From 9895655a8ab78c2c92e1e2f7d8b7c6c196157a20 Mon Sep 17 00:00:00 2001
From: Luis Lavena <luislavena@gmail.com>
Date: Sun, 12 Mar 2017 12:36:05 -0300
Subject: [PATCH] Fix incorrect lookup on non-shared partial keys

Given the following nodes in a tree:

    # ( 8) /product
    # ( 4)         /new
    # ( 1)         s
    tree = Radix::Tree(Symbol).new
    tree.add "/products", :products
    tree.add "/product/new", :product_new

It failed to properly identify `/products` during lookup:

    result = tree.find "/products"
    result.found? # => false

Caused by incorrect comparsion of `s` remaining path against `/new`
node instead of continue comparison with the next one.

Fixes #21
---
 CHANGELOG.md            |  2 ++
 spec/radix/tree_spec.cr | 11 +++++++++++
 src/radix/tree.cr       |  6 ++++++
 3 files changed, 19 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8976356..cc2579b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,8 @@ This project aims to comply with [Semantic Versioning](http://semver.org/),
 so please check *Changed* and *Removed* notes before upgrading.
 
 ## [Unreleased]
+### Fixed
+- Correct lookup issue caused by incorrect comparison of shared key [#21](https://github.com/luislavena/radix/issues/21)
 
 ## [0.3.7] - 2017-02-04
 ### Fixed
diff --git a/spec/radix/tree_spec.cr b/spec/radix/tree_spec.cr
index 4c8ce04..3f100a7 100644
--- a/spec/radix/tree_spec.cr
+++ b/spec/radix/tree_spec.cr
@@ -323,6 +323,17 @@ module Radix
           result.payload.should eq(:abc)
         end
 
+        it "finds matching path across separator" do
+          tree = Tree(Symbol).new
+          tree.add "/products", :products
+          tree.add "/product/new", :product_new
+
+          result = tree.find("/products")
+          result.found?.should be_true
+          result.key.should eq("/products")
+          result.payload.should eq(:products)
+        end
+
         it "finds matching path across parents" do
           tree = Tree(Symbol).new
           tree.add "/", :root
diff --git a/src/radix/tree.cr b/src/radix/tree.cr
index 49d910b..f65cb54 100644
--- a/src/radix/tree.cr
+++ b/src/radix/tree.cr
@@ -432,11 +432,17 @@ module Radix
     # _shared_key?("foo", "bar")         # => false (mismatch at 1st character)
     # _shared_key?("foo/bar", "foo/baz") # => true (only `foo` is compared)
     # _shared_key?("zipcode", "zip")     # => true (only `zip` is compared)
+    # _shared_key?("s", "/new")          # => false (1st character is a separator)
     # ```
     private def _shared_key?(path, key)
       path_reader = Char::Reader.new(path)
       key_reader = Char::Reader.new(key)
 
+      if (path_reader.current_char != key_reader.current_char) &&
+         _check_markers(key_reader.current_char)
+        return false
+      end
+
       different = false
 
       while (path_reader.has_next? && !_check_markers(path_reader.current_char)) &&