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 * notice, this list of conditions and the following disclaimer.
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 * in the documentation and/or other materials provided with the
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#include "src/core/census/grpc_filter.h"

#include <stdio.h>
#include <string.h>

#include <grpc/census.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/slice.h>
#include <grpc/support/time.h>

#include "src/core/channel/channel_stack.h"
#include "src/core/statistics/census_interface.h"
#include "src/core/statistics/census_rpc_stats.h"
#include "src/core/transport/static_metadata.h"

typedef struct call_data {
  census_op_id op_id;
  census_context *ctxt;
  gpr_timespec start_ts;
  int error;

  /* recv callback */
  grpc_metadata_batch *recv_initial_metadata;
  grpc_closure *on_done_recv;
  grpc_closure finish_recv;
} call_data;

typedef struct channel_data { uint8_t unused; } channel_data;

static void extract_and_annotate_method_tag(grpc_metadata_batch *md,
                                            call_data *calld,
                                            channel_data *chand) {
  grpc_linked_mdelem *m;
  for (m = md->list.head; m != NULL; m = m->next) {
    if (m->md->key == GRPC_MDSTR_PATH) {
      gpr_log(GPR_DEBUG, "%s",
              (const char *)GPR_SLICE_START_PTR(m->md->value->slice));
      /* Add method tag here */
    }
  }
}

static void client_mutate_op(grpc_call_element *elem,
                             grpc_transport_stream_op *op) {
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  if (op->send_initial_metadata) {
    extract_and_annotate_method_tag(op->send_initial_metadata, calld, chand);
  }
}

static void client_start_transport_op(grpc_exec_ctx *exec_ctx,
                                      grpc_call_element *elem,
                                      grpc_transport_stream_op *op) {
  client_mutate_op(elem, op);
  grpc_call_next_op(exec_ctx, elem, op);
}

static void server_on_done_recv(grpc_exec_ctx *exec_ctx, void *ptr,
                                bool success) {
  grpc_call_element *elem = ptr;
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  if (success) {
    extract_and_annotate_method_tag(calld->recv_initial_metadata, calld, chand);
  }
  calld->on_done_recv->cb(exec_ctx, calld->on_done_recv->cb_arg, success);
}

static void server_mutate_op(grpc_call_element *elem,
                             grpc_transport_stream_op *op) {
  call_data *calld = elem->call_data;
  if (op->recv_initial_metadata) {
    /* substitute our callback for the op callback */
    calld->recv_initial_metadata = op->recv_initial_metadata;
    calld->on_done_recv = op->recv_initial_metadata_ready;
    op->recv_initial_metadata_ready = &calld->finish_recv;
  }
}

static void server_start_transport_op(grpc_exec_ctx *exec_ctx,
                                      grpc_call_element *elem,
                                      grpc_transport_stream_op *op) {
  /* TODO(ctiller): this code fails. I don't know why. I expect it's
                    incomplete, and someone should look at it soon.

  call_data *calld = elem->call_data;
  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0)); */
  server_mutate_op(elem, op);
  grpc_call_next_op(exec_ctx, elem, op);
}

static void client_init_call_elem(grpc_exec_ctx *exec_ctx,
                                  grpc_call_element *elem,
                                  grpc_call_element_args *args) {
  call_data *d = elem->call_data;
  GPR_ASSERT(d != NULL);
  memset(d, 0, sizeof(*d));
  d->start_ts = gpr_now(GPR_CLOCK_REALTIME);
}

static void client_destroy_call_elem(grpc_exec_ctx *exec_ctx,
                                     grpc_call_element *elem) {
  call_data *d = elem->call_data;
  GPR_ASSERT(d != NULL);
  /* TODO(hongyu): record rpc client stats and census_rpc_end_op here */
}

static void server_init_call_elem(grpc_exec_ctx *exec_ctx,
                                  grpc_call_element *elem,
                                  grpc_call_element_args *args) {
  call_data *d = elem->call_data;
  GPR_ASSERT(d != NULL);
  memset(d, 0, sizeof(*d));
  d->start_ts = gpr_now(GPR_CLOCK_REALTIME);
  /* TODO(hongyu): call census_tracing_start_op here. */
  grpc_closure_init(&d->finish_recv, server_on_done_recv, elem);
}

static void server_destroy_call_elem(grpc_exec_ctx *exec_ctx,
                                     grpc_call_element *elem) {
  call_data *d = elem->call_data;
  GPR_ASSERT(d != NULL);
  /* TODO(hongyu): record rpc server stats and census_tracing_end_op here */
}

static void init_channel_elem(grpc_exec_ctx *exec_ctx,
                              grpc_channel_element *elem,
                              grpc_channel_element_args *args) {
  channel_data *chand = elem->channel_data;
  GPR_ASSERT(chand != NULL);
}

static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
                                 grpc_channel_element *elem) {
  channel_data *chand = elem->channel_data;
  GPR_ASSERT(chand != NULL);
}

const grpc_channel_filter grpc_client_census_filter = {
    client_start_transport_op, grpc_channel_next_op, sizeof(call_data),
    client_init_call_elem, grpc_call_stack_ignore_set_pollset,
    client_destroy_call_elem, sizeof(channel_data), init_channel_elem,
    destroy_channel_elem, grpc_call_next_get_peer, "census-client"};

const grpc_channel_filter grpc_server_census_filter = {
    server_start_transport_op, grpc_channel_next_op, sizeof(call_data),
    server_init_call_elem, grpc_call_stack_ignore_set_pollset,
    server_destroy_call_elem, sizeof(channel_data), init_channel_elem,
    destroy_channel_elem, grpc_call_next_get_peer, "census-server"};
