import { sawCollapsedSpans } from "../line/saw_special_spans.js"
import { heightAtLine, visualLineEndNo, visualLineNo } from "../line/spans.js"
import { getLine, lineNumberFor } from "../line/utils_line.js"
import { displayHeight, displayWidth, getDimensions, paddingVert, scrollGap } from "../measurement/position_measurement.js"
import { mac, webkit } from "../util/browser.js"
import { activeElt, removeChildren, contains } from "../util/dom.js"
import { hasHandler, signal } from "../util/event.js"
import { indexOf } from "../util/misc.js"

import { buildLineElement, updateLineForChanges } from "./update_line.js"
import { startWorker } from "./highlight_worker.js"
import { maybeUpdateLineNumberWidth } from "./line_numbers.js"
import { measureForScrollbars, updateScrollbars } from "./scrollbars.js"
import { updateSelection } from "./selection.js"
import { updateHeightsInViewport, visibleLines } from "./update_lines.js"
import { adjustView, countDirtyView, resetView } from "./view_tracking.js"

// DISPLAY DRAWING

export class DisplayUpdate {
  constructor(cm, viewport, force) {
    let display = cm.display

    this.viewport = viewport
    // Store some values that we'll need later (but don't want to force a relayout for)
    this.visible = visibleLines(display, cm.doc, viewport)
    this.editorIsHidden = !display.wrapper.offsetWidth
    this.wrapperHeight = display.wrapper.clientHeight
    this.wrapperWidth = display.wrapper.clientWidth
    this.oldDisplayWidth = displayWidth(cm)
    this.force = force
    this.dims = getDimensions(cm)
    this.events = []
  }

  signal(emitter, type) {
    if (hasHandler(emitter, type))
      this.events.push(arguments)
  }
  finish() {
    for (let i = 0; i < this.events.length; i++)
      signal.apply(null, this.events[i])
  }
}

export function maybeClipScrollbars(cm) {
  let display = cm.display
  if (!display.scrollbarsClipped && display.scroller.offsetWidth) {
    display.nativeBarWidth = display.scroller.offsetWidth - display.scroller.clientWidth
    display.heightForcer.style.height = scrollGap(cm) + "px"
    display.sizer.style.marginBottom = -display.nativeBarWidth + "px"
    display.sizer.style.borderRightWidth = scrollGap(cm) + "px"
    display.scrollbarsClipped = true
  }
}

function selectionSnapshot(cm) {
  if (cm.hasFocus()) return null
  let active = activeElt()
  if (!active || !contains(cm.display.lineDiv, active)) return null
  let result = {activeElt: active}
  if (window.getSelection) {
    let sel = window.getSelection()
    if (sel.anchorNode && sel.extend && contains(cm.display.lineDiv, sel.anchorNode)) {
      result.anchorNode = sel.anchorNode
      result.anchorOffset = sel.anchorOffset
      result.focusNode = sel.focusNode
      result.focusOffset = sel.focusOffset
    }
  }
  return result
}

function restoreSelection(snapshot) {
  if (!snapshot || !snapshot.activeElt || snapshot.activeElt == activeElt()) return
  snapshot.activeElt.focus()
  if (snapshot.anchorNode && contains(document.body, snapshot.anchorNode) && contains(document.body, snapshot.focusNode)) {
    let sel = window.getSelection(), range = document.createRange()
    range.setEnd(snapshot.anchorNode, snapshot.anchorOffset)
    range.collapse(false)
    sel.removeAllRanges()
    sel.addRange(range)
    sel.extend(snapshot.focusNode, snapshot.focusOffset)
  }
}

// Does the actual updating of the line display. Bails out
// (returning false) when there is nothing to be done and forced is
// false.
export function updateDisplayIfNeeded(cm, update) {
  let display = cm.display, doc = cm.doc

  if (update.editorIsHidden) {
    resetView(cm)
    return false
  }

  // Bail out if the visible area is already rendered and nothing changed.
  if (!update.force &&
      update.visible.from >= display.viewFrom && update.visible.to <= display.viewTo &&
      (display.updateLineNumbers == null || display.updateLineNumbers >= display.viewTo) &&
      display.renderedView == display.view && countDirtyView(cm) == 0)
    return false

  if (maybeUpdateLineNumberWidth(cm)) {
    resetView(cm)
    update.dims = getDimensions(cm)
  }

  // Compute a suitable new viewport (from & to)
  let end = doc.first + doc.size
  let from = Math.max(update.visible.from - cm.options.viewportMargin, doc.first)
  let to = Math.min(end, update.visible.to + cm.options.viewportMargin)
  if (display.viewFrom < from && from - display.viewFrom < 20) from = Math.max(doc.first, display.viewFrom)
  if (display.viewTo > to && display.viewTo - to < 20) to = Math.min(end, display.viewTo)
  if (sawCollapsedSpans) {
    from = visualLineNo(cm.doc, from)
    to = visualLineEndNo(cm.doc, to)
  }

  let different = from != display.viewFrom || to != display.viewTo ||
    display.lastWrapHeight != update.wrapperHeight || display.lastWrapWidth != update.wrapperWidth
  adjustView(cm, from, to)

  display.viewOffset = heightAtLine(getLine(cm.doc, display.viewFrom))
  // Position the mover div to align with the current scroll position
  cm.display.mover.style.top = display.viewOffset + "px"

  let toUpdate = countDirtyView(cm)
  if (!different && toUpdate == 0 && !update.force && display.renderedView == display.view &&
      (display.updateLineNumbers == null || display.updateLineNumbers >= display.viewTo))
    return false

  // For big changes, we hide the enclosing element during the
  // update, since that speeds up the operations on most browsers.
  let selSnapshot = selectionSnapshot(cm)
  if (toUpdate > 4) display.lineDiv.style.display = "none"
  patchDisplay(cm, display.updateLineNumbers, update.dims)
  if (toUpdate > 4) display.lineDiv.style.display = ""
  display.renderedView = display.view
  // There might have been a widget with a focused element that got
  // hidden or updated, if so re-focus it.
  restoreSelection(selSnapshot)

  // Prevent selection and cursors from interfering with the scroll
  // width and height.
  removeChildren(display.cursorDiv)
  removeChildren(display.selectionDiv)
  display.gutters.style.height = display.sizer.style.minHeight = 0

  if (different) {
    display.lastWrapHeight = update.wrapperHeight
    display.lastWrapWidth = update.wrapperWidth
    startWorker(cm, 400)
  }

  display.updateLineNumbers = null

  return true
}

export function postUpdateDisplay(cm, update) {
  let viewport = update.viewport

  for (let first = true;; first = false) {
    if (!first || !cm.options.lineWrapping || update.oldDisplayWidth == displayWidth(cm)) {
      // Clip forced viewport to actual scrollable area.
      if (viewport && viewport.top != null)
        viewport = {top: Math.min(cm.doc.height + paddingVert(cm.display) - displayHeight(cm), viewport.top)}
      // Updated line heights might result in the drawn area not
      // actually covering the viewport. Keep looping until it does.
      update.visible = visibleLines(cm.display, cm.doc, viewport)
      if (update.visible.from >= cm.display.viewFrom && update.visible.to <= cm.display.viewTo)
        break
    }
    if (!updateDisplayIfNeeded(cm, update)) break
    updateHeightsInViewport(cm)
    let barMeasure = measureForScrollbars(cm)
    updateSelection(cm)
    updateScrollbars(cm, barMeasure)
    setDocumentHeight(cm, barMeasure)
    update.force = false
  }

  update.signal(cm, "update", cm)
  if (cm.display.viewFrom != cm.display.reportedViewFrom || cm.display.viewTo != cm.display.reportedViewTo) {
    update.signal(cm, "viewportChange", cm, cm.display.viewFrom, cm.display.viewTo)
    cm.display.reportedViewFrom = cm.display.viewFrom; cm.display.reportedViewTo = cm.display.viewTo
  }
}

export function updateDisplaySimple(cm, viewport) {
  let update = new DisplayUpdate(cm, viewport)
  if (updateDisplayIfNeeded(cm, update)) {
    updateHeightsInViewport(cm)
    postUpdateDisplay(cm, update)
    let barMeasure = measureForScrollbars(cm)
    updateSelection(cm)
    updateScrollbars(cm, barMeasure)
    setDocumentHeight(cm, barMeasure)
    update.finish()
  }
}

// Sync the actual display DOM structure with display.view, removing
// nodes for lines that are no longer in view, and creating the ones
// that are not there yet, and updating the ones that are out of
// date.
function patchDisplay(cm, updateNumbersFrom, dims) {
  let display = cm.display, lineNumbers = cm.options.lineNumbers
  let container = display.lineDiv, cur = container.firstChild

  function rm(node) {
    let next = node.nextSibling
    // Works around a throw-scroll bug in OS X Webkit
    if (webkit && mac && cm.display.currentWheelTarget == node)
      node.style.display = "none"
    else
      node.parentNode.removeChild(node)
    return next
  }

  let view = display.view, lineN = display.viewFrom
  // Loop over the elements in the view, syncing cur (the DOM nodes
  // in display.lineDiv) with the view as we go.
  for (let i = 0; i < view.length; i++) {
    let lineView = view[i]
    if (lineView.hidden) {
    } else if (!lineView.node || lineView.node.parentNode != container) { // Not drawn yet
      let node = buildLineElement(cm, lineView, lineN, dims)
      container.insertBefore(node, cur)
    } else { // Already drawn
      while (cur != lineView.node) cur = rm(cur)
      let updateNumber = lineNumbers && updateNumbersFrom != null &&
        updateNumbersFrom <= lineN && lineView.lineNumber
      if (lineView.changes) {
        if (indexOf(lineView.changes, "gutter") > -1) updateNumber = false
        updateLineForChanges(cm, lineView, lineN, dims)
      }
      if (updateNumber) {
        removeChildren(lineView.lineNumber)
        lineView.lineNumber.appendChild(document.createTextNode(lineNumberFor(cm.options, lineN)))
      }
      cur = lineView.node.nextSibling
    }
    lineN += lineView.size
  }
  while (cur) cur = rm(cur)
}

export function updateGutterSpace(display) {
  let width = display.gutters.offsetWidth
  display.sizer.style.marginLeft = width + "px"
}

export function setDocumentHeight(cm, measure) {
  cm.display.sizer.style.minHeight = measure.docHeight + "px"
  cm.display.heightForcer.style.top = measure.docHeight + "px"
  cm.display.gutters.style.height = (measure.docHeight + cm.display.barHeight + scrollGap(cm)) + "px"
}
