/**
 * =========================================================================
 * File        : app_hooks.cpp
 * Project     : 0 A.D.
 * Description : hooks to allow customization / app-specific behavior.
 * =========================================================================
 */

// license: GPL; see lib/license.txt

#include "precompiled.h"
#include "app_hooks.h"

#include "lib/path_util.h"
#include "lib/sysdep/sysdep.h"


//-----------------------------------------------------------------------------
// default implementations
//-----------------------------------------------------------------------------

static void def_override_gl_upload_caps()
{
}


static const char* def_get_log_dir()
{
    static char N_log_dir[PATH_MAX];
    ONCE(\
        (void)sys_get_executable_name(N_log_dir, ARRAY_SIZE(N_log_dir));\
        /* strip app name (we only want its path) */\
        path_strip_fn(N_log_dir);\
    );
    return N_log_dir;
}


static void def_bundle_logs(FILE* UNUSED(f))
{
}


static const wchar_t* def_translate(const wchar_t* text)
{
    return text;
}


static void def_translate_free(const wchar_t* UNUSED(text))
{
    // no-op - translate() doesn't own the pointer.
}


static void def_log(const wchar_t* text)
{
    wprintf(text);
}


static ErrorReaction def_display_error(const wchar_t* UNUSED(text), uint UNUSED(flags))
{
    return ER_NOT_IMPLEMENTED;
}


//-----------------------------------------------------------------------------

// contains the current set of hooks. starts with the default values and
// may be changed via app_hooks_update.
//
// rationale: we don't ever need to switch "hook sets", so one global struct
// is fine. by always having one defined, we also avoid the trampolines
// having to check whether their function pointer is valid.
static AppHooks ah =
{
    def_override_gl_upload_caps,
    def_get_log_dir,
    def_bundle_logs,
    def_translate,
    def_translate_free,
    def_log,
    def_display_error
};

// separate copy of ah; used to determine if a particular hook has been
// redefined. the additional storage needed is negligible and this is
// easier than comparing each value against its corresponding def_ value.
static AppHooks default_ah = ah;

// register the specified hook function pointers. any of them that
// are non-zero override the previous function pointer value
// (these default to the stub hooks which are functional but basic).
void app_hooks_update(AppHooks* new_ah)
{
    debug_assert(new_ah);

#define OVERRIDE_IF_NONZERO(HOOKNAME) if(new_ah->HOOKNAME) ah.HOOKNAME = new_ah->HOOKNAME;
    OVERRIDE_IF_NONZERO(override_gl_upload_caps)
    OVERRIDE_IF_NONZERO(get_log_dir)
    OVERRIDE_IF_NONZERO(bundle_logs)
    OVERRIDE_IF_NONZERO(translate)
    OVERRIDE_IF_NONZERO(translate_free)
    OVERRIDE_IF_NONZERO(log)
    OVERRIDE_IF_NONZERO(display_error)
}

bool app_hook_was_redefined(size_t offset_in_struct)
{
    const u8* ah_bytes = (const u8*)&ah;
    const u8* default_ah_bytes = (const u8*)&default_ah;
    typedef void(*FP)();    // a bit safer than comparing void* pointers
    if(*(FP)(ah_bytes+offset_in_struct) != *(FP)(default_ah_bytes+offset_in_struct))
        return true;
    return false;
}


//-----------------------------------------------------------------------------
// trampoline implementations
// (boilerplate code; hides details of how to call the app hook)
//-----------------------------------------------------------------------------

void ah_override_gl_upload_caps(void)
{
    if(ah.override_gl_upload_caps)
        ah.override_gl_upload_caps();
}

const char* ah_get_log_dir(void)
{
    return ah.get_log_dir();
}

void ah_bundle_logs(FILE* f)
{
    ah.bundle_logs(f);
}

const wchar_t* ah_translate(const wchar_t* text)
{
    return ah.translate(text);
}

void ah_translate_free(const wchar_t* text)
{
    ah.translate_free(text);
}

void ah_log(const wchar_t* text)
{
    ah.log(text);
}

ErrorReaction ah_display_error(const wchar_t* text, uint flags)
{
    return ah.display_error(text, flags);
}