import { CalendarEventOverlapMode, CalendarEventVisual } from 'vuetify/types'
import { getOverlapGroupHandler, getVisuals, hasOverlap, getNormalizedRange } from './common'
import { getTimestampIdentifier } from '../util/timestamp'

interface Group {
  start: number
  end: number
  visuals: CalendarEventVisual[]
}

interface Node {
  parent: Node | null
  sibling: boolean
  index: number
  visual: CalendarEventVisual
  start: number
  end: number
  children: Node[]
}

const FULL_WIDTH = 100

const DEFAULT_OFFSET = 5

const WIDTH_MULTIPLIER = 1.7

/**
 * Variation of column mode where events can be stacked. The priority of this
 * mode is to stack events together taking up the least amount of space while
 * trying to ensure the content of the event is always visible as well as its
 * start and end. A sibling column has intersecting event content and must be
 * placed beside each other. Non-sibling columns are offset by 5% from the
 * previous column. The width is scaled by 1.7 so the events overlap and
 * whitespace is reduced. If there is a hole in columns the event width is
 * scaled up so it intersects with the next column. The columns have equal
 * width in the space they are given. If the event doesn't have any to the
 * right of it that intersect with it's content it's right side is extended
 * to the right side.
 */

export const stack: CalendarEventOverlapMode = (events, firstWeekday, overlapThreshold) => {
  const handler = getOverlapGroupHandler(firstWeekday)

  // eslint-disable-next-line max-statements
  return (day, dayEvents, timed, reset) => {
    if (!timed) {
      return handler.getVisuals(day, dayEvents, timed, reset)
    }

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

    for (const group of groups) {
      const nodes: Node[] = []

      for (const visual of group.visuals) {
        const child = getNode(visual, dayStart)
        const index = getNextIndex(child, nodes)

        if (index === false) {
          const parent = getParent(child, nodes)
          if (parent) {
            child.parent = parent
            child.sibling = hasOverlap(child.start, child.end, parent.start, addTime(parent.start, overlapThreshold))
            child.index = parent.index + 1
            parent.children.push(child)
          }
        } else {
          const [parent] = getOverlappingRange(child, nodes, index - 1, index - 1)
          const children = getOverlappingRange(child, nodes, index + 1, index + nodes.length, true)

          child.children = children
          child.index = index

          if (parent) {
            child.parent = parent
            child.sibling = hasOverlap(child.start, child.end, parent.start, addTime(parent.start, overlapThreshold))
            parent.children.push(child)
          }

          for (const grand of children) {
            if (grand.parent === parent) {
              grand.parent = child
            }

            const grandNext = grand.index - child.index <= 1
            if (grandNext && child.sibling &&
              hasOverlap(child.start, addTime(child.start, overlapThreshold), grand.start, grand.end)) {
              grand.sibling = true
            }
          }
        }

        nodes.push(child)
      }

      calculateBounds(nodes, overlapThreshold)
    }

    visuals.sort((a, b) => (a.left - b.left) || (a.event.startTimestampIdentifier - b.event.startTimestampIdentifier))

    return visuals
  }
}

function calculateBounds (nodes: Node[], overlapThreshold: number) {
  for (const node of nodes) {
    const { visual, parent } = node
    const columns = getMaxChildIndex(node) + 1
    const spaceLeft = parent ? parent.visual.left : 0
    const spaceWidth = FULL_WIDTH - spaceLeft
    const offset = Math.min(DEFAULT_OFFSET, FULL_WIDTH / columns)
    const columnWidthMultiplier = getColumnWidthMultiplier(node, nodes)
    const columnOffset = spaceWidth / (columns - node.index + 1)
    const columnWidth = spaceWidth / (columns - node.index + (node.sibling ? 1 : 0)) * columnWidthMultiplier

    if (parent) {
      visual.left = node.sibling
        ? spaceLeft + columnOffset
        : spaceLeft + offset
    }

    visual.width = hasFullWidth(node, nodes, overlapThreshold)
      ? FULL_WIDTH - visual.left
      : Math.min(FULL_WIDTH - visual.left, columnWidth * WIDTH_MULTIPLIER)
  }
}

function getColumnWidthMultiplier (node: Node, nodes: Node[]): number {
  if (!node.children.length) {
    return 1
  }

  const maxColumn = node.index + nodes.length
  const minColumn = node.children.reduce((min, c) => Math.min(min, c.index), maxColumn)

  return minColumn - node.index
}

function getOverlappingIndices (node: Node, nodes: Node[]): number[] {
  const indices: number[] = []
  for (const other of nodes) {
    if (hasOverlap(node.start, node.end, other.start, other.end)) {
      indices.push(other.index)
    }
  }
  return indices
}

function getNextIndex (node: Node, nodes: Node[]): number | false {
  const indices = getOverlappingIndices(node, nodes)
  indices.sort()

  for (let i = 0; i < indices.length; i++) {
    if (i < indices[i]) {
      return i
    }
  }
  return false
}

function getOverlappingRange (node: Node, nodes: Node[], indexMin: number, indexMax: number, returnFirstColumn = false): Node[] {
  const overlapping: Node[] = []
  for (const other of nodes) {
    if (other.index >= indexMin && other.index <= indexMax && hasOverlap(node.start, node.end, other.start, other.end)) {
      overlapping.push(other)
    }
  }
  if (returnFirstColumn && overlapping.length > 0) {
    const first = overlapping.reduce((min, n) => Math.min(min, n.index), overlapping[0].index)
    return overlapping.filter(n => n.index === first)
  }
  return overlapping
}

function getParent (node: Node, nodes: Node[]): Node | null {
  let parent: Node | null = null
  for (const other of nodes) {
    if (hasOverlap(node.start, node.end, other.start, other.end) && (parent === null || other.index > parent.index)) {
      parent = other
    }
  }
  return parent
}

function hasFullWidth (node: Node, nodes: Node[], overlapThreshold: number): boolean {
  for (const other of nodes) {
    if (other !== node &&
      other.index > node.index &&
      hasOverlap(node.start, addTime(node.start, overlapThreshold), other.start, other.end)) {
      return false
    }
  }

  return true
}

function getGroups (visuals: CalendarEventVisual[], dayStart: number): Group[] {
  const groups: Group[] = []

  for (const visual of visuals) {
    const [start, end] = getNormalizedRange(visual.event, dayStart)
    let added = false

    for (const group of groups) {
      if (hasOverlap(start, end, group.start, group.end)) {
        group.visuals.push(visual)
        group.end = Math.max(group.end, end)
        added = true
        break
      }
    }

    if (!added) {
      groups.push({ start, end, visuals: [visual] })
    }
  }

  return groups
}

function getNode (visual: CalendarEventVisual, dayStart: number): Node {
  const [start, end] = getNormalizedRange(visual.event, dayStart)

  return {
    parent: null,
    sibling: true,
    index: 0,
    visual,
    start,
    end,
    children: [],
  }
}

function getMaxChildIndex (node: Node): number {
  let max = node.index
  for (const child of node.children) {
    const childMax = getMaxChildIndex(child)
    if (childMax > max) {
      max = childMax
    }
  }
  return max
}

function addTime (identifier: number, minutes: number): number {
  const removeMinutes = identifier % 100
  const totalMinutes = removeMinutes + minutes
  const addHours = Math.floor(totalMinutes / 60)
  const addMinutes = totalMinutes % 60

  return identifier - removeMinutes + addHours * 100 + addMinutes
}