--[[

ed v0.3
by KinoftheFlames

ed is an IDE intended to replace the native file editor "edit".
The goal of this program is to make editting lua programs for ComputerCraft as fluid as possible.

For more info: http://www.computercraft.info/forums2/index.php?/topic/4270-wip-in-game-ideedit-program/

CONTROLS:
F3 - Save
F4 - Exit
F5 - Run
F6 - Run with arguments

CHANGELOG for v0.3:
I've added some more customizable options for the UI, which you can change by editting the settings variables at the top of ed's file.

- Added insertion/overwrite toggle
- Added status bar (optional) with the following information (which is all optional):
   -- Current line number
   -- Total line count (off by default)
   -- Insert/overwrite toggle display
- Added debugging. The file no longer needs to be force-saved to run it, and if there are any run-time errors ed will move the cursor to the error line and display the error.
- You can now run ed from ed as recursively as you'd like and everything should work properly (yo dawg!)
- Added auto-tabbing
- Trying to edit files in non-existant directories now creates those directories
- Added settings menu, you can finally customize the UI without editing the code!.
   -- Press F1 to access it, then use the arrow keys and space/enter to interact.
- Settings will automatically save on menu exit and load with the program - change it once and you're good!


Future features:
- Find and replace
- Goto line

]]

--argument handling
local arg = { ... }
if #arg == 0 then --verify argument exists
    print("Syntax: editor <path>")
    error()
end
if fs.isDir(arg[1]) then --verift not a directory
    print("Error: cannot edit a directory as a file")
    error()
end

--debug
local bDebug = true --display debugging info if true
local bClearDebug = false --determines if debug is cleared from screen every loop or not
local sDebugText = "" --debug text shown if debugging is on

--constants
local SCREEN_ORIGIN = 1 --top left of screen
local SCREEN_WIDTH, SCREEN_HEIGHT = term.getSize() --width and height of screen
local TIMER_INTERVAL = 300.0 --in seconds (DO NOT SET TO 0, that would be infinite)
local SETTINGS_FILEPATH = ".ed_settings" --where user settings are located

--settings (defaults)
local bShowLineNum = true --toggle visibility of line numbers
local bShowLineNumSep = true --toggle visibility of line numbers seperator
local bShowStatusBar = true --toggle visibility of the line of information at the bottom of the screen
    --toggle visibility of individual status information
    local bStatus_lineNum = true
    local bStatus_lineCount = false
    local bStatus_insert = true
local bShowMessages = true --toggle displaying of messages at the bottom of the screen
local nMinLineDigitsVisible = 1 --[POS] defines how much area for the line numbers is displayed at minimum (program will expand space as needed)
local nSpacesPerTab = 3 --[POS] defines how many visual spaces are in a tab

--toggles
local bInsert = true --insert text if true, override text if false

--flags
local bUnsavedChanges = false --tracks whether the file in the editor has been changed since last saved, helps with exit before saving confirmation
local bConfirmingExit = false --if the user tries to exit without saving, this requires them to try again before succeeding

--variables
local bRunning = true --false when the program exits
local sFilepath = arg[1] --path to the file being editted
local tFile = { } --table of lines for the file being editted
local xMin, yMin = SCREEN_ORIGIN, SCREEN_ORIGIN --min values for file display
local xMax, yMax = SCREEN_WIDTH, SCREEN_HEIGHT --max values for file display
local xFile, yFile = 1, 1 --the location of the cursor in the text file
local xScroll, yScroll = 0, 0 --amount file is scrolled on screen
local sStatus = "" --text displayed for the status bar at the bottom of the screen
local sMessage = "" --message displayed at the bottom of the screen until next input
local sArguments = "" --stores the last arguments used, bringing them up again when run w/ arguments is called
local sError = "" --stores error information from failed program execution for debugging
local tTimer --timer for main loop and time-based events

------------------------
--      EXTERNAL      --
------------------------

--converts a string to a boolean
function toboolean(value)
    if value == "true" then return true end
    if value == "false" then return false end
end



------------------------
--    FILE HANDLING   --
------------------------

--load a file from hdd into editor
function load()
    --error handling file
    if fs.exists(sFilepath) then
        --load file
        local file = fs.open(sFilepath, "r")
        while true do
            local line = file.readLine()
            if line == nil then --if reached end of file
                break end

            table.insert(tFile, line)
        end
        file.close()
    else
        table.insert(tFile, "")
    end
end

--save editor's text to a file
function save()
    sMessage = "SAVING..."
    draw()

    if bUnsavedChanges then --only save if needed (saves on CPU time)
        --create directory if it doesn't exist
        local dir = string.sub(sFilepath, 1, #sFilepath - #fs.getName(sFilepath))
        if not fs.exists(dir) then
            fs.makeDir(dir) end

        --write to file
        local file = fs.open(sFilepath, "w")
        for i,line in ipairs(tFile) do
            file.writeLine(line) end
        file.close()
    end

    sMessage = "SAVED to " .. sFilepath
    bUnsavedChanges = false
end

function loadSettings()
    if fs.exists(SETTINGS_FILEPATH) and not fs.isDir(SETTINGS_FILEPATH) then
        file = fs.open(SETTINGS_FILEPATH, "r")

        --load settings
        while true do
            local line = file.readLine()
            if line == nil then --EOF
                break end
            local v1, v2 = string.find(line, " = ") --finds delimitter location
            local var = string.sub(line, 1, v1-1) --name of variable
            local value = string.sub(line, v2+1) --value of variable

            if var == "bShowLineNum" then bShowLineNum = toboolean(value) end
            if var == "bShowLineNumSep" then bShowLineNumSep = toboolean(value) end
            if var == "bShowStatusBar" then bShowStatusBar = toboolean(value) end
            if var == "bStatus_lineNum" then bStatus_lineNum = toboolean(value) end
            if var == "bStatus_lineCount" then bStatus_lineCount = toboolean(value) end
            if var == "bStatus_insert" then bStatus_insert = toboolean(value) end
            if var == "bShowMessages" then bShowMessages = toboolean(value) end
            if var == "nMinLineDigitsVisible" then nMinLineDigitsVisible = tonumber(value) end
            if var == "nSpacesPerTab" then nSpacesPerTab = tonumber(value) end
        end

        file.close()
    end
end

function saveSettings()
    if fs.isDir(SETTINGS_FILEPATH) then --if a dir with settings filepath exists, delete it (sorry!)
        fs.delete(SETTINGS_FILEPATH)
    end

    file = fs.open(SETTINGS_FILEPATH, "w")

    --save settings
    file.writeLine("bShowLineNum = "..tostring(bShowLineNum))
    file.writeLine("bShowLineNumSep = "..tostring(bShowLineNumSep))
    file.writeLine("bShowStatusBar = "..tostring(bShowStatusBar))
    file.writeLine("bStatus_lineNum = "..tostring(bStatus_lineNum))
    file.writeLine("bStatus_lineCount = "..tostring(bStatus_lineCount))
    file.writeLine("bStatus_insert = "..tostring(bStatus_insert))
    file.writeLine("bShowMessages = "..tostring(bShowMessages))
    file.writeLine("nMinLineDigitsVisible = "..tostring(nMinLineDigitsVisible))
    file.writeLine("nSpacesPerTab = "..tostring(nSpacesPerTab))

    file.close()
    sMessage = "Settings saved"
end


------------------------
--       VISUAL       --
------------------------

--scrolls the screen with the cursor
function scroll()
    alignCursor()
    local x,y = term.getCursorPos()

    if y > yMax then
        yScroll = yScroll + (y - yMax)
    elseif y < yMin then
        yScroll = yScroll - (yMin - y)
    end
    if x > xMax then
        xScroll = xScroll + (x - xMax)
    elseif x < xMin then
        xScroll = xScroll - (xMin - x)
    end
end

--brings the visual cursor to the location of the cursor in file
function alignCursor()
    local charsLeftOfCursor = string.sub(tFile[yFile], 1, xFile-1) --chars left of cursor
    local dummy, numTabs = string.gsub(charsLeftOfCursor, "\t", "\t") --gets the number of tabs

    local x = xMin + (xFile - 1) - xScroll + numTabs * (nSpacesPerTab - 1)
    local y = yMin + (yFile - 1) - yScroll

    term.setCursorPos(x, y)
end

--moves cursor around
function shiftCursor(xShift, yShift)
    --format input for error handling
    if yFile + yShift < 1 then
        yShift = -(yFile - 1)
    elseif yFile + yShift > #tFile then
        yShift = #tFile - yFile
    end


    --handle left/right movement
    if xFile == 1 and xShift < 0 then --if at start of line and moving left, move to end of above line (if exists)
        if yFile ~= 1 then
            xFile = #tFile[yFile-1] + 1
            yFile = yFile - 1
        end
    elseif xFile > #tFile[yFile] and xShift > 0 then --if at end of line and moving right, move to start of next line (if exists)
        if yFile ~= #tFile then
            xFile = 1
            yFile = yFile + 1
        end
    else --horizontal only movement
        xFile = xFile + xShift--normal move
    end

    --handle up/down movement
    if yFile == 1 and yShift < 0 then --if at first line and moving up, move to start of line
        xFile = 1
    elseif yFile == #tFile and yShift > 0 then --if at last line and moving down, move to end of line
        xFile = #tFile[yFile] + 1
    else --vertical only movement
        yFile = yFile + yShift --normal move

        --if the cursor is past the end of the last character after having moved, move it to the last character
        if xFile > #tFile[yFile] then
            xFile = 1 + #tFile[yFile]
        end
    end
end

--move cursor to the start of the line
function shiftCursorHome()
    xFile = 1
end

--move cursor to the end of the line (end of text)
function shiftCursorEnd()
    xFile = 1 + #tFile[yFile]
end

--adjusts borders of editable area depending on settings and situational factors
function applyBoundrySettings()
    if bShowLineNum then
        local chars = #tostring(#tFile) --characters in line num area = num of digits of last line
        if nMinLineDigitsVisible > chars then --unless there is a minimum character count to enforce which is greater
            chars = nMinLineDigitsVisible end
        xMin = chars + 2 --adjust boundry for editable area
    else
        xMin = SCREEN_ORIGIN end

    if bShowStatusBar then
        yMax = SCREEN_HEIGHT - 1
    else
        yMax = SCREEN_HEIGHT end
end



------------------------
--      DRAWING       --
------------------------

--redraws entire screen
function draw()
    --clear screen
    term.clear()

    --draw line numbers
    if bShowLineNum then
        drawLineNum() end

    --draw file text
    for i=yMin,yMax do
        if tFile[i+yScroll] ~= nil then --if haven't reached end of file
            term.setCursorPos(xMin, i)
            local modifiedLine = string.gsub(tFile[i+yScroll], "\t", string.rep(" ", nSpacesPerTab)) --replace visual line's tab characters with defined num of spaces
            term.write(string.sub(modifiedLine, 1 + xScroll, xMax - xMin + 1 + xScroll)) --only draw visible text
        end
    end

    --draw status bar
    if bShowStatusBar then
        drawStatusBar() end

    --draw message
    if bShowMessages then
        drawMessage() end

    --draw debug
    if bDebug then
        drawDebug(sDebugText) end

    --place visual cursor in correct position
    alignCursor()
end

--draws line numbers and seperator
function drawLineNum()
    applyBoundrySettings()
    local chars = #tostring(#tFile) --characters in line num area = num of digits of last line
    if nMinLineDigitsVisible > chars then --unless there is a minimum character count to enforce which is greater
        chars = nMinLineDigitsVisible end

    for i=yMin,yMax do
        local lineNum = i+yScroll --line number of file line being drawn
        if tFile[lineNum] ~= nil then --don't draw line numbers for lines that dont exists in the file
            local numSpaces = chars - #tostring(lineNum) --spaces required to right-align numbers

            --draw finally
            term.setCursorPos(SCREEN_ORIGIN, i)
            term.write(string.rep(" ", numSpaces)) --spaces before line number
            term.write(tostring(lineNum)) --line number
            if bShowLineNumSep then
                term.write("|") end --seperator --TODO: add customizable line seperator (single char)
        end
    end

    --sDebugText = sDebugText .. " xMin:"..xMin
end

--draw bar with information at the bottom of the screen
function drawStatusBar()
    sStatus = "--< " --paint me like one of your french girls

    local charsLeft = SCREEN_WIDTH - 8 --characters available to print
    local nextAdd = "" --next info to add to status bar

    --line cursor is on
    if bStatus_lineNum then
        nextAdd = "Ln " .. yFile --cur line
        if bStatus_lineCount then --line count
            nextAdd = nextAdd .. "/" .. #tFile end

        charsLeft = addStatus(nextAdd, charsLeft)
    elseif bStatus_lineCount then
        nextAdd = #tFile .. " lines" --line count
        charsLeft = addStatus(nextAdd, charsLeft)
    end

    --INS for insert text, OVR for overwrite text
    if bStatus_insert then
        if bInsert then
            nextAdd = "INS"
        else
            nextAdd = "OVR" end
        charsLeft = addStatus(nextAdd, charsLeft)
    end

    sStatus = sStatus .. string.rep(" ", charsLeft) --filler
    sStatus = sStatus .. " >--" --paint me like one of your french girls

    --draw the bar
    term.setCursorPos(SCREEN_ORIGIN,SCREEN_HEIGHT)
    term.write(sStatus)
end

--push next status on to the status text
function addStatus(sText, nCharsLeft)
    if nCharsLeft >= #sText + 2 then --if status can fit wholly on line
        if #sStatus <= 4 then --if first status added
            sStatus = sStatus .. sText
            nCharsLeft = nCharsLeft - #sText --reduce remaining space for statuses
        else
            sStatus = sStatus .. "  " .. sText
            nCharsLeft = nCharsLeft - (#sText + 2) --reduce remaining space for statuses
        end
    end
    return nCharsLeft
end

--draw general message at the bottom of the screen for one loop
function drawMessage()
    if sMessage == "" then
        return end

    --truncates message
    sMessage = string.sub(sMessage, 1, SCREEN_WIDTH - 8)

    --add dashes on the side to draw attention
    local fillerDrawn = ((SCREEN_WIDTH - #sMessage)/2)-2 --num dashes on one side

    if fillerDrawn < 2 then
        fillerDrawn = 2 end

    local printedText = string.rep("-", fillerDrawn) .. "< " .. sMessage .. " >" .. string.rep("-", fillerDrawn + 1)

    --display message
    term.setCursorPos(SCREEN_ORIGIN,SCREEN_HEIGHT) --bottom left
    term.write(printedText)
end

--display debug info in bottom right
function drawDebug(sText)
    term.setCursorPos(SCREEN_WIDTH + 1 - #sText, SCREEN_HEIGHT) --set cursor at bottom rightmost while still showing all text
    term.write(sText)
end

--draw menu
function drawMenu(tMenu, nSel)
    --ALL HARD CODED POSITIONS ATM
    local xText,yText = SCREEN_ORIGIN+2, SCREEN_ORIGIN+2
    local xParam, yParam = xText + 40, SCREEN_ORIGIN+2

    for i,option in ipairs(tMenu) do
        --write text
        term.setCursorPos(xText, yText + (i-1))
        term.write(option.text)

        --write value
        if nSel == i then
            term.setCursorPos(xParam-2, yParam + (i-1))
            term.write("[ " .. tostring(option.value) .. " ]") --draw brackets to indicate selection
        else
            term.setCursorPos(xParam, yParam + (i-1))
            term.write(tostring(option.value))
        end
    end
end

--the background for the menu
function drawMenu_bg()
    local line = ""
    --draw top line
    local dashes = string.rep("-", (SCREEN_WIDTH-6)/2)
    line = "o"..dashes.." ed "..dashes
        if SCREEN_WIDTH-6 % 2 ~= 0 then --handling for odd screen widths
            line = line.."-o"
        else
            line = line.."o" end
    term.setCursorPos(SCREEN_ORIGIN, SCREEN_ORIGIN)
    term.write(line)

    --draw inbetween lines
    for i=SCREEN_ORIGIN+1,SCREEN_HEIGHT-1 do
        line = "|"..string.rep(" ", SCREEN_WIDTH-2).."|"
        term.setCursorPos(SCREEN_ORIGIN, i)
        term.write(line)
    end

    --draw bottom line
    line = "O"..string.rep("-", SCREEN_WIDTH-2).."O"
    term.setCursorPos(SCREEN_ORIGIN, SCREEN_HEIGHT)
    term.write(line)
end


------------------------
--      DEBUGGING     --
------------------------

--run the program being edited
function run(bArguments)
    local tArguments = {}

    --get arugments for program execution
    if bArguments then
        --draw seperator dashes below argument input
        term.setCursorPos(SCREEN_ORIGIN,SCREEN_ORIGIN+1)
        term.write(string.rep("-", SCREEN_WIDTH))

        --clear top line and get arguments
        term.setCursorPos(SCREEN_ORIGIN,SCREEN_ORIGIN)
        term.clearLine()
        term.write("Arguments: ")
        sArguments = read(nil, sArguments)

        --format arguments (stolen from shell)
        for match in string.gmatch(sArguments, "[^ \t]+") do --grabs each argument, space/tab delimitted
            table.insert(tArguments, match)
        end
    end

    --save() --save so its running the program in the editor
    term.clear()
    term.setCursorPos(SCREEN_ORIGIN,SCREEN_ORIGIN)
    --local progSuccess = shell.run(sFilepath, unpack(tArguments)) --OLD WAY (calling without debugging)
    sError = ""
    local progSuccess = runCatchErrors(table.concat(tFile, "\n"), unpack(tArguments))

    --formats error info
    if sError and sError ~= "" then
        local s1, s2 = string.find(sError, "%d+:") --the editor
        local errorStart, v = string.find(string.sub(sError, s2), "%d+:") --the executed code
        if errorStart ~= nil then
            sError = string.sub(string.sub(sError, s2), errorStart) --removed editor pre-error text
        else
            sError = string.sub(sError, s1) --removed executed pre-error text (name and colon)
        end
    end

    --display whether program succeeded or failed, then prompt to continue
    if progSuccess then
        sMessage = "SUCCESS - Press any key"
    else
        sMessage = "FAILED - Press any key" end
    drawMessage()

    while true do
        e, p1 = os.pullEvent()
        if e == "timer" and p1 == tTimer then
            tTimer = os.startTimer(TIMER_INTERVAL) --reset timer
        elseif e == "key" then
            break end
    end
    os.sleep(0) --if the key pressed produces a "char" event, this prevents it from going to the next input loop

    initializeSystem() --reset program systerm-oriented settings (in case they've been changed)

    if sError and sError ~= "" then --moves cursor to error line and display error message
        local v1, v2 = string.find(sError, "%d+") --get error line
        local errorLine = tonumber(string.sub(sError, v1, v2))
        xFile = 1
        yFile = errorLine
        sMessage = sError
    else --no error
        sMessage = "" end
end

--specialized function to run a file and catch the runtime errors
--Courtesy of faubiguy
function runCatchErrors( sProgram, ... ) --sProgram is a string containing the current text. Any other arguments are arguments to the program.
    local tArgs = { ... }
    local fnFile, err = loadstring( sProgram )
    if fnFile then
        local tEnv = {["shell"] = shell}
        setmetatable( tEnv, { __index = _G } )
        setfenv( fnFile, tEnv )
        local ok, err = pcall( function()
                fnFile( unpack( tArgs ) )
        end )
        if not ok then
                if err and err ~= "" then
                        print( err )
                        sError = err -- sError is the variable where you want the error
                end
                return false
        end
                sError = "" -- error value set to "" on successful execution
        return true
    end
    if err and err ~= "" then
                print( err )
                sError = err -- Again replace sError with the variable where you want the error
        end
    return false
end


------------------------
--       TYPING       --
------------------------

--inserts characters the user types in
function insertText(sText)
    local removeChar = 0
    if not bInsert then --overwrite the next char instead of inserting if settings say so
        removeChar = 1 end

    --insert/overwrite text
    tFile[yFile] = string.sub(tFile[yFile], 1, xFile-1) .. sText .. string.sub(tFile[yFile], xFile + removeChar)

    shiftCursor(#sText, 0)
    bUnsavedChanges = true
end

--key press: enter
function key_enter()
    if xFile <= #tFile[yFile] then --if cursor is between characters
        table.insert(tFile, yFile+1, string.sub(tFile[yFile], xFile)) --move remainder of characters to a new line
        tFile[yFile] = string.sub(tFile[yFile], 1, xFile-1) --and delete the moved characters from the previous line
    else --cursor at the end of the line
        table.insert(tFile, yFile+1, "")
    end

    --move cursor to begining of line and down
    shiftCursorHome()
    shiftCursor(0,1)

    --auto insert tabs equal to number on last line
    local v, numTabs = string.find(tFile[yFile-1], "[\t]+")
    if v ~= 1 or numTabs == nil then --tabs found, but not at the start of the line
        numTabs = 0 end
    insertText(string.rep("\t", numTabs))

    bUnsavedChanges = true
end

--key press: backspace
function key_backspace()
    if not (yFile == 1 and xFile == 1) then --if not at the first character in the file
        if xFile == 1 then --if at the start of a line, concatenate line above with this line
            shiftCursor(0,-1)
            shiftCursorEnd()

            tFile[yFile] = tFile[yFile] .. tFile[yFile+1] --concat lines
            table.remove(tFile, yFile+1) --remove second line
        else --otherwise just delete one character
            shiftCursor(-1,0)
            tFile[yFile] = string.sub(tFile[yFile], 1, xFile-1) .. string.sub(tFile[yFile], xFile+1)
        end
        bUnsavedChanges = true
    end
end

--key press: delete
function key_delete()
    if not (yFile == #tFile and xFile == #tFile[yFile] + 1) then --if not at the last character in the file
        if xFile > #tFile[yFile] then --if cursor is at the end of the line, concatenate with line below
            tFile[yFile] = tFile[yFile] .. tFile[yFile+1] --concat lines
            table.remove(tFile, yFile+1) --remove second line
        else --otherwise just delete one character
            tFile[yFile] = string.sub(tFile[yFile], 1, xFile-1) .. string.sub(tFile[yFile], xFile+1)
        end
        bUnsavedChanges = true
    end
end



------------------------
--        MENU        --
------------------------

function menuInit_settings()
    local opShowLineNum = { text = "Show line numbers",
                            type = "bool",
                            param = nil,
                            value = bShowLineNum }
    local opShowLineNumSep = {  text = "Show line number seperator",
                                type = "bool",
                                param = nil,
                                value = bShowLineNumSep }
    local opShowStatusBar = {   text = "Show status bar",
                                type = "bool",
                                param = nil,
                                value = bShowStatusBar }
        local opStatus_lineNum = {  text = "Show status - line number",
                                    type = "bool",
                                    param = nil,
                                    value = bStatus_lineNum }
        local opStatus_lineCount = {    text = "Show status - line count",
                                        type = "bool",
                                        param = nil,
                                        value = bStatus_lineCount }
        local opStatus_insert = {   text = "Show status - insert",
                                    type = "bool",
                                    param = nil,
                                    value = bStatus_insert }
    local opShowMessages = {    text = "Show messages",
                                type = "bool",
                                param = nil,
                                value = bShowMessages }
    local opMinLineDigitsVisible = {    text = "Min line num characters shown",
                                        type = "number",
                                        param = { 1, nil },
                                        value = nMinLineDigitsVisible }
    local opSpacesPerTab = {    text = "Spaces per tab",
                                type = "number",
                                param = { 1, nil },
                                value = nSpacesPerTab }

    local menu = {  opShowLineNum,
                    opShowLineNumSep,
                    opShowStatusBar,
                    opStatus_lineNum,
                    opStatus_lineCount,
                    opStatus_insert,
                    opShowMessages,
                    opMinLineDigitsVisible,
                    opSpacesPerTab }

    return menu
end

--top level menu accessed via F1
function menu()
    os.sleep(0) --prevents runover input from accessing the menu
    term.setCursorBlink(false) --HARDCODED
    local tMenu = menuInit_settings() --HARDCODED intializing values

    nSel = 1 --index of selected element
    opBack = {  text = "",
                type = "exit",
                param = nil,
                value = "BACK" }
    table.insert(tMenu, opBack)

    --draw
    drawMenu_bg()
    drawMenu(tMenu, nSel)

    local bRunning = true
    while bRunning do
        --input
        local e, p1 = os.pullEvent()
        if e == "timer" and p1 == tTimer then --main loop interval timer
            tick()
        else --user input (IMPORTANT distinction)
            if e == "key" then --key input
                if p1 == keys.up then --UP
                    if nSel > 1 then
                        nSel = nSel - 1 --move selection up
                    else
                        nSel = #tMenu end --move selection to bottom

                elseif p1 == keys.down then --DOWN
                    if nSel < #tMenu then
                        nSel = nSel + 1 --move selection down
                    else
                        nSel = 1 end --move selection to top

                elseif p1 == keys.left then --LEFT
                    if tMenu[nSel].type == "bool" then --if bool
                        tMenu[nSel].value = not tMenu[nSel].value --flip bool value
                    elseif tMenu[nSel].type == "number" then --if number
                        if tMenu[nSel].param[1] == nil then --if no min then decrease number
                            tMenu[nSel].value = tMenu[nSel].value - 1
                        elseif tMenu[nSel].value > tMenu[nSel].param[1] then --if num is above min then decrease number
                            tMenu[nSel].value = tMenu[nSel].value - 1 end
                    elseif tMenu[nSel].type == "table" then --if table

                    end
                elseif p1 == keys.right then --RIGHT
                    if tMenu[nSel].type == "bool" then --if bool
                        tMenu[nSel].value = not tMenu[nSel].value --flip bool value
                    elseif tMenu[nSel].type == "number" then --if number
                        if tMenu[nSel].param[2] == nil then --if no max then increase number
                            tMenu[nSel].value = tMenu[nSel].value + 1
                        elseif tMenu[nSel].value < tMenu[nSel].param[2] then --if num is below max then increase number
                            tMenu[nSel].value = tMenu[nSel].value + 1 end
                    elseif tMenu[nSel].type == "table" then --if table

                    end

                elseif p1 == keys.enter then --ENTER
                    if tMenu[nSel].type == "exit" then --exit menu
                        bRunning = false
                    elseif tMenu[nSel].type == "bool" then --flip bool value
                        tMenu[nSel].value = not tMenu[nSel].value
                    end

                elseif p1 == keys.space then --SPACE
                    if tMenu[nSel].type == "exit" then --exit menu
                        bRunning = false
                    elseif tMenu[nSel].type == "bool" then --flip bool value
                        tMenu[nSel].value = not tMenu[nSel].value
                    end

                elseif p1 == keys.f1 then --F1
                    bRunning = false

                elseif p1 == keys.f4 then --F4
                    bRunning = false
                end
            end
        end

        --draw
        drawMenu_bg()
        drawMenu(tMenu, nSel)
    end

    --hardcoded grabbing values
    bShowLineNum = tMenu[1].value
    bShowLineNumSep = tMenu[2].value
    bShowStatusBar = tMenu[3].value
    bStatus_lineNum = tMenu[4].value
    bStatus_lineCount = tMenu[5].value
    bStatus_insert = tMenu[6].value
    bShowMessages = tMenu[7].value
    nMinLineDigitsVisible = tMenu[8].value
    nSpacesPerTab = tMenu[9].value

    saveSettings()

    term.setCursorBlink(true) --HARDCODED (asumes top layer)
    applyBoundrySettings() --HARDCODED (asumes top layer)

    os.sleep(0) --prevent carryover input
end


------------------------
--        CORE        --
------------------------

--initializes system settings (this is called at startup and after program execution)
function initializeSystem()
    term.setCursorBlink(true)
    alignCursor()
end

--intialization
function intialize()
    load() --load file
    loadSettings() --loads user settings

    --setup screen
    applyBoundrySettings()
    draw()
    initializeSystem()
end

--handles user input
function input()
    --wait for key input
    local e, p1 = os.pullEvent()

    --timer input
    if e == "timer" and p1 == tTimer then --main loop interval timer
        tick()
    else --user input (IMPORTANT distinction)
        sMessage = "" --clear message

        --EXIT if confirmed, otherwise reset confirmation flag
        if bConfirmingExit == true and e == "key" and p1 == keys.f4 then
            exit()
        else
            bConfirmingExit = false end

        --character input
        if e == "char" then
            insertText(p1)

        --non-character, key input
        elseif e == "key" then
            --DONT USE F2, F10, F11, ALT, ESC

            --functions
            if p1 == keys.f1 then --menu
                menu()
            elseif p1 == keys.f3 then --save
                save()
            elseif p1 == keys.f4 then --exit
                exit()
            elseif p1 == keys.f5 then --run program in editor
                run(false)
            elseif p1 == keys.f6 then --run with arguments
                run(true)

            --movement
            elseif p1 == keys.up then --up
                shiftCursor(0, -1)
            elseif p1 == keys.down then --down
                shiftCursor(0, 1)
            elseif p1 == keys.left then --left
                shiftCursor(-1, 0)
            elseif p1 == keys.right then --right
                shiftCursor(1, 0)
            elseif p1 == keys.home then --home
                shiftCursorHome()
            elseif p1 == keys["end"] then --end
                shiftCursorEnd()
            elseif p1 == keys.pageUp then --pasge up
                shiftCursor(0, -(yMax-yMin))
            elseif p1 == keys.pageDown then --page down
                shiftCursor(0, yMax-yMin)

            --removing characters
            elseif p1 == keys.backspace then --backspace
                key_backspace()
            elseif p1 == keys.delete then --delete
                key_delete()

            --adding whitespace
            elseif p1 == keys.enter then --enter
                key_enter()
            elseif p1 == keys.tab then --tab
                insertText("\t")
                bUnsavedChanges = true

            --insert
            elseif p1 == keys.insert then
                bInsert = not bInsert

            end
        end
    end
end

--main timer interval actions
function tick()
    --do interval stuff
    --insertText("HI")
    --sMessage = "TIMER HIT!"

    tTimer = os.startTimer(TIMER_INTERVAL) --reset timer
end

--main loop
function mainLoop()
    tTimer = os.startTimer(TIMER_INTERVAL) --start interval timer

    while bRunning do
        if bClearDebug then
            sDebugText = "" end --clear debug info

        input() --get input and respond

        --debug info
        local x,y = term.getCursorPos()
        --sDebugText = sDebugText .. " Running:" ..tostring(bRunning)
        --sDebugText = sDebugText .. " File:"..xFile..","..yFile .." Scrn:"..x..","..y

        scroll() --shift screen to show cursor
        draw() --update screen
    end
end

--exit program
function exit()
    if bUnsavedChanges and not bConfirmingExit then --if there are unsaved changes, and this warning hasnt displayed yet
        sMessage = "UNSAVED CHANGES - Press F4 to exit"
        bConfirmingExit = true
    else
        bRunning = false end
end

--have the program exit cleanly and tidily
function exitCleanup()
    term.clear()
    term.setCursorPos(SCREEN_ORIGIN,SCREEN_ORIGIN)
end

intialize()
mainLoop()
exitCleanup()