/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

#include <thread>
#include <chrono>
#include <atomic>

#include <ts/ts.h>
#include <tscpp/api/Cleanup.h>

using atscppapi::TSContUniqPtr;
using atscppapi::TSThreadUniqPtr;

/*
Test spawning a thread in one transaction hook that runs in parallel with the transaction, until a transaction
continuation on a later hook waits for the thread results.

(To block the transaction until the thread completes, but allow the event task to continue processing events not
related to the transaction, follow the simpler example in example/plugins/c-api/thread_1.)
*/

#define PINAME "polite_hook_wait"

namespace
{
char PIName[] = PINAME;

DbgCtl dbg_ctl{PINAME};

enum Test_step { BEGIN, GLOBAL_CONT_READ_HDRS, THREAD, TXN_CONT, END };

char const *
step_cstr(int test_step)
{
  char const *result{"BAD TEST STEP"};

  switch (test_step) {
  case BEGIN:
    result = "BEGIN";
    break;

  case GLOBAL_CONT_READ_HDRS:
    result = "GLOBAL_CONT_READ_HDRS";
    break;

  case THREAD:
    result = "THREAD";
    break;

  case TXN_CONT:
    result = "TXN_CONT";
    break;

  default:
    break;
  }

  return result;
}

int txn_count{0};

void
next_step(int curr)
{
  static std::atomic<int> test_step{BEGIN};

  TSReleaseAssert(test_step.load(std::memory_order_relaxed) == curr);

  if (BEGIN == curr) {
    ++txn_count;

    TSReleaseAssert(txn_count <= 2);
  }

  ++curr;
  if (END == curr) {
    curr = BEGIN;
  }

  Dbg(dbg_ctl, "Entering test step %s", step_cstr(curr));

  test_step.store(curr, std::memory_order_relaxed);
}

atscppapi::TxnAuxMgrData mgr_data;

class Blocking_action
{
public:
  static void init();

private:
  ~Blocking_action()
  {
    // This should either not block, or only block very briefly.
    //
    TSThreadWait(_checker.get());

    Dbg(dbg_ctl, "In ~Blocking_action()");
  }

  Blocking_action() = default;

  static int   _global_cont_func(TSCont, TSEvent event, void *eventData);
  static int   _txn_cont_func(TSCont, TSEvent event, void *eventData);
  static void *_thread_func(void *vba);

  TSContUniqPtr     _txn_hook_cont{TSContCreate(_txn_cont_func, TSMutexCreate())};
  std::atomic<bool> _cont_mutex_locked{false};

  TSThreadUniqPtr _checker{TSThreadCreate(&_thread_func, this)};

  bool txn_valid{false};

  friend class atscppapi::TxnAuxDataMgr<Blocking_action, mgr_data>;
};

using AuxDataMgr = atscppapi::TxnAuxDataMgr<Blocking_action, mgr_data>;

void
Blocking_action::init()
{
  static TSContUniqPtr global{TSContCreate(_global_cont_func, nullptr)};

  TSHttpHookAdd(TS_HTTP_READ_REQUEST_HDR_HOOK, global.get());
  TSHttpHookAdd(TS_HTTP_SEND_RESPONSE_HDR_HOOK, global.get());
}

int
Blocking_action::_global_cont_func(TSCont, TSEvent event, void *eventData)
{
  Dbg(dbg_ctl, "entering _global_cont_func()");

  TSReleaseAssert(eventData != nullptr);

  TSHttpTxn txn{static_cast<TSHttpTxn>(eventData)};

  switch (event) {
  case TS_EVENT_HTTP_READ_REQUEST_HDR: {
    next_step(BEGIN);

    Blocking_action &ba = AuxDataMgr::data(txn);

    if (!ba._checker.get()) {
      TSError(PINAME ": failed to create thread");
      TSHttpTxnReenable(txn, TS_EVENT_HTTP_CONTINUE);
      return 0;
    }

    TSHttpTxnHookAdd(txn, TS_HTTP_CACHE_LOOKUP_COMPLETE_HOOK, ba._txn_hook_cont.get());

    while (!ba._cont_mutex_locked.load(std::memory_order_acquire)) {
      std::this_thread::yield();
    }
  } break;

  case TS_EVENT_HTTP_SEND_RESPONSE_HDR:
    next_step(TXN_CONT);

    if (!AuxDataMgr::data(txn).txn_valid) {
      static const char msg[] = "authorization denied\n";

      TSHttpTxnErrorBodySet(txn, TSstrdup(msg), sizeof(msg) - 1, TSstrdup("text/plain"));
    }

    break;

  default:
    TSReleaseAssert(false);
    break;
  }

  TSHttpTxnReenable(txn, TS_EVENT_HTTP_CONTINUE);

  return 0;
}

void *
Blocking_action::_thread_func(void *vba)
{
  next_step(GLOBAL_CONT_READ_HDRS);

  auto ba = static_cast<Blocking_action *>(vba);

  TSMutexLock(TSContMutexGet(ba->_txn_hook_cont.get())); // This will never block.
  ba->_cont_mutex_locked.store(true, std::memory_order_release);

  // This is a stand-in for some blocking call to validate the HTTP request in some way.
  // Use a longer delay to account for slower systems and variable scheduling latency.
  //
  std::this_thread::sleep_for(std::chrono::milliseconds(500));

  // Pass "validation" for first transaction, fail it for second.
  //
  if (1 == txn_count) {
    ba->txn_valid = true;
  }

  // Let per-txn continuation run.
  //
  TSMutexUnlock(TSContMutexGet(ba->_txn_hook_cont.get()));

  return nullptr;
}

int
Blocking_action::_txn_cont_func(TSCont, TSEvent event, void *eventData)
{
  next_step(THREAD);

  TSReleaseAssert(eventData != nullptr);
  TSReleaseAssert(TS_EVENT_HTTP_CACHE_LOOKUP_COMPLETE == event);

  TSHttpTxn txn{static_cast<TSHttpTxn>(eventData)};

  Blocking_action &ba = AuxDataMgr::data(txn);

  if (!ba.txn_valid) {
    TSHttpTxnStatusSet(txn, TS_HTTP_STATUS_FORBIDDEN, PINAME);
  }

  TSHttpTxnReenable(txn, ba.txn_valid ? TS_EVENT_HTTP_CONTINUE : TS_EVENT_HTTP_ERROR);

  return 0;
}

} // end anonymous namespace

void
TSPluginInit(int /* n_arg ATS_UNUSED */, char const ** /* arg ATS_UNUSED */)
{
  Dbg(dbg_ctl, "initializing plugin");

  TSPluginRegistrationInfo info;

  info.plugin_name   = const_cast<char *>(PIName);
  info.vendor_name   = const_cast<char *>("apache");
  info.support_email = const_cast<char *>("edge@yahooinc.com");

  if (TSPluginRegister(&info) != TS_SUCCESS) {
    TSError(PINAME ": failure calling TSPluginRegister.");
    return;
  } else {
    Dbg(dbg_ctl, "Plugin registration succeeded.");
  }

  AuxDataMgr::init(PIName);

  Blocking_action::init();
}
