local lexer = require 'lua_lang'

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local function get_assert_body_text (call_info)
	if call_info.what == 'Lua' then
		-- Find filetext
		local filetext = nil
		if call_info.source:find '^@' then
			local f = io.open(call_info.short_src, 'r')
			filetext = f:read '*all'
			f:close()
		elseif call_info.short_src:find '^%[string' then
			filetext = call_info.source
		else
			error 'Not implemented yet!'
		end
		-- Get lines
		local filetext = filetext .. '\n'
		local lines_after, line_i  =  {}, 0
		for line in filetext:gmatch '([^\r\n]*)[\r\n]' do
			line_i = line_i + 1
			if call_info.currentline == line_i then
				lines_after[#lines_after+1] = line
			end
		end
		-- Find body exclusively.
		return table.concat(lines_after, '\n'):match('assert%s*(%b())'):sub(2, -2)
	end

	error 'Not implemented yet!'
end

local function get_assert_body (call_info)
	local text = get_assert_body_text(call_info)
	return lexer:lex(text), text
end

local function get_variable (var_name, level)
	-- Local
	local index = 0
	repeat
		index = index + 1
		local name, val  =  debug.getlocal(level + 1, index)
		if name == var_name then
			local info   = debug.getinfo(level + 1)
			local is_par = index <= info.nparams
			return val, is_par and ('argument #'..index) or 'local', info.name or is_par and ''
		end
	until not name

	-- Up-value
	local index, func = 0, debug.getinfo(level + 1).func
	repeat
		index = index + 1
		local name, val  =  debug.getupvalue(func, index)
		if name == var_name then  return val, 'upvalue'  end
	until not name

	-- Global
	return getfenv(level + 1)[var_name], 'global'
end

local function get_value_of_string (string_str)
	if string_str:sub(1, 1) == '"' or string_str:sub(1, 1) == '\'' then
		return string_str:sub(2, -2)
	end
	assert(false)
end

--------------------------------------------------------------------------------

return function (condition)
	if condition then  return  condition  end
	local call_info = debug.getinfo(2)
	local tokens, body_text = get_assert_body(call_info)

	if tokens[1].text == 'type' and tokens[2].token == 'LPAR' and tokens[3].token == 'IDENTIFIER' and tokens[4].token == 'RPAR'and tokens[5].token == 'EQ'and tokens[6].token == 'STRING' then
		local var_name = tokens[3].text
		local var_val, var_scope, is_func  =  get_variable(var_name, 2)
		local func_name = (is_func == '' and ' to anonymous function') or is_func and (' to \''..is_func..'\'') or ''
		error(('assertion failed! bad %s \'%s\'%s (%s expected, but got %s: %s)'):format(var_scope, var_name, func_name, get_value_of_string(tokens[6].text), type(var_val), var_val), 2)
	else
		error(('assertion failed! expression `%s` evaluated to %s'):format(body_text, condition), 2)
	end
end