path.lua

--Path manipulation for Windows and UNIX paths.
--Written by Cosmin Apreutesei. Public Domain.

if not ... then require'path_test'; return end

local path = {}
setmetatable(path, path)

path.platform = package.config:sub(1, 1) == '\\' and 'win' or 'unix'

local function win(pl) --check if pl (or current platform) is Windows
	if pl == nil then pl = path.platform end
	assert(pl == 'unix' or pl == 'win', 'invalid platform')
	return pl == 'win'
end

function path.default_sep(pl)
	return win(pl) and '\\' or '/'
end

--device aliases are file names that are found _in any directory_.
local dev_aliases = {
	CON=1, PRN=1, AUX=1, NUL=1,
	COM1=1, COM2=1, COM3=1, COM4=1, COM5=1, COM6=1, COM7=1, COM8=1, COM9=1,
	LPT1=1, LPT2=1, LPT3=1, LPT4=1, LPT5=1, LPT6=1, LPT7=1, LPT8=1, LPT9=1,
}

--check if a path refers to a device alias and return that alias.
function path.dev_alias(s)
	s = s:match'[^\\/]+$' --basename (dev aliases are present in all dirs)
	s = s and s:match'^[^%.]+' --strip extension (they can have any extension)
	s = s and s:upper() --they're case-insensitive
	return s and dev_aliases[s] and s
end

--get the path type which can be: 'abs', 'abs_long', 'abs_nodrive',
--  'rel', 'rel_drive', 'unc', 'unc_long', 'global', 'dev', 'dev_alias'.
--NOTE: the empty path ('') comes off as type 'rel'.
function path.type(s, pl)
	if win(pl) then
		if s:find'^\\\\' then
			if s:find'^\\\\%?\\' then
				if s:find'^\\\\%?\\%a:\\' then
					return 'abs_long'
				elseif s:find'^\\\\%?\\[uU][nN][cC]\\' then
					return 'unc_long'
				else
					return 'global'
				end
			elseif s:find'^\\\\%.\\' then
				return 'dev'
			else
				return 'unc'
			end
		elseif path.dev_alias(s) then
			return 'dev_alias'
		elseif s:find'^%a:' then
			return s:find'^..[\\/]' and 'abs' or 'rel_drive'
		else
			return s:find'^[\\/]' and 'abs_nodrive' or 'rel'
		end
	else
		return s:byte(1) == ('/'):byte(1) and 'abs' or 'rel'
	end
end

--split a path into its local path component and, depending on the path
--type, the drive letter or server name.
--NOTE: UNC paths are not validated and can have and empty server or path.
function path.parse(s, pl)
	local type = path.type(s, pl)
	if win(pl) then
		if type == 'rel' or type == 'abs_nodrive' then
			return type, s -- nothing to split
		elseif type == 'abs' or type == 'rel_drive' then
			return type, s:sub(3), s:sub(1,1) -- \path, drive
		elseif type == 'abs_long' then
			return type, s:sub(3+4), s:sub(1+4,1 +4) -- \path, drive
		elseif type == 'unc' then
			local server, path = s:match'^..([^\\]*)(.*)$'
			return type, path, server
		elseif type == 'unc_long' then
			local server, path = s:match'^........([^\\]*)(.*)$'
			return type, path, server
		elseif type == 'dev' then
			return type, s:sub(4) -- \path
		elseif type == 'dev_alias' then
			return type, s -- CON, NUL, ...
		elseif type == 'global' then
			return type, s:sub(4) -- \path
		end
	else
		return type, s --unix path: nothing to split
	end
end

--put together a path from its broken-down components.
function path.format(type, path, drive, pl)
	if win(pl) and type == 'abs' or type == 'rel_drive' then
		return drive .. ':' .. path
	elseif type == 'abs_long' then
		return '\\\\?\\' .. drive .. ':' .. path
	elseif type == 'unc' then
		return '\\\\' .. drive .. path
	elseif type == 'unc_long' then
		return '\\\\?\\UNC\\' .. drive .. path
	elseif type == 'dev' then
		return '\\\\.' .. path
	elseif type == 'global' then
		return '\\\\?' .. path
	else --abs/unix, rel, abs_nodrive, dev_alias
		return path
	end
end

--check if a path is an absolute path or not, if it's empty or not,
--and if it's valid or not. NOTE: absolute paths for which their local path
--is '' are actually invalid (currently only UNC paths can be invalid and
--still parse); for those paths the third return value will be false.
local function isabs(type, p, win)
	if type == 'rel' or type == 'rel_drive' or type == 'dev_alias' then
		return false, p == '', true
	elseif p == '' then
		return true, true, false --invalid absolute path
	else
		local isroot = p:find(win and '^[\\/]+$' or '^/+$') and true or false
		return true, isroot, true
	end
end
function path.isabs(s, pl)
	local type, p = path.parse(s, pl)
	return isabs(type, p, win(pl))
end

--determine a path's separator if possible.
local function detect_sep(p, win)
	if win then
		local fws = p:find'[^/]*/'
		local bks = p:find'[^\\/]*\\'
		if not fws == not bks then
			return nil --can't determine
		end
		return fws and '/' or '\\'
	else
		return '/'
	end
end

--get/add/remove ending separator.
local function set_endsep(type, p, win, sep, default_sep)
	local _, isempty = isabs(type, p, win)
	if isempty then --refuse to change empty paths
		return
	elseif sep == false or sep == '' then --remove it
		return p:gsub(win and '[\\/]+$' or '/+$', '')
	elseif p:find(win and '[\\/]$' or '/$') then --add it/already set
		return p
	else
		if sep == true then
			sep = detect_sep(p, win) or default_sep or (win and '\\' or '/')
		end
		assert(sep == '\\' or sep == '/', 'invalid separator')
		return p .. sep
	end
end
function path.endsep(s, pl, sep, default_sep)
	local win = win(pl)
	local type, p, drive = path.parse(s, pl)
	if sep == nil then
		return p:match(win and '[\\/]+$' or '/+$')
	else
		local p = set_endsep(type, p, win, sep, default_sep)
		return p and path.format(type, p, drive, pl) or s, p and true or false
	end
end

--detect or set a path's separator (for Windows paths only).
--NOTE: setting '\' on a UNIX path may result in an invalid path because
--`\` is a valid character in UNIX filenames!
local function set_sep(p, win, sep, default_sep, empty_names)
	local dsep = default_sep or (win and '\\' or '/')
	if sep == true then --set to default
		sep = dsep
	elseif sep == false then --set to default only if mixed
		sep = detect_sep(p, win) or dsep
	elseif sep == nil then --collapse only
		sep = '%1'
	else
		assert(sep == '\\' or sep == '/', 'invalid separator')
	end
	if empty_names then
		return p:gsub(win and '[\\/]' or '/', sep)
	else
		return p:gsub(win and '([\\/])[\\/]*' or '(/)/*', sep)
	end
end
function path.sep(s, pl, sep, default_sep, empty_names)
	local win = win(pl)
	local type, p, drive = path.parse(s, pl)
	if sep == nil and empty_names == nil then
		return detect_sep(p, win)
	else
		p = set_sep(p, win, sep, default_sep, empty_names)
		return path.format(type, p, drive, pl)
	end
end

function path.long(s, pl, long)
	local type, p, drive = path.parse(s, pl)
	local is_long = type == 'abs_long' or type == 'unc_long'
	local is_short = (win(pl) and type == 'abs') or type == 'unc'
	if long == nil then
		if is_long then
			return true
		elseif is_short then
			return false
		else
			return nil --does not apply
		end
	end
	if
		is_short and (long == true or (long == 'auto' and #s > 259))
	then
		p = p:gsub('/+', '\\') --NOTE: this might create a smaller path
		local long_type = type == 'abs' and 'abs_long' or 'unc_long'
		s = path.format(long_type, p, drive, pl)
	elseif
		is_long and (long == false or (long == 'auto' and #s <= 259 + 4))
	then
		local short_type = type == 'abs_long' and 'abs' or 'unc'
		s = path.format(short_type, p, drive, pl)
	end
	return s
end

--get the last path component of a path.
--if the path ends in a separator then the empty string is returned.
function path.file(s, pl)
	local _, p = path.parse(s, pl)
	return p:match(win(pl) and '[^\\/]*$' or '[^/]*$')
end

--get the filename without extension and the extension from a path.
function path.nameext(s, pl)
	local patt = win(pl) and '^(.-)%.([^%.\\/]*)$' or '^(.-)%.([^%./]*)$'
	local file = path.file(s, pl)
	local name, ext = file:match(patt)
	if not name or name == '' then -- 'dir' or '.bashrc'
		name, ext = file, nil
	end
	return name, ext
end

function path.ext(s, pl)
	return (select(2, path.nameext(s, pl)))
end

--get a path without basename and separator. if the path ends with
--a separator then the whole path without the separator is returned.
function path.dir(s, pl)
	local type, p, drive = path.parse(s, pl)
	if p == '' or p == '.' then --current dir has no dir
		return nil
	end
	local i1, i2, i3 = p:match(win(pl)
		and '()[\\/]*()[^\\/]*()$' or '()/*()[^/]*()$')
	if i1 == 1 and i3 == i2 then --root dir has no dir
		return nil
	end
	local i = i1 == 1 and i2 or i1
	local s = path.format(type, p:sub(1, i-1), drive, pl)
	return s == '' and '.' or s --fix '' as '.'
end

--iterate over a path's components and separators.
function path.gsplit(s, pl, full)
	local win = win(pl)
	local p = full and s or select(2, path.parse(s, pl))
	local root_sep = p:match(win and '^[\\/]+' or '^/+')
	local next_pc = p:gmatch(win and '([^\\/]+)([\\/]*)' or '([^/]+)(/*)')
	local started = not root_sep
	return function()
		if not started then
			started = true
			return '', root_sep
		elseif started then
			return next_pc()
		end
	end
end

local function iif(a, b, c)
	if a == b then
		return c
	else
		return a
	end
end

-- remove `.` dirs (opt.dot_dirs)
-- remove unnecessary `..` dirs (opt.dot_dot_dirs)
-- normalize separator (opt.sep, opt.default_sep, opt.empty_names)
-- add/remove ending separator (opt.endsep)
-- convert between long and short Windows path encodings (opt.long)
function path.normalize(s, pl, opt)
	opt = opt or {}
	local win = win(pl)
	local type, p, drive = path.parse(s, pl)

	local t = {} --{dir1, sep1, ...}
	local lastsep --last separator that was not added to the list
	for s, sep in path.gsplit(p, pl, true) do
		if s == '.' and not opt.dot_dirs then
			--skip adding the `.` dir and the separator following it
			lastsep = sep
		elseif s == '..' and not opt.dot_dot_dirs and #t > 0 then
			--find the last dir past any `.` dirs, in case opt.dot_dirs = true.
			local i = #t-1
			while t[i] == '.' do
				i = i - 2
			end
			--remove the last dir (and the separator following it)
			--that's not `..` and it's not the root element.
			if i > 0 and ((i > 1 or t[i] ~= '') and t[i] ~= '..') then
				table.remove(t, i)
				table.remove(t, i)
				lastsep = sep
			elseif #t == 2 and t[1] == '' then
				--skip any `..` after the root slash
				lastsep = sep
			else
				table.insert(t, s)
				table.insert(t, sep)
			end
		else
			table.insert(t, s)
			table.insert(t, sep)
			lastsep = nil
		end
	end
	if type == 'rel' and #t == 0 then
		--rel path '' is invalid. fix that.
		table.insert(t, '.')
		table.insert(t, lastsep)
	elseif lastsep == '' and (#t > 2 or t[1] ~= '') then
		--if there was no end separator originally before removing path
		--components, remove the left over end separator now.
		table.remove(t)
	end
	p = table.concat(t)

	if opt.sep ~= 'leave' then
		p = set_sep(p, win, iif(opt.sep, nil, false),
			opt.default_sep, opt.empty_names)
	end

	if opt.endsep ~= 'leave' then
		p = set_endsep(type, p, win, iif(opt.endsep, nil, false),
			opt.default_sep) or p
	end

	s = path.format(type, p, drive, pl)

	if win and opt.long ~= 'leave' then
		s = path.long(s, pl, iif(opt.long, nil, 'auto'))
	end

	return s
end

--get the common base path (including the end separator if it's common)
--between two paths.
--BUG: the case-insensitive comparison doesn't work with utf8 paths!
function path.commonpath(s1, s2, pl)
	local win = win(pl)
	local t1, p1, d1 = path.parse(s1, pl)
	local t2, p2, d2 = path.parse(s2, pl)
	local t, p, d
	if #p1 <= #p2 then --pick the smaller/first path when formatting
		t, p, d = t1, p1, d1
	else
		t, p, d = t2, p2, d2
	end
	if win then --make the search case-insensitive and normalize separators
		d1 = d1 and d1:lower()
		d2 = d2 and d2:lower()
		p1 = p1:lower():gsub('/', '\\')
		p2 = p2:lower():gsub('/', '\\')
	end
	if t1 ~= t2 or d1 ~= d2 then
		return nil
	elseif p1 == '' or p2 == '' then
		return path.format(t, p, d, pl)
	end
	local sep = (win and '\\' or '/'):byte(1)
	local si = 0 --index where the last common separator was found
	for i = 1, #p + 1 do
		local c1 = p1:byte(i)
		local c2 = p2:byte(i)
		local sep1 = c1 == nil or c1 == sep
		local sep2 = c2 == nil or c2 == sep
		if sep1 and sep2 then
			si = i
		elseif c1 ~= c2 then
			break
		end
	end
	p = p:sub(1, si)
	return path.format(t, p, d, pl)
end

local function depth(p, win)
	local n = 0
	for _ in p:gmatch(win and '()[^\\/]+' or '()[^/]+') do
		n = n + 1
	end
	return n
end
function path.depth(s, pl)
	local _, p = path.parse(s, pl)
	return depth(p, win(pl))
end

--combine two paths if possible.
local function combinable(type1, type2)
	if type2 == 'rel' then             -- any + c/d -> any/c/d
		return type1 ~= 'dev_alias'
	elseif type2 == 'abs_nodrive' then -- C:a/b + /c/d -> C:/c/d/a/b
		return type1 == 'rel_drive'
	elseif type2 == 'rel_drive' then   -- C:/a/b + C:c/d -> C:/a/b/c/d
		return type1 == 'abs' or type1 == 'abs_long'
	end
end
function path.combine(s1, s2, pl, sep, default_sep)
	local type1, p1, drive1 = path.parse(s1, pl)
	local type2, p2, drive2 = path.parse(s2, pl)
	if not combinable(type1, type2) then
		if combinable(type2, type1) then
			type1, type2, s1, s2, p1, p2, drive1, drive2 =
			type2, type1, s2, s1, p2, p1, drive2, drive1
		else
			return nil, ('cannot combine %s and %s paths'):format(type1, type2)
		end
	end
	if s2 == '' then -- any + '' -> any
		return s1
	elseif type2 == 'rel' or type2 == 'abs_nodrive' then
		local win = win(pl)
		local sep = sep or detect_sep(p1, win) or detect_sep(p2, win)
			or default_sep or (win and '\\' or '/')
		if type2 == 'rel' then -- any + c/d -> any/c/d
			p1 = set_endsep(type1, p1, win, sep) or p1
			return path.format(type1, p1 .. s2, drive1, pl)
		elseif type2 == 'abs_nodrive' then -- C:a/b + /d/e -> C:/d/e/a/b
			p2 = set_endsep(type2, p2, win, sep) or p2
			return path.format(type1, p2 .. p1, drive1, pl)
		end
	elseif type2 == 'rel_drive' then -- C:/a/b + C:d/e -> C:/a/b/d/e
		if drive1 ~= drive2 then
			return nil, 'path drives are different'
		end
		return path.combine(s1, p2, pl)
	end
end

--transform a relative path into an absolute path given a base dir.
path.abs = path.combine

--transform an absolute path into a relative path which is relative to `pwd`.
--the ending separator is preserved.
function path.rel(s, pwd, pl, sep, default_sep)
	local prefix = path.commonpath(s, pwd, pl)
	if not prefix then return nil end
	local type, p, drive = path.parse(s, pl)
	local win = win(pl)
	local sep = sep or detect_sep(pwd, win) or detect_sep(p, win)
		or default_sep or (win and '\\' or '/')
	local endsep = p:match(win and '[\\/]*$' or '/*$')
	local pwd_suffix = pwd:sub(#prefix + 1)
	local n = depth(pwd_suffix, win)
	local p1 = ('..' .. sep):rep(n - 1) .. (n > 0 and '..' or '')
	local p2 = p:sub(#prefix + 1)
	local p2 = p2:gsub(win and '^[\\/]+' or '^/+', '')
	local p2 = p2:gsub(win and '[\\/]+$' or '/+$', '')
	local p2 = p1 == '' and p2 == '' and '.' or p2
	local p3 = p1 .. (p1 ~= '' and p2 ~= '' and sep or '') .. p2 .. endsep
	return path.format(type, p3, drive, pl)
end

--validate/make-valid a filename
--NOTE: repl can be a function(match, err) -> repl_str.
--NOTE: if repl isn't itself escaped then duplicate filenames can result.
function path.filename(s, pl, repl, break_on_err)
	local win = win(pl)

	local function check(err, msg)
		if not repl or err == break_on_err then
			return nil, msg, err
		end
		local s = repl(s, err)
		if not s then
			return nil, msg, err
		end
		return path.filename(s, pl, repl, err) --tail call
	end

	function subcheck(patt, err, msg)
		if repl then
			local user_repl = repl
			function repl(s, err)
				local s, repl_count = s:gsub(patt, function(c)
					return user_repl(c, err) --returning nil/false means no repl.
				end)
				return repl_count > 0 and s
			end
		end
		return check(err, msg)
	end

	local invalid_chars = win and '[%z\1-\31<>:"|%?%*\\/]' or '[%z/]'
	local empty

	if s == '' then
		return check(s, 'empty filename')
	elseif s == '.' or s == '..' then
		return check(s, 'filename is `.` or `..`')
	elseif win and path.dev_alias(s) then
		return check('dev_alias', 'filename is a Windows device alias')
	elseif win and s:find(invalid_chars) then
		return subcheck(invalid_chars, 'char', 'invalid characters in filename')
	elseif #s > 255 then --same maximum for Windows and Linux
		return check('length', 'filename too long')
	elseif s:find' +$' then
		return subcheck(' +$', 'evil', 'filename ends with spaces')
	elseif s:find'^ +' then
		return subcheck('^ +', 'evil', 'filename begins with spaces')
	elseif s:find'%.+$' then
		return subcheck('%.+$', 'evil', 'filename ends with a dot')
	end
	return s
end

return path