#include "source/common/config/xds_resource.h"

#include <algorithm>

#include "source/common/common/fmt.h"

#include "source/common/http/utility.h"

#include "absl/strings/str_cat.h"

#include "absl/strings/str_split.h"

// TODO(htuch): This file has a bunch of ad hoc URI encoding/decoding based on Envoy's HTTP util

// functions. Once https://github.com/envoyproxy/envoy/issues/6588 lands, we can replace with GURL.

namespace Envoy {

namespace Config {

using PercentEncoding = Http::Utility::PercentEncoding;

namespace {

// We need to percent-encode authority, id, path and query params. Resource types should not have

// reserved characters.

std::string encodeAuthority(const std::string& authority) {

  return PercentEncoding::encode(authority, "%/?#");

}

std::string encodeIdPath(const std::string& id) {

  const std::string path = PercentEncoding::encode(id, "%:?#[]");

  return path.empty() ? "" : absl::StrCat("/", path);

}

std::string encodeContextParams(const xds::core::v3::ContextParams& context_params,

                                bool sort_context_params) {

  std::vector<std::string> query_param_components;

  for (const auto& context_param : context_params.params()) {

    query_param_components.emplace_back(

        absl::StrCat(PercentEncoding::encode(context_param.first, "%#[]&="), "=",

                     PercentEncoding::encode(context_param.second, "%#[]&=")));

  }

  if (sort_context_params) {

    std::sort(query_param_components.begin(), query_param_components.end());

  }

  return query_param_components.empty() ? "" : "?" + absl::StrJoin(query_param_components, "&");

}

std::string encodeDirectives(

    const Protobuf::RepeatedPtrField<xds::core::v3::ResourceLocator::Directive>& directives) {

  std::vector<std::string> fragment_components;

  const std::string DirectiveEscapeChars = "%#[],";

  for (const auto& directive : directives) {

    switch (directive.directive_case()) {

    case xds::core::v3::ResourceLocator::Directive::DirectiveCase::kAlt:

      fragment_components.emplace_back(absl::StrCat(

          "alt=", PercentEncoding::encode(XdsResourceIdentifier::encodeUrl(directive.alt()),

                                          DirectiveEscapeChars)));

      break;

    case xds::core::v3::ResourceLocator::Directive::DirectiveCase::kEntry:

      fragment_components.emplace_back(

          absl::StrCat("entry=", PercentEncoding::encode(directive.entry(), DirectiveEscapeChars)));

      break;

    case xds::core::v3::ResourceLocator::Directive::DirectiveCase::DIRECTIVE_NOT_SET:

      PANIC_DUE_TO_PROTO_UNSET;

    }

  }

  return fragment_components.empty() ? "" : "#" + absl::StrJoin(fragment_components, ",");

}

} // namespace

std::string XdsResourceIdentifier::encodeUrn(const xds::core::v3::ResourceName& resource_name,

                                             const EncodeOptions& options) {

  const std::string authority = encodeAuthority(resource_name.authority());

  const std::string id_path = encodeIdPath(resource_name.id());

  const std::string query_params =

      encodeContextParams(resource_name.context(), options.sort_context_params_);

  return absl::StrCat("xdstp://", authority, "/", resource_name.resource_type(), id_path,

                      query_params);

}

std::string XdsResourceIdentifier::encodeUrl(const xds::core::v3::ResourceLocator& resource_locator,

                                             const EncodeOptions& options) {

  const std::string id_path = encodeIdPath(resource_locator.id());

  const std::string fragment = encodeDirectives(resource_locator.directives());

  std::string scheme = "xdstp:";

  switch (resource_locator.scheme()) {

    PANIC_ON_PROTO_ENUM_SENTINEL_VALUES;

  case xds::core::v3::ResourceLocator::HTTP:

    scheme = "http:";

    FALLTHRU;

  case xds::core::v3::ResourceLocator::XDSTP: {

    const std::string authority = encodeAuthority(resource_locator.authority());

    const std::string query_params =

        encodeContextParams(resource_locator.exact_context(), options.sort_context_params_);

    return absl::StrCat(scheme, "//", authority, "/", resource_locator.resource_type(), id_path,

                        query_params, fragment);

  }

  case xds::core::v3::ResourceLocator::FILE: {

    return absl::StrCat("file://", id_path, fragment);

  }

  }

  return "";

}

namespace {

void throwDecodeExceptionOrPanic(std::string message) {

  throwExceptionOrPanic(XdsResourceIdentifier::DecodeException, message);

}

void decodePath(absl::string_view path, std::string* resource_type, std::string& id) {

  // This is guaranteed by Http::Utility::extractHostPathFromUrn.

  ASSERT(absl::StartsWith(path, "/"));

  const std::vector<absl::string_view> path_components = absl::StrSplit(path.substr(1), '/');

  auto id_it = path_components.cbegin();

  if (resource_type != nullptr) {

    *resource_type = std::string(path_components[0]);

    if (resource_type->empty()) {

      throwDecodeExceptionOrPanic(fmt::format("Resource type missing from {}", path));

    }

    id_it = std::next(id_it);

  }

  id = PercentEncoding::decode(absl::StrJoin(id_it, path_components.cend(), "/"));

}

void decodeQueryParams(absl::string_view query_params,

                       xds::core::v3::ContextParams& context_params) {

  auto query_params_components = Http::Utility::QueryParamsMulti::parseQueryString(query_params);

  for (const auto& it : query_params_components.data()) {

    (*context_params.mutable_params())[PercentEncoding::decode(it.first)] =

        PercentEncoding::decode(it.second[0]);

  }

}

void decodeFragment(

    absl::string_view fragment,

    Protobuf::RepeatedPtrField<xds::core::v3::ResourceLocator::Directive>& directives) {

  const std::vector<absl::string_view> fragment_components = absl::StrSplit(fragment, ',');

  for (const absl::string_view& fragment_component : fragment_components) {

    if (absl::StartsWith(fragment_component, "alt=")) {

      directives.Add()->mutable_alt()->MergeFrom(

          XdsResourceIdentifier::decodeUrl(PercentEncoding::decode(fragment_component.substr(4))));

    } else if (absl::StartsWith(fragment_component, "entry=")) {

      directives.Add()->set_entry(PercentEncoding::decode(fragment_component.substr(6)));

    } else {

      throwDecodeExceptionOrPanic(fmt::format("Unknown fragment component {}", fragment_component));

      ;

    }

  }

}

} // namespace

xds::core::v3::ResourceName XdsResourceIdentifier::decodeUrn(absl::string_view resource_urn) {

  if (!hasXdsTpScheme(resource_urn)) {

    throwDecodeExceptionOrPanic(fmt::format("{} does not have an xdstp: scheme", resource_urn));

  }

  absl::string_view host, path;

  Http::Utility::extractHostPathFromUri(resource_urn, host, path);

  xds::core::v3::ResourceName decoded_resource_name;

  decoded_resource_name.set_authority(PercentEncoding::decode(host));

  const size_t query_params_start = path.find('?');

  if (query_params_start != absl::string_view::npos) {

    decodeQueryParams(path.substr(query_params_start), *decoded_resource_name.mutable_context());

    path = path.substr(0, query_params_start);

  }

  decodePath(path, decoded_resource_name.mutable_resource_type(),

             *decoded_resource_name.mutable_id());

  return decoded_resource_name;

}

xds::core::v3::ResourceLocator XdsResourceIdentifier::decodeUrl(absl::string_view resource_url) {

  absl::string_view host, path;

  Http::Utility::extractHostPathFromUri(resource_url, host, path);

  xds::core::v3::ResourceLocator decoded_resource_locator;

  const size_t fragment_start = path.find('#');

  if (fragment_start != absl::string_view::npos) {

    decodeFragment(path.substr(fragment_start + 1), *decoded_resource_locator.mutable_directives());

    path = path.substr(0, fragment_start);

  }

  if (hasXdsTpScheme(resource_url)) {

    decoded_resource_locator.set_scheme(xds::core::v3::ResourceLocator::XDSTP);

  } else if (absl::StartsWith(resource_url, "http:")) {

    decoded_resource_locator.set_scheme(xds::core::v3::ResourceLocator::HTTP);

  } else if (absl::StartsWith(resource_url, "file:")) {

    decoded_resource_locator.set_scheme(xds::core::v3::ResourceLocator::FILE);

    // File URLs only have a path and fragment.

    decodePath(path, nullptr, *decoded_resource_locator.mutable_id());

    return decoded_resource_locator;

  } else {

    throwExceptionOrPanic(

        XdsResourceIdentifier::DecodeException,

        fmt::format("{} does not have a xdstp:, http: or file: scheme", resource_url));

  }

  decoded_resource_locator.set_authority(PercentEncoding::decode(host));

  const size_t query_params_start = path.find('?');

  if (query_params_start != absl::string_view::npos) {

    decodeQueryParams(path.substr(query_params_start),

                      *decoded_resource_locator.mutable_exact_context());

    path = path.substr(0, query_params_start);

  }

  decodePath(path, decoded_resource_locator.mutable_resource_type(),

             *decoded_resource_locator.mutable_id());

  return decoded_resource_locator;

}

bool XdsResourceIdentifier::hasXdsTpScheme(absl::string_view resource_name) {

  return absl::StartsWith(resource_name, "xdstp:");

}

} // namespace Config

} // namespace Envoy