DoubleBuffering.lua

local component = require("component")
local unicode = require("unicode")
local color = require("color")
local image = require("image")

--------------------------------------------------------------------------------

local bufferWidth, bufferHeight
local currentFrameBackgrounds, currentFrameForegrounds, currentFrameSymbols, newFrameBackgrounds, newFrameForegrounds, newFrameSymbols
local drawLimitX1, drawLimitX2, drawLimitY1, drawLimitY2
local GPUProxy, GPUProxyGetResolution, GPUProxySetResolution, GPUProxyBind, GPUProxyGetBackground, GPUProxyGetForeground, GPUProxySetBackground, GPUProxySetForeground, GPUProxyGet, GPUProxySet, GPUProxyFill

local mathCeil, mathFloor, mathModf, mathAbs = math.ceil, math.floor, math.modf, math.abs
local tableInsert, tableConcat = table.insert, table.concat
local colorBlend = color.blend
local unicodeLen, unicodeSub = unicode.len, unicode.sub

--------------------------------------------------------------------------------

local function getIndex(x, y)
    return bufferWidth * (y - 1) + x
end

local function getCurrentFrameTables()
    return currentFrameBackgrounds, currentFrameForegrounds, currentFrameSymbols
end

local function getNewFrameTables()
    return newFrameBackgrounds, newFrameForegrounds, newFrameSymbols
end

--------------------------------------------------------------------------------

local function setDrawLimit(x1, y1, x2, y2)
    drawLimitX1, drawLimitY1, drawLimitX2, drawLimitY2 = x1, y1, x2, y2
end

local function resetDrawLimit()
    drawLimitX1, drawLimitY1, drawLimitX2, drawLimitY2 = 1, 1, bufferWidth, bufferHeight
end

local function getDrawLimit()
    return drawLimitX1, drawLimitY1, drawLimitX2, drawLimitY2
end

--------------------------------------------------------------------------------

local function flush(width, height)
    if not width or not height then
        width, height = GPUProxyGetResolution()
    end

    currentFrameBackgrounds, currentFrameForegrounds, currentFrameSymbols, newFrameBackgrounds, newFrameForegrounds, newFrameSymbols = {}, {}, {}, {}, {}, {}
    bufferWidth = width
    bufferHeight = height
    resetDrawLimit()

    for y = 1, bufferHeight do
        for x = 1, bufferWidth do
            tableInsert(currentFrameBackgrounds, 0x010101)
            tableInsert(currentFrameForegrounds, 0xFEFEFE)
            tableInsert(currentFrameSymbols, " ")

            tableInsert(newFrameBackgrounds, 0x010101)
            tableInsert(newFrameForegrounds, 0xFEFEFE)
            tableInsert(newFrameSymbols, " ")
        end
    end
end

local function setResolution(width, height)
    GPUProxySetResolution(width, height)
    flush(width, height)
end

local function getResolution()
    return bufferWidth, bufferHeight
end

local function getWidth()
    return bufferWidth
end

local function getHeight()
    return bufferHeight
end

local function bindScreen(...)
    GPUProxyBind(...)
    flush(GPUProxyGetResolution())
end

local function getGPUProxy()
    return GPUProxy
end

local function updateGPUProxyMethods()
    GPUProxyGet = GPUProxy.get
    GPUProxyGetResolution = GPUProxy.getResolution
    GPUProxyGetBackground = GPUProxy.getBackground
    GPUProxyGetForeground = GPUProxy.getForeground

    GPUProxySet = GPUProxy.set
    GPUProxySetResolution = GPUProxy.setResolution
    GPUProxySetBackground = GPUProxy.setBackground
    GPUProxySetForeground = GPUProxy.setForeground

    GPUProxyBind = GPUProxy.bind
    GPUProxyFill = GPUProxy.fill
end

local function bindGPU(address)
    GPUProxy = component.proxy(address)
    updateGPUProxyMethods()
    flush(GPUProxyGetResolution())
end

--------------------------------------------------------------------------------

local function rawSet(index, background, foreground, symbol)
    newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, foreground, symbol
end

local function rawGet(index)
    return newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index]
end

local function get(x, y)
    if x >= 1 and y >= 1 and x <= bufferWidth and y <= bufferHeight then
        local index = bufferWidth * (y - 1) + x
        return newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index]
    else
        return 0x000000, 0x000000, " "
    end
end

local function set(x, y, background, foreground, symbol)
    if x >= drawLimitX1 and y >= drawLimitY1 and x <= drawLimitX2 and y <= drawLimitY2 then
        local index = bufferWidth * (y - 1) + x
        newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, foreground, symbol
    end
end

local function drawRectangle(x, y, width, height, background, foreground, symbol, transparency)
    local index, indexStepOnReachOfSquareWidth = bufferWidth * (y - 1) + x, bufferWidth - width
    for j = y, y + height - 1 do
        if j >= drawLimitY1 and j <= drawLimitY2 then
            for i = x, x + width - 1 do
                if i >= drawLimitX1 and i <= drawLimitX2 then
                    if transparency then
                        newFrameBackgrounds[index], newFrameForegrounds[index] =
                        colorBlend(newFrameBackgrounds[index], background, transparency),
                        colorBlend(newFrameForegrounds[index], background, transparency)
                    else
                        newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, foreground, symbol
                    end
                end

                index = index + 1
            end

            index = index + indexStepOnReachOfSquareWidth
        else
            index = index + bufferWidth
        end
    end
end

local function clear(color, transparency)
    drawRectangle(1, 1, bufferWidth, bufferHeight, color or 0x0, 0x000000, " ", transparency)
end

local function copy(x, y, width, height)
    local copyArray, index = { width, height }

    for j = y, y + height - 1 do
        for i = x, x + width - 1 do
            if i >= 1 and j >= 1 and i <= bufferWidth and j <= bufferHeight then
                index = bufferWidth * (j - 1) + i
                tableInsert(copyArray, newFrameBackgrounds[index])
                tableInsert(copyArray, newFrameForegrounds[index])
                tableInsert(copyArray, newFrameSymbols[index])
            else
                tableInsert(copyArray, 0x0)
                tableInsert(copyArray, 0x0)
                tableInsert(copyArray, " ")
            end
        end
    end

    return copyArray
end

local function paste(startX, startY, picture)
    local imageWidth = picture[1]
    local bufferIndex, pictureIndex, bufferIndexStepOnReachOfImageWidth = bufferWidth * (startY - 1) + startX, 3, bufferWidth - imageWidth

    for y = startY, startY + picture[2] - 1 do
        if y >= drawLimitY1 and y <= drawLimitY2 then
            for x = startX, startX + imageWidth - 1 do
                if x >= drawLimitX1 and x <= drawLimitX2 then
                    newFrameBackgrounds[bufferIndex] = picture[pictureIndex]
                    newFrameForegrounds[bufferIndex] = picture[pictureIndex + 1]
                    newFrameSymbols[bufferIndex] = picture[pictureIndex + 2]
                end

                bufferIndex, pictureIndex = bufferIndex + 1, pictureIndex + 3
            end

            bufferIndex = bufferIndex + bufferIndexStepOnReachOfImageWidth
        else
            bufferIndex, pictureIndex = bufferIndex + bufferWidth, pictureIndex + imageWidth * 3
        end
    end
end

local function rasterizeLine(x1, y1, x2, y2, method)
    local inLoopValueFrom, inLoopValueTo, outLoopValueFrom, outLoopValueTo, isReversed, inLoopValueDelta, outLoopValueDelta = x1, x2, y1, y2, false, mathAbs(x2 - x1), mathAbs(y2 - y1)
    if inLoopValueDelta < outLoopValueDelta then
        inLoopValueFrom, inLoopValueTo, outLoopValueFrom, outLoopValueTo, isReversed, inLoopValueDelta, outLoopValueDelta = y1, y2, x1, x2, true, outLoopValueDelta, inLoopValueDelta
    end

    if outLoopValueFrom > outLoopValueTo then
        outLoopValueFrom, outLoopValueTo = outLoopValueTo, outLoopValueFrom
        inLoopValueFrom, inLoopValueTo = inLoopValueTo, inLoopValueFrom
    end

    local outLoopValue, outLoopValueCounter, outLoopValueTriggerIncrement = outLoopValueFrom, 1, inLoopValueDelta / outLoopValueDelta
    local outLoopValueTrigger = outLoopValueTriggerIncrement
    for inLoopValue = inLoopValueFrom, inLoopValueTo, inLoopValueFrom < inLoopValueTo and 1 or -1 do
        if isReversed then
            method(outLoopValue, inLoopValue)
        else
            method(inLoopValue, outLoopValue)
        end

        outLoopValueCounter = outLoopValueCounter + 1
        if outLoopValueCounter > outLoopValueTrigger then
            outLoopValue, outLoopValueTrigger = outLoopValue + 1, outLoopValueTrigger + outLoopValueTriggerIncrement
        end
    end
end

local function rasterizeEllipse(centerX, centerY, radiusX, radiusY, method)
    local function rasterizeEllipsePoints(XP, YP)
        method(centerX + XP, centerY + YP)
        method(centerX - XP, centerY + YP)
        method(centerX - XP, centerY - YP)
        method(centerX + XP, centerY - YP)
    end

    local x, y, changeX, changeY, ellipseError, twoASquare, twoBSquare = radiusX, 0, radiusY * radiusY * (1 - 2 * radiusX), radiusX * radiusX, 0, 2 * radiusX * radiusX, 2 * radiusY * radiusY
    local stoppingX, stoppingY = twoBSquare * radiusX, 0

    while stoppingX >= stoppingY do
        rasterizeEllipsePoints(x, y)

        y, stoppingY, ellipseError = y + 1, stoppingY + twoASquare, ellipseError + changeY
        changeY = changeY + twoASquare

        if (2 * ellipseError + changeX) > 0 then
            x, stoppingX, ellipseError = x - 1, stoppingX - twoBSquare, ellipseError + changeX
            changeX = changeX + twoBSquare
        end
    end

    x, y, changeX, changeY, ellipseError, stoppingX, stoppingY = 0, radiusY, radiusY * radiusY, radiusX * radiusX * (1 - 2 * radiusY), 0, 0, twoASquare * radiusY

    while stoppingX <= stoppingY do
        rasterizeEllipsePoints(x, y)

        x, stoppingX, ellipseError = x + 1, stoppingX + twoBSquare, ellipseError + changeX
        changeX = changeX + twoBSquare

        if (2 * ellipseError + changeY) > 0 then
            y, stoppingY, ellipseError = y - 1, stoppingY - twoASquare, ellipseError + changeY
            changeY = changeY + twoASquare
        end
    end
end

local function drawLine(x1, y1, x2, y2, background, foreground, symbol)
    rasterizeLine(x1, y1, x2, y2, function(x, y)
        set(x, y, background, foreground, symbol)
    end)
end

local function drawEllipse(centerX, centerY, radiusX, radiusY, background, foreground, symbol)
    rasterizeEllipse(centerX, centerY, radiusX, radiusY, function(x, y)
        set(x, y, background, foreground, symbol)
    end)
end

local function drawText(x, y, textColor, data, transparency)
    if y >= drawLimitY1 and y <= drawLimitY2 then
        local charIndex, bufferIndex = 1, bufferWidth * (y - 1) + x

        for charIndex = 1, unicodeLen(data) do
            if x >= drawLimitX1 and x <= drawLimitX2 then
                if transparency then
                    newFrameForegrounds[bufferIndex] = colorBlend(newFrameBackgrounds[bufferIndex], textColor, transparency)
                else
                    newFrameForegrounds[bufferIndex] = textColor
                end

                newFrameSymbols[bufferIndex] = unicodeSub(data, charIndex, charIndex)
            end

            x, bufferIndex = x + 1, bufferIndex + 1
        end
    end
end

local function drawImage(startX, startY, picture, blendForeground)
    local bufferIndex, pictureIndex, imageWidth, backgrounds, foregrounds, alphas, symbols = bufferWidth * (startY - 1) + startX, 1, picture[1], picture[3], picture[4], picture[5], picture[6]
    local bufferIndexStepOnReachOfImageWidth = bufferWidth - imageWidth

    for y = startY, startY + picture[2] - 1 do
        if y >= drawLimitY1 and y <= drawLimitY2 then
            for x = startX, startX + imageWidth - 1 do
                if x >= drawLimitX1 and x <= drawLimitX2 then
                    if alphas[pictureIndex] == 0 then
                        newFrameBackgrounds[bufferIndex], newFrameForegrounds[bufferIndex] = backgrounds[pictureIndex], foregrounds[pictureIndex]
                    elseif alphas[pictureIndex] > 0 and alphas[pictureIndex] < 1 then
                        newFrameBackgrounds[bufferIndex] = colorBlend(newFrameBackgrounds[bufferIndex], backgrounds[pictureIndex], alphas[pictureIndex])

                        if blendForeground then
                            newFrameForegrounds[bufferIndex] = colorBlend(newFrameForegrounds[bufferIndex], foregrounds[pictureIndex], alphas[pictureIndex])
                        else
                            newFrameForegrounds[bufferIndex] = foregrounds[pictureIndex]
                        end
                    elseif alphas[pictureIndex] == 1 and symbols[pictureIndex] ~= " " then
                        newFrameForegrounds[bufferIndex] = foregrounds[pictureIndex]
                    end

                    newFrameSymbols[bufferIndex] = symbols[pictureIndex]
                end

                bufferIndex, pictureIndex = bufferIndex + 1, pictureIndex + 1
            end

            bufferIndex = bufferIndex + bufferIndexStepOnReachOfImageWidth
        else
            bufferIndex, pictureIndex = bufferIndex + bufferWidth, pictureIndex + imageWidth
        end
    end
end

local function drawFrame(x, y, width, height, color)
    local stringUp, stringDown, x2 = "┌" .. string.rep("─", width - 2) .. "┐", "└" .. string.rep("─", width - 2) .. "┘", x + width - 1

    drawText(x, y, color, stringUp); y = y + 1
    for i = 1, height - 2 do
        drawText(x, y, color, "│")
        drawText(x2, y, color, "│")
        y = y + 1
    end
    drawText(x, y, color, stringDown)
end

--------------------------------------------------------------------------------

local function semiPixelRawSet(index, color, yPercentTwoEqualsZero)
    local upperPixel, lowerPixel, bothPixel = "▀", "▄", " "
    local background, foreground, symbol = newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index]

    if yPercentTwoEqualsZero then
        if symbol == upperPixel then
            if color == foreground then
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = color, foreground, bothPixel
            else
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = color, foreground, symbol
            end
        elseif symbol == bothPixel then
            if color ~= background then
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, color, lowerPixel
            end
        else
            newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, color, lowerPixel
        end
    else
        if symbol == lowerPixel then
            if color == foreground then
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = color, foreground, bothPixel
            else
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = color, foreground, symbol
            end
        elseif symbol == bothPixel then
            if color ~= background then
                newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, color, upperPixel
            end
        else
            newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index] = background, color, upperPixel
        end
    end
end

local function semiPixelSet(x, y, color)
    local yFixed = mathCeil(y / 2)
    if x >= drawLimitX1 and yFixed >= drawLimitY1 and x <= drawLimitX2 and yFixed <= drawLimitY2 then
        semiPixelRawSet(bufferWidth * (yFixed - 1) + x, color, y % 2 == 0)
    end
end

local function drawSemiPixelRectangle(x, y, width, height, color)
    local index, indexStepForward, indexStepBackward, jPercentTwoEqualsZero, jFixed = bufferWidth * (mathCeil(y / 2) - 1) + x, (bufferWidth - width), width
    for j = y, y + height - 1 do
        jPercentTwoEqualsZero = j % 2 == 0

        for i = x, x + width - 1 do
            jFixed = mathCeil(j / 2)
            semiPixelRawSet(index, color, jPercentTwoEqualsZero)
            index = index + 1
        end

        if jPercentTwoEqualsZero then
            index = index + indexStepForward
        else
            index = index - indexStepBackward
        end
    end
end

local function drawSemiPixelLine(x1, y1, x2, y2, color)
    rasterizeLine(x1, y1, x2, y2, function(x, y)
        semiPixelSet(x, y, color)
    end)
end

local function drawSemiPixelEllipse(centerX, centerY, radiusX, radiusY, color)
    rasterizeEllipse(centerX, centerY, radiusX, radiusY, function(x, y)
        semiPixelSet(x, y, color)
    end)
end

--------------------------------------------------------------------------------

local function getPointTimedPosition(firstPoint, secondPoint, time)
    return {
        x = firstPoint.x + (secondPoint.x - firstPoint.x) * time,
        y = firstPoint.y + (secondPoint.y - firstPoint.y) * time
    }
end

local function getConnectionPoints(points, time)
    local connectionPoints = {}
    for point = 1, #points - 1 do
        tableInsert(connectionPoints, getPointTimedPosition(points[point], points[point + 1], time))
    end
    return connectionPoints
end

local function getMainPointPosition(points, time)
    if #points > 1 then
        return getMainPointPosition(getConnectionPoints(points, time), time)
    else
        return points[1]
    end
end

local function drawSemiPixelCurve(points, color, precision)
    local linePoints = {}
    for time = 0, 1, precision or 0.01 do
        tableInsert(linePoints, getMainPointPosition(points, time))
    end

    for point = 1, #linePoints - 1 do
        drawSemiPixelLine(mathFloor(linePoints[point].x), mathFloor(linePoints[point].y), mathFloor(linePoints[point + 1].x), mathFloor(linePoints[point + 1].y), color)
    end
end

--------------------------------------------------------------------------------

local function drawChanges(force)
    local index, indexStepOnEveryLine, changes = bufferWidth * (drawLimitY1 - 1) + drawLimitX1, (bufferWidth - drawLimitX2 + drawLimitX1 - 1), {}
    local x, equalChars, equalCharsIndex, charX, charIndex, currentForeground
    local currentFrameBackground, currentFrameForeground, currentFrameSymbol, changesCurrentFrameBackground, changesCurrentFrameBackgroundCurrentFrameForeground

    local changesCurrentFrameBackgroundCurrentFrameForegroundIndex

    for y = drawLimitY1, drawLimitY2 do
        x = drawLimitX1
        while x <= drawLimitX2 do
            -- Determine if some pixel data was changed (or if <force> argument was passed)
            if
            currentFrameBackgrounds[index] ~= newFrameBackgrounds[index] or
                    currentFrameForegrounds[index] ~= newFrameForegrounds[index] or
                    currentFrameSymbols[index] ~= newFrameSymbols[index] or
                    force
            then
                -- Make pixel at both frames equal
                currentFrameBackground, currentFrameForeground, currentFrameSymbol = newFrameBackgrounds[index], newFrameForegrounds[index], newFrameSymbols[index]
                currentFrameBackgrounds[index] = currentFrameBackground
                currentFrameForegrounds[index] = currentFrameForeground
                currentFrameSymbols[index] = currentFrameSymbol

                -- Look for pixels with equal chars from right of current pixel
                equalChars, equalCharsIndex, charX, charIndex = {currentFrameSymbol}, 2, x + 1, index + 1
                while charX <= drawLimitX2 do
                    -- Pixels becomes equal only if they have same background and (whitespace char or same foreground)
                    if
                    currentFrameBackground == newFrameBackgrounds[charIndex] and
                            (
                                    newFrameSymbols[charIndex] == " " or
                                            currentFrameForeground == newFrameForegrounds[charIndex]
                            )
                    then
                        -- Make pixel at both frames equal
                        currentFrameBackgrounds[charIndex] = newFrameBackgrounds[charIndex]
                        currentFrameForegrounds[charIndex] = newFrameForegrounds[charIndex]
                        currentFrameSymbols[charIndex] = newFrameSymbols[charIndex]

                        equalChars[equalCharsIndex], equalCharsIndex = currentFrameSymbols[charIndex], equalCharsIndex + 1
                    else
                        break
                    end

                    charX, charIndex = charX + 1, charIndex + 1
                end

                -- Group pixels that need to be drawn by background and foreground
                changes[currentFrameBackground] = changes[currentFrameBackground] or {}
                changesCurrentFrameBackground = changes[currentFrameBackground]
                changesCurrentFrameBackground[currentFrameForeground] = changesCurrentFrameBackground[currentFrameForeground] or {index = 1}
                changesCurrentFrameBackgroundCurrentFrameForeground = changesCurrentFrameBackground[currentFrameForeground]
                changesCurrentFrameBackgroundCurrentFrameForegroundIndex = changesCurrentFrameBackgroundCurrentFrameForeground.index

                changesCurrentFrameBackgroundCurrentFrameForeground[changesCurrentFrameBackgroundCurrentFrameForegroundIndex], changesCurrentFrameBackgroundCurrentFrameForegroundIndex = x, changesCurrentFrameBackgroundCurrentFrameForegroundIndex + 1
                changesCurrentFrameBackgroundCurrentFrameForeground[changesCurrentFrameBackgroundCurrentFrameForegroundIndex], changesCurrentFrameBackgroundCurrentFrameForegroundIndex = y, changesCurrentFrameBackgroundCurrentFrameForegroundIndex + 1
                changesCurrentFrameBackgroundCurrentFrameForeground[changesCurrentFrameBackgroundCurrentFrameForegroundIndex], changesCurrentFrameBackgroundCurrentFrameForegroundIndex = tableConcat(equalChars), changesCurrentFrameBackgroundCurrentFrameForegroundIndex + 1

                x, index, changesCurrentFrameBackgroundCurrentFrameForeground.index = x + equalCharsIndex - 2, index + equalCharsIndex - 2, changesCurrentFrameBackgroundCurrentFrameForegroundIndex
            end

            x, index = x + 1, index + 1
        end

        index = index + indexStepOnEveryLine
    end

    -- Draw grouped pixels on screen
    for background, foregrounds in pairs(changes) do
        GPUProxySetBackground(background)

        for foreground, pixels in pairs(foregrounds) do
            if currentForeground ~= foreground then
                GPUProxySetForeground(foreground)
                currentForeground = foreground
            end

            for i = 1, #pixels, 3 do
                GPUProxySet(pixels[i], pixels[i + 1], pixels[i + 2])
            end
        end
    end

    changes = nil
end

--------------------------------------------------------------------------------

bindGPU(component.getPrimary("gpu").address)

return {
    getCoordinates = getCoordinates,
    getIndex = getIndex,
    setDrawLimit = setDrawLimit,
    resetDrawLimit = resetDrawLimit,
    getDrawLimit = getDrawLimit,
    flush = flush,
    setResolution = setResolution,
    bindScreen = bindScreen,
    bindGPU = bindGPU,
    getGPUProxy = getGPUProxy,
    getResolution = getResolution,
    getWidth = getWidth,
    getHeight = getHeight,
    getCurrentFrameTables = getCurrentFrameTables,
    getNewFrameTables = getNewFrameTables,

    rawSet = rawSet,
    rawGet = rawGet,
    get = get,
    set = set,
    clear = clear,
    copy = copy,
    paste = paste,
    rasterizeLine = rasterizeLine,
    rasterizeEllipse = rasterizeEllipse,
    semiPixelRawSet = semiPixelRawSet,
    semiPixelSet = semiPixelSet,
    drawChanges = drawChanges,

    drawRectangle = drawRectangle,
    drawLine = drawLine,
    drawEllipse = drawEllipse,
    drawText = drawText,
    drawImage = drawImage,
    drawFrame = drawFrame,

    drawSemiPixelRectangle = drawSemiPixelRectangle,
    drawSemiPixelLine = drawSemiPixelLine,
    drawSemiPixelEllipse = drawSemiPixelEllipse,
    drawSemiPixelCurve = drawSemiPixelCurve,
}