Introduce line editor library.

This library will be used by clang-query. I can imagine LLDB becoming another
client of this library, so I think LLVM is a sensible place for it to live.
It wraps libedit, and adds tab completion support.

The code is loosely based on the line editor bits in LLDB, with a few
improvements:

 - Polymorphism for retrieving the list of tab completions, based on
   the concept pattern from the new pass manager.

 - Tab completion doesn't corrupt terminal output if the input covers
   multiple lines. Unfortunately this can only be done in a truly horrible
   way, as far as I can tell. But since the alternative is to implement our
   own line editor (which I don't think LLVM should be in the business of
   doing, at least for now) I think it may be acceptable.

 - Includes a fallback for the case where the user doesn't have libedit
   installed.

Note that this uses C stdio, mainly because libedit also uses C stdio.

Differential Revision: http://llvm-reviews.chandlerc.com/D2200

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200595 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 158 insertions, 0 deletions

diff --git a/include/llvm/Config/config.h.cmake b/include/llvm/Config/config.h.cmake
index 5c72ad8a99..4a15197895 100644
--- a/include/llvm/Config/config.h.cmake
+++ b/include/llvm/Config/config.h.cmake
@@ -212,6 +212,9 @@
 /* Define to 1 if you have the 'z' library (-lz). */
 #cmakedefine HAVE_LIBZ ${HAVE_LIBZ}
 
+/* Define to 1 if you have the 'edit' library (-ledit). */
+#cmakedefine HAVE_LIBEDIT ${HAVE_LIBEDIT}
+
 /* Define to 1 if you have the <limits.h> header file. */
 #cmakedefine HAVE_LIMITS_H ${HAVE_LIMITS_H}
 
diff --git a/include/llvm/Config/config.h.in b/include/llvm/Config/config.h.in
index 0d43ae50a1..da5b6c9f64 100644
--- a/include/llvm/Config/config.h.in
+++ b/include/llvm/Config/config.h.in
@@ -205,6 +205,9 @@
 /* Define if you have the libdl library or equivalent. */
 #undef HAVE_LIBDL
 
+/* Define if libedit is available on this platform. */
+#undef HAVE_LIBEDIT
+
 /* Define to 1 if you have the `imagehlp' library (-limagehlp). */
 #undef HAVE_LIBIMAGEHLP
 
diff --git a/include/llvm/LineEditor/LineEditor.h b/include/llvm/LineEditor/LineEditor.h
new file mode 100644
index 0000000000..7ac9b57323
--- /dev/null
+++ b/include/llvm/LineEditor/LineEditor.h
@@ -0,0 +1,152 @@
+//===-- llvm/LineEditor/LineEditor.h - line editor --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LINEEDITOR_LINEEDITOR_H
+#define LLVM_LINEEDITOR_LINEEDITOR_H
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/OwningPtr.h"
+#include <stdio.h>
+#include <string>
+#include <vector>
+
+namespace llvm {
+
+class LineEditor {
+public:
+  /// Create a LineEditor object.
+  ///
+  /// \param ProgName The name of the current program. Used to form a default
+  /// prompt.
+  /// \param HistoryPath Path to the file in which to store history data, if
+  /// possible.
+  /// \param In The input stream used by the editor.
+  /// \param Out The output stream used by the editor.
+  /// \param Err The error stream used by the editor.
+  LineEditor(StringRef ProgName, StringRef HistoryPath = "", FILE *In = stdin,
+             FILE *Out = stdout, FILE *Err = stderr);
+  ~LineEditor();
+
+  /// Reads a line.
+  ///
+  /// \return The line, or llvm::Optional<std::string>() on EOF.
+  llvm::Optional<std::string> readLine() const;
+
+  void saveHistory();
+  void loadHistory();
+
+  static std::string getDefaultHistoryPath(StringRef ProgName);
+
+  /// The action to perform upon a completion request.
+  struct CompletionAction {
+    enum ActionKind {
+      /// Insert Text at the cursor position.
+      AK_Insert,
+      /// Show Completions, or beep if the list is empty.
+      AK_ShowCompletions
+    };
+
+    ActionKind Kind;
+
+    /// The text to insert.
+    std::string Text;
+
+    /// The list of completions to show.
+    std::vector<std::string> Completions;
+  };
+
+  /// A possible completion at a given cursor position.
+  struct Completion {
+    Completion() {}
+    Completion(const std::string &TypedText, const std::string &DisplayText)
+        : TypedText(TypedText), DisplayText(DisplayText) {}
+
+    /// The text to insert. If the user has already input some of the
+    /// completion, this should only include the rest of the text.
+    std::string TypedText;
+
+    /// A description of this completion. This may be the completion itself, or
+    /// maybe a summary of its type or arguments.
+    std::string DisplayText;
+  };
+
+  /// Set the completer for this LineEditor. A completer is a function object
+  /// which takes arguments of type StringRef (the string to complete) and
+  /// size_t (the zero-based cursor position in the StringRef) and returns a
+  /// CompletionAction.
+  template <typename T> void setCompleter(T Comp) {
+    Completer.reset(new CompleterModel<T>(Comp));
+  }
+
+  /// Set the completer for this LineEditor to the given list completer.
+  /// A list completer is a function object which takes arguments of type
+  /// StringRef (the string to complete) and size_t (the zero-based cursor
+  /// position in the StringRef) and returns a std::vector<Completion>.
+  template <typename T> void setListCompleter(T Comp) {
+    Completer.reset(new ListCompleterModel<T>(Comp));
+  }
+
+  /// Use the current completer to produce a CompletionAction for the given
+  /// completion request. If the current completer is a list completer, this
+  /// will return an AK_Insert CompletionAction if each completion has a common
+  /// prefix, or an AK_ShowCompletions CompletionAction otherwise.
+  ///
+  /// \param Buffer The string to complete
+  /// \param Pos The zero-based cursor position in the StringRef
+  CompletionAction getCompletionAction(StringRef Buffer, size_t Pos) const;
+
+  const std::string &getPrompt() const { return Prompt; }
+  void setPrompt(const std::string &P) { Prompt = P; }
+
+  // Public so callbacks in LineEditor.cpp can use it.
+  struct InternalData;
+
+private:
+  std::string Prompt;
+  std::string HistoryPath;
+  OwningPtr<InternalData> Data;
+
+  struct CompleterConcept {
+    virtual ~CompleterConcept();
+    virtual CompletionAction complete(StringRef Buffer, size_t Pos) const = 0;
+  };
+
+  struct ListCompleterConcept : CompleterConcept {
+    ~ListCompleterConcept();
+    CompletionAction complete(StringRef Buffer, size_t Pos) const;
+    static std::string getCommonPrefix(const std::vector<Completion> &Comps);
+    virtual std::vector<Completion> getCompletions(StringRef Buffer,
+                                                   size_t Pos) const = 0;
+  };
+
+  template <typename T>
+  struct CompleterModel : CompleterConcept {
+    CompleterModel(T Value) : Value(Value) {}
+    CompletionAction complete(StringRef Buffer, size_t Pos) const {
+      return Value(Buffer, Pos);
+    }
+    T Value;
+  };
+
+  template <typename T>
+  struct ListCompleterModel : ListCompleterConcept {
+    ListCompleterModel(T Value) : Value(Value) {}
+    std::vector<Completion> getCompletions(StringRef Buffer, size_t Pos) const {
+      return Value(Buffer, Pos);
+    }
+    T Value;
+  };
+
+  llvm::OwningPtr<const CompleterConcept> Completer;
+};
+
+}
+
+#endif