goto

args = {...}
rednet.open("right")
-- Make sure turtle is positioned correctly
term.clear()
term.setCursorPos(1,1)
doAutorestart = fs.exists("GPSExcavateCurrentpos") and #args == 0

if doAutorestart then
    print("Auto restarting... because no arguments have been deliverd and GPSExcavateCurrentpos does exist.")
else
    print("I am set up to dig a rectangle downward in a forward-left direction. There should be a refuel chest to my right and a dropoff chest behind me. Is this how I am set up?")
    print("\(y/n\)")
    while true do
        local event, character = os.pullEvent()
        if event == "char" and character == "y" then
            print("Initializing...")
            sleep(1)
            break
        elseif event == "char" and character == "n" then
            print("Please set up correctly.")
            error()
        end
    end
end

local function forward() --Forward movement
    --Move forward
    local i = 0 --Iterator for bedrock/strong player detection
    while not turtle.forward() do
        if not turtle.dig() then --Detect blocks
            i = i + 1
            turtle.attack() --Detect entities
            if i == 30 then
                return false --If movement fails
            end
        end
    end
    --Clear above and below
    if turtle.detectUp() then
        turtle.digUp()
    end
    if turtle.detectDown() then
        turtle.digDown()
    end
    --Position tracking
    if currentpos.f == 0 then
        currentpos.z = currentpos.z + 1
    elseif currentpos.f == 1 then
        currentpos.x = currentpos.x - 1
    elseif currentpos.f == 2 then
        currentpos.z = currentpos.z - 1
    elseif currentpos.f == 3 then
        currentpos.x = currentpos.x + 1
    else
        running = false
        error("Something went wrong with the direction :P")
    end
    return true
end
local function turnRight() --Right turn with position tracking
    turtle.turnRight()
    if currentpos.f < 3 then
        currentpos.f = currentpos.f + 1
    else
        currentpos.f = 0
    end
end
local function turnLeft() --Left turn with position tracking
    turtle.turnLeft()
    if currentpos.f > 0 then
        currentpos.f = currentpos.f - 1
    else
        currentpos.f = 3
    end
end
local function down() --Downward movement
    --Move down
    local i = 0 --Iterator for bedrock detection
    while not turtle.down() do
        if not turtle.digDown() then --Detect blocks
            i = i + 1
            turtle.attackDown() --Detect entities
            if i == 25 then
                return false --If movement fails
            end
        end
    end
    --Position tracking
    currentpos.y = currentpos.y - 1
    return true
end
local function mineDown() --Moves one layer downward
    if currentpos.y == edge.y + 2 then --If close to bottom (2 blocks away)
        if not down() then --If downward movement fails
            shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
            running = false
            error("I think I tried to dig bedrock.")
        end
    elseif currentpos.y == edge.y + 3 then --If close to bottom (3 blocks away)
        for i=1,2 do
            if not down() then --If downward movement fails
                shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
                running = false
                error("I think I tried to dig bedrock.")
            end
        end
    else --If far enough from bottom
        for i=1,3 do
            if not down() then --If downward movement fails
                shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
                running = false
                error("I think I tried to dig bedrock.")
            end
        end
    end
end
local function getFuelLevel() --Check if fuel level is unlimited
    local fuelLevel = turtle.getFuelLevel()
    if type(fuelLevel) == "string" then
        fuelLevel = 9001e9001
    end
    return fuelLevel
end
local function findDistance(x,y,z,newx,newy,newz) --Find how many blocks to travel to get somewhere (non-diagonally)
    local distance = 0
    local xDist = 0
    local yDist = 0
    local zDist = 0
    if x > newx then
        xDist = x - newx
    elseif x < newx then
        xDist = newx - x
    end
    if y > newy then
        yDist = y - newy
    elseif y < newy then
        yDist = newy - y
    end
    if z > newz then
        zDist = z - newz
    elseif z < newz then
        zDist = newz - z
    end
    distance = xDist + yDist + zDist
    return distance
end
local function saveLoc()
    --Write variables to savefile
    local fPos = fs.open("GPSExcavateCurrentpos","w")
    fPos.writeLine(currentpos.x)
    fPos.writeLine(currentpos.y)
    fPos.writeLine(currentpos.z)
    fPos.writeLine(currentpos.f)
    fPos.writeLine(storagepos.x)
    fPos.writeLine(storagepos.y)
    fPos.writeLine(storagepos.z)
    fPos.writeLine(edge.x)
    fPos.writeLine(edge.y)
    fPos.writeLine(edge.z)
    fPos.writeLine(backwards)
    fPos.writeLine(totalMined)
    fPos.writeLine(lastSlot)
    fPos.close()
end
local function detectUnwanted()
    local unwantedSlots = 0
    for i=1, lastSlot do
        turtle.select(i)
        if turtle.compareTo(13) or turtle.compareTo(14) or turtle.compareTo(15) or turtle.compareTo(16) then
            unwantedSlots = unwantedSlots + 1
        end
    end
    turtle.select(1)
    return unwantedSlots
end
local function dropUnwanted()
    local freeSlots = 0
    turtle.turnLeft()
    turtle.turnLeft()
    for i=1, lastSlot do
        turtle.select(i)
        if turtle.compareTo(13) or turtle.compareTo(14) or turtle.compareTo(15) or turtle.compareTo(16) then
            turtle.drop()
        end
    end
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.select(1)
end
local function dropAll() --Drop mined resources, display amounts
    local mined = 0
    turtle.turnRight()
    turtle.turnRight()
    for i=1,lastSlot do
        turtle.select(i)
        mined = mined + turtle.getItemCount(i)
        turtle.drop()
    end
    --This will send to rednet soon
    totalMined = totalMined + mined
    print("Minerals mined this run: "..mined)
    print("Total mined: "..totalMined)
    turtle.select(1)
    turtle.turnRight()
    turtle.turnRight()
end
local function refuel() --Refuel if needed
    turtle.turnRight()
    turtle.select(1)
    while getFuelLevel() < findDistance(currentpos.x,currentpos.y,currentpos.z,0,0,0) + 400 do --Enough to make it back to where he was digging and dig a bit
        turtle.suck()
        if turtle.getItemCount(1) == 0 then --If no fuel is in the box
            print("Please put fuel in my top-left slot, then press space.")
            while true do
                local event, character = os.pullEvent()
                if event == "key" and character == 57 then
                    print("Refueling...")
                    sleep(1)
                    break
                end
            end
        end
        if not turtle.refuel() then --If item isn't fuel
            print("This is not fuel! Please remove it, then press space.")
            while true do
                local event, character = os.pullEvent()
                if event == "key" and character == 57 then
                    print("Refueling...")
                    sleep(1)
                    break
                end
            end
        end
    end
    turtle.turnLeft()
end
local function dropRefuel()
    print("Dropping & refueling")
    shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
    dropAll()
    refuel()
    shell.run("goto","special",currentpos.x,currentpos.y,currentpos.z,currentpos.f,0,0,0,0) --Return to where he left off
end
local function excavate() --The actual excavation process
    while running do --Make sure stop signal hasn't been sent
        turtle.select(1)
        if currentpos.x == 0 and currentpos.y == 0 and currentpos.z == 0 then --To start off a layer down
            down()
            turtle.digDown()
        end
        if ( currentpos.x == edge.x and currentpos.y == edge.y + 1 and currentpos.z == edge.z or currentpos.x == edge.x and currentpos.y == edge.y + 1 and currentpos.z == 0 ) and not backwards or ( currentpos.x == 0 and currentpos.y == edge.y + 1 and currentpos.z == 0 or currentpos.x == 0 and currentpos.y == edge.y + 1 and currentpos.z == edge.z ) and backwards then --Very long check to see if at the end of process
            if lastSlot ~= 16 and detectUnwanted()  then
                dropUnwanted()
            end
            shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
            dropAll()
            print("Done digging a hole! Whew, that was hard work.")
            done = true --Record that turtle is finished digging
            running = false --Stop other "stopping" loop
            break
        end
        if turtle.getItemCount(lastSlot) > 0 then --Check if inventory is full or fuel is low
            if lastSlot ~= 16 then
                if detectUnwanted() < 3 then
                    dropUnwanted()
                    dropRefuel()
                else
                    dropUnwanted()
                end
                if turtle.getItemCount(lastSlot) > 0 then
                    turtle.select(lastSlot)
                    while turtle.getItemCount(lastSlot) > 0 do
                        for i=1, lastSlot do
                            turtle.transferTo(i)
                        end
                    end
                    turtle.select(1)
                end
            else
                dropRefuel()
            end
        end
        if getFuelLevel() < (findDistance(currentpos.x,currentpos.y,currentpos.z,0,0,0) + 16) then
            if lastSlot ~= 16 then
                dropUnwanted()
            end
            dropRefuel()
        end
        if ( currentpos.x == edge.x and currentpos.z == edge.z or currentpos.x == edge.x and currentpos.z == 0 ) and not backwards then --If at the end of a layer
            mineDown()
            turnRight()
            turnRight()
            backwards = true --Switching directions
            turtle.digDown()
        elseif ( currentpos.x == 0 and currentpos.z == 0 or currentpos.x == 0 and currentpos.z == edge.z ) and backwards then --If at the end of a layer
            mineDown()
            turnLeft()
            turnLeft()
            backwards = false --Switching directions
            turtle.digDown()
        elseif currentpos.z == edge.z then --If at edge, turn around and do next line
            if backwards then
                turnRight()
                forward()
                turnRight()
            else
                turnLeft()
                forward()
                turnLeft()
            end
        elseif currentpos.z == 0 and currentpos.x ~= 0 then --If at edge, turn around and do next line
            if backwards then
                turnLeft()
                forward()
                turnLeft()
            else
                turnRight()
                forward()
                turnRight()
            end
        end
        if not forward() then --If movement fails
            shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
            running = false
            error("I think I tried to dig bedrock.")
        end
        saveLoc()
    end
end
local function stop() --Ability to stop turtle mid-excavation. This will wait until current action is done, then exit the excavate function
    while running do
        local event, data, message = os.pullEvent()
        if event == "char" and data == "p" then --If direct keypress
            print("Stopping...")
            running = false
            break
        elseif event == "rednet_message" and message == "stop" then --If rednet stop signal
            print("Stopping...")
            running = false
            id = tonumber(data)
            break
        end
    end
end
local function restart() --To restart from previous digging
    print("Restarting from saved position...")
    if not fs.exists("GPSExcavateCurrentpos") then -- Check for save file
        error("Could not find saved position!")
    end
    --Read save file, change variables
    local fPos = fs.open("GPSExcavateCurrentpos","r")
    currentpos.x = tonumber(fPos.readLine())
    currentpos.y = tonumber(fPos.readLine())
    currentpos.z = tonumber(fPos.readLine())
    currentpos.f = tonumber(fPos.readLine())
    storagepos.x = tonumber(fPos.readLine())
    storagepos.y = tonumber(fPos.readLine())
    storagepos.z = tonumber(fPos.readLine())
    edge.x = tonumber(fPos.readLine())
    edge.y = tonumber(fPos.readLine())
    edge.z = tonumber(fPos.readLine())
    local backwardsString = fPos.readLine()
    if backwardsString == "true" then
        backwards = true
    else
        backwards = false
    end
    totalMined = tonumber(fPos.readLine())
    lastSlot = tonumber(fPos.readLine())
    fPos.close()
    shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
    shell.run("goto","special",currentpos.x,currentpos.y,currentpos.z,currentpos.f,0,0,0,0) --Go to position where turtle left off
    restarting = true
    print("Let the diggy-hole recommence!")
end

totalMined = 0 --Total mined out blocks over course of excavation
restarting = false --Whether turtle is restarting from save
done = false --Whether turtle has completed excavation
running = true --Whether turtle is currently digging
backwards = false --Which direction turtle is digging the layers currently
currentpos = {} --Current position. It's a table just because it is easier, no real need for it
storagepos = {} --Storage position. It's a table just because it is easier, no real need for it
edge = {} --Boundaries of hole. Same deal as currentpos, no real reason to have it as a table
id = -1 --Id of computer that sent the rednet message. This is so that it can reply when it has stopped
w, l, d = 0, 0, 0 --Width, length, depth of hole. This is just for input of numbers
currentpos.x, currentpos.y, currentpos.z, currentpos.f = 0, 0, 0, 0 --Initialise pieces of currentpos
lastSlot = 16 --Slot in which to make sure there are no blocks: this is to keep any comparing slots free

if doAutorestart or #args == 1 and args[1] == "restart" then --If restarting from save
    restart()
elseif #args == 2 and tonumber(args[1]) > 1 and tonumber(args[2]) > 2 then --If a square hole is wanted
    w = tonumber(args[1])
    l = w
    d = tonumber(args[2])
elseif #args == 3 and tonumber(args[1]) > 1 and tonumber(args[2]) > 1 and tonumber(args[3]) > 2 then --If a non-square hole is wanted
    w = tonumber(args[1])
    l = tonumber(args[2])
    d = tonumber(args[3])
else --If arguments improperly input, print usage
    print("Usage: \"GPSExcavate <side> <depth>\" or \"GPSExcavate <width> <length> <depth>\"")
    print("Note: depth must be at least 3.")
    print("To restart digging, use: \"GPSExcavate restart\"")
    error()
end
if not restarting then
    -- get storage position
    local x, y, z = gps.locate(5)
    if not x then --If gps.locate didn't work, it won't return anything. So check to see if it did.
        error("Failed to get my location!")
    else
        storagepos.x = x
        storagepos.y = y
        storagepos.z = z
        print("storagepos is (" .. storagepos.x .. ", " .. storagepos.y .. ", " .. storagepos.z .. ")")
    end

    --Input edge locations
    edge.x = w - 1
    edge.y = -(d - 1)
    edge.z = l - 1

    saveLoc()
    print("Let the diggy-hole commence! Digging a hole "..w.." by "..l.." by "..d.." meters.")
end
print("Press \"p\" to save and stop at any time.")
parallel.waitForAll(excavate,stop) --Actual running of program. This is to enable stopping mid-digging
if not done then --If turtle was stopped before the end
    print("Saving position and dimensions...")
    sleep(1)
    saveLoc()
    print("Position and dimensions saved. Returning to base...")
    shell.run("goto", storagepos.x,storagepos.y,storagepos.z) --Return to storage
    dropAll()
    print("Excavation stopped.")
    if id ~= -1 then --If stop signal was sent by rednet, reply when done returning
        rednet.send(id,"stopped")
    end
else --Get rid of save file if turtle is done excavating. I will find a way to have rednet in here too
    fs.delete("GPSExcavateCurrentpos")
end
print("Next hole please? :D")
 --Delete variables so they don't persist
args, currentpos, edge, id, done, restarting, running, w, l, d, backwards, lastSlot = nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil
rednet.close("right")