package storage

import (
	"context"
	"errors"
	"io"
)

// Errors of the media store.
var (
	// ErrNoSuchMedia means no media, or no thumbnail, is stored under the
	// given name.
	ErrNoSuchMedia = errors.New("no such media")

	// ErrMediaExists is CreateMedia's answer for a media ID that is taken.
	ErrMediaExists = errors.New("media already exists")

	// ErrMediaUploaded is CompleteUpload's answer for media whose content
	// has already been uploaded: content, once stored, never changes.
	ErrMediaUploaded = errors.New("media content already uploaded")
)

// Media is the metadata of one piece of content: uploaded here, or fetched
// from the server it was uploaded to and kept.
type Media struct {
	// Origin is the server name in the mxc:// URI: this server for an
	// upload, another for cached remote media.
	Origin  string
	MediaID string

	// ContentType is the Content-Type the content was uploaded with,
	// parameters included.
	ContentType string

	// UploadName is the file name the uploader gave, or "".
	UploadName string

	// Size is the content's length in bytes.
	Size int64

	// SHA256 names the content in the blob store: its SHA-256, in
	// lower-case hex. Empty while the media is pending.
	SHA256 string

	// UserID is the uploader; "" for remote media.
	UserID string

	CreatedAtMS int64

	// Pending is set for an ID handed out by /create whose content has
	// not been uploaded yet. Pending media expires at ExpiresAtMS.
	Pending     bool
	ExpiresAtMS int64
}

// MediaContent is what CompleteUpload fills in on pending media.
type MediaContent struct {
	ContentType string
	UploadName  string
	Size        int64
	SHA256      string
}

// Thumbnail is one generated (or, for remote media, fetched) thumbnail.
type Thumbnail struct {
	Origin  string
	MediaID string

	// Width, Height and Method are the size the thumbnail was made for —
	// one of the configured sizes — not the size of the image itself,
	// which for "scale" keeps the original's aspect ratio.
	Width  int
	Height int
	Method string

	ContentType string
	Size        int64
	SHA256      string
	CreatedAtMS int64
}

// MediaStore is the mediaapi store: the metadata of local and cached
// remote media and of their thumbnails. The content itself is in a
// BlobStore.
type MediaStore interface {
	// CreateMedia records media: an upload, a pending upload or a remote
	// fetch. A taken (origin, media ID) is ErrMediaExists.
	CreateMedia(ctx context.Context, m Media) error

	// Media reads one media record, pending or not.
	Media(ctx context.Context, origin, mediaID string) (Media, error)

	// CompleteUpload stores the content of pending media and clears its
	// pending flag. It is ErrNoSuchMedia for an unknown ID and
	// ErrMediaUploaded for media that is not pending.
	CompleteUpload(ctx context.Context, origin, mediaID string, content MediaContent) error

	// PendingUploads counts a user's pending media that has not expired
	// by nowMS.
	PendingUploads(ctx context.Context, userID string, nowMS int64) (int, error)

	// DeleteExpiredUploads removes pending media that expired before
	// nowMS, reporting how many.
	DeleteExpiredUploads(ctx context.Context, nowMS int64) (int, error)

	// Thumbnail reads the thumbnail made for one size.
	Thumbnail(ctx context.Context, origin, mediaID string, width, height int, method string) (Thumbnail, error)

	// StoreThumbnail records a thumbnail, replacing one stored for the
	// same size.
	StoreThumbnail(ctx context.Context, t Thumbnail) error

	// MediaUsage totals what a user has uploaded to this server. Pending
	// reservations count for nothing until their content arrives.
	MediaUsage(ctx context.Context, origin, userID string) (MediaUsage, error)

	// MediaQuota returns the quota the admin API set for a user, and
	// whether one is set.
	MediaQuota(ctx context.Context, userID string) (int64, bool, error)

	// SetMediaQuota sets a user's quota; 0 is no limit.
	SetMediaQuota(ctx context.Context, userID string, maxBytes int64) error

	// DeleteMediaQuota returns a user to the configured default.
	DeleteMediaQuota(ctx context.Context, userID string) error
}

// MediaUsage is what one user's uploads add up to.
type MediaUsage struct {
	Count int
	Bytes int64
}

// ErrNoSuchBlob means the blob store holds nothing under a hash.
var ErrNoSuchBlob = errors.New("no such blob")

// ErrBlobTooLarge means content passed the limit it was stored with.
var ErrBlobTooLarge = errors.New("content is larger than allowed")

// BlobInfo describes stored content.
type BlobInfo struct {
	// SHA256 is the lower-case hex SHA-256 of the content, and its name in
	// the store.
	SHA256 string
	Size   int64
}

// BlobStore keeps media content, addressed by its SHA-256. The same bytes
// uploaded twice are stored once.
type BlobStore interface {
	// Put stores what r yields, up to limit bytes; more is
	// ErrBlobTooLarge and stores nothing.
	Put(ctx context.Context, r io.Reader, limit int64) (BlobInfo, error)

	// Open reads stored content.
	Open(ctx context.Context, sha256 string) (io.ReadSeekCloser, error)

	// Delete removes stored content. Deleting what is not there is not an
	// error.
	Delete(ctx context.Context, sha256 string) error
}

// BlobProvider is implemented by a storage driver that brings its own
// BlobStore. PocketBase will (PLAN.md section 4: its filesystem
// abstraction puts media on local disk or S3); a driver that does not is
// given the local filesystem store.
type BlobProvider interface {
	Blobs() BlobStore
}