curl_url_handle: Add method to replace the hostname of a URL

Also adds a section in the curl_url test suite.

2 files changed, 57 insertions, 0 deletions

diff --git a/src/other_tools/utils/curl_url_handle.cpp b/src/other_tools/utils/curl_url_handle.cpp
index 90102e0b..5722a1cb 100644
--- a/src/other_tools/utils/curl_url_handle.cpp
+++ b/src/other_tools/utils/curl_url_handle.cpp
@@ -788,3 +788,49 @@ auto CurlURLHandle::NoproxyStringMatches(std::string const& no_proxy) noexcept
         return std::nullopt;
     }
 }
+
+auto CurlURLHandle::ReplaceHostname(std::string const& url,
+                                    std::string const& hostname) noexcept
+    -> std::optional<std::string> {
+    try {
+        // We should not guess the scheme based on current hostname, as it may
+        // cause the URL with the new hostname to falsely fail; we set
+        // use_default_scheme instead. Additionally, we set use_no_authority to
+        // false as the given URL MUST already have a hostname to be replaced.
+        if (auto parsed_url = CreatePermissive(url,
+                                               false /*use_guess_scheme*/,
+                                               true /*use_default_scheme*/,
+                                               true /*use_non_support_scheme*/,
+                                               false /*use_no_authority*/,
+                                               true /*use_path_as_is*/,
+                                               true /*use_allow_space*/,
+                                               true /*ignore_fatal*/)) {
+            if (*parsed_url == nullptr) {
+                return std::nullopt;
+            }
+            auto rc = curl_url_set(parsed_url.value()->handle_.get(),
+                                   CURLUPART_HOST,
+                                   hostname.c_str(),
+                                   0U);
+            if (rc != CURLUE_OK) {
+                Logger::Log(LogLevel::Debug,
+                            "CurlURLHandle: setting hostname {} in URL {} "
+                            "failed with:\n{}",
+                            hostname,
+                            url,
+                            curl_url_strerror(rc));
+                return std::nullopt;
+            }
+            return parsed_url.value()->GetURL(false /*use_default_port*/,
+                                              true /*use_default_scheme*/,
+                                              false /*use_no_default_port*/,
+                                              true /*ignore_fatal*/);
+        }
+    } catch (std::exception const& ex) {
+        Logger::Log(LogLevel::Debug,
+                    "CurlURLHandle: Replacing URL hostname failed unexpectedly "
+                    "with:\n{}",
+                    ex.what());
+    }
+    return std::nullopt;
+}
diff --git a/src/other_tools/utils/curl_url_handle.hpp b/src/other_tools/utils/curl_url_handle.hpp
index dfd278d7..5648a535 100644
--- a/src/other_tools/utils/curl_url_handle.hpp
+++ b/src/other_tools/utils/curl_url_handle.hpp
@@ -154,6 +154,17 @@ class CurlURLHandle {
     [[nodiscard]] auto NoproxyStringMatches(
         std::string const& no_proxy) noexcept -> std::optional<bool>;
 
+    /// \brief Tries to replace the hostname of a given URL. This is done by
+    /// parsing the URL with minimal validity checks, replacing the original
+    /// hostname with the one given, then putting the new URL back together.
+    /// \note The given URL MUST have a hostname for this to succeed.
+    /// \note A missing scheme field will be set to "https://" and a missing
+    /// path field will be set to "/".
+    /// \returns The new URL or nullopt on errors. This method is never fatal.
+    [[nodiscard]] static auto ReplaceHostname(
+        std::string const& url,
+        std::string const& hostname) noexcept -> std::optional<std::string>;
+
   private:
     // IMPORTANT: the CurlContext must be initialized before any curl
     // object!