-- Paint created by nitrogenfingers (edited by dan200)
-- http://www.youtube.com/user/NitrogenFingers

------------
-- Fields --
------------

-- The width and height of the terminal
local w,h = term.getSize()

-- The selected colours on the left and right mouse button, and the colour of the canvas
local leftColour, rightColour = colours.white, nil
local canvasColour = colours.black

-- The values stored in the canvas
local canvas = {}

-- The menu options
local mChoices = { "Save","Exit" }

-- The message displayed in the footer bar
local fMessage = "Press Ctrl to access menu"

-------------------------
-- Initialisation --
-------------------------

-- Determine if we can even run this
if not term.isColour() then
    print("Requires an Advanced Computer")
    return
end

-- Determines if the file exists, and can be edited on this computer
local tArgs = {...}
if #tArgs == 0 then
    print("Usage: paint <path>")
    return
end
local sPath = shell.resolve(tArgs[1])
local bReadOnly = fs.isReadOnly(sPath)
if fs.exists(sPath) and fs.isDir(sPath) then
    print("Cannot edit a directory.")
    return
end

---------------
-- Functions --
---------------

local function getCanvasPixel( x, y )
    if canvas[y] then
        return canvas[y][x]
    end
    return nil
end

--[[
    Converts a colour value to a text character
    params: colour = the number to convert to a hex value
    returns: a string representing the chosen colour
]]
local function getCharOf( colour )
    -- Incorrect values always convert to nil
    if type(colour) == "number" then
        local value = math.floor( math.log(colour) / math.log(2) ) + 1
        if value >= 1 and value <= 16 then
            return string.sub( "0123456789abcdef", value, value )
        end
    end
    return " "
end

--[[
    Converts a text character to colour value
    params: char = the char (from string.byte) to convert to number
    returns: the colour number of the hex value
]]
local tColourLookup = {}
for n=1,16 do
    tColourLookup[ string.byte( "0123456789abcdef",n,n ) ] = 2^(n-1)
end
local function getColourOf( char )
    -- Values not in the hex table are transparent (canvas coloured)
    return tColourLookup[char]
end

--[[
    Loads the file into the canvas
    params: path = the path of the file to open
    returns: nil
]]
local function load(path)
    -- Load the file
    if fs.exists(path) then
        local file = fs.open(sPath, "r")
        local sLine = file.readLine()
        while sLine do
            local line = {}
            for x=1,w-2 do
                line[x] = getColourOf( string.byte(sLine,x,x) )
            end
            table.insert( canvas, line )
            sLine = file.readLine()
        end
        file.close()
    end
end

--[[
    Saves the current canvas to file
    params: path = the path of the file to save
    returns: true if save was successful, false otherwise
]]
local function save(path)
    -- Open file
    local sDir = string.sub(sPath, 1, #sPath - #fs.getName(sPath))
    if not fs.exists(sDir) then
        fs.makeDir(sDir)
    end

    local file = fs.open( path, "w" )
    if not file then
        return false
    end

    -- Encode (and trim)
    local tLines = {}
    local nLastLine = 0
    for y=1,h-1 do
        local sLine = ""
        local nLastChar = 0
        for x=1,w-2 do
            local c = getCharOf( getCanvasPixel( x, y ) )
            sLine = sLine .. c
            if c ~= " " then
                nLastChar = x
            end
        end
        sLine = string.sub( sLine, 1, nLastChar )
        tLines[y] = sLine
        if string.len( sLine ) > 0 then
            nLastLine = y
        end
    end

    -- Save out
    for n=1,nLastLine do
           file.writeLine( tLines[ n ] )
    end
    file.close()
    return true
end

--[[
    Draws colour picker sidebar, the pallette and the footer
    returns: nil
]]
local function drawInterface()
    -- Footer
    term.setCursorPos(1, h)
    term.setBackgroundColour(colours.black)
    term.setTextColour(colours.yellow)
    term.clearLine()
    term.write(fMessage)

    -- Colour Picker
    for i=1,16 do
        term.setCursorPos(w-1, i)
        term.setBackgroundColour( 2^(i-1) )
        term.write("  ")
    end

    term.setCursorPos(w-1, 17)
    term.setBackgroundColour( canvasColour )
    term.setTextColour( colours.grey )
    term.write("XX")

    -- Left and Right Selected Colours
    for i=18,18 do
        term.setCursorPos(w-1, i)
        if leftColour ~= nil then
            term.setBackgroundColour( leftColour )
            term.write(" ")
        else
            term.setBackgroundColour( canvasColour )
            term.setTextColour( colours.grey )
            term.write("X")
        end
        if rightColour ~= nil then
            term.setBackgroundColour( rightColour )
            term.write(" ")
        else
            term.setBackgroundColour( canvasColour )
            term.setTextColour( colours.grey )
            term.write("X")
        end
    end

    -- Padding
    term.setBackgroundColour( canvasColour )
    for i=20,h-1 do
        term.setCursorPos(w-1, i)
        term.write("  ")
    end
end

--[[
    Converts a single pixel of a single line of the canvas and draws it
    returns: nil
]]
local function drawCanvasPixel( x, y )
    local pixel = getCanvasPixel( x, y )
    if pixel then
        term.setBackgroundColour( pixel or canvasColour )
        term.setCursorPos(x, y)
        term.write(" ")
    else
        term.setBackgroundColour( canvasColour )
        term.setTextColour( colours.grey )
        term.setCursorPos(x, y)
        term.write("-")
    end
end

--[[
    Converts each colour in a single line of the canvas and draws it
    returns: nil
]]
local function drawCanvasLine( y )
    for x = 1, w-2 do
        drawCanvasPixel( x, y )
    end
end

--[[
    Converts each colour in the canvas and draws it
    returns: nil
]]
local function drawCanvas()
    for y = 1, h-1 do
        drawCanvasLine( y )
    end
end

--[[
    Draws menu options and handles input from within the menu.
    returns: true if the program is to be exited; false otherwise
]]
local function accessMenu()
    -- Selected menu option
    local selection = 1

    term.setBackgroundColour(colours.black)
    while true do
        -- Draw the menu
        term.setCursorPos(1,h)
        term.clearLine()
        term.setTextColour(colours.white)
        for k,v in pairs(mChoices) do
            if selection==k then
                term.setTextColour(colours.yellow)
                local ox,_ = term.getCursorPos()
                term.write("["..string.rep(" ",#v).."]")
                term.setCursorPos(ox+1,h)
                term.setTextColour(colours.white)
                term.write(v)
                term.setCursorPos(term.getCursorPos()+1,h)
            else
                term.write(" "..v.." ")
            end
        end

        -- Handle input in the menu
        local id,key = os.pullEvent("key")
        if id == "key" then
            -- S and E are shortcuts
            if key == keys.s then
                selection = 1
                key = keys.enter
            elseif key == keys.e then
                selection = 2
                key = keys.enter
            end

            if key == keys.right then
                -- Move right
                selection = selection + 1
                if selection > #mChoices then
                    selection = 1
                end

            elseif key == keys.left and selection > 1 then
                -- Move left
                selection = selection - 1
                if selection < 1 then
                    selection = #mChoices
                end

            elseif key == keys.enter then
                -- Select an option
                if mChoices[selection]=="Save" then
                    if bReadOnly then
                        fMessage = "Access Denied"
                        return false
                    end
                    local success = save(sPath)
                    if success then
                        fMessage = "Saved to "..sPath
                    else
                        fMessage = "Error saving to "..sPath
                    end
                    return false
                elseif mChoices[selection]=="Exit" then
                    return true
                end
            elseif key == keys.leftCtrl or keys == keys.rightCtrl then
                -- Cancel the menu
                return false
            end
        end
    end
end

--[[
    Runs the main thread of execution. Draws the canvas and interface, and handles
    mouse and key events.
    returns: nil
]]
local function handleEvents()
    local programActive = true
    while programActive do
        local id,p1,p2,p3 = os.pullEvent()
        if id=="mouse_click" or id=="mouse_drag" then
            if p2 >= w-1 and p3 >= 1 and p3 <= 17 then
                if id ~= "mouse_drag" then
                    -- Selecting an items in the colour picker
                    if p3 <= 16 then
                        if p1==1 then
                            leftColour = 2^(p3-1)
                        else
                            rightColour = 2^(p3-1)
                        end
                    else
                        if p1==1 then
                            leftColour = nil
                        else
                            rightColour = nil
                        end
                    end
                    --drawCanvas()
                    drawInterface()
                end
            elseif p2 < w-1 and p3 <= h-1 then
                -- Clicking on the canvas
                local paintColour = nil
                if p1==1 then
                    paintColour = leftColour
                elseif p1==2 then
                    paintColour = rightColour
                end
                if not canvas[p3] then
                    canvas[p3] = {}
                end
                canvas[p3][p2] = paintColour

                drawCanvasPixel( p2, p3 )
            end
        elseif id=="key" then
            if p1==keys.leftCtrl or p1==keys.rightCtrl then
                programActive = not accessMenu()
                drawInterface()
            end
        elseif id=="term_resize" then
            w,h = term.getSize()
            drawCanvas()
            drawInterface()
        end
    end
end

-- Init
load(sPath)
drawCanvas()
drawInterface()

-- Main loop
handleEvents()

-- Shutdown
term.setBackgroundColour(colours.black)
term.setTextColour(colours.white)
term.clear()
term.setCursorPos(1,1)