// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package interfaces

import (
	"time"

	wire "v.io/v23/services/syncbase"
	"v.io/v23/security/access"
)

const (
	NoGroupId = GroupId("")
)

// TODO(hpucha): These are not final yet. This is an intermediate step.

const (
	// NodeRec type log record adds a new node in the dag.
	NodeRec = byte(0)

	// LinkRec type log record adds a new link in the dag. Link records are
	// added when a conflict is resolved by picking the local or the remote
	// version as the resolution of a conflict, instead of creating a new
	// version.
	LinkRec = byte(1)
)

// GenVector is the generation vector for any syncable entity, which maps each
// device id to its last locally known generation in the scope of that entity.
type GenVector map[uint64]uint64

// Knowledge is a mapping of syncable entities to their generation
// vectors. These syncable entities could be data prefixes relative to a
// Database id, or syncgroup oids.
type Knowledge map[string]GenVector

// LogRecMetadata represents the metadata of a single log record that is
// exchanged between two peers. Each log record represents a change made to an
// object in the store.
//
// TODO(hpucha): Add readset/scanset. Look into sending tx metadata only once
// per transaction.
type LogRecMetadata struct {
	// Log related information.
	Id      uint64 // device id that created the log record.
	Gen     uint64 // generation number for the log record.
	RecType byte   // type of log record.

	// Object related information.

	// Id of the object that was updated. This id is relative to Application
	// and Database names and is the store key for a particular row in a
	// collection.
	ObjId      string
	CurVers    string    // current version number of the object.
	Parents    []string  // 0, 1 or 2 parent versions that the current version is derived from.
	UpdTime    time.Time // timestamp when the update is generated.
	Delete     bool      // indicates whether the update resulted in object being deleted from the store.
	BatchId    uint64    // unique id of the Batch this update belongs to.
	BatchCount uint64    // number of objects in the Batch.
}

// LogRec represents the on-wire representation of an entire log record: its
// metadata and data. Value is the actual value of a store object.
type LogRec struct {
	Metadata LogRecMetadata
	Value    any
}

// GroupId is a globally unique syncgroup ID.
// It is a hash of the syncgroup name.
type GroupId string

// Possible states for a syncgroup.
type SyncgroupStatus enum {
	// Indicates that a syncgroup is operational, but publishing to the
	// remote server is pending.
	PublishPending

	// Indicates that the syncgroup is operational, but the publishing
	// failed.
	PublishRejected

	// Indicates that the syncgroup is operational and published.
	Running
}

// Syncgroup contains the state of a syncgroup.
type Syncgroup struct {
	Id          wire.Id                         // the relative syncgroup Id chosen by app
	SpecVersion string                          // version on syncgroup spec for concurrency control
	Spec        wire.SyncgroupSpec              // app-given specification
	Creator     string                          // Creator's Vanadium name
	DbId        wire.Id                         // Globally unique database id
	Status      SyncgroupStatus                 // Status of the syncgroup
	Joiners     map[string]SyncgroupMemberState // map of joiners to their metadata
}

// SyncgroupMemberState contains information about a joiner and the internal bookkeeping
// state required for resolving conflicts on this joiner's join/leave activity.
type SyncgroupMemberState struct {
    // Timestamp of when the member last joined/left the syncgroup. This timestamp is updated
    // even when an existing member rejoins a syncgroup. Represented as Unix time.
    WhenUpdated int64

    // If set then this record indicates that this member has left the group. The SyncgroupMember
    // entry is retained after a delete so that it can be used during conflict resolution, when
    // one node indicates that the member has left the group and another says that the member
    // is still in the group.
    HasLeft    bool

    // Information supplied when requesting a join.
    MemberInfo  wire.SyncgroupMemberInfo
}

// CollectionPerms represent the persistent, synced permissions of a Collection.
// Existence of CollectionPerms in the store determines existence of the
// Collection.
// Note: Since CollectionPerms is synced and conflict resolved, the sync
// protocol needs to be aware of it. Any potential additions to synced
// Collection metadata should be written to a separate, synced key prefix,
// written in the same transaction with CollectionPerms and incorporated into
// the sync protocol. All persistent Collection metadata should be synced;
// local-only metadata is acceptable only if optional (e.g. stats).
type CollectionPerms access.Permissions

// DeltaReq contains a request to sync either data or syncgroup metadata for a
// Database.
type DeltaReq union {
	Sgs  SgDeltaReq
	Data DataDeltaReq
}

// DataDeltaReq contains the initiator's genvectors and the set of syncgroups it
// is interested in within a database when requesting deltas for that database.
type DataDeltaReq struct {
	DbId wire.Id
	SgIds   set[GroupId]
	Gvs     Knowledge
}

// SgDeltaReq contains the initiator's genvectors for the syncgroups it is
// interested in within a database when requesting deltas for those syncgroups.
type SgDeltaReq struct {
	DbId wire.Id
	Gvs     Knowledge // Contains a genvector per syncgroup.
}

// DeltaResp contains the responder's genvectors or the missing log records
// returned in response to an initiator's request for deltas for a Database.
type DeltaResp union {
	Rec     LogRec
	Gvs     Knowledge
}

// DeltaFinalResp contains the data returned at the end of a GetDeltas call.
type DeltaFinalResp struct {
	SgPriorities SgPriorities
}

// ChunkHash contains the hash of a chunk that is part of a blob's recipe.
type ChunkHash struct {
	Hash []byte
}

// ChunkData contains the data of a chunk.
type ChunkData struct {
	Data []byte
}

// TimeReq contains the send timestamp from the requester.
type TimeReq struct {
	SendTs time.Time
}

// TimeResp contains information needed by the requester to estimate the
// difference between the two vclocks and to decide whether to incorporate the
// peer's vclock data.
type TimeResp struct {
	OrigTs time.Time // when we sent request
	RecvTs time.Time // when peer received request
	SendTs time.Time // when peer sent response

	// NTP server timestamp from the most recent NTP sync, or zero value if none.
	// Note, the NTP sync may have been performed by some peer device.
	LastNtpTs time.Time

	// Number of reboots since last NTP sync, accumulated across all hops of p2p
	// clock sync.
	NumReboots uint16

	// Number of sync hops between peer's device and its source of LastNtpTs.
	NumHops uint16
}

// A SgPriority represents data used to decide whether to transfer blob ownership
// between two devices.
type SgPriority struct {
	DevType    int32     // device type (BlobDevTypeServer, BlobDevTypeNormal, BlobDevTypeLeaf)
	Distance   float32   // mean number of hops from a server-quality member of the syncgroup
	ServerTime time.Time // when data from a server-quality member reached this device
}

// A SgPriorities maps syncgroup IDs to SgPriority structures.  It is sent and
// received in GetDeltas calls to allow the participants to assess who has
// higher priorities for keeping blobs.
type SgPriorities map[GroupId]SgPriority

// A BlobSharesBySyncgroup maps syncgroup IDs to integer share numbers that a
// syncbase instance may have for a blob.
type BlobSharesBySyncgroup map[GroupId]int32

// A LocationData is the information known about a particular location in a Signpost.
// TODO(m3b): Include mount table information to allow the location to be found.
type LocationData struct {
	WhenSeen time.Time // most recent time when blob thought to have been at location
	IsProxy  bool      // whether the location is a likely proxy to another syncgroup
	IsServer bool      // whether the location is a server that may be revealed outside its syncgroup
}

// A PeerToLocationDataMap is a map from syncbase peer names to LocationData structures.
type PeerToLocationDataMap map[string]LocationData

// A Signpost is a hint to syncbase of the device on which a blob may be found.
// It represents the data known about a blob even when the blob itself is not
// present on the device.
type Signpost struct {
	Locations    PeerToLocationDataMap   // Maps name of syncbase that probably has the blob to a LocationData
        SgIds        set[GroupId]            // SyncGroups through which the BlobRef was learned.
}