// Package s3 provides a storagedriver.StorageDriver implementation to
// store blobs in Amazon S3 cloud storage.
//
// This package leverages the crowdmob/goamz client library for interfacing with
// s3.
//
// Because s3 is a key, value store the Stat call does not support last modification
// time for directories (directories are an abstraction for key, value stores)
//
// Keep in mind that s3 guarantees only eventual consistency, so do not assume
// that a successful write will mean immediate access to the data written (although
// in most regions a new object put has guaranteed read after write). The only true
// guarantee is that once you call Stat and receive a certain file size, that much of
// the file is already accessible.
package s3

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/crowdmob/goamz/aws"
	"github.com/crowdmob/goamz/s3"
	"github.com/docker/distribution/storagedriver"
	"github.com/docker/distribution/storagedriver/factory"
)

const driverName = "s3"

// minChunkSize defines the minimum multipart upload chunk size
// S3 API requires multipart upload chunks to be at least 5MB
const minChunkSize = 5 << 20

const defaultChunkSize = 2 * minChunkSize

// listMax is the largest amount of objects you can request from S3 in a list call
const listMax = 1000

//DriverParameters A struct that encapsulates all of the driver parameters after all values have been set
type DriverParameters struct {
	AccessKey     string
	SecretKey     string
	Bucket        string
	Region        aws.Region
	Encrypt       bool
	Secure        bool
	V4Auth        bool
	ChunkSize     int64
	RootDirectory string
}

func init() {
	factory.Register(driverName, &s3DriverFactory{})
}

// s3DriverFactory implements the factory.StorageDriverFactory interface
type s3DriverFactory struct{}

func (factory *s3DriverFactory) Create(parameters map[string]interface{}) (storagedriver.StorageDriver, error) {
	return FromParameters(parameters)
}

// Driver is a storagedriver.StorageDriver implementation backed by Amazon S3
// Objects are stored at absolute keys in the provided bucket
type Driver struct {
	S3            *s3.S3
	Bucket        *s3.Bucket
	ChunkSize     int64
	Encrypt       bool
	RootDirectory string
}

// FromParameters constructs a new Driver with a given parameters map
// Required parameters:
// - accesskey
// - secretkey
// - region
// - bucket
// - encrypt
func FromParameters(parameters map[string]interface{}) (*Driver, error) {
	// Providing no values for these is valid in case the user is authenticating
	// with an IAM on an ec2 instance (in which case the instance credentials will
	// be summoned when GetAuth is called)
	accessKey, ok := parameters["accesskey"]
	if !ok {
		accessKey = ""
	}
	secretKey, ok := parameters["secretkey"]
	if !ok {
		secretKey = ""
	}

	regionName, ok := parameters["region"]
	if !ok || fmt.Sprint(regionName) == "" {
		return nil, fmt.Errorf("No region parameter provided")
	}
	region := aws.GetRegion(fmt.Sprint(regionName))
	if region.Name == "" {
		return nil, fmt.Errorf("Invalid region provided: %v", region)
	}

	bucket, ok := parameters["bucket"]
	if !ok || fmt.Sprint(bucket) == "" {
		return nil, fmt.Errorf("No bucket parameter provided")
	}

	encryptBool := false
	encrypt, ok := parameters["encrypt"]
	if ok {
		encryptBool, ok = encrypt.(bool)
		if !ok {
			return nil, fmt.Errorf("The encrypt parameter should be a boolean")
		}
	}

	secureBool := true
	secure, ok := parameters["secure"]
	if ok {
		secureBool, ok = secure.(bool)
		if !ok {
			return nil, fmt.Errorf("The secure parameter should be a boolean")
		}
	}

	v4AuthBool := true
	v4Auth, ok := parameters["v4auth"]
	if ok {
		v4AuthBool, ok = v4Auth.(bool)
		if !ok {
			return nil, fmt.Errorf("The v4auth parameter should be a boolean")
		}
	}

	chunkSize := int64(defaultChunkSize)
	chunkSizeParam, ok := parameters["chunksize"]
	if ok {
		chunkSize, ok = chunkSizeParam.(int64)
		if !ok || chunkSize < minChunkSize {
			return nil, fmt.Errorf("The chunksize parameter should be a number that is larger than 5*1024*1024")
		}
	}

	rootDirectory, ok := parameters["rootdirectory"]
	if !ok {
		rootDirectory = ""
	}

	params := DriverParameters{
		fmt.Sprint(accessKey),
		fmt.Sprint(secretKey),
		fmt.Sprint(bucket),
		region,
		encryptBool,
		secureBool,
		v4AuthBool,
		chunkSize,
		fmt.Sprint(rootDirectory),
	}

	return New(params)
}

// New constructs a new Driver with the given AWS credentials, region, encryption flag, and
// bucketName
func New(params DriverParameters) (*Driver, error) {
	auth, err := aws.GetAuth(params.AccessKey, params.SecretKey, "", time.Time{})
	if err != nil {
		return nil, err
	}

	if !params.Secure {
		params.Region.S3Endpoint = strings.Replace(params.Region.S3Endpoint, "https", "http", 1)
	}

	s3obj := s3.New(auth, params.Region)
	bucket := s3obj.Bucket(params.Bucket)

	if params.V4Auth {
		s3obj.Signature = aws.V4Signature
	} else {
		if params.Region.Name == "eu-central-1" {
			return nil, fmt.Errorf("The eu-central-1 region only works with v4 authentication")
		}
	}

	// Validate that the given credentials have at least read permissions in the
	// given bucket scope.
	if _, err := bucket.List(strings.TrimRight(params.RootDirectory, "/"), "", "", 1); err != nil {
		return nil, err
	}

	// TODO Currently multipart uploads have no timestamps, so this would be unwise
	// if you initiated a new s3driver while another one is running on the same bucket.
	// multis, _, err := bucket.ListMulti("", "")
	// if err != nil {
	// 	return nil, err
	// }

	// for _, multi := range multis {
	// 	err := multi.Abort()
	// 	//TODO appropriate to do this error checking?
	// 	if err != nil {
	// 		return nil, err
	// 	}
	// }

	return &Driver{
		S3:            s3obj,
		Bucket:        bucket,
		ChunkSize:     params.ChunkSize,
		Encrypt:       params.Encrypt,
		RootDirectory: params.RootDirectory}, nil
}

// Implement the storagedriver.StorageDriver interface

// GetContent retrieves the content stored at "path" as a []byte.
func (d *Driver) GetContent(path string) ([]byte, error) {
	if !storagedriver.PathRegexp.MatchString(path) {
		return nil, storagedriver.InvalidPathError{Path: path}
	}

	content, err := d.Bucket.Get(d.s3Path(path))
	if err != nil {
		return nil, parseError(path, err)
	}
	return content, nil
}

// PutContent stores the []byte content at a location designated by "path".
func (d *Driver) PutContent(path string, contents []byte) error {
	if !storagedriver.PathRegexp.MatchString(path) {
		return storagedriver.InvalidPathError{Path: path}
	}

	return parseError(path, d.Bucket.Put(d.s3Path(path), contents, d.getContentType(), getPermissions(), d.getOptions()))
}

// ReadStream retrieves an io.ReadCloser for the content stored at "path" with a
// given byte offset.
func (d *Driver) ReadStream(path string, offset int64) (io.ReadCloser, error) {
	if !storagedriver.PathRegexp.MatchString(path) {
		return nil, storagedriver.InvalidPathError{Path: path}
	}

	if offset < 0 {
		return nil, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
	}

	headers := make(http.Header)
	headers.Add("Range", "bytes="+strconv.FormatInt(offset, 10)+"-")

	resp, err := d.Bucket.GetResponseWithHeaders(d.s3Path(path), headers)
	if err != nil {
		if s3Err, ok := err.(*s3.Error); ok && s3Err.Code == "InvalidRange" {
			return ioutil.NopCloser(bytes.NewReader(nil)), nil
		}

		return nil, parseError(path, err)
	}
	return resp.Body, nil
}

// WriteStream stores the contents of the provided io.Reader at a
// location designated by the given path. The driver will know it has
// received the full contents when the reader returns io.EOF. The number
// of successfully READ bytes will be returned, even if an error is
// returned. May be used to resume writing a stream by providing a nonzero
// offset. Offsets past the current size will write from the position
// beyond the end of the file.
func (d *Driver) WriteStream(path string, offset int64, reader io.Reader) (totalRead int64, err error) {
	if !storagedriver.PathRegexp.MatchString(path) {
		return 0, storagedriver.InvalidPathError{Path: path}
	}

	if offset < 0 {
		return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
	}

	partNumber := 1
	bytesRead := 0
	var putErrChan chan error
	parts := []s3.Part{}
	var part s3.Part

	multi, err := d.Bucket.InitMulti(d.s3Path(path), d.getContentType(), getPermissions(), d.getOptions())
	if err != nil {
		return 0, err
	}

	buf := make([]byte, d.ChunkSize)
	zeroBuf := make([]byte, d.ChunkSize)

	// We never want to leave a dangling multipart upload, our only consistent state is
	// when there is a whole object at path. This is in order to remain consistent with
	// the stat call.
	//
	// Note that if the machine dies before executing the defer, we will be left with a dangling
	// multipart upload, which will eventually be cleaned up, but we will lose all of the progress
	// made prior to the machine crashing.
	defer func() {
		if putErrChan != nil {
			if putErr := <-putErrChan; putErr != nil {
				err = putErr
			}
		}

		if len(parts) > 0 {
			if multi == nil {
				// Parts should be empty if the multi is not initialized
				panic("Unreachable")
			} else {
				if multi.Complete(parts) != nil {
					multi.Abort()
				}
			}
		}
	}()

	// Fills from 0 to total from current
	fromSmallCurrent := func(total int64) error {
		current, err := d.ReadStream(path, 0)
		if err != nil {
			return err
		}

		bytesRead = 0
		for int64(bytesRead) < total {
			//The loop should very rarely enter a second iteration
			nn, err := current.Read(buf[bytesRead:total])
			bytesRead += nn
			if err != nil {
				if err != io.EOF {
					return err
				}

				break
			}

		}
		return nil
	}

	// Fills from parameter to chunkSize from reader
	fromReader := func(from int64) error {
		bytesRead = 0
		for from+int64(bytesRead) < d.ChunkSize {
			nn, err := reader.Read(buf[from+int64(bytesRead):])
			totalRead += int64(nn)
			bytesRead += nn

			if err != nil {
				if err != io.EOF {
					return err
				}

				break
			}
		}

		if putErrChan == nil {
			putErrChan = make(chan error)
		} else {
			if putErr := <-putErrChan; putErr != nil {
				putErrChan = nil
				return putErr
			}
		}

		go func(bytesRead int, from int64, buf []byte) {
			// parts and partNumber are safe, because this function is the only one modifying them and we
			// force it to be executed serially.
			if bytesRead > 0 {
				part, putErr := multi.PutPart(int(partNumber), bytes.NewReader(buf[0:int64(bytesRead)+from]))
				if putErr != nil {
					putErrChan <- putErr
				}

				parts = append(parts, part)
				partNumber++
			}
			putErrChan <- nil
		}(bytesRead, from, buf)

		buf = make([]byte, d.ChunkSize)
		return nil
	}

	if offset > 0 {
		resp, err := d.Bucket.Head(d.s3Path(path), nil)
		if err != nil {
			if s3Err, ok := err.(*s3.Error); !ok || s3Err.Code != "NoSuchKey" {
				return 0, err
			}
		}

		currentLength := int64(0)
		if err == nil {
			currentLength = resp.ContentLength
		}

		if currentLength >= offset {
			if offset < d.ChunkSize {
				// chunkSize > currentLength >= offset
				if err = fromSmallCurrent(offset); err != nil {
					return totalRead, err
				}

				if err = fromReader(offset); err != nil {
					return totalRead, err
				}

				if totalRead+offset < d.ChunkSize {
					return totalRead, nil
				}
			} else {
				// currentLength >= offset >= chunkSize
				_, part, err = multi.PutPartCopy(partNumber,
					s3.CopyOptions{CopySourceOptions: "bytes=0-" + strconv.FormatInt(offset-1, 10)},
					d.Bucket.Name+"/"+d.s3Path(path))
				if err != nil {
					return 0, err
				}

				parts = append(parts, part)
				partNumber++
			}
		} else {
			// Fills between parameters with 0s but only when to - from <= chunkSize
			fromZeroFillSmall := func(from, to int64) error {
				bytesRead = 0
				for from+int64(bytesRead) < to {
					nn, err := bytes.NewReader(zeroBuf).Read(buf[from+int64(bytesRead) : to])
					bytesRead += nn
					if err != nil {
						return err
					}
				}

				return nil
			}

			// Fills between parameters with 0s, making new parts
			fromZeroFillLarge := func(from, to int64) error {
				bytesRead64 := int64(0)
				for to-(from+bytesRead64) >= d.ChunkSize {
					part, err := multi.PutPart(int(partNumber), bytes.NewReader(zeroBuf))
					if err != nil {
						return err
					}
					bytesRead64 += d.ChunkSize

					parts = append(parts, part)
					partNumber++
				}

				return fromZeroFillSmall(0, (to-from)%d.ChunkSize)
			}

			// currentLength < offset
			if currentLength < d.ChunkSize {
				if offset < d.ChunkSize {
					// chunkSize > offset > currentLength
					if err = fromSmallCurrent(currentLength); err != nil {
						return totalRead, err
					}

					if err = fromZeroFillSmall(currentLength, offset); err != nil {
						return totalRead, err
					}

					if err = fromReader(offset); err != nil {
						return totalRead, err
					}

					if totalRead+offset < d.ChunkSize {
						return totalRead, nil
					}
				} else {
					// offset >= chunkSize > currentLength
					if err = fromSmallCurrent(currentLength); err != nil {
						return totalRead, err
					}

					if err = fromZeroFillSmall(currentLength, d.ChunkSize); err != nil {
						return totalRead, err
					}

					part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf))
					if err != nil {
						return totalRead, err
					}

					parts = append(parts, part)
					partNumber++

					//Zero fill from chunkSize up to offset, then some reader
					if err = fromZeroFillLarge(d.ChunkSize, offset); err != nil {
						return totalRead, err
					}

					if err = fromReader(offset % d.ChunkSize); err != nil {
						return totalRead, err
					}

					if totalRead+(offset%d.ChunkSize) < d.ChunkSize {
						return totalRead, nil
					}
				}
			} else {
				// offset > currentLength >= chunkSize
				_, part, err = multi.PutPartCopy(partNumber,
					s3.CopyOptions{},
					d.Bucket.Name+"/"+d.s3Path(path))
				if err != nil {
					return 0, err
				}

				parts = append(parts, part)
				partNumber++

				//Zero fill from currentLength up to offset, then some reader
				if err = fromZeroFillLarge(currentLength, offset); err != nil {
					return totalRead, err
				}

				if err = fromReader((offset - currentLength) % d.ChunkSize); err != nil {
					return totalRead, err
				}

				if totalRead+((offset-currentLength)%d.ChunkSize) < d.ChunkSize {
					return totalRead, nil
				}
			}

		}
	}

	for {
		if err = fromReader(0); err != nil {
			return totalRead, err
		}

		if int64(bytesRead) < d.ChunkSize {
			break
		}
	}

	return totalRead, nil
}

// Stat retrieves the FileInfo for the given path, including the current size
// in bytes and the creation time.
func (d *Driver) Stat(path string) (storagedriver.FileInfo, error) {
	if !storagedriver.PathRegexp.MatchString(path) {
		return nil, storagedriver.InvalidPathError{Path: path}
	}

	listResponse, err := d.Bucket.List(d.s3Path(path), "", "", 1)
	if err != nil {
		return nil, err
	}

	fi := storagedriver.FileInfoFields{
		Path: path,
	}

	if len(listResponse.Contents) == 1 {
		if listResponse.Contents[0].Key != d.s3Path(path) {
			fi.IsDir = true
		} else {
			fi.IsDir = false
			fi.Size = listResponse.Contents[0].Size

			timestamp, err := time.Parse(time.RFC3339Nano, listResponse.Contents[0].LastModified)
			if err != nil {
				return nil, err
			}
			fi.ModTime = timestamp
		}
	} else if len(listResponse.CommonPrefixes) == 1 {
		fi.IsDir = true
	} else {
		return nil, storagedriver.PathNotFoundError{Path: path}
	}

	return storagedriver.FileInfoInternal{FileInfoFields: fi}, nil
}

// List returns a list of the objects that are direct descendants of the given path.
func (d *Driver) List(path string) ([]string, error) {
	if !storagedriver.PathRegexp.MatchString(path) && path != "/" {
		return nil, storagedriver.InvalidPathError{Path: path}
	}

	if path != "/" && path[len(path)-1] != '/' {
		path = path + "/"
	}
	listResponse, err := d.Bucket.List(d.s3Path(path), "/", "", listMax)
	if err != nil {
		return nil, err
	}

	files := []string{}
	directories := []string{}

	for {
		for _, key := range listResponse.Contents {
			files = append(files, strings.Replace(key.Key, d.s3Path(""), "", 1))
		}

		for _, commonPrefix := range listResponse.CommonPrefixes {
			directories = append(directories, strings.Replace(commonPrefix[0:len(commonPrefix)-1], d.s3Path(""), "", 1))
		}

		if listResponse.IsTruncated {
			listResponse, err = d.Bucket.List(d.s3Path(path), "/", listResponse.NextMarker, listMax)
			if err != nil {
				return nil, err
			}
		} else {
			break
		}
	}

	return append(files, directories...), nil
}

// Move moves an object stored at sourcePath to destPath, removing the original
// object.
func (d *Driver) Move(sourcePath string, destPath string) error {
	if !storagedriver.PathRegexp.MatchString(sourcePath) {
		return storagedriver.InvalidPathError{Path: sourcePath}
	} else if !storagedriver.PathRegexp.MatchString(destPath) {
		return storagedriver.InvalidPathError{Path: destPath}
	}

	/* This is terrible, but aws doesn't have an actual move. */
	_, err := d.Bucket.PutCopy(d.s3Path(destPath), getPermissions(),
		s3.CopyOptions{Options: d.getOptions(), ContentType: d.getContentType()}, d.Bucket.Name+"/"+d.s3Path(sourcePath))
	if err != nil {
		return parseError(sourcePath, err)
	}

	return d.Delete(sourcePath)
}

// Delete recursively deletes all objects stored at "path" and its subpaths.
func (d *Driver) Delete(path string) error {
	if !storagedriver.PathRegexp.MatchString(path) {
		return storagedriver.InvalidPathError{Path: path}
	}

	listResponse, err := d.Bucket.List(d.s3Path(path), "", "", listMax)
	if err != nil || len(listResponse.Contents) == 0 {
		return storagedriver.PathNotFoundError{Path: path}
	}

	s3Objects := make([]s3.Object, listMax)

	for len(listResponse.Contents) > 0 {
		for index, key := range listResponse.Contents {
			s3Objects[index].Key = key.Key
		}

		err := d.Bucket.DelMulti(s3.Delete{Quiet: false, Objects: s3Objects[0:len(listResponse.Contents)]})
		if err != nil {
			return nil
		}

		listResponse, err = d.Bucket.List(d.s3Path(path), "", "", listMax)
		if err != nil {
			return err
		}
	}

	return nil
}

// URLFor returns a URL which may be used to retrieve the content stored at the given path.
// May return an UnsupportedMethodErr in certain StorageDriver implementations.
func (d *Driver) URLFor(path string, options map[string]interface{}) (string, error) {
	if !storagedriver.PathRegexp.MatchString(path) {
		return "", storagedriver.InvalidPathError{Path: path}
	}

	methodString := "GET"
	method, ok := options["method"]
	if ok {
		methodString, ok = method.(string)
		if !ok || (methodString != "GET" && methodString != "HEAD") {
			return "", storagedriver.ErrUnsupportedMethod
		}
	}

	expiresTime := time.Now().Add(20 * time.Minute)
	expires, ok := options["expiry"]
	if ok {
		et, ok := expires.(time.Time)
		if ok {
			expiresTime = et
		}
	}

	return d.Bucket.SignedURLWithMethod(methodString, d.s3Path(path), expiresTime, nil, nil), nil
}

func (d *Driver) s3Path(path string) string {
	return strings.TrimLeft(strings.TrimRight(d.RootDirectory, "/")+path, "/")
}

func parseError(path string, err error) error {
	if s3Err, ok := err.(*s3.Error); ok && s3Err.Code == "NoSuchKey" {
		return storagedriver.PathNotFoundError{Path: path}
	}

	return err
}

func hasCode(err error, code string) bool {
	s3err, ok := err.(*aws.Error)
	return ok && s3err.Code == code
}

func (d *Driver) getOptions() s3.Options {
	return s3.Options{SSE: d.Encrypt}
}

func getPermissions() s3.ACL {
	return s3.Private
}

func (d *Driver) getContentType() string {
	return "application/octet-stream"
}