orario/src/interval-layout.js

/**
 * Returns a compact layout of a list of intervals
 *
 * Second options parameter
 * - `tight` places an interval with same ending as previous next to each other.
 */
export function layoutIntervals(intervals, { tight } = {}) {
    tight ??= true

    const canPlaceInterval = tight
        ? ({ start }, place) => place <= start
        : ({ start }, place) => place < start

    if (intervals.length === 0) {
        return []
    }

    // sort intervals by ".start"
    intervals.sort((a, b) => a.start - b.start)

    const stack = [{ lastEnd: -Infinity, intervals: [] }]

    for (const interval of intervals) {
        const s = stack.find(level => canPlaceInterval(interval, level.lastEnd))

        if (s) {
            s.intervals.push(interval)
            s.lastEnd = Math.max(s.lastEnd, interval.end)
        } else {
            stack.push({ lastEnd: interval.end, intervals: [interval] })
        }
    }

    return stack.map(({ intervals }) => intervals)
}

function layoutBlockEvents(events) {
    events.sort((a, b) => a.start - b.start)

    let result = []
    for (const event of events) {
        let viableIndex = 0
        while (
            result.filter(
                e => e.index === viableIndex && e.start < event.end && event.start < e.end
            ).length !== 0
        ) {
            viableIndex += 1
        }

        result.push({ ...event, index: viableIndex })
    }

    return result
}
export function layoutEvents(events) {
    const overlap = (event, block) => event.start < block.end && block.start < event.end

    events.sort((a, b) => a.start - b.start)

    let layout = []
    for (const event of events) {
        const blocks = layout.filter(block => overlap(event, block))
        if (blocks.length > 0) {
            layout = layout.filter(block => !overlap(event, block))
            layout.push({
                start: Math.min(event.start, ...blocks.map(block => block.start)),
                end: Math.max(event.end, ...blocks.map(block => block.end)),
                events: blocks.flatMap(block => block.events).concat([event]),
            })
        } else {
            layout.push({ start: event.start, end: event.end, events: [event] })
        }
    }

    return layout.map(block => {
        const events = layoutBlockEvents(block.events)
        return {
            ...block,
            layers: Math.max(...events.map(event => event.index)) + 1,
            events: events,
        }
    })
}

// //
// // Testing...
// //

// console.dir(
//     layoutIntervals([
//         { start: 0, end: 2 },
//         { start: 2, end: 4 },
//         { start: 1, end: 3 },
//         { start: 4, end: 6 },
//         { start: 3, end: 5 },
//         { start: 2, end: 4 },
//     ]),
//     { depth: null }
// )