// 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 vsync

import (
	"v.io/x/ref/services/syncbase/server/interfaces"
)

// SyncData represents the persistent state of the sync module.
type SyncData struct {
	Id uint64
}

// DbSyncState represents the persistent sync state of a Database.
type DbSyncState struct {
	GenVecs   interfaces.Knowledge // knowledge capturing the locally-known generations of remote peers for data in Database.
	SgGenVecs interfaces.Knowledge // knowledge capturing the locally-known generations of remote peers for syncgroups in Database.
	IsPaused  bool                 // tracks whether sync is paused by client.
}

// LocalLogRec represents the persistent local state of a log record. Metadata
// is synced across peers, while pos is local-only.
type LocalLogRec struct {
	Metadata interfaces.LogRecMetadata
	Pos      uint64 // position in the Database log.
}

// SgLocalState holds the syncgroup local state, only relevant to this member
// (i.e. the local Syncbase).  This is needed for crash recovery of the internal
// state transitions of the syncgroup.
type SgLocalState struct {
	// The count of local joiners to the same syncgroup.
	NumLocalJoiners uint32

	// The syncgroup is watched when the sync Watcher starts processing the
	// syncgroup data.  When a syncgroup is created or joined, an entry is
	// added to the Watcher queue (log) to inform it from which point to
	// start accepting store mutations, an asynchronous notification similar
	// to regular store mutations.  When the Watcher processes that queue
	// entry, it sets this bit to true.  When Syncbase restarts, the value
	// of this bit allows the new sync Watcher to recreate its in-memory
	// state by resuming to watch only the prefixes of syncgroups that were
	// previously being watched.
	Watched bool

	// The syncgroup was published here by this remote peer (if non-empty
	// string), typically the syncgroup creator.  In this case the syncgroup
	// cannot be GCed locally even if it has no local joiners.
	RemotePublisher string

	// The syncgroup is in pending state on a device that learns the current
	// state of the syncgroup from another device but has not yet received
	// through peer-to-peer sync the history of the changes (DAG and logs).
	// This happens in two cases:
	// 1- A joiner was accepted into a syncgroup by a syncgroup admin and
	//    only given the current syncgroup info synchronously and will
	//    receive the full history later via p2p sync.
	// 2- A remote server where the syncgroup is published was told by the
	//    syncgroup publisher the current syncgroup info synchronously and
	//    will receive the full history later via p2p sync.
	// The pending state is over when the device reaches or exceeds the
	// knowledge level indicated in the pending genvec.  While SyncPending
	// is true, no local syncgroup mutations are allowed (i.e. no join or
	// set-spec requests).
	SyncPending   bool
	PendingGenVec interfaces.GenVector
}

// DagNode holds the information on an object mutation in the DAG.  The node
// information is extracted from the log records exchanged between Syncbases.
// They are also stored in the DAG node to improve DAG traversal for conflict
// resolution and pruning without having to fetch the full log record.
type DagNode struct {
	Level    uint64   // node distance from root
	Parents  []string // references to parent versions
	Logrec   string   // reference to log record
	BatchId  uint64   // ID of a write batch
	Deleted  bool     // true if the change was a delete
	PermId   string   // ID of the permissions controlling this version
	PermVers string   // current version of the permissions object
}

// BatchInfo holds the information on a write batch:
//  * The map of syncable (versioned) objects: {oid: version}
//  * The map of linked objects {oid: version} that were not explicitly written
//    as part of the batch but were reaffirmed during conflict resolution along
//    with other objects written in this batch by the app by choosing
//    "pickLocal" or "pickRemote". NOTE: this map is non empty only for batches
//    created during conflict resolution. Unlike the Objects map, the collection
//    of oid:version present in this map do not point back to this batch. They
//    point to the batches that there were originally created in.
//  * The total count of batch objects, including non-syncable ones.
// TODO(rdaoud): add support to track the read and scan sets.
type BatchInfo struct {
	Objects       map[string]string
	LinkedObjects map[string]string
	Count         uint64
}