distributor/internal/app/backends.go

package app

import (
	"context"
	"fmt"
	"strconv"

	"gitea.maximumdirect.net/eric/distributor/internal/adapters/local"
	s3adapter "gitea.maximumdirect.net/eric/distributor/internal/adapters/s3"
	sshadapter "gitea.maximumdirect.net/eric/distributor/internal/adapters/ssh"
	"gitea.maximumdirect.net/eric/distributor/internal/config"
	"gitea.maximumdirect.net/eric/distributor/internal/storage"
)

const storagePathKey = "path"

const (
	sshHostKey          = "host"
	sshUserKey          = "user"
	sshPortKey          = "port"
	sshKeyFileKey       = "ssh_key_file"
	sshKnownHostsKey    = "known_hosts"
	sshHostKeyPolicyKey = "host_key_policy"
	sshReadOnlyHostsKey = "read_only_known_hosts"
	s3EndpointKey       = "endpoint"
	s3BucketKey         = "bucket"
	s3PrefixKey         = "prefix"
	s3RegionKey         = "region"
	s3ForcePathStyleKey = "force_path_style"
	s3AccessKeyIDKey    = "access_key_id"
	s3SecretAccessKey   = "secret_access_key"
)

type backendFactory struct {
	registry           *storage.Registry
	environment        config.Environment
	readOnlyKnownHosts bool
}

func newBackendFactory() *backendFactory {
	return newBackendFactoryWithEnvironment(config.ProcessEnvironment())
}

func newBackendFactoryWithEnvironment(environment config.Environment) *backendFactory {
	registry := storage.NewRegistry()
	_ = registry.Register(config.BackendLocal, func(ctx context.Context, cfg storage.OpenConfig) (storage.Backend, error) {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		return local.New(cfg[storagePathKey])
	})
	_ = registry.Register(config.BackendSSH, func(ctx context.Context, cfg storage.OpenConfig) (storage.Backend, error) {
		port, err := strconv.Atoi(cfg[sshPortKey])
		if err != nil {
			return nil, fmt.Errorf("ssh port: %w", err)
		}
		readOnlyKnownHosts := false
		if raw := cfg[sshReadOnlyHostsKey]; raw != "" {
			readOnlyKnownHosts, err = strconv.ParseBool(raw)
			if err != nil {
				return nil, fmt.Errorf("ssh read_only_known_hosts: %w", err)
			}
		}
		return sshadapter.New(ctx, sshadapter.Options{
			Host:               cfg[sshHostKey],
			User:               cfg[sshUserKey],
			Port:               port,
			Root:               cfg[storagePathKey],
			KeyFile:            cfg[sshKeyFileKey],
			KnownHosts:         cfg[sshKnownHostsKey],
			HostKeyPolicy:      sshadapter.HostKeyPolicy(cfg[sshHostKeyPolicyKey]),
			ReadOnlyKnownHosts: readOnlyKnownHosts,
		})
	})
	_ = registry.Register(config.BackendS3, func(ctx context.Context, cfg storage.OpenConfig) (storage.Backend, error) {
		forcePathStyle, err := strconv.ParseBool(cfg[s3ForcePathStyleKey])
		if err != nil {
			return nil, fmt.Errorf("s3 force_path_style: %w", err)
		}
		return s3adapter.New(ctx, s3adapter.Options{
			Endpoint:        cfg[s3EndpointKey],
			Bucket:          cfg[s3BucketKey],
			Prefix:          cfg[s3PrefixKey],
			Region:          cfg[s3RegionKey],
			ForcePathStyle:  forcePathStyle,
			AccessKeyID:     cfg[s3AccessKeyIDKey],
			SecretAccessKey: cfg[s3SecretAccessKey],
		})
	})
	return &backendFactory{registry: registry, environment: environment}
}

func (f *backendFactory) openSource(ctx context.Context, source config.Backend) (storage.Backend, error) {
	if source.Backend != config.BackendLocal && source.Backend != config.BackendSSH && source.Backend != config.BackendS3 {
		return nil, fmt.Errorf("source backend %s is not implemented for execution", source.Backend)
	}
	openConfig, err := f.sourceOpenConfig(source)
	if err != nil {
		return nil, err
	}
	return f.registry.Open(ctx, source.Backend, openConfig)
}

func (f *backendFactory) openDestination(ctx context.Context, destination config.Destination) (storage.Backend, error) {
	if destination.Backend != config.BackendLocal && destination.Backend != config.BackendSSH && destination.Backend != config.BackendS3 {
		return nil, fmt.Errorf("backend %s is not implemented for execution", destination.Backend)
	}
	openConfig, err := f.destinationOpenConfig(destination)
	if err != nil {
		return nil, err
	}
	return f.registry.Open(ctx, destination.Backend, openConfig)
}

func (f *backendFactory) openLocalPath(ctx context.Context, path string) (storage.Backend, error) {
	return f.registry.Open(ctx, config.BackendLocal, storage.OpenConfig{storagePathKey: path})
}

func (f *backendFactory) resolveCredentials(creds config.Credentials) (config.ResolvedCredentials, error) {
	return f.environment.ResolveCredentials(creds)
}

func (f *backendFactory) sourceOpenConfig(source config.Backend) (storage.OpenConfig, error) {
	cfg := sourceOpenConfig(source)
	if source.Backend == config.BackendS3 {
		if err := f.addS3Config(cfg, source.Endpoint, source.Bucket, source.Prefix, source.Region, source.ForcePath, source.Creds); err != nil {
			return nil, err
		}
	}
	if source.Backend == config.BackendSSH {
		cfg[sshReadOnlyHostsKey] = strconv.FormatBool(f.readOnlyKnownHosts)
	}
	return cfg, nil
}

func (f *backendFactory) destinationOpenConfig(destination config.Destination) (storage.OpenConfig, error) {
	cfg := destinationOpenConfig(destination)
	if destination.Backend == config.BackendS3 {
		if err := f.addS3Config(cfg, destination.Endpoint, destination.Bucket, destination.Prefix, destination.Region, destination.ForcePath, destination.Creds); err != nil {
			return nil, err
		}
	}
	if destination.Backend == config.BackendSSH {
		cfg[sshReadOnlyHostsKey] = strconv.FormatBool(f.readOnlyKnownHosts)
	}
	return cfg, nil
}

func (f *backendFactory) addS3Config(cfg storage.OpenConfig, endpoint, bucket, prefix, region string, forcePath *bool, creds config.Credentials) error {
	cfg[s3EndpointKey] = endpoint
	cfg[s3BucketKey] = bucket
	cfg[s3PrefixKey] = prefix
	cfg[s3RegionKey] = region
	cfg[s3ForcePathStyleKey] = strconv.FormatBool(config.ForcePathStyle(forcePath))
	if creds.AccessKeyIDEnv != "" || creds.SecretAccessKeyEnv != "" {
		resolved, err := f.resolveCredentials(creds)
		if err != nil {
			return err
		}
		cfg[s3AccessKeyIDKey] = resolved.AccessKeyID
		cfg[s3SecretAccessKey] = resolved.SecretAccessKey
	}
	return nil
}

func sourceOpenConfig(source config.Backend) storage.OpenConfig {
	cfg := storage.OpenConfig{storagePathKey: source.Path}
	if source.Backend == config.BackendSSH {
		cfg[sshHostKey] = source.Host
		cfg[sshUserKey] = source.User
		cfg[sshPortKey] = strconv.Itoa(source.Port)
		cfg[sshKeyFileKey] = source.SSH.KeyFile
		cfg[sshKnownHostsKey] = source.SSH.KnownHosts
		cfg[sshHostKeyPolicyKey] = string(source.SSH.HostKeyPolicy)
		cfg[sshReadOnlyHostsKey] = "false"
	}
	return cfg
}

func destinationOpenConfig(destination config.Destination) storage.OpenConfig {
	cfg := storage.OpenConfig{storagePathKey: destination.Path}
	if destination.Backend == config.BackendSSH {
		cfg[sshHostKey] = destination.Host
		cfg[sshUserKey] = destination.User
		cfg[sshPortKey] = strconv.Itoa(destination.Port)
		cfg[sshKeyFileKey] = destination.SSH.KeyFile
		cfg[sshKnownHostsKey] = destination.SSH.KnownHosts
		cfg[sshHostKeyPolicyKey] = string(destination.SSH.HostKeyPolicy)
		cfg[sshReadOnlyHostsKey] = "false"
	}
	return cfg
}