--- The Window API allows easy definition of spaces within the display that can
-- be written/drawn to, then later redrawn/repositioned/etc as need be. The API
-- itself contains only one function, @{window.create}, which returns the
-- windows themselves.
--
-- Windows are considered terminal objects - as such, they have access to nearly
-- all the commands in the term API (plus a few extras of their own, listed
-- within said API) and are valid targets to redirect to.
--
-- Each window has a "parent" terminal object, which can be the computer's own
-- display, a monitor, another window or even other, user-defined terminal
-- objects. Whenever a window is rendered to, the actual screen-writing is
-- performed via that parent (or, if that has one too, then that parent, and so
-- forth). Bear in mind that the cursor of a window's parent will hence be moved
-- around etc when writing a given child window.
--
-- Windows retain a memory of everything rendered "through" them (hence acting
-- as display buffers), and if the parent's display is wiped, the window's
-- content can be easily redrawn later. A window may also be flagged as
-- invisible, preventing any changes to it from being rendered until it's
-- flagged as visible once more.
--
-- A parent terminal object may have multiple children assigned to it, and
-- windows may overlap. For example, the Multishell system functions by
-- assigning each tab a window covering the screen, each using the starting
-- terminal display as its parent, and only one of which is visible at a time.
--
-- @module window

local expect = dofile("rom/modules/main/cc/expect.lua").expect

local tHex = {
    [colors.white] = "0",
    [colors.orange] = "1",
    [colors.magenta] = "2",
    [colors.lightBlue] = "3",
    [colors.yellow] = "4",
    [colors.lime] = "5",
    [colors.pink] = "6",
    [colors.gray] = "7",
    [colors.lightGray] = "8",
    [colors.cyan] = "9",
    [colors.purple] = "a",
    [colors.blue] = "b",
    [colors.brown] = "c",
    [colors.green] = "d",
    [colors.red] = "e",
    [colors.black] = "f",
}

local type = type
local string_rep = string.rep
local string_sub = string.sub

--- Returns a terminal object that is a space within the specified parent
-- terminal object. This can then be used (or even redirected to) in the same
-- manner as eg a wrapped monitor. Refer to @{term|the term API} for a list of
-- functions available to it.
--
-- @{term} itself may not be passed as the parent, though @{term.native} is
-- acceptable. Generally, @{term.current} or a wrapped monitor will be most
-- suitable, though windows may even have other windows assigned as their
-- parents.
--
-- @tparam term.Redirect parent The parent terminal redirect to draw to.
-- @tparam number nX The x coordinate this window is drawn at in the parent terminal
-- @tparam number nY The y coordinate this window is drawn at in the parent terminal
-- @tparam number nWidth The width of this window
-- @tparam number nHeight The height of this window
-- @tparam[opt] boolean bStartVisible Whether this window is visible by
-- default. Defaults to `true`.
-- @treturn Window The constructed window
function create(parent, nX, nY, nWidth, nHeight, bStartVisible)
    expect(1, parent, "table")
    expect(2, nX, "number")
    expect(3, nY, "number")
    expect(4, nWidth, "number")
    expect(5, nHeight, "number")
    expect(6, bStartVisible, "boolean", "nil")

    if parent == term then
        error("term is not a recommended window parent, try term.current() instead", 2)
    end

    local sEmptySpaceLine
    local tEmptyColorLines = {}
    local function createEmptyLines(nWidth)
        sEmptySpaceLine = string_rep(" ", nWidth)
        for n = 0, 15 do
            local nColor = 2 ^ n
            local sHex = tHex[nColor]
            tEmptyColorLines[nColor] = string_rep(sHex, nWidth)
        end
    end

    createEmptyLines(nWidth)

    -- Setup
    local bVisible = bStartVisible ~= false
    local nCursorX = 1
    local nCursorY = 1
    local bCursorBlink = false
    local nTextColor = colors.white
    local nBackgroundColor = colors.black
    local tLines = {}
    local tPalette = {}
    do
        local sEmptyText = sEmptySpaceLine
        local sEmptyTextColor = tEmptyColorLines[nTextColor]
        local sEmptyBackgroundColor = tEmptyColorLines[nBackgroundColor]
        for y = 1, nHeight do
            tLines[y] = {
                text = sEmptyText,
                textColor = sEmptyTextColor,
                backgroundColor = sEmptyBackgroundColor,
            }
        end

        for i = 0, 15 do
            local c = 2 ^ i
            tPalette[c] = { parent.getPaletteColour(c) }
        end
    end

    -- Helper functions
    local function updateCursorPos()
        if nCursorX >= 1 and nCursorY >= 1 and
            nCursorX <= nWidth and nCursorY <= nHeight then
            parent.setCursorPos(nX + nCursorX - 1, nY + nCursorY - 1)
        else
            parent.setCursorPos(0, 0)
        end
    end

    local function updateCursorBlink()
        parent.setCursorBlink(bCursorBlink)
    end

    local function updateCursorColor()
        parent.setTextColor(nTextColor)
    end

    local function redrawLine(n)
        local tLine = tLines[n]
        parent.setCursorPos(nX, nY + n - 1)
        parent.blit(tLine.text, tLine.textColor, tLine.backgroundColor)
    end

    local function redraw()
        for n = 1, nHeight do
            redrawLine(n)
        end
    end

    local function updatePalette()
        for k, v in pairs(tPalette) do
            parent.setPaletteColour(k, v[1], v[2], v[3])
        end
    end

    local function internalBlit(sText, sTextColor, sBackgroundColor)
        local nStart = nCursorX
        local nEnd = nStart + #sText - 1
        if nCursorY >= 1 and nCursorY <= nHeight then
            if nStart <= nWidth and nEnd >= 1 then
                -- Modify line
                local tLine = tLines[nCursorY]
                if nStart == 1 and nEnd == nWidth then
                    tLine.text = sText
                    tLine.textColor = sTextColor
                    tLine.backgroundColor = sBackgroundColor
                else
                    local sClippedText, sClippedTextColor, sClippedBackgroundColor
                    if nStart < 1 then
                        local nClipStart = 1 - nStart + 1
                        local nClipEnd = nWidth - nStart + 1
                        sClippedText = string_sub(sText, nClipStart, nClipEnd)
                        sClippedTextColor = string_sub(sTextColor, nClipStart, nClipEnd)
                        sClippedBackgroundColor = string_sub(sBackgroundColor, nClipStart, nClipEnd)
                    elseif nEnd > nWidth then
                        local nClipEnd = nWidth - nStart + 1
                        sClippedText = string_sub(sText, 1, nClipEnd)
                        sClippedTextColor = string_sub(sTextColor, 1, nClipEnd)
                        sClippedBackgroundColor = string_sub(sBackgroundColor, 1, nClipEnd)
                    else
                        sClippedText = sText
                        sClippedTextColor = sTextColor
                        sClippedBackgroundColor = sBackgroundColor
                    end

                    local sOldText = tLine.text
                    local sOldTextColor = tLine.textColor
                    local sOldBackgroundColor = tLine.backgroundColor
                    local sNewText, sNewTextColor, sNewBackgroundColor
                    if nStart > 1 then
                        local nOldEnd = nStart - 1
                        sNewText = string_sub(sOldText, 1, nOldEnd) .. sClippedText
                        sNewTextColor = string_sub(sOldTextColor, 1, nOldEnd) .. sClippedTextColor
                        sNewBackgroundColor = string_sub(sOldBackgroundColor, 1, nOldEnd) .. sClippedBackgroundColor
                    else
                        sNewText = sClippedText
                        sNewTextColor = sClippedTextColor
                        sNewBackgroundColor = sClippedBackgroundColor
                    end
                    if nEnd < nWidth then
                        local nOldStart = nEnd + 1
                        sNewText = sNewText .. string_sub(sOldText, nOldStart, nWidth)
                        sNewTextColor = sNewTextColor .. string_sub(sOldTextColor, nOldStart, nWidth)
                        sNewBackgroundColor = sNewBackgroundColor .. string_sub(sOldBackgroundColor, nOldStart, nWidth)
                    end

                    tLine.text = sNewText
                    tLine.textColor = sNewTextColor
                    tLine.backgroundColor = sNewBackgroundColor
                end

                -- Redraw line
                if bVisible then
                    redrawLine(nCursorY)
                end
            end
        end

        -- Move and redraw cursor
        nCursorX = nEnd + 1
        if bVisible then
            updateCursorColor()
            updateCursorPos()
        end
    end

    --- The window object. Refer to the @{window|module's documentation} for
    -- a full description.
    --
    -- @type Window
    -- @see term.Redirect
    local window = {}

    function window.write(sText)
        sText = tostring(sText)
        internalBlit(sText, string_rep(tHex[nTextColor], #sText), string_rep(tHex[nBackgroundColor], #sText))
    end

    function window.blit(sText, sTextColor, sBackgroundColor)
        if type(sText) ~= "string" then expect(1, sText, "string") end
        if type(sTextColor) ~= "string" then expect(2, sTextColor, "string") end
        if type(sBackgroundColor) ~= "string" then expect(3, sBackgroundColor, "string") end
        if #sTextColor ~= #sText or #sBackgroundColor ~= #sText then
            error("Arguments must be the same length", 2)
        end
        internalBlit(sText, sTextColor, sBackgroundColor)
    end

    function window.clear()
        local sEmptyText = sEmptySpaceLine
        local sEmptyTextColor = tEmptyColorLines[nTextColor]
        local sEmptyBackgroundColor = tEmptyColorLines[nBackgroundColor]
        for y = 1, nHeight do
            tLines[y] = {
                text = sEmptyText,
                textColor = sEmptyTextColor,
                backgroundColor = sEmptyBackgroundColor,
            }
        end
        if bVisible then
            redraw()
            updateCursorColor()
            updateCursorPos()
        end
    end

    function window.clearLine()
        if nCursorY >= 1 and nCursorY <= nHeight then
            local sEmptyText = sEmptySpaceLine
            local sEmptyTextColor = tEmptyColorLines[nTextColor]
            local sEmptyBackgroundColor = tEmptyColorLines[nBackgroundColor]
            tLines[nCursorY] = {
                text = sEmptyText,
                textColor = sEmptyTextColor,
                backgroundColor = sEmptyBackgroundColor,
            }
            if bVisible then
                redrawLine(nCursorY)
                updateCursorColor()
                updateCursorPos()
            end
        end
    end

    function window.getCursorPos()
        return nCursorX, nCursorY
    end

    function window.setCursorPos(x, y)
        if type(x) ~= "number" then expect(1, x, "number") end
        if type(y) ~= "number" then expect(2, y, "number") end
        nCursorX = math.floor(x)
        nCursorY = math.floor(y)
        if bVisible then
            updateCursorPos()
        end
    end

    function window.setCursorBlink(blink)
        if type(blink) ~= "boolean" then expect(1, blink, "boolean") end
        bCursorBlink = blink
        if bVisible then
            updateCursorBlink()
        end
    end

    function window.getCursorBlink()
        return bCursorBlink
    end

    local function isColor()
        return parent.isColor()
    end

    function window.isColor()
        return isColor()
    end

    function window.isColour()
        return isColor()
    end

    local function setTextColor(color)
        if type(color) ~= "number" then expect(1, color, "number") end
        if tHex[color] == nil then
            error("Invalid color (got " .. color .. ")" , 2)
        end

        nTextColor = color
        if bVisible then
            updateCursorColor()
        end
    end

    window.setTextColor = setTextColor
    window.setTextColour = setTextColor

    function window.setPaletteColour(colour, r, g, b)
        if type(colour) ~= "number" then expect(1, colour, "number") end

        if tHex[colour] == nil then
            error("Invalid color (got " .. colour .. ")" , 2)
        end

        local tCol
        if type(r) == "number" and g == nil and b == nil then
            tCol = { colours.unpackRGB(r) }
            tPalette[colour] = tCol
        else
            if type(r) ~= "number" then expect(2, r, "number") end
            if type(g) ~= "number" then expect(3, g, "number") end
            if type(b) ~= "number" then expect(4, b, "number") end

            tCol = tPalette[colour]
            tCol[1] = r
            tCol[2] = g
            tCol[3] = b
        end

        if bVisible then
            return parent.setPaletteColour(colour, tCol[1], tCol[2], tCol[3])
        end
    end

    window.setPaletteColor = window.setPaletteColour

    function window.getPaletteColour(colour)
        if type(colour) ~= "number" then expect(1, colour, "number") end
        if tHex[colour] == nil then
            error("Invalid color (got " .. colour .. ")" , 2)
        end
        local tCol = tPalette[colour]
        return tCol[1], tCol[2], tCol[3]
    end

    window.getPaletteColor = window.getPaletteColour

    local function setBackgroundColor(color)
        if type(color) ~= "number" then expect(1, color, "number") end
        if tHex[color] == nil then
            error("Invalid color (got " .. color .. ")", 2)
        end
        nBackgroundColor = color
    end

    window.setBackgroundColor = setBackgroundColor
    window.setBackgroundColour = setBackgroundColor

    function window.getSize()
        return nWidth, nHeight
    end

    function window.scroll(n)
        if type(n) ~= "number" then expect(1, n, "number") end
        if n ~= 0 then
            local tNewLines = {}
            local sEmptyText = sEmptySpaceLine
            local sEmptyTextColor = tEmptyColorLines[nTextColor]
            local sEmptyBackgroundColor = tEmptyColorLines[nBackgroundColor]
            for newY = 1, nHeight do
                local y = newY + n
                if y >= 1 and y <= nHeight then
                    tNewLines[newY] = tLines[y]
                else
                    tNewLines[newY] = {
                        text = sEmptyText,
                        textColor = sEmptyTextColor,
                        backgroundColor = sEmptyBackgroundColor,
                    }
                end
            end
            tLines = tNewLines
            if bVisible then
                redraw()
                updateCursorColor()
                updateCursorPos()
            end
        end
    end

    function window.getTextColor()
        return nTextColor
    end

    function window.getTextColour()
        return nTextColor
    end

    function window.getBackgroundColor()
        return nBackgroundColor
    end

    function window.getBackgroundColour()
        return nBackgroundColor
    end

    --- Get the buffered contents of a line in this window.
    --
    -- @tparam number y The y position of the line to get.
    -- @treturn string The textual content of this line.
    -- @treturn string The text colours of this line, suitable for use with @{term.blit}.
    -- @treturn string The background colours of this line, suitable for use with @{term.blit}.
    -- @throws If `y` is not between 1 and this window's height.
    function window.getLine(y)
        if type(y) ~= "number" then expect(1, y, "number") end

        if y < 1 or y > nHeight then
            error("Line is out of range.", 2)
        end

        return tLines[y].text, tLines[y].textColor, tLines[y].backgroundColor
    end

    -- Other functions

    --- Set whether this window is visible. Invisible windows will not be drawn
    -- to the screen until they are made visible again.
    --
    -- Making an invisible window visible will immediately draw it.
    --
    -- @tparam boolean visible Whether this window is visible.
    function window.setVisible(visible)
        if type(visible) ~= "boolean" then expect(1, visible, "boolean") end
        if bVisible ~= visible then
            bVisible = visible
            if bVisible then
                window.redraw()
            end
        end
    end

    --- Get whether this window is visible. Invisible windows will not be
    -- drawn to the screen until they are made visible again.
    --
    -- @treturn boolean Whether this window is visible.
    -- @see Window:setVisible
    function window.isVisible()
        return bVisible
    end
    --- Draw this window. This does nothing if the window is not visible.
    --
    -- @see Window:setVisible
    function window.redraw()
        if bVisible then
            redraw()
            updatePalette()
            updateCursorBlink()
            updateCursorColor()
            updateCursorPos()
        end
    end

    --- Set the current terminal's cursor to where this window's cursor is. This
    -- does nothing if the window is not visible.
    function window.restoreCursor()
        if bVisible then
            updateCursorBlink()
            updateCursorColor()
            updateCursorPos()
        end
    end

    --- Get the position of the top left corner of this window.
    --
    -- @treturn number The x position of this window.
    -- @treturn number The y position of this window.
    function window.getPosition()
        return nX, nY
    end

    --- Reposition or resize the given window.
    --
    -- This function also accepts arguments to change the size of this window.
    -- It is recommended that you fire a `term_resize` event after changing a
    -- window's, to allow programs to adjust their sizing.
    --
    -- @tparam number new_x The new x position of this window.
    -- @tparam number new_y The new y position of this window.
    -- @tparam[opt] number new_width The new width of this window.
    -- @tparam number new_height The new height of this window.
    -- @tparam[opt] term.Redirect new_parent The new redirect object this
    -- window should draw to.
    function window.reposition(new_x, new_y, new_width, new_height, new_parent)
        if type(new_x) ~= "number" then expect(1, new_x, "number") end
        if type(new_y) ~= "number" then expect(2, new_y, "number") end
        if new_width ~= nil or new_height ~= nil then
            expect(3, new_width, "number")
            expect(4, new_height, "number")
        end
        if new_parent ~= nil and type(new_parent) ~= "table" then expect(5, new_parent, "table") end

        nX = new_x
        nY = new_y

        if new_parent then parent = new_parent end

        if new_width and new_height then
            local tNewLines = {}
            createEmptyLines(new_width)
            local sEmptyText = sEmptySpaceLine
            local sEmptyTextColor = tEmptyColorLines[nTextColor]
            local sEmptyBackgroundColor = tEmptyColorLines[nBackgroundColor]
            for y = 1, new_height do
                if y > nHeight then
                    tNewLines[y] = {
                        text = sEmptyText,
                        textColor = sEmptyTextColor,
                        backgroundColor = sEmptyBackgroundColor,
                    }
                else
                    local tOldLine = tLines[y]
                    if new_width == nWidth then
                        tNewLines[y] = tOldLine
                    elseif new_width < nWidth then
                        tNewLines[y] = {
                            text = string_sub(tOldLine.text, 1, new_width),
                            textColor = string_sub(tOldLine.textColor, 1, new_width),
                            backgroundColor = string_sub(tOldLine.backgroundColor, 1, new_width),
                        }
                    else
                        tNewLines[y] = {
                            text = tOldLine.text .. string_sub(sEmptyText, nWidth + 1, new_width),
                            textColor = tOldLine.textColor .. string_sub(sEmptyTextColor, nWidth + 1, new_width),
                            backgroundColor = tOldLine.backgroundColor .. string_sub(sEmptyBackgroundColor, nWidth + 1, new_width),
                        }
                    end
                end
            end
            nWidth = new_width
            nHeight = new_height
            tLines = tNewLines
        end
        if bVisible then
            window.redraw()
        end
    end

    if bVisible then
        window.redraw()
    end
    return window
end
