--[[

     Licensed under GNU General Public License v2
      * (c) 2014,      projektile
      * (c) 2013,      Luca CPZ
      * (c) 2010,      Nicolas Estibals
      * (c) 2010-2012, Peter Hofmann

--]]

local math = math
local screen = screen
local tonumber = tonumber

local termfair = { name = 'termfair' }
termfair.center = { name = 'centerfair' }
termfair.stable = { name = 'stablefair' }

local function do_fair(p, orientation)
	local t = p.tag or screen[p.screen].selected_tag
	local wa = p.workarea
	local cls = p.clients

	if #cls == 0 then
		return
	end

	-- How many vertical columns? Read from nmaster on the tag.
	local num_x = tonumber(termfair.nmaster) or t.master_count
	local ncol = tonumber(termfair.ncol) or t.column_count
	if num_x <= 2 then
		num_x = 2
	end
	if ncol <= 1 then
		ncol = 1
	end
	local width = math.floor(wa.width / num_x)

	if orientation == 'west' then
		-- Layout with fixed number of vertical columns (read from nmaster).
		-- New windows align from left to right. When a row is full, a new
		-- one above it is created. Like this:

		--        (1)                (2)                (3)
		--   +---+---+---+      +---+---+---+      +---+---+---+
		--   |   |   |   |      |   |   |   |      |   |   |   |
		--   | 1 |   |   |  ->  | 1 | 2 |   |  ->  | 1 | 2 | 3 |  ->
		--   |   |   |   |      |   |   |   |      |   |   |   |
		--   +---+---+---+      +---+---+---+      +---+---+---+

		--        (4)                (5)                (6)
		--   +---+---+---+      +---+---+---+      +---+---+---+
		--   | 1 |   |   |      | 1 | 2 |   |      | 1 | 2 | 3 |
		--   +---+---+---+  ->  +---+---+---+  ->  +---+---+---+
		--   | 2 | 3 | 4 |      | 3 | 4 | 5 |      | 4 | 5 | 6 |
		--   +---+---+---+      +---+---+---+      +---+---+---+

		local num_y = math.max(math.ceil(#cls / num_x), ncol)
		local height = math.floor(wa.height / num_y)
		local cur_num_x = num_x
		local at_x = 0
		local at_y = 0

		local remaining_clients = #cls

		-- We start the first row. Left-align by limiting the number of
		-- available slots.
		if remaining_clients < num_x then
			cur_num_x = remaining_clients
		end

		-- Iterate in reversed order.
		for i = #cls, 1, -1 do
			-- Get x and y position.
			local c = cls[i]
			local this_x = cur_num_x - at_x - 1
			local this_y = num_y - at_y - 1

			-- Calculate geometry.
			local g = {}
			if this_x == (num_x - 1) then
				g.width = wa.width - (num_x - 1) * width
			else
				g.width = width
			end

			if this_y == (num_y - 1) then
				g.height = wa.height - (num_y - 1) * height
			else
				g.height = height
			end

			g.x = wa.x + this_x * width
			g.y = wa.y + this_y * height

			if g.width < 1 then
				g.width = 1
			end
			if g.height < 1 then
				g.height = 1
			end

			p.geometries[c] = g

			remaining_clients = remaining_clients - 1

			-- Next grid position.
			at_x = at_x + 1
			if at_x == num_x then
				-- Row full, create a new one above it.
				at_x = 0
				at_y = at_y + 1

				-- We start a new row. Left-align.
				if remaining_clients < num_x then
					cur_num_x = remaining_clients
				end
			end
		end
	elseif orientation == 'stable' then
		-- Layout with fixed number of vertical columns (read from nmaster).
		-- New windows align from left to right. When a row is full, a new
		-- one below it is created. Like this:

		--        (1)                (2)                (3)
		--   +---+---+---+      +---+---+---+      +---+---+---+
		--   |   |   |   |      |   |   |   |      |   |   |   |
		--   | 1 |   |   |  ->  | 1 | 2 |   |  ->  | 1 | 2 | 3 |  ->
		--   |   |   |   |      |   |   |   |      |   |   |   |
		--   +---+---+---+      +---+---+---+      +---+---+---+

		--        (4)                (5)                (6)
		--   +---+---+---+      +---+---+---+      +---+---+---+
		--   | 1 | 2 | 3 |      | 1 | 2 | 3 |      | 1 | 2 | 3 |
		--   +---+---+---+      +---+---+---+      +---+---+---+
		--   | 4 |   |   |      | 4 | 5 |   |      | 4 | 5 | 6 |
		--   +---+---+---+  ->  +---+---+---+  ->  +---+---+---+

		local num_y = math.max(math.ceil(#cls / num_x), ncol)
		local height = math.floor(wa.height / num_y)

		for i = #cls, 1, -1 do
			-- Get x and y position.
			local c = cls[i]
			local this_x = (i - 1) % num_x
			local this_y = math.floor((i - this_x - 1) / num_x)

			-- Calculate geometry.
			local g = {}
			if this_x == (num_x - 1) then
				g.width = wa.width - (num_x - 1) * width
			else
				g.width = width
			end

			if this_y == (num_y - 1) then
				g.height = wa.height - (num_y - 1) * height
			else
				g.height = height
			end

			g.x = wa.x + this_x * width
			g.y = wa.y + this_y * height

			if g.width < 1 then
				g.width = 1
			end
			if g.height < 1 then
				g.height = 1
			end

			p.geometries[c] = g
		end
	elseif orientation == 'center' then
		-- Layout with fixed number of vertical columns (read from nmaster).
		-- Cols are centerded until there is nmaster columns, then windows
		-- are stacked in the slave columns, with at most ncol clients per
		-- column if possible.

		-- with nmaster=3 and ncol=1 you'll have
		--        (1)                (2)                (3)
		--   +---+---+---+      +-+---+---+-+      +---+---+---+
		--   |   |   |   |      | |   |   | |      |   |   |   |
		--   |   | 1 |   |  ->  | | 1 | 2 | | ->   | 1 | 2 | 3 |  ->
		--   |   |   |   |      | |   |   | |      |   |   |   |
		--   +---+---+---+      +-+---+---+-+      +---+---+---+

		--        (4)                (5)
		--   +---+---+---+      +---+---+---+
		--   |   |   | 3 |      |   | 2 | 4 |
		--   + 1 + 2 +---+  ->  + 1 +---+---+
		--   |   |   | 4 |      |   | 3 | 5 |
		--   +---+---+---+      +---+---+---+

		if #cls < num_x then
			-- Less clients than the number of columns, let's center it!
			local offset_x = wa.x + (wa.width - #cls * width) / 2
			for i = 1, #cls do
				local g = { y = wa.y }
				g.width = width
				g.height = wa.height
				if g.width < 1 then
					g.width = 1
				end
				if g.height < 1 then
					g.height = 1
				end
				g.x = offset_x + (i - 1) * width
				p.geometries[cls[i]] = g
			end
		else
			-- More clients than the number of columns, let's arrange it!
			-- Master client deserves a special treatement
			local g = {}
			g.width = wa.width - (num_x - 1) * width
			g.height = wa.height
			if g.width < 1 then
				g.width = 1
			end
			if g.height < 1 then
				g.height = 1
			end
			g.x = wa.x
			g.y = wa.y
			p.geometries[cls[1]] = g

			-- Treat the other clients

			-- Compute distribution of clients among columns
			local num_y = {}
			local remaining_clients = #cls - 1
			local ncol_min = math.ceil(remaining_clients / (num_x - 1))

			if ncol >= ncol_min then
				for i = (num_x - 1), 1, -1 do
					if (remaining_clients - i + 1) < ncol then
						num_y[i] = remaining_clients - i + 1
					else
						num_y[i] = ncol
					end
					remaining_clients = remaining_clients - num_y[i]
				end
			else
				local rem = remaining_clients % (num_x - 1)
				if rem == 0 then
					for i = 1, num_x - 1 do
						num_y[i] = ncol_min
					end
				else
					for i = 1, num_x - 1 do
						num_y[i] = ncol_min - 1
					end
					for i = 0, rem - 1 do
						num_y[num_x - 1 - i] = num_y[num_x - 1 - i] + 1
					end
				end
			end

			-- Compute geometry of the other clients
			local nclient = 2 -- we start with the 2nd client
			local wx = g.x + g.width
			for i = 1, (num_x - 1) do
				local height = math.floor(wa.height / num_y[i])
				local wy = wa.y
				for _ = 0, (num_y[i] - 2) do
					g = {}
					g.x = wx
					g.y = wy
					g.height = height
					g.width = width
					if g.width < 1 then
						g.width = 1
					end
					if g.height < 1 then
						g.height = 1
					end
					p.geometries[cls[nclient]] = g
					nclient = nclient + 1
					wy = wy + height
				end
				g = {}
				g.x = wx
				g.y = wy
				g.height = wa.height - (num_y[i] - 1) * height
				g.width = width
				if g.width < 1 then
					g.width = 1
				end
				if g.height < 1 then
					g.height = 1
				end
				p.geometries[cls[nclient]] = g
				nclient = nclient + 1
				wx = wx + width
			end
		end
	end
end

function termfair.center.arrange(p)
	return do_fair(p, 'center')
end

function termfair.stable.arrange(p)
	return do_fair(p, 'stable')
end

function termfair.arrange(p)
	return do_fair(p, 'west')
end

return termfair