package store

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

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

	"bountyboard/internal/domain"
)

// ErrDuplicate is returned when a unique index rejects an insert/update
// (e.g. email already registered).
var ErrDuplicate = errors.New("duplicate value")

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

// NormalizeEmail is the canonical form stored and queried everywhere.
func NormalizeEmail(email string) string {
	return strings.ToLower(strings.TrimSpace(email))
}

func (s *Store) CreateUser(ctx context.Context, u *domain.User) error {
	now := time.Now().UTC()
	u.Email = NormalizeEmail(u.Email)
	u.CreatedAt, u.UpdatedAt, u.Version = now, now, 1
	if u.LastSeenAt.IsZero() {
		u.LastSeenAt = now
	}
	if _, err := s.users().InsertOne(ctx, u); err != nil {
		if mongo.IsDuplicateKeyError(err) {
			return fmt.Errorf("user %s: %w", u.Email, ErrDuplicate)
		}
		return fmt.Errorf("insert user: %w", err)
	}
	return nil
}

func (s *Store) userBy(ctx context.Context, filter bson.M) (*domain.User, error) {
	var u domain.User
	err := s.users().FindOne(ctx, filter).Decode(&u)
	if errors.Is(err, mongo.ErrNoDocuments) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("find user: %w", err)
	}
	return &u, nil
}

func (s *Store) UserByID(ctx context.Context, id string) (*domain.User, error) {
	return s.userBy(ctx, bson.M{"_id": id})
}

func (s *Store) UserByEmail(ctx context.Context, email string) (*domain.User, error) {
	return s.userBy(ctx, bson.M{"email": NormalizeEmail(email)})
}

func (s *Store) UserByOIDC(ctx context.Context, issuer, subject string) (*domain.User, error) {
	return s.userBy(ctx, bson.M{"auth.oidc.issuer": issuer, "auth.oidc.subject": subject})
}

func (s *Store) CountUsers(ctx context.Context) (int64, error) {
	n, err := s.users().CountDocuments(ctx, bson.M{})
	if err != nil {
		return 0, fmt.Errorf("count users: %w", err)
	}
	return n, nil
}

// SetPassword replaces the local credential and clears/sets the forced
// change flag. Not version-checked: password changes must never lose to a
// concurrent profile edit.
func (s *Store) SetPassword(ctx context.Context, userID, hash string, mustChange bool) error {
	res, err := s.users().UpdateOne(ctx, bson.M{"_id": userID}, bson.M{
		"$set": bson.M{
			"auth.local.passwordHash": hash,
			"auth.local.mustChange":   mustChange,
			"updatedAt":               time.Now().UTC(),
		},
		"$inc": bson.M{"version": 1},
	})
	if err != nil {
		return fmt.Errorf("set password: %w", err)
	}
	if res.MatchedCount == 0 {
		return fmt.Errorf("user %s: %w", userID, ErrNotFound)
	}
	return nil
}

// LinkOIDC attaches an OIDC identity to an existing account (login linking
// by verified email, §7).
func (s *Store) LinkOIDC(ctx context.Context, userID, issuer, subject string) error {
	res, err := s.users().UpdateOne(ctx, bson.M{"_id": userID}, bson.M{
		"$set": bson.M{
			"auth.oidc": domain.OIDCAuth{Issuer: issuer, Subject: subject},
			"updatedAt": time.Now().UTC(),
		},
		"$inc": bson.M{"version": 1},
	})
	if err != nil {
		if mongo.IsDuplicateKeyError(err) {
			return fmt.Errorf("oidc identity: %w", ErrDuplicate)
		}
		return fmt.Errorf("link oidc: %w", err)
	}
	if res.MatchedCount == 0 {
		return fmt.Errorf("user %s: %w", userID, ErrNotFound)
	}
	return nil
}

// ListAdminIDs returns ids of all active admins (system notifications).
func (s *Store) ListAdminIDs(ctx context.Context) ([]string, error) {
	cur, err := s.users().Find(ctx, bson.M{"roles.admin": true, "disabled": false})
	if err != nil {
		return nil, fmt.Errorf("list admins: %w", err)
	}
	var users []domain.User
	if err := cur.All(ctx, &users); err != nil {
		return nil, fmt.Errorf("decode admins: %w", err)
	}
	ids := make([]string, len(users))
	for i, u := range users {
		ids[i] = u.ID
	}
	return ids, nil
}

// TouchLastSeen updates lastSeenAt without bumping version (pure telemetry).
func (s *Store) TouchLastSeen(ctx context.Context, userID string) error {
	_, err := s.users().UpdateOne(ctx, bson.M{"_id": userID},
		bson.M{"$set": bson.M{"lastSeenAt": time.Now().UTC()}})
	if err != nil {
		return fmt.Errorf("touch lastSeenAt: %w", err)
	}
	return nil
}