local core = require "core"
local common = require "core.common"
local style = require "core.style"
local Node = require "core.node"
local View = require "core.view"
local DocView = require "core.docview"

---@class core.rootview : core.view
---@field super core.view
---@field root_node core.node
---@field mouse core.view.position
local RootView = View:extend()

function RootView:new()
  RootView.super.new(self)
  self.root_node = Node()
  self.deferred_draws = {}
  self.mouse = { x = 0, y = 0 }
  self.drag_overlay = { x = 0, y = 0, w = 0, h = 0, visible = false, opacity = 0,
                        base_color = style.drag_overlay,
                        color = { table.unpack(style.drag_overlay) } }
  self.drag_overlay.to = { x = 0, y = 0, w = 0, h = 0 }
  self.drag_overlay_tab = { x = 0, y = 0, w = 0, h = 0, visible = false, opacity = 0,
                            base_color = style.drag_overlay_tab,
                            color = { table.unpack(style.drag_overlay_tab) } }
  self.drag_overlay_tab.to = { x = 0, y = 0, w = 0, h = 0 }
end


function RootView:defer_draw(fn, ...)
  table.insert(self.deferred_draws, 1, { fn = fn, ... })
end


---@return core.node
function RootView:get_active_node()
  local node = self.root_node:get_node_for_view(core.active_view)
  if not node then node = self:get_primary_node() end
  return node
end


---@return core.node
local function get_primary_node(node)
  if node.is_primary_node then
    return node
  end
  if node.type ~= "leaf" then
    return get_primary_node(node.a) or get_primary_node(node.b)
  end
end


---@return core.node
function RootView:get_active_node_default()
  local node = self.root_node:get_node_for_view(core.active_view)
  if not node then node = self:get_primary_node() end
  if node.locked then
    local default_view = self:get_primary_node().views[1]
    assert(default_view, "internal error: cannot find original document node.")
    core.set_active_view(default_view)
    node = self:get_active_node()
  end
  return node
end


---@return core.node
function RootView:get_primary_node()
  return get_primary_node(self.root_node)
end


---@param node core.node
---@return core.node
local function select_next_primary_node(node)
  if node.is_primary_node then return end
  if node.type ~= "leaf" then
    return select_next_primary_node(node.a) or select_next_primary_node(node.b)
  else
    local lx, ly = node:get_locked_size()
    if not lx and not ly then
      return node
    end
  end
end


---@return core.node
function RootView:select_next_primary_node()
  return select_next_primary_node(self.root_node)
end


---@param doc core.doc
---@return core.docview
function RootView:open_doc(doc)
  local node = self:get_active_node_default()
  for i, view in ipairs(node.views) do
    if view.doc == doc then
      node:set_active_view(node.views[i])
      return view
    end
  end
  local view = DocView(doc)
  node:add_view(view)
  self.root_node:update_layout()
  view:scroll_to_line(view.doc:get_selection(), true, true)
  return view
end


---@param keep_active boolean
function RootView:close_all_docviews(keep_active)
  self.root_node:close_all_docviews(keep_active)
end


---Function to intercept mouse pressed events on the active view.
---Do nothing by default.
---@param button core.view.mousebutton
---@param x number
---@param y number
---@param clicks integer
function RootView.on_view_mouse_pressed(button, x, y, clicks)
end


---@param button core.view.mousebutton
---@param x number
---@param y number
---@param clicks integer
---@return boolean
function RootView:on_mouse_pressed(button, x, y, clicks)
  local div = self.root_node:get_divider_overlapping_point(x, y)
  local node = self.root_node:get_child_overlapping_point(x, y)
  if div and (node and not node.active_view:scrollbar_overlaps_point(x, y)) then
    self.dragged_divider = div
    return true
  end
  if node.hovered_scroll_button > 0 then
    node:scroll_tabs(node.hovered_scroll_button)
    return true
  end
  local idx = node:get_tab_overlapping_point(x, y)
  if idx then
    if button == "middle" or node.hovered_close == idx then
      node:close_view(self.root_node, node.views[idx])
      return true
    else
      if button == "left" then
        self.dragged_node = { node = node, idx = idx, dragging = false, drag_start_x = x, drag_start_y = y}
      end
      node:set_active_view(node.views[idx])
      return true
    end
  elseif not self.dragged_node then -- avoid sending on_mouse_pressed events when dragging tabs
    core.set_active_view(node.active_view)
    return self.on_view_mouse_pressed(button, x, y, clicks) or node.active_view:on_mouse_pressed(button, x, y, clicks)
  end
end


function RootView:get_overlay_base_color(overlay)
  if overlay == self.drag_overlay then
    return style.drag_overlay
  else
    return style.drag_overlay_tab
  end
end


function RootView:set_show_overlay(overlay, status)
  overlay.visible = status
  if status then -- reset colors
    -- reload base_color
    overlay.base_color = self:get_overlay_base_color(overlay)
    overlay.color[1] = overlay.base_color[1]
    overlay.color[2] = overlay.base_color[2]
    overlay.color[3] = overlay.base_color[3]
    overlay.color[4] = overlay.base_color[4]
    overlay.opacity = 0
  end
end


---@param button core.view.mousebutton
---@param x number
---@param y number
function RootView:on_mouse_released(button, x, y, ...)
  if self.dragged_divider then
    self.dragged_divider = nil
  end
  if self.dragged_node then
    if button == "left" then
      if self.dragged_node.dragging then
        local node = self.root_node:get_child_overlapping_point(self.mouse.x, self.mouse.y)
        local dragged_node = self.dragged_node.node

        if node and not node.locked
           -- don't do anything if dragging onto own node, with only one view
           and (node ~= dragged_node or #node.views > 1) then
          local split_type = node:get_split_type(self.mouse.x, self.mouse.y)
          local view = dragged_node.views[self.dragged_node.idx]

          if split_type ~= "middle" and split_type ~= "tab" then -- needs splitting
            local new_node = node:split(split_type)
            self.root_node:get_node_for_view(view):remove_view(self.root_node, view)
            new_node:add_view(view)
          elseif split_type == "middle" and node ~= dragged_node then -- move to other node
            dragged_node:remove_view(self.root_node, view)
            node:add_view(view)
            self.root_node:get_node_for_view(view):set_active_view(view)
          elseif split_type == "tab" then -- move besides other tabs
            local tab_index = node:get_drag_overlay_tab_position(self.mouse.x, self.mouse.y, dragged_node, self.dragged_node.idx)
            dragged_node:remove_view(self.root_node, view)
            node:add_view(view, tab_index)
            self.root_node:get_node_for_view(view):set_active_view(view)
          end
          self.root_node:update_layout()
          core.redraw = true
        end
      end
      self:set_show_overlay(self.drag_overlay, false)
      self:set_show_overlay(self.drag_overlay_tab, false)
      if self.dragged_node and self.dragged_node.dragging then
        core.request_cursor("arrow")
      end
      self.dragged_node = nil
    end
  else -- avoid sending on_mouse_released events when dragging tabs
    self.root_node:on_mouse_released(button, x, y, ...)
  end
end


local function resize_child_node(node, axis, value, delta)
  local accept_resize = node.a:resize(axis, value)
  if not accept_resize then
    accept_resize = node.b:resize(axis, node.size[axis] - value)
  end
  if not accept_resize then
    node.divider = node.divider + delta / node.size[axis]
  end
end


---@param x number
---@param y number
---@param dx number
---@param dy number
function RootView:on_mouse_moved(x, y, dx, dy)
  if core.active_view == core.nag_view then
    core.request_cursor("arrow")
    core.active_view:on_mouse_moved(x, y, dx, dy)
    return
  end

  if self.dragged_divider then
    local node = self.dragged_divider
    if node.type == "hsplit" then
      x = common.clamp(x, 0, self.root_node.size.x * 0.95)
      resize_child_node(node, "x", x, dx)
    elseif node.type == "vsplit" then
      y = common.clamp(y, 0, self.root_node.size.y * 0.95)
      resize_child_node(node, "y", y, dy)
    end
    node.divider = common.clamp(node.divider, 0.01, 0.99)
    return
  end

  self.mouse.x, self.mouse.y = x, y

  local dn = self.dragged_node
  if dn and not dn.dragging then
    -- start dragging only after enough movement
    dn.dragging = common.distance(x, y, dn.drag_start_x, dn.drag_start_y) > style.tab_width * .05
    if dn.dragging then
      core.request_cursor("hand")
    end
  end

  -- avoid sending on_mouse_moved events when dragging tabs
  if dn then return end

  self.root_node:on_mouse_moved(x, y, dx, dy)

  local last_overlapping_node = self.overlapping_node
  self.overlapping_node = self.root_node:get_child_overlapping_point(x, y)

  if last_overlapping_node and last_overlapping_node ~= self.overlapping_node then
    last_overlapping_node:on_mouse_left()
  end

  local div = self.root_node:get_divider_overlapping_point(x, y)
  local tab_index = self.overlapping_node and self.overlapping_node:get_tab_overlapping_point(x, y)
  if self.overlapping_node and self.overlapping_node:get_scroll_button_index(x, y) then
    core.request_cursor("arrow")
  elseif div and (self.overlapping_node and not self.overlapping_node.active_view:scrollbar_overlaps_point(x, y)) then
    core.request_cursor(div.type == "hsplit" and "sizeh" or "sizev")
  elseif tab_index then
    core.request_cursor("arrow")
  elseif self.overlapping_node then
    core.request_cursor(self.overlapping_node.active_view.cursor)
  end
end


function RootView:on_mouse_left()
  if self.overlapping_node then
    self.overlapping_node:on_mouse_left()
  end
end


---@param filename string
---@param x number
---@param y number
---@return boolean
function RootView:on_file_dropped(filename, x, y)
  local node = self.root_node:get_child_overlapping_point(x, y)
  return node and node.active_view:on_file_dropped(filename, x, y)
end


function RootView:on_mouse_wheel(...)
  local x, y = self.mouse.x, self.mouse.y
  local node = self.root_node:get_child_overlapping_point(x, y)
  return node.active_view:on_mouse_wheel(...)
end


function RootView:on_text_input(...)
  core.active_view:on_text_input(...)
end


function RootView:on_focus_lost(...)
  -- We force a redraw so documents can redraw without the cursor.
  core.redraw = true
end


function RootView:interpolate_drag_overlay(overlay)
  self:move_towards(overlay, "x", overlay.to.x, nil, "tab_drag")
  self:move_towards(overlay, "y", overlay.to.y, nil, "tab_drag")
  self:move_towards(overlay, "w", overlay.to.w, nil, "tab_drag")
  self:move_towards(overlay, "h", overlay.to.h, nil, "tab_drag")

  self:move_towards(overlay, "opacity", overlay.visible and 100 or 0, nil, "tab_drag")
  overlay.color[4] = overlay.base_color[4] * overlay.opacity / 100
end


function RootView:update()
  Node.copy_position_and_size(self.root_node, self)
  self.root_node:update()
  self.root_node:update_layout()

  self:update_drag_overlay()
  self:interpolate_drag_overlay(self.drag_overlay)
  self:interpolate_drag_overlay(self.drag_overlay_tab)
end


function RootView:set_drag_overlay(overlay, x, y, w, h, immediate)
  overlay.to.x = x
  overlay.to.y = y
  overlay.to.w = w
  overlay.to.h = h
  if immediate then
    overlay.x = x
    overlay.y = y
    overlay.w = w
    overlay.h = h
  end
  if not overlay.visible then
    self:set_show_overlay(overlay, true)
  end
end


local function get_split_sizes(split_type, x, y, w, h)
  if split_type == "left" then
    w = w * .5
  elseif split_type == "right" then
    x = x + w * .5
    w = w * .5
  elseif split_type == "up" then
    h = h * .5
  elseif split_type == "down" then
    y = y + h * .5
    h = h * .5
  end
  return x, y, w, h
end


function RootView:update_drag_overlay()
  if not (self.dragged_node and self.dragged_node.dragging) then return end
  local over = self.root_node:get_child_overlapping_point(self.mouse.x, self.mouse.y)
  if over and not over.locked then
    local _, _, _, tab_h = over:get_scroll_button_rect(1)
    local x, y = over.position.x, over.position.y
    local w, h = over.size.x, over.size.y
    local split_type = over:get_split_type(self.mouse.x, self.mouse.y)

    if split_type == "tab" and (over ~= self.dragged_node.node or #over.views > 1) then
      local tab_index, tab_x, tab_y, tab_w, tab_h = over:get_drag_overlay_tab_position(self.mouse.x, self.mouse.y)
      self:set_drag_overlay(self.drag_overlay_tab,
        tab_x + (tab_index and 0 or tab_w), tab_y,
        style.caret_width, tab_h,
        -- avoid showing tab overlay moving between nodes
        over ~= self.drag_overlay_tab.last_over)
      self:set_show_overlay(self.drag_overlay, false)
      self.drag_overlay_tab.last_over = over
    else
      if (over ~= self.dragged_node.node or #over.views > 1) then
        y = y + tab_h
        h = h - tab_h
        x, y, w, h = get_split_sizes(split_type, x, y, w, h)
      end
      self:set_drag_overlay(self.drag_overlay, x, y, w, h)
      self:set_show_overlay(self.drag_overlay_tab, false)
    end
  else
    self:set_show_overlay(self.drag_overlay, false)
    self:set_show_overlay(self.drag_overlay_tab, false)
  end
end


function RootView:draw_grabbed_tab()
  local dn = self.dragged_node
  local _,_, w, h = dn.node:get_tab_rect(dn.idx)
  local x = self.mouse.x - w / 2
  local y = self.mouse.y - h / 2
  local view = dn.node.views[dn.idx]
  self.root_node:draw_tab(view, true, true, false, x, y, w, h, true)
end


function RootView:draw_drag_overlay(ov)
  if ov.opacity > 0 then
    renderer.draw_rect(ov.x, ov.y, ov.w, ov.h, ov.color)
  end
end


function RootView:draw()
  self.root_node:draw()
  while #self.deferred_draws > 0 do
    local t = table.remove(self.deferred_draws)
    t.fn(table.unpack(t))
  end

  self:draw_drag_overlay(self.drag_overlay)
  self:draw_drag_overlay(self.drag_overlay_tab)
  if self.dragged_node and self.dragged_node.dragging then
    self:draw_grabbed_tab()
  end
  if core.cursor_change_req then
    system.set_cursor(core.cursor_change_req)
    core.cursor_change_req = nil
  end
end


return RootView