package updater

import (
	"context"
	"fmt"

	"github.com/docker/docker/api/types/swarm"
	"github.com/shcizo/package-updater/internal/discovery"
)

// SwarmDockerClient is the subset of the Docker SDK SwarmExecutor depends
// on. Defined as an interface so tests can supply a fake.
type SwarmDockerClient interface {
	ServiceInspectWithRaw(ctx context.Context, serviceID string, opts swarm.ServiceInspectOptions) (swarm.Service, []byte, error)
	ServiceUpdate(ctx context.Context, serviceID string, version swarm.Version, service swarm.ServiceSpec, opts swarm.ServiceUpdateOptions) (swarm.ServiceUpdateResponse, error)
}

// SwarmExecutor updates a Swarm service's image via the Docker API,
// equivalent to `docker service update --image`.
type SwarmExecutor struct {
	cli SwarmDockerClient
}

// NewSwarmExecutor returns an executor that drives Swarm service updates
// through the Docker API.
func NewSwarmExecutor(cli SwarmDockerClient) *SwarmExecutor {
	return &SwarmExecutor{cli: cli}
}

// Execute inspects the service to get its current spec and version (required
// by the Docker API as an optimistic-concurrency token), sets the new image
// on the container spec, and calls ServiceUpdate. QueryRegistry is set so a
// floating tag (e.g. ":latest") resolves to a fresh digest and actually
// triggers a rolling update instead of being treated as unchanged.
func (e *SwarmExecutor) Execute(ctx context.Context, job discovery.Job) error {
	if job.Refused {
		return fmt.Errorf("refused: %s", job.RefusedReason)
	}

	svc, _, err := e.cli.ServiceInspectWithRaw(ctx, job.ServiceID, swarm.ServiceInspectOptions{})
	if err != nil {
		return fmt.Errorf("inspect service %s: %w", job.ServiceID, err)
	}

	spec := svc.Spec
	spec.TaskTemplate.ContainerSpec.Image = job.Image

	if _, err := e.cli.ServiceUpdate(ctx, job.ServiceID, svc.Version, spec, swarm.ServiceUpdateOptions{QueryRegistry: true}); err != nil {
		return fmt.Errorf("update service %s: %w", job.ServiceID, err)
	}
	return nil
}