Computercraft Roomba

local fuelSlot = 16

function checkResources()
    --Check fuel
    local selectedSlot = turtle.getSelectedSlot()
    local fuelThreshold = 2

    if(turtle.getFuelLevel() < fuelThreshold) then
        print("Turtle out of fuel!")
        if(turtle.getItemCount(fuelSlot)>0) then
            turtle.select(fuelSlot) --switch to fuel slot
            if(turtle.refuel(1))then --refuel one coal
                print("Turtle Refueled")
            end
            turtle.select(selectedSlot) --switch back to previous slot
        end
    end
end

function turnAround()
    turtle.turnRight()
    turtle.turnRight()
end

function checksurroundings()
    --Checking surroundings return values
    -- -1 - unreliable
    -- 0 - no surrounding blocks
    -- 1 - block only on left
    -- 2 - block only on right
    -- 4 - block only on front
    -- 3 - blocks on left, right
    -- 5 - blocks on front, left
    -- 6 - blocks on front, right
    -- 7 - blocks on front, left, and right

    local surroundings = 0

    if(turtle.turnLeft()) then--turn left to face left
        if(turtle.detect()) then --detect
            surroundings = surroundings + 1 -- 1 - block on left
        end
    else --unable to turn left
        print "Unreliable left detect"
        return -1
    end

    if(turtle.turnRight()) then --Turn right to face forward
        if(turtle.detect()) then
            surroundings = surroundings + 4 -- 2 - block on front
        end
    else --unable to turn right returns unreliable
        print "Unreliable front detect"
        return -1

    end

    if(turtle.turnRight()) then --Turn right to face right
        if(turtle.detect()) then
            surroundings = surroundings + 2 -- 4 - block on right
        end
        turtle.turnLeft() --return to face forwards
    else --unable to turn right returns unreliable
        print "Unreliable right detect"
        return -1
    end

    return surroundings
end

function rotateToPosition(position)
    local timeout = 4 --how many times to turn before returning failure
    local timer = 0 --incremental timer
    local success = false

    while(not success) do
        if(timer<timeout) then
            local surroundings = checksurroundings()
            if(surroundings == position)then
                success = true
            else
                turtle.turnRight()
            end
        end
        return false
    end

    return success
end

function getPerimeterPath()
    local perimeterPath = {}
    --Forward
    --Left turn
    --Right turn
    --turnaround

    local lastSurroundings = 0

    local ogX,ogY,ogZ = gps.locate()
    local retToStart = false
    local startSurroundings = checksurroundings()

    while(not retToStart) do
        checkResources()

        local surroundings = checksurroundings() --get current surroundings
        --print("new: " .. tostring(surroundings)) --for diagnostics
        --print("last: " .. tostring(lastSurroundings)) --for diagnostics


        if(surroundings == 0)then --Nothing around the turtle
            turtle.turnLeft()
            turtle.forward()
            table.insert(perimeterPath, "left")
            table.insert(perimeterPath, "forward")
            print("move: turn left and forward")

        elseif(surroundings == 1) then --Follow a left wall
            turtle.forward()
            table.insert(perimeterPath, "forward")
            print("move: forward")

        elseif(surroundings == 2) then --Only block on right (probably previously followed wall)
            turtle.turnLeft()
            turtle.forward()
            table.insert(perimeterPath, "left")
            table.insert(perimeterPath, "forward")
            print("move: turn left and forward")

        elseif(surroundings == 3)then --Follow a left wall
            turtle.forward()
            table.insert(perimeterPath, "forward")
            print("move: forwards")

        elseif(surroundings == 4) then --Only block in front
            turtle.turnLeft()
            turtle.forward()
            table.insert(perimeterPath, "left")
            table.insert(perimeterPath, "forward")
            print("move: turn left and forwards")


        elseif(surroundings == 5) then --Normal corner
            turtle.turnRight()
            turtle.forward()
            table.insert(perimeterPath, "right")
            table.insert(perimeterPath, "forward")
            print("move: turn right and forwards")

        elseif(surroundings == 6) then --Block ahead and to right, able to move left
            turtle.turnLeft()
            turtle.forward()
            table.insert(perimeterPath, "left")
            table.insert(perimeterPath, "forward")
            print("move: turn left and forwards")

        elseif(surroundings == 7) then --Cornered in, turn around!
            turnAround()
            turtle.forward()
            table.insert(perimeterPath, "uturn")
            table.insert(perimeterPath, "forward")
            print("move: turn around and forwards")
        end

        local newX,newY,newZ = gps.locate()
        --print("gps: " .. tostring(newX) .. "," .. tostring(newY) .. "," .. tostring(newZ))
        if(newX == ogX and newY == ogY and newZ == ogZ) then
            retToStart = true
        end

        --print("----------------------")

        lastSurroundings = surroundings
    end

    if(rotateToPosition(startSurroundings)) then
        print("Returned to base!")
    else
        print("unable to find starting base position")
    end
    return perimeterPath
end

function doAction(action)
    if(action == "forward") then
        print("move: forward")
        turtle.forward()
    elseif(action == "left") then
        print("move: turn left")
        turtle.turnLeft()
    elseif(action == "right")then
        print("move: turn right")
        turtle.turnRight()
    elseif(action =="uturn")then
        print("move: turn around")
        turnAround()
    else
        print("Action not recognised")
    end
end

local perimeterPath = getPerimeterPath()

for i, pathPiece in ipairs(perimeterPath) do
    doAction(pathPiece)
end