Reduced code redundancy in import processing

internal/backends/import.go

@@ -0,0 +1,121 @@
+/*
+Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>
+
+This file is part of Scotty.
+
+Scotty is free software: you can redistribute it and/or modify it under the
+terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later version.
+
+Scotty is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+Scotty. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package backends
+
+import "go.uploadedlobster.com/scotty/internal/models"
+
+type ImportProcessor[T models.ListensResult | models.LovesResult] interface {
+	ImportBackend() models.ImportBackend
+	Process(results chan T, out chan models.ImportResult, progress chan models.Progress)
+	Import(export T, result models.ImportResult, out chan models.ImportResult, progress chan models.Progress) models.ImportResult
+}
+
+type ListensImportProcessor struct {
+	Backend models.ListensImport
+}
+
+func (p ListensImportProcessor) ImportBackend() models.ImportBackend {
+	return p.Backend
+}
+
+func (p ListensImportProcessor) Process(results chan models.ListensResult, out chan models.ImportResult, progress chan models.Progress) {
+	process(p, results, out, progress)
+}
+
+func (p ListensImportProcessor) Import(export models.ListensResult, result models.ImportResult, out chan models.ImportResult, progress chan models.Progress) models.ImportResult {
+	if export.Error != nil {
+		handleError(result, export.Error, out, progress)
+		return result
+	}
+
+	if export.Total > 0 {
+		result.TotalCount = export.Total
+	} else {
+		result.TotalCount += len(export.Items)
+	}
+	importResult, err := p.Backend.ImportListens(export, result, progress)
+	if err != nil {
+		handleError(importResult, err, out, progress)
+		return result
+	}
+	return importResult
+}
+
+type LovesImportProcessor struct {
+	Backend models.LovesImport
+}
+
+func (p LovesImportProcessor) ImportBackend() models.ImportBackend {
+	return p.Backend
+}
+
+func (p LovesImportProcessor) Process(results chan models.LovesResult, out chan models.ImportResult, progress chan models.Progress) {
+	process(p, results, out, progress)
+}
+
+func (p LovesImportProcessor) Import(export models.LovesResult, result models.ImportResult, out chan models.ImportResult, progress chan models.Progress) models.ImportResult {
+	if export.Error != nil {
+		handleError(result, export.Error, out, progress)
+		return result
+	}
+
+	if export.Total > 0 {
+		result.TotalCount = export.Total
+	} else {
+		result.TotalCount += len(export.Items)
+	}
+	importResult, err := p.Backend.ImportLoves(export, result, progress)
+	if err != nil {
+		handleError(importResult, err, out, progress)
+		return result
+	}
+	return importResult
+}
+
+func process[R models.LovesResult | models.ListensResult, P ImportProcessor[R]](processor P, results chan R, out chan models.ImportResult, progress chan models.Progress) {
+	defer close(out)
+	defer close(progress)
+	result := models.ImportResult{}
+
+	err := processor.ImportBackend().StartImport()
+	if err != nil {
+		handleError(result, err, out, progress)
+		return
+	}
+
+	for exportResult := range results {
+		importResult := processor.Import(exportResult, result, out, progress)
+		result.Update(importResult)
+		progress <- models.Progress{}.FromImportResult(result)
+	}
+
+	err = processor.ImportBackend().FinishImport()
+	if err != nil {
+		handleError(result, err, out, progress)
+		return
+	}
+
+	progress <- models.Progress{}.FromImportResult(result).Complete()
+	out <- result
+}
+
+func handleError(result models.ImportResult, err error, out chan models.ImportResult, progress chan models.Progress) {
+	result.Error = err
+	progress <- models.Progress{}.FromImportResult(result).Complete()
+	out <- result
+}