package traceimpact

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strings"
)

// StageReopener applies an approved reopen to the workflow instance.
// It must not pause the instance or rewrite downstream stages.
type StageReopener interface {
	ReopenCompletedStage(ctx context.Context, instanceID int64, stageKey string, docTaskKeys []string, operatorID int64) error
}

// DocUnlocker moves selected approved documents back to drafting.
type DocUnlocker interface {
	ReopenApprovedDocs(ctx context.Context, projectID int64, docTaskKeys []string, actorID int64, reason string) error
}

// Service is the project trace index and the stage-backtrack ledger.
type Service struct {
	store     Store
	reopen    StageReopener
	unlock    DocUnlocker
	onRecheck func(ctx context.Context, mark RecheckMark)
}

func NewService(store Store) *Service {
	if store == nil {
		store = newMemStore()
	}
	return &Service{store: store}
}

func NewMemoryService() *Service {
	return NewService(newMemStore())
}

func (s *Service) SetStageReopener(r StageReopener) { s.reopen = r }
func (s *Service) SetDocUnlocker(u DocUnlocker)     { s.unlock = u }

// SetRecheckHook is called once when a new open recheck mark is stored.
// Repeat analyzes of the same source do not call it again.
func (s *Service) SetRecheckHook(fn func(ctx context.Context, mark RecheckMark)) {
	if s != nil {
		s.onRecheck = fn
	}
}

type actorCtxKey struct{}

// WithActor records who triggered this analysis so a recheck notice can reach their chat.
func WithActor(ctx context.Context, userID int64) context.Context {
	if userID <= 0 {
		return ctx
	}
	return context.WithValue(ctx, actorCtxKey{}, userID)
}

// ActorID is the user from WithActor, or 0.
func ActorID(ctx context.Context) int64 {
	id, _ := ctx.Value(actorCtxKey{}).(int64)
	return id
}

// IndexDocument projects explicit keys into items and same-line pairs into confirmed edges.
// Untyped IDs become candidate items only.
func (s *Service) IndexDocument(ctx context.Context, projectID int64, doc DocRef) (IndexState, error) {
	if projectID <= 0 || doc.DocID == "" {
		return IndexState{}, fmt.Errorf("traceimpact: project and doc are required")
	}
	keys := ExtractKeys(doc.Markdown)
	itemByKey := map[string]Item{}
	for _, k := range keys {
		review := ReviewConfirmed
		if !k.Explicit {
			review = ReviewCandidate
		}
		item, err := s.store.UpsertItem(ctx, Item{
			ProjectID: projectID, BusinessKey: k.Key, Kind: k.Kind,
			ReviewState: review, Statement: strings.TrimSpace(k.Line), SourceDocID: doc.DocID,
		})
		if err != nil {
			st := IndexState{ProjectID: projectID, DocID: doc.DocID, SnapshotID: doc.SnapshotID, Status: ImpactFailed, Error: err.Error()}
			_ = s.store.PutIndex(ctx, st)
			return st, err
		}
		sum := sha256.Sum256([]byte(k.Key + "\n" + strings.TrimSpace(k.Line)))
		if err := s.store.AppendRevision(ctx, ItemRevision{
			ItemID: item.ID, SourceDocID: doc.DocID, SnapshotID: doc.SnapshotID,
			ContentHash: hex.EncodeToString(sum[:]), Statement: strings.TrimSpace(k.Line),
			Extractor: ExtractorVersion,
		}); err != nil {
			return IndexState{}, err
		}
		itemByKey[k.Key] = item
	}
	for _, pair := range ExplicitPairsOnLine(doc.Markdown) {
		from, okA := itemByKey[pair[0]]
		to, okB := itemByKey[pair[1]]
		if !okA || !okB {
			continue
		}
		if _, err := s.store.UpsertEdge(ctx, Edge{
			ProjectID: projectID, FromItemID: from.ID, ToItemID: to.ID,
			RelationType: RelationRefines, Provenance: ProvenanceExplicit,
			ReviewState: ReviewConfirmed, EvidenceDoc: doc.DocID,
			FromKey: from.BusinessKey, ToKey: to.BusinessKey,
		}); err != nil {
			return IndexState{}, err
		}
	}
	st := IndexState{
		ProjectID: projectID, DocID: doc.DocID, SnapshotID: doc.SnapshotID,
		Status: "complete", Extractor: ExtractorVersion, ItemCount: len(keys),
	}
	if err := s.store.PutIndex(ctx, st); err != nil {
		return IndexState{}, err
	}
	return st, nil
}

// CoverageForDoc is what a change report should show before claiming no impact.
func (s *Service) CoverageForDoc(ctx context.Context, projectID int64, docID string) string {
	st, ok, err := s.store.IndexStatus(ctx, projectID, docID)
	if err != nil || !ok || st.Status == "" {
		return ImpactIndexPending
	}
	switch st.Status {
	case "complete":
		return ImpactNoKnown
	case "failed":
		return ImpactFailed
	case "partial":
		return ImpactPartial
	default:
		return ImpactIndexPending
	}
}

// Analyze walks confirmed edges from keys mentioned in the changed markdown.
// Missing index coverage never becomes "no impact".
func (s *Service) Analyze(ctx context.Context, projectID int64, source DocRef, others []DocRef) (*Report, error) {
	rep := &Report{ProjectID: projectID, SourceDocID: source.DocID, Impacts: []Impact{}}
	if projectID <= 0 || source.DocID == "" {
		rep.CoverageStatus = ImpactFailed
		rep.Summary = SummaryForCoverage(rep.CoverageStatus)
		rep.Suggestions = Suggest(rep.CoverageStatus, false)
		return rep, nil
	}
	srcIndex, ok, err := s.store.IndexStatus(ctx, projectID, source.DocID)
	if err != nil {
		rep.CoverageStatus = ImpactFailed
		rep.Summary = SummaryForCoverage(rep.CoverageStatus)
		rep.Suggestions = Suggest(rep.CoverageStatus, false)
		return rep, nil
	}
	if !ok || srcIndex.Status != "complete" {
		rep.CoverageStatus = ImpactIndexPending
		if ok && srcIndex.Status == "failed" {
			rep.CoverageStatus = ImpactFailed
		}
		rep.Summary = SummaryForCoverage(rep.CoverageStatus)
		rep.Suggestions = Suggest(rep.CoverageStatus, false)
		return rep, nil
	}

	items, err := s.store.ListItems(ctx, projectID)
	if err != nil {
		rep.CoverageStatus = ImpactFailed
		rep.Summary = SummaryForCoverage(rep.CoverageStatus)
		rep.Suggestions = Suggest(rep.CoverageStatus, false)
		return rep, nil
	}
	byID := map[int64]Item{}
	byKey := map[string]Item{}
	for _, it := range items {
		byID[it.ID] = it
		byKey[it.BusinessKey] = it
	}
	var start []int64
	for _, k := range ExtractKeys(source.Markdown) {
		if it, ok := byKey[k.Key]; ok && it.ReviewState == ReviewConfirmed {
			start = append(start, it.ID)
		}
	}
	edges, err := s.store.ListEdges(ctx, projectID)
	if err != nil {
		rep.CoverageStatus = ImpactFailed
		rep.Summary = SummaryForCoverage(rep.CoverageStatus)
		rep.Suggestions = Suggest(rep.CoverageStatus, false)
		return rep, nil
	}
	hits, truncated := WalkReverse(edges, start, MaxWalkDepth, MaxWalkNodes)
	docByKey := map[string]DocRef{source.DocID: source}
	for _, d := range others {
		docByKey[d.DocID] = d
	}
	for _, hit := range hits {
		it := byID[hit.ItemID]
		if !it.Tombstone && it.SourceDocID != "" && it.SourceDocID != source.DocID {
			target := docByKey[it.SourceDocID]
			if target.DocID != "" && !target.Visible {
				continue
			}
			rep.Impacts = append(rep.Impacts, Impact{
				DocID: it.SourceDocID, ItemKey: it.BusinessKey, StageKey: target.StageKey,
				ImpactType: ImpactConfirmed, Depth: hit.Depth,
				Reason: fmt.Sprintf("%s 经已确认关系受本次修改影响", it.BusinessKey),
			})
			if target.StageStatus == "completed" && target.StageKey != "" {
				already := false
				if existing, listErr := s.store.ListOpenMarks(ctx, projectID, target.StageKey); listErr == nil {
					for _, m := range existing {
						if m.SourceDoc == source.DocID {
							already = true
							break
						}
					}
				}
				saved, putErr := s.store.PutMark(ctx, RecheckMark{
					ProjectID: projectID, StageKey: target.StageKey, SourceDoc: source.DocID,
					Status: MarkOpen, Reason: "上游或同项目条目已变化",
				})
				if putErr == nil && !already && s.onRecheck != nil {
					s.onRecheck(ctx, saved)
				}
			}
		}
	}
	for _, e := range edges {
		if e.ReviewState != ReviewCandidate {
			continue
		}
		for _, id := range start {
			if e.ToItemID == id || e.FromItemID == id {
				rep.Impacts = append(rep.Impacts, Impact{
					ItemKey: byID[e.FromItemID].BusinessKey, ImpactType: ImpactPossible, Depth: 1,
					Reason: "候选关系尚未确认",
				})
				break
			}
		}
	}
	switch {
	case truncated:
		rep.CoverageStatus = ImpactPartial
	case len(rep.Impacts) == 0:
		rep.CoverageStatus = ImpactNoKnown
	default:
		rep.CoverageStatus = ImpactConfirmed
		for _, imp := range rep.Impacts {
			if imp.ImpactType == ImpactPossible && rep.CoverageStatus != ImpactConfirmed {
				rep.CoverageStatus = ImpactPossible
			}
			if imp.ImpactType == ImpactConfirmed {
				rep.CoverageStatus = ImpactConfirmed
				break
			}
		}
		onlyPossible := true
		for _, imp := range rep.Impacts {
			if imp.ImpactType == ImpactConfirmed {
				onlyPossible = false
			}
		}
		if onlyPossible {
			rep.CoverageStatus = ImpactPossible
		}
	}
	rep.Summary = SummaryForCoverage(rep.CoverageStatus)
	if rep.CoverageStatus == ImpactConfirmed {
		rep.Summary = fmt.Sprintf("发现 %d 条影响", len(rep.Impacts))
	}
	rep.Suggestions = Suggest(rep.CoverageStatus, len(rep.Impacts) > 0)
	return rep, nil
}

// DecideCandidate confirms or rejects a model/candidate edge.
func (s *Service) DecideCandidate(ctx context.Context, edgeID, actorID int64, creator bool, downstreamDoc string, downstreamAuthor int64, decision, reason string) error {
	if err := CanDecide(Actor{UserID: actorID, Creator: creator}, downstreamDoc, downstreamAuthor); err != nil {
		return err
	}
	if decision != DecisionConfirm && decision != DecisionReject {
		return fmt.Errorf("traceimpact: decision must be confirm or reject")
	}
	edge, err := s.store.GetEdge(ctx, edgeID)
	if err != nil {
		return err
	}
	review := ReviewConfirmed
	if decision == DecisionReject {
		review = ReviewRejected
	}
	if err := s.store.SetEdgeReview(ctx, edgeID, review); err != nil {
		return err
	}
	_, err = s.store.AddDecision(ctx, Decision{
		ProjectID: edge.ProjectID, EdgeID: edgeID, Decision: decision, Reason: reason, DecidedBy: actorID,
	})
	return err
}

// UpsertModelCandidate stores a model_candidate edge that stays out of confirmed walks until decided.
func (s *Service) UpsertModelCandidate(ctx context.Context, projectID int64, fromKey, toKey, evidenceDoc string) (Edge, error) {
	if projectID <= 0 || fromKey == "" || toKey == "" {
		return Edge{}, fmt.Errorf("traceimpact: project and both keys are required")
	}
	items, err := s.store.ListItems(ctx, projectID)
	if err != nil {
		return Edge{}, err
	}
	var from, to Item
	for _, it := range items {
		if it.BusinessKey == fromKey {
			from = it
		}
		if it.BusinessKey == toKey {
			to = it
		}
	}
	if from.ID == 0 || to.ID == 0 {
		return Edge{}, fmt.Errorf("traceimpact: both items must already be indexed")
	}
	return s.store.UpsertEdge(ctx, Edge{
		ProjectID: projectID, FromItemID: from.ID, ToItemID: to.ID,
		RelationType: RelationDependsOn, Provenance: ProvenanceModel,
		ReviewState: ReviewCandidate, EvidenceDoc: evidenceDoc,
		FromKey: from.BusinessKey, ToKey: to.BusinessKey,
	})
}

// ListCandidateEdges returns undecided candidate edges with business keys filled in.
func (s *Service) ListCandidateEdges(ctx context.Context, projectID int64) ([]Edge, error) {
	edges, err := s.store.ListEdges(ctx, projectID)
	if err != nil {
		return nil, err
	}
	items, err := s.store.ListItems(ctx, projectID)
	if err != nil {
		return nil, err
	}
	byID := map[int64]Item{}
	for _, it := range items {
		byID[it.ID] = it
	}
	var out []Edge
	for _, e := range edges {
		if e.ReviewState != ReviewCandidate {
			continue
		}
		if e.FromKey == "" {
			e.FromKey = byID[e.FromItemID].BusinessKey
		}
		if e.ToKey == "" {
			e.ToKey = byID[e.ToItemID].BusinessKey
		}
		out = append(out, e)
	}
	if out == nil {
		out = []Edge{}
	}
	return out, nil
}

// ReplayDecisions re-applies the decision ledger onto edge review_state.
// Latest decision per edge wins. Repair rebuilds must call this so rejected
// candidates cannot re-enter confirmed walks.
func (s *Service) ReplayDecisions(ctx context.Context, projectID int64) (applied int, err error) {
	decisions, err := s.store.ListDecisions(ctx, projectID)
	if err != nil {
		return 0, err
	}
	latest := map[int64]Decision{}
	for _, d := range decisions {
		latest[d.EdgeID] = d
	}
	for edgeID, d := range latest {
		review := ReviewConfirmed
		if d.Decision == DecisionReject {
			review = ReviewRejected
		}
		if err := s.store.SetEdgeReview(ctx, edgeID, review); err != nil {
			return applied, err
		}
		applied++
	}
	return applied, nil
}

// ListDecisions returns the authoritative decision ledger for a project.
func (s *Service) ListDecisions(ctx context.Context, projectID int64) ([]Decision, error) {
	out, err := s.store.ListDecisions(ctx, projectID)
	if err == nil && out == nil {
		out = []Decision{}
	}
	return out, err
}

// NeedsRecheckAck is true when the stage still has an open mark.
// Acknowledgement does not clear the mark.
func (s *Service) NeedsRecheckAck(ctx context.Context, projectID int64, stageKey string) (bool, error) {
	marks, err := s.store.ListOpenMarks(ctx, projectID, stageKey)
	if err != nil {
		return false, err
	}
	return len(marks) > 0, nil
}

// AcknowledgeRecheck records that the creator saw the marks. Marks stay open.
func (s *Service) AcknowledgeRecheck(ctx context.Context, projectID int64, stageKey string, userID int64) error {
	marks, err := s.store.ListOpenMarks(ctx, projectID, stageKey)
	if err != nil {
		return err
	}
	for _, m := range marks {
		if err := s.store.AckMark(ctx, m.ID, userID); err != nil {
			return err
		}
	}
	return nil
}

// ClearRecheck closes a mark only for an explicit human reason.
func (s *Service) ClearRecheck(ctx context.Context, markID int64, reason string) error {
	switch reason {
	case ClearNoChange, ClearRevision:
	default:
		return fmt.Errorf("traceimpact: recheck marks close only by no_change or revision_started")
	}
	return s.store.SetMarkStatus(ctx, markID, MarkCleared, reason)
}

// ReopenMark opens a previously cleared mark again, for example after a rejected proposal.
func (s *Service) ReopenMark(ctx context.Context, markID int64, reason string) error {
	return s.store.SetMarkStatus(ctx, markID, MarkOpen, reason)
}

// RequestReopen stores a request. Creators are approved immediately and applied.
func (s *Service) RequestReopen(ctx context.Context, req ReopenRequest, creator bool) (ReopenRequest, error) {
	if req.StageKey == "" || len(req.DocTasks) == 0 || strings.TrimSpace(req.Reason) == "" {
		return ReopenRequest{}, fmt.Errorf("traceimpact: stage, documents, and reason are required")
	}
	req.Status = ReopenPending
	stored, err := s.store.PutReopen(ctx, req)
	if err != nil {
		return ReopenRequest{}, err
	}
	if creator {
		return s.ApproveReopen(ctx, stored.ID, req.RequestedBy)
	}
	return stored, nil
}

// ApproveReopen lets the creator apply a pending request.
func (s *Service) ApproveReopen(ctx context.Context, requestID, creatorID int64) (ReopenRequest, error) {
	req, err := s.store.GetReopen(ctx, requestID)
	if err != nil {
		return ReopenRequest{}, err
	}
	if req.Status == ReopenApproved {
		return req, nil
	}
	if s.reopen == nil {
		return ReopenRequest{}, fmt.Errorf("traceimpact: stage reopen is not configured")
	}
	if err := s.reopen.ReopenCompletedStage(ctx, req.InstanceID, req.StageKey, req.DocTasks, creatorID); err != nil {
		return ReopenRequest{}, err
	}
	if s.unlock != nil {
		if err := s.unlock.ReopenApprovedDocs(ctx, req.ProjectID, req.DocTasks, creatorID, req.Reason); err != nil {
			return ReopenRequest{}, err
		}
	}
	req.Status = ReopenApproved
	return s.store.PutReopen(ctx, req)
}

func (s *Service) ListItems(ctx context.Context, projectID int64) ([]Item, error) {
	out, err := s.store.ListItems(ctx, projectID)
	if err == nil && out == nil {
		out = []Item{}
	}
	return out, err
}

func (s *Service) ListIndex(ctx context.Context, projectID int64) ([]IndexState, error) {
	out, err := s.store.ListIndex(ctx, projectID)
	if err == nil && out == nil {
		out = []IndexState{}
	}
	return out, err
}

func (s *Service) ListOpenMarks(ctx context.Context, projectID int64, stageKey string) ([]RecheckMark, error) {
	out, err := s.store.ListOpenMarks(ctx, projectID, stageKey)
	if err == nil && out == nil {
		out = []RecheckMark{}
	}
	return out, err
}

func (s *Service) GetReopen(ctx context.Context, id int64) (ReopenRequest, error) {
	return s.store.GetReopen(ctx, id)
}

func (s *Service) ListPendingReopens(ctx context.Context, projectID int64) ([]ReopenRequest, error) {
	if s == nil || s.store == nil {
		return nil, nil
	}
	out, err := s.store.ListPendingReopens(ctx, projectID)
	if err == nil && out == nil {
		out = []ReopenRequest{}
	}
	return out, err
}

// ErrNeedsConfirm is returned when a revision proposal is requested before confirmation.
var ErrNeedsConfirm = fmt.Errorf("traceimpact: confirmation required")

// ProposeRevision records a proposal for a human author. It never edits controlled content.
func (s *Service) ProposeRevision(ctx context.Context, projectID, userID int64, text string, confirmed bool) (string, error) {
	if !confirmed {
		return "", ErrNeedsConfirm
	}
	if projectID <= 0 || strings.TrimSpace(text) == "" {
		return "", fmt.Errorf("traceimpact: project and proposal text are required")
	}
	id, err := s.store.AddProposal(ctx, projectID, userID, strings.TrimSpace(text))
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("proposal-%d-by-%d", id, userID), nil
}