package tree

import (
	"context"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/account"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/aclchanges/aclpb"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/treestorage"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/treestorage/treepb"
	"github.com/gogo/protobuf/proto"
	"go.uber.org/zap"
	"sync"
)

type DocTree interface {
	RWLocker
	ID() string
	Header() *treepb.TreeHeader
	AddContent(ctx context.Context, content proto.Marshaler) (*aclpb.RawChange, error)
	AddRawChanges(ctx context.Context, validator ChangeValidator, changes ...*aclpb.RawChange) (AddResult, error)
	Heads() []string
	Root() *Change
	Iterate(func(change *Change) bool)
	IterateFrom(string, func(change *Change) bool)
	HasChange(string) bool
	SnapshotPath() []string
	ChangesAfterCommonSnapshot(snapshotPath []string) ([]*aclpb.RawChange, error)
	Storage() treestorage.TreeStorage
	DebugDump() (string, error)

	Close() error
}

type docTree struct {
	treeStorage    treestorage.TreeStorage
	accountData    *account.AccountData
	updateListener TreeUpdateListener

	id       string
	header   *treepb.TreeHeader
	tree     *Tree
	aclState *ACLState

	treeBuilder *treeBuilder

	sync.RWMutex
}

func BuildDocTreeWithIdentity(
	t treestorage.TreeStorage,
	acc *account.AccountData,
	listener TreeUpdateListener) (DocTree, error) {
	treeBuilder := newTreeBuilder(t, acc.Decoder)
	aclStateBuilder := newACLStateBuilderWithIdentity(acc.Decoder, acc)
	changeBuilder := newChangeBuilder()

	docTree := &docTree{
		treeStorage:     t,
		accountData:     acc,
		tree:            nil,
		aclState:        nil,
		treeBuilder:     treeBuilder,
		aclStateBuilder: aclStateBuilder,
		changeBuilder:   changeBuilder,
		updateListener:  listener,
	}
	err := docTree.rebuildFromStorage()
	if err != nil {
		return nil, err
	}
	err = docTree.removeOrphans()
	if err != nil {
		return nil, err
	}
	err = t.SetHeads(docTree.Heads())
	if err != nil {
		return nil, err
	}
	docTree.id, err = t.TreeID()
	if err != nil {
		return nil, err
	}
	docTree.header, err = t.Header()
	if err != nil {
		return nil, err
	}

	listener.Rebuild(docTree)

	return docTree, nil
}

func BuildACLTree(t treestorage.TreeStorage) {
	// TODO: Add logic for building without identity
}

func (a *docTree) removeOrphans() error {
	// removing attached or invalid orphans
	var toRemove []string

	orphans, err := a.treeStorage.Orphans()
	if err != nil {
		return err
	}
	for _, orphan := range orphans {
		if _, exists := a.tree.attached[orphan]; exists {
			toRemove = append(toRemove, orphan)
		}
		if _, exists := a.tree.invalidChanges[orphan]; exists {
			toRemove = append(toRemove, orphan)
		}
	}
	return a.treeStorage.RemoveOrphans(toRemove...)
}

func (a *docTree) rebuildFromStorage() (err error) {
	a.treeBuilder.Init()

	a.tree, err = a.treeBuilder.Build(false)
	if err != nil {
		return err
	}

	err = a.aclStateBuilder.Init(a.tree)
	if err != nil {
		return err
	}

	a.aclState, err = a.aclStateBuilder.Build()
	if err != nil {
		return err
	}

	return nil
}

func (a *docTree) ID() string {
	return a.id
}

func (a *docTree) Header() *treepb.TreeHeader {
	return a.header
}

func (a *docTree) ACLState() *ACLState {
	return a.aclState
}

func (a *docTree) Storage() treestorage.TreeStorage {
	return a.treeStorage
}

func (a *docTree) AddContent(ctx context.Context, build func(builder ChangeBuilder) error) (*aclpb.RawChange, error) {
	if a.accountData == nil {
		return nil, ErrTreeWithoutIdentity
	}

	defer func() {
		// TODO: should this be called in a separate goroutine to prevent accidental cycles (tree->updater->tree)
		a.updateListener.Update(a)
	}()

	a.changeBuilder.Init(a.aclState, a.tree, a.accountData)
	err := build(a.changeBuilder)
	if err != nil {
		return nil, err
	}

	ch, marshalled, err := a.changeBuilder.BuildAndApply()
	if err != nil {
		return nil, err
	}
	a.tree.AddFast(ch)
	rawCh := &aclpb.RawChange{
		Payload:   marshalled,
		Signature: ch.Signature(),
		Id:        ch.Id,
	}

	err = a.treeStorage.AddRawChange(rawCh)
	if err != nil {
		return nil, err
	}

	err = a.treeStorage.SetHeads([]string{ch.Id})
	if err != nil {
		return nil, err
	}
	return rawCh, nil
}

func (a *docTree) AddRawChanges(ctx context.Context, rawChanges ...*aclpb.RawChange) (AddResult, error) {
	// TODO: make proper error handling, because there are a lot of corner cases where this will break
	var err error
	var mode Mode

	var changes []*Change // TODO: = addChangesBuf[:0] ...
	for _, ch := range rawChanges {
		change, err := NewFromRawChange(ch)
		// TODO: think what if we will have incorrect signatures on rawChanges, how everything will work
		if err != nil {
			continue
		}
		changes = append(changes, change)
	}

	defer func() {
		if err != nil {
			return
		}

		err = a.removeOrphans()
		if err != nil {
			return
		}

		err = a.treeStorage.SetHeads(a.tree.Heads())
		if err != nil {
			return
		}

		switch mode {
		case Append:
			a.updateListener.Update(a)
		case Rebuild:
			a.updateListener.Rebuild(a)
		default:
			break
		}
	}()

	getAddedChanges := func() []*aclpb.RawChange {
		var added []*aclpb.RawChange
		for _, ch := range rawChanges {
			if _, exists := a.tree.attached[ch.Id]; exists {
				added = append(added, ch)
			}
		}
		return added
	}

	for _, ch := range changes {
		err = a.treeStorage.AddChange(ch)
		if err != nil {
			return AddResult{}, err
		}
		err = a.treeStorage.AddOrphans(ch.Id)
		if err != nil {
			return AddResult{}, err
		}
	}

	prevHeads := a.tree.Heads()
	mode = a.tree.Add(changes...)
	switch mode {
	case Nothing:
		return AddResult{
			OldHeads: prevHeads,
			Heads:    prevHeads,
			Summary:  AddResultSummaryNothing,
		}, nil

	case Rebuild:
		err = a.rebuildFromStorage()
		if err != nil {
			return AddResult{}, err
		}

		return AddResult{
			OldHeads: prevHeads,
			Heads:    a.tree.Heads(),
			Added:    getAddedChanges(),
			Summary:  AddResultSummaryRebuild,
		}, nil
	default:
		// just rebuilding the state from start without reloading everything from tree storage
		// as an optimization we could've started from current heads, but I didn't implement that
		a.aclState, err = a.aclStateBuilder.Build()
		if err != nil {
			return AddResult{}, err
		}

		return AddResult{
			OldHeads: prevHeads,
			Heads:    a.tree.Heads(),
			Added:    getAddedChanges(),
			Summary:  AddResultSummaryAppend,
		}, nil
	}
}

func (a *docTree) Iterate(f func(change *Change) bool) {
	a.tree.Iterate(a.tree.RootId(), f)
}

func (a *docTree) IterateFrom(s string, f func(change *Change) bool) {
	a.tree.Iterate(s, f)
}

func (a *docTree) HasChange(s string) bool {
	_, attachedExists := a.tree.attached[s]
	_, unattachedExists := a.tree.unAttached[s]
	_, invalidExists := a.tree.invalidChanges[s]
	return attachedExists || unattachedExists || invalidExists
}

func (a *docTree) Heads() []string {
	return a.tree.Heads()
}

func (a *docTree) Root() *Change {
	return a.tree.Root()
}

func (a *docTree) Close() error {
	return nil
}

func (a *docTree) SnapshotPath() []string {
	// TODO: think about caching this

	var path []string
	// TODO: think that the user may have not all of the snapshots locally
	currentSnapshotId := a.tree.RootId()
	for currentSnapshotId != "" {
		sn, err := a.treeBuilder.loadChange(currentSnapshotId)
		if err != nil {
			break
		}
		path = append(path, currentSnapshotId)
		currentSnapshotId = sn.SnapshotId
	}
	return path
}

func (a *docTree) ChangesAfterCommonSnapshot(theirPath []string) ([]*aclpb.RawChange, error) {
	// TODO: think about when the clients will have their full acl tree and thus full snapshots
	//  but no changes after some of the snapshots

	var (
		isNewDocument = len(theirPath) == 0
		ourPath       = a.SnapshotPath()
		// by default returning everything we have
		commonSnapshot = ourPath[len(ourPath)-1] // TODO: root snapshot, probably it is better to have a specific method in treestorage
		err            error
	)

	// if this is non-empty request
	if !isNewDocument {
		commonSnapshot, err = commonSnapshotForTwoPaths(ourPath, theirPath)
		if err != nil {
			return nil, err
		}
	}
	var rawChanges []*aclpb.RawChange
	// using custom load function to skip verification step and save raw changes
	load := func(id string) (*Change, error) {
		raw, err := a.treeStorage.GetChange(context.Background(), id)
		if err != nil {
			return nil, err
		}

		aclChange, err := a.treeBuilder.makeUnverifiedACLChange(raw)
		if err != nil {
			return nil, err
		}

		ch := NewChange(id, aclChange)
		rawChanges = append(rawChanges, raw)
		return ch, nil
	}
	// we presume that we have everything after the common snapshot, though this may not be the case in case of clients and only ACL tree changes
	log.With(
		zap.Strings("heads", a.tree.Heads()),
		zap.String("breakpoint", commonSnapshot),
		zap.String("id", a.id)).
		Debug("getting all changes from common snapshot")
	_, err = a.treeBuilder.dfs(a.tree.Heads(), commonSnapshot, load)
	if err != nil {
		return nil, err
	}
	if isNewDocument {
		// adding snapshot to raw changes
		_, err = load(commonSnapshot)
		if err != nil {
			return nil, err
		}
	}
	log.With(
		zap.Int("len(changes)", len(rawChanges)),
		zap.String("id", a.id)).
		Debug("returning all changes after common snapshot")

	return rawChanges, nil
}

func (a *docTree) DebugDump() (string, error) {
	return a.tree.Graph(ACLDescriptionParser)
}