/**
  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.
 */

/**
 * @file InterceptPlugin.cc
 */

#include "atscppapi/InterceptPlugin.h"

#include <ts/ts.h>
#include "logging_internal.h"
#include "atscppapi/noncopyable.h"
#include "utils_internal.h"

#include <cstdlib>
#include <cerrno>

#ifndef INT64_MAX
#define INT64_MAX (9223372036854775807LL)
#endif

using namespace atscppapi;
using std::string;

namespace {

/** This contains info for the continuation callback to invoke the plugin */
struct PluginHandle {
  InterceptPlugin *plugin_;
  shared_ptr<Mutex> mutex_;
  PluginHandle(InterceptPlugin *plugin, shared_ptr<Mutex> mutex) : plugin_(plugin), mutex_(mutex) { }
};

}

/**
 * @private
 */
struct InterceptPlugin::State {
  TSCont cont_;
  TSVConn net_vc_;

  struct IoHandle {
    TSVIO vio_;
    TSIOBuffer buffer_;
    TSIOBufferReader reader_;
    IoHandle() : vio_(NULL), buffer_(NULL), reader_(NULL) { };
    ~IoHandle() {
      if (reader_) {
        TSIOBufferReaderFree(reader_);
      }
      if (buffer_) {
        TSIOBufferDestroy(buffer_);
      }
    };
  };

  IoHandle input_;
  IoHandle output_;

  /** the API doesn't recognize end of input; so we have to explicitly
   * figure out when to continue reading and when to stop */
  TSHttpParser http_parser_;
  int expected_body_size_;
  int num_body_bytes_read_;
  bool hdr_parsed_;

  TSMBuffer hdr_buf_;
  TSMLoc hdr_loc_;
  int num_bytes_written_;
  PluginHandle *plugin_handle_;
  bool shut_down_;

  State(TSCont cont) : cont_(cont), net_vc_(NULL), expected_body_size_(0), num_body_bytes_read_(0),
                       hdr_parsed_(false), hdr_buf_(NULL), hdr_loc_(NULL), num_bytes_written_(0), 
                       plugin_handle_(NULL), shut_down_(false) {
    http_parser_ = TSHttpParserCreate();
  }
  
  ~State() {
    TSHttpParserDestroy(http_parser_); 
    if (hdr_loc_) {
      TSHandleMLocRelease(hdr_buf_, TS_NULL_MLOC, hdr_loc_);
    }
    if (hdr_buf_) {
      TSMBufferDestroy(hdr_buf_);
    }
  }
};

namespace {

int handleEvents(TSCont cont, TSEvent event, void *edata);

}

InterceptPlugin::InterceptPlugin(Transaction &transaction, InterceptPlugin::Type type)
  : TransactionPlugin(transaction) {
  TSCont cont = TSContCreate(handleEvents, TSMutexCreate());
  state_ = new State(cont);
  state_->plugin_handle_ = new PluginHandle(this, TransactionPlugin::getMutex());
  TSContDataSet(cont, state_->plugin_handle_);
  TSHttpTxn txn = static_cast<TSHttpTxn>(transaction.getAtsHandle());
  if (type == SERVER_INTERCEPT) {
    TSHttpTxnServerIntercept(cont, txn);
  }
  else {
    TSHttpTxnIntercept(cont, txn);
  }
  Headers &request_headers = transaction.getClientRequest().getHeaders();
  string content_length_str = request_headers.value("Content-Length");
  if (!content_length_str.empty()) {
    const char *start_ptr = content_length_str.data();
    char *end_ptr;
    int content_length = strtol(start_ptr, &end_ptr, 10 /* base */);
    if ((errno != ERANGE) && (end_ptr != start_ptr) && (*end_ptr == '\0')) {
      LOG_DEBUG("Got content length: %d", content_length);
      state_->expected_body_size_ = content_length;
    }
    else {
      LOG_ERROR("Invalid content length header [%s]; Assuming no content", content_length_str.c_str());
    }
  }
  if (request_headers.value("Transfer-Encoding") == "chunked") {
    // implementing a "dechunker" is non-trivial and in the real
    // world, most browsers don't send chunked requests
    LOG_ERROR("Support for chunked request not implemented! Assuming no body");
  }
  LOG_DEBUG("Expecting %d bytes of request body", state_->expected_body_size_);
}

InterceptPlugin::~InterceptPlugin() {
  if (!state_->shut_down_) {
    // transaction is closing, but intercept hasn't finished. Indicate
    // that plugin is dead (cleanup will be done by continuation
    // callback)
    state_->plugin_handle_->plugin_ = NULL;
  }
  else {
    TSContDestroy(state_->cont_);
    delete state_->plugin_handle_;
  }
  delete state_;
}

bool InterceptPlugin::produce(const void *data, int data_size) {
  ScopedSharedMutexLock scopedLock(getMutex());
  if (!state_->net_vc_) {
    LOG_ERROR("Intercept not operational yet");
    return false;
  }
  if (!state_->output_.buffer_) {
    state_->output_.buffer_ = TSIOBufferCreate();
    state_->output_.reader_ = TSIOBufferReaderAlloc(state_->output_.buffer_);
    state_->output_.vio_ = TSVConnWrite(state_->net_vc_, state_->cont_, state_->output_.reader_, INT64_MAX);
  }
  int num_bytes_written = TSIOBufferWrite(state_->output_.buffer_, data, data_size);
  if (num_bytes_written != data_size) {
    LOG_ERROR("Error while writing to buffer! Attempted %d bytes but only wrote %d bytes", data_size,
              num_bytes_written);
    return false;
  }
  TSVIOReenable(state_->output_.vio_);
  state_->num_bytes_written_ += data_size;
  LOG_DEBUG("Wrote %d bytes in response", data_size);
  return true;
}

bool InterceptPlugin::setOutputComplete() {
  ScopedSharedMutexLock scopedLock(getMutex());
  if (!state_->net_vc_) {
    LOG_ERROR("Intercept not operational yet");
    return false;
  }
  if (!state_->output_.buffer_) {
    LOG_ERROR("No output produced so far");
    return false;
  }
  TSVIONBytesSet(state_->output_.vio_, state_->num_bytes_written_);
  TSVIOReenable(state_->output_.vio_);
  LOG_DEBUG("Response complete");
  return true;
}

bool InterceptPlugin::doRead() {
  int avail = TSIOBufferReaderAvail(state_->input_.reader_);
  if (avail == TS_ERROR) {
    LOG_ERROR("Error while getting number of bytes available");
    return false;
  }
  
  int consumed = 0; // consumed is used to update the input buffers
  if (avail > 0) {
    int64_t num_body_bytes_in_block;
    int64_t data_len; // size of all data (header + body) in a block
    const char *data, *startptr;
    TSIOBufferBlock block = TSIOBufferReaderStart(state_->input_.reader_);
    while (block != NULL) {
      startptr = data = TSIOBufferBlockReadStart(block, state_->input_.reader_, &data_len);
      num_body_bytes_in_block = 0;
      if (!state_->hdr_parsed_) {
        const char *endptr = data + data_len;
        if (TSHttpHdrParseReq(state_->http_parser_, state_->hdr_buf_, state_->hdr_loc_, &data,
                              endptr) == TS_PARSE_DONE) {
          LOG_DEBUG("Parsed header");
          state_->hdr_parsed_ = true;
          // remaining data in this block is body; 'data' will be pointing to first byte of the body
          num_body_bytes_in_block = endptr - data;
        }
        consume(string(startptr, data - startptr), InterceptPlugin::REQUEST_HEADER);
      }
      else {
        num_body_bytes_in_block = data_len;
      }
      if (num_body_bytes_in_block) {
        state_->num_body_bytes_read_ += num_body_bytes_in_block;
        consume(string(data, num_body_bytes_in_block), InterceptPlugin::REQUEST_BODY);
      }
      consumed += data_len;
      block = TSIOBufferBlockNext(block);
    }
  }
  LOG_DEBUG("Consumed %d bytes from input vio", consumed);
  TSIOBufferReaderConsume(state_->input_.reader_, consumed);
  
  // Modify the input VIO to reflect how much data we've completed.
  TSVIONDoneSet(state_->input_.vio_, TSVIONDoneGet(state_->input_.vio_) + consumed);

  if ((state_->hdr_parsed_) && (state_->num_body_bytes_read_ >= state_->expected_body_size_)) {
    LOG_DEBUG("Completely read body");
    if (state_->num_body_bytes_read_ > state_->expected_body_size_) {
      LOG_ERROR("Read more data than specified in request");
      // TODO: any further action required?
    }
    handleInputComplete();
  }
  else {
    LOG_DEBUG("Reenabling input vio as %d bytes still need to be read",
              state_->expected_body_size_ - state_->num_body_bytes_read_);
    TSVIOReenable(state_->input_.vio_);
  }
  return true;
}

void InterceptPlugin::handleEvent(int abstract_event, void *edata) {
  TSEvent event = static_cast<TSEvent>(abstract_event);
  LOG_DEBUG("Received event %d", event);

  switch (event) {

  case TS_EVENT_NET_ACCEPT:
    LOG_DEBUG("Handling net accept");
    state_->net_vc_ = static_cast<TSVConn>(edata);
    state_->input_.buffer_ = TSIOBufferCreate();
    state_->input_.reader_ = TSIOBufferReaderAlloc(state_->input_.buffer_);
    state_->input_.vio_ = TSVConnRead(state_->net_vc_, state_->cont_, state_->input_.buffer_,
                                      INT64_MAX /* number of bytes to read - high value initially */);

    state_->hdr_buf_ = TSMBufferCreate();
    state_->hdr_loc_ = TSHttpHdrCreate(state_->hdr_buf_);
    TSHttpHdrTypeSet(state_->hdr_buf_, state_->hdr_loc_, TS_HTTP_TYPE_REQUEST);
    break;

  case TS_EVENT_VCONN_WRITE_READY: // nothing to do
    LOG_DEBUG("Got write ready"); 
    break;

  case TS_EVENT_VCONN_READ_READY:
    LOG_DEBUG("Handling read ready");  
    if (doRead()) {
      break;
    }
    // else fall through into the next shut down cases
    LOG_ERROR("Error while reading request!");
  case TS_EVENT_VCONN_READ_COMPLETE: // fall throughs intentional
  case TS_EVENT_VCONN_WRITE_COMPLETE:
  case TS_EVENT_VCONN_EOS:
  case TS_EVENT_ERROR: // erroring out, nothing more to do
  case TS_EVENT_NET_ACCEPT_FAILED: // somebody canceled the transaction
    if (event == TS_EVENT_ERROR) {
      LOG_ERROR("Unknown Error!");
    }
    else if (event == TS_EVENT_NET_ACCEPT_FAILED) {
      LOG_ERROR("Got net_accept_failed!");
    }
    LOG_DEBUG("Shutting down");
    if (state_->net_vc_) {
      TSVConnClose(state_->net_vc_);
    }
    state_->shut_down_ = true;
    break;

  default:
    LOG_ERROR("Unknown event %d", event);
  }
}

namespace {

int handleEvents(TSCont cont, TSEvent event, void *edata) {
  PluginHandle *plugin_handle = static_cast<PluginHandle *>(TSContDataGet(cont));
  ScopedSharedMutexLock scopedSharedMutexLock(plugin_handle->mutex_);
  if (plugin_handle->plugin_) {
    utils::internal::dispatchInterceptEvent(plugin_handle->plugin_, event, edata);
  }
  else {
    // plugin is dead; cleanup
    LOG_ERROR("Received event %d after plugin died!", event);
    TSContDestroy(cont);
    delete plugin_handle;
  }
  return 0;
}

}