CCGUI element

--[[

    ComputerCraft GUI
    Element

--]]

ccgui = ccgui or {}

-- Alignment enumerations
ccgui.Align = { Left = 0, Center = 1, Right = 2 }
ccgui.VAlign = { Top = 0, Middle = 1, Bottom = 2 }

--[[

    Element

]]--

local Element = common.newClass({
    -- Parent element
    parent = nil,
    -- Need repaint
    --needsRepaint = true,
    -- Colors
    foreground = colours.black,
    background = 0,
    -- Size and bounding box for drawing
    size = nil,
    bbox = nil,
    -- Border
    border = ccgui.newBorder(),
    -- Padding
    padding = ccgui.newMargins(0),
    -- Visibility
    isVisible = true
}, common.Observable)
ccgui.Element = Element

function Element:init()
    common.Observable.init(self)

    self.padding = ccgui.newMargins(self.padding)
    self.border = ccgui.newBorder(self.border)

    -- Mouse
    self:on("mouse_click", self.mouseClick, self)

    -- Focus
    self:on("focus", self.updateFocus, self)

    -- Paint
    self:on("paint", self.clear, self)
    self:on("paint", self.drawBorder, self)

    --self:markRepaint()
end

function Element:show()
    if not self.isVisible then
        --self:markRepaint()
        self.isVisible = true
        return true
    end
    return false
end

function Element:hide()
    if self.isVisible then
        --self:markRepaint()
        self.isVisible = false
        return true
    end
    return false
end

--[[

    Bounding box

--]]

-- Inner bounding box, without border and padding
function Element:inner(bbox)
    if bbox == nil then
        print("invalid bbox")
        for k,v in pairs(self) do
            print(tostring(k).."="..tostring(v))
        end
        error()
    end
    assert(bbox ~= nil, "invalid bbox")
    assert(self.padding ~= nil, "invalid padding")
    assert(self.border ~= nil, "invalid border")

    return bbox:contract(self.padding):contract(self.border:margins())
end

-- Outer bounding box, with border and padding
function Element:outer(bbox)
    assert(bbox ~= nil, "invalid bbox")
    assert(self.padding ~= nil, "invalid padding")
    assert(self.border ~= nil, "invalid border")

    return bbox:expand(self.padding):expand(self.border:margins())
end

-- Calculate element size within given size box
function Element:calcSize(size)
    self.size = ccgui.newRectangle(0, 0, 0, 0)
end

-- Calculate element layout within given bounding box
function Element:calcLayout(bbox)
    self.bbox = bbox
end

-- Update element layout within given bounding box
function Element:updateLayout(bbox)
    self:calcSize(bbox)
    self:calcLayout(ccgui.newRectangle(bbox:tl(), self.size:size()))
end

-- Check if the bounding box with padding contains the given point
function Element:contains(x, y)
    if self.bbox == nil then return false end
    return self:inner(self.bbox):expand(self.padding):contains(x, y)
end

--[[

    Focus

--]]

function Element:canFocus()
    return false
end

function Element:focus()
    if not self:canFocus() then
        return false
    end

    -- Set focus
    if not self.hasFocus then
        self.hasFocus = true
        self:trigger("focus", self)
    end

    return true
end

function Element:blur()
    if not self:canFocus() then
        return false
    end

    -- Set focus
    if self.hasFocus then
        self.hasFocus = false
        self:trigger("blur", self)
    end

    return true
end

function Element:updateFocus(newFocus)
    -- Blur if this element lost focus
    if self ~= newFocus then
        self:blur()
    end
    -- Bubble up to parent
    if self.parent ~= nil then
        self.parent:updateFocus(newFocus)
    end
end

function Element:mouseClick(button, x, y)
    if button == 1 then
        -- Left mouse button
        -- Take focus when focusable and contains mouse pointer
        if self:canFocus() and self:contains(x, y) then
            self:focus()
        end
    end
end

--[[

    Painting

]]--

-- Get the output device for drawing
function Element:getOutput()
    -- Bubble up to parent
    return self.parent:getOutput()
end

--[[function Element:markRepaint()
    self.needsRepaint = true
end

function Element:unmarkRepaint()
    self.needsRepaint = false
end]]--

function Element:paint()
    if not self.isVisible then return end
    self:trigger("beforepaint")
    if self.bbox ~= nil then
        self:trigger("paint")
    end
    self:trigger("afterpaint")
end

-- Clear element's bounding box
function Element:clear()
    local bbox = self.bbox
    for y=0,bbox.h-1 do
        for x=0,bbox.w-1 do
            self:draw(bbox.x + x, bbox.y + y, " ", self.foreground, self.background)
        end
    end
end

-- Draw single text line within bounding rectangle
function Element:draw(x, y, text, fgColor, bgColor, bounds)
    if type(x) == "table" then
        -- Position given as vector
        return self:draw(x.x, x.y, y, text, fgColor, bgColor)
    end

    if bounds then
        -- Check vertical bounds
        if y < bounds.y or y >= bounds.y + bounds.h then
            return
        end
        -- Limit to horizontal bounds
        local startIdx = 1 + math.max(0, bounds.x - x)
        local endIdx = math.min(#text, bounds.x + bounds.w - x)
        text = string.sub(text, startIdx, endIdx)
        x = x + startIdx - 1
    end

    self:drawUnsafe(x, y, text, fgColor, bgColor)
end

-- Unsafe drawing
function Element:drawUnsafe(x, y, text, fgColor, bgColor)
    -- Draw on parent
    if self.isVisible and self.parent ~= nil then
        self.parent:drawUnsafe(x, y, text, fgColor, bgColor)
    end
end

-- Draw line
function Element:drawLine(line, color)
    -- Draw each point along the line
    for i,point in ipairs(line:points()) do
        self:draw(point, " ", colours.white, color)
    end
end

-- Draw single border
function Element:drawSingleBorder(side)
    if(self.border:has(side)) then
        self:drawLine(self.bbox[side](self.bbox), self.border:get(side))
    end
end

-- Draw all borders
function Element:drawBorder()
    self:drawSingleBorder("left")
    self:drawSingleBorder("right")
    self:drawSingleBorder("top")
    self:drawSingleBorder("bottom")
end

-- Bubble event up to parent
function Element:bubbleEvent(event)
    self:on(event, function(self, ...)
        if self.parent ~= nil then
            self.parent:trigger(event, ...)
        end
    end, self)
end