function mergeSplice()

in packages/web-components/fast-element/src/observation/array-change-records.ts [323:407]
64 lines of code
11 McCabe index (conditional complexity)

function mergeSplice(
    splices: Splice[],
    index: number,
    removed: any[],
    addedCount: number
): void {
    const splice = newSplice(index, removed, addedCount);
    let inserted = false;
    let insertionOffset = 0;

    for (let i = 0; i < splices.length; i++) {
        const current = splices[i];
        current.index += insertionOffset;

        if (inserted) {
            continue;
        }

        const intersectCount = intersect(
            splice.index,
            splice.index + splice.removed.length,
            current.index,
            current.index + current.addedCount
        );

        if (intersectCount >= 0) {
            // Merge the two splices

            splices.splice(i, 1);
            i--;

            insertionOffset -= current.addedCount - current.removed.length;

            splice.addedCount += current.addedCount - intersectCount;
            const deleteCount =
                splice.removed.length + current.removed.length - intersectCount;

            if (!splice.addedCount && !deleteCount) {
                // merged splice is a noop. discard.
                inserted = true;
            } else {
                let currentRemoved = current.removed;

                if (splice.index < current.index) {
                    // some prefix of splice.removed is prepended to current.removed.
                    const prepend = splice.removed.slice(0, current.index - splice.index);
                    $push.apply(prepend, currentRemoved);
                    currentRemoved = prepend;
                }

                if (
                    splice.index + splice.removed.length >
                    current.index + current.addedCount
                ) {
                    // some suffix of splice.removed is appended to current.removed.
                    const append = splice.removed.slice(
                        current.index + current.addedCount - splice.index
                    );
                    $push.apply(currentRemoved, append);
                }

                splice.removed = currentRemoved;

                if (current.index < splice.index) {
                    splice.index = current.index;
                }
            }
        } else if (splice.index < current.index) {
            // Insert splice here.

            inserted = true;

            splices.splice(i, 0, splice);
            i++;

            const offset = splice.addedCount - splice.removed.length;
            current.index += offset;
            insertionOffset += offset;
        }
    }

    if (!inserted) {
        splices.push(splice);
    }
}