package twofactor

import (
	"context"
	"errors"
	model "git.sendico.io/tech/sxchnge/product/twofactor/model"
	vmodel "git.sendico.io/tech/sxchnge/product/verification/model"
	verification "git.sendico.io/tech/sxchnge/product/verification/store"
	merrors "git.sendico.io/tech/sxchnge/shared/errors"
	"go.mongodb.org/mongo-driver/v2/bson"
	"go.uber.org/zap"
	"strings"
	"time"
)

func (s *Service) Begin(ctx context.Context, req model.Request) (model.Challenge, error) {
	if !validScope(req.Scope) {
		return model.Challenge{}, merrors.InvalidArgument("unsupported second-factor operation scope")
	}
	return s.begin(ctx, req, nil)
}
func (s *Service) begin(ctx context.Context, req model.Request, enrollment *model.Factor) (model.Challenge, error) {
	if req.Subject.IsZero() || strings.TrimSpace(req.IdempotencyKey) == "" || len(req.IdempotencyKey) > 128 || strings.ContainsRune(req.IdempotencyKey, 0) {
		return model.Challenge{}, merrors.InvalidArgument("subject and idempotency key required")
	}
	a, p, version, err := s.profile(ctx, req.Subject)
	if err != nil {
		return model.Challenge{}, err
	}
	factor, err := s.preferred(p)
	if err != nil {
		return model.Challenge{}, err
	}
	if enrollment != nil {
		factor = *enrollment
	}
	// Repeating an operation key resolves to the same immutable challenge snapshot.
	id, _ := bson.ObjectIDFromHex(s.key("challenge", req.Subject.Hex(), scopeKey(req.Scope), req.IdempotencyKey)[:24])
	expires := time.Now().UTC().Add(TTL).Truncate(time.Millisecond)
	if !req.Deadline.IsZero() && req.Deadline.Before(expires) {
		expires = req.Deadline.UTC().Truncate(time.Millisecond)
	}
	if !expires.After(time.Now()) {
		return model.Challenge{}, verification.ErorrTokenExpired()
	}
	locale := "en"
	if strings.HasPrefix(strings.ToLower(a.Locale), "ru") {
		locale = "ru"
	}
	candidate := &model.Record{Subject: req.Subject, Scope: req.Scope, Factor: factor, ProfileVersion: version, Locale: locale, ExpiresAt: expires}
	candidate.ID = id
	result, err := s.tx.CreateTransaction().Execute(ctx, func(tx context.Context) (any, error) {
		r, err := s.store.Challenge(tx, id)
		if errors.Is(err, merrors.ErrNoData) {
			r = candidate
			if err = s.store.CreateChallenge(tx, r); err != nil {
				return nil, err
			}
		} else if err != nil {
			return nil, err
		}
		if r.Subject != req.Subject || r.Scope != req.Scope || r.Factor != factor || r.ProfileVersion != version {
			return nil, merrors.DataConflict("second-factor request changed")
		}
		return s.issue(tx, r, req.IdempotencyKey, req.IP)
	})
	if err != nil {
		return model.Challenge{}, err
	}
	return s.deliver(ctx, result)
}
func (s *Service) Resend(ctx context.Context, req model.Request, id string) (model.Challenge, error) {
	result, err := s.tx.CreateTransaction().Execute(ctx, func(tx context.Context) (any, error) {
		r, err := s.record(tx, id, req.Subject, req.Scope)
		if err != nil {
			return nil, err
		}
		return s.issue(tx, r, req.IdempotencyKey, req.IP)
	})
	if err != nil {
		return model.Challenge{}, err
	}
	return s.deliver(ctx, result)
}

type issued struct {
	record   *model.Record
	delivery model.Delivery
	resendAt time.Time
}

func (s *Service) issue(ctx context.Context, r *model.Record, key, ip string) (issued, error) {
	if r.VerifiedAt != nil {
		return issued{}, verification.ErorrTokenAlreadyUsed()
	}
	if !r.ExpiresAt.After(time.Now()) {
		return issued{}, verification.ErorrTokenExpired()
	}
	if strings.TrimSpace(key) == "" || len(key) > 128 || strings.ContainsRune(key, 0) {
		return issued{}, merrors.InvalidArgument("idempotency key required")
	}
	if ip == "" {
		ip = "unresolved"
	}
	secretKey := s.key("code", r.ID.Hex(), key)
	now := time.Now().UTC()
	req := verification.NewOTPRequest(r.Subject, r.Scope.Purpose, r.Factor.ID).
		WithContextRef(r.ID.Hex()).WithTTL(time.Until(r.ExpiresAt)).WithCooldown(Cooldown).WithMaxRetries(5).WithIdempotencyKey(secretKey).
		WithIssuanceLimits(verification.NewIssuanceLimit("twofactor_subject", r.Subject.Hex(), 5, time.Hour, now), verification.NewIssuanceLimit("twofactor_ip", ip, 20, time.Hour, now))
	token, err := s.tokens.CreateWithResult(ctx, req)
	if err != nil {
		return issued{}, err
	}
	if !token.ExpiresAt.After(now) {
		return issued{}, verification.ErorrTokenExpired()
	}
	return issued{record: r, delivery: model.Delivery{Key: secretKey, Subject: r.Subject, Scope: r.Scope, Factor: r.Factor, Locale: r.Locale, Code: token.VerificationToken, ExpiresAt: token.ExpiresAt}, resendAt: now.Add(Cooldown)}, nil
}
func (s *Service) deliver(ctx context.Context, result any) (model.Challenge, error) {
	issued, ok := result.(issued)
	if !ok {
		return model.Challenge{}, merrors.Internal("invalid second-factor issuance result")
	}
	driver := s.drivers[issued.record.Factor.Channel]
	if driver == nil {
		return model.Challenge{}, merrors.NotImplemented("second-factor channel unavailable")
	}
	if err := driver.Send(ctx, issued.delivery); err != nil {
		s.logger.Warn("Second-factor delivery unavailable", zap.String("challenge", issued.record.ID.Hex()), zap.String("channel", string(driver.Channel())))
		return model.Challenge{}, merrors.ServiceUnavailableWrap(err, "second-factor delivery unavailable")
	}
	s.logger.Info("Second-factor challenge queued", zap.String("challenge", issued.record.ID.Hex()), zap.String("purpose", string(issued.record.Scope.Purpose)), zap.String("channel", string(driver.Channel())))
	return model.Challenge{ID: issued.record.ID.Hex(), Channel: driver.Channel(), Target: driver.Mask(issued.record.Factor.Address), ExpiresAt: issued.delivery.ExpiresAt, ResendAt: issued.resendAt}, nil
}

func preferenceScope(factorID string) model.Scope {
	return model.Scope{Purpose: vmodel.PurposeFactorPreference, ContextRef: "preferred:" + factorID}
}