lzr_util = {}

local max_value = 255

-- Convert a 6-character color hexcode string in format RRGGBB
-- to 3 numbers red, green, blue.
lzr_util.hexcode_to_rgb = function(hexcode)
	if not hexcode or string.len(hexcode) ~= 6 then
		return
	end
	local rhex = string.sub(hexcode, 1, 2)
	local ghex = string.sub(hexcode, 3, 4)
	local bhex = string.sub(hexcode, 5, 6)
	local r = tonumber(rhex, 16)
	local g = tonumber(ghex, 16)
	local b = tonumber(bhex, 16)
	if r and g and b then
		r = math.min(255, math.max(0, r))
		g = math.min(255, math.max(0, g))
		b = math.min(255, math.max(0, b))
		return r, g, b
	end
end

-- Convert 3 numbers for red, green and blue (0-255 each)
-- to a hexadecical code of length 6 in format RRGGBB.
lzr_util.rgb_to_hexcode = function(r, g, b)
	return string.format("%02X%02X%02X", r, g, b)
end

-- Converts RGB values (0..255 each) to HSV values (0..1 each)
lzr_util.rgb_to_hsv = function(r, g, b)
	r = r / max_value
	g = g / max_value
	b = b / max_value

	local max = math.max(r, g, b)
	local min = math.min(r, g, b)
	local h, s, v = 0, 0, (max + min) / 2

	local d = max - min
	v = max
	s = max == 0 and 0 or d / max

	if max ~= min then
		if max == r then
			h = (g - b) / d + (g < b and 6 or 0)
		elseif max == g then
			h = (b - r) / d + 2
		elseif max == b then
			h = (r - g) / d + 4
		end
		h = h / 6
	end
	return h, s, v
end

-- Converts HSV values (0..1 each) to RGB values (0..255 each)
lzr_util.hsv_to_rgb = function(h, s, v)
	local r, g, b

	local i = math.floor(h * 6)
	local f = h * 6 - i
	local p = v * (1 - s)
	local q = v * (1 - f * s)
	local t = v * (1 - (1 - f) * s)

	i = i % 6

	if i == 0 then
		r, g, b = v, t, p
	elseif i == 1 then
		r, g, b = q, v, p
	elseif i == 2 then
		r, g, b = p, v, t
	elseif i == 3 then
		r, g, b = p, q, v
	elseif i == 4 then
		r, g, b = t, p, v
	elseif i == 5 then
		r, g, b = v, p, q
	end

        return math.floor(r * max_value), math.floor(g * max_value), math.floor(b * max_value)
end

-- Returns true if the given file exists, false otherwise.
-- * path: Path to file (without file name)
-- * filename: File name of file (without path)
lzr_util.file_exists = function(path, filename)
	local levels = minetest.get_dir_list(path, false)
	for l=1, #levels do
		if levels[l] == filename then
			return true
		end
	end
	return false
end