// Package provider reconciles TreatVault snapshots with platform secret providers.
package provider

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os/exec"
	"sort"
	"strings"

	barkfile "cloud.campbellwireless.net/git/barkstack/barkfile-parser/v2"
	"cloud.campbellwireless.net/git/barkstack/treatvault/internal/vault"
)

var ErrSecretInUse = errors.New("secret is in use")

type Runner interface {
	Run(context.Context, []byte, ...string) (string, error)
}

type ExecRunner struct {
	Path string
}

func (r ExecRunner) Run(ctx context.Context, input []byte, args ...string) (string, error) {
	path := r.Path
	if path == "" {
		path = "docker"
	}
	command := exec.CommandContext(ctx, path, args...)
	if input != nil {
		command.Stdin = strings.NewReader(string(input))
	}
	output, err := command.CombinedOutput()
	if err != nil {
		return string(output), fmt.Errorf("docker %s: %w: %s", strings.Join(args, " "), err, strings.TrimSpace(string(output)))
	}
	return string(output), nil
}

type SecretState struct {
	Name         string
	Revision     string
	PhysicalName string
	InUse        bool
}

type Docker struct {
	Runner Runner
}

// Sync reconciles snapshot with Docker Swarm: it creates one immutable secret
// object per record revision, rotates mounts on labeled consumer services, and
// removes obsolete objects. Names listed in a service's
// io.barkstack.treatvault.names label are mounted at barkstack_<name> targets.
func (d Docker) Sync(ctx context.Context, snapshot vault.Snapshot) ([]SecretState, error) {
	if d.Runner == nil {
		return nil, errors.New("Docker runner is required")
	}
	managed, err := d.managedSecrets(ctx, snapshot.VaultID)
	if err != nil {
		return nil, err
	}
	for name, record := range snapshot.Secrets {
		physical := physicalName(snapshot.VaultID, record.Revision)
		if containsSecret(managed, physical) {
			continue
		}
		args := []string{
			"secret", "create",
			"--label", barkfile.TreatVaultManagedLabel + "=true",
			"--label", barkfile.TreatVaultSecretNameLabel + "=" + name,
			"--label", barkfile.TreatVaultVaultIDLabel + "=" + snapshot.VaultID,
			"--label", barkfile.TreatVaultRevisionLabel + "=" + record.Revision,
			physical, "-",
		}
		if _, err := d.Runner.Run(ctx, record.Value, args...); err != nil {
			return nil, fmt.Errorf("create Docker secret for %q: %w", name, err)
		}
	}

	services, err := d.managedServices(ctx)
	if err != nil {
		return nil, err
	}
	inUse := make(map[string]bool)
	missing := make(map[string]struct{})
	desiredTargets := make(map[string]struct{}, len(snapshot.Secrets))
	for name := range snapshot.Secrets {
		desiredTargets[barkfile.DockerSecretName(name)] = struct{}{}
	}
	for _, service := range services {
		args := []string{"service", "update"}
		changed := false
		mountedByTarget := make(map[string]serviceSecret, len(service.Secrets))
		for _, mounted := range service.Secrets {
			mountedByTarget[mounted.Target] = mounted
			if _, managedTarget := desiredTargets[mounted.Target]; managedTarget {
				inUse[strings.TrimPrefix(mounted.Target, barkfile.DockerSecretPrefix)] = true
			}
		}
		for _, name := range service.DesiredNames {
			record, stored := snapshot.Secrets[name]
			if !stored {
				missing[name] = struct{}{}
				continue
			}
			inUse[name] = true
			desiredPhysical := physicalName(snapshot.VaultID, record.Revision)
			target := barkfile.DockerSecretName(name)
			mounted, isMounted := mountedByTarget[target]
			if isMounted && mounted.Source == desiredPhysical {
				continue
			}
			if isMounted {
				args = append(args, "--secret-rm", mounted.Source)
			}
			args = append(args, "--secret-add", secretMount(desiredPhysical, target))
			changed = true
		}
		for _, mounted := range service.Secrets {
			logical, managedTarget := strings.CutPrefix(mounted.Target, barkfile.DockerSecretPrefix)
			if !managedTarget {
				continue
			}
			if _, desired := desiredTargets[mounted.Target]; desired {
				continue
			}
			// Mounted under a Barkstack target but absent from the vault:
			// keep the mount so consumers keep working, surface the gap.
			missing[logical] = struct{}{}
		}
		if changed {
			args = append(args, service.Name)
			if _, err := d.Runner.Run(ctx, nil, args...); err != nil {
				return nil, fmt.Errorf("rotate secrets on service %q: %w", service.Name, err)
			}
		}
	}

	desiredPhysical := make(map[string]struct{}, len(snapshot.Secrets))
	for _, record := range snapshot.Secrets {
		desiredPhysical[physicalName(snapshot.VaultID, record.Revision)] = struct{}{}
	}
	for _, secret := range managed {
		if _, desired := desiredPhysical[secret.Name]; desired {
			continue
		}
		if _, err := d.Runner.Run(ctx, nil, "secret", "rm", secret.Name); err != nil && !isInUseError(err) {
			return nil, fmt.Errorf("remove obsolete Docker secret %q: %w", secret.Name, err)
		}
	}

	states := make([]SecretState, 0, len(snapshot.Secrets))
	for name, record := range snapshot.Secrets {
		states = append(states, SecretState{
			Name: name, Revision: record.Revision,
			PhysicalName: physicalName(snapshot.VaultID, record.Revision), InUse: inUse[name],
		})
	}
	sort.Slice(states, func(i, j int) bool { return states[i].Name < states[j].Name })
	if len(missing) != 0 {
		names := make([]string, 0, len(missing))
		for name := range missing {
			names = append(names, name)
		}
		sort.Strings(names)
		return states, fmt.Errorf("%w: %s", ErrSecretInUse, strings.Join(names, ", "))
	}
	return states, nil
}

// InUse reports whether any managed service currently mounts the secret at its
// barkstack_<name> target.
func (d Docker) InUse(ctx context.Context, name string) (bool, error) {
	services, err := d.managedServices(ctx)
	if err != nil {
		return false, err
	}
	target := barkfile.DockerSecretName(name)
	for _, service := range services {
		for _, secret := range service.Secrets {
			if secret.Target == target {
				return true, nil
			}
		}
	}
	return false, nil
}

type dockerSecret struct {
	Name        string
	LogicalName string
	Revision    string
	VaultID     string
}

func containsSecret(secrets []dockerSecret, name string) bool {
	for _, secret := range secrets {
		if secret.Name == name {
			return true
		}
	}
	return false
}

func (d Docker) managedSecrets(ctx context.Context, vaultID string) ([]dockerSecret, error) {
	output, err := d.Runner.Run(ctx, nil,
		"secret", "ls", "--quiet",
		"--filter", "label="+barkfile.TreatVaultManagedLabel+"=true",
		"--filter", "label="+barkfile.TreatVaultVaultIDLabel+"="+vaultID,
	)
	if err != nil {
		return nil, fmt.Errorf("list managed Docker secrets: %w", err)
	}
	ids := strings.Fields(output)
	secrets := make([]dockerSecret, 0, len(ids))
	for _, id := range ids {
		output, err := d.Runner.Run(ctx, nil, "secret", "inspect", "--format", "{{json .Spec}}", id)
		if err != nil {
			return nil, fmt.Errorf("inspect Docker secret %q: %w", id, err)
		}
		var spec struct {
			Name   string            `json:"Name"`
			Labels map[string]string `json:"Labels"`
		}
		if err := json.Unmarshal([]byte(output), &spec); err != nil {
			return nil, fmt.Errorf("decode Docker secret %q: %w", id, err)
		}
		if spec.Labels[barkfile.TreatVaultManagedLabel] != "true" || spec.Labels[barkfile.TreatVaultVaultIDLabel] != vaultID {
			continue
		}
		secrets = append(secrets, dockerSecret{
			Name: spec.Name, LogicalName: spec.Labels[barkfile.TreatVaultSecretNameLabel],
			Revision: spec.Labels[barkfile.TreatVaultRevisionLabel], VaultID: vaultID,
		})
	}
	return secrets, nil
}

type serviceSecret struct {
	Source string
	Target string
}

type dockerService struct {
	Name         string
	DesiredNames []string
	Secrets      []serviceSecret
}

func (d Docker) managedServices(ctx context.Context) ([]dockerService, error) {
	output, err := d.Runner.Run(ctx, nil,
		"service", "ls", "--quiet", "--filter", "label="+barkfile.TreatVaultConsumerLabel+"=true",
	)
	if err != nil {
		return nil, fmt.Errorf("list TreatVault consumer services: %w", err)
	}
	ids := strings.Fields(output)
	services := make([]dockerService, 0, len(ids))
	for _, id := range ids {
		output, err := d.Runner.Run(ctx, nil, "service", "inspect", "--format", "{{json .Spec}}", id)
		if err != nil {
			return nil, fmt.Errorf("inspect Docker service %q: %w", id, err)
		}
		var spec struct {
			Name         string            `json:"Name"`
			Labels       map[string]string `json:"Labels"`
			TaskTemplate struct {
				ContainerSpec struct {
					Secrets []struct {
						SecretName string `json:"SecretName"`
						File       *struct {
							Name string `json:"Name"`
						} `json:"File"`
					} `json:"Secrets"`
				} `json:"ContainerSpec"`
			} `json:"TaskTemplate"`
		}
		if err := json.Unmarshal([]byte(output), &spec); err != nil {
			return nil, fmt.Errorf("decode Docker service %q: %w", id, err)
		}
		names := spec.Labels[barkfile.TreatVaultNamesLabel]
		var desiredNames []string
		if names != "" {
			desiredNames = strings.Split(names, ",")
		}
		service := dockerService{Name: spec.Name, DesiredNames: desiredNames}
		for _, secret := range spec.TaskTemplate.ContainerSpec.Secrets {
			if secret.File != nil {
				service.Secrets = append(service.Secrets, serviceSecret{Source: secret.SecretName, Target: secret.File.Name})
			}
		}
		services = append(services, service)
	}
	return services, nil
}

func physicalName(vaultID, revision string) string {
	return barkfile.DockerSecretPrefix + "tv_" + vaultID + "_" + revision
}

func secretMount(source, target string) string {
	return "source=" + source + ",target=" + target
}

func isInUseError(err error) bool {
	message := strings.ToLower(err.Error())
	return strings.Contains(message, "in use") || strings.Contains(message, "used by")
}