local disp_common = require("disp_common")

-- a vlorb consists of six gromlings[A
-- 1  2
-- 4  8
-- 16 Q
-- these are characters 0x80 through 0x9f in the cc charset
-- which is only 2^5 characters though. for the sixth bit you flip the colours
-- of that vlorb.

-- on colour, off colour, gromlings 1 through 6 (bools)
-- returns text colour, bg color, and vlorbchar
local function vlorb(onc,offc, g1,g2,g3,g4,g5,g6)
	local textc,bgc = onc,offc
	if g6 then textc,bgc=bgc,textc end
	local vlorbchar = 0x80
	-- ~= on booleans is xor
	-- if g6 set then flip all the other bits
	if g1 ~= g6 then vlorbchar=vlorbchar+1  end
	if g2 ~= g6 then vlorbchar=vlorbchar+2  end
	if g3 ~= g6 then vlorbchar=vlorbchar+4  end
	if g4 ~= g6 then vlorbchar=vlorbchar+8  end
	if g5 ~= g6 then vlorbchar=vlorbchar+16 end
	return textc,bgc,string.char(vlorbchar)
end

local function all_palette_distances(R)
	local out = {}
	for a=0,15 do
		local ia=2^a
		out[ia] = {}
		for b = 0,15 do
			local ib=2^b
			local ca = {R.getPaletteColor(ia)}
			local cb = {R.getPaletteColor(ib)}
			local dist = disp_common.color_dist(ca,cb)
			out[ia][ib] = dist
		end
	end
	return out
end

local function list_contains(list,val)
	for _,v in ipairs(list) do
		if v == val then return true end
	end
	return false
end

-- R, lPx_gromlings, l_pdists  -> lCx_gromlings
local function adjust_to_2_colors(R,gromlings,pdists)
	-- gromlings goes 1 2 3 4 5 6
	-- compress the 6 pixels to just 2 colors
	-- return the list of cidxs
	local gromling_colors = {}
	for i,c in ipairs(gromlings) do
		local cx = disp_common.closest_palette_color(R,c)
		gromling_colors[i] = cx
	end

	local all_current_colors = {}
	local ncolors = 0
	for _,cidx in ipairs(gromling_colors) do
		if not all_current_colors[cidx] then ncolors = ncolors + 1 end
		all_current_colors[cidx] = true
	end


	while ncolors > 2 do
		-- print("- ncolors is "..ncolors)

		-- io.write("all_current_colors: ")
		-- for k in pairs(all_current_colors) do io.write(k," ") end
		-- io.write("\ngromling_colors: ")
		-- for k,v in pairs(gromling_colors) do print(k,v) end
		--print()
		
		-- merge closest two colors until there are only 2 distinct ones left
		local best_dist = 9999
		local best_a = nil
		local best_b = nil
		for a in pairs(all_current_colors) do
			for b in pairs(all_current_colors) do
				if a ~= b then
					local dist = pdists[a][b]
					assert(dist)
					if dist < best_dist then
						best_dist = dist
						best_a = a
						best_b = b
					end
				end
			end
		end

		-- todo: be cleverer when deciding whether to merge a into b, or b into a
		-- currently just merge b into a
		assert(best_a,"no best_a")
		assert(best_b,"no best_b")
		assert(best_a ~= best_b,"best a and b are the same")
		--print("mergng "..best_b.." into "..best_a)
		all_current_colors[best_b] = nil
		ncolors=ncolors-1
		for gidx,col in ipairs(gromling_colors) do
			if col == best_b then gromling_colors[gidx] = best_a end
		end

		

	end
		--print("-#-- ncolors is "..ncolors)

		--io.write("all_current_colors: ")
		--for k in pairs(all_current_colors) do io.write(k," ") end
		--io.write("\ngromling_colors: ")
		--for k,v in pairs(gromling_colors) do print(k,v) end
		--print()

	return gromling_colors
end

local function gromling_list_to_vlorb(gromling_colors)
	-- takes list of cidxs 
	local ca = nil
	local cb = nil
	local gs = {}
	for i,col in ipairs(gromling_colors) do
		if col == ca then
			gs[i] = true
		elseif col == cb then
			gs[i] = false
		else
			if not ca then
				ca = col
				gs[i] = true
			elseif not cb then
				cb = col
				gs[i] = false
			else
				error("third gromling color in vlorb")
			end
		end
	end
	return ca,cb or colors.black,table.unpack(gs)
end
	

-- todo: refactor common stuff into a common file
local function disp(R,img,scrx,scry,w,h,imgx,imgy)
	-- w and h are image coords
	scrx = scrx or 1
	scry = scry or 1
	w = w or img.width
	h = h or img.width
	imgx = imgx or 1
	imgy = imgy or 1

	disp_common.improve_palette(R,img,w,h,imgx,imgy)
	local pdists=all_palette_distances(R)

	local sw = math.ceil(w/2)
	local sh = math.ceil(h/3)

	for soffx=0,sw do
		for soffy=0,sh do
			local ioffx=soffx*2
			local ioffy=soffy*3
			R.setCursorPos(scrx+soffx,scry+soffy)
			local lPx_gromlings = {}
			for goffy=0,2 do
				for goffx=0,1 do
					local px = img[imgy+ioffy+goffy][imgx+ioffx+goffx] or {0,0,0}
					table.insert(lPx_gromlings,px)
				end
			end

			local lCx_gromlings = adjust_to_2_colors(R,lPx_gromlings,pdists)
			-- for k,v in ipairs(lCx_gromlings) do print("thethe",k,v) end
			local vlorbdf = {gromling_list_to_vlorb(lCx_gromlings)}
			-- for k,v in ipairs(vlorbdf) do print("ehteht",k,v) end
			local textc,bgc,vlorbchar = vlorb(table.unpack(vlorbdf))
			R.setTextColor(textc)
			R.setBackgroundColor(bgc)
			R.write(vlorbchar)
		end
	end
end

return {vlorb=vlorb,disp=disp}