/**
 * Tae Won Ha - http://taewon.de - @hataewon
 * See LICENSE
 */

import Cocoa
import PureLayout

protocol WorkspaceBarDelegate: class {

  func resizeWillStart(workspaceBar: WorkspaceBar)
  func resizeDidEnd(workspaceBar: WorkspaceBar)
}

class WorkspaceBar: NSView, WorkspaceToolDelegate {

  static fileprivate let separatorColor = NSColor.controlShadowColor
  static fileprivate let separatorThickness = CGFloat(1)

  fileprivate var tools = [WorkspaceTool]()
  fileprivate weak var selectedTool: WorkspaceTool?

  fileprivate var isMouseDownOngoing = false
  fileprivate var dragIncrement = CGFloat(1)

  fileprivate var layoutConstraints = [NSLayoutConstraint]()

  required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  // MARK: - API
  static let minimumDimension = CGFloat(50)

  let location: WorkspaceBarLocation
  var isButtonVisible = true {
    didSet {
      self.relayout()
    }
  }
  var isOpen: Bool {
    return self.selectedTool != nil
  }
  var dimensionConstraint = NSLayoutConstraint()

  weak var delegate: WorkspaceBarDelegate?

  init(location: WorkspaceBarLocation) {
    self.location = location

    super.init(frame: CGRect.zero)
    super.translatesAutoresizingMaskIntoConstraints = false

    self.wantsLayer = true
    self.layer!.backgroundColor = NSColor.windowBackgroundColor.cgColor
  }

  func relayout() {
    self.removeConstraints(self.layoutConstraints)
    self.removeAllSubviews()

    if self.isEmpty() {
      self.set(dimension: 0)
      return
    }

    if self.isButtonVisible {
      self.layoutButtons()

      if self.isOpen {
        let curTool = self.selectedTool!

        self.layout(curTool)

        let newDimension = self.barDimension(withToolDimension: curTool.dimension)
        self.set(dimension: newDimension)
      } else {
        self.set(dimension: self.barDimensionWithButtonsWithoutTool())
      }

    } else {
      if self.isOpen {
        let curTool = self.selectedTool!

        self.layoutWithoutButtons(curTool)

        let newDimension = self.barDimensionWithoutButtons(withToolDimension: curTool.dimension)
        self.set(dimension: newDimension)
      } else {
        self.set(dimension: 0)
      }
    }
  }

  func append(tool: WorkspaceTool) {
    tool.delegate = self
    tool.location = self.location
    tools.append(tool)

    if self.isOpen {
      self.selectedTool?.isSelected = false
      self.selectedTool = tool
    }

    self.relayout()
  }
}

// MARK: - NSView
extension WorkspaceBar {

  override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)

    if self.isButtonVisible {
      self.drawInnerSeparator(dirtyRect)
    }

    if self.isOpen {
      self.drawOuterSeparator(dirtyRect)
    }
  }

  override func hitTest(_ point: NSPoint) -> NSView? {
    if self.resizeRect().contains(point) {
      return self
    }

    return super.hitTest(point)
  }

  override func mouseDown(with event: NSEvent) {
    guard self.isOpen else {
      return
    }

    if self.isMouseDownOngoing {
      return
    }

    let initialMouseLoc = self.convert(event.locationInWindow, from: nil)
    let mouseInResizeRect = NSMouseInRect(initialMouseLoc, self.resizeRect(), self.isFlipped)

    guard mouseInResizeRect && event.type == .leftMouseDown else {
      super.mouseDown(with: event)
      return
    }

    self.isMouseDownOngoing = true
    self.delegate?.resizeWillStart(workspaceBar: self)
    self.dimensionConstraint.priority = NSLayoutPriorityDragThatCannotResizeWindow - 1

    var dragged = false
    var curEvent = event
    let nextEventMask: NSEventMask = [
      NSEventMask.leftMouseDragged,
      NSEventMask.leftMouseDown,
      NSEventMask.leftMouseUp
    ]
    while curEvent.type != .leftMouseUp {
      let nextEvent = NSApp.nextEvent(matching: nextEventMask,
                                      until: Date.distantFuture,
                                      inMode: RunLoopMode.eventTrackingRunLoopMode,
                                      dequeue: true)
      guard nextEvent != nil else {
        break
      }

      curEvent = nextEvent!

      guard curEvent.type == .leftMouseDragged else {
        break
      }

      let curMouseLoc = self.convert(curEvent.locationInWindow, from: nil)
      let distance = sq(initialMouseLoc.x - curMouseLoc.x) + sq(initialMouseLoc.y - curMouseLoc.y)

      guard dragged || distance >= 1 else {
        continue
      }

      let locInSuperview = self.superview!.convert(curEvent.locationInWindow, from: nil)
      let newDimension = self.newDimension(forLocationInSuperview: locInSuperview)

      self.set(dimension: newDimension)

      dragged = true
    }

    self.dimensionConstraint.priority = NSLayoutPriorityDragThatCannotResizeWindow
    self.isMouseDownOngoing = false
    self.delegate?.resizeDidEnd(workspaceBar: self)
  }

  override func resetCursorRects() {
    guard self.isOpen else {
      return
    }

    switch self.location {
    case .top, .bottom:
      self.addCursorRect(self.resizeRect(), cursor: NSCursor.resizeUpDown())
    case .right, .left:
      self.addCursorRect(self.resizeRect(), cursor: NSCursor.resizeLeftRight())
    }
  }

  fileprivate func drawInnerSeparator(_ dirtyRect: NSRect) {
    WorkspaceBar.separatorColor.set()

    let innerLineRect = self.innerSeparatorRect()
    if dirtyRect.intersects(innerLineRect) {
      NSRectFill(innerLineRect)
    }
  }

  fileprivate func drawOuterSeparator(_ dirtyRect: NSRect) {
    WorkspaceBar.separatorColor.set()

    let outerLineRect = self.outerSeparatorRect()
    if dirtyRect.intersects(outerLineRect) {
      NSRectFill(outerLineRect)
    }
  }

  fileprivate func buttonSize() -> CGSize {
    if self.isEmpty() {
      return CGSize.zero
    }

    return self.tools.first!.button.intrinsicContentSize
  }

  fileprivate func innerSeparatorRect() -> CGRect {
    let bounds = self.bounds
    let thickness = WorkspaceBar.separatorThickness
    let bar = self.buttonSize()

    switch self.location {
    case .top:
      return CGRect(x: 0, y: bounds.height - bar.height - thickness, width: bounds.width, height: thickness)
    case .right:
      return CGRect(x: bounds.width - bar.width - thickness, y: 0, width: thickness, height: bounds.height)
    case .bottom:
      return CGRect(x: 0, y: bar.height, width: bounds.width, height: thickness)
    case .left:
      return CGRect(x: bar.width, y: 0, width: thickness, height: bounds.height)
    }
  }

  fileprivate func newDimension(forLocationInSuperview locInSuperview: CGPoint) -> CGFloat {
    let dimension = self.dimension(forLocationInSuperview: locInSuperview)
    return self.dragIncrement * floor(dimension / self.dragIncrement)
  }

  fileprivate func dimension(forLocationInSuperview locInSuperview: CGPoint) -> CGFloat {
    let superviewBounds = self.superview!.bounds

    switch self.location {
    case .top:
      return superviewBounds.height - locInSuperview.y
    case .right:
      return superviewBounds.width - locInSuperview.x
    case .bottom:
      return locInSuperview.y
    case .left:
      return locInSuperview.x
    }
  }

  fileprivate func sq(_ number: CGFloat) -> CGFloat {
    return number * number
  }

  fileprivate func outerSeparatorRect() -> CGRect {
    let thickness = WorkspaceBar.separatorThickness

    switch self.location {
    case .top:
      return CGRect(x: 0, y: 0, width: self.bounds.width, height: thickness)
    case .right:
      return CGRect(x: 0, y: 0, width: thickness, height: self.bounds.height)
    case .bottom:
      return CGRect(x: 0, y: self.bounds.height - thickness, width: self.bounds.width, height: thickness)
    case .left:
      return CGRect(x: self.bounds.width - thickness, y: 0, width: thickness, height: self.bounds.height)
    }
  }

  fileprivate func resizeRect() -> CGRect {
    let separatorRect = self.outerSeparatorRect()
    let clickDimension = CGFloat(4)

    switch self.location {
    case .top:
      return separatorRect.offsetBy(dx: 0, dy: clickDimension).union(separatorRect)
    case .right:
      return separatorRect.offsetBy(dx: clickDimension, dy: 0).union(separatorRect)
    case .bottom:
      return separatorRect.offsetBy(dx: 0, dy: -clickDimension).union(separatorRect)
    case .left:
      return separatorRect.offsetBy(dx: -clickDimension, dy: 0).union(separatorRect)
    }
  }

  fileprivate func set(dimension: CGFloat) {
    let saneDimension = self.saneDimension(from: dimension)

    self.dimensionConstraint.constant = saneDimension

    let toolDimension = self.toolDimension(fromBarDimension: saneDimension)
    if self.isOpen {
      self.selectedTool?.dimension = toolDimension
    }

    // In 10.12 we need the following, otherwise resizing the tools does not work correctly.
    self.layoutSubtreeIfNeeded()

    self.window?.invalidateCursorRects(for: self)
    self.needsDisplay = true
  }

  fileprivate func saneDimension(from dimension: CGFloat) -> CGFloat {
    if dimension == 0 {
      return 0
    }

    if self.isOpen {
      return max(dimension, self.selectedTool!.minimumDimension, WorkspaceBar.minimumDimension)
    }

    return max(dimension, self.barDimensionWithButtonsWithoutTool())
  }
}

// MARK: - Layout
extension WorkspaceBar {

  fileprivate func isEmpty() -> Bool {
    return self.tools.isEmpty
  }

  fileprivate func hasTools() -> Bool {
    return !self.isEmpty()
  }

  fileprivate func layoutWithoutButtons(_ tool: WorkspaceTool) {
    let view = tool.view
    let thickness = WorkspaceBar.separatorThickness

    self.addSubview(view)
    switch self.location {
    case .top:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
        view.autoPinEdge(toSuperviewEdge: .right),
        view.autoPinEdge(toSuperviewEdge: .bottom, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.height, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .right:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
        view.autoPinEdge(toSuperviewEdge: .right),
        view.autoPinEdge(toSuperviewEdge: .bottom),
        view.autoPinEdge(toSuperviewEdge: .left, withInset: thickness),

        view.autoSetDimension(.width, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .bottom:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .right),
        view.autoPinEdge(toSuperviewEdge: .bottom),
        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.height, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .left:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
        view.autoPinEdge(toSuperviewEdge: .right, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .bottom),
        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.width, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    }
  }

  fileprivate func layout(_ tool: WorkspaceTool) {
    let view = tool.view
    let button = tool.button
    let thickness = WorkspaceBar.separatorThickness

    self.addSubview(view)

    switch self.location {
    case .top:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(.top, to: .bottom, of: button, withOffset: thickness),
        view.autoPinEdge(toSuperviewEdge: .right),
        view.autoPinEdge(toSuperviewEdge: .bottom, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.height, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .right:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
        view.autoPinEdge(.right, to: .left, of: button, withOffset: -thickness),  // Offset is count l -> r,
        view.autoPinEdge(toSuperviewEdge: .bottom),
        view.autoPinEdge(toSuperviewEdge: .left, withInset: thickness),

        view.autoSetDimension(.width, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .bottom:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .right),
        view.autoPinEdge(.bottom, to: .top, of: button, withOffset: -thickness), // Offset is count t -> b,
        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.height, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    case .left:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
        view.autoPinEdge(toSuperviewEdge: .right, withInset: thickness),
        view.autoPinEdge(toSuperviewEdge: .bottom),
        view.autoPinEdge(.left, to: .right, of: button, withOffset: thickness),

        view.autoSetDimension(.width, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    }
  }

  fileprivate func layoutButtons() {
    guard let firstTool = self.tools.first else {
      return
    }

    self.tools
      .map { $0.button }
      .forEach(self.addSubview)

    let firstButton = firstTool.button
    switch self.location {
    case .top:
      self.layoutConstraints.append(contentsOf: [
        firstButton.autoPinEdge(toSuperviewEdge: .top),
        firstButton.autoPinEdge(toSuperviewEdge: .left),
        ])
    case .right:
      self.layoutConstraints.append(contentsOf: [
        firstButton.autoPinEdge(toSuperviewEdge: .top),
        firstButton.autoPinEdge(toSuperviewEdge: .right),
        ])
    case .bottom:
      self.layoutConstraints.append(contentsOf: [
        firstButton.autoPinEdge(toSuperviewEdge: .left),
        firstButton.autoPinEdge(toSuperviewEdge: .bottom),
        ])
    case .left:
      self.layoutConstraints.append(contentsOf: [
        firstButton.autoPinEdge(toSuperviewEdge: .top),
        firstButton.autoPinEdge(toSuperviewEdge: .left),
        ])
    }

    var lastButton = firstButton
    for button in self.tools[1..<self.tools.count].map({ $0.button }) {
      switch self.location {
      case .top:
        self.layoutConstraints.append(contentsOf: [
          button.autoPinEdge(toSuperviewEdge: .top),
          button.autoPinEdge(.left, to: .right, of: lastButton),
          ])
      case .right:
        self.layoutConstraints.append(contentsOf: [
          button.autoPinEdge(.top, to: .bottom, of: lastButton),
          button.autoPinEdge(toSuperviewEdge: .right),
          ])
      case .bottom:
        self.layoutConstraints.append(contentsOf: [
          button.autoPinEdge(.left, to: .right, of: lastButton),
          button.autoPinEdge(toSuperviewEdge: .bottom),
          ])
      case .left:
        self.layoutConstraints.append(contentsOf: [
          button.autoPinEdge(.top, to: .bottom, of: lastButton),
          button.autoPinEdge(toSuperviewEdge: .left),
          ])
      }

      lastButton = button
    }
  }

  fileprivate func barDimensionWithButtonsWithoutTool() -> CGFloat {
    switch self.location {
    case .top, .bottom:
      return self.buttonSize().height + WorkspaceBar.separatorThickness
    case .right, .left:
      return self.buttonSize().width + WorkspaceBar.separatorThickness
    }
  }

  fileprivate func barDimensionWithoutButtons(withToolDimension toolDimension: CGFloat) -> CGFloat {
    return toolDimension + WorkspaceBar.separatorThickness
  }

  fileprivate func barDimension(withToolDimension toolDimension: CGFloat) -> CGFloat {
    return self.barDimensionWithButtonsWithoutTool() + toolDimension + WorkspaceBar.separatorThickness
  }

  fileprivate func toolDimension(fromBarDimension barDimension: CGFloat) -> CGFloat {
    if self.isButtonVisible {
      return barDimension - WorkspaceBar.separatorThickness - barDimensionWithButtonsWithoutTool()
    }

    return barDimension - WorkspaceBar.separatorThickness
  }
}

// MARK: - WorkspaceToolDelegate
extension WorkspaceBar {

  func toggle(_ tool: WorkspaceTool) {
    self.delegate?.resizeWillStart(workspaceBar: self)

    if self.isOpen {
      let curTool = self.selectedTool!
      if curTool === tool {
        // In this case, curTool.isSelected is already set to false in WorkspaceTool.toggle()
        self.selectedTool = nil
      } else {
        curTool.isSelected = false
        self.selectedTool = tool
      }
      
    } else {
      self.selectedTool = tool
    }
    
    self.relayout()

    self.delegate?.resizeDidEnd(workspaceBar: self)
  }
}