util.lua

function prompt( _tOptions )
    local tVerify = {replaceChar = "string", history = "table", complete = "function", prefix = "string", limit = "number", newline = "boolean", completeBGColor = "number", completeTextColor = "number", filter = "function", customkeys = "table", writer = "function"}
    if not _tOptions then
        _tOptions = {}
    end
    for k, v in pairs(tVerify) do
        if _tOptions[k] ~= nil and type( _tOptions[k] ) ~= v then
            error( "bad argument " .. k .. " (expected " .. v .. " got ".. type( _tOptions[k] ) .. ")", 2)
        end
    end

    term.setCursorBlink( true )

    local sLine
    if type( _tOptions.prefix ) == "string" then
        sLine = _tOptions.prefix
    else
        sLine = ""
    end
    local nhistoryPos
    local nPos = #sLine
    if _tOptions.replaceChar then
        _tOptions.replaceChar = string.sub( _tOptions.replaceChar, 1, 1 )
    end
    if not _tOptions.customkeys then
        _tOptions.customkeys = {}
    end
    local tCustomKeyNames = {enter = keys.enter, up = keys.up, down = keys.down, left = keys.left, right = keys.right, backspace = keys.backspace, home = keys.home, delete = keys.delete, tab = keys.tab, ["end"] = keys["end"]}
    for k, v in pairs(tCustomKeyNames) do
        if not _tOptions.customkeys[k] then
            _tOptions.customkeys[k] = v
        end
    end

    local tCompletions
    local nCompletion
    local function recomplete()
        if _tOptions.complete and nPos == string.len(sLine) then
            tCompletions = _tOptions.complete( sLine )
            if tCompletions and #tCompletions > 0 then
                nCompletion = 1
            else
                nCompletion = nil
            end
        else
            tCompletions = nil
            nCompletion = nil
        end
    end

    local function uncomplete()
        tCompletions = nil
        nCompletion = nil
    end

    local sx = term.getCursorPos()

    local w
    if not _tOptions.limit then
        w = term.getSize()
    else
        w = _tOptions.limit+sx
    end

    local writeFunc = term.write

    if _tOptions.writer then
        writeFunc = _tOptions.writer
    end

    local function redraw( _bClear )
        local nScroll = 0
        if sx + nPos >= w then
            nScroll = (sx + nPos) - w
        end

        local cx,cy = term.getCursorPos()
        term.setCursorPos( sx, cy )
        local sReplace = (_bClear and " ") or _tOptions.replaceChar
        if sReplace then
            writeFunc( string.sub( string.rep( sReplace, math.max( string.len(sLine) + 1, 0 ) ),  nScroll + 1, nScroll + w ) )
        else
            writeFunc( string.sub( sLine, nScroll + 1, nScroll + w ) )
        end

        if nCompletion then
            local sCompletion = tCompletions[ nCompletion ]
            local oldText, oldBg
            if not _bClear then
                oldText = term.getTextColor()
                oldBg = term.getBackgroundColor()
                if not _tOptions.completeTextColor then
                    term.setTextColor( colors.white )
                else
                    term.setTextColor( _tOptions.completeTextColor )
                end
                if not _tOptions.completeBGColor then
                    term.setBackgroundColor( colors.gray )
                else
                    term.setBackgroundColor( _tOptions.completeBGColor )
                end
            end
            if sReplace then
                writeFunc( string.rep( sReplace, string.len( sCompletion ) ) )
            else
                writeFunc( sCompletion )
            end
            if not _bClear then
                term.setTextColor( oldText )
                term.setBackgroundColor( oldBg )
            end
        end

        term.setCursorPos( sx + nPos - nScroll, cy )
    end

    local function clear()
        redraw( true )
    end

    recomplete()
    redraw()

    local function acceptCompletion()
        if nCompletion then
            -- Clear
            clear()

            -- Find the common prefix of all the other suggestions which start with the same letter as the current one
            local sCompletion = tCompletions[ nCompletion ]
            sLine = sLine .. sCompletion
            nPos = string.len( sLine )

            -- Redraw
            recomplete()
            redraw()
        end
    end
    while true do
        local sEvent, param = os.pullEvent()

        if sEvent == "char" then
            -- Typed key
            clear()
            sLine = string.sub( sLine, 1, nPos ) .. param .. string.sub( sLine, nPos + 1 )
            nPos = nPos + 1
            recomplete()
            redraw()

        elseif sEvent == "paste" then
            -- Pasted text
            clear()
            sLine = string.sub( sLine, 1, nPos ) .. param .. string.sub( sLine, nPos + 1 )
            nPos = nPos + string.len( param )
            recomplete()
            redraw()

        elseif sEvent == "key" then
            if _tOptions.customkeys.enter == param then
                -- Enter
                if nCompletion then
                    clear()
                    uncomplete()
                    redraw()
                end
                break

            elseif _tOptions.customkeys.left == param then
                -- Left
                if nPos > 0 then
                    clear()
                    nPos = nPos - 1
                    recomplete()
                    redraw()
                end

            elseif _tOptions.customkeys.right == param then
                -- Right
                if nPos < string.len(sLine) then
                    -- Move right
                    clear()
                    nPos = nPos + 1
                    recomplete()
                    redraw()
                else
                    -- Accept autocomplete
                    acceptCompletion()
                end

            elseif  _tOptions.customkeys.up == param or _tOptions.customkeys.down == param then
                -- Up or down
                if nCompletion then
                    -- Cycle completions
                    clear()
                    if _tOptions.customkeys.up == param then
                        nCompletion = nCompletion - 1
                        if nCompletion < 1 then
                            nCompletion = #tCompletions
                        end
                    elseif _tOptions.customkeys.down == param then
                        nCompletion = nCompletion + 1
                        if nCompletion > #tCompletions then
                            nCompletion = 1
                        end
                    end
                    redraw()

                elseif _tOptions.history then
                    -- Cycle history
                    clear()
                    if _tOptions.customkeys.up == param then
                        -- Up
                        if nhistoryPos == nil then
                            if #_tOptions.history > 0 then
                                nhistoryPos = #_tOptions.history
                            end
                        elseif nhistoryPos > 1 then
                            nhistoryPos = nhistoryPos - 1
                        end
                    elseif _tOptions.customkeys.down == param then
                        -- Down
                        if nhistoryPos == #_tOptions.history then
                            nhistoryPos = nil
                        elseif nhistoryPos ~= nil then
                            nhistoryPos = nhistoryPos + 1
                        end
                    end
                    if nhistoryPos then
                        sLine = _tOptions.history[nhistoryPos]
                        nPos = string.len( sLine )
                    else
                        sLine = ""
                        nPos = 0
                    end
                    uncomplete()
                    redraw()

                end

            elseif _tOptions.customkeys.backspace == param then
                -- Backspace
                if nPos > 0 then
                    clear()
                    sLine = string.sub( sLine, 1, nPos - 1 ) .. string.sub( sLine, nPos + 1 )
                    nPos = nPos - 1
                    recomplete()
                    redraw()
                end

            elseif _tOptions.customkeys.home == param then
                -- Home
                if nPos > 0 then
                    clear()
                    nPos = 0
                    recomplete()
                    redraw()
                end

            elseif _tOptions.customkeys.delete == param then
                -- Delete
                if nPos < string.len(sLine) then
                    clear()
                    sLine = string.sub( sLine, 1, nPos ) .. string.sub( sLine, nPos + 2 )
                    recomplete()
                    redraw()
                end

            elseif _tOptions.customkeys["end"] == param then
                -- End
                if nPos < string.len(sLine ) then
                    clear()
                    nPos = string.len(sLine)
                    recomplete()
                    redraw()
                end

            elseif _tOptions.customkeys.tab == param then
                -- Tab (accept autocomplete)
                acceptCompletion()

            end

        elseif sEvent == "term_resize" then
            -- Terminal resized
            if not _tOptions.limit then
                w = term.getSize()
            else
                w = _tOptions.limit
            end
            redraw()

        end

        if _tOptions.filter then
            -- Filter out all unwanted characters/strings using a function defined by the user
            local sPreFilterLine = sLine
            sLine = _tOptions.filter( sLine )
            if string.len( sPreFilterLine ) ~= string.len( sLine ) then
                local sPreClearLine = sLine
                sLine = sPreFilterLine
                clear()
                sLine = sPreClearLine
            end
            if not sLine then
                sLine = sPreFilterLine
            else
                if nPos >= ( string.len( sPreFilterLine ) - string.len( sLine ) ) then
                    nPos = nPos - ( string.len( sPreFilterLine ) - string.len( sLine ) )
                else
                    nPos = 0
                end
            end
            redraw()
        end
    end

    local cx, cy = term.getCursorPos()
    term.setCursorBlink( false )
    if _tOptions.newline == nil or _tOptions.newline == true then
        term.setCursorPos( 1, cy + 1)
    end

    return sLine
end