/* 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 fanout_extension_t_ {
  sexp_t *name;
  hashtable_t subscriptions;
} fanout_extension_t;

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

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

static sexp_t *fanout_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));
    fanout_extension_t *f = calloc(1, sizeof(*f));
    f->name = INCREF(sexp_head(args));
    init_hashtable(&f->subscriptions, 5, NULL, free_subscription);

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

static void fanout_destructor(node_t *n) {
  fanout_extension_t *f = n->extension;
  if (f != NULL) { /* can be NULL if fanout_extend was given invalid args */
    DECREF(f->name, sexp_destructor);
    destroy_hashtable(&f->subscriptions);
    free(f);
  }
}

struct delivery_context {
  fanout_extension_t *f;
  sexp_t *body;
};

static void send_to_sub(void *contextv, cmsg_bytes_t key, void *subv) {
  struct delivery_context *context = contextv;
  subscription_t *sub = subv;
  if (!post_node(sexp_data(sub->sink), sexp_data(sub->name), context->body, sub->uuid)) {
    hashtable_erase(&context->f->subscriptions, sexp_data(sub->uuid));
  }
}

static void fanout_handle_message(node_t *n, sexp_t *m) {
  fanout_extension_t *f = 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 fanout\n");
    return;
  }

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

  if ((msglen == 4) && !cmsg_bytes_cmp(selector, cmsg_cstring_bytes("post"))) {
    struct delivery_context context;
    context.f = f;
    context.body = sexp_listref(args, 1);
    hashtable_foreach(&f->subscriptions, send_to_sub, &context);
  } 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 *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);
      if (!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(&f->subscriptions, sexp_data(sub->uuid), 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));
      hashtable_erase(&f->subscriptions, uuid);
    } else {
      warn("Invalid unsubscription\n");
    }
  } else {
    warn("Message not understood in fanout; selector <<%.*s>>, length %u\n",
	 selector.len, selector.bytes,
	 msglen);
  }
}

static node_class_t fanout_class = {
  .name = "fanout",
  .extend = fanout_extend,
  .destroy = fanout_destructor,
  .handle_message = fanout_handle_message
};

void init_fanout(void) {
  register_node_class(&fanout_class);
}