package service

import (
	"context"
	"errors"
	"time"

	"git.sendico.io/tech/sxchnge/notifications/model"
	merrors "git.sendico.io/tech/sxchnge/shared/errors"
	"go.uber.org/zap"
)

// Dispatch consumes an opaque job ID from JetStream. Duplicate messages are safe.
func (s *Service) Dispatch(ctx context.Context, id string) (bool, error) {
	now := time.Now().UTC()
	if err := s.repo.Recover(ctx, now); err != nil {
		return false, err
	}
	n, err := s.repo.Claim(ctx, id, now)
	if errors.Is(err, merrors.ErrNoData) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	switch {
	case !n.ExpiresAt.After(now):
		n.State = model.Expired
		n.FailureCode = "expired"
	case n.Driver != s.driver:
		n.State = model.Failed
		n.FailureCode = "driver_changed"
	default:
		deadline := now.Add(20 * time.Second)
		if n.ExpiresAt.Before(deadline) {
			deadline = n.ExpiresAt
		}
		sendCtx, cancel := context.WithDeadline(ctx, deadline)
		outcome := s.sender.Send(sendCtx, n.ID.Hex(), n.Email)
		cancel()
		n.State = outcome.State
		n.FailureCode = outcome.Code
		if n.State == model.RetryWait {
			delay := time.Duration(1<<min(n.Attempts, 8)) * time.Second
			if outcome.RetryAfter > delay {
				delay = outcome.RetryAfter
			}
			n.NextAttemptAt = time.Now().UTC().Add(delay)
			if n.Attempts >= 5 {
				n.State = model.Failed
				n.FailureCode = "retry_exhausted"
			} else if !n.NextAttemptAt.Before(n.ExpiresAt) {
				n.State = model.Expired
				n.FailureCode = "expired"
			}
		} else if n.State != model.Accepted && n.State != model.Failed && n.State != model.Unknown {
			n.State = model.Unknown
			n.FailureCode = "invalid_driver_outcome"
		}
	}
	n.UpdatedAt = time.Now().UTC()
	// Persist the result even when shutdown canceled the provider request.
	finishCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), 5*time.Second)
	defer cancel()
	if err = s.repo.Finish(finishCtx, n); err != nil {
		return true, err
	}
	fields := []zap.Field{zap.String("notification_id", n.ID.Hex()), zap.String("driver", n.Driver), zap.String("state", string(n.State)), zap.Uint32("attempts", n.Attempts), zap.String("failure_code", n.FailureCode)}
	if n.State == model.Accepted {
		s.logger.Info("Email accepted by provider", fields...)
	} else {
		s.logger.Warn("Email delivery attempt finished", fields...)
	}
	return true, nil
}