From 5603d284bf4af763169d3c37f4ff17f68203fdf8 Mon Sep 17 00:00:00 2001
From: heinrich5991 <heinrich5991@gmail.com>
Date: Thu, 14 Mar 2024 12:18:05 +0100
Subject: [PATCH] Parse `Date` and `Last-Modified` HTTP headers

---
 ddnet-libs                 |  2 +-
 src/engine/shared/http.cpp | 70 ++++++++++++++++++++++++++++++++++++++
 src/engine/shared/http.h   |  9 +++++
 3 files changed, 80 insertions(+), 1 deletion(-)

diff --git a/ddnet-libs b/ddnet-libs
index a4fbe0e52..87fbb5783 160000
--- a/ddnet-libs
+++ b/ddnet-libs
@@ -1 +1 @@
-Subproject commit a4fbe0e52338a129bc3ac2e3a1de54de1d175279
+Subproject commit 87fbb57839080f40d16cd77d8ad11ae91bb9c849
diff --git a/src/engine/shared/http.cpp b/src/engine/shared/http.cpp
index 76bbec657..6b72e980d 100644
--- a/src/engine/shared/http.cpp
+++ b/src/engine/shared/http.cpp
@@ -148,6 +148,8 @@ bool CHttpRequest::ConfigureHandle(void *pHandle)
 	curl_easy_setopt(pH, CURLOPT_USERAGENT, GAME_NAME " " GAME_RELEASE_VERSION " (" CONF_PLATFORM_STRING "; " CONF_ARCH_STRING ")");
 	curl_easy_setopt(pH, CURLOPT_ACCEPT_ENCODING, ""); // Use any compression algorithm supported by libcurl.
 
+	curl_easy_setopt(pH, CURLOPT_HEADERDATA, this);
+	curl_easy_setopt(pH, CURLOPT_HEADERFUNCTION, HeaderCallback);
 	curl_easy_setopt(pH, CURLOPT_WRITEDATA, this);
 	curl_easy_setopt(pH, CURLOPT_WRITEFUNCTION, WriteCallback);
 	curl_easy_setopt(pH, CURLOPT_NOPROGRESS, 0L);
@@ -206,6 +208,52 @@ bool CHttpRequest::ConfigureHandle(void *pHandle)
 	return true;
 }
 
+size_t CHttpRequest::OnHeader(char *pHeader, size_t HeaderSize)
+{
+	// `pHeader` is NOT null-terminated.
+	// `pHeader` has a trailing newline.
+
+	if(HeaderSize <= 1)
+	{
+		m_HeadersEnded = true;
+		return HeaderSize;
+	}
+	if(m_HeadersEnded)
+	{
+		// redirect, clear old headers
+		m_HeadersEnded = false;
+		m_ResultDate = {};
+		m_ResultLastModified = {};
+	}
+
+	static const char DATE[] = "Date: ";
+	static const char LAST_MODIFIED[] = "Last-Modified: ";
+
+	// Trailing newline and null termination evens out.
+	if(HeaderSize - 1 >= sizeof(DATE) - 1 && str_startswith_nocase(pHeader, DATE))
+	{
+		char aValue[128];
+		str_truncate(aValue, sizeof(aValue), pHeader + (sizeof(DATE) - 1), HeaderSize - (sizeof(DATE) - 1) - 1);
+		int64_t Value = curl_getdate(aValue, nullptr);
+		if(Value != -1)
+		{
+			m_ResultDate = Value;
+		}
+	}
+	if(HeaderSize - 1 >= sizeof(LAST_MODIFIED) - 1 && str_startswith_nocase(pHeader, LAST_MODIFIED))
+	{
+		char aValue[128];
+		str_truncate(aValue, sizeof(aValue), pHeader + (sizeof(LAST_MODIFIED) - 1), HeaderSize - (sizeof(LAST_MODIFIED) - 1) - 1);
+		int64_t Value = curl_getdate(aValue, nullptr);
+		if(Value != -1)
+		{
+			m_ResultLastModified = Value;
+		}
+	}
+
+	return HeaderSize;
+}
+
 size_t CHttpRequest::OnData(char *pData, size_t DataSize)
 {
 	// Need to check for the maximum response size here as curl can only
@@ -244,6 +292,12 @@ size_t CHttpRequest::OnData(char *pData, size_t DataSize)
 	}
 }
 
+size_t CHttpRequest::HeaderCallback(char *pData, size_t Size, size_t Number, void *pUser)
+{
+	dbg_assert(Size == 1, "invalid size parameter passed to header callback");
+	return ((CHttpRequest *)pUser)->OnHeader(pData, Number);
+}
+
 size_t CHttpRequest::WriteCallback(char *pData, size_t Size, size_t Number, void *pUser)
 {
 	return ((CHttpRequest *)pUser)->OnData(pData, Size * Number);
@@ -390,6 +444,22 @@ int CHttpRequest::StatusCode() const
 	return m_StatusCode;
 }
 
+std::optional<int64_t> CHttpRequest::ResultAgeSeconds() const
+{
+	dbg_assert(State() == EHttpState::DONE, "Request not done");
+	if(!m_ResultDate || !m_ResultLastModified)
+	{
+		return {};
+	}
+	return *m_ResultDate - *m_ResultLastModified;
+}
+
+std::optional<int64_t> CHttpRequest::ResultLastModified() const
+{
+	dbg_assert(State() == EHttpState::DONE, "Request not done");
+	return m_ResultLastModified;
+}
+
 bool CHttp::Init(std::chrono::milliseconds ShutdownDelay)
 {
 	m_ShutdownDelay = ShutdownDelay;
diff --git a/src/engine/shared/http.h b/src/engine/shared/http.h
index 87b808be9..86e53fac9 100644
--- a/src/engine/shared/http.h
+++ b/src/engine/shared/http.h
@@ -118,6 +118,9 @@ class CHttpRequest : public IHttpRequest
 	std::atomic<bool> m_Abort{false};
 
 	int m_StatusCode = 0;
+	bool m_HeadersEnded = false;
+	std::optional<int64_t> m_ResultDate = {};
+	std::optional<int64_t> m_ResultLastModified = {};
 
 	// Abort the request with an error if `BeforeInit()` returns false.
 	bool BeforeInit();
@@ -125,11 +128,15 @@ class CHttpRequest : public IHttpRequest
 	// `pHandle` can be nullptr if no handle was ever created for this request.
 	void OnCompletionInternal(void *pHandle, unsigned int Result); // void * == CURL *, unsigned int == CURLcode
 
+	// Abort the request if `OnHeader()` returns something other than
+	// `DataSize`. `pHeader` is NOT null-terminated.
+	size_t OnHeader(char *pHeader, size_t HeaderSize);
 	// Abort the request if `OnData()` returns something other than
 	// `DataSize`.
 	size_t OnData(char *pData, size_t DataSize);
 
 	static int ProgressCallback(void *pUser, double DlTotal, double DlCurr, double UlTotal, double UlCurr);
+	static size_t HeaderCallback(char *pData, size_t Size, size_t Number, void *pUser);
 	static size_t WriteCallback(char *pData, size_t Size, size_t Number, void *pUser);
 
 protected:
@@ -207,6 +214,8 @@ public:
 	const SHA256_DIGEST &ResultSha256() const;
 
 	int StatusCode() const;
+	std::optional<int64_t> ResultAgeSeconds() const;
+	std::optional<int64_t> ResultLastModified() const;
 };
 
 inline std::unique_ptr<CHttpRequest> HttpHead(const char *pUrl)