-- Credit/Sources/Inspiration
-- https://tweaked.cc/
-- https://www.reddit.com/r/ComputerCraft/comments/v7vdur/im_confused_with_vectors/

-- Variable declarations for movement.
local currentPosition = vector.new(0, 0, 0)
local chestPosition = vector.new(0, 0, 0)
-- Direction turtle is facing on placement is considered facing direction 0.
local facing = 0
local facingDirections = {
    [0] =  "forwards", -- Right
    [1] = "right", -- Left
    [2] = "backwards", -- Forwards
    [3] = "left" -- Backwards
}
local checkpointPosition = vector.new(0, 0, 0)
local movementDirections = {
    ["right"] =  vector.new(1, 0, 0), -- Right
    ["left"] = vector.new(-1, 0, 0), -- Left
    ["up"] = vector.new(0, 1, 0), -- Up
    ["down"] = vector.new(0, -1, 0), -- Down
    ["forwards"] = vector.new(0, 0, 1), -- Forwards
    ["backwards"] = vector.new(0, 0, -1) -- Backwards
}
local isGoingHome = false
-- Variable declaration for tunnel dimensions.
local tunnelHeight = 0
local tunnelWidth = 0
local tunnelDepth = 0
local realTunnelHeight = 0 -- Because we are starting at 0 which is technically height "1" we have to subtract 1 from the height.
local realTunnelWidth = 0 -- Because we are starting at 0 which is technically width "0" we have to subtract 1 from the width.

-- Function declarations.

-- Prints out the current position/vector.
local function getCurrentPosition()
    write("Current position: " .. tostring(currentPosition) .. "\n")
end

-- Moves forward once.
local function forward()
    write("Moving forward...\n")
    if(turtle.detect()) then
        write("Block in front of me. Digging...\n")
        turtle.dig()
    end
    turtle.forward()
    local direction = facingDirections[facing]
    currentPosition = currentPosition + movementDirections[direction]
    getCurrentPosition()
end

-- Turns right once.
local function turnRight()
    write("Turning right...\n")
    turtle.turnRight()
    facing = (facing + 1) % 4
    write("I am facing "..facingDirections[facing]..".\n")
end

-- Turns left once.
local function turnLeft()
    write("Turning left...\n")
    turtle.turnLeft()
    facing = (facing - 1) % 4
    write("I am facing "..facingDirections[facing]..".\n")
end

-- Moves up once.
local function up()
    write("Moving up...\n")
    if(turtle.detectUp()) then
        write("Block above me. Digging...\n")
        turtle.digUp()
    end
    turtle.up()
    currentPosition = currentPosition + movementDirections["up"]
    getCurrentPosition()
end

-- Moves down once.
local function down()
    write("Moving down...\n")
    if(turtle.detectDown()) then
        write("Block below me. Digging...\n")
        turtle.digDown()
    end
    turtle.down()
    currentPosition = currentPosition + movementDirections["down"]
    getCurrentPosition()
end

-- Turns left or right until facing the correct direction.
local function face(direction)
    if facingDirections[facing] == direction then return end
    local turn
    if facingDirections[(facing + 1) % 4] == direction then
      turn = turnRight
    else
      turn = turnLeft
    end
    repeat
      turn()
    until facingDirections[facing] == direction
end

local function buildFloor()
    -- If we are not on the floor or we are going home, we don't need to do anything.
    if((currentPosition.y ~= 0) or isGoingHome) then
        return
    end
    if not turtle.detectDown() then
        turtle.select(1)
        turtle.placeDown()
    elseif(currentPosition.z ~= 0) then
        -- Only start floor pattern after we moved forward.
        if((currentPosition.z % 2 > 0 and currentPosition.x % 2 > 0) or (currentPosition.z % 2 == 0 and currentPosition.x % 2 == 0)) then
            -- Chess Pattern for floor.
            turtle.digDown()
            turtle.select(1)
            turtle.placeDown()
        end
    end
end

local function buildCeiling()
    if(currentPosition.y == realTunnelHeight) then
        if not turtle.detectUp() then
            turtle.select(1)
            turtle.placeUp()
        end
    end
end

-- Uses some functions above combined to move to a specified point relative to the turtles position.
local function goTo(newPosition)
    -- Align on the X axis
    if currentPosition.x > newPosition.x then
        face("left")
    elseif currentPosition.x < newPosition.x then 
        face("right")
    end
    while currentPosition.x ~= newPosition.x do
        buildCeiling()
        buildFloor()
        forward()
    end
  
    -- Align on the Y axis
    while currentPosition.y > newPosition.y do -- we're above where we want to go
        buildCeiling()
        buildFloor()
        down()
    end
    while currentPosition.y < newPosition.y do -- we're below where we want to go
        buildCeiling()
        buildFloor()
        up()
    end
  
    -- Align on the Z axis
    if currentPosition.z > newPosition.z then
        face("backwards")
    elseif currentPosition.z < newPosition.z then 
        face("forwards")
    end
    while currentPosition.z ~= newPosition.z do
        buildCeiling()
        buildFloor()
        forward()
    end
end

local function digColumn()
    -- If we on the bottom row, dig up to specified height. Otherwise dig down to Y = 0 (in Vector not Minecraft).
    if(currentPosition.y < realTunnelHeight) then
        repeat 
            goTo(currentPosition + movementDirections["up"])
        until currentPosition.y == realTunnelHeight
    else
        repeat 
            goTo(currentPosition + movementDirections["down"])
        until currentPosition.y == 0
    end
end

local function digTunnel()
    -- Starting position is always bottom left.
    -- Reapeat as long was we have not reached the specified depth.
    while currentPosition.z < tunnelDepth do
        -- Always move forward for the next tunnel layer.
        goTo(currentPosition + movementDirections["forwards"])
        digColumn()
        -- If we are on the left, dig to the right and vice versa.
        if(currentPosition.x < realTunnelWidth) then
            repeat
                goTo(currentPosition + movementDirections["right"])
                digColumn()
            until currentPosition.x == realTunnelWidth
        else
            repeat
                goTo(currentPosition + movementDirections["left"])
                digColumn()
            until currentPosition.x == 0
        end
    end
end

-- "Main"
print("How high do you want the tunnel to be?")
write("Height: ")
tunnelHeight = tonumber(io.read())
realTunnelHeight = tunnelHeight-1
print("How wide do you want the tunnel to be?")
write("Width: ")
tunnelWidth = tonumber(io.read())
realTunnelWidth = tunnelWidth-1
print("How deep do you want the tunnel to be?")
write("Depth: ")
tunnelDepth = tonumber(io.read())
digTunnel()
--- Go back "home"/to starting position.
isGoingHome = true
goTo(vector.new(0, 0, 0))
face("forwards")