From b6c645260fca28d15814acee2a8793abfb169bd4 Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashikkbn@gmail.com>
Date: Mon, 23 Nov 2015 04:15:54 +0900
Subject: [PATCH] Invent Hamlit::StringInterpolation.compile

---
 lib/hamlit/compiler/script_compiler.rb   |  1 +
 lib/hamlit/string_interpolation.rb       | 60 ++++++++++++++++++++++++
 test/hamlit/string_interpolation_test.rb | 41 ++++++++++++++++
 3 files changed, 102 insertions(+)
 create mode 100644 lib/hamlit/string_interpolation.rb
 create mode 100644 test/hamlit/string_interpolation_test.rb

diff --git a/lib/hamlit/compiler/script_compiler.rb b/lib/hamlit/compiler/script_compiler.rb
index fa12c026..6b170342 100644
--- a/lib/hamlit/compiler/script_compiler.rb
+++ b/lib/hamlit/compiler/script_compiler.rb
@@ -1,4 +1,5 @@
 require 'hamlit/static_analyzer'
+require 'hamlit/string_interpolation'
 
 module Hamlit
   class Compiler
diff --git a/lib/hamlit/string_interpolation.rb b/lib/hamlit/string_interpolation.rb
new file mode 100644
index 00000000..b95d36a7
--- /dev/null
+++ b/lib/hamlit/string_interpolation.rb
@@ -0,0 +1,60 @@
+require 'ripper'
+
+module Hamlit::StringInterpolation
+  class << self
+    # `code` param must be valid string literal
+    def compile(code)
+      [].tap do |exps|
+        tokens = Ripper.lex(code.strip)
+
+        raise Hamlit::InternalError if tokens.size < 2
+        strip_quotes!(tokens)
+
+        compile_tokens!(exps, tokens)
+      end
+    end
+
+    private
+
+    def strip_quotes!(tokens)
+      _, type, _ = tokens.shift
+      raise Hamlit::InternalError if type != :on_tstring_beg
+
+      _, type, _ = tokens.pop
+      raise Hamlit::InternalError if type != :on_tstring_end
+    end
+
+    def compile_tokens!(exps, tokens)
+      until tokens.empty?
+        _, type, str = tokens.shift
+
+        case type
+        when :on_tstring_content
+          exps << [:static, str]
+        when :on_embexpr_beg
+          embedded = shift_balanced_embexpr(tokens)
+          exps << [:dynamic, embedded] unless embedded.empty?
+        end
+      end
+    end
+
+    def shift_balanced_embexpr(tokens)
+      String.new.tap do |embedded|
+        embexpr_open = 1
+
+        until tokens.empty?
+          _, type, str = tokens.shift
+          case type
+          when :on_embexpr_beg
+            embexpr_open += 1
+          when :on_embexpr_end
+            embexpr_open -= 1
+            break if embexpr_open == 0
+          end
+
+          embedded << str
+        end
+      end
+    end
+  end
+end
diff --git a/test/hamlit/string_interpolation_test.rb b/test/hamlit/string_interpolation_test.rb
new file mode 100644
index 00000000..fc6720b7
--- /dev/null
+++ b/test/hamlit/string_interpolation_test.rb
@@ -0,0 +1,41 @@
+describe Hamlit::StringInterpolation do
+  describe '.compile' do
+    def assert_compile(expected, code)
+      actual = Hamlit::StringInterpolation.compile(code)
+      assert_equal expected, actual
+    end
+
+    it { assert_compile([], %q|''|) }
+    it { assert_compile([], %q|""|) }
+    it { assert_compile([[:static, 'hello']], %q|"hello"|) }
+    it { assert_compile([[:static, 'hello '], [:static, 'world']], %q|"hello #{}world"|) }
+    it { assert_compile([[:dynamic, 'hello']], %q|"#{hello}"|) }
+    it { assert_compile([[:static, 'nya'], [:dynamic, '123']], %q|"nya#{123}"|) }
+    it { assert_compile([[:dynamic, '()'], [:static, '()']], %q|"#{()}()"|) }
+    it { assert_compile([[:static, ' '], [:dynamic, %q[ " #{ '#{}' } " ]]], %q|" #{ " #{ '#{}' } " }"|) }
+    it { assert_compile([[:static, 'a'], [:dynamic, 'b'], [:static, 'c'], [:dynamic, 'd'], [:static, 'e']], %q|%Q[a#{b}c#{d}e]|) }
+    it { assert_compile([[:static, 'a#{b}c#{d}e']], %q|%q[a#{b}c#{d}e]|) }
+    it { assert_compile([[:static, '\#{}'], [:dynamic, '123']], %q|"\#{}#{123}"|) }
+    it { assert_compile([[:dynamic, " '}' "]], %q|"#{ '}' }"|) }
+
+    describe 'invalid argument' do
+      it 'raises internal error' do
+        assert_raises Hamlit::InternalError do
+          Hamlit::StringInterpolation.compile('1')
+        end
+      end
+
+      it 'raises internal error' do
+        assert_raises Hamlit::InternalError do
+          Hamlit::StringInterpolation.compile('[]')
+        end
+      end
+
+      it 'raises internal error' do
+        assert_raises Hamlit::InternalError do
+          Hamlit::StringInterpolation.compile('"]')
+        end
+      end
+    end
+  end
+end