From 94f42f24c5a57ff37d116c90872fe9b3e9958834 Mon Sep 17 00:00:00 2001
From: Janis <janis@nirgendwo.xyz>
Date: Fri, 17 Mar 2023 20:08:51 +0100
Subject: [PATCH] insert with lookup

3rd lvl is broken
---
 src/main.zig | 120 ++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 91 insertions(+), 29 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index cce0a46..a7a8313 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -22,16 +22,26 @@ const BTree = struct {
         self.dbg();
 
         if (self.root) |*root| {
-            const result = try root.as_leaf().insert_value(value);
-            if (result) |split| {
-                // create new node which will replace self.
-                const parent = try Node.create(self.ally);
-                parent.leaf.level = split.left.level + 1;
-                parent.leaf.push_value(split.middle);
-                parent.insert_node(NodeOrLeaf.from_leaf(split.left));
-                parent.insert_node(NodeOrLeaf.from_leaf(split.right));
+            const search = root.find_key(value);
 
-                self.root = .{ .internal = parent };
+            switch (search) {
+                .Leaf => |node| {
+                    std.debug.print("key already present: {}", .{node});
+                    return error.Occupied;
+                },
+                .Edge => |edge| {
+                    const result = try edge.leaf.insert_value(value);
+                    if (result) |split| {
+                        // create new node which will replace self.
+                        const parent = try Node.create(self.ally);
+                        parent.leaf.level = split.left.level + 1;
+                        parent.leaf.push_value(split.middle);
+                        parent.insert_node(NodeOrLeaf.from_leaf(split.left));
+                        parent.insert_node(NodeOrLeaf.from_leaf(split.right));
+
+                        self.root = .{ .internal = parent };
+                    }
+                },
             }
         } else {
             var leaf: *Leaf = try self.ally.create(Leaf);
@@ -94,6 +104,32 @@ const BTree = struct {
             }
         }
 
+        fn find_key(self: NodeOrLeaf, key: u32) Leaf.SearchResult {
+            var leaf = self.as_leaf();
+            while (true) {
+                const search = leaf.find_key(key);
+
+                switch (search) {
+                    .Leaf => {
+                        return search;
+                    },
+                    .Edge => |edge| {
+                        const node = NodeOrLeaf.from_leaf(edge.leaf);
+                        switch (node) {
+                            .internal => |internal| {
+                                if (internal.get_edges()[edge.idx]) |child| {
+                                    leaf = child.as_leaf();
+                                    continue;
+                                }
+                            },
+                            .leaf => {},
+                        }
+                        return search;
+                    },
+                }
+            }
+        }
+
         fn dbg(self: NodeOrLeaf) void {
             switch (self) {
                 .internal => |node| {
@@ -237,11 +273,12 @@ const BTree = struct {
         }
 
         const SplitResult = struct {
-            // attached
+            // attached, old node that may be modified
             left: *Leaf,
             // lose value, previously attacked, must be inserted
+            // if we go all the way to the top, the root node must have some value and this is it
             middle: u32,
-            // free floating leaf, must be attached
+            // new, free floating leaf, must be attached
             right: *Leaf,
         };
 
@@ -254,36 +291,51 @@ const BTree = struct {
                 }
             }
 
-            std.debug.assert(idx > 0 and idx < CAPACITY - 1);
+            std.debug.assert(self.len == CAPACITY);
+            //std.debug.assert(idx > 0 and idx < CAPACITY - 1);
 
             var new = try Leaf.create(self.ally);
             new.level = self.level;
             var middle: u32 = undefined;
 
+            new.len = B - 1;
+            std.mem.copy(u32, &new.values, self.values[B..]);
+            middle = self.values[B - 1];
+            self.len = B - 1;
+
             // take from right half
-            if (idx > B) {
-                new.len = self.len - (idx + 1);
-                std.mem.copy(u32, &new.values, self.values[(idx + 1)..self.len]);
-
-                middle = self.values[idx];
-
-                self.len = idx;
-                self.push_value(value);
-            } else {
-                // take from left half
-                new.len = self.len - (idx);
-                std.mem.copy(u32, &new.values, self.values[idx..self.len]);
-
+            if (idx >= B) {
                 new.push_value(value);
-
-                middle = self.values[idx - 1];
-
-                self.len = idx - 1;
+            } else {
+                self.push_value(value);
             }
 
             return .{ .left = self, .middle = middle, .right = new };
         }
 
+        const SearchResultTag = enum { Edge, Leaf };
+
+        const SearchResult = union(SearchResultTag) {
+            Edge: struct { leaf: *Leaf, idx: u16 },
+            Leaf: struct { leaf: *Leaf, idx: u16 },
+        };
+
+        fn find_key(self: *Leaf, key: u32) SearchResult {
+            std.debug.print("looking for {} in {any}\n", .{ key, self.get_values() });
+            for (self.get_values(), 0..) |v, i| {
+                if (key < v) {
+                    std.debug.print("decending left of {}\n", .{v});
+                    return .{ .Edge = .{ .leaf = self, .idx = @intCast(u16, i) } };
+                } else if (key == v) {
+                    std.debug.print("located {} at {}\n", .{ key, v });
+                    return .{ .Leaf = .{ .leaf = self, .idx = @intCast(u16, i) } };
+                }
+            }
+
+            std.debug.print("decending right of {}\n", .{self.get_values()[self.len - 1]});
+            return .{ .Edge = .{ .leaf = self, .idx = self.len } };
+        }
+
         // returns null on success, or a split result which could not be merged
         // up because we are at the root node
         fn insert_value(self: *Leaf, value: u32) !?SplitResult {
@@ -394,6 +446,16 @@ test "btree insert" {
     try tree.insert(9);
     try tree.insert(8);
     tree.dbg();
+    try tree.insert(11);
+    tree.dbg();
+    try tree.insert(12);
+    try tree.insert(16);
+    tree.dbg();
+    try tree.insert(1);
+    try tree.insert(2);
+    try tree.insert(0);
+    try tree.insert(5);
+    tree.dbg();
 }
 
 test "btree new" {