/* Copyright (c) 2005-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "unichar.h"
#include "istream.h"
#include "mail-namespace.h"
#include "mail-search-build.h"
#include "quota-private.h"
#include "quota-plugin.h"
#include "trash-plugin.h"

#include <unistd.h>
#include <fcntl.h>

#define INIT_TRASH_MAILBOX_COUNT 4
#define MAX_RETRY_COUNT 3

#define TRASH_USER_CONTEXT(obj) \
	MODULE_CONTEXT(obj, trash_user_module)
#define TRASH_USER_CONTEXT_REQUIRE(obj) \
	MODULE_CONTEXT_REQUIRE(obj, trash_user_module)

struct trash_mailbox {
	const char *name;
	int priority; /* lower number = higher priority */

	struct mail_namespace *ns;

	/* temporarily set while cleaning: */
	struct mailbox *box;
	struct mailbox_transaction_context *trans;
	struct mail_search_context *search_ctx;
	struct mail *mail;
};

struct trash_user {
	union mail_user_module_context module_ctx;

	const char *config_file;
	/* ordered by priority, highest first */
	ARRAY(struct trash_mailbox) trash_boxes;
};

const char *trash_plugin_version = DOVECOT_ABI_VERSION;

static MODULE_CONTEXT_DEFINE_INIT(trash_user_module,
				  &mail_user_module_register);
static enum quota_alloc_result (*trash_next_quota_test_alloc)(
		struct quota_transaction_context *, uoff_t,
		const char **error_r);

static int trash_clean_mailbox_open(struct trash_mailbox *trash)
{
	struct mail_search_args *search_args;

	trash->box = mailbox_alloc(trash->ns->list, trash->name, 0);
	if (mailbox_open(trash->box) < 0) {
		mailbox_free(&trash->box);
		return 0;
	}

	if (mailbox_sync(trash->box, MAILBOX_SYNC_FLAG_FULL_READ) < 0)
		return -1;

	trash->trans = mailbox_transaction_begin(trash->box, 0, __func__);

	search_args = mail_search_build_init();
	mail_search_build_add_all(search_args);
	trash->search_ctx = mailbox_search_init(trash->trans,
						search_args, NULL,
						MAIL_FETCH_PHYSICAL_SIZE |
						MAIL_FETCH_RECEIVED_DATE, NULL);
	mail_search_args_unref(&search_args);

	return mailbox_search_next(trash->search_ctx, &trash->mail) ? 1 : 0;
}

static int trash_clean_mailbox_get_next(struct trash_mailbox *trash,
					time_t *received_time_r)
{
	int ret;

	if (trash->mail == NULL) {
		if (trash->box == NULL)
			ret = trash_clean_mailbox_open(trash);
		else {
			ret = mailbox_search_next(trash->search_ctx,
						  &trash->mail) ? 1 : 0;
		}
		if (ret <= 0) {
			*received_time_r = 0;
			return ret;
		}
	}

	if (mail_get_received_date(trash->mail, received_time_r) < 0)
		return -1;
	return 1;
}

static int trash_try_clean_mails(struct quota_transaction_context *ctx,
				 uint64_t size_needed,
				 unsigned int count_needed)
{
	struct trash_user *tuser = TRASH_USER_CONTEXT_REQUIRE(ctx->quota->user);
	struct trash_mailbox *trashes;
	struct event_reason *reason;
	unsigned int i, j, count, oldest_idx;
	time_t oldest, received = 0;
	uint64_t size, size_expunged = 0;
	unsigned int expunged_count = 0;
	int ret = 0;

	reason = event_reason_begin("trash:clean");

	trashes = array_get_modifiable(&tuser->trash_boxes, &count);
	for (i = 0; i < count; ) {
		/* expunge oldest mails first in all trash boxes with
		   same priority */
		oldest_idx = count;
		oldest = (time_t)-1;
		for (j = i; j < count; j++) {
			if (trashes[j].priority != trashes[i].priority)
				break;

			ret = trash_clean_mailbox_get_next(&trashes[j],
							   &received);
			if (ret < 0)
				goto err;
			if (ret > 0) {
				if (oldest == (time_t)-1 || received < oldest) {
					oldest = received;
					oldest_idx = j;
				}
			}
		}

		if (oldest_idx < count) {
			if (mail_get_physical_size(trashes[oldest_idx].mail,
						   &size) < 0) {
				/* maybe expunged already? */
				trashes[oldest_idx].mail = NULL;
				continue;
			}

			mail_expunge(trashes[oldest_idx].mail);
			expunged_count++;
			size_expunged += size;
			if (size_expunged >= size_needed &&
			    expunged_count >= count_needed)
				break;
			trashes[oldest_idx].mail = NULL;
		} else {
			/* find more mails from next priority's mailbox */
			i = j;
		}
	}

err:
	for (i = 0; i < count; i++) {
		struct trash_mailbox *trash = &trashes[i];

		if (trash->box == NULL)
			continue;

		trash->mail = NULL;
		(void)mailbox_search_deinit(&trash->search_ctx);

		if (size_expunged >= size_needed &&
		    expunged_count >= count_needed) {
			(void)mailbox_transaction_commit(&trash->trans);
			(void)mailbox_sync(trash->box, 0);
		} else {
			/* couldn't get enough space, don't expunge anything */
                        mailbox_transaction_rollback(&trash->trans);
		}

		mailbox_free(&trash->box);
	}
	event_reason_end(&reason);

	if (size_expunged < size_needed) {
		e_debug(ctx->quota->user->event,
			"trash plugin: Failed to remove enough messages "
			"(needed %"PRIu64" bytes, expunged only %"PRIu64" bytes)",
			size_needed, size_expunged);
		return 0;
	}
	if (expunged_count < count_needed) {
		e_debug(ctx->quota->user->event,
			"trash plugin: Failed to remove enough messages "
			"(needed %u messages, expunged only %u messages)",
			count_needed, expunged_count);
		return 0;
	}

	if (ctx->bytes_over > 0) {
		/* user is over quota. drop the over-bytes first. */
		i_assert(ctx->bytes_over <= size_expunged);
		size_expunged -= ctx->bytes_over;
		ctx->bytes_over = 0;
	}
	if (ctx->count_over > 0) {
		/* user is over quota. drop the over-count first. */
		i_assert(ctx->count_over <= expunged_count);
		expunged_count -= ctx->count_over;
		ctx->count_over = 0;
	}

	if (ctx->bytes_ceil > ((uint64_t)-1 - size_expunged)) {
		ctx->bytes_ceil = (uint64_t)-1;
	} else {
		ctx->bytes_ceil += size_expunged;
	}
	if (ctx->count_ceil < ((uint64_t)-1 - expunged_count)) {
		ctx->count_ceil = (uint64_t)-1;
	} else {
		ctx->count_ceil += expunged_count;
	}
	return 1;
}

static enum quota_alloc_result
trash_quota_test_alloc(struct quota_transaction_context *ctx,
		       uoff_t size, const char **error_r)
{
	int i;
	uint64_t size_needed = 0;
	unsigned int count_needed = 0;

	for (i = 0; ; i++) {
		enum quota_alloc_result ret;
		ret = trash_next_quota_test_alloc(ctx, size, error_r);
		if (ret != QUOTA_ALLOC_RESULT_OVER_QUOTA) {
			if (ret == QUOTA_ALLOC_RESULT_OVER_QUOTA_LIMIT &&
			    ctx->quota->user->mail_debug)
				i_debug("trash plugin: Mail is larger than "
					"quota, won't even try to handle");
			return ret;
		}

		if (i == MAX_RETRY_COUNT) {
			/* trash_try_clean_mails() should have returned 0 if
			   it couldn't get enough space, but allow retrying
			   it a couple of times if there was some extra space
			   that was needed.. */
			break;
		}

		if (ctx->bytes_ceil != (uint64_t)-1 &&
		    ctx->bytes_ceil < size + ctx->bytes_over)
			size_needed = size + ctx->bytes_over - ctx->bytes_ceil;
		if (ctx->count_ceil != (uint64_t)-1 &&
		    ctx->count_ceil < 1 + ctx->count_over)
			count_needed = 1 + ctx->count_over - ctx->count_ceil;

		/* not enough space. try deleting some from mailbox. */
		if (trash_try_clean_mails(ctx, size_needed, count_needed) <= 0) {
			*error_r = t_strdup_printf(
				"Allocating %"PRIuUOFF_T" bytes would exceed quota", size);
			return QUOTA_ALLOC_RESULT_OVER_QUOTA;
		}
	}
	*error_r = t_strdup_printf(
		"Allocating %"PRIuUOFF_T" bytes would exceed quota", size);
	return QUOTA_ALLOC_RESULT_OVER_QUOTA;
}

static bool trash_find_storage(struct mail_user *user,
			       struct trash_mailbox *trash)
{
	struct mail_namespace *ns;

	ns = mail_namespace_find(user->namespaces, trash->name);
	if ((ns->flags & NAMESPACE_FLAG_UNUSABLE) != 0)
		return FALSE;

	trash->ns = ns;
	return TRUE;
}

static int trash_mailbox_priority_cmp(const struct trash_mailbox *t1,
				      const struct trash_mailbox *t2)
{
	return t1->priority - t2->priority;
}

static int read_configuration(struct mail_user *user, const char *path)
{
	struct trash_user *tuser = TRASH_USER_CONTEXT_REQUIRE(user);
	struct istream *input;
	const char *line, *name;
	struct trash_mailbox *trash;
	int fd, ret = 0;

	fd = open(path, O_RDONLY);
	if (fd == -1) {
		i_error("trash plugin: open(%s) failed: %m", path);
		return -1;
	}

	p_array_init(&tuser->trash_boxes, user->pool, INIT_TRASH_MAILBOX_COUNT);

	input = i_stream_create_fd(fd, SIZE_MAX);
	i_stream_set_return_partial_line(input, TRUE);
	while ((line = i_stream_read_next_line(input)) != NULL) {
		/* <priority> <mailbox name> */
		name = strchr(line, ' ');
		if (name == NULL || name[1] == '\0' || *line == '#')
			continue;

		trash = array_append_space(&tuser->trash_boxes);
		trash->name = p_strdup(user->pool, name+1);
		if (str_to_int(t_strdup_until(line, name),
			       &trash->priority) < 0) {
			i_error("trash: Invalid priority for mailbox '%s'",
				trash->name);
			ret = -1;
		}

		if (!uni_utf8_str_is_valid(trash->name)) {
			i_error("trash: Mailbox name not UTF-8: %s",
				trash->name);
			ret = -1;
		}
		if (!trash_find_storage(user, trash)) {
			i_error("trash: Namespace not found for mailbox '%s'",
				trash->name);
			ret = -1;
		}

		e_debug(user->event, "trash plugin: Added '%s' with priority %d",
			trash->name, trash->priority);
	}
	i_stream_destroy(&input);
	i_close_fd(&fd);

	array_sort(&tuser->trash_boxes, trash_mailbox_priority_cmp);
	return ret;
}

static void
trash_mail_user_created(struct mail_user *user)
{
	struct quota_user *quser = QUOTA_USER_CONTEXT(user);
	struct trash_user *tuser;
	const char *env;

	env = mail_user_plugin_getenv(user, "trash");
	if (env == NULL) {
		e_debug(user->event, "trash: No trash setting - plugin disabled");
	} else if (quser == NULL) {
		i_error("trash plugin: quota plugin not initialized");
	} else {
		tuser = p_new(user->pool, struct trash_user, 1);
		tuser->config_file = env;
		MODULE_CONTEXT_SET(user, trash_user_module, tuser);
	}
}

static void
trash_mail_namespaces_created(struct mail_namespace *namespaces)
{
	struct mail_user *user = namespaces->user;
	struct trash_user *tuser = TRASH_USER_CONTEXT(user);
	struct quota_user *quser = QUOTA_USER_CONTEXT(user);

	if (tuser != NULL && read_configuration(user, tuser->config_file) == 0) {
		i_assert(quser != NULL);
		trash_next_quota_test_alloc =
			quser->quota->set->test_alloc;
		quser->quota->set->test_alloc = trash_quota_test_alloc;
	}
}

static struct mail_storage_hooks trash_mail_storage_hooks = {
	.mail_user_created = trash_mail_user_created,
	.mail_namespaces_created = trash_mail_namespaces_created,
};

void trash_plugin_init(struct module *module)
{
	mail_storage_hooks_add(module, &trash_mail_storage_hooks);
}

void trash_plugin_deinit(void)
{
	mail_storage_hooks_remove(&trash_mail_storage_hooks);
}

const char *trash_plugin_dependencies[] = { "quota", NULL };