/* Copyright (c) 2002-2009 Dovecot authors, see the included COPYING file */

#include "common.h"
#include "ioloop.h"
#include "istream.h"
#include "ostream.h"
#include "crc32.h"
#include "commands.h"
#include "mail-user.h"
#include "imap-sync.h"

#include <stdlib.h>

#define DEFAULT_IDLE_CHECK_INTERVAL 30
/* Send some noice to client every few minutes to avoid NATs and stateful
   firewalls from closing the connection */
#define DEFAULT_IMAP_IDLE_NOTIFY_INTERVAL (2*60)

struct cmd_idle_context {
	struct client *client;
	struct client_command_context *cmd;

	struct imap_sync_context *sync_ctx;
	struct timeout *keepalive_to;

	unsigned int manual_cork:1;
	unsigned int sync_pending:1;
};

static void idle_add_keepalive_timeout(struct cmd_idle_context *ctx);
static bool cmd_idle_continue(struct client_command_context *cmd);

static void
idle_finish(struct cmd_idle_context *ctx, bool done_ok, bool free_cmd)
{
	struct client *client = ctx->client;

	if (ctx->keepalive_to != NULL)
		timeout_remove(&ctx->keepalive_to);

	if (ctx->sync_ctx != NULL) {
		/* we're here only in connection failure cases */
		(void)imap_sync_deinit(ctx->sync_ctx, ctx->cmd);
	}

	o_stream_cork(client->output);
	if (client->io != NULL)
		io_remove(&client->io);

	if (client->mailbox != NULL)
		mailbox_notify_changes_stop(client->mailbox);

	if (done_ok)
		client_send_tagline(ctx->cmd, "OK Idle completed.");
	else
		client_send_tagline(ctx->cmd, "BAD Expected DONE.");

	o_stream_uncork(client->output);
	if (free_cmd)
		client_command_free(&ctx->cmd);
}

static void idle_client_input(struct cmd_idle_context *ctx)
{
	struct client *client = ctx->client;
	char *line;

	client->last_input = ioloop_time;
	timeout_reset(client->to_idle);

	switch (i_stream_read(client->input)) {
	case -1:
		/* disconnected */
		client_destroy(client, "Disconnected in IDLE");
		return;
	case -2:
		client->input_skip_line = TRUE;
		idle_finish(ctx, FALSE, TRUE);
		client_continue_pending_input(client);
		return;
	}

	if (ctx->sync_ctx != NULL) {
		/* we're still sending output to client. wait until it's all
		   sent so we don't lose any changes. */
		io_remove(&client->io);
		return;
	}

	while ((line = i_stream_next_line(client->input)) != NULL) {
		if (client->input_skip_line)
			client->input_skip_line = FALSE;
		else {
			idle_finish(ctx, strcasecmp(line, "DONE") == 0, TRUE);
			break;
		}
	}
	if (client->disconnected)
		client_destroy(client, NULL);
	else
		client_continue_pending_input(client);
}

static void keepalive_timeout(struct cmd_idle_context *ctx)
{
	if (ctx->client->output_lock != NULL) {
		/* it's busy sending output */
		return;
	}

	/* Sending this keeps NATs/stateful firewalls alive. Sending this
	   also catches dead connections. */
	client_send_line(ctx->client, "* OK Still here");
	/* Make sure idling connections don't get disconnected. There are
	   several clients that really want to IDLE forever and there's not
	   much harm in letting them do so. */
	timeout_reset(ctx->client->to_idle);
	/* recalculate time for the next keepalive timeout */
	idle_add_keepalive_timeout(ctx);
}

static void idle_sync_now(struct mailbox *box, struct cmd_idle_context *ctx)
{
	i_assert(ctx->sync_ctx == NULL);

	ctx->sync_pending = FALSE;
	ctx->sync_ctx = imap_sync_init(ctx->client, box, 0, 0);
	cmd_idle_continue(ctx->cmd);
}

static void idle_callback(struct mailbox *box, struct cmd_idle_context *ctx)
{
	if (ctx->sync_ctx != NULL)
		ctx->sync_pending = TRUE;
	else {
		ctx->manual_cork = TRUE;
		idle_sync_now(box, ctx);
	}
}

static void idle_add_keepalive_timeout(struct cmd_idle_context *ctx)
{
	const char *value;
	unsigned int interval;

	value = getenv("IMAP_IDLE_NOTIFY_INTERVAL");
	interval = value != NULL ?
		(unsigned int)strtoul(value, NULL, 10) :
		DEFAULT_IMAP_IDLE_NOTIFY_INTERVAL;
	if (interval == 0)
		return;

	interval -= (time(NULL) +
		     crc32_str(ctx->client->user->username)) % interval;

	if (ctx->keepalive_to != NULL)
		timeout_remove(&ctx->keepalive_to);
	ctx->keepalive_to = timeout_add(interval * 1000,
					keepalive_timeout, ctx);
}

static bool cmd_idle_continue(struct client_command_context *cmd)
{
	struct client *client = cmd->client;
	struct cmd_idle_context *ctx = cmd->context;
	uoff_t orig_offset = client->output->offset;

	if (cmd->cancel) {
		idle_finish(ctx, FALSE, FALSE);
		return TRUE;
	}

	if (ctx->manual_cork)  {
		/* we're coming from idle_callback instead of a normal
		   I/O handler, so we'll have to do corking manually */
		o_stream_cork(client->output);
	}

	if (ctx->sync_ctx != NULL) {
		if (imap_sync_more(ctx->sync_ctx) == 0) {
			/* unfinished */
			if (ctx->manual_cork) {
				ctx->manual_cork = FALSE;
				o_stream_uncork(client->output);
			}
			cmd->state = CLIENT_COMMAND_STATE_WAIT_OUTPUT;
			return FALSE;
		}

		if (imap_sync_deinit(ctx->sync_ctx, ctx->cmd) < 0) {
			client_send_untagged_storage_error(client,
				mailbox_get_storage(client->mailbox));
			mailbox_notify_changes_stop(client->mailbox);
		}
		ctx->sync_ctx = NULL;
	}
	if (client->output->offset != orig_offset &&
	    ctx->keepalive_to != NULL)
		idle_add_keepalive_timeout(ctx);

	if (ctx->sync_pending) {
		/* more changes occurred while we were sending changes to
		   client */
		idle_sync_now(client->mailbox, ctx);
		/* NOTE: this recurses back to this function,
		   so we return here instead of doing everything twice. */
		return FALSE;
	}
	cmd->state = CLIENT_COMMAND_STATE_WAIT_INPUT;

	if (ctx->manual_cork) {
		ctx->manual_cork = FALSE;
		o_stream_uncork(client->output);
	}

	if (client->output->closed) {
		idle_finish(ctx, FALSE, FALSE);
		return TRUE;
	}
	if (client->io == NULL) {
		/* input is pending */
		client->io = io_add(i_stream_get_fd(client->input),
				    IO_READ, idle_client_input, ctx);
		idle_client_input(ctx);
	}
	return FALSE;
}

bool cmd_idle(struct client_command_context *cmd)
{
	struct client *client = cmd->client;
	struct cmd_idle_context *ctx;
	const char *str;
	unsigned int interval;

	ctx = p_new(cmd->pool, struct cmd_idle_context, 1);
	ctx->cmd = cmd;
	ctx->client = client;
	idle_add_keepalive_timeout(ctx);

	str = getenv("MAILBOX_IDLE_CHECK_INTERVAL");
	interval = str == NULL ? 0 : (unsigned int)strtoul(str, NULL, 10);
	if (interval == 0)
		interval = DEFAULT_IDLE_CHECK_INTERVAL;

	if (client->mailbox != NULL) {
		mailbox_notify_changes(client->mailbox, interval,
				       idle_callback, ctx);
	}
	client_send_line(client, "+ idling");

	io_remove(&client->io);
	client->io = io_add(i_stream_get_fd(client->input),
			    IO_READ, idle_client_input, ctx);

	cmd->func = cmd_idle_continue;
	cmd->context = ctx;

	/* check immediately if there are changes. if they came before we
	   added mailbox-notifier, we wouldn't see them otherwise. */
	if (client->mailbox != NULL)
		idle_sync_now(client->mailbox, ctx);
	return FALSE;
}