;; This Source Code Form is subject to the terms of the Mozilla Public
;; License, v. 2.0. If a copy of the MPL was not distributed with this
;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
;;
;; Copyright (c) KALEIDOS INC Sucursal en España SL

(ns app.tasks.file-gc
  "A maintenance task that is responsible of: purge unused file media,
  clean unused object thumbnails and remove old file thumbnails.  The
  file is eligible to be garbage collected after some period of
  inactivity (the default threshold is 72h)."
  (:require
   [app.binfile.cleaner :as bfl]
   [app.binfile.common :as bfc]
   [app.common.files.helpers :as cfh]
   [app.common.files.validate :as cfv]
   [app.common.logging :as l]
   [app.common.thumbnails :as thc]
   [app.common.time :as ct]
   [app.common.types.components-list :as ctkl]
   [app.common.types.file :as ctf]
   [app.common.types.shape-tree :as ctt]
   [app.config :as cf]
   [app.db :as db]
   [app.features.fdata :as feat.fdata]
   [app.features.file-snapshots :as fsnap]
   [app.storage :as sto]
   [app.worker :as wrk]
   [integrant.core :as ig]))

(declare get-file)

(def ^:private sql:mark-file-media-object-deleted
  "UPDATE file_media_object
      SET deleted_at = ?
    WHERE file_id = ? AND id != ALL(?::uuid[])
   RETURNING id")

(def xf:collect-used-media
  (comp
   (map :data)
   (mapcat cfh/collect-used-media)))

(defn- clean-file-media!
  "Performs the garbage collection of file media objects."
  [{:keys [::db/conn ::timestamp] :as cfg} {:keys [id] :as file}]
  (let [used-media
        (fsnap/reduce-snapshots cfg id xf:collect-used-media conj #{})

        used-media
        (into used-media xf:collect-used-media [file])

        used-media
        (db/create-array conn "uuid" used-media)

        unused-media
        (->> (db/exec! conn [sql:mark-file-media-object-deleted timestamp id used-media])
             (into #{} (map :id)))]

    (doseq [id unused-media]
      (l/trc :obj "media-object"
             :file-id (str id)
             :id (str id)))

    file))

(def ^:private sql:mark-file-object-thumbnails-deleted
  "UPDATE file_tagged_object_thumbnail
      SET deleted_at = ?
    WHERE file_id = ? AND object_id != ALL(?::text[])
   RETURNING object_id")

(defn- clean-file-object-thumbnails!
  [{:keys [::db/conn ::timestamp]} {:keys [data] :as file}]
  (let [file-id (:id file)
        using   (->> (vals (:pages-index data))
                     (into #{} (comp
                                (mapcat (fn [{:keys [id objects]}]
                                          (->> (ctt/get-frames objects)
                                               (map #(assoc % :page-id id)))))
                                (mapcat (fn [{:keys [id page-id]}]
                                          (list
                                           (thc/fmt-object-id file-id page-id id "frame")
                                           (thc/fmt-object-id file-id page-id id "component")))))))

        ids    (into-array String using)
        unused (->> (db/exec! conn [sql:mark-file-object-thumbnails-deleted timestamp file-id ids])
                    (into #{} (map :object-id)))]

    (doseq [object-id unused]
      (l/trc :obj "object-thumbnail"
             :file-id (str file-id)
             :id object-id))

    file))

(def ^:private sql:mark-file-thumbnails-deleted
  "UPDATE file_thumbnail
      SET deleted_at = ?
    WHERE file_id = ? AND revn < ?
   RETURNING revn")

(defn- clean-file-thumbnails!
  [{:keys [::db/conn ::timestamp]} {:keys [id revn] :as file}]
  (let [unused (->> (db/exec! conn [sql:mark-file-thumbnails-deleted timestamp id revn])
                    (into #{} (map :revn)))]

    (doseq [revn unused]
      (l/trc :obj "thumbnail"
             :file-id (str id)
             :revn revn))

    file))

(def ^:private sql:get-files-for-library
  "SELECT f.id
     FROM file AS f
     LEFT JOIN file_library_rel AS fl ON (fl.file_id = f.id)
    WHERE fl.library_file_id = ?
      AND f.deleted_at IS null
    ORDER BY f.modified_at ASC")

(defn- get-used-components
  "Given a file and a set of components marked for deletion, return a
  filtered set of component ids that are still un use"
  [components library-id {:keys [data]}]
  (filter #(ctf/used-in? data library-id % :component) components))

(defn- clean-deleted-components!
  "Performs the garbage collection of unreferenced deleted components."
  [{:keys [::db/conn] :as cfg} {:keys [data] :as file}]
  (let [file-id (:id file)

        deleted-components
        (ctkl/deleted-components-seq data)

        file-xform
        (mapcat (partial get-used-components deleted-components file-id))

        library-xform
        (comp
         (map :id)
         (map #(bfc/get-file cfg % :realize? true :read-only? true))
         file-xform)

        used-remote
        (->> (db/plan conn [sql:get-files-for-library file-id] {:fetch-size 1})
             (transduce library-xform conj #{}))

        used-local
        (into #{} file-xform [file])

        unused
        (transduce bfc/xf-map-id disj
                   (into #{} bfc/xf-map-id deleted-components)
                   (concat used-remote used-local))

        file
        (update file :data
                (fn [data]
                  (reduce (fn [data id]
                            (l/trc :obj "component"
                                   :file-id (str file-id)
                                   :id (str id))
                            (ctkl/delete-component data id))
                          data
                          unused)))]

    file))

(def ^:private sql:mark-deleted-data-fragments
  "UPDATE file_data
      SET deleted_at = ?
    WHERE file_id = ?
      AND id != ALL(?::uuid[])
      AND type = 'fragment'
      AND deleted_at IS NULL
   RETURNING id")

(def ^:private xf:collect-pointers
  (comp (map :data)
        (mapcat feat.fdata/get-used-pointer-ids)))

(defn- clean-fragments!
  [{:keys [::db/conn ::timestamp]} {:keys [id] :as file}]
  (let [used   (into #{} xf:collect-pointers [file])
        unused (->> (db/exec! conn [sql:mark-deleted-data-fragments timestamp id
                                    (db/create-array conn "uuid" used)])
                    (into #{} bfc/xf-map-id))]

    (doseq [id unused]
      (l/trc :obj "fragment"
             :file-id (str id)
             :id (str id)))

    file))

(defn- clean-media!
  [cfg file]
  (let [file (->> file
                  (clean-deleted-components! cfg)
                  (clean-file-media! cfg)
                  (clean-file-thumbnails! cfg)
                  (clean-file-object-thumbnails! cfg))]
    (cfv/validate-file-schema! file)
    file))

(defn get-file
  [cfg {:keys [file-id revn]}]
  (let [file (bfc/get-file cfg file-id
                           :realize? true
                           :skip-locked? true
                           :lock-for-update? true)]

    ;; We should ensure that the scheduled file and the procesing file
    ;; has not changed since schedule, for this reason we check the
    ;; revn from props with the revn from retrieved file from database
    (when (or (nil? revn) (= revn (:revn file)))
      file)))

;; FIXME: we should skip files that does not match the revn on the
;; props and add proper schema for this task props

(defn- process-file!
  [cfg {:keys [file-id] :as props}]
  (if-let [file (get-file cfg props)]
    (let [file (->> file
                    (bfl/clean-file)
                    (clean-media! cfg)
                    (clean-fragments! cfg))
          file (assoc file :has-media-trimmed true)]
      (bfc/update-file! cfg file)
      true)

    (do
      (l/dbg :hint "skip cleaning, criteria does not match" :file-id (str file-id))
      false)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; HANDLER
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defmethod ig/assert-key ::handler
  [_ params]
  (assert (db/pool? (::db/pool params)) "expected a valid database pool")
  (assert (sto/valid-storage? (::sto/storage params)) "expected valid storage to be provided"))

(defmethod ig/init-key ::handler
  [_ cfg]
  (fn [{:keys [props] :as task}]
    (try
      (-> cfg
          (assoc ::db/rollback (:rollback? props))
          (db/tx-run! (fn [{:keys [::db/conn] :as cfg}]
                        (let [cfg        (-> cfg
                                             (update ::sto/storage sto/configure conn)
                                             (assoc ::timestamp (ct/now)))
                              processed? (process-file! cfg props)]

                          (when (and processed? (contains? cf/flags :tiered-file-data-storage))
                            (wrk/submit! (-> cfg
                                             (assoc ::wrk/task :offload-file-data)
                                             (assoc ::wrk/params props)
                                             (assoc ::wrk/priority 10)
                                             (assoc ::wrk/delay 1000))))
                          processed?))))
      (catch Throwable cause
        (l/err :hint "error on cleaning file"
               :file-id (str (:file-id props))
               :cause cause)))))