autoTunnel

local h -- Holds file to be manipulated
local input
local success, data -- Turtle inspect values
local stuck = false

local running = true
local timeout = 2

local constantIdentifiers
= {"Origin X", "Origin Y", "Origin Z", "Origin Side (0 to 3)", "Origin Next to Entrance (0 or 1)", "Signal Block (mod:blockname)"}

local originX
local originY
local originZ
local originSide
local originNextToEntrance
local signalBlock

local checkpointX
local checkpointY
local checkpointZ
local checkpointFacing

local x, y, z
local facing -- 0 to 3 (north to west)
local blocksTravelled -- From origin
local allInventorySlotsUsed

local function setConstants()
    h = fs.open("constants", "w")
    print("Enter constants:")
    for i = 1, #constantIdentifiers do
        write("    ")
        write(constantIdentifiers[i])
        write(" = ")
        input = read()
        h.writeLine(input)
    end
    h.close()
end

local function setState(values)
    h = fs.open("state", "w")
    for i = 1, 4 do
        h.writeLine(values[i])
    end
    h.close()
end

local function readConstants()
    h = fs.open("constants", "r")
    originX = tonumber(h.readLine())
    originY = tonumber(h.readLine())
    originZ = tonumber(h.readLine())
    originSide = tonumber(h.readLine())
    originNextToEntrance = tonumber(h.readLine())
    signalBlock = h.readLine()
    h.close()
end

local function readState()
    h = fs.open("state", "r")
    checkpointX = tonumber(h.readLine())
    checkpointY = tonumber(h.readLine())
    checkpointZ = tonumber(h.readLine())
    checkpointFacing = tonumber(h.readLine())
    h.close()
end

local function refuel()
    for i = 1, 16 do
        turtle.select(i)
        turtle.refuel()
    end
end

local function getFacing()
    local xOld, yOld, zOld
    repeat
        xOld, yOld, zOld = gps.locate(timeout)
    until xOld and yOld and zOld
    repeat
        turtle.dig()
        stuck = not turtle.forward()
    until not stuck
    repeat
        x, y, z = gps.locate(timeout)
    until x and y and z
    turtle.back()
    if z < zOld then
        return 0
    elseif z > zOld then
        return 2
    elseif x < xOld then
        return 3
    elseif x > xOld then
        return 1
    end
end

local function trackTurnLeft()
    turtle.turnLeft()
    facing = (facing - 1) % 4
end
local function trackTurnRight()
    turtle.turnRight()
    facing = (facing + 1) % 4
end

local function faceDirection(target)
    if facing == (target + 1) % 4 then
        trackTurnLeft()
    else
        while facing ~= target do
            trackTurnRight()
        end
    end
end

local function goTo(targetX, targetY, targetZ, targetDirection)
    repeat
        x, y, z = gps.locate(timeout)
    until x and y and z

    if z > targetZ then
        faceDirection(0)
        repeat
            turtle.dig()
            turtle.forward()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until z == targetZ
    elseif z < targetZ then
        faceDirection(2)
        repeat
            turtle.dig()
            turtle.forward()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until z == targetZ
    end

    if x > targetX then
        faceDirection(3)
        repeat
            turtle.dig()
            turtle.forward()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until x == targetX
    elseif x < targetX then
        faceDirection(1)
        repeat
            turtle.dig()
            turtle.forward()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until x == targetX
    end

    if y > targetY then
        repeat
            turtle.digDown()
            turtle.down()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until y == targetY
    elseif y < targetY then
        repeat
            turtle.digUp()
            turtle.up()
            repeat
                x, y, z = gps.locate(timeout)
            until x and y and z
        until y == targetY
    end

    faceDirection(targetDirection)
end

local function mineOres()
    for i = 1, 3 do
        success, data = turtle.inspect()
        if success then
            if string.find(string.lower(data.name), "ore") then
                turtle.dig()
                turtle.forward()
                mineOres()
                turtle.back()
            end
        end

        if i == 2 then
            trackTurnRight()
        end
        trackTurnRight()
    end

    success, data = turtle.inspectUp()
    if success then
        if string.find(string.lower(data.name), "ore") then
            turtle.digUp()
            turtle.up()
            mineOres()
            turtle.down()
        end
    end

    success, data = turtle.inspectDown()
    if success then
        if string.find(string.lower(data.name), "ore") then
            turtle.digDown()
            turtle.down()
            mineOres()
            turtle.up()
        end
    end
end

if not fs.exists("constants") then
    setConstants()
end
if not fs.exists("state") then
    setState({"nil", "nil", "nil", "nil"})
end
readConstants()
readState()

refuel()

facing = getFacing()
if checkpointX ~= nil and checkpointY ~= nil and checkpointZ ~= nil and checkpointFacing ~= nil then
    goTo(checkpointX, checkpointY, checkpointZ, checkpointFacing)
end

while running do
    repeat
        x, y, z = gps.locate(timeout)
    until x and y and z
    setState({tostring(x), tostring(y), tostring(z), tostring(facing)})

    blocksTravelled = math.abs(x - originX) + math.abs(y - originY) + math.abs(z - originX)
    allInventorySlotsUsed = true
    for i = 1, 16 do
        turtle.select(i)
        if turtle.getItemCount() == 0 then
            allInventorySlotsUsed = false
        end
    end

    if blocksTravelled >= turtle.getFuelLevel() + 10 or allInventorySlotsUsed then
        if originNextToEntrance == 0 then
            if facing == (originSide + 1) % 4 then
                trackTurnRight()
                trackTurnRight()
            end
        elseif originNextToEntrance == 1 then
            if facing == (originSide - 1) % 4 then
                trackTurnRight()
                trackTurnRight()
            end
        end
    end

    success, data = turtle.inspectDown()
    if data.name == signalBlock then
        if facing == originSide then
            if originNextToEntrance == 0 then
                trackTurnRight()
            elseif originNextToEntrance == 1 then
                trackTurnLeft()
            end
        elseif facing == (originSide + 2) % 4 then
            if originNextToEntrance == 0 then
                trackTurnLeft()
            elseif originNextToEntrance == 1 then
                trackTurnRight()
            end
        end
        turtle.select(1)
        turtle.digDown()
    else
        x, y, z = gps.locate(timeout)
        success, data = turtle.inspectUp()
        if originSide == 0 then
            if data.name == signalBlock then
                if z > originZ then
                    if originNextToEntrance == 0 then
                        trackTurnRight()
                    elseif originNextToEntrance == 1 then
                        trackTurnLeft()
                    end
                elseif z < originZ then
                    if originNextToEntrance == 0 then
                        trackTurnLeft()
                    elseif originNextToEntrance == 1 then
                        trackTurnRight()
                    end
                end
                turtle.select(1)
                turtle.placeDown()
            end
        elseif originSide == 2 then
            if data.name == signalBlock then
                if z > originZ then
                    if originNextToEntrance == 0 then
                        trackTurnLeft()
                    elseif originNextToEntrance == 1 then
                        trackTurnRight()
                    end
                elseif z < originZ then
                    if originNextToEntrance == 0 then
                        trackTurnRight()
                    elseif originNextToEntrance == 1 then
                        trackTurnLeft()
                    end
                end
                turtle.select(1)
                turtle.placeDown()
            end
        elseif originSide == 1 then
            if data.name == signalBlock then
                if x > originX then
                    if originNextToEntrance == 0 then
                        trackTurnLeft()
                    elseif originNextToEntrance == 1 then
                        trackTurnRight()
                    end
                elseif x < originX then
                    if originNextToEntrance == 0 then
                        trackTurnRight()
                    elseif originNextToEntrance == 1 then
                        trackTurnLeft()
                    end
                end
                turtle.select(1)
                turtle.placeDown()
            end
        elseif originSide == 3 then
            if data.name == signalBlock then
                if x > originX then
                    if originNextToEntrance == 0 then
                        trackTurnRight()
                    elseif originNextToEntrance == 1 then
                        trackTurnLeft()
                    end
                elseif x < originX then
                    if originNextToEntrance == 0 then
                        trackTurnLeft()
                    elseif originNextToEntrance == 1 then
                        trackTurnRight()
                    end
                end
                turtle.select(1)
                turtle.placeDown()
            end
        end
    end

    success, data = turtle.inspect()
    if data.name == signalBlock then
        trackTurnRight()
        trackTurnRight()
    end

    repeat
        x, y, z = gps.locate(timeout)
    until x and y and z

    setState({tostring(x), tostring(y), tostring(z), tostring(facing)})
    mineOres()

    success, data = turtle.inspectDown()
    if data.name == "minecraft:chest" then
        for i = 1, 16 do
            turtle.select(i)
            turtle.dropDown()
        end
    end

    turtle.dig()
    turtle.forward()
end