Fetch repository pull requests with the specified base branch

2 files changed, 198 insertions, 16 deletions

diff --git a/mod/mod-ci-github-gq.cxx b/mod/mod-ci-github-gq.cxx
index 5979511..26b4c1f 100644
--- a/mod/mod-ci-github-gq.cxx
+++ b/mod/mod-ci-github-gq.cxx
@@ -693,22 +693,192 @@ namespace brep
     return nullopt;
   }
 
-  // bool
-  // gq_fetch_branch_open_pull_requests ()
-  // {
-  //   // query {
-  //   //   repository(owner:"francoisk" name:"libb2")
-  //   //   {
-  //   //     pullRequests (last:100 states:OPEN baseRefName:"master") {
-  //   //       edges {
-  //   //         node {
-  //   //           id
-  //   //         }
-  //   //       }
-  //   //     }
-  //   //   }
-  //   // }
-  // }
+  // Serialize a GraphQL query that fetches the last 100 (the maximum per
+  // page) open pull requests with the specified base branch from the
+  // repository with the specified node ID.
+  //
+  // @@ TMP Should we support more than 100?
+  //
+  // Example query:
+  //
+  //   query {
+  //     node(id:"R_kgDOLc8CoA")
+  //     {
+  //       ... on Repository {
+  //         pullRequests (last:100 states:OPEN baseRefName:"master") {
+  //           edges {
+  //             node {
+  //               id
+  //               number
+  //               headRefOid
+  //             }
+  //           }
+  //         }
+  //       }
+  //     }
+  //   }
+  //
+  static string
+  gq_query_fetch_open_pull_requests (const string& rid, const string& br)
+  {
+    ostringstream os;
+
+    os << "query {"                                              << '\n'
+       << "  node(id:" << gq_str (rid) << ") {"                  << '\n'
+       << "    ... on Repository {"                              << '\n'
+       << "      pullRequests (last:100"                         << '\n'
+       << "                    states:" << gq_enum ("OPEN")      << '\n'
+       << "                    baseRefName:" << gq_str (br)      << '\n'
+       << "                   ) {"                               << '\n'
+       << "        totalCount"                                   << '\n'
+       << "        edges { node { id number headRefOid } }"      << '\n'
+       << "      }"                                              << '\n'
+       << "    }"                                                << '\n'
+       << "  }"                                                  << '\n'
+       << "}"                                                    << '\n';
+
+    return os.str ();
+  }
+
+  optional<vector<gh_pull_request>>
+  gq_fetch_open_pull_requests (const basic_mark& error,
+                               const string& iat,
+                               const string& nid,
+                               const string& br)
+  {
+    string rq (
+      gq_serialize_request (gq_query_fetch_open_pull_requests (nid, br)));
+
+    try
+    {
+      // Response parser.
+      //
+      // Example response (only the part we need to parse here):
+      //
+      //   {
+      //     "node": {
+      //       "pullRequests": {
+      //         "totalCount": 2,
+      //         "edges": [
+      //           {
+      //             "node": {
+      //               "id": "PR_kwDOLc8CoM5vRS0y",
+      //               "number": 7,
+      //               "headRefOid": "cf72888be9484d6946a1340264e7abf18d31cc92"
+      //             }
+      //           },
+      //           {
+      //             "node": {
+      //               "id": "PR_kwDOLc8CoM5vRzHs",
+      //               "number": 8,
+      //               "headRefOid": "626d25b318aad27bc0005277afefe3e8d6b2d434"
+      //             }
+      //           }
+      //         ]
+      //       }
+      //     }
+      //   }
+      //
+      struct resp
+      {
+        bool found = false;
+
+        vector<gh_pull_request> pull_requests;
+
+        resp (json::parser& p)
+        {
+          using event = json::event;
+
+          gq_parse_response (p, [this] (json::parser& p)
+          {
+            p.next_expect (event::begin_object);
+
+            if (p.next_expect_member_object_null ("node"))
+            {
+              found = true;
+
+              p.next_expect_member_object ("pullRequests");
+
+              uint16_t n (p.next_expect_member_number<uint16_t> ("totalCount"));
+
+              p.next_expect_member_array ("edges");
+              for (size_t i (0); i != n; ++i)
+              {
+                p.next_expect (event::begin_object); // edges[i]
+
+                p.next_expect_member_object ("node");
+                {
+                  gh_pull_request pr;
+                  pr.node_id = p.next_expect_member_string ("id");
+                  pr.number = p.next_expect_member_number<unsigned int> ("number");
+                  pr.head_sha = p.next_expect_member_string ("headRefOid");
+                  pull_requests.push_back (move (pr));
+                }
+                p.next_expect (event::end_object); // node
+
+                p.next_expect (event::end_object); // edges[i]
+              }
+              p.next_expect (event::end_array); // edges
+
+              p.next_expect (event::end_object); // pullRequests
+              p.next_expect (event::end_object); // node
+            }
+
+            p.next_expect (event::end_object);
+          });
+        }
+
+        resp () = default;
+      } rs;
+
+      uint16_t sc (github_post (rs,
+                                "graphql", // API Endpoint.
+                                strings {"Authorization: Bearer " + iat},
+                                move (rq)));
+
+      if (sc == 200)
+      {
+        if (!rs.found)
+        {
+          error << "repository '" << nid << "' not found";
+
+          return nullopt;
+        }
+
+        return rs.pull_requests;
+      }
+      else
+        error << "failed to fetch repository pull requests: "
+              << "error HTTP response status " << sc;
+    }
+    catch (const json::invalid_json_input& e)
+    {
+      // Note: e.name is the GitHub API endpoint.
+      //
+      error << "malformed JSON in response from " << e.name << ", line: "
+            << e.line << ", column: " << e.column << ", byte offset: "
+            << e.position << ", error: " << e;
+    }
+    catch (const invalid_argument& e)
+    {
+      error << "malformed header(s) in response: " << e;
+    }
+    catch (const system_error& e)
+    {
+      error << "unable to fetch repository pull requests (errno=" << e.code ()
+            << "): " << e.what ();
+    }
+    catch (const runtime_error& e) // From response type's parsing constructor.
+    {
+      // GitHub response contained error(s) (could be ours or theirs at this
+      // point).
+      //
+      error << "unable to fetch repository pull requests: " << e;
+    }
+
+    return nullopt;
+  }
+
 
   // GraphQL serialization functions.
   //
diff --git a/mod/mod-ci-github-gq.hxx b/mod/mod-ci-github-gq.hxx
index 9721b6e..439f7b7 100644
--- a/mod/mod-ci-github-gq.hxx
+++ b/mod/mod-ci-github-gq.hxx
@@ -116,6 +116,18 @@ namespace brep
   gq_pull_request_mergeable (const basic_mark& error,
                              const string& installation_access_token,
                              const string& node_id);
+
+  // Fetch the last 100 open pull requests with the specified base branch from
+  // the repository with the specified node ID.
+  //
+  // Issue diagnostics and return nullopt if the repository was not found or
+  // an error occurred.
+  //
+  optional<vector<gh_pull_request>>
+  gq_fetch_open_pull_requests (const basic_mark& error,
+                               const string& installation_access_token,
+                               const string& repository_node_id,
+                               const string& base_branch);
 }
 
 #endif // MOD_MOD_CI_GITHUB_GQ_HXX