-- 'Hole' program, version 2

-- Stores dimensions for the hole
local size, depth = 0,0

-- Stores current turtle position, relative to start point
local xPos, yPos, zPos = 0,0,0
local xDirSav, zDirSav = 0,0

-- Stores current direction, positive x is directly forwards from start point
-- positive z is directly right
local xDir, zDir = 1,0

-- Stores last saved position
local xSay, ySav, zSav = 0,0,0

-- **************************************************
-- Movement / Turning functions

local function moveForward()
    -- Account for falling blocks, such as sand and gravel
    while turtle.detect() do
        turtle.dig()
        sleep(0.8)
    end
    -- If there is any mob infront of the turtle, or we are out of fuel
    -- DEV NOTE: Will be modified later to refuel, or message over rednet wifi
    while not turtle.forward() do
        sleep(1)
    end

    -- Update position
    xPos = xPos + xDir
    zPos = zPos + zDir
end

local function moveUp()
    -- Account for falling blocks
    while turtle.detectUp() do
        turtle.digUp()
        sleep(0.8)
    end
    --Update position
    yPos = yPos + 1

    turtle.up()
end

local function moveDown()
    -- No need to account for falling blocks
    turtle.digDown()

    -- Update position
    yPos = yPos - 1

    turtle.down()
end

local function turnLeft()
    -- Update direction vector
    zDir, xDir = -xDir, zDir

    turtle.turnLeft()
end

local function turnRight()
    -- Update direction vector
    zDir, xDir = xDir, -zDir

    turtle.turnRight()
end

local function turnAround()
    -- Update direction
    zDir, xDir = -zDir, -xDir

    turtle.turnLeft()
    turtle.turnLeft()
end

-- Turns the turtle to the prompted direction
local function turnToDir(x, z)
    if x == 1 and xDir == 0 then
        if zDir == 1 then
            turnLeft()
        else
            turnRight()
        end
    elseif x == 1 and xDir == -1 then
        turnAround()
    elseif x == -1 and xDir == 0 then
        if zDir == 1 then
            turnRight()
        else
            turnLeft()
        end
    elseif x == -1 and xDir == 1 then
        turnAround()
    elseif z == 1 and zDir == 0 then
        if xDir == 1 then
            turnRight()
        else
            turnLeft()
        end
    elseif z == 1 and zDir == -1 then
        turnAround()
    elseif z == -1 and zDir == 0 then
        if xDir == 1 then
            turnLeft()
        else
            turnRight()
        end
    elseif z == -1 and zDir == 1 then
        turnAround()
    else
        return false
    end
    return true
end

-- Takes in a coordinate and moves the turtle there
-- USE NOTE: Turtle will be facing in negative x direction upon completion.
-- This is to do with returning home, so it's facing the chest
local function moveToPos(x, y, z)

    -- Move the turtle to the required X value
        if x > xPos then
            turnToDir(1, 0)
            while x > xPos do
                moveForward()
            end
        elseif x < xPos then
            turnToDir(-1, 0)
            while x < xPos do
                moveForward()
            end
        end

    -- Move the turtle to the required Z value
        if z > zPos then
            turnToDir(0, 1)
            while z > zPos do
                moveForward()
            end
        elseif z < zPos then
            turnToDir(0, -1)
            while z < zPos do
                moveForward()
            end
        end

    -- Move the turtle to the required Y value
        if y > yPos then
            while y > yPos do
                moveUp()
            end
        else
            while y < yPos do
                moveDown()
            end
        end

    turnToDir(-1, 0)
end

-- End of movement functions
-- **************************************************

-- ++++++++++++++++++++++++++++++++++++++++++++++++++
-- Logic functions

-- Saves the current dig position and direction
local function saveDig()
    xSav = xPos
    ySav = yPos
    zSav = zPos
    xDirSav = xDir
    zDirSav = zDir
end

-- Moves the turlte back to the last saved position and direction
local function resumeDig()
    moveToPos(xSav, ySav, zSav)
    turnToDir(xDirSav, zDirSav)
end

-- Dumps the load into a chest or thin air
local function dumpLoad()
    for n = 1, 9 do
        turtle.select(n)
        turtle.drop()
    end
end

-- Simply checks if the turtle is full
-- DEV NOTE: this is kind of brute-forcish, I wonder if there's a better way?
local function isFull()
    local retVal = true
    for n = 1, 9 do
        if turtle.getItemCount(n) == 0 then
            retVal = false
        end
    end
    return retVal
end

-- This function controls the digging of the hole
local function digOut()
-- This for loop controls how many layers we are going to dig
    for n = 1, depth do
    -- Similarly, this one control how many 'strips' we are going to mine on this level
        for nn = 1, size do
        -- And this one controls how long each of those 'strips' is, and also if the
        -- turtle is full, it controls dumping the contents in the home chest
            for nnn = 2, size  do
                moveForward()
                if isFull() then
                    saveDig()
                    moveToPos(0, 0, 0)
                    dumpLoad()
                    resumeDig()
                end
            end
            -- This determines the direction the turtle will turn at the end of the
            -- strip, since it alternates every other strip
            if nn ~= size then
                if nn % 2 == 0 then
                    turnLeft()
                    moveForward()
                    turnLeft()
                else
                    turnRight()
                    moveForward()
                    turnRight()
                end
            end
        end
        -- Move to the home corner when the current layer is finished
        moveToPos(0, yPos, 0)
        -- If this was no the last layer, then start digging the next one, otherwise,
        -- head home and empty contents into the chest
        if m ~= depth then
            turnAround()
            moveDown()
        elseif m == depth then
            moveToPos(0, 0, 0)
            dumpLoad()
        end
    end
end

-- End of logic functions
-- ++++++++++++++++++++++++++++++++++++++++++++++++++

-- Main function controls flow of program
local function main(argc, argv)
    if argc ~= 2 then
        print("Usage: hole <diameter> <depth>")
        return false
    end

    size = argv[1]
    depth = argv[2]

    print("Beginning dig...")
    digOut()
    print("Finishing dig...")

end

main(#{...}, {...})