package payments

import (
	"context"
	"errors"
	"time"

	customer "git.sendico.io/tech/sxchnge/product/customers/model"
	"git.sendico.io/tech/sxchnge/product/twofactor"
	factor "git.sendico.io/tech/sxchnge/product/twofactor/model"
	verification "git.sendico.io/tech/sxchnge/product/verification/model"
	merrors "git.sendico.io/tech/sxchnge/shared/errors"
	mlogger "git.sendico.io/tech/sxchnge/shared/logging"
	"go.mongodb.org/mongo-driver/v2/bson"
	"go.uber.org/zap"
)

type Service struct {
	Store    Store
	Provider Provider
	Identity Identity
	Factors  twofactor.API
	Logger   mlogger.Logger
}

func (s *Service) ready() error {
	if s == nil || s.Store == nil || s.Provider == nil || s.Identity == nil || s.Factors == nil {
		return Unavailable
	}
	return nil
}
func (s *Service) record(ctx context.Context, a *customer.Account, id string) (*Record, error) {
	if err := s.ready(); err != nil {
		return nil, err
	}
	if a == nil || a.ID.IsZero() {
		return nil, NotFound
	}
	ref, err := bson.ObjectIDFromHex(id)
	if err != nil {
		return nil, NotFound
	}
	r, err := s.Store.Get(ctx, ref, a.ID, s.Provider.Namespace())
	if errors.Is(err, merrors.ErrNoData) {
		return nil, NotFound
	}
	if err != nil {
		return nil, err
	}
	subject, err := s.Identity.Subject(ctx, a)
	if err != nil {
		return nil, err
	}
	if subject != r.Subject {
		return nil, Unavailable
	}
	return r, nil
}
func (s *Service) Quote(ctx context.Context, a *customer.Account, request Request) (Quote, error) {
	if err := s.ready(); err != nil {
		return Quote{}, err
	}
	subject, err := s.Identity.Subject(ctx, a)
	if err != nil {
		return Quote{}, err
	}
	accounts, err := s.Provider.Accounts(ctx, subject)
	if err != nil {
		return Quote{}, err
	}
	q, err := s.Provider.Quote(ctx, subject, request, accounts)
	if err != nil {
		return Quote{}, err
	}
	providerRef := q.ID
	q.ID = bson.NewObjectID().Hex()
	r := &Record{Customer: a.ID, Namespace: s.Provider.Namespace(), Subject: subject, Quote: q, ProviderQuote: providerRef}
	r.SetID(mustID(q.ID))
	if err = s.Store.Create(ctx, r); err != nil {
		return Quote{}, err
	}
	s.Logger.Info("Customer quotation stored", zap.String("quote_ref", q.ID), zap.String("kind", request.Kind))
	return q, nil
}
func mustID(id string) bson.ObjectID { value, _ := bson.ObjectIDFromHex(id); return value }
func operationScope(r *Record) factor.Scope {
	return factor.Scope{Purpose: verification.PurposePayment, ContextRef: r.Quote.ID}
}
func (s *Service) Challenge(ctx context.Context, a *customer.Account, id, ip string) (factor.Challenge, error) {
	r, err := s.record(ctx, a, id)
	if err != nil {
		return factor.Challenge{}, err
	}
	if !time.Now().Before(r.Quote.ExpiresAt) || r.Key != "" {
		return factor.Challenge{}, ExpiredQuote
	}
	return s.Factors.Begin(ctx, factor.Request{Subject: a.ID, Scope: operationScope(r), Deadline: r.Quote.ExpiresAt, IdempotencyKey: "payment:" + r.Quote.ID, IP: ip})
}
func (s *Service) Resend(ctx context.Context, a *customer.Account, id, challenge, key, ip string) (factor.Challenge, error) {
	r, err := s.record(ctx, a, id)
	if err != nil {
		return factor.Challenge{}, err
	}
	if !time.Now().Before(r.Quote.ExpiresAt) || r.Key != "" {
		return factor.Challenge{}, ExpiredQuote
	}
	if !validKey(key) {
		return factor.Challenge{}, InvalidAmount
	}
	return s.Factors.Resend(ctx, factor.Request{Subject: a.ID, Scope: operationScope(r), Deadline: r.Quote.ExpiresAt, IdempotencyKey: key, IP: ip}, challenge)
}
func validKey(key string) bool {
	if len(key) < 16 || len(key) > 128 {
		return false
	}
	for _, c := range key {
		if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c == '-' || c == '_') {
			return false
		}
	}
	return true
}

// Authorize consumes the challenge atomically with a durable execution intent.
// No upstream I/O occurs inside the transaction. Replaying the same authorization
// recovers a lost response without reusing the one-use verification code.
func (s *Service) Authorize(ctx context.Context, a *customer.Account, id, challenge, code, key string) error {
	r, err := s.record(ctx, a, id)
	if err != nil {
		return err
	}
	if !validKey(key) {
		return InvalidAmount
	}
	if r.Key != "" {
		if r.Key == key {
			return nil
		}
		return ExpiredQuote
	}
	return s.Factors.Complete(ctx, a.ID, operationScope(r), challenge, code, func(tx context.Context) error {
		if !time.Now().Before(r.Quote.ExpiresAt) {
			return ExpiredQuote
		}
		return s.Store.Authorize(tx, r, key)
	})
}
func (s *Service) execute(ctx context.Context, r *Record) (Operation, error) {
	var remote RemoteOperation
	var err error
	if r.Payment != "" {
		remote, err = s.Provider.Payment(ctx, r.Payment)
	} else {
		remote, err = s.Provider.Execute(ctx, r.ProviderQuote, "sxchnge:payment:"+r.ID.Hex())
	}
	if err != nil {
		s.Logger.Warn("Payment execution needs reconciliation", zap.String("quote_ref", r.Quote.ID))
		return Operation{}, merrors.OpaqueWrap(Uncertain, err, "provider payment outcome unknown")
	}
	if remote.QuoteRef != r.ProviderQuote || remote.ID == "" || (r.Payment != "" && r.Payment != remote.ID) {
		return Operation{}, Uncertain
	}
	if r.Payment == "" {
		if err = s.Store.Attach(ctx, r, remote.ID); err != nil {
			return Operation{}, merrors.OpaqueWrap(Uncertain, err, "persist provider payment reference")
		}
	}
	s.Logger.Info("Payment execution reconciled", zap.String("quote_ref", r.Quote.ID), zap.String("payment_ref", remote.ID), zap.String("state", remote.Status))
	return Operation{ID: r.Quote.ID, Quote: r.Quote, Status: remote.Status, CreatedAt: remote.CreatedAt}, nil
}
func (s *Service) Submit(ctx context.Context, a *customer.Account, id, key string) (Operation, error) {
	r, err := s.record(ctx, a, id)
	if err != nil {
		return Operation{}, err
	}
	if !validKey(key) || r.Key == "" || r.Key != key {
		return Operation{}, FactorRequired
	}
	return s.execute(ctx, r)
}

// Reconcile replays the already authorized durable intent with the same provider
// key. A timeout or an empty upstream list is never treated as proof of absence.
func (s *Service) Reconcile(ctx context.Context, a *customer.Account, key string) (*Operation, error) {
	if err := s.ready(); err != nil {
		return nil, err
	}
	if !validKey(key) {
		return nil, NotFound
	}
	r, err := s.Store.ByKey(ctx, a.ID, s.Provider.Namespace(), key)
	if errors.Is(err, merrors.ErrNoData) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	r, err = s.record(ctx, a, r.ID.Hex())
	if err != nil {
		return nil, err
	}
	op, err := s.execute(ctx, r)
	return &op, err
}
func (s *Service) Fetch(ctx context.Context, a *customer.Account) (Snapshot, error) {
	if err := s.ready(); err != nil {
		return Snapshot{}, err
	}
	subject, err := s.Identity.Subject(ctx, a)
	if err != nil {
		return Snapshot{}, err
	}
	rows, err := s.Store.List(ctx, a.ID, s.Provider.Namespace())
	if err != nil {
		return Snapshot{}, err
	}
	result := Snapshot{Operations: []Operation{}}
	for _, r := range rows {
		if r.Subject != subject {
			return Snapshot{}, Unavailable
		}
		op, err := s.execute(ctx, &r)
		if errors.Is(err, Uncertain) {
			// A durable authorization with an unknown provider outcome remains
			// pending. It must not hide unrelated balances or report failure.
			op = Operation{ID: r.Quote.ID, Quote: r.Quote, Status: "pending", CreatedAt: r.CreatedAt}
		} else if err != nil {
			return Snapshot{}, err
		}
		result.Operations = append(result.Operations, op)
	}
	result.Accounts, err = s.Provider.Accounts(ctx, subject)
	if err != nil {
		return Snapshot{}, err
	}
	return result, nil
}