--[[
util.lua - Utility functions for the Lua sandbox
Enhanced with web development utilities
]]--

local util = {}

-- ======================================================================
-- CORE UTILITY FUNCTIONS
-- ======================================================================

-- Generate a random token
function util.generate_token(length)
	return __generate_token(length or 32)
end

-- Deep copy of tables
function util.deep_copy(obj)
	if type(obj) ~= 'table' then return obj end
	local res = {}
	for k, v in pairs(obj) do res[k] = util.deep_copy(v) end
	return res
end

-- Merge tables
function util.merge_tables(t1, t2)
	if type(t1) ~= 'table' or type(t2) ~= 'table' then
		error("Both arguments must be tables", 2)
	end

	local result = util.deep_copy(t1)
	for k, v in pairs(t2) do
		if type(v) == 'table' and type(result[k]) == 'table' then
			result[k] = util.merge_tables(result[k], v)
		else
			result[k] = v
		end
	end
	return result
end

-- ======================================================================
-- HTML ENTITY FUNCTIONS
-- ======================================================================

-- HTML entity mapping for common characters
local html_entities = {
	["&"] = "&",
	["<"] = "&lt;",
	[">"] = "&gt;",
	['"'] = "&quot;",
	["'"] = "&#39;",
	["/"] = "&#x2F;",
	["`"] = "&#x60;",
	["="] = "&#x3D;"
}

-- Convert special characters to HTML entities (like htmlspecialchars)
function util.html_special_chars(str)
	if type(str) ~= "string" then
		return str
	end
	
	return __html_special_chars(str)
end

-- Convert all applicable characters to HTML entities (like htmlentities)
function util.html_entities(str)
	if type(str) ~= "string" then
		return str
	end
	
	return __html_entities(str)
end

-- Convert HTML entities back to characters (simple version)
function util.html_entity_decode(str)
	if type(str) ~= "string" then
		return str
	end
	
	str = str:gsub("&lt;", "<")
	str = str:gsub("&gt;", ">")
	str = str:gsub("&quot;", '"')
	str = str:gsub("&#39;", "'")
	str = str:gsub("&amp;", "&")
	
	return str
end

-- Convert newlines to <br> tags
function util.nl2br(str)
	if type(str) ~= "string" then
		return str
	end
	
	return str:gsub("\r\n", "<br>"):gsub("\n", "<br>"):gsub("\r", "<br>")
end

-- ======================================================================
-- URL FUNCTIONS
-- ======================================================================

-- URL encode a string
function util.url_encode(str)
	if type(str) ~= "string" then
		return str
	end
	
	str = str:gsub("\n", "\r\n")
	str = str:gsub("([^%w %-%_%.%~])", function(c)
		return string.format("%%%02X", string.byte(c))
	end)
	str = str:gsub(" ", "+")
	return str
end

-- URL decode a string
function util.url_decode(str)
	if type(str) ~= "string" then
		return str
	end
	
	str = str:gsub("+", " ")
	str = str:gsub("%%(%x%x)", function(h)
		return string.char(tonumber(h, 16))
	end)
	return str
end

-- ======================================================================
-- VALIDATION FUNCTIONS
-- ======================================================================

-- Email validation
function util.is_email(str)
	if type(str) ~= "string" then
		return false
	end
	
	-- Simple email validation pattern
	local pattern = "^[%w%.%%%+%-]+@[%w%.%%%+%-]+%.%w%w%w?%w?$"
	return str:match(pattern) ~= nil
end

-- URL validation
function util.is_url(str)
	if type(str) ~= "string" then
		return false
	end
	
	-- Simple URL validation
	local pattern = "^https?://[%w-_%.%?%.:/%+=&%%]+$"
	return str:match(pattern) ~= nil
end

-- IP address validation (IPv4)
function util.is_ipv4(str)
	if type(str) ~= "string" then
		return false
	end
	
	local pattern = "^(%d%d?%d?)%.(%d%d?%d?)%.(%d%d?%d?)%.(%d%d?%d?)$"
	local a, b, c, d = str:match(pattern)
	
	if not (a and b and c and d) then
		return false
	end
	
	a, b, c, d = tonumber(a), tonumber(b), tonumber(c), tonumber(d)
	return a <= 255 and b <= 255 and c <= 255 and d <= 255
end

-- Integer validation
function util.is_int(str)
	if type(str) == "number" then
		return math.floor(str) == str
	elseif type(str) ~= "string" then
		return false
	end
	
	return str:match("^-?%d+$") ~= nil
end

-- Float validation
function util.is_float(str)
	if type(str) == "number" then
		return true
	elseif type(str) ~= "string" then
		return false
	end
	
	return str:match("^-?%d+%.?%d*$") ~= nil
end

-- Boolean validation
function util.is_bool(value)
	if type(value) == "boolean" then
		return true
	elseif type(value) ~= "string" and type(value) ~= "number" then
		return false
	end
	
	local v = type(value) == "string" and value:lower() or value
	return v == "1" or v == "true" or v == "on" or v == "yes" or
	       v == "0" or v == "false" or v == "off" or v == "no" or
	       v == 1 or v == 0
end

-- Convert to boolean
function util.to_bool(value)
	if type(value) == "boolean" then
		return value
	elseif type(value) ~= "string" and type(value) ~= "number" then
		return false
	end
	
	local v = type(value) == "string" and value:lower() or value
	return v == "1" or v == "true" or v == "on" or v == "yes" or v == 1
end

-- Sanitize string (simple version)
function util.sanitize_string(str)
	if type(str) ~= "string" then
		return ""
	end
	
	return util.html_special_chars(str)
end

-- Sanitize to integer
function util.sanitize_int(value)
	if type(value) ~= "string" and type(value) ~= "number" then
		return 0
	end
	
	value = tostring(value)
	local result = value:match("^-?%d+")
	return result and tonumber(result) or 0
end

-- Sanitize to float
function util.sanitize_float(value)
	if type(value) ~= "string" and type(value) ~= "number" then
		return 0
	end
	
	value = tostring(value)
	local result = value:match("^-?%d+%.?%d*")
	return result and tonumber(result) or 0
end

-- Sanitize URL
function util.sanitize_url(str)
	if type(str) ~= "string" then
		return ""
	end
	
	-- Basic sanitization by removing control characters
	str = str:gsub("[\000-\031]", "")
	
	-- Make sure it's a valid URL
	if util.is_url(str) then
		return str
	end
	
	-- Try to prepend http:// if it's missing
	if not str:match("^https?://") and util.is_url("http://" .. str) then
		return "http://" .. str
	end
	
	return ""
end

-- Sanitize email
function util.sanitize_email(str)
	if type(str) ~= "string" then
		return ""
	end
	
	-- Remove all characters except common email characters
	str = str:gsub("[^%a%d%!%#%$%%%&%'%*%+%-%/%=%?%^%_%`%{%|%}%~%@%.%[%]]", "")
	
	-- Return only if it's a valid email
	if util.is_email(str) then
		return str
	end
	
	return ""
end

-- ======================================================================
-- SECURITY FUNCTIONS
-- ======================================================================

-- Basic XSS prevention
function util.xss_clean(str)
	if type(str) ~= "string" then
		return str
	end
	
	-- Convert problematic characters to entities
	local result = util.html_special_chars(str)
	
	-- Remove JavaScript event handlers
	result = result:gsub("on%w+%s*=", "")
	
	-- Remove JavaScript protocol
	result = result:gsub("javascript:", "")
	
	-- Remove CSS expression
	result = result:gsub("expression%s*%(", "")
	
	return result
end

-- Base64 encode
function util.base64_encode(str)
	if type(str) ~= "string" then
		return str
	end
	
	return __base64_encode(str)
end

-- Base64 decode
function util.base64_decode(str)
	if type(str) ~= "string" then
		return str
	end
	
	return __base64_decode(str)
end

return util