---@class Context
local Context = {
  topElements = {},
  -- Base scale configuration
  baseScale = nil, -- {width: number, height: number}
  -- Current scale factors
  scaleFactors = { x = 1.0, y = 1.0 },
  defaultTheme = nil,
  _focusedElement = nil,
  _activeEventElement = nil,
  _cachedViewport = { width = 0, height = 0 },
  -- Immediate mode state
  _immediateMode = false,
  _frameNumber = 0,
  _currentFrameElements = {},
  _immediateModeState = nil, -- Will be initialized if immediate mode is enabled
  _frameStarted = false,
  _autoBeganFrame = false,
  -- Z-index ordered element tracking for immediate mode
  _zIndexOrderedElements = {}, -- Array of elements sorted by z-index (lowest to highest)
  -- Focus management guard
  _settingFocus = false,
}

---@return number, number -- scaleX, scaleY
function Context.getScaleFactors()
  return Context.scaleFactors.x, Context.scaleFactors.y
end

--- Register an element in the z-index ordered tree (for immediate mode)
---@param element Element The element to register
function Context.registerElement(element)
  if not Context._immediateMode then
    return
  end

  table.insert(Context._zIndexOrderedElements, element)
end

function Context.clearFrameElements()
  -- Preserve retained-mode elements
  if Context._immediateMode then
    local retainedElements = {}
    for _, element in ipairs(Context._zIndexOrderedElements) do
      if element._elementMode == "retained" then
        table.insert(retainedElements, element)
      end
    end
    Context._zIndexOrderedElements = retainedElements
  else
    Context._zIndexOrderedElements = {}
  end
end

--- Sort elements by z-index (called after all elements are registered)
function Context.sortElementsByZIndex()
  -- Sort elements by z-index (lowest to highest)
  -- We need to consider parent-child relationships and z-index
  table.sort(Context._zIndexOrderedElements, function(a, b)
    -- Calculate effective z-index considering parent hierarchy
    local function getEffectiveZIndex(elem)
      local z = elem.z or 0
      local parent = elem.parent
      while parent do
        z = z + (parent.z or 0) * 1000 -- Parent z-index has much higher weight
        parent = parent.parent
      end
      return z
    end

    return getEffectiveZIndex(a) < getEffectiveZIndex(b)
  end)
end

--- Check if a point is inside an element's bounds, respecting scroll and clipping
---@param element Element The element to check
---@param x number Screen X coordinate
---@param y number Screen Y coordinate
---@return boolean True if point is inside element bounds
local function isPointInElement(element, x, y)
  local bx = element.x
  local by = element.y
  local bw = element._borderBoxWidth or (element.width + element.padding.left + element.padding.right)
  local bh = element._borderBoxHeight or (element.height + element.padding.top + element.padding.bottom)

  -- Calculate scroll offset from parent chain
  local scrollOffsetX = 0
  local scrollOffsetY = 0

  -- Walk up parent chain to check clipping and accumulate scroll offsets
  local current = element.parent
  while current do
    local overflowX = current.overflowX or current.overflow
    local overflowY = current.overflowY or current.overflow

    -- Check if parent clips content (overflow: hidden, scroll, auto)
    if overflowX == "hidden" or overflowX == "scroll" or overflowX == "auto" or overflowY == "hidden" or overflowY == "scroll" or overflowY == "auto" then
      local parentX = current.x + current.padding.left
      local parentY = current.y + current.padding.top
      local parentW = current.width
      local parentH = current.height

      if x < parentX or x > parentX + parentW or y < parentY or y > parentY + parentH then
        return false -- Point is clipped by parent
      end

      -- Accumulate scroll offset
      scrollOffsetX = scrollOffsetX + (current._scrollX or 0)
      scrollOffsetY = scrollOffsetY + (current._scrollY or 0)
    end

    current = current.parent
  end

  -- Adjust mouse position by scroll offset for hit testing
  local adjustedX = x + scrollOffsetX
  local adjustedY = y + scrollOffsetY

  return adjustedX >= bx and adjustedX <= bx + bw and adjustedY >= by and adjustedY <= by + bh
end

--- Get the topmost element at a screen position
---@param x number Screen X coordinate
---@param y number Screen Y coordinate
---@return Element|nil The topmost element at the position, or nil if none
function Context.getTopElementAt(x, y)
  if not Context._immediateMode then
    return nil
  end

  -- Helper function to find the first interactive ancestor (including self)
  local function findInteractiveAncestor(elem)
    local current = elem
    while current do
      -- An element is interactive if it has an onEvent handler, themeComponent, or is editable
      if current.onEvent or current.themeComponent or current.editable then
        return current
      end
      current = current.parent
    end
    return nil
  end

  for i = #Context._zIndexOrderedElements, 1, -1 do
    local element = Context._zIndexOrderedElements[i]

    if isPointInElement(element, x, y) then
      local interactive = findInteractiveAncestor(element)
      if interactive then
        return interactive
      end
      return element
    end
  end

  return nil
end

--- Set the focused element (centralizes focus management)
--- Automatically blurs the previously focused element if different
---@param element Element|nil The element to focus (nil to clear focus)
function Context.setFocused(element)
  if Context._focusedElement == element then
    return -- Already focused
  end

  -- Prevent re-entry during focus change
  if Context._settingFocus then
    return
  end
  Context._settingFocus = true

  -- Blur previously focused element
  if Context._focusedElement and Context._focusedElement ~= element then
    if Context._focusedElement._textEditor then
      Context._focusedElement._textEditor:blur(Context._focusedElement)
    end
  end

  -- Set new focused element
  Context._focusedElement = element

  -- Focus the new element's text editor if it has one
  if element and element._textEditor then
    element._textEditor._focused = true
  end

  Context._settingFocus = false
end

--- Get the currently focused element
---@return Element|nil The focused element, or nil if none
function Context.getFocused()
  return Context._focusedElement
end

--- Clear focus from any element
function Context.clearFocus()
  Context.setFocused(nil)
end

return Context