function nonEmptyLines(content: string): string[] {
	return content.split(/\r\n|\r|\n/).filter(Boolean)
}

function overlapLength(history: readonly string[], liveBuffer: readonly string[]): number {
	const maximum = Math.min(history.length, liveBuffer.length)

	for (let length = maximum; length > 0; length--) {
		let overlaps = true
		for (let index = 0; index < length; index++) {
			if (history[history.length - length + index] !== liveBuffer[index]) {
				overlaps = false
				break
			}
		}
		if (overlaps) return length
	}

	return 0
}

/**
 * Combines the persisted Minecraft log with output that may not have reached
 * latest.log yet. The ring buffer commonly repeats the tail of latest.log, so
 * retain only its non-overlapping suffix.
 */
export function mergeLiveLogHistory(latestLog: string, liveBuffer: string): string {
	const history = nonEmptyLines(latestLog)
	const buffer = nonEmptyLines(liveBuffer)
	return [...history, ...buffer.slice(overlapLength(history, buffer))].join('\n')
}