/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd
 * Copyright (c) 2017 Pycom Limited
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "stdio.h"

#include "py/runtime.h"
#include "py/gc.h"
#include "py/mpthread.h"
#include "py/mphal.h"
#include "mpthreadport.h"

#include "esp_task.h"

#if MICROPY_PY_THREAD

#define MP_THREAD_MIN_STACK_SIZE                        (4 * 1024)
#define MP_THREAD_DEFAULT_STACK_SIZE                    (MP_THREAD_MIN_STACK_SIZE + MICROPY_STACK_CHECK_MARGIN)
#define MP_THREAD_PRIORITY                              (ESP_TASK_PRIO_MIN + 1)

typedef enum {
    MP_THREAD_RUN_STATE_NEW,
    MP_THREAD_RUN_STATE_RUNNING,
    MP_THREAD_RUN_STATE_FINISHED,
} mp_thread_run_state_t;

// this structure forms a linked list, one node per active thread
typedef struct _mp_thread_t {
    TaskHandle_t id;        // system id of thread
    mp_thread_run_state_t run_state; // current run state of the thread
    void *arg;              // thread Python args, a GC root pointer
    void *stack;            // pointer to the stack
    size_t stack_len;       // number of words in the stack
    struct _mp_thread_t *next;
} mp_thread_t;

// the mutex controls access to the linked list
static mp_thread_mutex_t thread_mutex;
static mp_thread_t thread_entry0;
static mp_thread_t *thread = NULL; // root pointer, handled by mp_thread_gc_others

void mp_thread_init(void *stack, uint32_t stack_len) {
    mp_thread_set_state(&mp_state_ctx.thread);
    // create the first entry in the linked list of all threads
    thread_entry0.id = xTaskGetCurrentTaskHandle();
    thread_entry0.run_state = MP_THREAD_RUN_STATE_RUNNING;
    thread_entry0.arg = NULL;
    thread_entry0.stack = stack;
    thread_entry0.stack_len = stack_len;
    thread_entry0.next = NULL;
    thread = &thread_entry0;
    mp_thread_mutex_init(&thread_mutex);

    // memory barrier to ensure above data is committed
    __sync_synchronize();
}

void mp_thread_gc_others(void) {
    mp_thread_mutex_lock(&thread_mutex, 1);
    for (mp_thread_t *th = thread; th != NULL; th = th->next) {
        gc_collect_root((void **)&th, 1);
        gc_collect_root(&th->arg, 1); // probably not needed
        if (th->id == xTaskGetCurrentTaskHandle()) {
            continue;
        }
        if (th->run_state != MP_THREAD_RUN_STATE_RUNNING) {
            continue;
        }
        gc_collect_root(th->stack, th->stack_len);
    }
    mp_thread_mutex_unlock(&thread_mutex);
}

mp_state_thread_t *mp_thread_get_state(void) {
    return pvTaskGetThreadLocalStoragePointer(NULL, 1);
}

void mp_thread_set_state(mp_state_thread_t *state) {
    vTaskSetThreadLocalStoragePointer(NULL, 1, state);
}

mp_uint_t mp_thread_get_id(void) {
    return (mp_uint_t)xTaskGetCurrentTaskHandle();
}

void mp_thread_start(void) {
    mp_thread_mutex_lock(&thread_mutex, 1);
    for (mp_thread_t *th = thread; th != NULL; th = th->next) {
        if (th->id == xTaskGetCurrentTaskHandle()) {
            th->run_state = MP_THREAD_RUN_STATE_RUNNING;
            break;
        }
    }
    mp_thread_mutex_unlock(&thread_mutex);
}

static void *(*ext_thread_entry)(void *) = NULL;

static void freertos_entry(void *arg) {
    // Run the Python code.
    if (ext_thread_entry) {
        ext_thread_entry(arg);
    }

    // Remove the thread from the linked-list of active threads.
    mp_thread_mutex_lock(&thread_mutex, 1);
    for (mp_thread_t **th = &thread; *th != NULL; th = &(*th)->next) {
        if ((*th)->id == xTaskGetCurrentTaskHandle()) {
            *th = (*th)->next;
        }
    }
    mp_thread_mutex_unlock(&thread_mutex);

    // Delete this FreeRTOS task (this call to vTaskDelete will not return).
    vTaskDelete(NULL);
}

mp_uint_t mp_thread_create_ex(void *(*entry)(void *), void *arg, size_t *stack_size, int priority, char *name) {
    // store thread entry function into a global variable so we can access it
    ext_thread_entry = entry;

    if (*stack_size == 0) {
        *stack_size = MP_THREAD_DEFAULT_STACK_SIZE; // default stack size
    } else if (*stack_size < MP_THREAD_MIN_STACK_SIZE) {
        *stack_size = MP_THREAD_MIN_STACK_SIZE; // minimum stack size
    }

    // Allocate linked-list node (must be outside thread_mutex lock)
    mp_thread_t *th = m_new_obj(mp_thread_t);

    mp_thread_mutex_lock(&thread_mutex, 1);

    // create thread
    BaseType_t result = xTaskCreatePinnedToCore(freertos_entry, name, *stack_size / sizeof(StackType_t), arg, priority, &th->id, MP_TASK_COREID);
    if (result != pdPASS) {
        mp_thread_mutex_unlock(&thread_mutex);
        mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("can't create thread"));
    }

    // add thread to linked list of all threads
    th->run_state = MP_THREAD_RUN_STATE_NEW;
    th->arg = arg;
    th->stack = pxTaskGetStackStart(th->id);
    th->stack_len = *stack_size / sizeof(uintptr_t);
    th->next = thread;
    thread = th;

    mp_thread_mutex_unlock(&thread_mutex);

    return (mp_uint_t)th->id;
}

mp_uint_t mp_thread_create(void *(*entry)(void *), void *arg, size_t *stack_size) {
    return mp_thread_create_ex(entry, arg, stack_size, MP_THREAD_PRIORITY, "mp_thread");
}

void mp_thread_finish(void) {
    mp_thread_mutex_lock(&thread_mutex, 1);
    for (mp_thread_t *th = thread; th != NULL; th = th->next) {
        if (th->id == xTaskGetCurrentTaskHandle()) {
            th->run_state = MP_THREAD_RUN_STATE_FINISHED;
            break;
        }
    }
    mp_thread_mutex_unlock(&thread_mutex);
}

void mp_thread_mutex_init(mp_thread_mutex_t *mutex) {
    // Need a binary semaphore so a lock can be acquired on one Python thread
    // and then released on another.
    mutex->handle = xSemaphoreCreateBinaryStatic(&mutex->buffer);
    xSemaphoreGive(mutex->handle);
}

int mp_thread_mutex_lock(mp_thread_mutex_t *mutex, int wait) {
    return pdTRUE == xSemaphoreTake(mutex->handle, wait ? portMAX_DELAY : 0);
}

void mp_thread_mutex_unlock(mp_thread_mutex_t *mutex) {
    xSemaphoreGive(mutex->handle);
    // Python threads run at equal priority, so preemptively yield here to
    // prevent pathological imbalances where a thread unlocks and then
    // immediately re-locks a mutex before a context switch can occur, leaving
    // another thread waiting for an unbounded period of time.
    taskYIELD();
}

void mp_thread_deinit(void) {
    // The current task should be thread_entry0 and should be the last in the linked list.
    assert(thread_entry0.id == xTaskGetCurrentTaskHandle());
    assert(thread_entry0.next == NULL);

    // Delete all tasks except the main one.
    mp_thread_mutex_lock(&thread_mutex, 1);
    for (mp_thread_t *th = thread; th != NULL; th = th->next) {
        if (th != &thread_entry0) {
            vTaskDelete(th->id);
        }
    }
    thread = &thread_entry0;
    mp_thread_mutex_unlock(&thread_mutex);

    // Give the idle task a chance to run, to clean up any deleted tasks.
    vTaskDelay(1);
}

#endif // MICROPY_PY_THREAD