Auto Miner V2.0

-- West = Negative x
-- Top = Positive y
-- North = Negative z

local x,y,z = 0,0,0 --Relative to First position
local Orien = 0 --0:Forward; 1:Right; 2:Back; 3:Left
local Heading = {x=0,y=0,z=0}
local Query
local IsFull = false

function MoveUp(amount)
    if (amount==0) then return end
    if (amount<0) then amount=amount*-1 end

    for i=1,amount,1 do
        turtle.digUp()
        if (turtle.up()) then
            y=y+1
            term.setCursorPos(1,2)
            term.write("I am at: " .. x .. " " .. y .. " " .. z)
            term.setCursorPos(1,3)
            term.write("Fuel: " .. turtle.getFuelLevel())
        end
    end
end
function MoveDown(amount)
    if (amount==0) then return end
    if (amount<0) then amount=amount*-1 end

    for i=1,amount,1 do
        turtle.digDown()
        if (turtle.down()) then
            y=y-1
            term.setCursorPos(1,2)
            term.write("I am at: " .. x .. " " .. y .. " " .. z)
            term.setCursorPos(1,3)
            term.write("Fuel: " .. turtle.getFuelLevel())
        end
    end
end

function MoveForward(amount)
    if (amount==0) then return end
    if (amount<0) then amount=amount*-1 end

    for i=1,amount,1 do
        turtle.dig()
        turtle.digDown()
        if (turtle.forward()) then
            if (Orien==0)then
                z=z-1
            elseif (Orien==1)then
                x=x+1
            elseif (Orien==2)then
                z=z+1
            elseif (Orien==3)then
                x=x-1
            end
            term.setCursorPos(1,2)
            term.write("I am at: " .. x .. " " .. y .. " " .. z)
            term.setCursorPos(1,3)
            term.write("Fuel: " .. turtle.getFuelLevel())
        end
    end
end

function SetFacing(direction)
    if (direction==3 and Orien==0) then
        turtle.turnLeft()
        Orien=Orien-1
        return
    end

    while(true) do
        if (direction==Orien) then
            break
        end

        if (direction>Orien) then
            if (turtle.turnRight()) then
                Orien = Orien+1
                if (Orien>3) then Orien=0 end
            end
        elseif (direction<Orien) then
            if (turtle.turnLeft()) then
                Orien = Orien-1
                if (Orien<-1) then Orien=3 end
            end
        end
    end
end

function Movement()
    --X
    if (x>Heading.x) then
        SetFacing(3)
    elseif (x<Heading.x) then
        SetFacing(1)
    end
    MoveForward(Heading.x - x)

    --Y
    if (y>Heading.y) then
        MoveDown(Heading.y - y)
    elseif (y<Heading.y) then
        MoveUp(Heading.y - y)
    end

    --Z
    if (z>Heading.z) then
        SetFacing(0)
    elseif (z<Heading.z) then
        SetFacing(2)
    end
    MoveForward(Heading.z - z)
end

function Search()
    turtle.select(2)
    turtle.equipRight() --Equip scanner

    local Scanner = peripheral.wrap("right")
    local scan = Scanner.scan(5)
    if (scan ~= nil) then
        for i, data in ipairs(scan) do
            if (string.match(data.name, Query)) then
                Heading.x = data.x+x
                Heading.y = data.y+y
                Heading.z = data.z+z
                turtle.equipRight(2) --UnEquip scanner
                return
            end
        end
        --Wander North
        Heading.x = 0
        Heading.y = 0
        Heading.z = z-5
        turtle.equipRight(2) --UnEquip scanner
    else
        --Wander North
        Heading.x = 0
        Heading.y = 0
        Heading.z = z-5
        turtle.equipRight(2) --UnEquip scanner
    end
end

function Refuel()
    turtle.select(1) --Select bucket

    local success, data = turtle.inspect()
    if (success and data.name=="minecraft:lava") then
        turtle.place()
    end

    success, data = turtle.inspectUp()
    if (success and data.name=="minecraft:lava") then
        turtle.placeUp()
    end

    success, data = turtle.inspectDown()
    if (success and data.name=="minecraft:lava") then
        turtle.placeDown()
    end
end

function Inventory()
    --1 and 2 are the bucket and the scanner, so DON'T drop them
    IsFull = true
    for i=3,16,1 do
        local data = turtle.getItemDetail(i)
        if (data~=nil) then
            if (string.match(data.name, Query)==nil) then -- Missing to count if items are full stacks
                turtle.select(i)
                turtle.drop()
                IsFull = false
            elseif (data.count<64) then --Will not work if stack is 16
                IsFull = false
            end
        end
    end
end

function GoHome()
    local FuelNeeded = ((x+y+z)*2)+100 -- Imagine is a straight line and then think it has to dig all the way
                                       -- (+100 just in case there is gravel)

    if (turtle.getFuelLevel()<=FuelNeeded or IsFull==true) then
        term.clear()
        term.setCursorPos(1,1)
        term.write("Heading home.")

        Heading.x=0
        Heading.y=0
        Heading.z=0
        Movement()
        return true
    end

    return false
end

-- Main --
term.clear()
term.setCursorPos(1,1)
term.setTextColor(colors.orange)
term.write("Place turtle facing North.")
term.setCursorPos(1,2)
term.setTextColor(colors.white)
term.write("Place a bucket in the first slot,")
term.setCursorPos(1,3)
term.write("then a geo scanner in the second,")
term.setCursorPos(1,4)
term.write("then equip a pickaxe on the right side")
term.setCursorPos(1,5)
term.write("and a chunk loader on the left.")

term.setTextColor(colors.green)
term.setCursorPos(1,7)
term.write("Search for: ")
Query = read()
while(true) do
    term.clear()
    term.setCursorPos(1,1)
    term.write(Query .. " at: " .. Heading.x .. " " .. Heading.y .. " " .. Heading.z)
    term.setCursorPos(1,2)
    term.write("I am at: " .. x .. " " .. y .. " " .. z)
    term.setCursorPos(1,3)
    term.write("Fuel: " .. turtle.getFuelLevel())

    if (GoHome()==false) then
        Search()
        Movement()
        Refuel()
        Inventory()
    else
        break
    end
end