Modify selected text length automator applescript

--Installation: Create an Automator service, paste this code into a "Run AppleScript" action, and save.
--How to use it: 1. Copy a number indicating the length you want the selection to be. 2. Select the region of text where you want the copied length to be selected. 3. Right-click the selection and select this service

--NOTES:
--If the contents of the clipboard is not a number, you'll be prompted to enter a length, although this feature has not been tested.
--If input is not supplied, this script will backup the current clipboard, copy the current selection to get the currently selected text, then restore the clipboard.

on run {input, parameters}

    try
        set debug to false
        if input's class is not list then
            set input to getHighlight(debug)
        end if

        tell application "System Events"
            --See if the clipboard has a number in it to use for the selection length
            set checkClipboard to the clipboard as text
            if my isNumString(checkClipboard) then
                set n to checkClipboard as integer
            else
                set n to my getintvalue()
            end if

            --Check the length of the selected text passed in
            set character_count to count characters of ((input as string) as string)

            set lengthen to false
            set mod_length to 0
            if character_count is equal to 0 or n is greater than character_count then
                set lengthen to true
                set mod_length to n - character_count
            else
                set mod_length to character_count - n
            end if

            --See if we're in Terminal
            set isTerminal to ((name of first process where it is frontmost) as string) is equal to "Terminal"

            if isTerminal is true then
                if lengthen is true then
                    set substr to (input as string)
                    repeat mod_length times
                        set substr to substr & "N"
                    end repeat
                    set substr to " <- " & n
                else
                    set substr to text 1 thru n of (input as string)
                    set substr to substr & " <- " & n & " "
                    set substr to substr & (text (n + 1) thru character_count of (input as string))
                end if
                display dialog "Position " & n & " is marked below:" & return & return & substr buttons {"OK"}
            else
                --Figure out whether the selection must be lengthened or shrunk
                if not (character_count is equal to 0 or n is greater than character_count) then
                    key code 124 using {shift down}
                    key code 123 using {shift down}
                end if

                repeat mod_length times
                    if lengthen is true then
                        key code 124 using {shift down}
                    else
                        key code 123 using {shift down}
                    end if
                end repeat
            end if
        end tell
    on error errstr
        display dialog errstr
    end try

end run



property mytitle : "Length of text to select"

-- I am asking the user to provide an integer
-- In case the user cancels the dialog, I return «missing value»
on getintvalue()
    set dlgmsg to "How many characters would you like to select?:"
    try
        display dialog dlgmsg default answer "1" buttons {"Cancel", "Enter"} default button 2 with title mytitle
    on error
        -- User canceled
        return missing value
    end try
    set dlgresult to result
    set usrinput to text returned of dlgresult
    -- the user did not enter anything...
    if usrinput is "" then
        my getintvalue()
    else
        -- let's check if the user entered numbers only
        set nums to {"1", "2", "3", "4", "5", "6", "7", "8", "9", "0"}
        set invalidchars to ""
        repeat with char in usrinput
            if char is not in nums then
                set invalidchars to invalidchars & char & space
            end if
        end repeat
        -- we found invalid characters
        if invalidchars is not "" then
            set errmsg to "We found the following characters in the given input. Please enter numbers only." & return & return & invalidchars & return
            my dsperrmsg(errmsg, "--")
            my getintvalue()
        else
            -- let's try to transform the user input into an integer
            try
                set intvalue to usrinput as integer
                return intvalue
            on error
                set errmsg to "We could not coerce the given input into an integer:" & return & return & usrinput & return
                my dsperrmsg(errmsg, "--")
                my getintvalue()
            end try
        end if
    end if
end getintvalue

-- I am displaying error messages to the user
on dsperrmsg(errmsg, errnum)
    tell me
        activate
        display dialog errmsg & " (" & errnum & ")" buttons {"OK"} default button 1 with title mytitle with icon stop
    end tell
end dsperrmsg

-- isNumString :: String -> Bool
on isNumString(s)
    try
        if class of s is string then
            set c to class of (s as number)
            c is real or c is integer
        else
            false
        end if
    on error
        false
    end try
end isNumString

on getHighlight(debug)

    --Save the current contents of the clipboard
    try
        set theSpare to the clipboard --as text
    on error
        set response to (display dialog "Warning: The contents of the clipboard will be lost." buttons {"Cancel", "OK"})
        if button returned of response is "OK" then
            set theSpare to ""
        end if
    end try
    set the clipboard to ""
    --Declare the variable we're going to return
    set selecTxt to ""

    tell application "System Events"
        --Initiate the copy
        keystroke "c" using {command down}

        --Wait up to 2 seconds for the copy to finish
        set done to "no"
        set waitnum to 0
        set waitInterval to 0.02
        set maxwaits to 100

        --Repeat while the clipboard contents have not changed
        repeat while done = "no"
            --Get the contents of the clipboard
            try
                set selecTxt to the clipboard as text
            end try

            --See if we're done or need to wait
            if waitnum is equal to maxwaits then
                set done to "yes"
            else if selecTxt is equal to "" then
                delay waitInterval
                set waitnum to waitnum + 1
            else
                set done to "yes"
            end if

        end repeat

        if debug is true then
            try
                display dialog "Copied text: " & (the clipboard as text)
            end try
        end if
    end tell

    --Restore the original clipboard contents
    set the clipboard to theSpare --as record

    if debug is true then
        try
            display dialog "The clipboard contents have been restored to " & (the clipboard as text)
        end try
    end if

    --Return the highlighted text
    return selecTxt

end getHighlight