path: root/util.lua

-- Copyright 2025 David Vazgenovich Shakaryan

local mp_utils = require('mp.utils')

local util = {}

function util.copy_table(t)
	local u = {}
	for k, v in pairs(t) do
		u[k] = v
	end
	return u
end

function util.reverse(t)
	for i = 1, #t/2 do
		t[i], t[#t-i+1] = t[#t-i+1], t[i]
	end
end

function util.strip(str)
	return (str:gsub('^%s*(.-)%s*$', '%1'))
end

function util.strip_ne(str)
	if str == nil then
		return nil
	end
	local str = util.strip(tostring(str))
	return str ~= '' and str or nil
end

-- skips over utf8 continuation bytes (10xxxxxx)
-- valid positions range from 1 to #str + 1 (*after* the last byte)
function util.utf8_seek(str, pos, n)
	local step = n > 0 and 1 or -1
	local test = n > 0
		and function() return pos > #str end
		or function() return pos <= 1 end

	while n ~= 0 and not test() do
		repeat
			pos = pos + step
		until test() or bit.band(str:byte(pos), 0xc0) ~= 0x80

		n = n - step
	end
	return pos
end

-- wraps string into a table of strings. spaces are not removed, resulting in
-- width-1 visible chars; newlines and end of string are handled similarly for
-- consistency. words longer than width are not broken. optional cont_width can
-- be specified to use a different width for continuation lines.
function util.wrap(str, width, cont_width)
	local t = {}
	local start, stop = 0, 0
	while stop < #str do
		local i = str:find('[ \n]', stop + 1) or #str + 1
		if i - start >= width then
			t[#t+1] = str:sub(start, stop)
			start = stop + 1

			if cont_width then
				width = cont_width
			end
		end
		stop = i

		if str:byte(stop) == 10 or stop >= #str then
			t[#t+1] = str:sub(start, stop - 1) .. ' '
			start = stop + 1
		end
	end
	return t
end

function util.read_json_file(path)
	local f = io.open(path, 'r')
	if not f then
		return {}
	end
	local json = f:read('*all')
	f:close()
	return mp_utils.parse_json(json)
end

function util.write_json_file(path, data)
	local f = io.open(path, 'w')
	f:write(mp_utils.format_json(data), '\n')
	f:close()
end

-- merges tables `t' and `u', using key `k' for identity. the order from `u' is
-- always respected, preserving the relative order from `t' when possible.
function util.stable_kmerge(t, u, k)
	local pos = {}
	for i, v in ipairs(u) do
		pos[v[k]] = i
	end

	local res = {}
	local seen = {}
	local function append(v)
		if not seen[v[k]] then
			res[#res+1] = v
			seen[v[k]] = true
		end
	end

	local ind = 1
	for _, v in ipairs(t) do
		if pos[v[k]] then
			while ind <= pos[v[k]] do
				append(u[ind])
				ind = ind + 1
			end
		end
		append(v)
	end
	for i = ind, #u do
		append(u[i])
	end

	return res
end

function util.flatten_table(src, dst, prefix)
	local dst = dst or {}
	for k, v in pairs(src) do
		local k = prefix and prefix .. '.' .. k or k
		if type(v) == 'table' then
			util.flatten_table(v, dst, k)
		else
			dst[k] = v
		end
	end
	return dst
end

function util.unflatten_table(src, dst)
	local dst = dst or {}
	for k, v in pairs(src) do
		local t = dst
		local prev
		for curr in (k .. '.'):gmatch('(.-)%.') do
			if prev then
				t[prev] = t[prev] or {}
				t = t[prev]
			end
			prev = curr
		end
		t[prev] = v
	end
	return dst
end

function util.find_matches(str, substr, case_sensitive)
	if not str then
		return
	end

	if not case_sensitive then
		str = str:lower()
	end

	local matches
	local i, j = 0, 0
	while true do
		i, j = str:find(substr, j + 1, true)
		-- j < i avoids infinite loop on empty substr
		if not i or j < i then
			break
		end
		matches = matches or {}
		matches[#matches+1] = {start = i, stop = j}
	end
	return matches or i and {}
end

function util.str_seek_prev_char(str, pos)
	return util.utf8_seek(str, pos, -1)
end

function util.str_seek_next_char(str, pos)
	return util.utf8_seek(str, pos, 1)
end

function util.str_seek_prev_word(str, pos)
	return str:sub(1, pos - 1):match('()%S*%s*$')
end

function util.str_seek_next_word(str, pos)
	return str:match('%s*%S*()', pos)
end

function util.str_insert_char(str, pos, ch)
	return str:sub(1, pos - 1) .. ch .. str:sub(pos), pos + #ch
end

function util.str_del_prev_char(str, pos)
	if pos <= 1 then
		return
	end

	local npos = util.utf8_seek(str, pos, -1)
	return str:sub(1, npos - 1) .. str:sub(pos), npos
end

function util.str_del_next_char(str, pos)
	if pos > #str then
		return
	end

	return str:sub(1, pos - 1) .. str:sub(util.utf8_seek(str, pos, 1)), pos
end

function util.str_del_prev_word(str, pos)
	if pos <= 1 then
		return
	end

	local npos = str:sub(1, pos - 1):match('()%S*%s*$')
	return str:sub(1, npos - 1) .. str:sub(pos), npos
end

function util.str_del_next_word(str, pos)
	if pos > #str then
		return
	end

	return str:sub(1, pos - 1) .. str:sub(str:match('%s*%S*()', pos)), pos
end

function util.str_del_to_start(str, pos)
	if pos <= 1 then
		return
	end

	return str:sub(pos), 1
end

function util.str_del_to_end(str, pos)
	if pos > #str then
		return
	end

	return str:sub(1, pos - 1), pos
end

function util.str_transpose_chars(str, pos)
	if pos <= 1 then
		return
	end

	local npos = util.utf8_seek(str, pos, 1)
	local cp2 = util.utf8_seek(str, npos, -1)
	if cp2 <= 1 then
		return
	end
	local cp1 = util.utf8_seek(str, cp2, -1)

	return str:sub(1, cp1 - 1) .. str:sub(cp2, npos - 1) ..
			str:sub(cp1, cp2 - 1) .. str:sub(npos),
		npos
end

function util.str_transpose_words(str, pos)
	if pos <= 1 then
		return
	end

	local npos = str:match('%s*%S*()', pos)
	local pre, w1, sp, w2 = str:sub(1, npos - 1):match(
		'^(.-)(%S+)(%s+)(%S+%s*)$')
	if not pre then
		return
	end

	return pre .. w2 .. sp .. w1 .. str:sub(npos), npos
end

return util