or Istanbul reports.

class RangeTree {

    constructor(
        start,
        end,
        delta,
        children
    ) {
        this.start = start;
        this.end = end;
        this.delta = delta;
        this.children = children;
    }

    // eslint-disable-next-line complexity
    normalize() {
        const children = [];
        let curEnd;
        let head;
        const tail = [];
        for (const child of this.children) {
            if (!head) {
                head = child;
            } else if (child.delta === head.delta && child.start === curEnd) {
                tail.push(child);
            } else {
                endChain();
                head = child;
            }
            curEnd = child.end;
        }
        if (head) {
            endChain();
        }

        if (children.length === 1) {
            const child = children[0];
            if (child.start === this.start && child.end === this.end) {
                this.delta += child.delta;
                this.children = child.children;
                // `.lazyCount` is zero for both (both are after normalization)
                return;
            }
        }

        this.children = children;

        function endChain() {
            if (tail.length !== 0) {
                head.end = tail[tail.length - 1].end;
                for (const tailTree of tail) {
                    for (const subChild of tailTree.children) {
                        subChild.delta += tailTree.delta - head.delta;
                        head.children.push(subChild);
                    }
                }
                tail.length = 0;
            }
            head.normalize();
            children.push(head);
        }
    }

    /**
     * @precondition `tree.start < value && value < tree.end`
     * @return RangeTree Right part
     */
    split(value) {
        let leftChildLen = this.children.length;
        let mid;

        // TODO(perf): Binary search (check overhead)
        for (let i = 0; i < this.children.length; i++) {
            const child = this.children[i];
            if (child.start < value && value < child.end) {
                mid = child.split(value);
                leftChildLen = i + 1;
                break;
            } else if (child.start >= value) {
                leftChildLen = i;
                break;
            }
        }

        const rightLen = this.children.length - leftChildLen;
        const rightChildren = this.children.splice(leftChildLen, rightLen);
        if (mid) {
            rightChildren.unshift(mid);
        }
        const result = new RangeTree(
            value,
            this.end,
            this.delta,
            rightChildren
        );
        this.end = value;
        return result;
    }

    /**
     * Get the range coverages corresponding to the tree.
     *
     * The ranges are pre-order sorted.
     */
    toRanges() {
        const ranges = [];
        // Stack of parent trees and counts.
        const stack = [[this, 0]];
        while (stack.length > 0) {
            const [cur, parentCount] = stack.pop();
            const count = parentCount + cur.delta;
            ranges.push({
                startOffset: cur.start, endOffset: cur.end, count
            });
            for (let i = cur.children.length - 1; i >= 0; i--) {
                stack.push([cur.children[i], count]);
            }
        }
        return ranges;
    }
}

module.exports = RangeTree;