Make basic (unbalanced) insertion work.

src/vase/shard.cc

@@ -1,64 +1,49 @@
 #include "vase/shard.h"
 
-std::pair<ShardPtr, ShardPtr> split(Shard *n, uint32_t offset) {
+std::pair<ShardPtr, ShardPtr> split_shard(Shard *n, uint32_t offset) {
   if (!n)
     return {nullptr, nullptr};
-
   if (offset == 0)
     return {nullptr, ShardPtr(n)};
-
   if (offset == n->length)
     return {ShardPtr(n), nullptr};
 
   if (n->kind == Shard::ShardKind::Branch) {
-    Branch *b = static_cast<Branch *>(n);
+    Branch *b = (Branch *)n;
 
     if (offset < b->left.ptr->length) {
-      auto [a, b2] = split(b->left.ptr, offset);
-
-      return {
-        a,
-        ShardPtr(new Branch(
-          b2.ptr,
-          b->right.ptr
-        ))
-      };
+      auto [a, b2] = split_shard(b->left.ptr, offset);
+      return {a, ShardPtr(new Branch(b2.ptr, b->right.ptr))};
     } else {
-      auto [a, b2] = split(
-        b->right.ptr,
-        offset - b->left.ptr->length
-      );
-
-      return {
-        ShardPtr(new Branch(
-          b->left.ptr,
-          a.ptr
-        )),
-        b2
-      };
+      auto [a, b2] = split_shard(b->right.ptr, offset - b->left.ptr->length);
+      return {ShardPtr(new Branch(b->left.ptr, a.ptr)), b2};
     }
+  } else {
+    Petal *p = (Petal *)n;
+
+    auto left = new Petal(
+      offset,
+      p->source->count_lines(0, offset),
+      p->source,
+      p->pos
+    );
+    auto right = new Petal(
+      p->length - offset,
+      p->source->count_lines(offset, p->length),
+      p->source,
+      p->pos + offset
+    );
+
+    return {ShardPtr(left), ShardPtr(right)};
   }
+}
 
-  Petal *p = static_cast<Petal *>(n);
-
-  auto left = new Petal(
-    offset,
-    p->source->count_lines(0, offset),
-    p->source,
-    p->pos
-  );
-
-  auto right = new Petal(
-    p->length - offset,
-    p->source->count_lines(offset, p->length),
-    p->source,
-    p->pos + offset
-  );
-
-  return {
-    ShardPtr(left),
-    ShardPtr(right)
-  };
+ShardPtr concat_shard(ShardPtr left, ShardPtr right) {
+  if (!left.ptr)
+    return right;
+  if (!right.ptr)
+    return left;
+  return new Branch(left.ptr, right.ptr);
 }
 
 void print_shard(const Shard *shard, int depth) {
@@ -68,7 +53,6 @@ void print_shard(const Shard *shard, int depth) {
   }
 
   std::string indent(depth * 2, ' ');
-
   std::cout << indent;
 
   if (shard->kind == Shard::ShardKind::Branch) {