// Copyright (C) 2020 Storj Labs, Inc.
// See LICENSE for copying information.

package metabase

import (
	"math"
	"sort"
	"strconv"
	"strings"

	"github.com/zeebo/errs"

	"storj.io/common/storj"
	"storj.io/common/uuid"
)

// Error is the default error for metabase.
var Error = errs.Class("metabase")

// Common constants for segment keys.
const (
	Delimiter        = '/'
	LastSegmentName  = "l"
	LastSegmentIndex = uint32(math.MaxUint32)
)

// MaxListLimit is the maximum number of items the client can request for listing.
const MaxListLimit = 1000

const batchsizeLimit = 1000

// BucketPrefix consists of <project id>/<bucket name>.
type BucketPrefix string

// BucketLocation defines a bucket that belongs to a project.
type BucketLocation struct {
	ProjectID  uuid.UUID
	BucketName string
}

// ParseBucketPrefix parses BucketPrefix.
func ParseBucketPrefix(prefix BucketPrefix) (BucketLocation, error) {
	elements := strings.Split(string(prefix), "/")
	if len(elements) != 2 {
		return BucketLocation{}, Error.New("invalid prefix %q", prefix)
	}

	projectID, err := uuid.FromString(elements[0])
	if err != nil {
		return BucketLocation{}, Error.Wrap(err)
	}

	return BucketLocation{
		ProjectID:  projectID,
		BucketName: elements[1],
	}, nil
}

// Verify object location fields.
func (loc BucketLocation) Verify() error {
	switch {
	case loc.ProjectID.IsZero():
		return ErrInvalidRequest.New("ProjectID missing")
	case loc.BucketName == "":
		return ErrInvalidRequest.New("BucketName missing")
	}
	return nil
}

// Prefix converts bucket location into bucket prefix.
func (loc BucketLocation) Prefix() BucketPrefix {
	return BucketPrefix(loc.ProjectID.String() + "/" + loc.BucketName)
}

// ObjectKey is an encrypted object key encoded using Path Component Encoding.
// It is not ascii safe.
type ObjectKey string

// ObjectLocation is decoded object key information.
type ObjectLocation struct {
	ProjectID  uuid.UUID
	BucketName string
	ObjectKey  ObjectKey
}

// Bucket returns bucket location this object belongs to.
func (obj ObjectLocation) Bucket() BucketLocation {
	return BucketLocation{
		ProjectID:  obj.ProjectID,
		BucketName: obj.BucketName,
	}
}

// Verify object location fields.
func (obj ObjectLocation) Verify() error {
	switch {
	case obj.ProjectID.IsZero():
		return ErrInvalidRequest.New("ProjectID missing")
	case obj.BucketName == "":
		return ErrInvalidRequest.New("BucketName missing")
	case len(obj.ObjectKey) == 0:
		return ErrInvalidRequest.New("ObjectKey missing")
	}
	return nil
}

// SegmentKey is an encoded metainfo key. This is used as the key in pointerdb key-value store.
type SegmentKey []byte

// SegmentLocation is decoded segment key information.
type SegmentLocation struct {
	ProjectID  uuid.UUID
	BucketName string
	ObjectKey  ObjectKey
	Position   SegmentPosition
}

// Bucket returns bucket location this segment belongs to.
func (seg SegmentLocation) Bucket() BucketLocation {
	return BucketLocation{
		ProjectID:  seg.ProjectID,
		BucketName: seg.BucketName,
	}
}

// Object returns the object location associated with this segment location.
func (seg SegmentLocation) Object() ObjectLocation {
	return ObjectLocation{
		ProjectID:  seg.ProjectID,
		BucketName: seg.BucketName,
		ObjectKey:  seg.ObjectKey,
	}
}

// ParseSegmentKey parses an segment key into segment location.
func ParseSegmentKey(encoded SegmentKey) (SegmentLocation, error) {
	elements := strings.SplitN(string(encoded), "/", 4)
	if len(elements) < 4 {
		return SegmentLocation{}, Error.New("invalid key %q", encoded)
	}

	projectID, err := uuid.FromString(elements[0])
	if err != nil {
		return SegmentLocation{}, Error.New("invalid key %q", encoded)
	}

	var index uint32
	if elements[1] == LastSegmentName {
		index = LastSegmentIndex
	} else {
		numstr := strings.TrimPrefix(elements[1], "s")
		// remove prefix `s` from segment index we got
		parsed, err := strconv.ParseUint(numstr, 10, 64)
		if err != nil {
			return SegmentLocation{}, Error.New("invalid %q, segment number %q", string(encoded), elements[1])
		}
		index = uint32(parsed)
	}

	return SegmentLocation{
		ProjectID:  projectID,
		BucketName: elements[2],
		Position:   SegmentPosition{Index: index},
		ObjectKey:  ObjectKey(elements[3]),
	}, nil
}

// Encode converts segment location into a segment key.
func (seg SegmentLocation) Encode() SegmentKey {
	segment := LastSegmentName
	if seg.Position.Index != LastSegmentIndex {
		segment = "s" + strconv.FormatUint(seg.Position.Encode(), 10)
	}
	return SegmentKey(storj.JoinPaths(
		seg.ProjectID.String(),
		segment,
		seg.BucketName,
		string(seg.ObjectKey),
	))
}

// ObjectStream uniquely defines an object and stream.
//
// TODO: figure out whether ther's a better name.
type ObjectStream struct {
	ProjectID  uuid.UUID
	BucketName string
	ObjectKey  ObjectKey
	Version    Version
	StreamID   uuid.UUID
}

// Verify object stream fields.
func (obj *ObjectStream) Verify() error {
	switch {
	case obj.ProjectID.IsZero():
		return ErrInvalidRequest.New("ProjectID missing")
	case obj.BucketName == "":
		return ErrInvalidRequest.New("BucketName missing")
	case len(obj.ObjectKey) == 0:
		return ErrInvalidRequest.New("ObjectKey missing")
	case obj.Version < 0:
		return ErrInvalidRequest.New("Version invalid: %v", obj.Version)
	case obj.StreamID.IsZero():
		return ErrInvalidRequest.New("StreamID missing")
	}
	return nil
}

// Location returns object location.
func (obj *ObjectStream) Location() ObjectLocation {
	return ObjectLocation{
		ProjectID:  obj.ProjectID,
		BucketName: obj.BucketName,
		ObjectKey:  obj.ObjectKey,
	}
}

// SegmentPosition is segment part and index combined.
type SegmentPosition struct {
	Part  uint32
	Index uint32
}

// SegmentPositionFromEncoded decodes an uint64 into a SegmentPosition.
func SegmentPositionFromEncoded(v uint64) SegmentPosition {
	return SegmentPosition{
		Part:  uint32(v >> 32),
		Index: uint32(v),
	}
}

// Encode encodes a segment position into an uint64, that can be stored in a database.
func (pos SegmentPosition) Encode() uint64 { return uint64(pos.Part)<<32 | uint64(pos.Index) }

// Less returns whether pos should before b.
func (pos SegmentPosition) Less(b SegmentPosition) bool { return pos.Encode() < b.Encode() }

// Version is used to uniquely identify objects with the same key.
type Version int64

// NextVersion means that the version should be chosen automatically.
const NextVersion = Version(0)

// ObjectStatus defines the statuses that the object might be in.
type ObjectStatus byte

const (
	// Pending means that the object is being uploaded or that the client failed during upload.
	// The failed upload may be continued in the future.
	Pending = ObjectStatus(1)
	// Committed means that the object is finished and should be visible for general listing.
	Committed = ObjectStatus(3)

	pendingStatus   = "1"
	committedStatus = "3"
)

// Pieces defines information for pieces.
type Pieces []Piece

// Verify verifies pieces.
func (p Pieces) Verify() error {
	if len(p) == 0 {
		return ErrInvalidRequest.New("pieces missing")
	}

	currentPiece := p[0]
	if currentPiece.StorageNode == (storj.NodeID{}) {
		return ErrInvalidRequest.New("piece number %d is missing storage node id", currentPiece.Number)
	}

	for _, piece := range p[1:] {
		switch {
		case piece.Number == currentPiece.Number:
			return ErrInvalidRequest.New("duplicated piece number %d", piece.Number)
		case piece.Number < currentPiece.Number:
			return ErrInvalidRequest.New("pieces should be ordered")
		case piece.StorageNode == (storj.NodeID{}):
			return ErrInvalidRequest.New("piece number %d is missing storage node id", piece.Number)
		}
		currentPiece = piece
	}
	return nil
}

// Equal checks if Pieces structures are equal.
func (p Pieces) Equal(pieces Pieces) bool {
	if len(p) != len(pieces) {
		return false
	}

	first := make(Pieces, len(p))
	second := make(Pieces, len(p))

	copy(first, p)
	copy(second, pieces)

	sort.Slice(first, func(i, j int) bool {
		return first[i].Number < first[j].Number
	})
	sort.Slice(second, func(i, j int) bool {
		return second[i].Number < second[j].Number
	})

	for i := range first {
		if first[i].Number != second[i].Number {
			return false
		}
		if first[i].StorageNode != second[i].StorageNode {
			return false
		}
	}

	return true
}

// Len is the number of pieces.
func (p Pieces) Len() int { return len(p) }

// Less reports whether the piece with
// index i should sort before the piece with index j.
func (p Pieces) Less(i, j int) bool { return p[i].Number < p[j].Number }

// Swap swaps the pieces with indexes i and j.
func (p Pieces) Swap(i, j int) { p[i], p[j] = p[j], p[i] }

// Piece defines information for a segment piece.
type Piece struct {
	Number      uint16
	StorageNode storj.NodeID
}