// Copyright 2021 Security Scorecard Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package data

import (
	"context"
	"errors"
	"fmt"
	"io"
	"time"

	"gocloud.dev/blob"

	// Needed to link in GCP drivers.
	_ "gocloud.dev/blob/gcsblob"

	"github.com/ossf/scorecard/cron/config"
)

const (
	// filePrefixFormat uses ISO 8601 standard, i.e - YYYY-MM-DDTHH:MM:SS.
	// This format guarantees that lexicographically sorted files are chronologically sorted.
	filePrefixFormat = "2006.01.02/150405/"
)

var (
	errShortBlobName = errors.New("input key length is shorter than expected")
	errParseBlobName = errors.New("error parsing input blob name")
)

func GetBlobKeys(ctx context.Context, bucketURL string) ([]string, error) {
	bucket, err := blob.OpenBucket(ctx, bucketURL)
	if err != nil {
		return nil, fmt.Errorf("error from blob.OpenBucket: %w", err)
	}
	defer bucket.Close()

	keys := make([]string, 0)
	iter := bucket.List(nil)
	for {
		next, err := iter.Next(ctx)
		if errors.Is(err, io.EOF) {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("error during iter.Next: %w", err)
		}
		keys = append(keys, next.Key)
	}
	return keys, nil
}

func GetBlobContent(ctx context.Context, bucketURL, key string) ([]byte, error) {
	bucket, err := blob.OpenBucket(ctx, bucketURL)
	if err != nil {
		return nil, fmt.Errorf("error from blob.OpenBucket: %w", err)
	}
	defer bucket.Close()

	keyData, err := bucket.ReadAll(ctx, key)
	if err != nil {
		return keyData, fmt.Errorf("error during bucket.ReadAll: %w", err)
	}
	return keyData, nil
}

func BlobExists(ctx context.Context, bucketURL, key string) (bool, error) {
	bucket, err := blob.OpenBucket(ctx, bucketURL)
	if err != nil {
		return false, fmt.Errorf("error from blob.OpenBucket: %w", err)
	}
	defer bucket.Close()

	ret, err := bucket.Exists(ctx, key)
	if err != nil {
		return ret, fmt.Errorf("error during bucket.Exists: %w", err)
	}
	return ret, nil
}

func WriteToBlobStore(ctx context.Context, bucketURL, filename string, data []byte) error {
	bucket, err := blob.OpenBucket(ctx, bucketURL)
	if err != nil {
		return fmt.Errorf("error from blob.OpenBucket: %w", err)
	}
	defer bucket.Close()

	blobWriter, err := bucket.NewWriter(ctx, filename, nil)
	if err != nil {
		return fmt.Errorf("error from bucket.NewWriter: %w", err)
	}
	if _, err = blobWriter.Write(data); err != nil {
		return fmt.Errorf("error from blobWriter.Write: %w", err)
	}
	if err := blobWriter.Close(); err != nil {
		return fmt.Errorf("error from blobWriter.Close: %w", err)
	}
	return nil
}

func GetBlobFilename(filename string, datetime time.Time) string {
	return datetime.Format(filePrefixFormat) + filename
}

func GetShardNumFilename(datetime time.Time) string {
	return GetBlobFilename(config.ShardNumFilename, datetime)
}

func GetTransferStatusFilename(datetime time.Time) string {
	return GetBlobFilename(config.TransferStatusFilename, datetime)
}

func ParseBlobFilename(key string) (time.Time, string, error) {
	if len(key) < len(filePrefixFormat) {
		return time.Now(), "", fmt.Errorf("%w: %s", errShortBlobName, key)
	}
	prefix := key[:len(filePrefixFormat)]
	objectName := key[len(filePrefixFormat):]
	t, err := time.Parse(filePrefixFormat, prefix)
	if err != nil {
		return t, "", fmt.Errorf("%w: %v", errParseBlobName, err)
	}
	return t, objectName, nil
}