Replace levenshtein with ruby implementation

Author: mikefranken

Gemfile

@@ -1,5 +1,4 @@
 source 'http://rubygems.org'
-gem "levenshtein-ffi", git: "https://github.com/zilverline/levenshtein-ffi.git"
 gemspec
 
 group :development, :test do

Gemfile.lock

@@ -4,7 +4,6 @@ PATH
     ups-ruby (0.17.1)
       excon (~> 0.45, >= 0.45.3)
       insensitive_hash (~> 0.3.3)
-      levenshtein-ffi (~> 1.1)
       ox (~> 2.2, >= 2.2.0)
 
 GEM
@@ -15,12 +14,9 @@ GEM
       simplecov (<= 0.13)
     docile (1.1.5)
     excon (0.110.0)
-    ffi (1.16.3)
     insensitive_hash (0.3.3)
     json (2.7.2)
     language_server-protocol (3.17.0.3)
-    levenshtein-ffi (1.1.0)
-      ffi (~> 1.9)
     minitest (5.22.3)
     ox (2.14.18)
     parallel (1.24.0)

lib/levenshtein.rb

@@ -0,0 +1,28 @@
+def levenshtein_distance(str1, str2)
+  # Create a 2D array to hold distances
+  rows = str1.length + 1
+  cols = str2.length + 1
+  dp = Array.new(rows) { Array.new(cols, 0) }
+
+  # Initialize base cases
+  (0...rows).each { |i| dp[i][0] = i }
+  (0...cols).each { |j| dp[0][j] = j }
+
+  # Fill the matrix
+  (1...rows).each do |i|
+    (1...cols).each do |j|
+      if str1[i - 1] == str2[j - 1]
+        dp[i][j] = dp[i - 1][j - 1] # No cost if characters are the same
+      else
+        dp[i][j] = [
+          dp[i - 1][j],    # Deletion
+          dp[i][j - 1],    # Insertion
+          dp[i - 1][j - 1] # Substitution
+        ].min + 1
+      end
+    end
+  end
+
+  # The bottom-right cell contains the result
+  dp[rows - 1][cols - 1]
+end

lib/ups/data.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-
 require 'levenshtein'
 
 module UPS
@@ -33,7 +32,7 @@ def ie_state_matcher(match_string)
 
         normalized_string = ie_state_normalizer string_normalizer match_string
         counties_with_distances = IE_COUNTIES.map do |county|
-          [county, Levenshtein.distance(county.downcase, normalized_string)]
+          [county, levenshtein_distance(county.downcase, normalized_string)]
         end
         counties_with_distances_hash = Hash[*counties_with_distances.flatten]
         counties_with_distances_hash.min_by { |_k, v| v }[0]