rom/programs/edit

local tArgs = { ... }
if #tArgs == 0 then
    print( "Usage: edit <path>" )
    return
end

local sPath = shell.resolve( tArgs[1] )
local bReadOnly = fs.isReadOnly( sPath )
if fs.exists( sPath ) and fs.isDir( sPath ) then
    print( "Cannot edit a directory" )
    return
end

local w,h = term.getSize()
local x,y = 1,1
local scrollX, scrollY = 0,0

local bMenu = false
local nMenuItem = 1

local sStatus = ""
local tLines = {}

local function load()
    tLines = {}
    if fs.exists( sPath ) then
        local file = io.open( sPath, "r" )
        local sLine = file:read()
        while sLine do
            table.insert( tLines, sLine )
            sLine = file:read()
        end
        file:close()
    else
        table.insert( tLines, "" )
    end
end

local function save()
    local file = io.open( sPath, "w" )
    if file then
        for n, sLine in ipairs( tLines ) do
            file:write( sLine .. "\n" )
        end
        file:close()
        return true
    end
    return false
end

local function redrawText()
    for y=1,h-1 do
        term.setCursorPos( 1 - scrollX, y )
        term.clearLine()

        local sLine = tLines[ y + scrollY ]
        if sLine ~= nil then
            term.write( sLine )
        end
    end
    term.setCursorPos( x - scrollX, y - scrollY )
end

local function redrawLine()
    local sLine = tLines[y]
    term.setCursorPos( 1 - scrollX, y - scrollY )
    term.clearLine()
    term.write( sLine )
    term.setCursorPos( x - scrollX, y - scrollY )
end

local tMenuItems = { "Save", "Exit" }

local function redrawMenu()
    term.setCursorPos( 1, h )
    term.clearLine()

    if not bMenu then
        term.write( sStatus )
    else
        for n,sItem in ipairs( tMenuItems ) do
            if n == nMenuItem then
                term.write( "["..sItem.."]" )
            else
                term.write( " "..sItem.." " )
            end
        end
    end

    term.setCursorPos( x - scrollX, y - scrollY )
end

local function setStatus( _sText )
    sStatus = _sText
    redrawMenu()
end

local function setCursor( x, y )
    local screenX = x - scrollX
    local screenY = y - scrollY

    local bRedraw = false
    if screenX < 1 then
        scrollX = x - 1
        screenX = 1
        bRedraw = true
    elseif screenX > w then
        scrollX = x - w
        screenX = w
        bRedraw = true
    end

    if screenY < 1 then
        scrollY = y - 1
        screenY = 1
        bRedraw = true
    elseif screenY > h-1 then
        scrollY = y - (h-1)
        screenY = h-1
        bRedraw = true
    end

    if bRedraw then
        redrawText()
    end
    term.setCursorPos( screenX, screenY )
end

load()

term.clear()
term.setCursorPos(x,y)
term.setCursorBlink( true )

redrawText()
setStatus( "Press Ctrl to access menu" )

local bRunning = true
local tMenuFunctions = {
    ["Exit"] = function()
        bRunning = false
    end,
    ["Save"] = function()
        if save() then
            setStatus( "Saved to "..sPath )
        else
            setStatus( "Access denied" )
        end
    end,
}

local function doMenuItem( _n )
    local fnMenu = tMenuFunctions[ tMenuItems[_n] ]
    if fnMenu then
        fnMenu()
    end

    bMenu = false
    term.setCursorBlink( true )
    redrawMenu()
end

while bRunning do
  local sEvent, param = os.pullEvent()
  if sEvent == "key" then
    if param == 200 then
        -- Up
        if not bMenu then
            -- Move cursor up
            if y > 1 then
                y = y - 1
                x = math.min( x, string.len( tLines[y] ) + 1 )
                setCursor( x, y )
            end
        end
    elseif param == 208 then
        -- Down
        if not bMenu then
            -- Move cursor down
            if y < #tLines then
                y = y + 1
                x = math.min( x, string.len( tLines[y] ) + 1 )
                setCursor( x, y )
            end
        end
    elseif param == 201 then
        -- Page Up
        if not bMenu then
            -- Move up a page
            local sx,sy=term.getSize()
            if y>sy-1 then
                y = y-sy-1
            else
                y = 1
            end
            x = math.min( x, string.len( tLines[y] ) + 1 )
            setCursor( x, y )
        end
    elseif param == 209 then
        -- Page Down
        if not bMenu then
            -- Move down a page
            local sx,sy=term.getSize()
            if y<#tLines-sy-1 then
                y = y+sy-1
            else
                y = #tLines
            end
            x = math.min( x, string.len( tLines[y] ) + 1 )
            setCursor( x, y )
        end
    elseif param == 199 then
        -- Home
        if not bMenu then
            -- Move cursor to the beginning
            x=1
            setCursor(x,y)
        end
    elseif param == 207 then
        -- End
        if not bMenu then
            -- Move cursor to the end
            x = string.len( tLines[y] ) + 1
            setCursor(x,y)
        end
    elseif param == 203 then
        -- Left
        if not bMenu then
            -- Move cursor left
            if x > 1 then
                x = x - 1
            elseif x==1 and y>1 then
                x = string.len( tLines[y-1] ) + 1
                y = y - 1
            end
            setCursor( x, y )
        else
            -- Move menu left
            nMenuItem = nMenuItem - 1
            if nMenuItem < 1 then
                nMenuItem = #tMenuItems
            end
            redrawMenu()
        end
    elseif param == 205 then
        -- Right
        if not bMenu then
            -- Move cursor right
            if x < string.len( tLines[y] ) + 1 then
                x = x + 1
            elseif x==string.len( tLines[y] ) + 1 and y<#tLines then
                x = 1
                y = y + 1
            end
            setCursor( x, y )
        else
            -- Move menu right
            nMenuItem = nMenuItem + 1
            if nMenuItem > #tMenuItems then
                nMenuItem = 1
            end
            redrawMenu()
        end
    elseif param == 211 then
        -- Delete
        if not bMenu then
            if  x < string.len( tLines[y] ) + 1 then
                local sLine = tLines[y]
                tLines[y] = string.sub(sLine,1,x-1) .. string.sub(sLine,x+1)
                redrawLine()
            elseif y<#tLines then
                tLines[y] = tLines[y] .. tLines[y+1]
                table.remove( tLines, y+1 )
                redrawText()
                -- don't touch that cursor
            end
        end
    elseif param == 14 then
        -- Backspace
        if not bMenu then
            if x > 1 then
                -- Remove character
                local sLine = tLines[y]
                tLines[y] = string.sub(sLine,1,x-2) .. string.sub(sLine,x)
                redrawLine()

                x = x - 1
                setCursor( x, y )

            elseif y > 1 then
                -- Remove newline
                local sPrevLen = string.len( tLines[y-1] )
                tLines[y-1] = tLines[y-1] .. tLines[y]
                table.remove( tLines, y )
                redrawText()

                x = sPrevLen + 1
                y = y - 1
                setCursor( x, y )
            end
        end

    elseif param == 28 then
        -- Enter
        if not bMenu then
            -- Newline
            local sLine = tLines[y]
            tLines[y] = string.sub(sLine,1,x-1)
            table.insert( tLines, y+1, string.sub(sLine,x) )
            redrawText()

            x = 1
            y = y + 1
            setCursor( x, y )

        else
            -- Menu selection
            doMenuItem( nMenuItem )
        end

    elseif param == 29 then
        -- Menu toggle
        bMenu = not bMenu
        if bMenu then
            term.setCursorBlink( false )
            nMenuItem = 1
        else
            term.setCursorBlink( true )
        end
        redrawMenu()

    end

  elseif sEvent == "char" then
    if not bMenu then
        -- Input text
        local sLine = tLines[y]
        tLines[y] = string.sub(sLine,1,x-1) .. param .. string.sub(sLine,x)
        redrawLine()

        x = x + string.len( param )
        setCursor( x, y )

    else
        -- Select menu items
        for n,sMenuItem in ipairs( tMenuItems ) do
            if string.lower(string.sub(sMenuItem,1,1)) == string.lower(param) then
                doMenuItem( n )
                break
            end
        end
    end
  end
end

term.clear()
term.setCursorBlink( false )
term.setCursorPos( 1, 1 )