//===-- ASTStructExtractor.h ------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef liblldb_ASTStructExtractor_h_
#define liblldb_ASTStructExtractor_h_

#include "ClangExpressionVariable.h"
#include "ClangFunctionCaller.h"

#include "clang/Sema/SemaConsumer.h"
#include "lldb/Core/ClangForward.h"

namespace lldb_private {
    
//----------------------------------------------------------------------
/// @class ASTStructExtractor ASTStructExtractor.h "lldb/Expression/ASTStructExtractor.h"
/// @brief Extracts and describes the argument structure for a wrapped function.
///
/// This pass integrates with ClangFunctionCaller, which calls functions with custom
/// sets of arguments.  To avoid having to implement the full calling convention
/// for the target's architecture, ClangFunctionCaller writes a simple wrapper
/// function that takes a pointer to an argument structure that contains room
/// for the address of the function to be called, the values of all its
/// arguments, and room for the function's return value.
///
/// The definition of this struct is itself in the body of the wrapper function,
/// so Clang does the structure layout itself.  ASTStructExtractor reads through
/// the AST for the wrapper function and finds the struct.
//----------------------------------------------------------------------
class ASTStructExtractor : public clang::SemaConsumer
{
public:
    //----------------------------------------------------------------------
    /// Constructor
    ///
    /// @param[in] passthrough
    ///     Since the ASTs must typically go through to the Clang code generator
    ///     in order to produce LLVM IR, this SemaConsumer must allow them to
    ///     pass to the next step in the chain after processing.  Passthrough is
    ///     the next ASTConsumer, or NULL if none is required.
    ///
    /// @param[in] struct_name
    ///     The name of the structure to extract from the wrapper function.
    ///
    /// @param[in] function
    ///     The caller object whose members should be populated with information
    ///     about the argument struct.  ClangFunctionCaller friends ASTStructExtractor
    ///     for this purpose.
    //----------------------------------------------------------------------
    ASTStructExtractor(clang::ASTConsumer *passthrough,
                       const char *struct_name,
                       ClangFunctionCaller &function);
    
    //----------------------------------------------------------------------
    /// Destructor
    //----------------------------------------------------------------------
    ~ASTStructExtractor() override;
    
    //----------------------------------------------------------------------
    /// Link this consumer with a particular AST context
    ///
    /// @param[in] Context
    ///     This AST context will be used for types and identifiers, and also
    ///     forwarded to the passthrough consumer, if one exists.
    //----------------------------------------------------------------------
    void Initialize(clang::ASTContext &Context) override;
    
    //----------------------------------------------------------------------
    /// Examine a list of Decls to find the function $__lldb_expr and 
    /// transform its code
    ///
    /// @param[in] D
    ///     The list of Decls to search.  These may contain LinkageSpecDecls,
    ///     which need to be searched recursively.  That job falls to
    ///     TransformTopLevelDecl.
    //----------------------------------------------------------------------
    bool HandleTopLevelDecl(clang::DeclGroupRef D) override;
    
    //----------------------------------------------------------------------
    /// Passthrough stub
    //----------------------------------------------------------------------
    void HandleTranslationUnit(clang::ASTContext &Ctx) override;
    
    //----------------------------------------------------------------------
    /// Passthrough stub
    //----------------------------------------------------------------------
    void HandleTagDeclDefinition(clang::TagDecl *D) override;
    
    //----------------------------------------------------------------------
    /// Passthrough stub
    //----------------------------------------------------------------------
    void CompleteTentativeDefinition(clang::VarDecl *D) override;
    
    //----------------------------------------------------------------------
    /// Passthrough stub
    //----------------------------------------------------------------------
    void HandleVTable(clang::CXXRecordDecl *RD) override;
    
    //----------------------------------------------------------------------
    /// Passthrough stub
    //----------------------------------------------------------------------
    void PrintStats() override;
    
    //----------------------------------------------------------------------
    /// Set the Sema object to use when performing transforms, and pass it on
    ///
    /// @param[in] S
    ///     The Sema to use.  Because Sema isn't externally visible, this class
    ///     casts it to an Action for actual use.
    //----------------------------------------------------------------------
    void InitializeSema(clang::Sema &S) override;
    
    //----------------------------------------------------------------------
    /// Reset the Sema to NULL now that transformations are done
    //----------------------------------------------------------------------
    void ForgetSema() override;

private:
    //----------------------------------------------------------------------
    /// Hunt the given FunctionDecl for the argument struct and place
    /// information about it into m_function
    ///
    /// @param[in] F
    ///     The FunctionDecl to hunt.
    //----------------------------------------------------------------------
    void
    ExtractFromFunctionDecl(clang::FunctionDecl* F);
    
    //----------------------------------------------------------------------
    /// Hunt the given Decl for FunctionDecls named the same as the wrapper
    /// function name, recursing as necessary through LinkageSpecDecls, and 
    /// calling ExtractFromFunctionDecl on anything that was found
    ///
    /// @param[in] D
    ///     The Decl to hunt.
    //----------------------------------------------------------------------
    void
    ExtractFromTopLevelDecl(clang::Decl* D);
    
    clang::ASTContext              *m_ast_context;          ///< The AST context to use for identifiers and types.
    clang::ASTConsumer             *m_passthrough;          ///< The ASTConsumer down the chain, for passthrough.  NULL if it's a SemaConsumer.
    clang::SemaConsumer            *m_passthrough_sema;     ///< The SemaConsumer down the chain, for passthrough.  NULL if it's an ASTConsumer.
    clang::Sema                    *m_sema;                 ///< The Sema to use.
    clang::Action                  *m_action;               ///< The Sema to use, cast to an Action so it's usable.
    
    ClangFunctionCaller            &m_function;             ///< The function to populate with information about the argument structure.
    std::string                     m_struct_name;          ///< The name of the structure to extract.
};
    
} // namespace lldb_private

#endif // liblldb_ASTStructExtractor_h_
