/*
   GoToSocial
   Copyright (C) 2021-2023 GoToSocial Authors admin@gotosocial.org

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package media

import (
	"context"
	"fmt"

	"github.com/superseriousbusiness/gotosocial/internal/concurrency"
	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/storage"
)

var SupportedMIMETypes = []string{
	mimeImageJpeg,
	mimeImageGif,
	mimeImagePng,
	mimeImageWebp,
	mimeVideoMp4,
}

var SupportedEmojiMIMETypes = []string{
	mimeImageGif,
	mimeImagePng,
}

// Manager provides an interface for managing media: parsing, storing, and retrieving media objects like photos, videos, and gifs.
type Manager interface {
	// Stop stops the underlying worker pool of the manager. It should be called
	// when closing GoToSocial in order to cleanly finish any in-progress jobs.
	// It will block until workers are finished processing.
	Stop() error

	/*
		PROCESSING FUNCTIONS
	*/

	// ProcessMedia begins the process of decoding and storing the given data as an attachment.
	// It will return a pointer to a ProcessingMedia struct upon which further actions can be performed, such as getting
	// the finished media, thumbnail, attachment, etc.
	//
	// data should be a function that the media manager can call to return a reader containing the media data.
	//
	// postData will be called after data has been called; it can be used to clean up any remaining resources.
	// The provided function can be nil, in which case it will not be executed.
	//
	// accountID should be the account that the media belongs to.
	//
	// ai is optional and can be nil. Any additional information about the attachment provided will be put in the database.
	ProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error)
	// ProcessEmoji begins the process of decoding and storing the given data as an emoji.
	// It will return a pointer to a ProcessingEmoji struct upon which further actions can be performed, such as getting
	// the finished media, thumbnail, attachment, etc.
	//
	// data should be a function that the media manager can call to return a reader containing the emoji data.
	//
	// postData will be called after data has been called; it can be used to clean up any remaining resources.
	// The provided function can be nil, in which case it will not be executed.
	//
	// shortcode should be the emoji shortcode without the ':'s around it.
	//
	// id is the database ID that should be used to store the emoji.
	//
	// uri is the ActivityPub URI/ID of the emoji.
	//
	// ai is optional and can be nil. Any additional information about the emoji provided will be put in the database.
	//
	// If refresh is true, this indicates that the emoji image has changed and should be updated.
	ProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error)
	// RecacheMedia refetches, reprocesses, and recaches an existing attachment that has been uncached via pruneRemote.
	RecacheMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, attachmentID string) (*ProcessingMedia, error)

	/*
		PRUNING/UNCACHING FUNCTIONS
	*/

	// PruneAll runs all of the below pruning/uncacheing functions, and then cleans up any resulting
	// empty directories from the storage driver. It can be called as a shortcut for calling the below
	// pruning functions one by one.
	//
	// If blocking is true, then any errors encountered during the prune will be combined + returned to
	// the caller. If blocking is false, the prune is run in the background and errors are just logged
	// instead.
	PruneAll(ctx context.Context, mediaCacheRemoteDays int, blocking bool) error
	// UncacheRemote uncaches all remote media attachments older than the given amount of days.
	//
	// In this context, uncacheing means deleting media files from storage and marking the attachment
	// as cached=false in the database.
	//
	// If 'dry' is true, then only a dry run will be performed: nothing will actually be changed.
	//
	// The returned int is the amount of media that was/would be uncached by this function.
	UncacheRemote(ctx context.Context, olderThanDays int, dry bool) (int, error)
	// PruneUnusedRemote prunes unused/out of date headers and avatars cached on this instance.
	//
	// The returned int is the amount of media that was pruned by this function.
	PruneUnusedRemote(ctx context.Context, dry bool) (int, error)
	// PruneUnusedLocal prunes unused media attachments that were uploaded by
	// a user on this instance, but never actually attached to a status, or attached but
	// later detached.
	//
	// The returned int is the amount of media that was pruned by this function.
	PruneUnusedLocal(ctx context.Context, dry bool) (int, error)
	// PruneOrphaned prunes files that exist in storage but which do not have a corresponding
	// entry in the database.
	//
	// If dry is true, then nothing will be changed, only the amount that *would* be removed
	// is returned to the caller.
	PruneOrphaned(ctx context.Context, dry bool) (int, error)

	/*
		REFETCHING FUNCTIONS
		Useful when data loss has occurred.
	*/

	// RefetchEmojis iterates through remote emojis (for the given domain, or all if domain is empty string).
	//
	// For each emoji, the manager will check whether both the full size and static images are present in storage.
	// If not, the manager will refetch and reprocess full size and static images for the emoji.
	//
	// The provided DereferenceMedia function will be used when it's necessary to refetch something this way.
	RefetchEmojis(ctx context.Context, domain string, dereferenceMedia DereferenceMedia) (int, error)
}

type manager struct {
	db           db.DB
	storage      *storage.Driver
	emojiWorker  *concurrency.WorkerPool[*ProcessingEmoji]
	mediaWorker  *concurrency.WorkerPool[*ProcessingMedia]
	stopCronJobs func() error
}

// NewManager returns a media manager with the given db and underlying storage.
//
// A worker pool will also be initialized for the manager, to ensure that only
// a limited number of media will be processed in parallel. The numbers of workers
// is determined from the $GOMAXPROCS environment variable (usually no. CPU cores).
// See internal/concurrency.NewWorkerPool() documentation for further information.
func NewManager(database db.DB, storage *storage.Driver) (Manager, error) {
	m := &manager{
		db:      database,
		storage: storage,
	}

	// Prepare the media worker pool.
	m.mediaWorker = concurrency.NewWorkerPool[*ProcessingMedia](-1, 10)
	m.mediaWorker.SetProcessor(func(ctx context.Context, media *ProcessingMedia) error {
		if _, err := media.LoadAttachment(ctx); err != nil {
			return fmt.Errorf("error loading media %s: %v", media.AttachmentID(), err)
		}
		return nil
	})

	// Prepare the emoji worker pool.
	m.emojiWorker = concurrency.NewWorkerPool[*ProcessingEmoji](-1, 10)
	m.emojiWorker.SetProcessor(func(ctx context.Context, emoji *ProcessingEmoji) error {
		if _, err := emoji.LoadEmoji(ctx); err != nil {
			return fmt.Errorf("error loading emoji %s: %v", emoji.EmojiID(), err)
		}
		return nil
	})

	// Start the worker pools.
	if err := m.mediaWorker.Start(); err != nil {
		return nil, err
	}
	if err := m.emojiWorker.Start(); err != nil {
		return nil, err
	}

	// Schedule cron job(s) for clean up.
	if err := scheduleCleanup(m); err != nil {
		return nil, err
	}

	return m, nil
}

func (m *manager) ProcessMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, accountID string, ai *AdditionalMediaInfo) (*ProcessingMedia, error) {
	processingMedia, err := m.preProcessMedia(ctx, data, postData, accountID, ai)
	if err != nil {
		return nil, err
	}
	m.mediaWorker.Queue(processingMedia)
	return processingMedia, nil
}

func (m *manager) ProcessEmoji(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, shortcode string, id string, uri string, ai *AdditionalEmojiInfo, refresh bool) (*ProcessingEmoji, error) {
	processingEmoji, err := m.preProcessEmoji(ctx, data, postData, shortcode, id, uri, ai, refresh)
	if err != nil {
		return nil, err
	}
	m.emojiWorker.Queue(processingEmoji)
	return processingEmoji, nil
}

func (m *manager) RecacheMedia(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, attachmentID string) (*ProcessingMedia, error) {
	processingRecache, err := m.preProcessRecache(ctx, data, postData, attachmentID)
	if err != nil {
		return nil, err
	}
	m.mediaWorker.Queue(processingRecache)
	return processingRecache, nil
}

func (m *manager) Stop() error {
	// Stop worker pools.
	mediaErr := m.mediaWorker.Stop()
	emojiErr := m.emojiWorker.Stop()

	var cronErr error
	if m.stopCronJobs != nil {
		cronErr = m.stopCronJobs()
	}

	if mediaErr != nil {
		return mediaErr
	} else if emojiErr != nil {
		return emojiErr
	}

	return cronErr
}