-- resumable signed-volume miner with start offset, slow start, return+dual-dump
local ST="mine_state.txt"
local t=turtle

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

local function digf() while t.detect() do t.dig() end end
local function dgu() while t.detectUp() do t.digUp() end end
local function dgd() while t.detectDown() do t.digDown() end end

local S=load()
if not S then
  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)")
    local OX=rd("OffX (signed fwd/back; stand beside first mined)")
    local OY=rd("OffY (signed up/down)")
    local OZ=rd("OffZ (signed right/left)")
    S={
      xlen=math.abs(X), ylen=math.abs(Y), zlen=math.abs(Z),
      xneg=X<0, yneg=Y<0, zneg=Z<0,
      x=1, y=1, z=1, dir=0,
      ox=OX, oy=OY, oz=OZ, at_off=false,
      slow=10,
      px=0,py=0,pz=0, h=0, sh=0
    }
    save(S)
  end
end

local function TL() t.turnLeft();  S.h=(S.h+3)%4 end
local function TR() t.turnRight(); S.h=(S.h+1)%4 end
local function T2() TL(); TL() end
local function face(d) while S.h~=d do if (d-S.h)%4==1 then TR() else TL() end end end

local function tick() if S.slow and S.slow>0 then sleep(5); S.slow=S.slow-1; save(S) end end

local function F()
  local n=0
  while not t.forward() do t.attack(); digf(); n=n+1; if n>50 then return end end
  if S.h==0 then S.px=S.px+1 elseif S.h==1 then S.pz=S.pz+1 elseif S.h==2 then S.px=S.px-1 else S.pz=S.pz-1 end
  tick(); save(S)
end
local function U()
  local n=0
  while not t.up() do t.attackUp(); dgu(); n=n+1; if n>50 then return end end
  S.py=S.py+1; tick(); save(S)
end
local function D()
  local n=0
  while not t.down() do t.attackDown(); dgd(); n=n+1; if n>50 then return end end
  S.py=S.py-1; tick(); save(S)
end

local function go_off()
  if S.at_off then return end
  if S.oy>0 then for i=1,S.oy do dgu(); U() end elseif S.oy<0 then for i=1,-S.oy do dgd(); D() end end
  if S.oz>0 then TR(); for i=1,S.oz do digf(); F() end; TL()
  elseif S.oz<0 then TL(); for i=1,-S.oz do digf(); F() end; TR() end
  if S.ox>0 then for i=1,S.ox do digf(); F() end
  elseif S.ox<0 then T2(); for i=1,-S.ox do digf(); F() end; T2() end
  S.at_off=true; save(S)
end

local function goto_rel(x,y,z)
  while S.py<y do dgu(); U() end
  while S.py>y do dgd(); D() end
  if S.px<x then face(0); for i=1,x-S.px do digf(); F() end
  elseif S.px>x then face(2); for i=1,S.px-x do digf(); F() end end
  if S.pz<z then face(1); for i=1,z-S.pz do digf(); F() end
  elseif S.pz>z then face(3); for i=1,S.pz-z do digf(); F() end end
end

local function dump_home()
  -- must be at (0,0,0)
  local a={["minecraft:cobblestone"]=1,["minecraft:dirt"]=1,["minecraft:gravel"]=1,["minecraft:sand"]=1}
  for s=1,16 do local d=t.getItemDetail(s); if d and a[d.name] then t.select(s); t.dropDown() end end
  face(0); digf(); F()
  dgd(); D(); dgd(); D()
  face(2)
  for s=1,16 do local d=t.getItemDetail(s); if d and not a[d.name] then t.select(s); t.drop() end end
  face(0); dgu(); U(); dgu(); U()
  face(2); digf(); F()
  face(0)
  -- now near home; ensure exact home:
  goto_rel(0,0,0)
end

go_off()
if S.xneg then T2() end

while S.y<=S.ylen do
  if S.dir==1 then T2() end
  for i=S.x,S.xlen do
    dgu(); dgd()
    local last=(i==S.xlen) and (S.z==S.zlen) and (S.y==S.ylen)
    if not last and i<S.xlen then digf(); F() end
    S.x=i+1; save(S)
  end
  S.x=1
  if S.z<S.zlen then
    if not S.zneg then TR(); digf(); F(); TR() else TL(); digf(); F(); TL() end
    S.z=S.z+1; S.dir=1-S.dir; save(S)
  else
    if S.y<S.ylen then
      if not S.yneg then dgu(); U() else dgd(); D() end
      if (S.z%2)==1 then T2(); for i=1,S.xlen-1 do digf(); F() end; T2() end
      S.y=S.y+1; S.z=1; S.dir=0; save(S)
    else break end
  end
end

goto_rel(0,0,0)
dump_home()
goto_rel(0,0,0)
face(S.sh)
if fs.exists(ST) then fs.delete(ST) end
print("done")