import { CalendarEventParsed, CalendarEventVisual, CalendarTimestamp } from 'vuetify/types'
import { getTimestampIdentifier } from '../util/timestamp'

const MILLIS_IN_DAY = 86400000

export type GetRange = (event: CalendarEventParsed) => [number, number]

export function getVisuals (events: CalendarEventParsed[], minStart = 0): CalendarEventVisual[] {
  const visuals = events.map(event => ({
    event,
    columnCount: 0,
    column: 0,
    left: 0,
    width: 100,
  }))

  visuals.sort((a, b) => {
    return (Math.max(minStart, a.event.startTimestampIdentifier) - Math.max(minStart, b.event.startTimestampIdentifier)) ||
           (b.event.endTimestampIdentifier - a.event.endTimestampIdentifier)
  })

  return visuals
}

export interface ColumnGroup {
  start: number
  end: number
  visuals: CalendarEventVisual[]
}

export function hasOverlap (s0: number, e0: number, s1: number, e1: number, exclude = true): boolean {
  return exclude ? !(s0 >= e1 || e0 <= s1) : !(s0 > e1 || e0 < s1)
}

export function setColumnCount (groups: ColumnGroup[]) {
  groups.forEach(group => {
    group.visuals.forEach(groupVisual => {
      groupVisual.columnCount = groups.length
    })
  })
}

export function getRange (event: CalendarEventParsed): [number, number] {
  return [event.startTimestampIdentifier, event.endTimestampIdentifier]
}

export function getDayRange (event: CalendarEventParsed): [number, number] {
  return [event.startIdentifier, event.endIdentifier]
}

export function getNormalizedRange (event: CalendarEventParsed, dayStart: number): [number, number] {
  return [Math.max(dayStart, event.startTimestampIdentifier), Math.min(dayStart + MILLIS_IN_DAY, event.endTimestampIdentifier)]
}

export function getOpenGroup (groups: ColumnGroup[], start: number, end: number, timed: boolean) {
  for (let i = 0; i < groups.length; i++) {
    const group = groups[i]
    let intersected = false

    if (hasOverlap(start, end, group.start, group.end, timed)) {
      for (let k = 0; k < group.visuals.length; k++) {
        const groupVisual = group.visuals[k]
        const [groupStart, groupEnd] = timed ? getRange(groupVisual.event) : getDayRange(groupVisual.event)

        if (hasOverlap(start, end, groupStart, groupEnd, timed)) {
          intersected = true
          break
        }
      }
    }

    if (!intersected) {
      return i
    }
  }

  return -1
}

export function getOverlapGroupHandler (firstWeekday: number) {
  const handler = {
    groups: [] as ColumnGroup[],
    min: -1,
    max: -1,
    reset: () => {
      handler.groups = []
      handler.min = handler.max = -1
    },
    getVisuals: (day: CalendarTimestamp, dayEvents: CalendarEventParsed[], timed: boolean, reset = false) => {
      if (day.weekday === firstWeekday || reset) {
        handler.reset()
      }

      const dayStart = getTimestampIdentifier(day)
      const visuals = getVisuals(dayEvents, dayStart)

      visuals.forEach(visual => {
        const [start, end] = timed ? getRange(visual.event) : getDayRange(visual.event)

        if (handler.groups.length > 0 && !hasOverlap(start, end, handler.min, handler.max, timed)) {
          setColumnCount(handler.groups)
          handler.reset()
        }

        let targetGroup = getOpenGroup(handler.groups, start, end, timed)

        if (targetGroup === -1) {
          targetGroup = handler.groups.length

          handler.groups.push({ start, end, visuals: [] })
        }

        const target = handler.groups[targetGroup]
        target.visuals.push(visual)
        target.start = Math.min(target.start, start)
        target.end = Math.max(target.end, end)

        visual.column = targetGroup

        if (handler.min === -1) {
          handler.min = start
          handler.max = end
        } else {
          handler.min = Math.min(handler.min, start)
          handler.max = Math.max(handler.max, end)
        }
      })

      setColumnCount(handler.groups)

      if (timed) {
        handler.reset()
      }

      return visuals
    },
  }

  return handler
}