move biomes definition to a json file

src/world/generator/GeneratorDef.cpp

@@ -1,6 +1,9 @@
 #include "GeneratorDef.hpp"
 
 #include "VoxelFragment.hpp"
+#include "content/Content.hpp"
+#include "util/stringutil.hpp"
+#include "voxels/Block.hpp"
 
 GeneratingVoxelStructure::GeneratingVoxelStructure(
     VoxelStructureMeta meta,
@@ -9,3 +12,25 @@ GeneratingVoxelStructure::GeneratingVoxelStructure(
 
 
 GeneratorDef::GeneratorDef(std::string name) : name(std::move(name)) {}
+
+void GeneratorDef::prepare(const Content* content) {
+    for (auto& biome : biomes) {
+        for (auto& layer : biome.groundLayers.layers) {
+            layer.rt.id = content->blocks.require(layer.block).rt.id;
+        }
+        for (auto& layer : biome.seaLayers.layers) {
+            layer.rt.id = content->blocks.require(layer.block).rt.id;
+        }
+        for (auto& plant : biome.plants.entries) {
+            plant.rt.id = content->blocks.require(plant.name).rt.id;
+        }
+        for (auto& structure : biome.structures.entries) {
+            const auto& found = structuresIndices.find(structure.name);
+            if (found == structuresIndices.end()) {
+                throw std::runtime_error(
+                    "no structure "+util::quote(structure.name)+" found");
+            }
+            structure.rt.id = found->second;
+        }
+    }
+}