// -*- mode: c++; c-basic-offset: 2; -*-

#include "common.hh"

#include <cstring>
#include <memory>
#include <sstream>
#include <vector>

#include "http.hh"

namespace {

std::string make_string(char const* data, size_t start, size_t end) {
  assert(start <= end);
  return std::string(data + start, end - start);
}

uint16_t number(char const* data, size_t start, size_t end) {
  uint16_t ret = 0;
  assert(start < end);
  for (; start < end; ++start) {
    ret *= 10;
    ret += data[start] - '0';
  }
  return ret;
}

inline char lower_ascii(char c) {
  return (c >= 'A' && c <= 'Z') ? (c - 'A' + 'a') : c;
}

inline char upper_ascii(char c) {
  return (c >= 'a' && c <= 'z') ? (c - 'a' + 'A') : c;
}

bool lower_equal(char const* data, size_t start, size_t end,
                 std::string const& str) {
  assert(start <= end);
  if (str.size() != end - start) return false;
  for (auto i = str.begin(); start < end; ++start, ++i) {
    if (lower_ascii(*i) != lower_ascii(data[start])) return false;
  }
  return true;
}

bool lower_equal2(char const* data, size_t start, size_t end,
                  char const* str, size_t size) {
  assert(start <= end);
  if (size != end - start) return false;
  for (auto i = str; start < end; ++start, ++i) {
    if (*i != lower_ascii(data[start])) return false;
  }
  return true;
}

bool allow_header_append(char const* data, size_t start, size_t end) {
  // These headers doesn't handle being merged with ',' even if the standard
  // say they must
  return !lower_equal2(data, start, end, "set-cookie", 10) &&
    !lower_equal2(data, start, end, "set-cookie2", 11);
}

enum ParseResult {
  GOOD,
  BAD,
  INCOMPLETE,
};

class HeaderIteratorImpl : public HeaderIterator {
public:
  HeaderIteratorImpl(char const* data, std::vector<size_t> const* headers)
    : data_(data), headers_(headers), iter_(headers_->begin()) {
  }

  bool valid() const override {
    return iter_ != headers_->end();
  }
  std::string name() const override {
    return make_string(data_, iter_[0], iter_[1]);
  }
  bool name_equal(std::string const& name) const override {
    return lower_equal(data_, iter_[0], iter_[1], name);
  }
  std::string value() const override {
    std::string ret = make_string(data_, iter_[2], iter_[3]);
    if (allow_header_append(data_, iter_[0], iter_[1])) {
      auto i = iter_ + 4;
      while (i != headers_->end()) {
        if (i[0] != i[1]) break;
        ret.push_back(',');
        ret.append(data_ + i[2], i[3] - i[2]);
        i += 4;
      }
    }
    return ret;
  }
  void next() override {
    if (iter_ != headers_->end()) {
      while (true) {
        iter_ += 4;
        if (iter_ == headers_->end() || iter_[0] != iter_[1]) break;
      }
    }
  }

private:
  char const* const data_;
  std::vector<size_t> const* const headers_;
  std::vector<size_t>::const_iterator iter_;
};

class FilterHeaderIteratorImpl : public HeaderIteratorImpl {
public:
  FilterHeaderIteratorImpl(char const* data, std::vector<size_t> const* headers,
                           std::string const& filter)
    : HeaderIteratorImpl(data, headers), filter_(filter) {
    check_filter();
  }

  void next() override {
    HeaderIteratorImpl::next();
    check_filter();
  }

private:
  void check_filter() {
    while (true) {
      if (!valid() || name_equal(filter_)) return;
      next();
    }
  }

  std::string const filter_;
};

class AbstractHttp : public virtual Http {
public:
  AbstractHttp(char const* data, size_t size)
    : data_(data), size_(size) {
  }

  std::string proto() const override {
    return make_string(data_, proto_start_, proto_slash_);
  }

  bool proto_equal(std::string const& proto) const override {
    return proto.compare(0, proto.size(),
        data_ + proto_start_, proto_slash_ - proto_start_) == 0;
  }

  Version proto_version() const override {
    Version ret;
    ret.major = number(data_, proto_slash_ + 1, proto_dot_);
    ret.minor = number(data_, proto_dot_ + 1, proto_end_);
    return ret;
  }

  std::unique_ptr<HeaderIterator> header() const override {
    return std::unique_ptr<HeaderIterator>(
        new HeaderIteratorImpl(data_, &headers_));
  }
  std::unique_ptr<HeaderIterator> header(
      std::string const& name) const override {
    return std::unique_ptr<HeaderIterator>(
        new FilterHeaderIteratorImpl(data_, &headers_, name));
  }

  size_t size() const override {
    return content_start_;
  }

protected:
  ParseResult parse_headers() {
    headers_.clear();
    while (true) {
      auto start = content_start_;
      auto end = find_newline(start, &content_start_);
      if (end == std::string::npos) return INCOMPLETE;
      if (end == start) {
        // The final newline can only be a alone '\r' if the one in front of
        // it is also '\r', otherwise we expect a missing '\n'
        if (data_[start - 1] == '\n' && data_[content_start_ - 1] == '\r') {
          return INCOMPLETE;
        }
        break;
      }
      if (is_lws(data_[start])) {
        if (headers_.empty()) return BAD;
        headers_.push_back(start);
        headers_.push_back(start);
        headers_.push_back(start + 1);
        headers_.push_back(end);
      } else {
        auto colon = find(start, ':', end);
        if (colon == std::string::npos) return BAD;
        auto value_start = skip_lws(colon + 1, end);
        while (colon > start && is_lws(data_[colon - 1])) --colon;
        headers_.push_back(start);
        headers_.push_back(colon);
        headers_.push_back(value_start);
        headers_.push_back(end);
      }
    }
    return GOOD;
  }

  void new_data(char const* data) {
    data_ = data;
  }

  char const* data() const {
    return data_;
  }

  size_t data_size() const {
    return size_;
  }

  size_t find(size_t start, char c, size_t end) const {
    assert(start <= end);
    for (; start < end; ++start) {
      if (data_[start] == c) return start;
    }
    return std::string::npos;
  }

  static bool is_lws(char c) {
    return c == ' ' || c == '\t';
  }

  size_t skip_lws(size_t start, size_t end) const {
    assert(start <= end);
    while (start < end && is_lws(data_[start])) ++start;
    return start;
  }

  size_t find_newline(size_t start, size_t* next) const {
    assert(start <= size_);
    for (; start < size_; ++start) {
      if (data_[start] == '\r') {
        if (start + 1 < size_ && data_[start + 1] == '\n') {
          if (next) *next = start + 2;
        } else {
          if (next) *next = start + 1;
        }
        return start;
      } else if (data_[start] == '\n') {
        if (next) *next = start + 1;
        return start;
      }
    }
    return std::string::npos;
  }

  size_t valid_number(size_t start, size_t end) const {
    assert(start <= end);
    if (start == end) return std::string::npos;
    if (data_[start] == '0') {
      return start + 1;
    }
    if (data_[start] < '0' || data_[start] > '9') return std::string::npos;
    for (++start; start < end; ++start) {
      if (data_[start] < '0' || data_[start] > '9') break;
    }
    return start;
  }

  char const* data_;
  size_t const size_;
  size_t proto_start_;
  size_t proto_slash_;
  size_t proto_dot_;
  size_t proto_end_;
  std::vector<size_t> headers_;
  size_t content_start_;
};

class AbstractHttpResponse : public HttpResponse, protected AbstractHttp {
public:
  AbstractHttpResponse(char const* data, size_t size)
    : AbstractHttp(data, size), good_(false) {
  }

  bool good() const override {
    return good_;
  }

  uint16_t status_code() const override {
    return number(data_, status_start_, status_end_);
  }

  std::string status_message() const override {
    return make_string(data_, status_msg_start_, status_msg_end_);
  }

  ParseResult parse() {
    good_ = false;
    status_msg_end_ = find_newline(0, &content_start_);
    if (status_msg_end_ == std::string::npos) return INCOMPLETE;
    proto_start_ = 0;
    proto_slash_ = find(0, '/', status_msg_end_);
    if (proto_slash_ == std::string::npos) return BAD;
    proto_dot_ = valid_number(proto_slash_ + 1, status_msg_end_);
    if (proto_dot_ == std::string::npos || data_[proto_dot_] != '.') {
      return BAD;
    }
    proto_end_ = valid_number(proto_dot_ + 1, status_msg_end_);
    if (proto_end_ == std::string::npos || !is_lws(data_[proto_end_])) {
      return BAD;
    }
    status_start_ = skip_lws(proto_end_ + 1, status_msg_end_);
    status_end_ = valid_number(status_start_, status_msg_end_);
    if (status_end_ == std::string::npos) return BAD;
    if (is_lws(data_[status_end_])) {
      status_msg_start_ = skip_lws(status_end_ + 1, status_msg_end_);
    } else {
      status_msg_start_ = status_end_;
      if (status_msg_start_ != status_msg_end_) return BAD;
    }

    auto ret = parse_headers();
    if (ret == GOOD) good_ = true;
    return ret;
  }

protected:
  bool good_;
  size_t status_start_;
  size_t status_end_;
  size_t status_msg_start_;
  size_t status_msg_end_;
};

class UniqueHttpResponse : public AbstractHttpResponse {
public:
  UniqueHttpResponse(char const* data, size_t size)
    : AbstractHttpResponse(data, size) {
  }

  void copy() {
    assert(!data_);
    auto tmp = new char[data_size()];
    memcpy(tmp, data(), data_size());
    new_data(tmp);
    data_.reset(tmp);
  }

private:
  std::unique_ptr<char[]> data_;
};

class SharedHttpResponse : public AbstractHttpResponse {
public:
  SharedHttpResponse(std::shared_ptr<char> data, size_t offset, size_t len)
    : AbstractHttpResponse(data.get() + offset, len), data_(data) {
  }

private:
  std::shared_ptr<char> data_;
};

class AbstractHttpRequest : public HttpRequest, protected AbstractHttp {
public:
  AbstractHttpRequest(char const* data, size_t size)
    : AbstractHttp(data, size), good_(false) {
  }

  bool good() const override {
    return good_;
  }

  std::string method() const override {
    return make_string(data_, 0, method_end_);
  }

  bool method_equal(std::string const& method) const override {
    return method.compare(0, method.size(), data_, method_end_) == 0;
  }
  std::string url() const override {
    return make_string(data_, url_start_, url_end_);
  }

  ParseResult parse() {
    good_ = false;
    proto_end_ = find_newline(0, &content_start_);
    if (proto_end_ == std::string::npos) return INCOMPLETE;
    method_end_ = 0;
    while (method_end_ < proto_end_ && !is_lws(data_[method_end_])) {
      ++method_end_;
    }
    if (method_end_ == 0 || method_end_ == proto_end_) return BAD;
    url_start_ = skip_lws(method_end_ + 1, proto_end_);
    url_end_ = url_start_;
    while (url_end_ < proto_end_ && !is_lws(data_[url_end_])) {
      ++url_end_;
    }
    if (url_end_ == url_start_ || url_end_ == proto_end_) return BAD;
    proto_start_ = skip_lws(url_end_ + 1, proto_end_);
    proto_slash_ = find(proto_start_, '/', proto_end_);
    if (proto_slash_ == std::string::npos) return BAD;
    proto_dot_ = valid_number(proto_slash_ + 1, proto_end_);
    if (proto_dot_ == std::string::npos || data_[proto_dot_] != '.') {
      return BAD;
    }
    auto tmp = valid_number(proto_dot_ + 1, proto_end_);
    if (tmp != proto_end_) return BAD;

    auto ret = parse_headers();
    if (ret == GOOD) good_ = true;
    return ret;
  }

protected:
  bool good_;
  size_t method_end_;
  size_t url_start_;
  size_t url_end_;
};

class UniqueHttpRequest : public AbstractHttpRequest {
public:
  UniqueHttpRequest(char const* data, size_t size)
    : AbstractHttpRequest(data, size) {
  }

  void copy() {
    assert(!data_);
    auto tmp = new char[data_size()];
    memcpy(tmp, data(), data_size());
    new_data(tmp);
    data_.reset(tmp);
  }

private:
  std::unique_ptr<char[]> data_;
};

class SharedHttpRequest : public AbstractHttpRequest {
public:
  SharedHttpRequest(std::shared_ptr<char> data, size_t offset, size_t len)
    : AbstractHttpRequest(data.get() + offset, len), data_(data) {
  }

private:
  std::shared_ptr<char> data_;
};

class AbstractHttpBuilder {
public:
  AbstractHttpBuilder()
    : set_content_length_(false), set_content_(false) {
  }

  void add_header(std::string const& name,
                  std::string const& value) {
    if (name.empty()) {
      data_.push_back(' ');
      data_.append(value);
      data_.append("\r\n", 2);
      return;
    }
    size_t pos = 0;
    auto c = upper_ascii(name[pos]);
    if (c != name[pos]) {
      data_.push_back(c);
      ++pos;
    }
    auto last = pos;
    for (; pos < name.size(); ++pos) {
      if (name[pos] == '-') {
        ++pos;
        if (pos == name.size()) break;
        data_.append(name.data() + last, pos - last);
        auto c = upper_ascii(name[pos]);
        if (c != name[pos]) {
          data_.push_back(c);
          ++pos;
        }
        last = pos;
      }
    }
    if (!set_content_length_
        && lower_equal2(name.data(), 0, name.size(), "content-length", 14)) {
      set_content_length_ = true;
    }
    if (last < pos) {
      data_.append(name.data() + last, pos - last);
    }
    data_.append(": ", 2);
    data_.append(value);
    data_.append("\r\n", 2);
  }

  void set_content(std::string const& content) {
    set_content_ = true;
    content_ = content;
  }

  std::string build() const {
    std::string ret(data_);
    if (!set_content_length_ && set_content_) {
      char tmp[50];
      auto len = snprintf(tmp, sizeof(tmp),
                          "Content-Length: %zu\r\n", content_.size());
      ret.append(tmp, len);
    }
    ret.append("\r\n", 2);
    if (set_content_) {
      ret.append(content_);
    }
    return ret;
  }

protected:
  std::string data_;
  std::string content_;
  bool set_content_length_;
  bool set_content_;
};

class HttpRequestBuilderImpl : public HttpRequestBuilder, AbstractHttpBuilder {
public:
  HttpRequestBuilderImpl(std::string const& method, std::string const& url,
                         std::string const& proto, Version version) {
    data_.append(method);
    data_.push_back(' ');
    data_.append(url);
    data_.push_back(' ');
    data_.append(proto);
    data_.push_back('/');
    char tmp[10];
    data_.append(tmp, snprintf(
                     tmp, 10, "%u", static_cast<unsigned int>(version.major)));
    data_.push_back('.');
    data_.append(tmp, snprintf(
                     tmp, 10, "%u", static_cast<unsigned int>(version.minor)));
    data_.append("\r\n", 2);
  }

  void add_header(std::string const& name,
                  std::string const& value) override {
    AbstractHttpBuilder::add_header(name, value);
  }
  void set_content(std::string const& content) override {
    AbstractHttpBuilder::set_content(content);
  }
  std::string build() const override {
    return AbstractHttpBuilder::build();
  }
};

class HttpResponseBuilderImpl : public HttpResponseBuilder,
                                AbstractHttpBuilder {
public:
  HttpResponseBuilderImpl(std::string const& proto, Version version,
                          uint16_t status_code, std::string const& status) {
    data_.append(proto);
    data_.push_back('/');
    char tmp[10];
    data_.append(tmp, snprintf(
                     tmp, 10, "%u", static_cast<unsigned int>(version.major)));
    data_.push_back('.');
    data_.append(tmp, snprintf(
                     tmp, 10, "%u", static_cast<unsigned int>(version.minor)));
    data_.push_back(' ');
    data_.append(tmp, snprintf(
                     tmp, 10, "%u", static_cast<unsigned int>(status_code)));
    data_.push_back(' ');
    data_.append(status);
    data_.append("\r\n", 2);
  }

  void add_header(std::string const& name,
                  std::string const& value) override {
    AbstractHttpBuilder::add_header(name, value);
  }
  void set_content(std::string const& content) override {
    AbstractHttpBuilder::set_content(content);
  }
  std::string build() const override {
    return AbstractHttpBuilder::build();
  }
};

}  // namespace

// static
HttpResponse* HttpResponse::parse(std::string const& data) {
  return parse(data.data(), data.size(), true);
}

// static
HttpResponse* HttpResponse::parse(char const* data, size_t len, bool copy) {
  auto ret = std::unique_ptr<UniqueHttpResponse>(
      new UniqueHttpResponse(data, len));
  if (ret->parse() == INCOMPLETE) return nullptr;
  if (copy) ret->copy();
  return ret.release();
}

// static
HttpResponse* HttpResponse::parse(std::shared_ptr<char> data,
                                  size_t offset, size_t len) {
  auto ret = std::unique_ptr<SharedHttpResponse>(
      new SharedHttpResponse(data, offset, len));
  if (ret->parse() == INCOMPLETE) return nullptr;
  return ret.release();
}

std::string Http::first_header(std::string const& name) const {
  static std::string empty_str;
  auto iter = header(name);
  if (iter->valid()) {
    return iter->value();
  }
  return empty_str;
}

// static
HttpRequest* HttpRequest::parse(std::string const& data) {
  return parse(data.data(), data.size(), true);
}

// static
HttpRequest* HttpRequest::parse(char const* data, size_t len, bool copy) {
  auto ret = std::unique_ptr<UniqueHttpRequest>(
      new UniqueHttpRequest(data, len));
  if (ret->parse() == INCOMPLETE) return nullptr;
  if (copy) ret->copy();
  return ret.release();
}

// static
HttpRequest* HttpRequest::parse(std::shared_ptr<char> data,
                                size_t offset, size_t len) {
  auto ret = std::unique_ptr<SharedHttpRequest>(
      new SharedHttpRequest(data, offset, len));
  if (ret->parse() == INCOMPLETE) return nullptr;
  return ret.release();
}

// static
HttpRequestBuilder* HttpRequestBuilder::create(std::string const& method,
                                               std::string const& url,
                                               std::string const& proto,
                                               Version version) {
  return new HttpRequestBuilderImpl(method, url, proto, version);
}

// static
HttpResponseBuilder* HttpResponseBuilder::create(std::string const& proto,
                                                 Version version,
                                                 uint16_t status_code,
                                                 std::string const& status) {
  return new HttpResponseBuilderImpl(proto, version, status_code, status);
}