/* Copyright (c) 2006-2016 Dovecot authors, see the included COPYING file */

/* There are several race conditions in this plugin, but they should be
   happening pretty rarely and usually it's not a big problem if the results
   are temporarily wrong. Fixing the races would likely be a lot of work,
   so it's not really worth it. */

#include "lib.h"
#include "ioloop.h"
#include "array.h"
#include "str.h"
#include "master-service.h"
#include "dict.h"
#include "mail-namespace.h"
#include "index-mail.h"
#include "index-storage.h"
#include "expire-set.h"
#include "expire-plugin.h"


#define EXPIRE_CONTEXT(obj) \
	MODULE_CONTEXT(obj, expire_storage_module)
#define EXPIRE_MAIL_CONTEXT(obj) \
	MODULE_CONTEXT(obj, expire_mail_module)
#define EXPIRE_USER_CONTEXT(obj) \
	MODULE_CONTEXT(obj, expire_mail_user_module)

struct expire_mail_index_header {
	uint32_t timestamp;
};

struct expire_mail_user {
	union mail_user_module_context module_ctx;

	struct dict *db;
	struct expire_set *set;
	bool expire_cache;
};

struct expire_mailbox {
	union mailbox_module_context module_ctx;
	uint32_t expire_ext_id;
};

struct expire_transaction_context {
	union mailbox_transaction_module_context module_ctx;

	unsigned int saves:1;
	unsigned int first_expunged:1;
};

const char *expire_plugin_version = DOVECOT_ABI_VERSION;

static MODULE_CONTEXT_DEFINE_INIT(expire_storage_module,
				  &mail_storage_module_register);
static MODULE_CONTEXT_DEFINE_INIT(expire_mail_module, &mail_module_register);
static MODULE_CONTEXT_DEFINE_INIT(expire_mail_user_module,
				  &mail_user_module_register);

static struct mailbox_transaction_context *
expire_mailbox_transaction_begin(struct mailbox *box,
				 enum mailbox_transaction_flags flags)
{
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(box);
	struct mailbox_transaction_context *t;
	struct expire_transaction_context *xt;

	t = xpr_box->module_ctx.super.transaction_begin(box, flags);
	xt = i_new(struct expire_transaction_context, 1);

	MODULE_CONTEXT_SET(t, expire_storage_module, xt);
	return t;
}

static void first_save_timestamp(struct mailbox *box, time_t *stamp_r)
{
	struct mailbox_transaction_context *t;
	const struct mail_index_header *hdr;
	struct mail *mail;

	*stamp_r = ioloop_time;

	t = mailbox_transaction_begin(box, 0);
	mail = mail_alloc(t, 0, NULL);

	/* find the first non-expunged mail. we're here because the first
	   mail was expunged, so don't bother checking it. */
	hdr = mail_index_get_header(box->view);
	if (hdr->messages_count > 0) {
		mail_set_seq(mail, 1);
		(void)mail_get_save_date(mail, stamp_r);
	}
	mail_free(&mail);
	(void)mailbox_transaction_commit(&t);
}

static uint32_t expire_get_ext_id(struct mailbox *box)
{
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(box);

	if (xpr_box->expire_ext_id != (uint32_t)-1)
		return xpr_box->expire_ext_id;

	xpr_box->expire_ext_id =
		mail_index_ext_register(box->index, "expire",
			sizeof(struct expire_mail_index_header), 0, 0);
	return xpr_box->expire_ext_id;
}

static int expire_lookup(struct mailbox *box, const char *key,
			 time_t *new_stamp_r)
{
	struct expire_mail_user *euser =
		EXPIRE_USER_CONTEXT(box->storage->user);
	const struct expire_mail_index_header *hdr;
	const void *data;
	size_t data_size;
	const char *value;
	int ret;

	/* default to ioloop_time for newly saved mails. it may not be exactly
	   the first message's save time, but a few seconds difference doesn't
	   matter */
	*new_stamp_r = ioloop_time;

	if (euser->expire_cache) {
		mail_index_get_header_ext(box->view, expire_get_ext_id(box),
					  &data, &data_size);
		if (data_size == sizeof(*hdr)) {
			hdr = data;
			if (hdr->timestamp == 0)
				return 0;
			/* preserve the original timestamp */
			*new_stamp_r = hdr->timestamp;
			return 1;
		}
		/* cache doesn't exist yet */
	}

	ret = dict_lookup(euser->db, pool_datastack_create(),
			  key, &value);
	if (ret <= 0) {
		if (ret < 0)
			return -1;
		first_save_timestamp(box, new_stamp_r);
		return 0;
	}
	return strcmp(value, "0") != 0 ? 1 : 0;
}

static void
expire_update(struct mailbox *box, const char *key, time_t timestamp)
{
	struct expire_mail_user *euser =
		EXPIRE_USER_CONTEXT(box->storage->user);
	struct dict_transaction_context *dctx;
	struct mail_index_transaction *trans;
	struct expire_mail_index_header hdr;

	dctx = dict_transaction_begin(euser->db);
	dict_set(dctx, key, dec2str(timestamp));
	if (dict_transaction_commit(&dctx) < 0)
		i_error("expire: dict commit failed");
	else if (euser->expire_cache) {
		i_zero(&hdr);
		hdr.timestamp = timestamp;

		trans = mail_index_transaction_begin(box->view,
			MAIL_INDEX_TRANSACTION_FLAG_EXTERNAL);
		mail_index_update_header_ext(trans, expire_get_ext_id(box),
					     0, &hdr, sizeof(hdr));
		if (mail_index_transaction_commit(&trans) < 0)
			i_error("expire: index transaction commit failed");
	}
}

static void first_nonexpunged_timestamp(struct mailbox_transaction_context *t,
					time_t *stamp_r)
{
	struct mail_index_view *view = t->view;
	const struct mail_index_header *hdr;
	struct mail *mail;
	uint32_t seq;

	mail = mail_alloc(t, 0, NULL);

	/* find the first non-expunged mail. we're here because the first
	   mail was expunged, so don't bother checking it. */
	hdr = mail_index_get_header(view);
	for (seq = 2; seq <= hdr->messages_count; seq++) {
		if (!mail_index_is_expunged(view, seq)) {
			mail_set_seq(mail, seq);
			if (mail_get_save_date(mail, stamp_r) == 0)
				break;
		}
	}
	mail_free(&mail);

	if (seq > hdr->messages_count) {
		/* everything expunged */
		*stamp_r = 0;
	}
}

static int
expire_mailbox_transaction_commit(struct mailbox_transaction_context *t,
				  struct mail_transaction_commit_changes *changes_r)
{
	struct mail_user *user = t->box->storage->user;
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(t->box);
	struct expire_transaction_context *xt = EXPIRE_CONTEXT(t);
	struct mailbox *box = t->box;
	time_t new_stamp = 0;
	bool update_dict = FALSE;
	int ret;

	if (xt->first_expunged) {
		/* first mail expunged. dict needs updating. */
		first_nonexpunged_timestamp(t, &new_stamp);
		if (new_stamp == 0 && xt->saves) {
			/* everything was expunged, but also within this
			   transaction a new message was saved */
			new_stamp = ioloop_time;
		}
		if (user->mail_debug) {
			i_debug("expire: Expunging first message in %s, "
				"updating timestamp to %ld",
				box->vname, (long)new_stamp);
		}
		update_dict = TRUE;
	}

	if (xpr_box->module_ctx.super.transaction_commit(t, changes_r) < 0) {
		i_free(xt);
		return -1;
	}
	/* transaction is freed now */
	t = NULL;

	if (xt->first_expunged || xt->saves) T_BEGIN {
		const char *key;

		key = t_strconcat(DICT_EXPIRE_PREFIX,
				  box->storage->user->username, "/",
				  mailbox_get_vname(box), NULL);
		if (xt->first_expunged) {
			/* new_stamp is already set */
		} else {
			i_assert(xt->saves);
			/* saved new mails. dict needs to be updated only if
			   this is the first mail in the database */
			ret = expire_lookup(box, key, &new_stamp);
			if (ret <= 0) {
				/* first time saving here with expire enabled.
				   also handle lookup errors by just assuming
				   it didn't exist */
				if (ret < 0) {
					i_warning("expire: dict lookup failed, "
						  "assuming update is needed");
				}
				update_dict = TRUE;
			} else {
				/* already exists */
			}
			if (user->mail_debug && update_dict) {
				i_debug("expire: Saving first message to %s, "
					"updating timestamp to %ld",
					box->vname, (long)new_stamp);
			}
		}

		if (update_dict)
			expire_update(box, key, new_stamp);
	} T_END;
	i_free(xt);
	return 0;
}

static void
expire_mailbox_transaction_rollback(struct mailbox_transaction_context *t)
{
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(t->box);
	struct expire_transaction_context *xt = EXPIRE_CONTEXT(t);

	xpr_box->module_ctx.super.transaction_rollback(t);
	i_free(xt);
}

static void expire_mail_expunge(struct mail *_mail)
{
	struct mail_private *mail = (struct mail_private *)_mail;
	union mail_module_context *xpr_mail = EXPIRE_MAIL_CONTEXT(mail);
	struct expire_transaction_context *xt =
		EXPIRE_CONTEXT(_mail->transaction);

	if (_mail->seq == 1) {
		/* first mail expunged, database needs to be updated */
		xt->first_expunged = TRUE;
	}
	xpr_mail->super.expunge(_mail);
}

static void expire_mail_allocated(struct mail *_mail)
{
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(_mail->box);
	struct mail_private *mail = (struct mail_private *)_mail;
	struct mail_vfuncs *v = mail->vlast;
	union mail_module_context *xpr_mail;

	if (xpr_box == NULL)
		return;

	xpr_mail = p_new(mail->pool, union mail_module_context, 1);
	xpr_mail->super = *v;
	mail->vlast = &xpr_mail->super;

	v->expunge = expire_mail_expunge;
	MODULE_CONTEXT_SET_SELF(mail, expire_mail_module, xpr_mail);
}

static int expire_save_finish(struct mail_save_context *ctx)
{
	struct expire_transaction_context *xt =
		EXPIRE_CONTEXT(ctx->transaction);
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(ctx->transaction->box);

	xt->saves = TRUE;
	return xpr_box->module_ctx.super.save_finish(ctx);
}

static int
expire_copy(struct mail_save_context *ctx, struct mail *mail)
{
	struct expire_transaction_context *xt =
		EXPIRE_CONTEXT(ctx->transaction);
	struct expire_mailbox *xpr_box = EXPIRE_CONTEXT(ctx->transaction->box);

	xt->saves = TRUE;
	return xpr_box->module_ctx.super.copy(ctx, mail);
}

static void expire_mailbox_allocate_init(struct mailbox *box)
{
	struct mailbox_vfuncs *v = box->vlast;
	struct expire_mailbox *xpr_box;

	xpr_box = p_new(box->pool, struct expire_mailbox, 1);
	xpr_box->module_ctx.super = *v;
	box->vlast = &xpr_box->module_ctx.super;
	xpr_box->expire_ext_id = (uint32_t)-1;

	v->transaction_begin = expire_mailbox_transaction_begin;
	v->transaction_commit = expire_mailbox_transaction_commit;
	v->transaction_rollback = expire_mailbox_transaction_rollback;
	v->save_finish = expire_save_finish;
	v->copy = expire_copy;

	MODULE_CONTEXT_SET(box, expire_storage_module, xpr_box);
}

static void expire_mailbox_allocated(struct mailbox *box)
{
	struct expire_mail_user *euser =
		EXPIRE_USER_CONTEXT(box->storage->user);

	if (euser != NULL && expire_set_lookup(euser->set, box->vname))
		expire_mailbox_allocate_init(box);
}

static void expire_mail_user_deinit(struct mail_user *user)
{
	struct expire_mail_user *euser = EXPIRE_USER_CONTEXT(user);

	dict_deinit(&euser->db);
	expire_set_deinit(&euser->set);

	euser->module_ctx.super.deinit(user);
}

static const char *const *expire_get_patterns(struct mail_user *user)
{
	ARRAY_TYPE(const_string) patterns;
	const char *str;
	char set_name[6+MAX_INT_STRLEN+1];
	unsigned int i;

	t_array_init(&patterns, 16);
	str = mail_user_set_plugin_getenv(user->set, "expire");
	for (i = 2; str != NULL; i++) {
		array_append(&patterns, &str, 1);

		if (i_snprintf(set_name, sizeof(set_name), "expire%u", i) < 0)
			i_unreached();
		str = mail_user_set_plugin_getenv(user->set, set_name);
	}
	array_append_zero(&patterns);
	return array_idx(&patterns, 0);
}

static void expire_mail_namespaces_created(struct mail_namespace *ns)
{
	struct mail_user *user = ns->user;
	struct mail_user_vfuncs *v = user->vlast;
	struct expire_mail_user *euser;
	struct dict *db;
	const char *dict_uri, *error;

	dict_uri = mail_user_plugin_getenv(user, "expire_dict");
	if (mail_user_plugin_getenv(user, "expire") == NULL) {
		if (user->mail_debug)
			i_debug("expire: No expire setting - plugin disabled");
		return;
	}
	if (dict_uri == NULL) {
		i_error("expire plugin: expire_dict setting missing");
		return;
	}

	/* we're using only shared dictionary, the username doesn't matter. */
	if (dict_init(dict_uri, DICT_DATA_TYPE_UINT32, "",
		      user->set->base_dir, &db, &error) < 0) {
		i_error("expire plugin: dict_init(%s) failed: %s",
			dict_uri, error);
		return;
	}

	euser = p_new(user->pool, struct expire_mail_user, 1);
	euser->module_ctx.super = *v;
	user->vlast = &euser->module_ctx.super;
	v->deinit = expire_mail_user_deinit;

	euser->db = db;
	euser->set = expire_set_init(expire_get_patterns(user));
	euser->expire_cache = mail_user_plugin_getenv(user, "expire_cache") != NULL;
	MODULE_CONTEXT_SET(user, expire_mail_user_module, euser);
}

static struct mail_storage_hooks expire_mail_storage_hooks = {
	.mail_namespaces_created = expire_mail_namespaces_created,
	.mailbox_allocated = expire_mailbox_allocated,
	.mail_allocated = expire_mail_allocated
};

void expire_plugin_init(struct module *module)
{
	mail_storage_hooks_add(module, &expire_mail_storage_hooks);
}

void expire_plugin_deinit(void)
{
	mail_storage_hooks_remove(&expire_mail_storage_hooks);
}