/* Copyright (C) 2010 Tony Garnock-Jones. All rights reserved. */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <stdint.h>
#include <stddef.h>

#include <assert.h>

#include <ucontext.h>

#include "cmsg_private.h"
#include "harness.h"
#include "ref.h"
#include "sexp.h"
#include "hashtable.h"
#include "node.h"

typedef struct direct_extension_t_ {
  sexp_t *name;
  hashtable_t routing_table;
  hashtable_t subscriptions;
} direct_extension_t;

typedef struct subscription_t_ {
  sexp_t *uuid;
  sexp_t *sink;
  sexp_t *name;
  struct subscription_t_ *link;
} subscription_t;

static void free_subscription(subscription_t *sub) {
  DECREF(sub->uuid, sexp_destructor);
  DECREF(sub->sink, sexp_destructor);
  DECREF(sub->name, sexp_destructor);
  free(sub);
}

static void free_subscription_chain(void *context, cmsg_bytes_t key, void *value) {
  subscription_t *chain = value;
  while (chain != NULL) {
    subscription_t *next = chain->link;
    free_subscription(chain);
    chain = next;
  }
}

static sexp_t *direct_extend(node_t *n, sexp_t *args) {
  if ((sexp_length(args) == 1) && sexp_stringp(sexp_head(args))) {
    cmsg_bytes_t name = sexp_data(sexp_head(args));
    direct_extension_t *d = calloc(1, sizeof(*d));
    d->name = INCREF(sexp_head(args));
    init_hashtable(&d->routing_table, 5, NULL, NULL);
    init_hashtable(&d->subscriptions, 5, NULL, NULL);

    n->extension = d;
    return bind_node(name, n) ? NULL : sexp_cstring("bind failed");
  } else {
    return sexp_cstring("invalid args");
  }
}

static void direct_destructor(node_t *n) {
  direct_extension_t *d = n->extension;
  if (d != NULL) { /* can be NULL if direct_extend was given invalid args */
    DECREF(d->name, sexp_destructor);
    hashtable_foreach(&d->routing_table, free_subscription_chain, NULL);
    destroy_hashtable(&d->routing_table);
    destroy_hashtable(&d->subscriptions);
    free(d);
  }
}

static int send_to_sub(subscription_t *sub, sexp_t *body) {
  return post_node(sexp_data(sub->sink), sexp_data(sub->name), body, sub->uuid);
}

static void route_message(direct_extension_t *d, sexp_t *rk, sexp_t *body) {
  subscription_t *chain = NULL;
  subscription_t *prev = NULL;
  hashtable_get(&d->routing_table, sexp_data(rk), (void **) &chain);
  while (chain != NULL) {
    subscription_t *next = chain->link;
    if (!send_to_sub(chain, body)) { /* Destination no longer exists. */
      info("Destination not found\n");
      if (prev == NULL) {
	hashtable_put(&d->routing_table, sexp_data(rk), chain->link);
      } else {
	prev->link = chain->link;
      }
      chain->link = NULL;
      free_subscription(chain);
    }
    chain = next;
  }
}

static void direct_handle_message(node_t *n, sexp_t *m) {
  direct_extension_t *d = n->extension;

  size_t msglen = sexp_length(m);
  sexp_t *args;
  cmsg_bytes_t selector;

  if (msglen == 0 || !sexp_stringp(sexp_head(m))) {
    warn("Invalid message in direct\n");
    return;
  }

  selector = sexp_data(sexp_head(m));
  args = sexp_tail(m);

  if ((msglen == 4) && !cmsg_bytes_cmp(selector, cmsg_cstring_bytes("post"))) {
    sexp_t *rk = sexp_listref(args, 0);
    if (sexp_stringp(rk)) {
      route_message(d, rk, sexp_listref(args, 1));
    } else {
      warn("Non-string routing key in direct\n");
    }
  } else if ((msglen == 6) && !cmsg_bytes_cmp(selector, cmsg_cstring_bytes("subscribe"))) {
    unsigned char uuid[CMSG_UUID_BUF_SIZE];
    if (gen_uuid(uuid) != 0) {
      warn("Could not generate UUID\n");
    } else {
      sexp_t *filter = sexp_listref(args, 0);
      sexp_t *reply_sink = sexp_listref(args, 3);
      sexp_t *reply_name = sexp_listref(args, 4);
      subscription_t *sub = malloc(sizeof(*sub));
      sub->uuid = INCREF(sexp_bytes(CMSG_BYTES(sizeof(uuid), uuid)));
      sub->sink = sexp_listref(args, 1);
      sub->name = sexp_listref(args, 2);
      sub->link = NULL;
      if (!sexp_stringp(filter)
	  || !sexp_stringp(sub->sink) || !sexp_stringp(sub->name)
	  || !sexp_stringp(reply_sink) || !sexp_stringp(reply_name)) {
	DECREF(sub->uuid, sexp_destructor);
	free(sub);
	warn("Bad sink/name/reply_sink/reply_name in subscribe");
      } else {
	INCREF(sub->sink);
	INCREF(sub->name);
	hashtable_put(&d->subscriptions, sexp_data(sub->uuid), sub);
	hashtable_get(&d->routing_table, sexp_data(filter), (void **) &sub->link);
	hashtable_put(&d->routing_table, sexp_data(filter), sub);
	{
	  sexp_t *subok = sexp_cons(sexp_cstring("subscribe-ok"), sexp_cons(sub->uuid, NULL));
	  INCREF(subok);
	  post_node(sexp_data(reply_sink), sexp_data(reply_name), subok, sexp_empty_bytes);
	  DECREF(subok, sexp_destructor);
	}
      }
    }
  } else if ((msglen == 2) && !cmsg_bytes_cmp(selector, cmsg_cstring_bytes("unsubscribe"))) {
    if (sexp_stringp(sexp_head(args))) {
      cmsg_bytes_t uuid = sexp_data(sexp_head(args));
      subscription_t *sub;
      if (hashtable_get(&d->subscriptions, uuid, (void **) &sub)) {
	/* TODO: clean up more eagerly perhaps? */
	hashtable_erase(&d->subscriptions, uuid);
	DECREF(sub->uuid, sexp_destructor);
	sub->uuid = NULL;
      }
    } else {
      warn("Invalid unsubscription\n");
    }
  } else {
    warn("Message not understood in direct; selector <<%.*s>>, length %u\n",
	 selector.len, selector.bytes,
	 msglen);
  }
}

static node_class_t direct_class = {
  .name = "direct",
  .extend = direct_extend,
  .destroy = direct_destructor,
  .handle_message = direct_handle_message
};

void init_direct(void) {
  register_node_class(&direct_class);
}