import { clipPos } from "../line/pos"
import { findMaxLine } from "../line/spans"
import { displayWidth, measureChar, scrollGap } from "../measurement/position_measurement"
import { signal } from "../util/event"
import { activeElt } from "../util/dom"
import { finishOperation, pushOperation } from "../util/operation_group"

import { ensureFocus } from "./focus"
import { measureForScrollbars, updateScrollbars } from "./scrollbars"
import { restartBlink } from "./selection"
import { maybeScrollWindow, scrollPosIntoView, setScrollLeft, setScrollTop } from "./scrolling"
import { DisplayUpdate, maybeClipScrollbars, postUpdateDisplay, setDocumentHeight, updateDisplayIfNeeded } from "./update_display"
import { updateHeightsInViewport } from "./update_lines"

// Operations are used to wrap a series of changes to the editor
// state in such a way that each change won't have to update the
// cursor and display (which would be awkward, slow, and
// error-prone). Instead, display updates are batched and then all
// combined and executed at once.

let nextOpId = 0
// Start a new operation.
export function startOperation(cm) {
  cm.curOp = {
    cm: cm,
    viewChanged: false,      // Flag that indicates that lines might need to be redrawn
    startHeight: cm.doc.height, // Used to detect need to update scrollbar
    forceUpdate: false,      // Used to force a redraw
    updateInput: null,       // Whether to reset the input textarea
    typing: false,           // Whether this reset should be careful to leave existing text (for compositing)
    changeObjs: null,        // Accumulated changes, for firing change events
    cursorActivityHandlers: null, // Set of handlers to fire cursorActivity on
    cursorActivityCalled: 0, // Tracks which cursorActivity handlers have been called already
    selectionChanged: false, // Whether the selection needs to be redrawn
    updateMaxLine: false,    // Set when the widest line needs to be determined anew
    scrollLeft: null, scrollTop: null, // Intermediate scroll position, not pushed to DOM yet
    scrollToPos: null,       // Used to scroll to a specific position
    focus: false,
    id: ++nextOpId           // Unique ID
  }
  pushOperation(cm.curOp)
}

// Finish an operation, updating the display and signalling delayed events
export function endOperation(cm) {
  let op = cm.curOp
  finishOperation(op, group => {
    for (let i = 0; i < group.ops.length; i++)
      group.ops[i].cm.curOp = null
    endOperations(group)
  })
}

// The DOM updates done when an operation finishes are batched so
// that the minimum number of relayouts are required.
function endOperations(group) {
  let ops = group.ops
  for (let i = 0; i < ops.length; i++) // Read DOM
    endOperation_R1(ops[i])
  for (let i = 0; i < ops.length; i++) // Write DOM (maybe)
    endOperation_W1(ops[i])
  for (let i = 0; i < ops.length; i++) // Read DOM
    endOperation_R2(ops[i])
  for (let i = 0; i < ops.length; i++) // Write DOM (maybe)
    endOperation_W2(ops[i])
  for (let i = 0; i < ops.length; i++) // Read DOM
    endOperation_finish(ops[i])
}

function endOperation_R1(op) {
  let cm = op.cm, display = cm.display
  maybeClipScrollbars(cm)
  if (op.updateMaxLine) findMaxLine(cm)

  op.mustUpdate = op.viewChanged || op.forceUpdate || op.scrollTop != null ||
    op.scrollToPos && (op.scrollToPos.from.line < display.viewFrom ||
                       op.scrollToPos.to.line >= display.viewTo) ||
    display.maxLineChanged && cm.options.lineWrapping
  op.update = op.mustUpdate &&
    new DisplayUpdate(cm, op.mustUpdate && {top: op.scrollTop, ensure: op.scrollToPos}, op.forceUpdate)
}

function endOperation_W1(op) {
  op.updatedDisplay = op.mustUpdate && updateDisplayIfNeeded(op.cm, op.update)
}

function endOperation_R2(op) {
  let cm = op.cm, display = cm.display
  if (op.updatedDisplay) updateHeightsInViewport(cm)

  op.barMeasure = measureForScrollbars(cm)

  // If the max line changed since it was last measured, measure it,
  // and ensure the document's width matches it.
  // updateDisplay_W2 will use these properties to do the actual resizing
  if (display.maxLineChanged && !cm.options.lineWrapping) {
    op.adjustWidthTo = measureChar(cm, display.maxLine, display.maxLine.text.length).left + 3
    cm.display.sizerWidth = op.adjustWidthTo
    op.barMeasure.scrollWidth =
      Math.max(display.scroller.clientWidth, display.sizer.offsetLeft + op.adjustWidthTo + scrollGap(cm) + cm.display.barWidth)
    op.maxScrollLeft = Math.max(0, display.sizer.offsetLeft + op.adjustWidthTo - displayWidth(cm))
  }

  if (op.updatedDisplay || op.selectionChanged)
    op.preparedSelection = display.input.prepareSelection(op.focus)
}

function endOperation_W2(op) {
  let cm = op.cm

  if (op.adjustWidthTo != null) {
    cm.display.sizer.style.minWidth = op.adjustWidthTo + "px"
    if (op.maxScrollLeft < cm.doc.scrollLeft)
      setScrollLeft(cm, Math.min(cm.display.scroller.scrollLeft, op.maxScrollLeft), true)
    cm.display.maxLineChanged = false
  }

  let takeFocus = op.focus && op.focus == activeElt() && (!document.hasFocus || document.hasFocus())
  if (op.preparedSelection)
    cm.display.input.showSelection(op.preparedSelection, takeFocus)
  if (op.updatedDisplay || op.startHeight != cm.doc.height)
    updateScrollbars(cm, op.barMeasure)
  if (op.updatedDisplay)
    setDocumentHeight(cm, op.barMeasure)

  if (op.selectionChanged) restartBlink(cm)

  if (cm.state.focused && op.updateInput)
    cm.display.input.reset(op.typing)
  if (takeFocus) ensureFocus(op.cm)
}

function endOperation_finish(op) {
  let cm = op.cm, display = cm.display, doc = cm.doc

  if (op.updatedDisplay) postUpdateDisplay(cm, op.update)

  // Abort mouse wheel delta measurement, when scrolling explicitly
  if (display.wheelStartX != null && (op.scrollTop != null || op.scrollLeft != null || op.scrollToPos))
    display.wheelStartX = display.wheelStartY = null

  // Propagate the scroll position to the actual DOM scroller
  if (op.scrollTop != null) setScrollTop(cm, op.scrollTop, op.forceScroll)

  if (op.scrollLeft != null) setScrollLeft(cm, op.scrollLeft, true, true)
  // If we need to scroll a specific position into view, do so.
  if (op.scrollToPos) {
    let rect = scrollPosIntoView(cm, clipPos(doc, op.scrollToPos.from),
                                 clipPos(doc, op.scrollToPos.to), op.scrollToPos.margin)
    maybeScrollWindow(cm, rect)
  }

  // Fire events for markers that are hidden/unidden by editing or
  // undoing
  let hidden = op.maybeHiddenMarkers, unhidden = op.maybeUnhiddenMarkers
  if (hidden) for (let i = 0; i < hidden.length; ++i)
    if (!hidden[i].lines.length) signal(hidden[i], "hide")
  if (unhidden) for (let i = 0; i < unhidden.length; ++i)
    if (unhidden[i].lines.length) signal(unhidden[i], "unhide")

  if (display.wrapper.offsetHeight)
    doc.scrollTop = cm.display.scroller.scrollTop

  // Fire change events, and delayed event handlers
  if (op.changeObjs)
    signal(cm, "changes", cm, op.changeObjs)
  if (op.update)
    op.update.finish()
}

// Run the given function in an operation
export function runInOp(cm, f) {
  if (cm.curOp) return f()
  startOperation(cm)
  try { return f() }
  finally { endOperation(cm) }
}
// Wraps a function in an operation. Returns the wrapped function.
export function operation(cm, f) {
  return function() {
    if (cm.curOp) return f.apply(cm, arguments)
    startOperation(cm)
    try { return f.apply(cm, arguments) }
    finally { endOperation(cm) }
  }
}
// Used to add methods to editor and doc instances, wrapping them in
// operations.
export function methodOp(f) {
  return function() {
    if (this.curOp) return f.apply(this, arguments)
    startOperation(this)
    try { return f.apply(this, arguments) }
    finally { endOperation(this) }
  }
}
export function docMethodOp(f) {
  return function() {
    let cm = this.cm
    if (!cm || cm.curOp) return f.apply(this, arguments)
    startOperation(cm)
    try { return f.apply(this, arguments) }
    finally { endOperation(cm) }
  }
}
