package sqlite

import (
	"bytes"
	"context"
	"database/sql"
	"io"
	"sync"
	"time"

	"forge.cadoles.com/arcad/edge/pkg/storage"
	"github.com/gabriel-vasile/mimetype"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type BlobBucket struct {
	name   string
	getDB  getDBFunc
	closed bool
}

// Size implements storage.BlobBucket
func (b *BlobBucket) Size(ctx context.Context) (int64, error) {
	var size int64

	err := b.withTx(ctx, func(tx *sql.Tx) error {
		query := `SELECT SUM(size) FROM blobs WHERE bucket = $1`

		row := tx.QueryRowContext(ctx, query, b.name)

		var nullSize sql.NullInt64

		if err := row.Scan(&nullSize); err != nil {
			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		size = nullSize.Int64

		return nil
	})
	if err != nil {
		return 0, errors.WithStack(err)
	}

	return size, nil
}

// Name implements storage.BlobBucket
func (b *BlobBucket) Name() string {
	return b.name
}

// Close implements storage.BlobBucket
func (b *BlobBucket) Close() error {
	logger.Debug(
		context.Background(), "closing bucket",
		logger.F("alreadyClosed", b.closed),
		logger.F("name", b.name),
	)

	b.closed = true

	return nil
}

// Delete implements storage.BlobBucket
func (b *BlobBucket) Delete(ctx context.Context, id storage.BlobID) error {
	err := b.withTx(ctx, func(tx *sql.Tx) error {
		query := `DELETE FROM blobs WHERE bucket = $1 AND id = $2`
		args := []any{b.name, id}

		logger.Debug(ctx, "executing query", logger.F("query", query), logger.F("args", args))

		if _, err := tx.ExecContext(ctx, query, args...); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return errors.WithStack(err)
	}

	return nil
}

// Get implements storage.BlobBucket
func (b *BlobBucket) Get(ctx context.Context, id storage.BlobID) (storage.BlobInfo, error) {
	var blobInfo *BlobInfo

	err := b.withTx(ctx, func(tx *sql.Tx) error {
		query := `SELECT content_type, mod_time, size FROM blobs WHERE bucket = $1 AND id = $2`
		args := []any{b.name, id}

		logger.Debug(ctx, "executing query", logger.F("query", query), logger.F("args", args))

		row := tx.QueryRowContext(ctx, query, args...)

		var (
			contentType string
			modTime     time.Time
			size        int64
		)

		if err := row.Scan(&contentType, &modTime, &size); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.WithStack(storage.ErrBlobNotFound)
			}

			return errors.WithStack(err)
		}

		if err := row.Err(); err != nil {
			return errors.WithStack(err)
		}

		blobInfo = &BlobInfo{
			id:          id,
			bucket:      b.name,
			contentType: contentType,
			modTime:     modTime,
			size:        size,
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return blobInfo, nil
}

// List implements storage.BlobBucket
func (b *BlobBucket) List(ctx context.Context) ([]storage.BlobInfo, error) {
	var blobs []storage.BlobInfo

	err := b.withTx(ctx, func(tx *sql.Tx) error {
		query := `SELECT id, content_type, mod_time, size FROM blobs WHERE bucket = $1`
		args := []any{b.name}

		logger.Debug(ctx, "executing query", logger.F("query", query), logger.F("args", args))

		rows, err := tx.QueryContext(ctx, query, args...)
		if err != nil {
			return errors.WithStack(err)
		}

		defer func() {
			if err := rows.Close(); err != nil {
				logger.Error(ctx, "could not close rows", logger.E(errors.WithStack(err)))
			}
		}()

		blobs = make([]storage.BlobInfo, 0)

		for rows.Next() {
			var (
				blobID      string
				contentType string
				modTime     time.Time
				size        int64
			)

			if err := rows.Scan(&blobID, &contentType, &modTime, &size); err != nil {
				if errors.Is(err, sql.ErrNoRows) {
					return errors.WithStack(storage.ErrBlobNotFound)
				}

				return errors.WithStack(err)
			}

			blobInfo := &BlobInfo{
				id:          storage.BlobID(blobID),
				bucket:      b.name,
				contentType: contentType,
				modTime:     modTime,
				size:        size,
			}

			blobs = append(blobs, blobInfo)
		}

		if err := rows.Err(); err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return blobs, nil
}

// NewReader implements storage.BlobBucket
func (b *BlobBucket) NewReader(ctx context.Context, id storage.BlobID) (io.ReadSeekCloser, error) {
	if b.closed {
		return nil, errors.WithStack(storage.ErrBucketClosed)
	}

	return &blobReaderCloser{
		id:     id,
		bucket: b.name,
		getDB:  b.getDB,
	}, nil
}

// NewWriter implements storage.BlobBucket
func (b *BlobBucket) NewWriter(ctx context.Context, id storage.BlobID) (io.WriteCloser, error) {
	if b.closed {
		return nil, errors.WithStack(storage.ErrBucketClosed)
	}

	return &blobWriterCloser{
		id:     id,
		bucket: b.name,
		getDB:  b.getDB,
		buf:    bytes.Buffer{},
	}, nil
}

func (b *BlobBucket) withTx(ctx context.Context, fn func(tx *sql.Tx) error) error {
	if b.closed {
		return errors.WithStack(storage.ErrBucketClosed)
	}

	db, err := b.getDB(ctx)
	if err != nil {
		return errors.WithStack(err)
	}

	if err := withTx(ctx, db, fn); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

type blobWriterCloser struct {
	id     storage.BlobID
	bucket string
	getDB  getDBFunc
	buf    bytes.Buffer
	closed bool
}

// Write implements io.WriteCloser
func (wbc *blobWriterCloser) Write(p []byte) (int, error) {
	logger.Debug(
		context.Background(), "writing data to blob",
		logger.F("size", len(p)),
		logger.F("blobID", wbc.id),
		logger.F("bucket", wbc.bucket),
	)

	n, err := wbc.buf.Write(p)
	if err != nil {
		return n, errors.WithStack(err)
	}

	return n, nil
}

// Close implements io.WriteCloser
func (wbc *blobWriterCloser) Close() error {
	ctx := context.Background()

	logger.Debug(
		ctx, "closing writer",
		logger.F("alreadyClosed", wbc.closed),
		logger.F("bucket", wbc.bucket),
		logger.F("blobID", wbc.id),
	)

	if wbc.closed {
		return nil
	}

	err := wbc.withTx(ctx, func(tx *sql.Tx) error {
		query := `
			INSERT INTO blobs (bucket, id, data, content_type, mod_time, size)
			VALUES ($1, $2, $3, $4, $5, $6)
			ON CONFLICT (id, bucket) DO UPDATE SET
			data = $3, content_type = $4, mod_time = $5, size = $6
		`

		data := wbc.buf.Bytes()
		mime := mimetype.Detect(data)
		modTime := time.Now().UTC()

		args := []any{
			wbc.bucket,
			wbc.id,
			data,
			mime.String(),
			modTime,
			len(data),
		}

		logger.Debug(ctx, "executing query", logger.F("query", query))

		_, err := tx.Exec(
			query,
			args...,
		)
		if err != nil {
			return errors.WithStack(err)
		}

		return nil
	})
	if err != nil {
		return errors.WithStack(err)
	}

	wbc.closed = true

	return nil
}

func (wbc *blobWriterCloser) withTx(ctx context.Context, fn func(tx *sql.Tx) error) error {
	if wbc.closed {
		return errors.WithStack(io.ErrClosedPipe)
	}

	db, err := wbc.getDB(ctx)
	if err != nil {
		return errors.WithStack(err)
	}

	if err := withTx(ctx, db, fn); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

type blobReaderCloser struct {
	id     storage.BlobID
	bucket string
	getDB  getDBFunc
	reader bytes.Reader
	once   sync.Once
	closed bool
}

// Read implements io.ReadSeekCloser
func (brc *blobReaderCloser) Read(p []byte) (int, error) {
	var err error

	brc.once.Do(func() {
		err = brc.loadBlob()
	})

	if err != nil {
		return 0, errors.WithStack(err)
	}

	n, err := brc.reader.Read(p)
	if err != nil {
		if errors.Is(err, io.EOF) {
			return n, io.EOF
		}

		return n, errors.WithStack(err)
	}

	return n, nil
}

// Seek implements io.ReadSeekCloser
func (brc *blobReaderCloser) Seek(offset int64, whence int) (int64, error) {
	var err error

	brc.once.Do(func() {
		err = brc.loadBlob()
	})

	if err != nil {
		return 0, errors.WithStack(err)
	}

	n, err := brc.reader.Seek(offset, whence)
	if err != nil {
		return n, errors.WithStack(err)
	}

	return n, nil
}

func (brc *blobReaderCloser) loadBlob() error {
	ctx := context.Background()
	logger.Debug(ctx, "loading blob", logger.F("alreadyClosed", brc.closed))

	err := brc.withTx(ctx, func(tx *sql.Tx) error {
		query := `SELECT data FROM blobs WHERE bucket = $1 AND id = $2`
		row := tx.QueryRow(query, brc.bucket, brc.id)

		var data []byte

		if err := row.Scan(&data); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.WithStack(storage.ErrBlobNotFound)
			}

			return errors.WithStack(err)
		}

		brc.reader = *bytes.NewReader(data)

		return nil
	})
	if err != nil {
		return errors.WithStack(err)
	}

	return nil
}

// Close implements io.ReadSeekCloser
func (brc *blobReaderCloser) Close() error {
	logger.Debug(
		context.Background(), "closing reader",
		logger.F("alreadyClosed", brc.closed),
		logger.F("bucket", brc.bucket),
		logger.F("blobID", brc.id),
	)

	brc.closed = true

	return nil
}

func (brc *blobReaderCloser) withTx(ctx context.Context, fn func(tx *sql.Tx) error) error {
	db, err := brc.getDB(ctx)
	if err != nil {
		return errors.WithStack(err)
	}

	if err := withTx(ctx, db, fn); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

var (
	_ storage.BlobBucket = &BlobBucket{}
	_ storage.BlobInfo   = &BlobInfo{}
	_ io.WriteCloser     = &blobWriterCloser{}
	_ io.ReadSeekCloser  = &blobReaderCloser{}
)