public handleKeydown()

in packages/web-components/fast-foundation/src/data-grid/data-grid.ts [383:490]
88 lines of code
22 McCabe index (conditional complexity)

    public handleKeydown(e: KeyboardEvent): void {
        if (e.defaultPrevented) {
            return;
        }

        let newFocusRowIndex: number;
        const maxIndex = this.rowElements.length - 1;
        const currentGridBottom: number = this.offsetHeight + this.scrollTop;
        const lastRow: HTMLElement = this.rowElements[maxIndex] as HTMLElement;

        switch (e.key) {
            case keyArrowUp:
                e.preventDefault();
                // focus up one row
                this.focusOnCell(this.focusRowIndex - 1, this.focusColumnIndex, true);
                break;

            case keyArrowDown:
                e.preventDefault();
                // focus down one row
                this.focusOnCell(this.focusRowIndex + 1, this.focusColumnIndex, true);
                break;

            case keyPageUp:
                e.preventDefault();
                if (this.rowElements.length === 0) {
                    this.focusOnCell(0, 0, false);
                    break;
                }
                if (this.focusRowIndex === 0) {
                    this.focusOnCell(0, this.focusColumnIndex, false);
                    return;
                }

                newFocusRowIndex = this.focusRowIndex - 1;

                for (newFocusRowIndex; newFocusRowIndex >= 0; newFocusRowIndex--) {
                    const thisRow: HTMLElement = this.rowElements[newFocusRowIndex];
                    if (thisRow.offsetTop < this.scrollTop) {
                        this.scrollTop =
                            thisRow.offsetTop + thisRow.clientHeight - this.clientHeight;
                        break;
                    }
                }

                this.focusOnCell(newFocusRowIndex, this.focusColumnIndex, false);
                break;

            case keyPageDown:
                e.preventDefault();
                if (this.rowElements.length === 0) {
                    this.focusOnCell(0, 0, false);
                    break;
                }

                // focus down one "page"
                if (
                    this.focusRowIndex >= maxIndex ||
                    lastRow.offsetTop + lastRow.offsetHeight <= currentGridBottom
                ) {
                    this.focusOnCell(maxIndex, this.focusColumnIndex, false);
                    return;
                }

                newFocusRowIndex = this.focusRowIndex + 1;

                for (newFocusRowIndex; newFocusRowIndex <= maxIndex; newFocusRowIndex++) {
                    const thisRow: HTMLElement = this.rowElements[
                        newFocusRowIndex
                    ] as HTMLElement;
                    if (thisRow.offsetTop + thisRow.offsetHeight > currentGridBottom) {
                        let stickyHeaderOffset: number = 0;
                        if (
                            this.generateHeader === GenerateHeaderOptions.sticky &&
                            this.generatedHeader !== null
                        ) {
                            stickyHeaderOffset = this.generatedHeader.clientHeight;
                        }
                        this.scrollTop = thisRow.offsetTop - stickyHeaderOffset;
                        break;
                    }
                }

                this.focusOnCell(newFocusRowIndex, this.focusColumnIndex, false);

                break;

            case keyHome:
                if (e.ctrlKey) {
                    e.preventDefault();
                    // focus first cell of first row
                    this.focusOnCell(0, 0, true);
                }
                break;

            case keyEnd:
                if (e.ctrlKey && this.columnDefinitions !== null) {
                    e.preventDefault();
                    // focus last cell of last row
                    this.focusOnCell(
                        this.rowElements.length - 1,
                        this.columnDefinitions.length - 1,
                        true
                    );
                }
                break;
        }
    }