hardfork: add a get_ideal_version(uint64_t) function

It returns the ideal version for a given height, which is
based on the minimum height for a fork, disregarding votes

src/cryptonote_core/hardfork.cpp

@@ -337,6 +337,17 @@ uint8_t HardFork::get_ideal_version() const
   return heights.back().version;
 }
 
+uint8_t HardFork::get_ideal_version(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  for (unsigned int n = heights.size() - 1; n > 0; --n) {
+    if (height >= heights[n].height) {
+      return heights[n].version;
+    }
+  }
+  return original_version;
+}
+
 bool HardFork::get_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint8_t &voting) const
 {
   CRITICAL_REGION_LOCAL(lock);

src/cryptonote_core/hardfork.h

@@ -167,6 +167,13 @@ namespace cryptonote
      */
     uint8_t get_ideal_version() const;
 
+    /**
+     * @brief returns the "ideal" version for a given height
+     *
+     * @param height height of the block to check
+     */
+    uint8_t get_ideal_version(uint64_t height) const;
+
     /**
      * @brief returns the current version
      *

tests/unit_tests/hardfork.cpp

@@ -480,3 +480,25 @@ TEST(reorganize, changed)
     ASSERT_EQ(hf.get_current_version(), 2); // we did not bump to 3 this time
     ASSERT_EQ(hf.get_start_height(3), std::numeric_limits<uint64_t>::max()); // not yet
 }
+
+TEST(get, higher)
+{
+    TestDB db;
+    HardFork hf(db, 1, 0, 1, 1, 4, 50);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(2, 2, 1));
+    ASSERT_TRUE(hf.add(3, 5, 2));
+    hf.init();
+
+    ASSERT_EQ(hf.get_ideal_version(0), 1);
+    ASSERT_EQ(hf.get_ideal_version(1), 1);
+    ASSERT_EQ(hf.get_ideal_version(2), 2);
+    ASSERT_EQ(hf.get_ideal_version(3), 2);
+    ASSERT_EQ(hf.get_ideal_version(4), 2);
+    ASSERT_EQ(hf.get_ideal_version(5), 3);
+    ASSERT_EQ(hf.get_ideal_version(6), 3);
+    ASSERT_EQ(hf.get_ideal_version(7), 3);
+}
+