Method drop

packages/muya/src/editor/index.ts:253–355

(root: BlockNode, descent: JSONOpList)

        const snapshot = pick(this.scrollPage as BlockNode, operations);

        function drop(root: BlockNode, descent: JSONOpList): BlockNode {
            let subDoc = root;
            let i = 0; // For reading
            let m = 0;
            const rootContainer: { root: BlockNode } = { root }; // This is an avoidable allocation.
            let container: BlockNode | { root: BlockNode } = rootContainer;
            let key: string | number = 'root'; // For writing

            function mut() {
                for (; m < i; m++) {
                    const d = descent[m];
                    if (typeof d === 'object')
                        continue;
                    if (key === 'root') {
                        const wrap = container as { root: BlockNode };
                        container = wrap.root;
                    }
                    else {
                        container = (container as BlockNode)?.queryBlock?.([key]);
                    }
                    key = d as string | number;
                }
            }

            for (; i < descent.length; i++) {
                const d = descent[i];

                if (Array.isArray(d)) {
                    const child = drop(subDoc, d);
                    if (child !== subDoc && child !== undefined) {
                        mut();
                        // It maybe never go into this if statement.
                        if (key === 'root')
                            (container as { root: BlockNode }).root = child;
                        else
                            (container as Record<string, BlockNode>)[key] = child;
                        subDoc = child;
                    }
                }
                else if (typeof d === 'object') {
                    const comp = d as JSONOpComponent;
                    if (comp.i !== undefined) {
                        // Insert
                        mut();
                        const cur = container as BlockNode;
                        const ref = cur?.find?.(key);
                        if (typeof key === 'number') {
                            const insertedState = comp.i as { name: string };
                            const newBlock = ScrollPage.loadBlock(insertedState.name).create(muya, insertedState) as BlockNode;
                            if (cur && ref && newBlock)
                                cur.insertBefore?.(newBlock, ref, 'api');

                            subDoc = newBlock;
                        }
                        else {
                            switch (key) {
                                case 'checked': {
                                    ref?.update?.(comp.i, 'api');