package storage

import (
	"fmt"
	"io"
	"strings"

	"github.com/pkg/errors"
	"gopkg.in/yaml.v2"
)

// StorageProvider is the type of provider used for storage if not leveraging a file implementation.
type StorageProvider string

const (
	S3      StorageProvider = "S3"
	GCS     StorageProvider = "GCS"
	AZURE   StorageProvider = "AZURE"
	CLUSTER StorageProvider = "CLUSTER"
)

// StorageConfig is the configuration type used as the "parent" configuration. It contains a type, which will
// specify the bucket storage implementation, and a configuration object specific to that storage implementation.
type StorageConfig struct {
	Type   StorageProvider `yaml:"type"`
	Config interface{}     `yaml:"config"`
	Prefix string          `yaml:"prefix"`
}

// NewBucketStorage initializes and returns new Storage implementation leveraging the storage provider
// configuration. This configuration type uses the layout provided in thanos: https://thanos.io/tip/thanos/storage.md/
func NewBucketStorage(config []byte) (Storage, error) {
	storageConfig := &StorageConfig{}
	if err := yaml.UnmarshalStrict(config, storageConfig); err != nil {
		return nil, errors.Wrap(err, "parsing config YAML file")
	}

	// Because the Config property is specific to the storage implementation, we'll marshal back into yaml, and allow
	// the specific implementation to unmarshal back into a concrete configuration type.
	config, err := yaml.Marshal(storageConfig.Config)
	if err != nil {
		return nil, errors.Wrap(err, "marshal content of storage configuration")
	}

	var storage Storage
	switch strings.ToUpper(string(storageConfig.Type)) {
	case string(S3):
		storage, err = NewS3Storage(config)
	case string(GCS):
		storage, err = NewGCSStorage(config)
	case string(AZURE):
		storage, err = NewAzureStorage(config)
	case string(CLUSTER):
		storage, err = NewClusterStorage(config)
	default:
		return nil, errors.Errorf("storage with type %s is not supported", storageConfig.Type)
	}
	if err != nil {
		return nil, errors.Wrap(err, fmt.Sprintf("create %s client", storageConfig.Type))
	}

	if storageConfig.Prefix != "" {
		return NewPrefixedBucketStorage(storage, storageConfig.Prefix)
	}

	return storage, nil
}

// asyncPipeWriter wraps *io.PipeWriter so that Close() blocks until the
// background upload goroutine finishes and surfaces any upload error to the caller.
type asyncPipeWriter struct {
	*io.PipeWriter
	done <-chan error
}

// newAsyncPipeWriter creates a new async pipe writer that implements io.WriteCloser that
// handles asynchronous closing of an io.PipeWriter
func newAsyncPipeWriter(writer *io.PipeWriter, done <-chan error) *asyncPipeWriter {
	return &asyncPipeWriter{
		PipeWriter: writer,
		done:       done,
	}
}

// Close propagates any errors that were received on the pipewriter or reader.
func (apw *asyncPipeWriter) Close() error {
	if err := apw.PipeWriter.Close(); err != nil {
		return err
	}
	return <-apw.done
}

// trimLeading removes a leading / from the file name
func trimLeading(file string) string {
	if len(file) == 0 {
		return file
	}

	if file[0] == '/' {
		return file[1:]
	}
	return file
}

// trimName removes the leading directory prefix
func trimName(file string) string {
	slashIndex := strings.LastIndex(file, "/")
	if slashIndex < 0 {
		return file
	}

	name := file[slashIndex+1:]
	return name
}