Initial commit

src/sexpr.cr

@@ -0,0 +1,71 @@
+# Based on fast-sexpr (https://www.npmjs.com/package/fast-sexpr)
+
+module Sexpr
+  extend self
+
+  VERSION = {{ `shards version`.stringify.chomp }}
+
+  alias Node = String | Body
+  alias Body = Array(String) | Array(Node)
+
+  private class Wrapper
+    private property i = 0
+    private property source : String
+
+    private module Terms
+      STRING = /"/
+      SPACE  = /\s/
+      LIST   = /(#{SPACE})|[()]/
+    end
+
+    def initialize(@source : String)
+    end
+
+    private def get_char : Char?
+      if @i == @source.size
+        return nil
+      end
+
+      char = @source[@i]
+      @i += 1
+      char
+    end
+
+    private def read_value(is_terminator : Regex) : String
+      value = ""
+      while !is_terminator.matches?(strChar = get_char.to_s)
+        value += strChar
+      end
+
+      value
+    end
+
+    private def un_get_char
+      @i -= 1
+    end
+
+    def parse : Body
+      body = [] of Node
+
+      while char = get_char
+        if char == ')'
+          break
+        elsif char == '('
+          body << parse
+        elsif char == '"'
+          body << read_value(Terms::STRING)
+        elsif !Terms::SPACE.matches?(char.to_s)
+          un_get_char
+          body << read_value(Terms::LIST)
+          un_get_char
+        end
+      end
+
+      body
+    end
+  end
+
+  def parse(source : String) : Body
+    Wrapper.new(source).parse
+  end
+end