package main

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path"
	"path/filepath"
	"time"

	"github.com/bugsnag/bugsnag-go/v2"
	"github.com/minio/minio-go/v7"
)

func (s *service) backupTangledKnot(ctx context.Context) {
	err := s.backupKnotDB(ctx)
	if err != nil {
		bugsnag.Notify(fmt.Errorf("backup knot db: %w", err))
		slog.Error("failed to backup knot db", "error", err)
	}
	err = s.backupKnotRepos(ctx)
	if err != nil {
		bugsnag.Notify(fmt.Errorf("backup knot db: %w", err))
		slog.Error("failed to backup knot db", "error", err)
	}

	slog.Info("finished tangled knot backup")
}

func (s *service) backupKnotDB(ctx context.Context) error {
	dir := os.Getenv("TANGLED_KNOT_DATABASE_DIRECTORY")
	if dir == "" {
		slog.Info("TANGLED_KNOT_DATABASE_DIRECTORY env not set - skipping knot DB backup")
	}

	filename := path.Join(s.blobDir, fmt.Sprintf("%d-knot.zip", time.Now().UnixMilli()))
	f, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("creating temp file: %w", err)
	}
	defer func() {
		f.Close()

		err = os.Remove(filename)
		if err != nil {
			slog.Error("failed to delete knot db zip file after uploading", "error", err, "filename", f.Name())
			metadata := bugsnag.MetaData{
				"file": {
					"filename": f.Name(),
				},
			}
			bugsnag.Notify(fmt.Errorf("delete knot db zip file after uploading: %w", err), metadata)
		}
	}()

	compress(dir, f)

	// reset the reader back to the start so that the minio upload can read the data that's been written.
	_, err = f.Seek(0, 0)
	if err != nil {
		return fmt.Errorf("setting seek on written file: %w", err)
	}

	fi, err := f.Stat()
	if err != nil {
		return fmt.Errorf("stat written file: %w", err)
	}

	_, err = s.minioClient.PutObject(ctx, s.bucketName, "knot-db.zip", f, fi.Size(), minio.PutObjectOptions{})
	if err != nil {
		return fmt.Errorf("put knot db zip file to bucket: %w", err)
	}
	return nil
}

func (s *service) backupKnotRepos(ctx context.Context) error {
	dir := os.Getenv("TANGLED_KNOT_REPOSITORY_DIRECTORY")
	if dir == "" {
		slog.Info("TANGLED_KNOT_REPOSITORY_DIRECTORY env not set - skipping knot repo backup")
	}

	filename := path.Join(s.blobDir, fmt.Sprintf("%d-knot-repos.zip", time.Now().UnixMilli()))
	f, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("creating temp file: %w", err)
	}
	defer func() {
		f.Close()

		err = os.Remove(filename)
		if err != nil {
			slog.Error("failed to delete knot repos zip file after uploading", "error", err, "filename", f.Name())
			metadata := bugsnag.MetaData{
				"file": {
					"filename": f.Name(),
				},
			}
			bugsnag.Notify(fmt.Errorf("delete knot repos zip file after uploading: %w", err), metadata)
		}
	}()

	compress(dir, f)

	// reset the reader back to the start so that the minio upload can read the data that's been written.
	_, err = f.Seek(0, 0)
	if err != nil {
		return fmt.Errorf("setting seek on written file: %w", err)
	}

	fi, err := f.Stat()
	if err != nil {
		return fmt.Errorf("stat written file: %w", err)
	}

	_, err = s.minioClient.PutObject(ctx, s.bucketName, "knot-repos.zip", f, fi.Size(), minio.PutObjectOptions{})
	if err != nil {
		return fmt.Errorf("put knot repo file to bucket: %w", err)
	}
	return nil
}

func compress(src string, writer io.Writer) error {
	zipWriter := gzip.NewWriter(writer)
	tarWriter := tar.NewWriter(zipWriter)

	filepath.Walk(src, func(file string, fi os.FileInfo, err error) error {
		header, err := tar.FileInfoHeader(fi, file)
		if err != nil {
			return err
		}

		// must provide real name
		// (see https://golang.org/src/archive/tar/common.go?#L626)
		header.Name = filepath.ToSlash(file)

		if err := tarWriter.WriteHeader(header); err != nil {
			return err
		}
		// if not a dir, write file content
		if !fi.IsDir() {
			data, err := os.Open(file)
			if err != nil {
				return err
			}
			if _, err := io.Copy(tarWriter, data); err != nil {
				return err
			}
		}

		return nil
	})

	// produce tar
	if err := tarWriter.Close(); err != nil {
		return err
	}
	// produce gzip
	if err := zipWriter.Close(); err != nil {
		return err
	}

	return nil
}