Update /<count>/ endpoints to use a '?count=' query parameter instead

In most RESTful APIs, path parameters are used to represent resources, and
query parameters are used to control how these resources are being filtered/sorted/...

The old /<count>/ functionality is kept alive to maintain backwards compatibility,
but new paths with query parameters are introduced and documented as the default
interface so future API methods don't break consistency by using query parameters.

1 files changed, 35 insertions, 15 deletions

diff --git a/src/rest.cpp b/src/rest.cpp
index ec9295b283..7025dd6ad1 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -194,15 +194,25 @@ static bool rest_headers(const std::any& context,
     std::vector<std::string> path;
     boost::split(path, param, boost::is_any_of("/"));
 
-    if (path.size() != 2)
-        return RESTERR(req, HTTP_BAD_REQUEST, "No header count specified. Use /rest/headers/<count>/<hash>.<ext>.");
-
-    const auto parsed_count{ToIntegral<size_t>(path[0])};
+    std::string raw_count;
+    std::string hashStr;
+    if (path.size() == 2) {
+        // deprecated path: /rest/headers/<count>/<hash>
+        hashStr = path[1];
+        raw_count = path[0];
+    } else if (path.size() == 1) {
+        // new path with query parameter: /rest/headers/<hash>?count=<count>
+        hashStr = path[0];
+        raw_count = req->GetQueryParameter("count").value_or("5");
+    } else {
+        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid URI format. Expected /rest/headers/<hash>.<ext>?count=<count>");
+    }
+
+    const auto parsed_count{ToIntegral<size_t>(raw_count)};
     if (!parsed_count.has_value() || *parsed_count < 1 || *parsed_count > MAX_REST_HEADERS_RESULTS) {
-        return RESTERR(req, HTTP_BAD_REQUEST, strprintf("Header count is invalid or out of acceptable range (1-%u): %s", MAX_REST_HEADERS_RESULTS, path[0]));
+        return RESTERR(req, HTTP_BAD_REQUEST, strprintf("Header count is invalid or out of acceptable range (1-%u): %s", MAX_REST_HEADERS_RESULTS, raw_count));
     }
 
-    std::string hashStr = path[1];
     uint256 hash;
     if (!ParseHashStr(hashStr, hash))
         return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + hashStr);
@@ -354,13 +364,28 @@ static bool rest_filter_header(const std::any& context, HTTPRequest* req, const
 
     std::vector<std::string> uri_parts;
     boost::split(uri_parts, param, boost::is_any_of("/"));
-    if (uri_parts.size() != 3) {
-        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid URI format. Expected /rest/blockfilterheaders/<filtertype>/<count>/<blockhash>");
+    std::string raw_count;
+    std::string raw_blockhash;
+    if (uri_parts.size() == 3) {
+        // deprecated path: /rest/blockfilterheaders/<filtertype>/<count>/<blockhash>
+        raw_blockhash = uri_parts[2];
+        raw_count = uri_parts[1];
+    } else if (uri_parts.size() == 2) {
+        // new path with query parameter: /rest/blockfilterheaders/<filtertype>/<blockhash>?count=<count>
+        raw_blockhash = uri_parts[1];
+        raw_count = req->GetQueryParameter("count").value_or("5");
+    } else {
+        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid URI format. Expected /rest/blockfilterheaders/<filtertype>/<blockhash>.<ext>?count=<count>");
+    }
+
+    const auto parsed_count{ToIntegral<size_t>(raw_count)};
+    if (!parsed_count.has_value() || *parsed_count < 1 || *parsed_count > MAX_REST_HEADERS_RESULTS) {
+        return RESTERR(req, HTTP_BAD_REQUEST, strprintf("Header count is invalid or out of acceptable range (1-%u): %s", MAX_REST_HEADERS_RESULTS, raw_count));
     }
 
     uint256 block_hash;
-    if (!ParseHashStr(uri_parts[2], block_hash)) {
-        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + uri_parts[2]);
+    if (!ParseHashStr(raw_blockhash, block_hash)) {
+        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + raw_blockhash);
     }
 
     BlockFilterType filtertype;
@@ -373,11 +398,6 @@ static bool rest_filter_header(const std::any& context, HTTPRequest* req, const
         return RESTERR(req, HTTP_BAD_REQUEST, "Index is not enabled for filtertype " + uri_parts[0]);
     }
 
-    const auto parsed_count{ToIntegral<size_t>(uri_parts[1])};
-    if (!parsed_count.has_value() || *parsed_count < 1 || *parsed_count > MAX_REST_HEADERS_RESULTS) {
-        return RESTERR(req, HTTP_BAD_REQUEST, strprintf("Header count is invalid or out of acceptable range (1-%u): %s", MAX_REST_HEADERS_RESULTS, uri_parts[1]));
-    }
-
     std::vector<const CBlockIndex*> headers;
     headers.reserve(*parsed_count);
     {