-- Mine a hole of depth by width by heigth, starting from 0, 0, -1 relative to
-- current position and facing

-- +x = right of start, +y = up of start, +z = forward of start
local FUEL_RESERVE = 800
local FUEL_REFUEL_UNIT = 8 -- how many items to refuel with at a time
local FULL_CHECK_SLOT = 14 -- slot to check for "fullness"

-- what size of a dimension is considered big enough to split into medium-size
-- pieces
local BIG_DIM = 7

local V_ZERO = vector.new(0, 0, 0)
local UNIT_X = vector.new(1, 0, 0)
local UNIT_Y = vector.new(0, 1, 0)
local UNIT_Z = vector.new(0, 0, 1)

local FORWARD, RIGHT, BACK, LEFT = 0, 1, 2, 3
local mode = { v = vector.new(0, 0, 0), facing = FORWARD }
mode.mine = { forward = true }

---------------------- BLOCK MATH ------------------------

function copy_v(v)
    return vector.new(
        v.x,
        v.y,
        v.z
    )
end

local bmetatable, new_block
-- what is this? a type that holds a starting position and a dimention as
-- two vectors
-- TODO learn about metatables
local Block = {
    -- orient our corner and offset to a vector
    orient = function (self, pos)
        self.v1 = self.v1 - pos
        local dims = {
            x = { self.v1.x, self.v1.x + self.v2.x },
            y = { self.v1.y, self.v1.y + self.v2.y },
            z = { self.v1.z, self.v1.z + self.v2.z }
        }
        for dim, points in pairs(dims) do
            -- pick the closer point
            -- return to point-offset format
            local point, offset
            if math.abs(points[1]) <= math.abs(points[2]) then
                point = points[1]
                offset = points[2] - points[1]
            else
                point = points[2]
                offset = points[1] - points[2]
            end
            self.v1[dim] = point
            self.v2[dim] = offset
        end
        self.v1 = self.v1 + pos
        return self
    end,
    take = function (self, amt, dir)
        -- TODO
        if dir ~= "x" and dir ~= "y" and dir ~= "z" then return nil end

        local block_offset = -1
        if self.v2[dir] < 0 then
            amt = amt * -1
            block_offset = 1
        end

        local new, remainder = self:copy(), self
        new.v2[dir] = amt + block_offset
        remainder.v1[dir] = remainder.v1[dir] + amt
        remainder.v2[dir] = remainder.v2[dir] - amt

        return new, remainder
    end,
    copy = function (self)
        return new_block(
            vector.new(self.v1.x, self.v1.y, self.v1.z),
            vector.new(self.v2.x, self.v2.y, self.v2.z)
        )
    end,
    tostring = function (self)
        -- TODO revisit?
        return string.format('%s %s', self.v1:tostring(), self.v2:tostring())
    end
}

bmetatable = {
    __name = "Block",
    __index = Block,
}

new_block = function (v1, v2)
    return setmetatable(
        { v1 = v1, v2 = v2 },
        bmetatable
    )
end

---------------------- BASIC MOVEMENT ---------------------

function mineSides ()
    if mode.mine.up then
        turtle.digUp()
    end
    if mode.mine.down then
        turtle.digDown()
    end
end

function moveInLine (delta)
    mineSides()
    while delta > 0 do
        if mode.mine.forward then
            turtle.dig()
        end
        local success = turtle.forward()
        if success then
            mineSides()
            delta = delta - 1
        end
    end
end

function moveUpDown (delta)
    while delta > 0 do
        if mode.mine.forward then
            turtle.digUp()
        end
        local success = turtle.up()
        if success then
            delta = delta - 1
        end
    end
    while delta < 0 do
        if mode.mine.forward then
            turtle.digDown()
        end
        local success = turtle.down()
        if success then
            delta = delta + 1
        end
    end
end

function turnToFace (new_direction)
    local delta = new_direction - mode.facing
    if delta > 2 then
        delta = delta - 4
    elseif delta < -2 then
        delta = delta + 4
    end
    while delta > 0 do
        turtle.turnRight()
        delta = delta - 1
    end
    while delta < 0 do
        turtle.turnLeft()
        delta = delta + 1
    end
    mode.facing = new_direction
end

function getCurrentPos()
    return mode.v
end

-- move to a specific point
function moveAbs (v)
    -- print(string.format("Moving to (%s)", v:tostring()))
    move(v - getCurrentPos())
end

-- move relative to the turtle's current location
function move (v)
    -- x
    if v.x > 0 then
        turnToFace(RIGHT)
        moveInLine(v.x)
    elseif v.x < 0 then
        turnToFace(LEFT)
        moveInLine(-v.x)
    end
    mode.v.x = mode.v.x + v.x
    -- z
    if v.z > 0 then
        turnToFace(FORWARD)
        moveInLine(v.z)
    end
    if v.z < 0 then
        turnToFace(BACK)
        moveInLine(-v.z)
    end
    mode.v.z = mode.v.z + v.z
    -- y
    moveUpDown(v.y)
    mode.v.y = mode.v.y + v.y
end

-------------- DROPPING OFF AND REFUELING -------------------

function refuelUntil (amt)
    while turtle.getFuelLevel() < amt do
        if not turtle.refuel(FUEL_REFUEL_UNIT) then break end
    end
end

function dropOffItems (starting_point, go_back)
    print("Time to drop off what I got")
    -- Turn off mining
    mode.mine = { forward = true }
    -- Note current position (assuming facing FORWARD)
    local pos_state = getCurrentPos()
    -- Return to origin, facing BACK
    moveAbs(starting_point)
    moveAbs(V_ZERO)
    turnToFace(BACK)
    -- deposit items
    for slot = 2, 16 do
        turtle.select(slot)
        turtle.drop()
    end
    turtle.select(1)
    -- Return to current position, facing forward
    if go_back then
        moveAbs(starting_point)
        moveAbs(pos_state)
    end
end

function inventoryFull ()
    -- leave a little extra space just in case
    return turtle.getItemCount(FULL_CHECK_SLOT) > 0
end

function checkAndDropOff(starting_point)
    if inventoryFull() then dropOffItems(starting_point, true) end
    refuelUntil(FUEL_RESERVE)
end

function mine (block)
    -- assumptions: block is mineable in a single pass and oriented to the
    -- currentPos
    -- rough algo draft:
    -- 1. go to "starting point" at one end of block
    --    a. don't move vertically if you don't have to
    --    b. set mining mode beforehand
    -- 2. move to the ending point
    local offset = 1
    if block.v2.y < 0 then offset = -1 end
    local height = block.v2.y + offset
    local start_v = copy_v(block.v1)
    local end_v = block.v1 + block.v2
    if height > 2 then
        start_v = start_v + UNIT_Y
        end_v = end_v - UNIT_Y
    elseif height < -2 then
        start_v = start_v - UNIT_Y
        end_v = end_v + UNIT_Y
    end
    moveAbs(start_v)
    if height % 3 == 0 then
        mode.mine = { up = true, forward = true, down = true }
    elseif height == 2 then
        mode.mine = { forward = true, up = true }
        end_v = end_v - UNIT_Y
    elseif height == -2 then
        mode.mine = { forward = true, down = true }
        end_v = end_v + UNIT_Y
    end
    moveAbs(end_v)
end

function canMine (block)
    local tooHigh = math.abs(block.v2.y) > 2
    -- we can only mine in a 1-wide strip at a time
    local tooWide = (math.abs(block.v2.x) > 0) and (math.abs(block.v2.z) > 0)
    return not (tooHigh or tooWide)
end

function splitHorizontal (block)
    -- TODO make this less naive?
    -- Future work: potentially split a large block into smaller blocks
    -- based on currentPos (think splitting down the middle instead of
    -- splitting off of one end)
    local bigBlock = function (block)
        return (block.v2.x >= BIG_DIM) and (block.v2.z >= BIG_DIM)
    end
    local inMiddleOfBlock = function (block)
        local middle_of_x = differentSigns(block.v1.x, block.v2.x)
        local middle_of_z = differentSigns(block.v1.z, block.v2.z)
        return middle_of_x or middle_of_z
    end
    local inMiddleOfBigBlock = function (block)
        return bigBlock(block) and inMiddleOfBlock(block)
    end
    if inMiddleOfBigBlock(block) then
        -- TODO split the big block at where the turtle is near
    end
    -- decide whether to take a slice off of the x or z direction
    -- (criteria: take the dimension that is not too big)
    if math.abs(block.v2.z) < BIG_DIM then
        return block:take(1, "z")
    else
        return block:take(1, "x")
    end
end

function split (block)
    local tooHigh = function (block)
        return math.abs(block.v2.y) > 2
    end
    if tooHigh(block) then
        return block:take(3, "y")
    else
        return splitHorizontal(block)
    end
end

function process (stack, starting_point)
    -- fuel and go to starting point
    refuelUntil(FUEL_RESERVE)
    mode.mine = { forward = true }
    if #stack == 0 then return nil end
    local working = table.remove(stack):orient(getCurrentPos())
    print("Working:", working:tostring())
    if canMine(working) then
        checkAndDropOff(starting_point)
        mine(working)
    else
        local new, remainder = split(working, mode.v)
        table.insert(stack, remainder)
        table.insert(stack, new)
    end
    return process (stack, starting_point)
end

function run (v1, v2)
    -- TODO calculate starting_point, the place turtle will move to before
    -- moving to the first corner of block
    local block = new_block(v1, v2 - v1)
    local starting_point = V_ZERO

    process({ block }, starting_point)
    -- return to base
    dropOffItems(starting_point)
    turnToFace(FORWARD)
end

function usage ()
    print("Usage: mine x1 y1 z1 x2 y2 z2 OR mine x1 y1 z1 OR mine x1 y1 z1 \
        x2 y2 z2 x_turtle y_turtle z_turtle.")
    print("Mine from the first set of coordinates to the second in a \
        rectangular prism.")
    print("The coordinates are relative to the facing of the turtle at the \
        start of the program.")
    print("If invoked with only three arguments, act as if they are the last \
        three arguments and substitute 0 0 0 for the first three.")
    print("If invoked with nine arguments, interpret the first two sets as \
        world coordinates of the rectangular prism and the third set as \
        the coordinates of the turtle's starting position, \
        ASSUMING FACING NORTH.")
    print("Fuel goes in the top-left slot of the turtle's inventory.")
end

function argsToNumbers ()
    local num_args = {}
    for i, v in ipairs(arg) do
        num_args[i] = tonumber(v)
    end
    return num_args
end

local arg = argsToNumbers()
if #arg == 3 then
    run(V_ZERO, vector.new(arg[1], arg[2], arg[3]))
elseif #arg == 6 then
    run(vector.new(arg[1], arg[2], arg[3]), vector.new(arg[4], arg[5], arg[6]))
elseif #arg == 9 then
    local turtle_pos = vector.new(arg[7], arg[8], arg[9])
    local v1, v2 = vector.new(arg[1], arg[2], arg[3])
                 , vector.new(arg[4], arg[5], arg[6])
    run(v1 - turtle_pos, v2 - turtle_pos)
else
    usage()
end