Initial interfaces fr love transfer

backends/interfaces.go

@@ -0,0 +1,89 @@
+/*
+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"
+	"time"
+
+	"github.com/spf13/viper"
+)
+
+type Backend interface {
+	FromConfig(config *viper.Viper) Backend
+}
+
+type ListenExport interface {
+	ExportListens(oldestTimestamp time.Time) ([]Listen, error)
+}
+
+type ListenImport interface {
+	ImportListens(listens []Listen, oldestTimestamp time.Time) (ImportResult, error)
+}
+
+type LovesExport interface {
+	ExportLoves(oldestTimestamp time.Time) ([]Love, error)
+}
+
+type LovesImport interface {
+	ExportLoves(loves []Love, oldestTimestamp time.Time) (ImportResult, error)
+}
+
+type ImportResult struct {
+	Count         int
+	LastTimestamp time.Time
+}
+
+func resolveBackend(config *viper.Viper) (string, Backend, error) {
+	backendName := config.GetString("backend")
+	// fmt.Printf("requested backend %s\n", backendName)
+	backendType := knownBackends[backendName]
+	if backendType == nil {
+		return backendName, nil, errors.New(fmt.Sprintf("Unknown backend %s", backendName))
+	}
+	return backendName, backendType().FromConfig(config), nil
+}
+
+func ResolveBackend[T interface{}](config *viper.Viper) (T, error) {
+	expectedInterface := reflect.TypeOf((*T)(nil)).Elem()
+	backendName, backend, err := resolveBackend(config)
+	var result T
+	if err != nil {
+		return result, err
+	}
+	if backend != nil && reflect.TypeOf(backend).Implements(expectedInterface) {
+		result = backend.(T)
+	} else {
+		err = errors.New(
+			fmt.Sprintf("Backend %s does not implement %s", backendName, expectedInterface.String()))
+	}
+	return result, err
+}
+
+var knownBackends = map[string]func() Backend{
+	"dump":             func() Backend { return &DumpBackend{} },
+	"listenbrainz-api": func() Backend { return &ListenBrainzApiBackend{} },
+	"maloja-api":       func() Backend { return &MalojaApiBackend{} },
+	"scrobbler-log":    func() Backend { return &ScrobblerLogBackend{} },
+}