package store

import (
	"context"
	"errors"
	"fmt"
	"time"

	"go.mongodb.org/mongo-driver/v2/bson"
	"go.mongodb.org/mongo-driver/v2/mongo"
	"go.mongodb.org/mongo-driver/v2/mongo/options"

	"bountyboard/internal/domain"
	"bountyboard/internal/ulid"
)

func (s *Store) tasks() *mongo.Collection { return s.DB.Collection("tasks") }

func (s *Store) InsertTask(ctx context.Context, t *domain.Task) error {
	now := time.Now().UTC()
	if t.ID == "" {
		t.ID = ulid.New()
	}
	if t.RootID == "" {
		t.RootID = t.ID
	}
	t.CreatedAt, t.UpdatedAt, t.Version = now, now, 1
	if t.AcceptanceCriteria == nil {
		t.AcceptanceCriteria = []string{}
	}
	if t.Attachments == nil {
		t.Attachments = []domain.TaskAttachment{}
	}
	if t.Links == nil {
		t.Links = []string{}
	}
	if t.ClaimRequests == nil {
		t.ClaimRequests = []domain.ClaimRequest{}
	}
	if t.Timeline == nil {
		t.Timeline = []domain.TimelineEntry{}
	}
	if t.Comments == nil {
		t.Comments = []domain.Comment{}
	}
	if t.TimeLog == nil {
		t.TimeLog = []domain.TimeLogEntry{}
	}
	if _, err := s.tasks().InsertOne(ctx, t); err != nil {
		if mongo.IsDuplicateKeyError(err) {
			return fmt.Errorf("task %s: %w", t.ID, ErrDuplicate)
		}
		return fmt.Errorf("insert task: %w", err)
	}
	return nil
}

func (s *Store) TaskByID(ctx context.Context, id string) (*domain.Task, error) {
	var t domain.Task
	err := s.tasks().FindOne(ctx, bson.M{"_id": id}).Decode(&t)
	if errors.Is(err, mongo.ErrNoDocuments) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("find task: %w", err)
	}
	return &t, nil
}

// TaskFilter selects tasks for boards and workers.
type TaskFilter struct {
	CustomerID    string
	CustomerIDs   []string
	ConsultantID  string
	ConsultantIDs []string
	Statuses      []domain.TaskStatus
	AssigneeID    string
	RootID        string
	ParentID      string
	Search        string // Mongo text index
	MinBounty     float64
	Sort          string // newest | bounty | updated
	Cursor        string
	Limit         int
}

func (f TaskFilter) build() bson.M {
	q := bson.M{}
	if f.CustomerID != "" {
		q["customerId"] = f.CustomerID
	}
	if len(f.CustomerIDs) > 0 {
		q["customerId"] = bson.M{"$in": f.CustomerIDs}
	}
	if f.ConsultantID != "" {
		q["consultantId"] = f.ConsultantID
	}
	if len(f.ConsultantIDs) > 0 {
		q["consultantId"] = bson.M{"$in": f.ConsultantIDs}
	}
	if len(f.Statuses) > 0 {
		q["status"] = bson.M{"$in": f.Statuses}
	}
	if f.AssigneeID != "" {
		q["assignee.userId"] = f.AssigneeID
	}
	if f.RootID != "" {
		q["rootId"] = f.RootID
	}
	if f.ParentID != "" {
		q["parentId"] = f.ParentID
	}
	if f.Search != "" {
		q["$text"] = bson.M{"$search": f.Search}
	}
	if f.MinBounty > 0 {
		q["bounty"] = bson.M{"$gte": f.MinBounty}
	}
	return q
}

func (s *Store) ListTasks(ctx context.Context, f TaskFilter) ([]domain.Task, error) {
	q := f.build()
	limit := f.Limit
	if limit <= 0 || limit > 500 {
		limit = 100
	}
	sort := bson.D{{Key: "_id", Value: -1}} // newest first (ULID)
	switch f.Sort {
	case "bounty":
		sort = bson.D{{Key: "bounty", Value: -1}, {Key: "_id", Value: -1}}
	case "updated":
		sort = bson.D{{Key: "updatedAt", Value: -1}}
	}
	if f.Cursor != "" && f.Sort != "bounty" && f.Sort != "updated" {
		q["_id"] = bson.M{"$lt": f.Cursor}
	}
	cur, err := s.tasks().Find(ctx, q, options.Find().SetSort(sort).SetLimit(int64(limit)))
	if err != nil {
		return nil, fmt.Errorf("list tasks: %w", err)
	}
	out := []domain.Task{}
	if err := cur.All(ctx, &out); err != nil {
		return nil, fmt.Errorf("decode tasks: %w", err)
	}
	return out, nil
}

// UpsertResult describes what an imported-ticket upsert did.
type UpsertResult struct {
	Created         bool
	UpstreamChanged bool // changed after atomization began (timeline-only)
	Task            *domain.Task
}

// UpsertImportedTask implements the §5.3 idempotent upsert keyed on
// (external.system, external.key, customerId). While the task is still
// `imported`, upstream refreshes title/description/attachments/raw; after
// atomization begins, a change only appends an "upstream ticket changed"
// timeline entry (caller notifies the consultant).
func (s *Store) UpsertImportedTask(ctx context.Context, incoming *domain.Task) (*UpsertResult, error) {
	if incoming.External == nil {
		return nil, errors.New("imported task requires external ref")
	}
	key := bson.M{
		"external.system": incoming.External.System,
		"external.key":    incoming.External.Key,
		"customerId":      incoming.CustomerID,
	}
	var existing domain.Task
	err := s.tasks().FindOne(ctx, key).Decode(&existing)
	switch {
	case errors.Is(err, mongo.ErrNoDocuments):
		incoming.Origin = domain.OriginImported
		incoming.Status = domain.StatusImported
		incoming.Timeline = []domain.TimelineEntry{{
			At: time.Now().UTC(), ActorID: "system", Event: "imported",
			Data: map[string]any{"key": incoming.External.Key},
		}}
		if err := s.InsertTask(ctx, incoming); err != nil {
			// A concurrent worker may have inserted the same key (unique
			// index): treat as found-and-unchanged.
			if errors.Is(err, ErrDuplicate) {
				return &UpsertResult{Created: false, Task: incoming}, nil
			}
			return nil, err
		}
		return &UpsertResult{Created: true, Task: incoming}, nil
	case err != nil:
		return nil, fmt.Errorf("find imported task: %w", err)
	}

	if existing.External.ContentHash == incoming.External.ContentHash {
		return &UpsertResult{Task: &existing}, nil // nothing new upstream
	}

	now := time.Now().UTC()
	if existing.Status == domain.StatusImported {
		_, err := s.tasks().UpdateOne(ctx, bson.M{"_id": existing.ID}, bson.M{
			"$set": bson.M{
				"title":                incoming.Title,
				"description":          incoming.Description,
				"attachments":          incoming.Attachments,
				"external.raw":         incoming.External.Raw,
				"external.url":         incoming.External.URL,
				"external.type":        incoming.External.Type,
				"external.contentHash": incoming.External.ContentHash,
				"updatedAt":            now,
			},
			"$inc": bson.M{"version": 1},
		})
		if err != nil {
			return nil, fmt.Errorf("refresh imported task: %w", err)
		}
		return &UpsertResult{Task: &existing}, nil
	}

	// Atomization already began: record only.
	_, err = s.tasks().UpdateOne(ctx, bson.M{"_id": existing.ID}, bson.M{
		"$set": bson.M{"external.contentHash": incoming.External.ContentHash, "updatedAt": now},
		"$push": bson.M{"timeline": domain.TimelineEntry{
			At: now, ActorID: "system", Event: "upstream_changed",
			Data: map[string]any{"key": incoming.External.Key},
		}},
		"$inc": bson.M{"version": 1},
	})
	if err != nil {
		return nil, fmt.Errorf("record upstream change: %w", err)
	}
	return &UpsertResult{UpstreamChanged: true, Task: &existing}, nil
}

// MarkTaskOrphaned flags a task whose upstream ticket disappeared (§5.3).
func (s *Store) MarkTaskOrphaned(ctx context.Context, id string) error {
	now := time.Now().UTC()
	res, err := s.tasks().UpdateOne(ctx,
		bson.M{"_id": id, "external.orphaned": bson.M{"$ne": true}},
		bson.M{
			"$set": bson.M{"external.orphaned": true, "updatedAt": now},
			"$push": bson.M{"timeline": domain.TimelineEntry{
				At: now, ActorID: "system", Event: "orphaned",
				Data: map[string]any{"reason": "no longer returned by upstream query"},
			}},
			"$inc": bson.M{"version": 1},
		})
	if err != nil {
		return fmt.Errorf("mark orphaned: %w", err)
	}
	if res.MatchedCount == 0 {
		return ErrNotFound // already orphaned or missing
	}
	return nil
}

// AppendTimeline pushes a timeline entry without status change.
func (s *Store) AppendTimeline(ctx context.Context, taskID string, e domain.TimelineEntry) error {
	if e.At.IsZero() {
		e.At = time.Now().UTC()
	}
	_, err := s.tasks().UpdateOne(ctx, bson.M{"_id": taskID}, bson.M{
		"$push": bson.M{"timeline": e},
		"$set":  bson.M{"updatedAt": time.Now().UTC()},
		"$inc":  bson.M{"version": 1},
	})
	if err != nil {
		return fmt.Errorf("append timeline: %w", err)
	}
	return nil
}

// TransitionTask performs a version-checked §4.4 transition with a timeline
// entry and optional extra $set fields.
func (s *Store) TransitionTask(ctx context.Context, t *domain.Task, to domain.TaskStatus,
	actorID, event string, data map[string]any, extraSet bson.M) error {
	if err := domain.Transition(t.Status, to); err != nil {
		return err
	}
	set := bson.M{"status": to}
	for k, v := range extraSet {
		set[k] = v
	}
	update := bson.M{
		"$set": set,
		"$push": bson.M{"timeline": domain.TimelineEntry{
			At: time.Now().UTC(), ActorID: actorID, Event: event, Data: data,
		}},
	}
	return UpdateVersioned(ctx, s.tasks(), t.ID, t.Version, update)
}

// SetTaskAttachments persists attachment metadata (e.g. cached fileIds).
func (s *Store) SetTaskAttachments(ctx context.Context, taskID string, atts []domain.TaskAttachment) error {
	_, err := s.tasks().UpdateOne(ctx, bson.M{"_id": taskID}, bson.M{
		"$set": bson.M{"attachments": atts, "updatedAt": time.Now().UTC()},
		"$inc": bson.M{"version": 1},
	})
	if err != nil {
		return fmt.Errorf("set attachments: %w", err)
	}
	return nil
}

// ListImportedTasksForOrphanCheck returns imported-origin tasks for one
// customer/system/consultant that are still live (not archived).
func (s *Store) ListImportedTasksForOrphanCheck(ctx context.Context, customerID, system, consultantID string) ([]domain.Task, error) {
	cur, err := s.tasks().Find(ctx, bson.M{
		"customerId":      customerID,
		"consultantId":    consultantID,
		"origin":          domain.OriginImported,
		"external.system": system,
		"status":          bson.M{"$ne": domain.StatusArchived},
	})
	if err != nil {
		return nil, fmt.Errorf("list for orphan check: %w", err)
	}
	out := []domain.Task{}
	if err := cur.All(ctx, &out); err != nil {
		return nil, fmt.Errorf("decode orphan check: %w", err)
	}
	return out, nil
}

// DeleteTasks removes tasks matching ids (re-run subdivision cleanup).
func (s *Store) DeleteTasks(ctx context.Context, ids []string) (int64, error) {
	res, err := s.tasks().DeleteMany(ctx, bson.M{"_id": bson.M{"$in": ids}})
	if err != nil {
		return 0, fmt.Errorf("delete tasks: %w", err)
	}
	return res.DeletedCount, nil
}