local graphics = {}

function graphics.pixel(GPU, x, y, color)
    local screenY = math.ceil(y / 2)
    local baseChar, baseForeground, baseBackground = GPU.get(x, screenY)
    GPU.setForeground(color)
    GPU.setBackground(baseBackground)
    if y % 2 == 1 then --Upper half of pixel
        GPU.set(x, screenY, "▀")
    else --Lower half of pixel
        GPU.set(x, screenY, "▄")
    end
end

function graphics.rectangle(GPU, x, y, w, h, color)
    local hLeft = h
    if x > 0 and y > 0 then
        if y % 2 == 0 then
            for i = x, x + w - 1 do
                graphics.pixel(GPU, i, y, color)
            end
            hLeft = hLeft - 1
        end
        GPU.setBackground(table.unpack(color))
        GPU.setForeground(table.unpack(color))
        if hLeft % 2 == 1 then
            GPU.fill(x, math.ceil(y / 2) + (h - hLeft), w, (hLeft - 1) / 2, "█")
            for j = x, x + w - 1 do
                graphics.pixel(GPU, j, y + h - 1, color)
            end
        else
            GPU.fill(x, math.ceil(y / 2) + (h - hLeft), w, hLeft / 2, "█")
        end
    end
end

function graphics.text(GPU, x, y, color, string)
    if y % 2 == 0 then
        error("Text position must be odd on y axis")
    end
    local screenY = math.ceil(y / 2)
    GPU.setForeground(table.unpack(color))
    for i = 0, #string - 1 do
        local baseChar, baseForeground, baseBackground = GPU.get(x + i, screenY)
        GPU.setBackground(baseBackground)
        GPU.fill(x + i, screenY, 1, 1, string:sub(i + 1, i + 1))
    end
end

function graphics.centeredText(GPU, x, y, color, string)
    if y % 2 == 0 then
        error("Text position must be odd on y axis")
    end
    local screenY = math.ceil(y / 2)
    local oldForeground = GPU.setForeground(table.unpack(color))
    local oldBackground = GPU.getBackground()
    for i = 0, #string - 1 do
        local baseChar, baseForeground, baseBackground = GPU.get(x + i - math.ceil(#string / 2) + 1, screenY)
        GPU.setBackground(baseBackground)
        GPU.fill(x + i - math.ceil(#string / 2) + 1, screenY, 1, 1, string:sub(i + 1, i + 1))
    end
    GPU.setBackground(oldBackground)
    GPU.setForeground(oldForeground)
end

function graphics.border(GPU, w, h, color)
    graphics.rectangle(GPU, 1, 1, w, 1, color)
    graphics.rectangle(GPU, 1, h * 2, w, 1, color)
    graphics.rectangle(GPU, 1, 1, 1, h * 2, color)
    graphics.rectangle(GPU, w, 1, 1, h * 2, color)
end
graphics.currentWindows = {}
function graphics.checkCollision(GPU, x, y)
    for window, params in pairs(graphics.currentWindows) do
        if x >= params.x and x <= params.x + params.w - 1 then
            if y >= params.y and y <= params.y + math.ceil(params.h / 2) - 1 then
                return window
            end
        end
    end
    return nil
end
function graphics.createWindow(GPU, width, height, name)
    local pageNumber = GPU.allocateBuffer(width, math.ceil(height / 2))
    graphics.currentWindows[name] = {page = pageNumber, x = 1, y = 1, w = width, h = height, GPU = GPU}
    return pageNumber
end
local function copyWindow(GPU, x, y, page, destination)
    destination = 0 or destination
    GPU.bitblt(destination, x, y, 160, 50, page, 1, 1)
end
function graphics.refresh(GPU)
    for window, params in pairs(graphics.currentWindows) do
        if params.w > 0 then
            copyWindow(GPU, params.x, params.y, params.page)
        end
    end
    GPU.setActiveBuffer(0)
end

graphics.windows = {}
function graphics.update()
    local function redraw()
        for window, params in pairs(graphics.windows) do
            copyWindow(params.GPU, params.x, params.y, params.page)
        end
    end
    for name, params in pairs(graphics.windows) do
        params.GPU.setActiveBuffer(params.page)
        params.update(params.GPU, name, params.address)
        params.GPU.setActiveBuffer(0)
    end
    redraw()
    os.sleep()
end
function graphics.clear()
    graphics.currentWindows = {}
end

return graphics