Method slice

src/SpannedString.ts:101–163

(
        startIndex: number,
        endIndex: number = this._string.length
    )

    }

    slice(
        startIndex: number,
        endIndex: number = this._string.length
    ): SpannedString<T> {
        if (startIndex < 0 || endIndex < 0) {
            throw new Error('Invalid start or end index');
        }
        if (startIndex > this._string.length) {
            startIndex = this._string.length;
        }
        if (endIndex > this._string.length) {
            endIndex = this._string.length;
        }

        let index = 0;
        const activeSpansById = new Map<number, Span<T>>();
        const updatedActiveSpans = () => {
            for (const span of this._spanMarkers[index] ?? []) {
                if (span.isStart) {
                    activeSpansById.set(span.id, span);
                } else {
                    activeSpansById.delete(span.id);
                }
            }
        };
        const getActiveSpans = () => {
            return [...activeSpansById.values()];
        };

        const newSpanMarkers: (Span<T>[] | undefined)[] = new Array(
            endIndex + 1 - startIndex
        );

        // Collect all the active spans before the new string starts
        while (index < startIndex) {
            updatedActiveSpans();
            index++;
        }
        newSpanMarkers[0] = getActiveSpans().map((span) => ({ ...span }));

        // Copy over spans active in the new string
        while (index < endIndex) {
            const spans = this._spanMarkers[index];
            updatedActiveSpans();
            if (spans) {
                const newIndex = index - startIndex;
                newSpanMarkers[newIndex] = newSpanMarkers[newIndex] ?? [];
                newSpanMarkers[newIndex]!.push(...spans);
            }
            index++;
        }

        // Close any spans that are still active at the end of the new string
        newSpanMarkers[endIndex - startIndex] = getActiveSpans().map(
            (span) => ({ ...span, isStart: false })
        );

        return new SpannedString<T>(