import { addClass, elt, rmClass } from "../util/dom"
import { on } from "../util/event"
import { scrollGap, paddingVert } from "../measurement/position_measurement"
import { ie, ie_version, mac, mac_geMountainLion } from "../util/browser"
import { updateHeightsInViewport } from "./update_lines"
import { Delayed } from "../util/misc"

import { setScrollLeft, setScrollTop } from "./scroll_events"

// SCROLLBARS

// Prepare DOM reads needed to update the scrollbars. Done in one
// shot to minimize update/measure roundtrips.
export function measureForScrollbars(cm) {
  let d = cm.display, gutterW = d.gutters.offsetWidth
  let docH = Math.round(cm.doc.height + paddingVert(cm.display))
  return {
    clientHeight: d.scroller.clientHeight,
    viewHeight: d.wrapper.clientHeight,
    scrollWidth: d.scroller.scrollWidth, clientWidth: d.scroller.clientWidth,
    viewWidth: d.wrapper.clientWidth,
    barLeft: cm.options.fixedGutter ? gutterW : 0,
    docHeight: docH,
    scrollHeight: docH + scrollGap(cm) + d.barHeight,
    nativeBarWidth: d.nativeBarWidth,
    gutterWidth: gutterW
  }
}

class NativeScrollbars {
  constructor(place, scroll, cm) {
    this.cm = cm
    let vert = this.vert = elt("div", [elt("div", null, null, "min-width: 1px")], "CodeMirror-vscrollbar")
    let horiz = this.horiz = elt("div", [elt("div", null, null, "height: 100%; min-height: 1px")], "CodeMirror-hscrollbar")
    place(vert); place(horiz)

    on(vert, "scroll", () => {
      if (vert.clientHeight) scroll(vert.scrollTop, "vertical")
    })
    on(horiz, "scroll", () => {
      if (horiz.clientWidth) scroll(horiz.scrollLeft, "horizontal")
    })

    this.checkedZeroWidth = false
    // Need to set a minimum width to see the scrollbar on IE7 (but must not set it on IE8).
    if (ie && ie_version < 8) this.horiz.style.minHeight = this.vert.style.minWidth = "18px"
  }

  update(measure) {
    let needsH = measure.scrollWidth > measure.clientWidth + 1
    let needsV = measure.scrollHeight > measure.clientHeight + 1
    let sWidth = measure.nativeBarWidth

    if (needsV) {
      this.vert.style.display = "block"
      this.vert.style.bottom = needsH ? sWidth + "px" : "0"
      let totalHeight = measure.viewHeight - (needsH ? sWidth : 0)
      // A bug in IE8 can cause this value to be negative, so guard it.
      this.vert.firstChild.style.height =
        Math.max(0, measure.scrollHeight - measure.clientHeight + totalHeight) + "px"
    } else {
      this.vert.style.display = ""
      this.vert.firstChild.style.height = "0"
    }

    if (needsH) {
      this.horiz.style.display = "block"
      this.horiz.style.right = needsV ? sWidth + "px" : "0"
      this.horiz.style.left = measure.barLeft + "px"
      let totalWidth = measure.viewWidth - measure.barLeft - (needsV ? sWidth : 0)
      this.horiz.firstChild.style.width =
        (measure.scrollWidth - measure.clientWidth + totalWidth) + "px"
    } else {
      this.horiz.style.display = ""
      this.horiz.firstChild.style.width = "0"
    }

    if (!this.checkedZeroWidth && measure.clientHeight > 0) {
      if (sWidth == 0) this.zeroWidthHack()
      this.checkedZeroWidth = true
    }

    return {right: needsV ? sWidth : 0, bottom: needsH ? sWidth : 0}
  }

  setScrollLeft(pos) {
    if (this.horiz.scrollLeft != pos) this.horiz.scrollLeft = pos
    if (this.disableHoriz) this.enableZeroWidthBar(this.horiz, this.disableHoriz)
  }

  setScrollTop(pos) {
    if (this.vert.scrollTop != pos) this.vert.scrollTop = pos
    if (this.disableVert) this.enableZeroWidthBar(this.vert, this.disableVert)
  }

  zeroWidthHack() {
    let w = mac && !mac_geMountainLion ? "12px" : "18px"
    this.horiz.style.height = this.vert.style.width = w
    this.horiz.style.pointerEvents = this.vert.style.pointerEvents = "none"
    this.disableHoriz = new Delayed
    this.disableVert = new Delayed
  }

  enableZeroWidthBar(bar, delay) {
    bar.style.pointerEvents = "auto"
    function maybeDisable() {
      // To find out whether the scrollbar is still visible, we
      // check whether the element under the pixel in the bottom
      // left corner of the scrollbar box is the scrollbar box
      // itself (when the bar is still visible) or its filler child
      // (when the bar is hidden). If it is still visible, we keep
      // it enabled, if it's hidden, we disable pointer events.
      let box = bar.getBoundingClientRect()
      let elt = document.elementFromPoint(box.left + 1, box.bottom - 1)
      if (elt != bar) bar.style.pointerEvents = "none"
      else delay.set(1000, maybeDisable)
    }
    delay.set(1000, maybeDisable)
  }

  clear() {
    let parent = this.horiz.parentNode
    parent.removeChild(this.horiz)
    parent.removeChild(this.vert)
  }
}

class NullScrollbars {
  update() { return {bottom: 0, right: 0} }
  setScrollLeft() {}
  setScrollTop() {}
  clear() {}
}

export function updateScrollbars(cm, measure) {
  if (!measure) measure = measureForScrollbars(cm)
  let startWidth = cm.display.barWidth, startHeight = cm.display.barHeight
  updateScrollbarsInner(cm, measure)
  for (let i = 0; i < 4 && startWidth != cm.display.barWidth || startHeight != cm.display.barHeight; i++) {
    if (startWidth != cm.display.barWidth && cm.options.lineWrapping)
      updateHeightsInViewport(cm)
    updateScrollbarsInner(cm, measureForScrollbars(cm))
    startWidth = cm.display.barWidth; startHeight = cm.display.barHeight
  }
}

// Re-synchronize the fake scrollbars with the actual size of the
// content.
function updateScrollbarsInner(cm, measure) {
  let d = cm.display
  let sizes = d.scrollbars.update(measure)

  d.sizer.style.paddingRight = (d.barWidth = sizes.right) + "px"
  d.sizer.style.paddingBottom = (d.barHeight = sizes.bottom) + "px"
  d.heightForcer.style.borderBottom = sizes.bottom + "px solid transparent"

  if (sizes.right && sizes.bottom) {
    d.scrollbarFiller.style.display = "block"
    d.scrollbarFiller.style.height = sizes.bottom + "px"
    d.scrollbarFiller.style.width = sizes.right + "px"
  } else d.scrollbarFiller.style.display = ""
  if (sizes.bottom && cm.options.coverGutterNextToScrollbar && cm.options.fixedGutter) {
    d.gutterFiller.style.display = "block"
    d.gutterFiller.style.height = sizes.bottom + "px"
    d.gutterFiller.style.width = measure.gutterWidth + "px"
  } else d.gutterFiller.style.display = ""
}

export let scrollbarModel = {"native": NativeScrollbars, "null": NullScrollbars}

export function initScrollbars(cm) {
  if (cm.display.scrollbars) {
    cm.display.scrollbars.clear()
    if (cm.display.scrollbars.addClass)
      rmClass(cm.display.wrapper, cm.display.scrollbars.addClass)
  }

  cm.display.scrollbars = new scrollbarModel[cm.options.scrollbarStyle](node => {
    cm.display.wrapper.insertBefore(node, cm.display.scrollbarFiller)
    // Prevent clicks in the scrollbars from killing focus
    on(node, "mousedown", () => {
      if (cm.state.focused) setTimeout(() => cm.display.input.focus(), 0)
    })
    node.setAttribute("cm-not-content", "true")
  }, (pos, axis) => {
    if (axis == "horizontal") setScrollLeft(cm, pos)
    else setScrollTop(cm, pos)
  }, cm)
  if (cm.display.scrollbars.addClass)
    addClass(cm.display.wrapper, cm.display.scrollbars.addClass)
}
