[ComputerCraft][Code Snippet] Modified Reading Function

--[[
    [Code Snippet] Modified Reading Function
    @version 0.9, 2014-09-01
    @author TheOddByte



    Features:
        Placeholder text
        Text limit
        Ability to mark text
        Block unwanted characters

    Todo:
        Add keyboard support for CTRL+A, CTRL+C etc. kinda obvious what it's for right?
        Scrollable text, ( fooba > oobar )
--]]

local function mRead( properties )

    local placeholder, text_limit, width, mask, cursor_blink, blocked_chars, allowed_chars, marker
    local properties = properties or {}
    placeholder   = properties.placeholder.text and properties.placeholder or nil
    text_limit    = properties.text_limit
    width         = properties.width
    mask          = properties.mask
    blocked_chars = properties.blocked_chars
    allowed_chars = properties.allowed_chars
    cursor_blink  = properties.cursor_blink or true
    marker        = properties.marker


    term.setCursorBlink( cursor_blink )
    local x, y = term.getCursorPos()
    local text, pos, sPos, fPos, selected, mark, mx = "", 0, 0, 0, false, false

    local function redraw()
        pcall( term.setTextColor, properties.native_text_color )
        pcall( term.setBackgroundColor, properties.native_background_color )
        term.setCursorPos( x, y )
        term.write( string.rep( " ", #text + 1 ) )
    end




    while true do

        --# Format text( remove blocked characters )
        if blocked_chars then
            for i = 1, #blocked_chars do
                text = text:gsub( blocked_chars:sub( i, i ), "" )
            end
        end
        if allowed_chars then
            local _text = ""
            for i = 1, #text do
                for k = 1, #allowed_chars do
                    if text:sub( i,i ) == allowed_chars:sub( k, k ) then
                        _text = _text .. text:sub( i,i )
                        break
                    end
                end
            end
            text = _text
        end
        if pos > #text then
            pos = #text
        end


        --# Redraw text
        term.setCursorPos( x + #text, y )
        term.write( " " )
        term.setCursorPos( x, y )
        if placeholder then
            if #text == 0 then
                if placeholder.text_color then
                    pcall( term.setTextColor, placeholder.text_color )
                end
                term.setCursorBlink( placeholder.cursor_blink or true )
            else
                if properties.native_text_color then
                    pcall( term.setTextColor, properties.native_text_color )
                end
            end
            if mask then
                term.write( #text > 0 and string.rep( mask:sub(1,1), #text ) or placeholder.text )
            else
                term.write( #text > 0 and text or placeholder.text )
            end
        else
            term.write( mask and string.rep( mask:sub(1,1), #text ) or text )
        end
        if selected then
            term.setCursorBlink( false )
            pcall( term.setTextColor, marker.text_color )
            pcall( term.setBackgroundColor, marker.background_color )
            local str = ""
            for i = sPos, fPos do
                str = str .. text:sub( i, i )
            end
            term.setCursorPos( x + (sPos-1), y )
            term.write( mask and string.rep( mask, #str ) or str )
            pcall( term.setTextColor, properties.native_text_color )
            pcall( term.setBackgroundColor, properties.native_background_color )
        else
            term.setCursorBlink( cursor_blink )
        end
        term.setCursorPos( placeholder and #text > 0 and x + pos or x + #placeholder.text, y )



        --# Handle events
        local e = { os.pullEvent() }
        if e[1] == "char" then
            if placeholder.text and #text == 0 then
                for i = 1, #placeholder.text do
                    term.setCursorPos( x + (i-1), y )
                    term.write( " " )
                end
            end
            if not text_limit then
                if not selected then
                    text = text:sub( 1, pos ) .. e[2] .. text:sub( pos + 1 )
                    pos = pos + 1
                else
                    redraw()
                    text = text:sub( 1, sPos - 1 ) .. e[2] .. text:sub( fPos + 1 )
                    pos = sPos
                    selected = false
                end
            else
                if #text < text_limit then
                    if not selected then
                        text = text:sub( 1, pos ) .. e[2] .. text:sub( pos + 1 )
                        pos = pos + 1
                    else
                        redraw()
                        text = text:sub( 1, sPos - 1 ) .. e[2] .. text:sub( fPos + 1 )
                        pos = sPos
                        selected = false
                    end
                end
            end

        elseif e[1] == "key" then
            if e[2] == 14 then
                if selected then
                    redraw()
                    text = text:sub( 1, sPos - 1 ) .. text:sub( fPos + 1 )
                    selected = false
                    pos = sPos - 1
                else
                    if #text > 0 and pos > 0 then
                        text = text:sub( 1, pos - 1 ) .. text:sub( pos + 1 )
                        pos = pos - 1
                    end
                end

            elseif e[2] == keys.left then
                selected = false
                pos = pos > 0 and pos - 1 or pos

            elseif e[2] == keys.right then
                selected = false
                pos = pos < #text and pos + 1 or pos

            elseif e[2] == 28 then
                return text
            end

        elseif e[1] == "mouse_click" then
            if e[3] >= x and e[3] <= x + #text and e[4] == y then
                pos = e[3] - x
                mark = true
                mx = e[3]
            else
                mx = nil
                mark = false
            end
            selected = false

        elseif e[1] == "mouse_drag" then
            if mark then
                selected = true;
                if e[3] == mx then
                    selected = false
                else
                    selected = true
                    if e[3] >= x and e[3] <= x + #text then
                        if e[3] < mx then
                            sPos = (e[3] - x) + 1;
                            fPos = (mx - x) + 1;
                        elseif e[3] > mx then
                            sPos = (mx - x) + 1;
                            fPos = (e[3] - x) + 1;
                        end
                    else
                        if mx == x + #text then
                            if e[3] > x + #text then
                                selected = false;
                            end
                        end
                    end
                end
            end
        end
    end
end



--[[
    Example usage

    local text = mRead({ native_text_color = colors.white, native_background_color = colors.black, placeholder = { text = "Input numbers", text_color = colors.lightGray}, text_limit = 10, allowed_chars = "0123456789", marker = { text_color = colors.white, background_color = colors.blue } })

--]]