//===-- FunctionCaller.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_FunctionCaller_h_
#define liblldb_FunctionCaller_h_

// C Includes
// C++ Includes
#include <list>
#include <memory>
#include <string>
#include <vector>

// Other libraries and framework includes
// Project includes
#include "lldb/Core/Address.h"
#include "lldb/Core/Value.h"
#include "lldb/Expression/Expression.h"
#include "lldb/Expression/ExpressionParser.h"
#include "lldb/Symbol/CompilerType.h"

namespace lldb_private
{
    
//----------------------------------------------------------------------
/// @class FunctionCaller FunctionCaller.h "lldb/Expression/FunctionCaller.h"
/// @brief Encapsulates a function that can be called.
///
/// A given FunctionCaller object can handle a single function signature.
/// Once constructed, it can set up any number of concurrent calls to
/// functions with that signature.
///
/// It performs the call by synthesizing a structure that contains the pointer
/// to the function and the arguments that should be passed to that function,
/// and producing a special-purpose JIT-compiled function that accepts a void*
/// pointing to this struct as its only argument and calls the function in the 
/// struct with the written arguments.  This method lets Clang handle the
/// vagaries of function calling conventions.
///
/// The simplest use of the FunctionCaller is to construct it with a
/// function representative of the signature you want to use, then call
/// ExecuteFunction(ExecutionContext &, Stream &, Value &).
///
/// If you need to reuse the arguments for several calls, you can call
/// InsertFunction() followed by WriteFunctionArguments(), which will return
/// the location of the args struct for the wrapper function in args_addr_ref.
///
/// If you need to call the function on the thread plan stack, you can also 
/// call InsertFunction() followed by GetThreadPlanToCallFunction().
///
/// Any of the methods that take arg_addr_ptr or arg_addr_ref can be passed
/// a pointer set to LLDB_INVALID_ADDRESS and new structure will be allocated
/// and its address returned in that variable.
/// 
/// Any of the methods that take arg_addr_ptr can be passed nullptr, and the
/// argument space will be managed for you.
//----------------------------------------------------------------------    
class FunctionCaller : public Expression
{
public:
    //------------------------------------------------------------------
    /// Constructor
    ///
    /// @param[in] exe_scope
    ///     An execution context scope that gets us at least a target and 
    ///     process.
    ///
    /// @param[in] ast_context
    ///     The AST context to evaluate argument types in.
    ///
    /// @param[in] return_qualtype
    ///     An opaque Clang QualType for the function result.  Should be
    ///     defined in ast_context.
    ///
    /// @param[in] function_address
    ///     The address of the function to call.
    ///
    /// @param[in] arg_value_list
    ///     The default values to use when calling this function.  Can
    ///     be overridden using WriteFunctionArguments().
    //------------------------------------------------------------------
    FunctionCaller (ExecutionContextScope &exe_scope,
                   const CompilerType &return_type,
                   const Address& function_address, 
                   const ValueList &arg_value_list,
                   const char *name);
    
    //------------------------------------------------------------------
    /// Destructor
    //------------------------------------------------------------------
    ~FunctionCaller() override;

    //------------------------------------------------------------------
    /// Compile the wrapper function
    ///
    /// @param[in] errors
    ///     The stream to print parser errors to.
    ///
    /// @return
    ///     The number of errors.
    //------------------------------------------------------------------
    virtual unsigned
    CompileFunction (Stream &errors) = 0;
    
    //------------------------------------------------------------------
    /// Insert the default function wrapper and its default argument struct  
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in,out] args_addr_ref
    ///     The address of the structure to write the arguments into.  May
    ///     be LLDB_INVALID_ADDRESS; if it is, a new structure is allocated
    ///     and args_addr_ref is pointed to it.
    ///
    /// @param[in] errors
    ///     The stream to write errors to.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    bool
    InsertFunction (ExecutionContext &exe_ctx,
                    lldb::addr_t &args_addr_ref,
                    Stream &errors);

    //------------------------------------------------------------------
    /// Insert the default function wrapper (using the JIT)
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in] errors
    ///     The stream to write errors to.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    bool WriteFunctionWrapper (ExecutionContext &exe_ctx, 
                               Stream &errors);
    
    //------------------------------------------------------------------
    /// Insert the default function argument struct  
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in,out] args_addr_ref
    ///     The address of the structure to write the arguments into.  May
    ///     be LLDB_INVALID_ADDRESS; if it is, a new structure is allocated
    ///     and args_addr_ref is pointed to it.
    ///
    /// @param[in] errors
    ///     The stream to write errors to.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    bool WriteFunctionArguments (ExecutionContext &exe_ctx, 
                                 lldb::addr_t &args_addr_ref, 
                                 Stream &errors);
    
    //------------------------------------------------------------------
    /// Insert an argument struct with a non-default function address and
    /// non-default argument values
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in,out] args_addr_ref
    ///     The address of the structure to write the arguments into.  May
    ///     be LLDB_INVALID_ADDRESS; if it is, a new structure is allocated
    ///     and args_addr_ref is pointed at it.
    ///
    /// @param[in] arg_values
    ///     The values of the function's arguments.
    ///
    /// @param[in] errors
    ///     The stream to write errors to.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    bool WriteFunctionArguments (ExecutionContext &exe_ctx, 
                                 lldb::addr_t &args_addr_ref, 
                                 ValueList &arg_values,
                                 Stream &errors);

    //------------------------------------------------------------------
    /// Run the function this FunctionCaller was created with.
    ///
    /// This is the full version.
    ///
    /// @param[in] exe_ctx
    ///     The thread & process in which this function will run.
    ///
    /// @param[in] args_addr_ptr
    ///     If nullptr, the function will take care of allocating & deallocating the wrapper
    ///     args structure.  Otherwise, if set to LLDB_INVALID_ADDRESS, a new structure
    ///     will be allocated, filled and the address returned to you.  You are responsible
    ///     for deallocating it.  And if passed in with a value other than LLDB_INVALID_ADDRESS,
    ///     this should point to an already allocated structure with the values already written.
    ///
    /// @param[in] errors
    ///     Errors will be written here if there are any.
    ///
    /// @param[in] options
    ///     The options for this expression execution.
    ///
    /// @param[out] results
    ///     The result value will be put here after running the function.
    ///
    /// @return
    ///     Returns one of the ExpressionResults enum indicating function call status.
    //------------------------------------------------------------------
    lldb::ExpressionResults
    ExecuteFunction(ExecutionContext &exe_ctx, 
                    lldb::addr_t *args_addr_ptr, 
                    const EvaluateExpressionOptions &options,
                    Stream &errors,
                    Value &results);
    
    //------------------------------------------------------------------
    /// Get a thread plan to run the function this FunctionCaller was created with.
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in] func_addr
    ///     The address of the function in the target process.
    ///
    /// @param[in] args_addr
    ///     The address of the argument struct.
    ///
    /// @param[in] errors
    ///     The stream to write errors to.
    ///
    /// @param[in] stop_others
    ///     True if other threads should pause during execution.
    ///
    /// @param[in] unwind_on_error
    ///     True if the thread plan may simply be discarded if an error occurs.
    ///
    /// @return
    ///     A ThreadPlan shared pointer for executing the function.
    //------------------------------------------------------------------
    lldb::ThreadPlanSP
    GetThreadPlanToCallFunction (ExecutionContext &exe_ctx, 
                                 lldb::addr_t args_addr,
                                 const EvaluateExpressionOptions &options,
                                 Stream &errors);
    
    //------------------------------------------------------------------
    /// Get the result of the function from its struct
    ///
    /// @param[in] exe_ctx
    ///     The execution context to retrieve the result from.
    ///
    /// @param[in] args_addr
    ///     The address of the argument struct.
    ///
    /// @param[out] ret_value
    ///     The value returned by the function.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    bool FetchFunctionResults (ExecutionContext &exe_ctx, 
                               lldb::addr_t args_addr, 
                               Value &ret_value);
    
    //------------------------------------------------------------------
    /// Deallocate the arguments structure
    ///
    /// @param[in] exe_ctx
    ///     The execution context to insert the function and its arguments
    ///     into.
    ///
    /// @param[in] args_addr
    ///     The address of the argument struct.
    //------------------------------------------------------------------
    void DeallocateFunctionResults (ExecutionContext &exe_ctx, 
                                    lldb::addr_t args_addr);
    
    //------------------------------------------------------------------
    /// Interface for ClangExpression
    //------------------------------------------------------------------
    
    //------------------------------------------------------------------
    /// Return the string that the parser should parse.  Must be a full
    /// translation unit.
    //------------------------------------------------------------------
    const char *
    Text() override
    {
        return m_wrapper_function_text.c_str();
    }
    
    //------------------------------------------------------------------
    /// Return the function name that should be used for executing the
    /// expression.  Text() should contain the definition of this
    /// function.
    //------------------------------------------------------------------
    const char *
    FunctionName() override
    {
        return m_wrapper_function_name.c_str();
    }
    
    //------------------------------------------------------------------
    /// Return the object that the parser should use when registering
    /// local variables. May be nullptr if the Expression doesn't care.
    //------------------------------------------------------------------
    ExpressionVariableList *
    LocalVariables ()
    {
        return nullptr;
    }
    
    //------------------------------------------------------------------
    /// Return true if validation code should be inserted into the
    /// expression.
    //------------------------------------------------------------------
    bool
    NeedsValidation() override
    {
        return false;
    }
    
    //------------------------------------------------------------------
    /// Return true if external variables in the expression should be
    /// resolved.
    //------------------------------------------------------------------
    bool
    NeedsVariableResolution() override
    {
        return false;
    }
    
    ValueList
    GetArgumentValues () const
    {
        return m_arg_values;
    }

protected:
    // Note: the parser needs to be destructed before the execution unit, so
    // declare the execution unit first.
    std::shared_ptr<IRExecutionUnit> m_execution_unit_sp;
    std::unique_ptr<ExpressionParser> m_parser;                     ///< The parser responsible for compiling the function.
                                                                    ///< This will get made in CompileFunction, so it is
                                                                    ///< safe to access it after that.

    lldb::ModuleWP                  m_jit_module_wp;
    std::string                     m_name;                         ///< The name of this clang function - for debugging purposes.
    
    Function                       *m_function_ptr;                 ///< The function we're going to call. May be nullptr if we don't have debug info for the function.
    Address                         m_function_addr;                ///< If we don't have the FunctionSP, we at least need the address & return type.
    CompilerType                    m_function_return_type;         ///< The opaque clang qual type for the function return type.

    std::string                     m_wrapper_function_name;        ///< The name of the wrapper function.
    std::string                     m_wrapper_function_text;        ///< The contents of the wrapper function.
    std::string                     m_wrapper_struct_name;          ///< The name of the struct that contains the target function address, arguments, and result.
    std::list<lldb::addr_t>         m_wrapper_args_addrs;           ///< The addresses of the arguments to the wrapper function.
    
    bool                            m_struct_valid;                 ///< True if the ASTStructExtractor has populated the variables below.
    
    //------------------------------------------------------------------
    /// These values are populated by the ASTStructExtractor
    size_t                          m_struct_size;                  ///< The size of the argument struct, in bytes.
    std::vector<uint64_t>           m_member_offsets;               ///< The offset of each member in the struct, in bytes.
    uint64_t                        m_return_size;                  ///< The size of the result variable, in bytes.
    uint64_t                        m_return_offset;                ///< The offset of the result variable in the struct, in bytes.
    //------------------------------------------------------------------

    ValueList                       m_arg_values;                   ///< The default values of the arguments.
    
    bool                            m_compiled;                     ///< True if the wrapper function has already been parsed.
    bool                            m_JITted;                       ///< True if the wrapper function has already been JIT-compiled.
};

} // namespace lldb_private

#endif // liblldb_FunctionCaller_h_
