Turtle API

local old_fd = old_fd or turtle.forward
local old_bk = old_bk or turtle.back
local old_lt = old_lt or turtle.turnLeft
local old_rt = old_rt or turtle.turnRight
local old_up = old_up or turtle.up
local old_dn = old_dn or turtle.down
saveOnMove = false
saveOnTurn = true
local x,y,z,fx,fz
local filePos = {}
if fs.exists("turtle position") then
    local f = fs.open("turtle position","r")
    filePos = textutils.unserialize(f.readAll() or "")
    f.close()
end
local gpsPos = {gps.locate(0)}
if filePos.x and gpsPos[1] then
    x,y,z,fx,fz = gpsPos[1],gpsPos[2],gpsPos[3],filePos.fx,filePos.fz
elseif gpsPos[1] then
    if not turtle.forward() then
        print("Need to move forward to get Facing")
        while not turtle.forward() do
            turtle.refuel(1)
            sleep(1)
        end
    end
    local gpsPos2 = {gps.locate(0)}
    repeat until turtle.back()
    x,y,z,fx,fz = gpsPos[1],gpsPos[2],gpsPos[3],gpsPos2[1]-gpsPos[1],gpsPos2[3]-gpsPos[3]
elseif filePos.x then
    x,y,z,fx,fz = filePos.x,filePos.y,filePos.z,filePos.fx,filePos.fz
else
    local display = {"X","Y","Z","FX","FZ"}
    local result = {}
    local input
    for i=1,5 do
        repeat
            write(display[i]..": ")
            input = tonumber(read())
        until input
        table.insert(result,input)
    end
    x,y,z,fx,fz = unpack(result)
end
local function save()
    local f = fs.open("turtle position","w")
    f.write(textutils.serialize(getPos()))
    f.close()
end
function turtle.forward()
    if turtle.detect() then return false,"Movement obstructed" end
    x = x + fx
    z = z + fz
    if saveOnMove then save() end
    local r,m = old_fd()
    if not r then
        x = x - fx
        z = z - fz
        if saveOnMove then save() end
    end
    return r,m
end
function turtle.back()
    x = x - fx
    z = z - fz
    if saveOnMove then save() end
    local r,m = old_bk()
    if not r then
        x = x + fx
        z = z + fz
        if saveOnMove then save() end
        sleep(1)
    end
    return r,m
end
function turtle.up()
    if turtle.detectUp() then return false,"Movement obstructed" end
    y = y + 1
    if saveOnMove then save() end
    local r,m = old_up()
    if not r then
        y = y - 1
        if saveOnMove then save() end
    end
    return r,m
end
function turtle.down()
    if turtle.detectDown() then return false,"Movement obstructed" end
    y = y - 1
    if saveOnMove then save() end
    local r,m = old_dn()
    if not r then
        y = y + 1
        if saveOnMove then save() end
    end
    return r,m
end
function turtle.turnLeft()
    fx,fz = fz,-fx
    if saveOnTurn then save() end
    return old_lt()
end
function turtle.turnRight()
    fx,fz = -fz,fx
    if saveOnTurn then save() end
    return old_rt()
end
function face(tfx,tfz)
    if tfx==-fz and tfz==fx then
        turtle.turnRight()
    end
    while tfx~=fx or tfz~=fz do
        turtle.turnLeft()
    end
    return true
end
function goto(tx,ty,tz,tfx,tfz,startWithDir)
    if type(tx)=="table" then
        if tx.x then
            startWithDir=ty
            tx,ty,tz,tfx,tfz = tx.x,tx.y,tx.z,tx.fx,tx.fz
        end
        if #tx>=3 then
            startWithDir=ty
            tx,ty,tz,tfx,tfz = unpack(tx)
        end
    end
    tx,ty,tz,tfx,tfz=tonumber(tx),tonumber(ty),tonumber(tz),tonumber(tfx),tonumber(tfz)
    if not (tx and ty and tz) then
        return false,"Invalid coordinates"
    end
    local dirs = {
        function()
            if x<tx then
                face(1,0)
                while x<tx and turtle.forward() do end
            end
            if x>tx then
                face(-1,0)
                while x>tx and turtle.forward() do end
            end
            return x==tx
        end,
        function()
            while y<ty and turtle.up() do end
            while y>ty and turtle.down() do end
            return y==ty
        end,
        function()
            if z<tz then
                face(0,1)
                while z<tz and turtle.forward() do end
            end
            if z>tz then
                face(0,-1)
                while z>tz and turtle.forward() do end
            end
            return z==tz
        end
    }
    local tryDir = startWithDir or 1
    local successCount=0
    repeat
        if dirs[(tryDir%3)+1]() then
            successCount = successCount + 1
        else
            successCount = 0
        end
        tryDir = tryDir + 1
    until successCount>=3 or tryDir>=30
    if successCount>=3 and tfx and tfz then
        face(tfx,tfz)
    end
    return successCount>=3
end
local Position = {__tostring=function() return "X:"..tostring(x).." Y:"..tostring(y).." Z:"..tostring(z).." Facing:"..getFacingName() end}
Position.__index = Position
function Position:goto()
    return goto(self.x,self.y,self.z,self.fx,self.fz)
end
Position.__call = Position.goto
function Position:moveBy()
    return goto(x+self.x,y+self.y,z+self.z,fx,fz)
end
function Position:gotoPoint()
    return goto(self.x,self.y,self.z)
end
function Position:face()
    return face(self.fx,self.fz)
end
function Position:toVector()
    return vector.new(self.x,self.y,self.z)
end
function newPos(ax,ay,az,afx,afz)
    if type(ax)=="table" then
        if ax.x then
            ax,ay,az,afx,afz = ax.x,ax.y,ax.z,ax.fx,ax.fz
        end
        if #x>=3 then
            ax,ay,az,afx,afz = unpack(ax)
        end
    end
    local result = {x=ax,y=ay,z=az,fx=afx,fz=afz}
    setmetatable(result,Position)
    return result
end
function getPos()
    return newPos(x,y,z,fx,fz)
end
function getFacing(afx,afz)
    return (afx or fx)==0 and 1-(afz or fz) or 2+(afx or fx)
end
function getFacingName(afx,afz)
    local names={"South","West","North","East"}
    return names[getFacing(afx,afz)+1]
end