question

function read( _sReplaceChar, _tHistory )
    term.setCursorBlink( true )

    local sLine = ""
    local nHistoryPos
    local nPos = 0
    if _sReplaceChar then
        _sReplaceChar = string.sub( _sReplaceChar, 1, 1 )
    end

    local w = term.getSize()
    local sx = term.getCursorPos()

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

        local cx,cy = term.getCursorPos()
        term.setCursorPos( sx, cy )
        local sReplace = _sCustomReplaceChar or _sReplaceChar
        if sReplace then
            term.write( string.rep( sReplace, math.max( string.len(sLine) - nScroll, 0 ) ) )
        else
            term.write( string.sub( sLine, nScroll + 1 ) )
        end
        term.setCursorPos( sx + nPos - nScroll, cy )
    end

    while true do
        local sEvent, param = os.pullEvent()
        if sEvent == "char" then
            -- Typed key
            sLine = string.sub( sLine, 1, nPos ) .. param .. string.sub( sLine, nPos + 1 )
            nPos = nPos + 1
            redraw()

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

        elseif sEvent == "key" then
            if param == keys.enter then
                -- Enter
                break

            elseif param == keys.left then
                -- Left
                if nPos > 0 then
                    nPos = nPos - 1
                    redraw()
                end

            elseif param == keys.right then
                -- Right                
                if nPos < string.len(sLine) then
                    redraw(" ")
                    nPos = nPos + 1
                    redraw()
                end

            elseif param == keys.up or param == keys.down then
                -- Up or down
                if _tHistory then
                    redraw(" ")
                    if param == keys.up then
                        -- Up
                        if nHistoryPos == nil then
                            if #_tHistory > 0 then
                                nHistoryPos = #_tHistory
                            end
                        elseif nHistoryPos > 1 then
                            nHistoryPos = nHistoryPos - 1
                        end
                    else
                        -- Down
                        if nHistoryPos == #_tHistory then
                            nHistoryPos = nil
                        elseif nHistoryPos ~= nil then
                            nHistoryPos = nHistoryPos + 1
                        end                        
                    end
                    if nHistoryPos then
                        sLine = _tHistory[nHistoryPos]
                        nPos = string.len( sLine ) 
                    else
                        sLine = ""
                        nPos = 0
                    end
                    redraw()
                end
            elseif param == keys.backspace then
                -- Backspace
                if nPos > 0 then
                    redraw(" ")
                    sLine = string.sub( sLine, 1, nPos - 1 ) .. string.sub( sLine, nPos + 1 )
                    nPos = nPos - 1                    
                    redraw()
                end
            elseif param == keys.home then
                -- Home
                redraw(" ")
                nPos = 0
                redraw()        
            elseif param == keys.delete then
                -- Delete
                if nPos < string.len(sLine) then
                    redraw(" ")
                    sLine = string.sub( sLine, 1, nPos ) .. string.sub( sLine, nPos + 2 )                
                    redraw()
                end
            elseif param == keys["end"] then
                -- End
                redraw(" ")
                nPos = string.len(sLine)
                redraw()
            end

        elseif sEvent == "term_resize" then
            -- Terminal resized
            w = term.getSize()
            redraw()

        end
    end

    local cx, cy = term.getCursorPos()
    term.setCursorBlink( false )
    term.setCursorPos( w + 1, cy )
    print()

    return sLine
end