local Y=require("yaru.core")
local gfx=require("yaru.gfx")
local ui=require("yaru.ui")
local computer=require("computer")
local M={}
local LEVELS={{"Easy",36},{"Medium",46},{"Hard",53}}

local function solve(g,i)
i=i or 1
while i<=81 and g[i]~=0 do i=i+1 end
if i>81 then return true end
local r,c=(i-1)//9,(i-1)%9
local used={}
for k=0,8 do
used[g[r*9+k+1]]=true
used[g[k*9+c+1]]=true
used[g[((r//3)*3+k//3)*9+(c//3)*3+k%3+1]]=true
end
local digits={1,2,3,4,5,6,7,8,9}
for k=9,2,-1 do local j=math.random(k)digits[k],digits[j]=digits[j],digits[k]end
for _,d in ipairs(digits)do
if not used[d]then
g[i]=d
if solve(g,i+1)then return true end
end
end
g[i]=0
return false
end

function M.open()
local st={sel=41}
local win=Y.newWindow{app="sudoku",title="Sudoku",w=62,h=33,fixed=true}
local function new(li)
st.level=li or st.level or 1
local sol={}
for i=1,81 do sol[i]=0 end
solve(sol)
st.sol,st.g,st.given=sol,{},{}
for i=1,81 do st.g[i]=sol[i]end
local removed=0
while removed<LEVELS[st.level][2]do
local i=math.random(81)
if st.g[i]~=0 then st.g[i]=0;st.g[82-i]=0;removed=removed+(i==41 and 1 or 2)end
end
for i=1,81 do st.given[i]=st.g[i]~=0 end
st.t0,st.done=computer.uptime(),nil
end
local function conflict(i)
local v=st.g[i]
if v==0 then return false end
local r,c=(i-1)//9,(i-1)%9
for k=0,8 do
local a,b=r*9+k+1,k*9+c+1
local q=((r//3)*3+k//3)*9+(c//3)*3+k%3+1
if(a~=i and st.g[a]==v)or(b~=i and st.g[b]==v)or(q~=i and st.g[q]==v)then return true end
end
return false
end
local function set(v)
if st.done or st.given[st.sel]then return end
st.g[st.sel]=v
for i=1,81 do if st.g[i]==0 or conflict(i)then return end end
st.done=computer.uptime()-st.t0
Y.notify("Sudoku solved!",string.format("%s puzzle in %d:%02d",LEVELS[st.level][1],st.done//60,math.floor(st.done%60)))
end
function win.header(w,hw)
local x=2
for i,L in ipairs(LEVELS)do x=x+ui.button(w,x,1,L[1],function()new(i)end,i==st.level and nil or"flat")+1 end
end
function win.draw(w,cw,ch)
local t=Y.theme
w.tickInterval=st.done and nil or 1
local el=st.done or(computer.uptime()-st.t0)
local tm=string.format("◷ %d:%02d",el//60,math.floor(el%60))
gfx.text(cw-#tm-1,1,tm,st.done and t.success or t.dim)

local CW,CH=5,5
local function off(k)return k*(CW+1)+(k//3)end
local function offy(k)return k*(CH+1)+(k//3)end
local gw=off(9)+1
local ox,oy=(cw-gw)//2+1,5
local grid=t.dark and 0x5E5C64 or 0x969696
gfx.prrect(ox-1,oy-1,gw+1,offy(9)+2,grid)
local sr,sc=(st.sel-1)//9,(st.sel-1)%9
for i=1,81 do
local r,c=(i-1)//9,(i-1)%9
local x,y=ox+off(c),oy+offy(r)
local related=r==sr or c==sc or(r//3==sr//3 and c//3==sc//3)
local bg=t.dark and 0x1E1E1E or 0xFFFFFF
if related then bg=t.dark and 0x2D2D2D or 0xEBEBEB end
if selV~=0 and st.g[i]==selV then bg=t.dark and 0x454545 or 0xDEDDDA end
if i==st.sel then bg=t.accent end
gfx.prect(x,y,CW,CH,bg)
local v=st.g[i]
local tr=y+1
if tr%2==0 then tr=tr+1 end
if v~=0 then
local fg=st.given[i]and t.fg or(t.dark and 0x6D92FF or 0x0049BF)
if conflict(i)then fg=t.danger end
if i==st.sel then fg=0xFFFFFF end
gfx.text(x+2,(tr+1)//2,tostring(v),fg,bg)
end
local idx=i
ui.hit(w,x,(y+1)//2,CW,2,function()st.sel=idx end)
end
local py=(oy+offy(9)+3)//2+1

for d=1,9 do
ui.button(w,ox+(d-1)*6,py,tostring(d),function()set(d)end,nil,5)
end
ui.button(w,ox+54,py,"⌫",function()set(0)end,"flat",3)
end
function win.tick(w)Y.redraw(w)end
function win.key(w,char,code)
local K=Y.K
if code==K.left then st.sel=st.sel-1<1 and st.sel or st.sel-1
elseif code==K.right then st.sel=math.min(81,st.sel+1)
elseif code==K.up then st.sel=st.sel>9 and st.sel-9 or st.sel
elseif code==K.down then st.sel=st.sel<=72 and st.sel+9 or st.sel
elseif code==K.del or code==K.back or char==48 then set(0)
elseif char and char>=49 and char<=57 then set(char-48)end
end
new(1)
return win
end

return M