//
//
// Copyright 2015 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//

// Test of gpr synchronization support.

#include <stdint.h>
#include <stdio.h>

#include "gtest/gtest.h"

#include <grpc/support/alloc.h>
#include <grpc/support/sync.h>
#include <grpc/support/time.h>

#include "src/core/lib/gprpp/thd.h"
#include "test/core/util/test_config.h"

// ==================Example use of interface===================

// A producer-consumer queue of up to N integers,
// illustrating the use of the calls in this interface.

#define N 4

typedef struct queue {
  gpr_cv non_empty;  // Signalled when length becomes non-zero.
  gpr_cv non_full;   // Signalled when length becomes non-N.
  gpr_mu mu;         // Protects all fields below.
                     // (That is, except during initialization or
                     // destruction, the fields below should be accessed
                     // only by a thread that holds mu.)
  int head;          // Index of head of queue 0..N-1.
  int length;        // Number of valid elements in queue 0..N.
  int elem[N];       // elem[head .. head+length-1] are queue elements.
} queue;

// Initialize *q.
void queue_init(queue* q) {
  gpr_mu_init(&q->mu);
  gpr_cv_init(&q->non_empty);
  gpr_cv_init(&q->non_full);
  q->head = 0;
  q->length = 0;
}

// Free storage associated with *q.
void queue_destroy(queue* q) {
  gpr_mu_destroy(&q->mu);
  gpr_cv_destroy(&q->non_empty);
  gpr_cv_destroy(&q->non_full);
}

// Wait until there is room in *q, then append x to *q.
void queue_append(queue* q, int x) {
  gpr_mu_lock(&q->mu);
  // To wait for a predicate without a deadline, loop on the negation of the
  // predicate, and use gpr_cv_wait(..., gpr_inf_future(GPR_CLOCK_REALTIME))
  // inside the loop
  // to release the lock, wait, and reacquire on each iteration.  Code that
  // makes the condition true should use gpr_cv_broadcast() on the
  // corresponding condition variable.  The predicate must be on state
  // protected by the lock.
  while (q->length == N) {
    gpr_cv_wait(&q->non_full, &q->mu, gpr_inf_future(GPR_CLOCK_MONOTONIC));
  }
  if (q->length == 0) {  // Wake threads blocked in queue_remove().
    // It's normal to use gpr_cv_broadcast() or gpr_signal() while
    // holding the lock.
    gpr_cv_broadcast(&q->non_empty);
  }
  q->elem[(q->head + q->length) % N] = x;
  q->length++;
  gpr_mu_unlock(&q->mu);
}

// If it can be done without blocking, append x to *q and return non-zero.
// Otherwise return 0.
int queue_try_append(queue* q, int x) {
  int result = 0;
  if (gpr_mu_trylock(&q->mu)) {
    if (q->length != N) {
      if (q->length == 0) {  // Wake threads blocked in queue_remove().
        gpr_cv_broadcast(&q->non_empty);
      }
      q->elem[(q->head + q->length) % N] = x;
      q->length++;
      result = 1;
    }
    gpr_mu_unlock(&q->mu);
  }
  return result;
}

// Wait until the *q is non-empty or deadline abs_deadline passes.  If the
// queue is non-empty, remove its head entry, place it in *head, and return
// non-zero.  Otherwise return 0.
int queue_remove(queue* q, int* head, gpr_timespec abs_deadline) {
  int result = 0;
  gpr_mu_lock(&q->mu);
  // To wait for a predicate with a deadline, loop on the negation of the
  // predicate or until gpr_cv_wait() returns true.  Code that makes
  // the condition true should use gpr_cv_broadcast() on the corresponding
  // condition variable.  The predicate must be on state protected by the
  // lock.
  while (q->length == 0 && !gpr_cv_wait(&q->non_empty, &q->mu, abs_deadline)) {
  }
  if (q->length != 0) {  // Queue is non-empty.
    result = 1;
    if (q->length == N) {  // Wake threads blocked in queue_append().
      gpr_cv_broadcast(&q->non_full);
    }
    *head = q->elem[q->head];
    q->head = (q->head + 1) % N;
    q->length--;
  }  // else deadline exceeded
  gpr_mu_unlock(&q->mu);
  return result;
}

// -------------------------------------------------
// Tests for gpr_mu and gpr_cv, and the queue example.
struct test {
  int nthreads;  // number of threads
  grpc_core::Thread* threads;

  int64_t iterations;  // number of iterations per thread
  int64_t counter;
  int thread_count;  // used to allocate thread ids
  int done;          // threads not yet completed
  int incr_step;     // how much to increment/decrement refcount each time

  gpr_mu mu;  // protects iterations, counter, thread_count, done

  gpr_cv cv;  // signalling depends on test

  gpr_cv done_cv;  // signalled when done == 0

  queue q;

  gpr_stats_counter stats_counter;

  gpr_refcount refcount;
  gpr_refcount thread_refcount;
  gpr_event event;
};

// Return pointer to a new struct test.
static struct test* test_new(int nthreads, int64_t iterations, int incr_step) {
  struct test* m = static_cast<struct test*>(gpr_malloc(sizeof(*m)));
  m->nthreads = nthreads;
  m->threads = static_cast<grpc_core::Thread*>(
      gpr_malloc(sizeof(*m->threads) * nthreads));
  m->iterations = iterations;
  m->counter = 0;
  m->thread_count = 0;
  m->done = nthreads;
  m->incr_step = incr_step;
  gpr_mu_init(&m->mu);
  gpr_cv_init(&m->cv);
  gpr_cv_init(&m->done_cv);
  queue_init(&m->q);
  gpr_stats_init(&m->stats_counter, 0);
  gpr_ref_init(&m->refcount, 0);
  gpr_ref_init(&m->thread_refcount, nthreads);
  gpr_event_init(&m->event);
  return m;
}

// Return pointer to a new struct test.
static void test_destroy(struct test* m) {
  gpr_mu_destroy(&m->mu);
  gpr_cv_destroy(&m->cv);
  gpr_cv_destroy(&m->done_cv);
  queue_destroy(&m->q);
  gpr_free(m->threads);
  gpr_free(m);
}

// Create m->nthreads threads, each running (*body)(m)
static void test_create_threads(struct test* m, void (*body)(void* arg)) {
  int i;
  for (i = 0; i != m->nthreads; i++) {
    m->threads[i] = grpc_core::Thread("grpc_create_threads", body, m);
    m->threads[i].Start();
  }
}

// Wait until all threads report done.
static void test_wait(struct test* m) {
  gpr_mu_lock(&m->mu);
  while (m->done != 0) {
    gpr_cv_wait(&m->done_cv, &m->mu, gpr_inf_future(GPR_CLOCK_MONOTONIC));
  }
  gpr_mu_unlock(&m->mu);
  for (int i = 0; i != m->nthreads; i++) {
    m->threads[i].Join();
  }
}

// Get an integer thread id in the raneg 0..nthreads-1
static int thread_id(struct test* m) {
  int id;
  gpr_mu_lock(&m->mu);
  id = m->thread_count++;
  gpr_mu_unlock(&m->mu);
  return id;
}

// Indicate that a thread is done, by decrementing m->done
// and signalling done_cv if m->done==0.
static void mark_thread_done(struct test* m) {
  gpr_mu_lock(&m->mu);
  ASSERT_NE(m->done, 0);
  m->done--;
  if (m->done == 0) {
    gpr_cv_signal(&m->done_cv);
  }
  gpr_mu_unlock(&m->mu);
}

// Test several threads running (*body)(struct test *m) for increasing settings
// of m->iterations, until about timeout_s to 2*timeout_s seconds have elapsed.
// If extra!=NULL, run (*extra)(m) in an additional thread.
// incr_step controls by how much m->refcount should be incremented/decremented
// (if at all) each time in the tests.
//
static void test(const char* name, void (*body)(void* m),
                 void (*extra)(void* m), int timeout_s, int incr_step) {
  int64_t iterations = 8;
  struct test* m;
  gpr_timespec start = gpr_now(GPR_CLOCK_REALTIME);
  gpr_timespec time_taken;
  gpr_timespec deadline = gpr_time_add(
      start, gpr_time_from_micros(static_cast<int64_t>(timeout_s) * 1000000,
                                  GPR_TIMESPAN));
  fprintf(stderr, "%s:", name);
  fflush(stderr);
  while (gpr_time_cmp(gpr_now(GPR_CLOCK_REALTIME), deadline) < 0) {
    fprintf(stderr, " %ld", static_cast<long>(iterations));
    fflush(stderr);
    m = test_new(10, iterations, incr_step);
    grpc_core::Thread extra_thd;
    if (extra != nullptr) {
      extra_thd = grpc_core::Thread(name, extra, m);
      extra_thd.Start();
      m->done++;  // one more thread to wait for
    }
    test_create_threads(m, body);
    test_wait(m);
    if (extra != nullptr) {
      extra_thd.Join();
    }
    if (m->counter != m->nthreads * m->iterations * m->incr_step) {
      fprintf(stderr, "counter %ld  threads %d  iterations %ld\n",
              static_cast<long>(m->counter), m->nthreads,
              static_cast<long>(m->iterations));
      fflush(stderr);
      ASSERT_TRUE(0);
    }
    test_destroy(m);
    iterations <<= 1;
  }
  time_taken = gpr_time_sub(gpr_now(GPR_CLOCK_REALTIME), start);
  fprintf(stderr, " done %lld.%09d s\n",
          static_cast<long long>(time_taken.tv_sec),
          static_cast<int>(time_taken.tv_nsec));
  fflush(stderr);
}

// Increment m->counter on each iteration; then mark thread as done.
static void inc(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations; i++) {
    gpr_mu_lock(&m->mu);
    m->counter++;
    gpr_mu_unlock(&m->mu);
  }
  mark_thread_done(m);
}

// Increment m->counter under lock acquired with trylock, m->iterations times;
// then mark thread as done.
static void inctry(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations;) {
    if (gpr_mu_trylock(&m->mu)) {
      m->counter++;
      gpr_mu_unlock(&m->mu);
      i++;
    }
  }
  mark_thread_done(m);
}

// Increment counter only when (m->counter%m->nthreads)==m->thread_id; then mark
// thread as done.
static void inc_by_turns(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  int id = thread_id(m);
  for (i = 0; i != m->iterations; i++) {
    gpr_mu_lock(&m->mu);
    while ((m->counter % m->nthreads) != id) {
      gpr_cv_wait(&m->cv, &m->mu, gpr_inf_future(GPR_CLOCK_MONOTONIC));
    }
    m->counter++;
    gpr_cv_broadcast(&m->cv);
    gpr_mu_unlock(&m->mu);
  }
  mark_thread_done(m);
}

// Wait a millisecond and increment counter on each iteration;
// then mark thread as done.
static void inc_with_1ms_delay(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations; i++) {
    gpr_timespec deadline;
    gpr_mu_lock(&m->mu);
    deadline = gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC),
                            gpr_time_from_micros(1000, GPR_TIMESPAN));
    while (!gpr_cv_wait(&m->cv, &m->mu, deadline)) {
    }
    m->counter++;
    gpr_mu_unlock(&m->mu);
  }
  mark_thread_done(m);
}

// Wait a millisecond and increment counter on each iteration, using an event
// for timing; then mark thread as done.
static void inc_with_1ms_delay_event(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations; i++) {
    gpr_timespec deadline;
    deadline = gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
                            gpr_time_from_micros(1000, GPR_TIMESPAN));
    ASSERT_EQ(gpr_event_wait(&m->event, deadline), nullptr);
    gpr_mu_lock(&m->mu);
    m->counter++;
    gpr_mu_unlock(&m->mu);
  }
  mark_thread_done(m);
}

// Produce m->iterations elements on queue m->q, then mark thread as done.
// Even threads use queue_append(), and odd threads use queue_try_append()
// until it succeeds.
static void many_producers(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  int x = thread_id(m);
  if ((x & 1) == 0) {
    for (i = 0; i != m->iterations; i++) {
      queue_append(&m->q, 1);
    }
  } else {
    for (i = 0; i != m->iterations; i++) {
      while (!queue_try_append(&m->q, 1)) {
      }
    }
  }
  mark_thread_done(m);
}

// Consume elements from m->q until m->nthreads*m->iterations are seen,
// wait an extra second to confirm that no more elements are arriving,
// then mark thread as done.
static void consumer(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t n = m->iterations * m->nthreads;
  int64_t i;
  int value;
  for (i = 0; i != n; i++) {
    queue_remove(&m->q, &value, gpr_inf_future(GPR_CLOCK_MONOTONIC));
  }
  gpr_mu_lock(&m->mu);
  m->counter = n;
  gpr_mu_unlock(&m->mu);
  ASSERT_TRUE(
      !queue_remove(&m->q, &value,
                    gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC),
                                 gpr_time_from_micros(1000000, GPR_TIMESPAN))));
  mark_thread_done(m);
}

// Increment m->stats_counter m->iterations times, transfer counter value to
// m->counter, then mark thread as done.
static void statsinc(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations; i++) {
    gpr_stats_inc(&m->stats_counter, 1);
  }
  gpr_mu_lock(&m->mu);
  m->counter = gpr_stats_read(&m->stats_counter);
  gpr_mu_unlock(&m->mu);
  mark_thread_done(m);
}

// Increment m->refcount by m->incr_step for m->iterations times. Decrement
// m->thread_refcount once, and if it reaches zero, set m->event to (void*)1;
// then mark thread as done.
static void refinc(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t i;
  for (i = 0; i != m->iterations; i++) {
    if (m->incr_step == 1) {
      gpr_ref(&m->refcount);
    } else {
      gpr_refn(&m->refcount, m->incr_step);
    }
  }
  if (gpr_unref(&m->thread_refcount)) {
    gpr_event_set(&m->event, reinterpret_cast<void*>(1));
  }
  mark_thread_done(m);
}

// Wait until m->event is set to (void *)1, then decrement m->refcount by 1
// (m->nthreads * m->iterations * m->incr_step) times, and ensure that the last
// decrement caused the counter to reach zero, then mark thread as done.
static void refcheck(void* v /*=m*/) {
  struct test* m = static_cast<struct test*>(v);
  int64_t n = m->iterations * m->nthreads * m->incr_step;
  int64_t i;
  ASSERT_EQ(gpr_event_wait(&m->event, gpr_inf_future(GPR_CLOCK_REALTIME)),
            (void*)1);
  ASSERT_EQ(gpr_event_get(&m->event), (void*)1);
  for (i = 1; i != n; i++) {
    ASSERT_FALSE(gpr_unref(&m->refcount));
    m->counter++;
  }
  ASSERT_TRUE(gpr_unref(&m->refcount));
  m->counter++;
  mark_thread_done(m);
}

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

TEST(SyncTest, MainTest) {
  test("mutex", &inc, nullptr, 1, 1);
  test("mutex try", &inctry, nullptr, 1, 1);
  test("cv", &inc_by_turns, nullptr, 1, 1);
  test("timedcv", &inc_with_1ms_delay, nullptr, 1, 1);
  test("queue", &many_producers, &consumer, 10, 1);
  test("stats_counter", &statsinc, nullptr, 1, 1);
  test("refcount by 1", &refinc, &refcheck, 1, 1);
  test("refcount by 3", &refinc, &refcheck, 1, 3);  // incr_step of 3 is an
                                                    // arbitrary choice. Any
                                                    // number > 1 is okay here
  test("timedevent", &inc_with_1ms_delay_event, nullptr, 1, 1);
}

int main(int argc, char** argv) {
  grpc::testing::TestEnvironment env(&argc, argv);
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}
