Add HTTP client implementation with logging for chat API

- Implemented a new HTTP client in send_with_httplib.cpp using the httplib library.
- Added a logger function to log request and response details, including headers.
- Created a main function to send a POST request to the chat API with a sample message.
- Included error handling for the HTTP response.

Author: yhirose

httplib.h

@@ -7246,9 +7246,54 @@ inline ssize_t detail::BodyReader::read(char *buf, size_t len) {
     return n;
   }
 
-  // TODO: Chunked transfer encoding (Phase 2.3 extension)
-  // For now, return error for chunked
-  return -1;
+  // Chunked transfer encoding
+  // If no data remaining in current chunk, read next chunk header
+  while (current_chunk_remaining == 0) {
+    // Read chunk size line
+    const size_t line_buf_size = 32;
+    char line_buf[line_buf_size];
+    stream_line_reader line_reader(*stream, line_buf, line_buf_size);
+
+    if (!line_reader.getline()) {
+      eof = true;
+      return 0;
+    }
+
+    // Skip empty lines (CRLF between chunks)
+    if (line_reader.size() <= 2 && (strcmp(line_reader.ptr(), "\r\n") == 0 ||
+                                    strcmp(line_reader.ptr(), "\n") == 0)) {
+      continue;
+    }
+
+    // Parse chunk size (hex)
+    char *end_ptr;
+    auto chunk_size = std::strtoul(line_reader.ptr(), &end_ptr, 16);
+    if (end_ptr == line_reader.ptr() || chunk_size == ULONG_MAX) {
+      return -1; // Parse error
+    }
+
+    if (chunk_size == 0) {
+      // Final chunk
+      eof = true;
+      return 0;
+    }
+
+    current_chunk_remaining = chunk_size;
+  }
+
+  // Read from current chunk
+  auto to_read = (std::min)(len, current_chunk_remaining);
+  auto n = stream->read(buf, to_read);
+
+  if (n <= 0) {
+    eof = true;
+    return n;
+  }
+
+  current_chunk_remaining -= static_cast<size_t>(n);
+  bytes_read += static_cast<size_t>(n);
+
+  return n;
 }
 
 namespace detail {

test/test20.cc

@@ -812,7 +812,8 @@ class OpenStreamDirectTest : public ::testing::Test {
     svr_.Get("/chunked", [](const httplib::Request &, httplib::Response &res) {
       res.set_chunked_content_provider(
           "text/plain", [](size_t offset, httplib::DataSink &sink) {
-            if (offset < 3) {
+            // Send "chunk" 3 times (offset 0, 5, 10)
+            if (offset < 15) {
               sink.write("chunk", 5);
               return true;
             }
@@ -897,3 +898,31 @@ TEST_F(OpenStreamDirectTest, ConnectionError) {
   EXPECT_FALSE(handle.is_valid());
   EXPECT_NE(httplib::Error::Success, handle.error);
 }
+
+TEST_F(OpenStreamDirectTest, ChunkedResponse) {
+  httplib::Client cli("127.0.0.1", 8787);
+
+  auto handle = cli.open_stream_direct("/chunked");
+  ASSERT_TRUE(handle.is_valid());
+  EXPECT_TRUE(handle.body_reader_.chunked);
+
+  auto body = handle.read_all();
+  // Server sends "chunk" 3 times
+  EXPECT_EQ("chunkchunkchunk", body);
+}
+
+TEST_F(OpenStreamDirectTest, ChunkedResponseInPieces) {
+  httplib::Client cli("127.0.0.1", 8787);
+
+  auto handle = cli.open_stream_direct("/chunked");
+  ASSERT_TRUE(handle.is_valid());
+
+  std::string result;
+  char buf[3]; // Small buffer to force multiple reads
+  ssize_t n;
+  while ((n = handle.read(buf, sizeof(buf))) > 0) {
+    result.append(buf, static_cast<size_t>(n));
+  }
+
+  EXPECT_EQ("chunkchunkchunk", result);
+}