Refactor GN source expansions.

tools/gn/substitution_writer.h

Index: tools/gn/substitution_writer.h
diff --git a/tools/gn/substitution_writer.h b/tools/gn/substitution_writer.h
new file mode 100644
index 0000000000000000000000000000000000000000..2bc9ed2aa86ebe3e41af2a6a9dd9e3f783ef7d9b
--- /dev/null
+++ b/tools/gn/substitution_writer.h
@@ -0,0 +1,107 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_GN_SUBSTITUTION_WRITER_H_
+#define TOOLS_GN_SUBSTITUTION_WRITER_H_
+
+#include <iosfwd>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "tools/gn/substitution_type.h"
+
+struct EscapeOptions;
+class OutputFile;
+class Settings;
+class SourceDir;
+class SourceFile;
+class SubstitutionList;
+class SubstitutionPattern;
+
+// Help text for script source expansion.
+extern const char kSourceExpansion_Help[];
+
+// This class handles writing or applying substitution patterns to strings.
+class SubstitutionWriter {
+ public:
+  enum OutputStyle {
+    OUTPUT_ABSOLUTE,  // Dirs will be absolute "//foo/bar".
+    OUTPUT_RELATIVE,  // Dirs will be relative to a given directory.
+  };
+
+  SubstitutionWriter();
+  ~SubstitutionWriter();
+
+  // Applies the substitution pattern to a source file, returning the result
+  // as either a SourceFile or OutputFile.
+  static SourceFile ApplyPatternToSource(
+      const Settings* settings,
+      const SubstitutionPattern& pattern,
+      const SourceFile& source);
+  static OutputFile ApplyPatternToSourceAsOutputFile(
+      const Settings* settings,
+      const SubstitutionPattern& pattern,
+      const SourceFile& source);
+
+  // Applies the substitution list to a source, APPENDING the result to the
+  // given output vector. It works this way so one can call multiple times to
+  // apply to multiple files and create a list. The result can either be
+  // SourceFiles or OutputFiles.
+  static void ApplyListToSource(
+      const Settings* settings,
+      const SubstitutionList& list,
+      const SourceFile& source,
+      std::vector<SourceFile>* output);
+  static void ApplyListToSourceAsOutputFile(
+      const Settings* settings,
+      const SubstitutionList& list,
+      const SourceFile& source,
+      std::vector<OutputFile>* output);
+
+  // Like ApplyListToSource but applies the list to all sources and replaces
+  // rather than appesnds the output (this produces the complete output).
+  static void ApplyListToSources(
+      const Settings* settings,
+      const SubstitutionList& list,
+      const std::vector<SourceFile>& sources,
+      std::vector<SourceFile>* output);
+  static void ApplyListToSourcesAsOutputFile(
+      const Settings* settings,
+      const SubstitutionList& list,
+      const std::vector<SourceFile>& sources,
+      std::vector<OutputFile>* output);
+
+  // Given a list of source replacement types used, writes the Ninja variable
+  // definitions for the given source file to use for those replacements. The
+  // variables will be indented two spaces. Since this is for writing to
+  // Ninja files, paths will be relative to the build dir, and no definition
+  // for {{source}} will be written since that maps to Ninja's implicit $in
+  // variable.
+  static void WriteNinjaVariablesForSource(
+      const Settings* settings,
+      const SourceFile& source,
+      const std::vector<SubstitutionType>& types,
+      const EscapeOptions& escape_options,
+      std::ostream& out);
+
+  // Writes the pattern to the given stream with no special handling, and with
+  // Ninja variables replacing the patterns.
+  static void WriteWithNinjaVariables(
+      const SubstitutionPattern& pattern,
+      const EscapeOptions& escape_options,
+      std::ostream& out);
+
+  // Extracts the given type of substitution related to a source file from the
+  // given source file. If output_style is OUTPUT_RELATIVE, relative_to
+  // indicates the directory that the relative directories should be relative
+  // to, otherwise it is ignored.
+  static std::string GetSourceSubstitution(
+      const Settings* settings,
+      const SourceFile& source,
+      SubstitutionType type,
+      OutputStyle output_style,
+      const SourceDir& relative_to);
+};
+
+#endif  // TOOLS_GN_SUBSTITUTION_WRITER_H_