package discovery

import (
	"context"
	"fmt"

	"github.com/docker/docker/api/types/swarm"
)

// SwarmDockerClient is the subset of the Docker SDK SwarmDiscovery depends
// on. Defined as an interface so tests can supply a fake.
type SwarmDockerClient interface {
	ServiceList(ctx context.Context, opts swarm.ServiceListOptions) ([]swarm.Service, error)
}

// SwarmDiscovery orchestrates "given an image, which Swarm services should
// we update?". Unlike Discovery, it has no filesystem path to check — the
// opt-in label on the service itself is the only gate, since Swarm services
// have no local compose file to anchor a STACKS_ROOT check against.
type SwarmDiscovery struct {
	cli        SwarmDockerClient
	optInLabel string
}

// NewSwarm returns a SwarmDiscovery bound to the given Docker client and
// opt-in label.
func NewSwarm(cli SwarmDockerClient, optInLabel string) *SwarmDiscovery {
	return &SwarmDiscovery{cli: cli, optInLabel: optInLabel}
}

// FindJobs lists Swarm services, filters by image match + opt-in label, and
// returns one Job per matching service. Signature matches Discovery.FindJobs
// so both satisfy api.Finder.
func (d *SwarmDiscovery) FindJobs(ctx context.Context, image string) ([]Job, error) {
	services, err := d.cli.ServiceList(ctx, swarm.ServiceListOptions{})
	if err != nil {
		return nil, fmt.Errorf("docker service list: %w", err)
	}

	var jobs []Job
	for _, svc := range services {
		if svc.Spec.TaskTemplate.ContainerSpec == nil {
			continue
		}
		if !ImagesMatch(image, svc.Spec.TaskTemplate.ContainerSpec.Image) {
			continue
		}
		if !HasOptIn(svc.Spec.Labels, d.optInLabel) {
			continue
		}

		jobs = append(jobs, Job{
			Service:   svc.Spec.Name,
			ServiceID: svc.ID,
			Image:     image,
		})
	}

	return jobs, nil
}