1 files changed, 109 insertions, 0 deletions
diff --git a/gems/ipynbdiff/lib/ipynb_diff/symbol_map.rb b/gems/ipynbdiff/lib/ipynb_diff/symbol_map.rb
new file mode 100644
index 00000000000..383f1de5c18
--- /dev/null
+++ b/gems/ipynbdiff/lib/ipynb_diff/symbol_map.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+module IpynbDiff
+  require 'oj'
+
+  # Creates a map from a symbol to the line number it appears in a Json file
+  #
+  # Example:
+  #
+  # Input:
+  #
+  # 1. {
+  # 2.   'obj1': [
+  # 3.     {
+  # 4.       'obj2': 5
+  # 5.     },
+  # 6.     3,
+  # 7.     {
+  # 8.       'obj3': {
+  # 9.         'obj4': 'b'
+  # 10.      }
+  # 11.    }
+  # 12.  ]
+  # 13.}
+  #
+  # Output:
+  #
+  # Symbol                Line Number
+  # .obj1              -> 2
+  # .obj1.0            -> 3
+  # .obj1.0            -> 3
+  # .obj1.0.obj2       -> 4
+  # .obj1.1            -> 6
+  # .obj1.2            -> 7
+  # .obj1.2.obj3       -> 8
+  # .obj1.2.obj3.obj4  -> 9
+  #
+  class SymbolMap
+    # rubocop:disable Lint/UnusedMethodArgument
+    class << self
+      def handler
+        @handler ||= SymbolMap.new
+      end
+
+      def parser
+        @parser ||= Oj::Parser.new(:saj).tap { |p| p.handler = handler }
+      end
+
+      def parse(notebook, *args)
+        handler.reset
+        parser.parse(notebook)
+        handler.symbols
+      end
+    end
+
+    attr_accessor :symbols
+
+    def hash_start(key, line, column)
+      add_symbol(key_or_index(key), line)
+    end
+
+    def hash_end(key, line, column)
+      @current_path.pop
+    end
+
+    def array_start(key, line, column)
+      @current_array_index << 0
+
+      add_symbol(key, line)
+    end
+
+    def array_end(key, line, column)
+      @current_path.pop
+      @current_array_index.pop
+    end
+
+    def add_value(value, key, line, column)
+      add_symbol(key_or_index(key), line)
+
+      @current_path.pop
+    end
+
+    def add_symbol(symbol, line)
+      @symbols[@current_path.append(symbol).join('.')] = line if symbol
+    end
+
+    def key_or_index(key)
+      if key.nil? # value in an array
+        if @current_path.empty?
+          @current_path = ['']
+          return
+        end
+
+        symbol = @current_array_index.last
+        @current_array_index[-1] += 1
+        symbol
+      else
+        key
+      end
+    end
+
+    def reset
+      @current_path = []
+      @symbols = {}
+      @current_array_index = []
+    end
+    # rubocop:enable Lint/UnusedMethodArgument
+  end
+end