scotty/backends/backends.go

/*
Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
package backends

import (
	"errors"
	"fmt"
	"reflect"
	"strings"

	"github.com/spf13/viper"
	"go.uploadedlobster.com/scotty/backends/dump"
	"go.uploadedlobster.com/scotty/backends/funkwhale"
	"go.uploadedlobster.com/scotty/backends/jspf"
	"go.uploadedlobster.com/scotty/backends/listenbrainz"
	"go.uploadedlobster.com/scotty/backends/maloja"
	"go.uploadedlobster.com/scotty/backends/scrobblerlog"
	"go.uploadedlobster.com/scotty/backends/spotify"
	"go.uploadedlobster.com/scotty/backends/subsonic"
	"go.uploadedlobster.com/scotty/models"
)

type BackendInfo struct {
	Name               string
	ExportCapabilities []Capability
	ImportCapabilities []Capability
}

type Capability = string

func ResolveBackend[T interface{}](config *viper.Viper) (T, error) {
	backendName, backend, err := resolveBackend(config)
	var result T
	if err != nil {
		return result, err
	}
	implements, interfaceName := ImplementsInterface[T](&backend)
	if implements {
		result = backend.(T)
	} else {
		err = errors.New(
			fmt.Sprintf("Backend %s does not implement %s", backendName, interfaceName))
	}
	return result, err
}

func GetBackends() []BackendInfo {
	backends := make([]BackendInfo, 0)
	for name, backendFunc := range knownBackends {
		backend := backendFunc()
		info := BackendInfo{
			Name:               name,
			ExportCapabilities: getExportCapabilities(backend),
			ImportCapabilities: getImportCapabilities(backend),
		}
		backends = append(backends, info)
	}

	return backends
}

var knownBackends = map[string]func() models.Backend{
	"dump":          func() models.Backend { return &dump.DumpBackend{} },
	"funkwhale":     func() models.Backend { return &funkwhale.FunkwhaleApiBackend{} },
	"jspf":          func() models.Backend { return &jspf.JspfBackend{} },
	"listenbrainz":  func() models.Backend { return &listenbrainz.ListenBrainzApiBackend{} },
	"maloja":        func() models.Backend { return &maloja.MalojaApiBackend{} },
	"scrobbler-log": func() models.Backend { return &scrobblerlog.ScrobblerLogBackend{} },
	"spotify":       func() models.Backend { return &spotify.SpotifyApiBackend{} },
	"subsonic":      func() models.Backend { return &subsonic.SubsonicApiBackend{} },
}

func resolveBackend(config *viper.Viper) (string, models.Backend, error) {
	backendName := config.GetString("backend")
	backendType := knownBackends[backendName]
	if backendType == nil {
		return backendName, nil, fmt.Errorf("Unknown backend %s", backendName)
	}
	return backendName, backendType().FromConfig(config), nil
}

func ImplementsInterface[T interface{}](backend *models.Backend) (bool, string) {
	expectedInterface := reflect.TypeOf((*T)(nil)).Elem()
	implements := backend != nil && reflect.TypeOf(*backend).Implements(expectedInterface)
	return implements, expectedInterface.Name()
}

func getExportCapabilities(backend models.Backend) []string {
	caps := make([]Capability, 0)
	var name string
	var found bool
	name, found = checkCapability[models.ListensExport](backend, "export")
	if found {
		caps = append(caps, name)
	}
	name, found = checkCapability[models.LovesExport](backend, "export")
	if found {
		caps = append(caps, name)
	}
	return caps
}

func getImportCapabilities(backend models.Backend) []Capability {
	caps := make([]Capability, 0)
	var name string
	var found bool
	name, found = checkCapability[models.ListensImport](backend, "import")
	if found {
		caps = append(caps, name)
	}
	name, found = checkCapability[models.LovesImport](backend, "import")
	if found {
		caps = append(caps, name)
	}
	return caps
}

func checkCapability[T interface{}](backend models.Backend, suffix string) (string, bool) {
	implements, name := ImplementsInterface[T](&backend)
	if implements {
		cap, found := strings.CutSuffix(strings.ToLower(name), suffix)
		if found {
			return cap, found
		}
	}

	return "", false
}