-- 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"

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
-- 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)
        -- TODO similar to "normalize"
        error("not yet implemented")
        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
        end
    end,
    take = function (self, amt, dir)
        -- TODO
        if dir ~= "x" and dir ~= "y" and dir ~= "z" then return nil end

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

        return new, remainder
    end,
    copy = function (self)
        return Block.new(
            vector.new(self.v1.x, self.v1.y, self.v1.z),
            vector.new(self.v2.x, self.v2.y, self.v2.z),
        )
    end
}

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

local 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 (%d, %d, %d)", v.x, v.y, v.z))
    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 = mode.v + UNIT_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 = mode.v + UNIT_Z
    -- y
    moveUpDown(v.y)
    mode.v = mode.v + UNIT_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)
    -- Turn off mining
    local mine_state = mode.mine
    mode.mine = { forward = true }
    -- Note current position (assuming facing FORWARD)
    local pos_state = vector.new(mode.v.x, mode.v.y, mode.v.z)
    -- 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
    -- Turn mining back on, if it was on
    mode.mine = mine_state
end

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

function moveAndCheck (v, starting_point)
    move(v)
    if inventoryFull() then dropOffItems(starting_point, true) end
    refuelUntil(FUEL_RESERVE)
end

function mine (block)
    -- TODO adjust for new paradigm
    -- assumptions: block is mineable in a single pass
    -- 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. refuel beforehand
    -- 2. move to the ending point
    -- 3. drop off items if necessary
    move(start_v)
    move(end_v)
end

function canMine (block)
    local notTooHigh = block.v2.y > 3
    -- we can only mine in a 1-wide strip at a time
    local notTooWide = block.v2.x > 1 and block.v2.z > 1
    return not (tooHigh or tooWide)
end

function splitHorizontal (block)
    -- TODO make this less naive?
    return block:take(1, "x")
end

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

function process (stack, starting_point)
    -- START code taken from `mine`
    -- fuel and go to starting point
    refuelUntil(FUEL_RESERVE)
    mode.mine = { forward = true }
    moveAbs(starting_point)
    -- END
    -- TODO
    if #stack == 0 then return nil end
    local working = table.remove(stack)
    if canMine(working) then
        mine(working)
    else
        local new, remainder = split(working, mode.v)
        table.insert(stack, remainder)
        table.insert(stack, new)
    end
    return process (stack)
end

function calculateBlock (v1, v2)
    -- Using the coordinates, construct a block of certain dimensions, a
    -- certain distance away.
    local block = {}
    local normalize = function (dim, c1, c2)
        -- pick the closest point
        -- offset goes to the other point
        local corner, offset
        if math.abs(c1) <= math.abs(c2) then
            corner, offset = c1, c2 - c1
        else
            corner, offset = c2, c1 - c2
        end
        block[dim] = corner
        block[dim .. "off"] = offset
    end
    normalize("x", v1.x, v2.x)
    normalize("y", v1.y, v2.y)
    normalize("z", v1.z, v2.z)
    return new_block(
        vector.new(block.x, block.y, block.z)
        vector.new(block.xoff, block.yoff, block.zoff)
    )
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)
    process({ block })
    -- 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