/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/

#include "stdafx.h"
#include "PyInt.h"

#include "Globals.h"
#include "application.h"
#include "renderer.h"
#include "Logs.h"

void render_task::run() {
    // call the renderer
    auto *output { PyObject_CallMethod( m_renderer, "render", "O", m_input ) };
    Py_DECREF( m_input );

    if( output != nullptr ) {
        auto *outputwidth { PyObject_CallMethod( m_renderer, "get_width", nullptr ) };
        auto *outputheight { PyObject_CallMethod( m_renderer, "get_height", nullptr ) };
        // upload texture data
        if( ( outputwidth != nullptr )
         && ( outputheight != nullptr ) ) {

            ::glBindTexture( GL_TEXTURE_2D, m_target );
            // setup texture parameters
            ::glTexParameteri( GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE );
            ::glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
            ::glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
            if( GLEW_EXT_texture_filter_anisotropic ) {
                // anisotropic filtering
                ::glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, Global.AnisotropicFiltering );
            }
            // build texture
            ::glTexImage2D(
                GL_TEXTURE_2D, 0,
                GL_RGBA8,
                PyInt_AsLong( outputwidth ), PyInt_AsLong( outputheight ), 0,
                GL_RGB, GL_UNSIGNED_BYTE, reinterpret_cast<GLubyte const *>( PyString_AsString( output ) ) );
            ::glFlush();
        }
        if( outputheight != nullptr ) { Py_DECREF( outputheight ); }
        if( outputwidth  != nullptr ) { Py_DECREF( outputwidth ); }
        Py_DECREF( output );
    }
    // clean up after yourself
    delete this;
}

void render_task::cancel() {

    Py_DECREF( m_input );
    delete this;
}

// initializes the module. returns true on success
auto python_taskqueue::init() -> bool {

#ifdef _WIN32
	if (sizeof(void*) == 8)
		Py_SetPythonHome("python64");
	else
		Py_SetPythonHome("python");
#elif __linux__
	if (sizeof(void*) == 8)
		Py_SetPythonHome("linuxpython64");
	else
		Py_SetPythonHome("linuxpython");
#endif
    Py_Initialize();
    PyEval_InitThreads();
    // do the setup work while we hold the lock
    m_main = PyImport_ImportModule("__main__");
    if (m_main == nullptr) {
        ErrorLog( "Python Interpreter: __main__ module is missing" );
        goto release_and_exit;
    }

    auto *stringiomodule { PyImport_ImportModule( "cStringIO" ) };
    auto *stringioclassname { (
        stringiomodule != nullptr ?
            PyObject_GetAttrString( stringiomodule, "StringIO" ) :
            nullptr ) };
    auto *stringioobject { (
        stringioclassname != nullptr ?
            PyObject_CallObject( stringioclassname, nullptr ) :
            nullptr ) };
    m_error = { (
        stringioobject == nullptr ? nullptr :
        PySys_SetObject( "stderr", stringioobject ) != 0 ? nullptr :
        stringioobject ) };

    if( m_error == nullptr ) { goto release_and_exit; }

    if( false == run_file( "abstractscreenrenderer" ) ) { goto release_and_exit; }

    // release the lock, save the state for future use
    m_mainthread = PyEval_SaveThread();

    WriteLog( "Python Interpreter setup complete" );

    // init workers
    for( auto &worker : m_workers ) {

        auto *openglcontextwindow { Application.window( -1 ) };
        worker = std::thread(
                    &python_taskqueue::run, this,
                    openglcontextwindow, std::ref( m_tasks ), std::ref( m_condition ), std::ref( m_exit ) );

        if( false == worker.joinable() ) { return false; }
    }

    return true;

release_and_exit:
    PyEval_ReleaseLock();
    return false;
}

// shuts down the module
void python_taskqueue::exit() {
    // let the workers know we're done with them
    m_exit = true;
    m_condition.notify_all();
    // let them free up their shit before we proceed
    for( auto &worker : m_workers ) {
        worker.join();
    }
    // get rid of the leftover tasks
    // with the workers dead we don't have to worry about concurrent access anymore
    for( auto *task : m_tasks.data ) {
        task->cancel();
    }
    // take a bow
    acquire_lock();
    Py_Finalize();
}

// adds specified task along with provided collection of data to the work queue. returns true on success
auto python_taskqueue::insert( task_request const &Task ) -> bool {

    if( ( Task.renderer.empty() )
     || ( Task.input == nullptr )
     || ( Task.target == 0 ) ) { return false; }

    auto *renderer { fetch_renderer( Task.renderer ) };
    if( renderer == nullptr ) { return false; }

    auto *newtask { new render_task( renderer, Task.input, Task.target ) };
    bool newtaskinserted { false };
    // acquire a lock on the task queue and add the new task
    {
        std::lock_guard<std::mutex> lock( m_tasks.mutex );
        // check the task list for a pending request with the same target
        for( auto &task : m_tasks.data ) {
            if( task->target() == Task.target ) {
                // replace pending task in the slot with the more recent one
                acquire_lock();
                {
                    task->cancel();
                }
                release_lock();
                task = newtask;
                newtaskinserted = true;
                break;
            }
        }
        if( false == newtaskinserted ) {
            m_tasks.data.emplace_back( newtask );
        }
    }
    // potentially wake a worker to handle the new task
    m_condition.notify_one();
    // all done
    return true;
}

// executes python script stored in specified file. returns true on success
auto python_taskqueue::run_file( std::string const &File, std::string const &Path ) -> bool {

    auto const lookup { FileExists( { Path + File, "python/local/" + File }, { ".py" } ) };
    if( lookup.first.empty() ) { return false; }

    std::ifstream inputfile { lookup.first + lookup.second };
    std::string input;
    input.assign( std::istreambuf_iterator<char>( inputfile ), std::istreambuf_iterator<char>() );

    if( PyRun_SimpleString( input.c_str() ) != 0 ) {
        error();
        return false;
    }

    return true;
}

// acquires the python gil and sets the main thread as current
void python_taskqueue::acquire_lock() {

    PyEval_RestoreThread( m_mainthread );
}

// releases the python gil and swaps the main thread out
void python_taskqueue::release_lock() {

    PyEval_SaveThread();
}

auto python_taskqueue::fetch_renderer( std::string const Renderer ) ->PyObject * {

    auto const lookup { m_renderers.find( Renderer ) };
    if( lookup != std::end( m_renderers ) ) {
        return lookup->second;
    }
    // try to load specified renderer class
    auto const path { substr_path( Renderer ) };
    auto const file { Renderer.substr( path.size() ) };
    PyObject *renderer { nullptr };
    PyObject *rendererarguments { nullptr };
    acquire_lock();
    {
        if( m_main == nullptr ) {
            ErrorLog( "Python Renderer: __main__ module is missing" );
            goto cache_and_return;
        }

        if( false == run_file( file, path ) ) {
            goto cache_and_return;
        }
        auto *renderername{ PyObject_GetAttrString( m_main, file.c_str() ) };
        if( renderername == nullptr ) {
            ErrorLog( "Python Renderer: class \"" + file + "\" not defined" );
            goto cache_and_return;
        }
        rendererarguments = Py_BuildValue( "(s)", path.c_str() );
        if( rendererarguments == nullptr ) {
            ErrorLog( "Python Renderer: failed to create initialization arguments" );
            goto cache_and_return;
        }
        renderer = PyObject_CallObject( renderername, rendererarguments );

        if( PyErr_Occurred() != nullptr ) {
            error();
            renderer = nullptr;
        }

cache_and_return:
        // clean up after yourself
        if( rendererarguments != nullptr ) {
            Py_DECREF( rendererarguments );
        }
    }
    release_lock();
    // cache the failures as well so we don't try again on subsequent requests
    m_renderers.emplace( Renderer, renderer );
    return renderer;
}

void python_taskqueue::run( GLFWwindow *Context, rendertask_sequence &Tasks, threading::condition_variable &Condition, std::atomic<bool> &Exit ) {

    glfwMakeContextCurrent( Context );
    // create a state object for this thread
    PyEval_AcquireLock();
    auto *threadstate { PyThreadState_New( m_mainthread->interp ) };
    PyEval_ReleaseLock();

    render_task *task { nullptr };

    while( false == Exit.load() ) {
        // regardless of the reason we woke up prime the spurious wakeup flag for the next time
        Condition.spurious( true );
        // keep working as long as there's any scheduled tasks
        do {
            task = nullptr;
            // acquire a lock on the task queue and potentially grab a task from it
            {
                std::lock_guard<std::mutex> lock( Tasks.mutex );
                if( false == Tasks.data.empty() ) {
                    // fifo
                    task = Tasks.data.front();
                    Tasks.data.pop_front();
                }
            }
            if( task != nullptr ) {
                // swap in my thread state
                PyEval_RestoreThread( threadstate );
                {
                    // execute python code
                    task->run();
                    error();
                }
                // clear the thread state
                PyEval_SaveThread();
            }
            // TBD, TODO: add some idle time between tasks in case we're on a single thread cpu?
        } while( task != nullptr );
        // if there's nothing left to do wait until there is
        // but check every now and then on your own to minimize potential deadlock situations
        Condition.wait_for( std::chrono::seconds( 5 ) );
    }
    // clean up thread state data
    PyEval_AcquireLock();
    PyThreadState_Swap( nullptr );
    PyThreadState_Clear( threadstate );
    PyThreadState_Delete( threadstate );
    PyEval_ReleaseLock();
}

void
python_taskqueue::error() {

    if( PyErr_Occurred() == nullptr ) { return; }

    if( m_error != nullptr ) {
        // std err pythona jest buforowane
        PyErr_Print();
        auto *errortext { PyObject_CallMethod( m_error, "getvalue", nullptr ) };
        ErrorLog( PyString_AsString( errortext ) );
        // czyscimy bufor na kolejne bledy
        PyObject_CallMethod( m_error, "truncate", "i", 0 );
    }
    else {
        // nie dziala buffor pythona
        PyObject *type, *value, *traceback;
        PyErr_Fetch( &type, &value, &traceback );
        if( type == nullptr ) {
            ErrorLog( "Python Interpreter: don't know how to handle null exception" );
        }
        PyErr_NormalizeException( &type, &value, &traceback );
        if( type == nullptr ) {
            ErrorLog( "Python Interpreter: don't know how to handle null exception" );
        }
        auto *typetext { PyObject_Str( type ) };
        if( typetext != nullptr ) {
            ErrorLog( PyString_AsString( typetext ) );
        }
        if( value != nullptr ) {
            ErrorLog( PyString_AsString( value ) );
        }
        auto *tracebacktext { PyObject_Str( traceback ) };
        if( tracebacktext != nullptr ) {
            WriteLog( PyString_AsString( tracebacktext ) );
        }
        else {
            WriteLog( "Python Interpreter: failed to retrieve the stack traceback" );
        }
    }
}