//
// Copyright (c) 2023 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#include "util/cookie.hpp"

#include <sstream>
#include <stdexcept>
#include <string_view>

#include "error.hpp"

using namespace chat;

// Copied from Boost.Beast. Returns whether a character is valid in the context
// of a HTTP token (RFC2616/RFC7230). Cookie names must be valid HTTP tokens.
static bool is_token_char(char c) noexcept
{
 /*
 tchar = "!" | "#" | "$" | "%" | "&" |
 "'" | "*" | "+" | "-" | "." |
 "^" | "_" | "`" | "|" | "~" |
 DIGIT | ALPHA
 */
 static char constexpr tab[] = {
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16
 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, // 32
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, // 48
 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 64
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, // 80
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 96
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, // 112
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 128
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 144
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 160
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 176
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 192
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 208
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 224
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 // 240
 };
 static_assert(sizeof(tab) == 256u);
 return tab[static_cast<unsigned char>(c)];
}

// Returns whether a character is valid in the context of a cookie value.
// See https://datatracker.ietf.org/doc/html/rfc6265#section-4.1.1
static bool is_cookie_value_char(char c) noexcept
{
 // cookie-octet = %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E
 // ; US-ASCII characters excluding CTLs,
 // ; whitespace DQUOTE, comma, semicolon,
 // ; and backslash
 static char constexpr tab[] = {
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16
 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, // 32
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, // 48
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 64
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, // 80
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 96
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, // 112
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 128
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 144
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 160
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 176
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 192
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 208
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 224
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 // 240
 };
 static_assert(sizeof(tab) == 256u);
 return tab[static_cast<unsigned char>(c)];
}

// Skips optional whitespace
static const char* skip_ows(const char* it, const char* end) noexcept
{
 while (it != end && (*it == ' ' || *it == '\t'))
 ++it;
 return it;
}

// Skips a token
static const char* skip_token(const char* it, const char* last) noexcept
{
 while (it != last && is_token_char(*it))
 ++it;
 return it;
}

// Skips a cookie value
static const char* skip_cookie_value(const char* it, const char* last) noexcept
{
 while (it != last && is_cookie_value_char(*it))
 ++it;
 return it;
}

static bool is_valid_token(std::string_view value) noexcept
{
 if (value.empty())
 return false;
 for (char c : value)
 {
 if (!is_token_char(c))
 return false;
 }
 return true;
}

static bool is_valid_cookie_value(std::string_view value) noexcept
{
 if (value.empty())
 return false;
 for (char c : value)
 {
 if (!is_cookie_value_char(c))
 return false;
 }
 return true;
}

static std::string_view trim_ows(std::string_view from) noexcept
{
 const char* first = from.data();
 const char* last = from.data() + from.size();
 first = skip_ows(first, last);
 return std::string_view(first, last - first);
}

set_cookie_builder::set_cookie_builder(std::string_view name, std::string_view value)
 : name_(name), value_(value)
{
 if (!is_valid_token(name_))
 throw std::invalid_argument("Invalid cookie name");
 if (!is_valid_cookie_value(value_))
 throw std::invalid_argument("Invalid cookie value");
}

std::string set_cookie_builder::build_header() const
{
 std::ostringstream oss;
 oss << name_ << '=' << value_;
 if (http_only_)
 oss << "; HttpOnly";
 if (max_age_)
 oss << "; Max-Age=" << max_age_->count();
 if (same_site_ != same_site_t::lax)
 oss << "; SameSite=" << (same_site_ == same_site_t::none ? "None" : "Strict");
 if (secure_)
 oss << "; Secure";
 return oss.str();
}

// Grammar for the Cookie header
// https://datatracker.ietf.org/doc/html/rfc6265
//
// cookie-header = "Cookie:" OWS cookie-string OWS
// cookie-string = cookie-pair *( ";" SP cookie-pair )
// cookie-pair = cookie-name "=" cookie-value
// cookie-name = token
// cookie-value = *cookie-octet / ( DQUOTE *cookie-octet DQUOTE )
// cookie-octet = %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E
// ; US-ASCII characters excluding CTLs,
// ; whitespace DQUOTE, comma, semicolon,
// ; and backslash

// Trim the initial OWS. The final OWS can be left there, since when no more cookies
// are found, increment() sets the iterator to end()
cookie_list::cookie_list(std::string_view header) noexcept : header_(trim_ows(header)) {}

void cookie_list::const_iterator::increment(bool is_first) noexcept
{
 // Check that this is not a sentinel iterator
 assert(next_ != nullptr);
 assert(last_ != nullptr);

 const char* current = next_;
 const char* const last = last_;

 // If we're parsing subsequent cookies, skip a semicolon and a space
 if (!is_first)
 {
 if (current == last || *current++ != ';')
 return reset();
 if (current == last || *current++ != ' ')
 return reset();
 }

 // Cookie name. Empty cookie names are not valid
 auto name_first = current;
 current = skip_token(current, last);
 std::string_view name(name_first, current - name_first);
 if (name.empty())
 return reset();

 // Equal sign
 if (current == last || *current++ != '=')
 return reset();

 // Cookie value. Note that quotes are part of the value
 auto value_first = current;
 bool is_quoted = false;
 if (current != last && *current == '"')
 {
 ++current;
 is_quoted = true;
 }
 current = skip_cookie_value(current, last);
 if (is_quoted)
 {
 if (current == last || *current != '"')
 return reset();
 ++current;
 }
 std::string_view value(value_first, current - value_first);

 // Done parsing
 val_.name = name;
 val_.value = value;
 next_ = current;
 last_ = last;
}