/*
   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 (
	"bytes"
	"context"
	"fmt"
	"image/jpeg"
	"io"
	"sync"
	"time"

	"github.com/disintegration/imaging"
	"github.com/h2non/filetype"
	terminator "github.com/superseriousbusiness/exif-terminator"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/id"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/gotosocial/internal/uris"
)

// ProcessingMedia represents a piece of media that is currently being processed. It exposes
// various functions for retrieving data from the process.
type ProcessingMedia struct {
	media   *gtsmodel.MediaAttachment // processing media attachment details
	recache bool                      // recaching existing (uncached) media
	dataFn  DataFunc                  // load-data function, returns media stream
	postFn  PostDataCallbackFunc      // post data callback function
	err     error                     // error encountered during processing
	manager *manager                  // manager instance (access to db / storage)
	once    sync.Once                 // once ensures processing only occurs once
}

// AttachmentID returns the ID of the underlying media attachment without blocking processing.
func (p *ProcessingMedia) AttachmentID() string {
	return p.media.ID // immutable, safe outside mutex.
}

// LoadAttachment blocks until the thumbnail and fullsize content
// has been processed, and then returns the completed attachment.
func (p *ProcessingMedia) LoadAttachment(ctx context.Context) (*gtsmodel.MediaAttachment, error) {
	// only process once.
	p.once.Do(func() {
		var err error

		defer func() {
			if r := recover(); r != nil {
				if err != nil {
					rOld := r // wrap the panic so we don't lose existing returned error
					r = fmt.Errorf("panic occured after error %q: %v", err.Error(), rOld)
				}

				// Catch any panics and wrap as error.
				err = fmt.Errorf("caught panic: %v", r)
			}

			if err != nil {
				// Store error.
				p.err = err
			}
		}()

		// Attempt to store media and calculate
		// full-size media attachment details.
		if err = p.store(ctx); err != nil {
			return
		}

		// Finish processing by reloading media into
		// memory to get dimension and generate a thumb.
		if err = p.finish(ctx); err != nil {
			return
		}

		if p.recache {
			// Existing attachment we're recaching, so only need to update.
			err = p.manager.db.UpdateByID(ctx, p.media, p.media.ID)
			return
		}

		// New attachment, first time caching.
		err = p.manager.db.Put(ctx, p.media)
		return //nolint shutup linter i like this here
	})

	if p.err != nil {
		return nil, p.err
	}

	return p.media, nil
}

// store calls the data function attached to p if it hasn't been called yet,
// and updates the underlying attachment fields as necessary. It will then stream
// bytes from p's reader directly into storage so that it can be retrieved later.
func (p *ProcessingMedia) store(ctx context.Context) error {
	defer func() {
		if p.postFn == nil {
			return
		}

		// ensure post callback gets called.
		if err := p.postFn(ctx); err != nil {
			log.Errorf("error executing postdata function: %v", err)
		}
	}()

	// Load media from provided data fun
	rc, sz, err := p.dataFn(ctx)
	if err != nil {
		return fmt.Errorf("error executing data function: %w", err)
	}

	defer func() {
		// Ensure data reader gets closed on return.
		if err := rc.Close(); err != nil {
			log.Errorf("error closing data reader: %v", err)
		}
	}()

	// Byte buffer to read file header into.
	// See: https://en.wikipedia.org/wiki/File_format#File_header
	// and https://github.com/h2non/filetype
	hdrBuf := make([]byte, 261)

	// Read the first 261 header bytes into buffer.
	if _, err := io.ReadFull(rc, hdrBuf); err != nil {
		return fmt.Errorf("error reading incoming media: %w", err)
	}

	// Parse file type info from header buffer.
	info, err := filetype.Match(hdrBuf)
	if err != nil {
		return fmt.Errorf("error parsing file type: %w", err)
	}

	// Recombine header bytes with remaining stream
	r := io.MultiReader(bytes.NewReader(hdrBuf), rc)

	switch info.Extension {
	case "mp4":
		p.media.Type = gtsmodel.FileTypeVideo

	case "gif":
		p.media.Type = gtsmodel.FileTypeImage

	case "jpg", "jpeg", "png", "webp":
		p.media.Type = gtsmodel.FileTypeImage
		if sz > 0 {
			// A file size was provided so we can clean exif data from image.
			r, err = terminator.Terminate(r, int(sz), info.Extension)
			if err != nil {
				return fmt.Errorf("error cleaning exif data: %w", err)
			}
		}

	default:
		return fmt.Errorf("unsupported file type: %s", info.Extension)
	}

	// Calculate attachment file path.
	p.media.File.Path = fmt.Sprintf(
		"%s/%s/%s/%s.%s",
		p.media.AccountID,
		TypeAttachment,
		SizeOriginal,
		p.media.ID,
		info.Extension,
	)

	// This shouldn't already exist, but we do a check as it's worth logging.
	if have, _ := p.manager.storage.Has(ctx, p.media.File.Path); have {
		log.Warnf("media already exists at storage path: %s", p.media.File.Path)

		// Attempt to remove existing media at storage path (might be broken / out-of-date)
		if err := p.manager.storage.Delete(ctx, p.media.File.Path); err != nil {
			return fmt.Errorf("error removing media from storage: %v", err)
		}
	}

	// Write the final image reader stream to our storage.
	sz, err = p.manager.storage.PutStream(ctx, p.media.File.Path, r)
	if err != nil {
		return fmt.Errorf("error writing media to storage: %w", err)
	}

	// Set written image size.
	p.media.File.FileSize = int(sz)

	// Fill in remaining attachment data now it's stored.
	p.media.URL = uris.GenerateURIForAttachment(
		p.media.AccountID,
		string(TypeAttachment),
		string(SizeOriginal),
		p.media.ID,
		info.Extension,
	)
	p.media.File.ContentType = info.MIME.Value
	cached := true
	p.media.Cached = &cached

	return nil
}

func (p *ProcessingMedia) finish(ctx context.Context) error {
	// Fetch a stream to the original file in storage.
	rc, err := p.manager.storage.GetStream(ctx, p.media.File.Path)
	if err != nil {
		return fmt.Errorf("error loading file from storage: %w", err)
	}
	defer rc.Close()

	var fullImg *gtsImage

	switch p.media.File.ContentType {
	// .jpeg, .gif, .webp image type
	case mimeImageJpeg, mimeImageGif, mimeImageWebp:
		fullImg, err = decodeImage(rc, imaging.AutoOrientation(true))
		if err != nil {
			return fmt.Errorf("error decoding image: %w", err)
		}

	// .png image (requires ancillary chunk stripping)
	case mimeImagePng:
		fullImg, err = decodeImage(&PNGAncillaryChunkStripper{
			Reader: rc,
		}, imaging.AutoOrientation(true))
		if err != nil {
			return fmt.Errorf("error decoding image: %w", err)
		}

	// .mp4 video type
	case mimeVideoMp4:
		video, err := decodeVideoFrame(rc)
		if err != nil {
			return fmt.Errorf("error decoding video: %w", err)
		}

		// Set video frame as image.
		fullImg = video.frame

		// Set video metadata in attachment info.
		p.media.FileMeta.Original.Duration = &video.duration
		p.media.FileMeta.Original.Framerate = &video.framerate
		p.media.FileMeta.Original.Bitrate = &video.bitrate
	}

	// The image should be in-memory by now.
	if err := rc.Close(); err != nil {
		return fmt.Errorf("error closing file: %w", err)
	}

	// Set full-size dimensions in attachment info.
	p.media.FileMeta.Original.Width = int(fullImg.Width())
	p.media.FileMeta.Original.Height = int(fullImg.Height())
	p.media.FileMeta.Original.Size = int(fullImg.Size())
	p.media.FileMeta.Original.Aspect = fullImg.AspectRatio()

	// Calculate attachment thumbnail file path
	p.media.Thumbnail.Path = fmt.Sprintf(
		"%s/%s/%s/%s.jpg",
		p.media.AccountID,
		TypeAttachment,
		SizeSmall,
		p.media.ID,
	)

	// Get smaller thumbnail image
	thumbImg := fullImg.Thumbnail()

	// Garbage collector, you may
	// now take our large son.
	fullImg = nil

	// Blurhash needs generating from thumb.
	hash, err := thumbImg.Blurhash()
	if err != nil {
		return fmt.Errorf("error generating blurhash: %w", err)
	}

	// Set the attachment blurhash.
	p.media.Blurhash = hash

	// This shouldn't already exist, but we do a check as it's worth logging.
	if have, _ := p.manager.storage.Has(ctx, p.media.Thumbnail.Path); have {
		log.Warnf("thumbnail already exists at storage path: %s", p.media.Thumbnail.Path)

		// Attempt to remove existing thumbnail at storage path (might be broken / out-of-date)
		if err := p.manager.storage.Delete(ctx, p.media.Thumbnail.Path); err != nil {
			return fmt.Errorf("error removing thumbnail from storage: %v", err)
		}
	}

	// Create a thumbnail JPEG encoder stream.
	enc := thumbImg.ToJPEG(&jpeg.Options{
		Quality: 70, // enough for a thumbnail.
	})

	// Stream-encode the JPEG thumbnail image into storage.
	sz, err := p.manager.storage.PutStream(ctx, p.media.Thumbnail.Path, enc)
	if err != nil {
		return fmt.Errorf("error stream-encoding thumbnail to storage: %w", err)
	}

	// Fill in remaining thumbnail now it's stored
	p.media.Thumbnail.ContentType = mimeImageJpeg
	p.media.Thumbnail.URL = uris.GenerateURIForAttachment(
		p.media.AccountID,
		string(TypeAttachment),
		string(SizeSmall),
		p.media.ID,
		"jpg", // always jpeg
	)

	// Set thumbnail dimensions in attachment info.
	p.media.FileMeta.Small = gtsmodel.Small{
		Width:  int(thumbImg.Width()),
		Height: int(thumbImg.Height()),
		Size:   int(thumbImg.Size()),
		Aspect: thumbImg.AspectRatio(),
	}

	// Set written image size.
	p.media.Thumbnail.FileSize = int(sz)

	// Finally set the attachment as processed and update time.
	p.media.Processing = gtsmodel.ProcessingStatusProcessed
	p.media.File.UpdatedAt = time.Now()

	return nil
}

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

	avatar := false
	header := false
	cached := false

	// populate initial fields on the media attachment -- some of these will be overwritten as we proceed
	attachment := &gtsmodel.MediaAttachment{
		ID:                id,
		CreatedAt:         time.Now(),
		UpdatedAt:         time.Now(),
		StatusID:          "",
		URL:               "", // we don't know yet because it depends on the uncalled DataFunc
		RemoteURL:         "",
		Type:              gtsmodel.FileTypeUnknown, // we don't know yet because it depends on the uncalled DataFunc
		FileMeta:          gtsmodel.FileMeta{},
		AccountID:         accountID,
		Description:       "",
		ScheduledStatusID: "",
		Blurhash:          "",
		Processing:        gtsmodel.ProcessingStatusReceived,
		File:              gtsmodel.File{UpdatedAt: time.Now()},
		Thumbnail:         gtsmodel.Thumbnail{UpdatedAt: time.Now()},
		Avatar:            &avatar,
		Header:            &header,
		Cached:            &cached,
	}

	// check if we have additional info to add to the attachment,
	// and overwrite some of the attachment fields if so
	if ai != nil {
		if ai.CreatedAt != nil {
			attachment.CreatedAt = *ai.CreatedAt
		}

		if ai.StatusID != nil {
			attachment.StatusID = *ai.StatusID
		}

		if ai.RemoteURL != nil {
			attachment.RemoteURL = *ai.RemoteURL
		}

		if ai.Description != nil {
			attachment.Description = *ai.Description
		}

		if ai.ScheduledStatusID != nil {
			attachment.ScheduledStatusID = *ai.ScheduledStatusID
		}

		if ai.Blurhash != nil {
			attachment.Blurhash = *ai.Blurhash
		}

		if ai.Avatar != nil {
			attachment.Avatar = ai.Avatar
		}

		if ai.Header != nil {
			attachment.Header = ai.Header
		}

		if ai.FocusX != nil {
			attachment.FileMeta.Focus.X = *ai.FocusX
		}

		if ai.FocusY != nil {
			attachment.FileMeta.Focus.Y = *ai.FocusY
		}
	}

	processingMedia := &ProcessingMedia{
		media:   attachment,
		dataFn:  data,
		postFn:  postData,
		manager: m,
	}

	return processingMedia, nil
}

func (m *manager) preProcessRecache(ctx context.Context, data DataFunc, postData PostDataCallbackFunc, id string) (*ProcessingMedia, error) {
	// get the existing attachment from database.
	attachment, err := m.db.GetAttachmentByID(ctx, id)
	if err != nil {
		return nil, err
	}

	processingMedia := &ProcessingMedia{
		media:   attachment,
		dataFn:  data,
		postFn:  postData,
		manager: m,
		recache: true, // indicate it's a recache
	}

	return processingMedia, nil
}