-- minimal resumable volume miner w/ signed dims and quit/resume
local ST="mine_state.txt"

local function rd(p)
  io.write(p..": ")
  local s=read()
  if not s then return nil end
  s=s:lower()
  if s=="quit" then print("bye") error() end
  if s=="resume" then return "resume" end
  local n=tonumber(s); if not n then print("num/quit/resume"); return rd(p) end
  return n
end

local function save(S)
  local h=fs.open(ST,"w"); h.write(textutils.serialize(S)); h.close()
end
local function load()
  if not fs.exists(ST) then return nil end
  local h=fs.open(ST,"r"); local s=h.readAll(); h.close()
  return textutils.unserialize(s)
end

-- moves
local t=turtle
local function digf() while t.detect() do t.dig() end end
local function df() while not t.forward() do t.attack(); digf() end end
local function dug() while t.detectUp() do t.digUp() end end
local function ddn() while t.detectDown() do t.digDown() end end
local function up() while not t.up() do t.attackUp(); dug() end end
local function dn() while not t.down() do t.attackDown(); ddn() end end

-- state (progress)
local S = load()
if S=="resume" then S=nil end
if S then
  print("resuming")
else
  local X=rd("X (signed, fwd/back)"); if X=="resume" then S=load() end
  if not S then
    local Y=rd("Y (signed, up/down)")
    local Z=rd("Z (signed, right/left serpentine)")
    local xlen=math.abs(X); local ylen=math.abs(Y); local zlen=math.abs(Z)
    local xneg = X<0; local yneg = Y<0; local zneg = Z<0
    -- starting facing: forward mines along +X; flip if X<0
    if xneg then t.turnLeft(); t.turnLeft() end
    S={xlen=xlen,ylen=ylen,zlen=zlen,x=1,y=1,z=1,dir=0,xneg=xneg,yneg=yneg,zneg=zneg,started=true}
    save(S)
  end
end

-- helpers to go to next line and layer based on signs
local function next_row(S)
  if S.z>=S.zlen then return false end
  if not S.zneg then
    t.turnRight(); digf(); df(); t.turnRight()
  else
    t.turnLeft(); digf(); df(); t.turnLeft()
  end
  S.z=S.z+1; S.dir=1-S.dir; save(S)
  return true
end

local function next_layer(S)
  if S.y>=S.ylen then return false end
  if not S.yneg then dug(); up() else ddn(); dn() end
  -- reset row to 1 and go to row start
  if S.z%2==1 then
    -- we ended at row end; go back to row start for new layer
    t.turnLeft(); t.turnLeft()
    for i=1,S.xlen-1 do digf(); df() end
    t.turnLeft(); t.turnLeft()
  end
  -- go to first row start cell in new layer
  S.y=S.y+1; S.z=1; S.dir=0; save(S)
  return true
end

-- main loop: layers -> rows -> cells
while S.y<=S.ylen do
  -- at start of a row, face correct dir
  if S.dir==0 then
    -- face forward
  else
    t.turnLeft(); t.turnLeft()
  end
  -- advance along X for remaining cells in this row
  local startx = S.x
  for i=startx,S.xlen do
    -- mine current cell
    dug(); ddn()
    -- move forward unless last cell of last row/layer
    local last = (i==S.xlen) and (S.z==S.zlen) and (S.y==S.ylen)
    if not last then
      if i<S.xlen then digf(); df() end
    end
    S.x = i+1; save(S)
  end
  -- row done
  S.x=1
  if not next_row(S) then
    -- rows done in this layer
    if not next_layer(S) then break end
  end
end

-- finished: delete state and dump dirt/cobble
if fs.exists(ST) then fs.delete(ST) end
for s=1,16 do
  local d=t.getItemDetail(s)
  if d and (d.name=="minecraft:dirt" or d.name=="minecraft:cobblestone") then
    t.select(s); t.dropDown()
  end
end
print("done")