// Copyright Epic Games, Inc. All Rights Reserved.

#include <zenhttp/httpserver.h>

#include "servers/httpasio.h"
#include "servers/httpmulti.h"
#include "servers/httpnull.h"
#include "servers/httpsys.h"
#include "zenhttp/httpplugin.h"

#if ZEN_WITH_PLUGINS
#	include "transports/asiotransport.h"
#	include "transports/dlltransport.h"
#	include "transports/winsocktransport.h"
#endif

#include <zenbase/refcount.h>
#include <zencore/compactbinary.h>
#include <zencore/compactbinarybuilder.h>
#include <zencore/compactbinarypackage.h>
#include <zencore/compactbinaryutil.h>
#include <zencore/iobuffer.h>
#include <zencore/logging.h>
#include <zencore/stream.h>
#include <zencore/string.h>
#include <zencore/testing.h>
#include <zencore/thread.h>
#include <zenhttp/packageformat.h>
#include <zentelemetry/otlptrace.h>

#include <charconv>
#include <mutex>
#include <span>
#include <string_view>

#include <EASTL/fixed_vector.h>

namespace zen {

using namespace std::literals;

std::string_view
MapContentTypeToString(HttpContentType ContentType)
{
	switch (ContentType)
	{
		default:
		case HttpContentType::kUnknownContentType:
		case HttpContentType::kBinary:
			return "application/octet-stream"sv;

		case HttpContentType::kText:
			return "text/plain"sv;

		case HttpContentType::kJSON:
			return "application/json"sv;

		case HttpContentType::kCbObject:
			return "application/x-ue-cb"sv;

		case HttpContentType::kCbPackage:
			return "application/x-ue-cbpkg"sv;

		case HttpContentType::kCbPackageOffer:
			return "application/x-ue-offer"sv;

		case HttpContentType::kCompressedBinary:
			return "application/x-ue-comp"sv;

		case HttpContentType::kYAML:
			return "text/yaml"sv;

		case HttpContentType::kHTML:
			return "text/html"sv;

		case HttpContentType::kJavaScript:
			return "application/javascript"sv;

		case HttpContentType::kCSS:
			return "text/css"sv;

		case HttpContentType::kPNG:
			return "image/png"sv;

		case HttpContentType::kIcon:
			return "image/x-icon"sv;

		case HttpContentType::kXML:
			return "application/xml"sv;

		case HttpContentType::kProtobuf:
			return "application/x-protobuf"sv;
	}
}

//////////////////////////////////////////////////////////////////////////
//
// Note that in addition to MIME types we accept abbreviated versions, for
// use in suffix parsing as well as for convenience when using curl

static constinit uint32_t HashBinary					= HashStringDjb2("application/octet-stream"sv);
static constinit uint32_t HashJson						= HashStringDjb2("json"sv);
static constinit uint32_t HashApplicationJson			= HashStringDjb2("application/json"sv);
static constinit uint32_t HashApplicationProblemJson	= HashStringDjb2("application/problem+json"sv);
static constinit uint32_t HashYaml						= HashStringDjb2("yaml"sv);
static constinit uint32_t HashTextYaml					= HashStringDjb2("text/yaml"sv);
static constinit uint32_t HashText						= HashStringDjb2("text/plain"sv);
static constinit uint32_t HashApplicationCompactBinary	= HashStringDjb2("application/x-ue-cb"sv);
static constinit uint32_t HashCompactBinary				= HashStringDjb2("ucb"sv);
static constinit uint32_t HashCompactBinaryPackage		= HashStringDjb2("application/x-ue-cbpkg"sv);
static constinit uint32_t HashCompactBinaryPackageShort = HashStringDjb2("cbpkg"sv);
static constinit uint32_t HashCompactBinaryPackageOffer = HashStringDjb2("application/x-ue-offer"sv);
static constinit uint32_t HashCompressedBinary			= HashStringDjb2("application/x-ue-comp"sv);
static constinit uint32_t HashHtml						= HashStringDjb2("html"sv);
static constinit uint32_t HashTextHtml					= HashStringDjb2("text/html"sv);
static constinit uint32_t HashJavaScript				= HashStringDjb2("js"sv);
static constinit uint32_t HashJavaScriptSourceMap		= HashStringDjb2("map"sv);	// actually .js.map
static constinit uint32_t HashApplicationJavaScript		= HashStringDjb2("application/javascript"sv);
static constinit uint32_t HashCss						= HashStringDjb2("css"sv);
static constinit uint32_t HashTextCss					= HashStringDjb2("text/css"sv);
static constinit uint32_t HashPng						= HashStringDjb2("png"sv);
static constinit uint32_t HashImagePng					= HashStringDjb2("image/png"sv);
static constinit uint32_t HashIcon						= HashStringDjb2("ico"sv);
static constinit uint32_t HashImageIcon					= HashStringDjb2("image/x-icon"sv);
static constinit uint32_t HashXml						= HashStringDjb2("application/xml"sv);
static constinit uint32_t HashProtobuf					= HashStringDjb2("application/x-protobuf"sv);

std::once_flag InitContentTypeLookup;

struct HashedTypeEntry
{
	uint32_t		Hash;
	HttpContentType Type;
} TypeHashTable[] = {
	// clang-format off
	{HashBinary,					HttpContentType::kBinary},
	{HashApplicationCompactBinary,	HttpContentType::kCbObject},
	{HashCompactBinary,				HttpContentType::kCbObject},
	{HashCompactBinaryPackage,		HttpContentType::kCbPackage},
	{HashCompactBinaryPackageShort,	HttpContentType::kCbPackage},
	{HashCompactBinaryPackageOffer, HttpContentType::kCbPackageOffer},
	{HashJson,						HttpContentType::kJSON},
	{HashApplicationJson,			HttpContentType::kJSON},
	{HashApplicationProblemJson,	HttpContentType::kJSON},
	{HashYaml,						HttpContentType::kYAML},
	{HashTextYaml,					HttpContentType::kYAML},
	{HashText,						HttpContentType::kText},
	{HashCompressedBinary,			HttpContentType::kCompressedBinary},
	{HashHtml,						HttpContentType::kHTML},
	{HashTextHtml,					HttpContentType::kHTML},
	{HashJavaScript,				HttpContentType::kJavaScript},
	{HashApplicationJavaScript,		HttpContentType::kJavaScript},
	{HashJavaScriptSourceMap,		HttpContentType::kJavaScript},
	{HashCss,						HttpContentType::kCSS},
	{HashTextCss,					HttpContentType::kCSS},
	{HashPng,						HttpContentType::kPNG},
	{HashImagePng,					HttpContentType::kPNG},
	{HashIcon,						HttpContentType::kIcon},
	{HashImageIcon,					HttpContentType::kIcon},
	{HashXml,						HttpContentType::kXML},
	{HashProtobuf,					HttpContentType::kProtobuf},
	// clang-format on
};

HttpContentType
ParseContentTypeImpl(const std::string_view& ContentTypeString)
{
	if (!ContentTypeString.empty())
	{
		size_t ContentEnd = ContentTypeString.find(';');
		if (ContentEnd == std::string_view::npos)
		{
			ContentEnd = ContentTypeString.length();
		}
		std::string_view ContentString(ContentTypeString.substr(0, ContentEnd));

		const uint32_t CtHash = HashStringDjb2(ContentString);

		if (auto It = std::lower_bound(std::begin(TypeHashTable),
									   std::end(TypeHashTable),
									   CtHash,
									   [](const HashedTypeEntry& Lhs, const uint32_t Rhs) { return Lhs.Hash < Rhs; });
			It != std::end(TypeHashTable))
		{
			if (It->Hash == CtHash)
			{
				return It->Type;
			}
		}
	}

	return HttpContentType::kUnknownContentType;
}

HttpContentType
ParseContentTypeInit(const std::string_view& ContentTypeString)
{
	std::call_once(InitContentTypeLookup, [] {
		std::sort(std::begin(TypeHashTable), std::end(TypeHashTable), [](const HashedTypeEntry& Lhs, const HashedTypeEntry& Rhs) {
			return Lhs.Hash < Rhs.Hash;
		});

		// validate that there are no hash collisions

		uint32_t LastHash = 0;

		for (const auto& Item : TypeHashTable)
		{
			ZEN_ASSERT(LastHash != Item.Hash);
			LastHash = Item.Hash;
		}
	});

	ParseContentType = ParseContentTypeImpl;

	return ParseContentTypeImpl(ContentTypeString);
}

HttpContentType (*ParseContentType)(const std::string_view& ContentTypeString) = &ParseContentTypeInit;

bool
TryParseHttpRangeHeader(std::string_view RangeHeader, HttpRanges& Ranges)
{
	if (RangeHeader.empty())
	{
		return false;
	}

	const size_t Count = Ranges.size();

	std::size_t UnitDelim = RangeHeader.find_first_of('=');
	if (UnitDelim == std::string_view::npos)
	{
		return false;
	}

	// only bytes for now
	std::string_view Unit = RangeHeader.substr(0, UnitDelim);
	if (Unit != "bytes"sv)
	{
		return false;
	}

	std::string_view Tokens = RangeHeader.substr(UnitDelim);
	while (!Tokens.empty())
	{
		// Skip =,
		Tokens = Tokens.substr(1);

		size_t Delim = Tokens.find_first_of(',');
		if (Delim == std::string_view::npos)
		{
			Delim = Tokens.length();
		}

		std::string_view Token = Tokens.substr(0, Delim);
		Tokens				   = Tokens.substr(Delim);

		Delim = Token.find_first_of('-');
		if (Delim == std::string_view::npos)
		{
			return false;
		}

		const auto Start = ParseInt<uint32_t>(Token.substr(0, Delim));
		const auto End	 = ParseInt<uint32_t>(Token.substr(Delim + 1));

		if (Start.has_value() && End.has_value() && End.value() > Start.value())
		{
			Ranges.push_back({.Start = Start.value(), .End = End.value()});
		}
		else if (Start)
		{
			Ranges.push_back({.Start = Start.value()});
		}
		else if (End)
		{
			Ranges.push_back({.End = End.value()});
		}
	}

	return Count != Ranges.size();
}

//////////////////////////////////////////////////////////////////////////

const std::string_view
ToString(HttpVerb Verb)
{
	switch (Verb)
	{
		case HttpVerb::kGet:
			return "GET"sv;
		case HttpVerb::kPut:
			return "PUT"sv;
		case HttpVerb::kPost:
			return "POST"sv;
		case HttpVerb::kDelete:
			return "DELETE"sv;
		case HttpVerb::kHead:
			return "HEAD"sv;
		case HttpVerb::kCopy:
			return "COPY"sv;
		case HttpVerb::kOptions:
			return "OPTIONS"sv;
		default:
			return "???"sv;
	}
}

std::string_view
ToString(HttpResponseCode HttpCode)
{
	return ReasonStringForHttpResultCode(int(HttpCode));
}

std::string_view
ReasonStringForHttpResultCode(int HttpCode)
{
	switch (HttpCode)
	{
			// 1xx Informational

		case 100:
			return "Continue"sv;
		case 101:
			return "Switching Protocols"sv;

			// 2xx Success

		case 200:
			return "OK"sv;
		case 201:
			return "Created"sv;
		case 202:
			return "Accepted"sv;
		case 204:
			return "No Content"sv;
		case 205:
			return "Reset Content"sv;
		case 206:
			return "Partial Content"sv;

			// 3xx Redirection

		case 300:
			return "Multiple Choices"sv;
		case 301:
			return "Moved Permanently"sv;
		case 302:
			return "Found"sv;
		case 303:
			return "See Other"sv;
		case 304:
			return "Not Modified"sv;
		case 305:
			return "Use Proxy"sv;
		case 306:
			return "Switch Proxy"sv;
		case 307:
			return "Temporary Redirect"sv;
		case 308:
			return "Permanent Redirect"sv;

			// 4xx Client errors

		case 400:
			return "Bad Request"sv;
		case 401:
			return "Unauthorized"sv;
		case 402:
			return "Payment Required"sv;
		case 403:
			return "Forbidden"sv;
		case 404:
			return "Not Found"sv;
		case 405:
			return "Method Not Allowed"sv;
		case 406:
			return "Not Acceptable"sv;
		case 407:
			return "Proxy Authentication Required"sv;
		case 408:
			return "Request Timeout"sv;
		case 409:
			return "Conflict"sv;
		case 410:
			return "Gone"sv;
		case 411:
			return "Length Required"sv;
		case 412:
			return "Precondition Failed"sv;
		case 413:
			return "Payload Too Large"sv;
		case 414:
			return "URI Too Long"sv;
		case 415:
			return "Unsupported Media Type"sv;
		case 416:
			return "Range Not Satisifiable"sv;
		case 417:
			return "Expectation Failed"sv;
		case 418:
			return "I'm a teapot"sv;
		case 421:
			return "Misdirected Request"sv;
		case 422:
			return "Unprocessable Entity"sv;
		case 423:
			return "Locked"sv;
		case 424:
			return "Failed Dependency"sv;
		case 425:
			return "Too Early"sv;
		case 426:
			return "Upgrade Required"sv;
		case 428:
			return "Precondition Required"sv;
		case 429:
			return "Too Many Requests"sv;
		case 431:
			return "Request Header Fields Too Large"sv;

			// 5xx Server errors

		case 500:
			return "Internal Server Error"sv;
		case 501:
			return "Not Implemented"sv;
		case 502:
			return "Bad Gateway"sv;
		case 503:
			return "Service Unavailable"sv;
		case 504:
			return "Gateway Timeout"sv;
		case 505:
			return "HTTP Version Not Supported"sv;
		case 506:
			return "Variant Also Negotiates"sv;
		case 507:
			return "Insufficient Storage"sv;
		case 508:
			return "Loop Detected"sv;
		case 510:
			return "Not Extended"sv;
		case 511:
			return "Network Authentication Required"sv;

		default:
			return "Unknown Result"sv;
	}
}

//////////////////////////////////////////////////////////////////////////

Ref<IHttpPackageHandler>
HttpService::HandlePackageRequest(HttpServerRequest& HttpServiceRequest)
{
	ZEN_UNUSED(HttpServiceRequest);

	return Ref<IHttpPackageHandler>();
}

//////////////////////////////////////////////////////////////////////////

HttpServerRequest::HttpServerRequest(HttpService& Service) : m_Service(Service)
{
}

HttpServerRequest::~HttpServerRequest()
{
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, CbPackage Data)
{
	std::vector<IoBuffer> ResponseBuffers = FormatPackageMessage(Data);
	return WriteResponse(ResponseCode, HttpContentType::kCbPackage, ResponseBuffers);
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, CbObject Data)
{
	if (m_AcceptType == HttpContentType::kJSON)
	{
		ExtendableStringBuilder<1024> Sb;
		WriteResponse(ResponseCode, HttpContentType::kJSON, Data.ToJson(Sb).ToView());
	}
	else if (m_AcceptType == HttpContentType::kYAML)
	{
		ExtendableStringBuilder<1024> Sb;
		WriteResponse(ResponseCode, HttpContentType::kYAML, Data.ToYaml(Sb).ToView());
	}
	else
	{
		SharedBuffer			Buf = Data.GetBuffer();
		std::array<IoBuffer, 1> Buffers{IoBufferBuilder::MakeCloneFromMemory(Buf.GetData(), Buf.GetSize())};
		return WriteResponse(ResponseCode, HttpContentType::kCbObject, Buffers);
	}
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, CbArray Array)
{
	if (m_AcceptType == HttpContentType::kJSON)
	{
		ExtendableStringBuilder<1024> Sb;
		WriteResponse(ResponseCode, HttpContentType::kJSON, Array.ToJson(Sb).ToView());
	}
	else if (m_AcceptType == HttpContentType::kYAML)
	{
		ExtendableStringBuilder<1024> Sb;
		WriteResponse(ResponseCode, HttpContentType::kYAML, Array.ToYaml(Sb).ToView());
	}
	else
	{
		SharedBuffer			Buf = Array.GetBuffer();
		std::array<IoBuffer, 1> Buffers{IoBufferBuilder::MakeCloneFromMemory(Buf.GetData(), Buf.GetSize())};
		return WriteResponse(ResponseCode, HttpContentType::kCbObject, Buffers);
	}
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, std::string_view ResponseString)
{
	return WriteResponse(ResponseCode, ContentType, std::u8string_view{(char8_t*)ResponseString.data(), ResponseString.size()});
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, IoBuffer Blob)
{
	std::array<IoBuffer, 1> Buffers{Blob};
	return WriteResponse(ResponseCode, ContentType, Buffers);
}

void
HttpServerRequest::WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, CompositeBuffer& Payload)
{
	std::span<const SharedBuffer> Segments = Payload.GetSegments();

	eastl::fixed_vector<IoBuffer, 64> Buffers;
	Buffers.reserve(Segments.size());

	for (auto& Segment : Segments)
	{
		Buffers.push_back(Segment.AsIoBuffer());
	}

	WriteResponse(ResponseCode, ContentType, std::span<IoBuffer>(begin(Buffers), end(Buffers)));
}

std::string
HttpServerRequest::Decode(std::string_view PercentEncodedString)
{
	size_t		Length = PercentEncodedString.length();
	std::string Decoded;
	Decoded.reserve(Length);
	size_t Offset = 0;
	while (Offset < Length)
	{
		char C = PercentEncodedString[Offset];
		if (C == '%' && (Offset <= (Length - 3)))
		{
			std::string_view CharHash(&PercentEncodedString[Offset + 1], 2);
			uint8_t			 DecodedChar = 0;
			if (ParseHexBytes(CharHash, &DecodedChar))
			{
				Decoded.push_back((char)DecodedChar);
				Offset += 3;
			}
			else
			{
				Decoded.push_back(C);
				Offset++;
			}
		}
		else
		{
			Decoded.push_back(C);
			Offset++;
		}
	}
	return Decoded;
}

HttpServerRequest::QueryParams
HttpServerRequest::GetQueryParams()
{
	QueryParams Params;

	const std::string_view QStr = QueryString();

	const char* QueryIt	 = QStr.data();
	const char* QueryEnd = QueryIt + QStr.size();

	while (QueryIt != QueryEnd)
	{
		if (*QueryIt == '&')
		{
			++QueryIt;
			continue;
		}

		size_t				   QueryLen = ptrdiff_t(QueryEnd - QueryIt);
		const std::string_view Query{QueryIt, QueryLen};

		size_t DelimIndex = Query.find('&', 0);

		if (DelimIndex == std::string_view::npos)
		{
			DelimIndex = Query.size();
		}

		std::string_view ThisQuery{QueryIt, DelimIndex};

		size_t EqIndex = ThisQuery.find('=', 0);

		if (EqIndex != std::string_view::npos)
		{
			std::string_view Param{ThisQuery.data(), EqIndex};
			ThisQuery.remove_prefix(EqIndex + 1);

			Params.KvPairs.emplace_back(Param, ThisQuery);
		}

		QueryIt += DelimIndex;
	}

	return Params;
}

Oid
HttpServerRequest::SessionId() const
{
	if (m_Flags & kHaveSessionId)
	{
		return m_SessionId;
	}

	m_SessionId = ParseSessionId();
	m_Flags |= kHaveSessionId;
	return m_SessionId;
}

uint32_t
HttpServerRequest::RequestId() const
{
	if (m_Flags & kHaveRequestId)
	{
		return m_RequestId;
	}

	m_RequestId = ParseRequestId();
	m_Flags |= kHaveRequestId;
	return m_RequestId;
}

CbObject
HttpServerRequest::ReadPayloadObject()
{
	if (IoBuffer Payload = ReadPayload())
	{
		if (m_ContentType == HttpContentType::kJSON)
		{
			std::string Json(reinterpret_cast<const char*>(Payload.GetData()), Payload.GetSize());
			std::string Err;

			CbFieldIterator It = LoadCompactBinaryFromJson(Json, Err);
			if (Err.empty())
			{
				return It.AsObject();
			}
			return CbObject();
		}
		CbValidateError ValidationError = CbValidateError::None;
		if (CbObject ResponseObject = ValidateAndReadCompactBinaryObject(std::move(Payload), ValidationError);
			ValidationError == CbValidateError::None)
		{
			return ResponseObject;
		}
	}
	return {};
}

CbPackage
HttpServerRequest::ReadPayloadPackage()
{
	if (IoBuffer Payload = ReadPayload())
	{
		return ParsePackageMessage(std::move(Payload));
	}

	return {};
}

//////////////////////////////////////////////////////////////////////////

void
HttpRequestRouter::AddPattern(const char* Id, const char* Regex)
{
	ZEN_ASSERT(m_PatternMap.find(Id) == m_PatternMap.end());
	ZEN_ASSERT(!m_IsFinalized);

	m_PatternMap.insert({Id, Regex});
}

void
HttpRequestRouter::AddMatcher(const char* Id, std::function<bool(std::string_view)>&& Matcher)
{
	ZEN_ASSERT(m_MatcherNameMap.find(Id) == m_MatcherNameMap.end());
	ZEN_ASSERT(!m_IsFinalized);

	const int MatcherIndex = gsl::narrow_cast<int>(m_MatcherFunctions.size());
	m_MatcherFunctions.push_back(Matcher);
	m_MatcherNameMap.insert({Id, MatcherIndex});
}

void
HttpRequestRouter::RegisterRoute(const char* UriPattern, HttpRequestRouter::HandlerFunc_t&& HandlerFunc, HttpVerb SupportedVerbs)
{
	ZEN_ASSERT(!m_IsFinalized);

	if (ExtendableStringBuilder<128> ExpandedRegex; ProcessRegexSubstitutions(UriPattern, ExpandedRegex))
	{
		// Regex route
		m_RegexHandlers.emplace_back(ExpandedRegex.c_str(), SupportedVerbs, std::move(HandlerFunc), UriPattern);
	}
	else
	{
		// New-style regex-free route. More efficient and should be used for everything eventually

		int RegexLen = gsl::narrow_cast<int>(strlen(UriPattern));

		int i = 0;

		std::vector<int> MatcherIndices;

		while (i < RegexLen)
		{
			if (UriPattern[i] == '{')
			{
				bool IsComplete	  = false;
				int	 PatternStart = i + 1;
				while (++i < RegexLen)
				{
					if (UriPattern[i] == '}')
					{
						std::string_view Pattern(&UriPattern[PatternStart], i - PatternStart);
						if (auto it = m_MatcherNameMap.find(std::string(Pattern)); it != m_MatcherNameMap.end())
						{
							// It's a match
							MatcherIndices.push_back(it->second);
							IsComplete = true;
							++i;
							break;
						}
						else
						{
							throw std::runtime_error(fmt::format("unknown matcher pattern '{}' in URI pattern '{}'", Pattern, UriPattern));
						}
					}
				}
				if (!IsComplete)
				{
					throw std::runtime_error(fmt::format("unterminated matcher pattern in URI pattern '{}'", UriPattern));
				}
			}
			else
			{
				if (UriPattern[i] == '/')
				{
					throw std::runtime_error(fmt::format("unexpected '/' in literal segment of URI pattern '{}'", UriPattern));
				}

				int SegmentStart = i;
				while (++i < RegexLen && UriPattern[i] != '/')
					;

				std::string_view Segment(&UriPattern[SegmentStart], (i - SegmentStart));
				int				 LiteralIndex = gsl::narrow_cast<int>(m_Literals.size());
				m_Literals.push_back(std::string(Segment));
				MatcherIndices.push_back(-1 - LiteralIndex);
			}

			if (i < RegexLen && UriPattern[i] == '/')
			{
				++i;  // skip slash
			}
		}

		m_MatcherEndpoints.emplace_back(std::move(MatcherIndices), SupportedVerbs, std::move(HandlerFunc), UriPattern);
	}
}

std::string_view
HttpRouterRequest::GetCapture(uint32_t Index) const
{
	if (!m_CapturedSegments.empty())
	{
		ZEN_ASSERT(Index < m_CapturedSegments.size());
		return m_CapturedSegments[Index];
	}

	ZEN_ASSERT(Index < m_Match.size());

	const auto& Match = m_Match[Index];

	return std::string_view(&*Match.first, Match.second - Match.first);
}

bool
HttpRequestRouter::ProcessRegexSubstitutions(const char* Regex, StringBuilderBase& OutExpandedRegex)
{
	size_t RegexLen = strlen(Regex);

	bool HasRegex = false;

	std::vector<std::string> UnknownPatterns;

	for (size_t i = 0; i < RegexLen;)
	{
		bool matched = false;

		if (Regex[i] == '{' && ((i == 0) || (Regex[i - 1] != '\\')))
		{
			// Might have a pattern reference - find closing brace

			for (size_t j = i + 1; j < RegexLen; ++j)
			{
				if (Regex[j] == '}')
				{
					std::string Pattern(&Regex[i + 1], j - i - 1);

					if (auto it = m_PatternMap.find(Pattern); it != m_PatternMap.end())
					{
						OutExpandedRegex.Append(it->second.c_str());
						HasRegex = true;
					}
					else
					{
						UnknownPatterns.push_back(Pattern);
					}

					// skip ahead
					i = j + 1;

					matched = true;

					break;
				}
			}
		}

		if (!matched)
		{
			OutExpandedRegex.Append(Regex[i++]);
		}
	}

	if (HasRegex)
	{
		if (UnknownPatterns.size() > 0)
		{
			std::string UnknownList;
			for (const auto& Pattern : UnknownPatterns)
			{
				if (!UnknownList.empty())
				{
					UnknownList += ", ";
				}
				UnknownList += "'";
				UnknownList += Pattern;
				UnknownList += "'";
			}

			throw std::runtime_error(fmt::format("unknown pattern(s) {} in regex route '{}'", UnknownList, Regex));
		}

		return true;
	}

	return false;
}

bool
HttpRequestRouter::HandleRequest(zen::HttpServerRequest& Request)
{
	if (!m_IsFinalized)
	{
		m_IsFinalized = true;
	}

	const HttpVerb Verb = Request.RequestVerb();

	std::string_view  Uri = Request.RelativeUri();
	HttpRouterRequest RouterRequest(Request);

	// First try new-style matcher routes

	for (const MatcherEndpoint& Handler : m_MatcherEndpoints)
	{
		if ((Handler.Verbs & Verb) == Verb)
		{
			size_t					UriPos	 = 0;
			const size_t			UriLen	 = Uri.length();
			const std::vector<int>& Matchers = Handler.ComponentIndices;
			bool					IsMatch	 = true;

			std::vector<std::string_view> CapturedSegments;

			CapturedSegments.emplace_back(Uri);

			for (int MatcherIndex : Matchers)
			{
				if (UriPos >= UriLen)
				{
					IsMatch = false;
					break;
				}

				if (MatcherIndex < 0)
				{
					// Literal match
					int				   LitIndex = -MatcherIndex - 1;
					const std::string& LitStr	= m_Literals[LitIndex];
					size_t			   LitLen	= LitStr.length();

					if (Uri.substr(UriPos, LitLen) == LitStr)
					{
						UriPos += LitLen;
					}
					else
					{
						IsMatch = false;
						break;
					}
				}
				else
				{
					// Matcher function
					size_t SegmentStart = UriPos;
					while (UriPos < UriLen && Uri[UriPos] != '/')
					{
						++UriPos;
					}

					std::string_view Segment = Uri.substr(SegmentStart, UriPos - SegmentStart);

					if (m_MatcherFunctions[MatcherIndex](Segment))
					{
						CapturedSegments.push_back(Segment);
					}
					else
					{
						IsMatch = false;
						break;
					}
				}

				// Skip slash
				if (UriPos < UriLen && Uri[UriPos] == '/')
				{
					++UriPos;
				}
			}

			if (IsMatch && UriPos == UriLen)
			{
#if ZEN_WITH_OTEL
				if (otel::Span* ActiveSpan = otel::Span::GetCurrentSpan())
				{
					ExtendableStringBuilder<128> RoutePath;
					RoutePath.Append(Request.Service().BaseUri());
					RoutePath.Append(Handler.Pattern);
					ActiveSpan->AddAttribute("http.route"sv, RoutePath.ToView());
				}
#endif

				RouterRequest.m_CapturedSegments = std::move(CapturedSegments);
				Handler.Handler(RouterRequest);

				return true;  // Route matched
			}
		}
	}

	// Old-style regex routes

	for (const auto& Handler : m_RegexHandlers)
	{
		if ((Handler.Verbs & Verb) == Verb && regex_match(begin(Uri), end(Uri), RouterRequest.m_Match, Handler.RegEx))
		{
#if ZEN_WITH_OTEL
			if (otel::Span* ActiveSpan = otel::Span::GetCurrentSpan())
			{
				ExtendableStringBuilder<128> RoutePath;
				RoutePath.Append(Request.Service().BaseUri());
				RoutePath.Append(Handler.Pattern);
				ActiveSpan->AddAttribute("http.route"sv, RoutePath.ToView());
			}
#endif

			Handler.Handler(RouterRequest);

			return true;  // Route matched
		}
	}

	return false;  // No route matched
}

//////////////////////////////////////////////////////////////////////////

int
HttpServer::Initialize(int BasePort, std::filesystem::path DataDir)
{
	return OnInitialize(BasePort, std::move(DataDir));
}

void
HttpServer::Run(bool IsInteractiveSession)
{
	OnRun(IsInteractiveSession);
}

void
HttpServer::RequestExit()
{
	OnRequestExit();
}
void
HttpServer::Close()
{
	OnClose();
}

void
HttpServer::RegisterService(HttpService& Service)
{
	OnRegisterService(Service);
	m_KnownServices.push_back(&Service);
}

void
HttpServer::EnumerateServices(std::function<void(HttpService& Service)>&& Callback)
{
	// This doesn't take a lock because services should only be registered during
	// server initialization, before it starts accepting requests
	for (HttpService* Service : m_KnownServices)
	{
		Callback(*Service);
	}
}

void
HttpServer::SetHttpRequestFilter(IHttpRequestFilter* RequestFilter)
{
	OnSetHttpRequestFilter(RequestFilter);
}

//////////////////////////////////////////////////////////////////////////

HttpRpcHandler::HttpRpcHandler()
{
}

HttpRpcHandler::~HttpRpcHandler()
{
}

void
HttpRpcHandler::AddRpc(std::string_view RpcId, std::function<void(CbObject& RpcArgs)> HandlerFunction)
{
	ZEN_UNUSED(RpcId, HandlerFunction);
}

//////////////////////////////////////////////////////////////////////////

Ref<HttpServer>
CreateHttpServerClass(const std::string_view ServerClass, const HttpServerConfig& Config)
{
	if (ServerClass == "asio"sv)
	{
		ZEN_INFO("using asio HTTP server implementation")
		return CreateHttpAsioServer(AsioConfig{.ThreadCount		  = Config.ThreadCount,
											   .ForceLoopback	  = Config.ForceLoopback,
											   .IsDedicatedServer = Config.IsDedicatedServer});
	}
#if ZEN_WITH_HTTPSYS
	else if (ServerClass == "httpsys"sv)
	{
		ZEN_INFO("using http.sys server implementation")
		return Ref<HttpServer>(CreateHttpSysServer({.ThreadCount			 = Config.ThreadCount,
													.AsyncWorkThreadCount	 = Config.HttpSys.AsyncWorkThreadCount,
													.IsAsyncResponseEnabled	 = Config.HttpSys.IsAsyncResponseEnabled,
													.IsRequestLoggingEnabled = Config.HttpSys.IsRequestLoggingEnabled,
													.IsDedicatedServer		 = Config.IsDedicatedServer,
													.ForceLoopback			 = Config.ForceLoopback}));
	}
#endif
	else if (ServerClass == "null"sv)
	{
		ZEN_INFO("using null HTTP server implementation")
		return Ref<HttpServer>(new HttpNullServer);
	}
	else
	{
		ZEN_WARN("unknown HTTP server implementation '{}', falling back to default", ServerClass)

#if ZEN_WITH_HTTPSYS
		return CreateHttpServerClass("httpsys"sv, Config);
#else
		return CreateHttpServerClass("asio"sv, Config);
#endif
	}
}

#if ZEN_WITH_PLUGINS
Ref<HttpServer>
CreateHttpServerPlugin(const HttpServerPluginConfig& PluginConfig)
{
	const std::string& PluginName = PluginConfig.PluginName;

	ZEN_INFO("using '{}' plugin HTTP server implementation", PluginName)

	if (PluginName.starts_with("builtin:"sv))
	{
#	if 0
		Ref<TransportPlugin> Plugin = {};
		if (PluginName == "builtin:winsock"sv)
		{
			Plugin = CreateSocketTransportPlugin();
		}
		else if (PluginName == "builtin:asio"sv)
		{
			Plugin = CreateAsioTransportPlugin();
		}
		else
		{
			ZEN_WARN("Unknown builtin plugin '{}'", PluginName)
			return {};
		}

		ZEN_ASSERT(!Plugin.IsNull());

		for (const std::pair<std::string, std::string>& Option : PluginConfig.PluginOptions)
		{
			Plugin->Configure(Option.first.c_str(), Option.second.c_str());
		}

		Ref<HttpPluginServer> Server{CreateHttpPluginServer()};
		Server->AddPlugin(Plugin);
		return Server;
#	else
		ZEN_WARN("Builtin plugin '{}' is not supported", PluginName)
		return {};
#	endif
	}

	Ref<DllTransportPlugin> DllPlugin{CreateDllTransportPlugin()};
	if (!DllPlugin->LoadDll(PluginName))
	{
		return {};
	}

	for (const std::pair<std::string, std::string>& Option : PluginConfig.PluginOptions)
	{
		DllPlugin->ConfigureDll(PluginName, Option.first.c_str(), Option.second.c_str());
	}

	Ref<HttpPluginServer> Server{CreateHttpPluginServer()};
	Server->AddPlugin(DllPlugin);
	return Server;
}
#endif

Ref<HttpServer>
CreateHttpServer(const HttpServerConfig& Config)
{
	using namespace std::literals;

#if ZEN_WITH_PLUGINS
	if (Config.PluginConfigs.empty())
	{
		return CreateHttpServerClass(Config.ServerClass, Config);
	}
	else
	{
		Ref<HttpMultiServer> Server{new HttpMultiServer()};
		Server->AddServer(CreateHttpServerClass(Config.ServerClass, Config));

		for (const HttpServerPluginConfig& PluginConfig : Config.PluginConfigs)
		{
			Ref<HttpServer> PluginServer = CreateHttpServerPlugin(PluginConfig);
			if (!PluginServer.IsNull())
			{
				Server->AddServer(PluginServer);
			}
		}

		return Server;
	}
#else
	return CreateHttpServerClass(Config.ServerClass, Config);
#endif
}

//////////////////////////////////////////////////////////////////////////

bool
HandlePackageOffers(HttpService& Service, HttpServerRequest& Request, Ref<IHttpPackageHandler>& PackageHandlerRef)
{
	if (Request.RequestVerb() == HttpVerb::kPost)
	{
		if (Request.RequestContentType() == HttpContentType::kCbPackageOffer)
		{
			// The client is presenting us with a package attachments offer, we need
			// to filter it down to the list of attachments we need them to send in
			// the follow-up request

			PackageHandlerRef = Service.HandlePackageRequest(Request);

			if (PackageHandlerRef)
			{
				CbValidateError ValidationError = CbValidateError::None;
				if (CbObject OfferMessage = ValidateAndReadCompactBinaryObject(IoBuffer(Request.ReadPayload()), ValidationError);
					ValidationError == CbValidateError::None)
				{
					std::vector<IoHash> OfferCids;

					for (auto& CidEntry : OfferMessage["offer"])
					{
						if (!CidEntry.IsHash())
						{
							// Should yield bad request response?

							ZEN_WARN("found invalid entry in offer");

							continue;
						}

						OfferCids.push_back(CidEntry.AsHash());
					}

					ZEN_TRACE("request #{} -> filtering offer of {} entries", Request.RequestId(), OfferCids.size());

					PackageHandlerRef->FilterOffer(OfferCids);

					ZEN_TRACE("request #{} -> filtered to {} entries", Request.RequestId(), OfferCids.size());

					CbObjectWriter ResponseWriter;
					ResponseWriter.BeginArray("need");

					for (const IoHash& Cid : OfferCids)
					{
						ResponseWriter.AddHash(Cid);
					}

					ResponseWriter.EndArray();

					// Emit filter response
					Request.WriteResponse(HttpResponseCode::OK, ResponseWriter.Save());
				}
				else
				{
					Request.WriteResponse(HttpResponseCode::BadRequest,
										  HttpContentType::kText,
										  fmt::format("Invalid request payload: '{}'", ToString(ValidationError)));
				}
				return true;
			}
		}
		else if (Request.RequestContentType() == HttpContentType::kCbPackage)
		{
			// Process chunks in package request

			PackageHandlerRef = Service.HandlePackageRequest(Request);

			// TODO: this should really be done in a streaming fashion, currently this emulates
			// the intended flow from an API perspective

			if (PackageHandlerRef)
			{
				PackageHandlerRef->OnRequestBegin();

				auto CreateBuffer = [&](const IoHash& Cid, uint64_t Size) -> IoBuffer {
					return PackageHandlerRef->CreateTarget(Cid, Size);
				};

				CbPackage Package = ParsePackageMessage(Request.ReadPayload(), CreateBuffer);

				PackageHandlerRef->OnRequestComplete();
			}
		}
	}
	return false;
}

//////////////////////////////////////////////////////////////////////////

#if ZEN_WITH_TESTS

TEST_CASE("http.common")
{
	using namespace std::literals;

	struct TestHttpService : public HttpService
	{
		TestHttpService() = default;

		virtual const char* BaseUri() const override { return "/test"; }
		virtual void		HandleRequest(HttpServerRequest& HttpServiceRequest) override { ZEN_UNUSED(HttpServiceRequest); }
	};

	struct TestHttpServerRequest : public HttpServerRequest
	{
		TestHttpServerRequest(HttpService& Service, std::string_view Uri) : HttpServerRequest(Service) { m_Uri = Uri; }
		virtual IoBuffer ReadPayload() override { return IoBuffer(); }

		virtual bool			 IsLocalMachineRequest() const override { return false; }
		virtual std::string_view GetAuthorizationHeader() const override { return {}; }

		virtual void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, std::span<IoBuffer> Blobs) override
		{
			ZEN_UNUSED(ResponseCode, ContentType, Blobs);
		}
		virtual void WriteResponse(HttpResponseCode ResponseCode) override { ZEN_UNUSED(ResponseCode); }
		virtual void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, std::u8string_view ResponseString) override
		{
			ZEN_UNUSED(ResponseCode, ContentType, ResponseString);
		}
		virtual void WriteResponseAsync(std::function<void(HttpServerRequest&)>&& ContinuationHandler) override
		{
			ZEN_UNUSED(ContinuationHandler);
		}
		virtual Oid		 ParseSessionId() const override { return Oid(); }
		virtual uint32_t ParseRequestId() const override { return 0; }
	};

	SUBCASE("router-regex")
	{
		bool					 HandledA  = false;
		bool					 HandledAA = false;
		std::vector<std::string> Captures;
		auto					 Reset = [&] {
			Captures.clear();
			HandledA = HandledAA = false;
		};

		TestHttpService Service;

		HttpRequestRouter r;
		r.AddPattern("a", "([[:alpha:]]+)");
		r.RegisterRoute(
			"{a}",
			[&](auto& Req) {
				HandledA = true;
				Captures = {std::string(Req.GetCapture(0))};
			},
			HttpVerb::kGet);

		r.RegisterRoute(
			"{a}/{a}",
			[&](auto& Req) {
				HandledAA = true;
				Captures  = {std::string(Req.GetCapture(1)), std::string(Req.GetCapture(2))};
			},
			HttpVerb::kGet);

		{
			Reset();
			TestHttpServerRequest req(Service, "abc"sv);
			r.HandleRequest(req);
			CHECK(HandledA);
			CHECK(!HandledAA);
			REQUIRE_EQ(Captures.size(), 1);
			CHECK_EQ(Captures[0], "abc"sv);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "abc/def"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
			CHECK(HandledAA);
			REQUIRE_EQ(Captures.size(), 2);
			CHECK_EQ(Captures[0], "abc"sv);
			CHECK_EQ(Captures[1], "def"sv);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "123"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "a123"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
		}
	}

	SUBCASE("router-matcher")
	{
		bool					 HandledA	  = false;
		bool					 HandledAA	  = false;
		bool					 HandledAB	  = false;
		bool					 HandledAandB = false;
		std::vector<std::string> Captures;
		auto					 Reset = [&] {
			HandledA = HandledAA = HandledAB = HandledAandB = false;
			Captures.clear();
		};

		TestHttpService	  Service;
		HttpRequestRouter r;
		r.AddMatcher("a", [](std::string_view In) -> bool { return In.length() % 2 == 0; });
		r.AddMatcher("b", [](std::string_view In) -> bool { return In.length() % 3 == 0; });
		r.RegisterRoute(
			"{a}",
			[&](auto& Req) {
				HandledA = true;
				Captures = {std::string(Req.GetCapture(1))};
			},
			HttpVerb::kGet);
		r.RegisterRoute(
			"{a}/{a}",
			[&](auto& Req) {
				HandledAA = true;
				Captures  = {std::string(Req.GetCapture(1)), std::string(Req.GetCapture(2))};
			},
			HttpVerb::kGet);
		r.RegisterRoute(
			"{a}/{b}",
			[&](auto& Req) {
				HandledAB = true;
				Captures  = {std::string(Req.GetCapture(1)), std::string(Req.GetCapture(2))};
			},
			HttpVerb::kGet);
		r.RegisterRoute(
			"{a}/and/{b}",
			[&](auto& Req) {
				HandledAandB = true;
				Captures	 = {std::string(Req.GetCapture(1)), std::string(Req.GetCapture(2))};
			},
			HttpVerb::kGet);

		{
			Reset();
			TestHttpServerRequest req{Service, "ab"sv};
			r.HandleRequest(req);
			CHECK(HandledA);
			CHECK(!HandledAA);
			CHECK(!HandledAB);

			REQUIRE_EQ(Captures.size(), 1);
			CHECK_EQ(Captures[0], "ab"sv);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "ab/def"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
			CHECK(!HandledAA);
			CHECK(HandledAB);
			REQUIRE_EQ(Captures.size(), 2);
			CHECK_EQ(Captures[0], "ab"sv);
			CHECK_EQ(Captures[1], "def"sv);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "ab/and/def"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
			CHECK(!HandledAA);
			CHECK(!HandledAB);
			CHECK(HandledAandB);
			REQUIRE_EQ(Captures.size(), 2);
			CHECK_EQ(Captures[0], "ab"sv);
			CHECK_EQ(Captures[1], "def"sv);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "123"sv};
			r.HandleRequest(req);
			CHECK(!HandledA);
			CHECK(!HandledAA);
			CHECK(!HandledAB);
		}

		{
			Reset();
			TestHttpServerRequest req{Service, "a123"sv};
			r.HandleRequest(req);
			CHECK(HandledA);
			CHECK(!HandledAA);
			CHECK(!HandledAB);
		}
	}

	SUBCASE("content-type")
	{
		for (uint8_t i = 0; i < uint8_t(HttpContentType::kCOUNT); ++i)
		{
			HttpContentType Ct{i};

			if (Ct != HttpContentType::kUnknownContentType)
			{
				CHECK_EQ(Ct, ParseContentType(MapContentTypeToString(Ct)));
			}
		}
	}
}

void
http_forcelink()
{
}

#endif

}  // namespace zen