scotty/internal/backends/import.go

/*
Copyright © 2023-2025 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 (
	"context"
	"sync"

	"go.uploadedlobster.com/scotty/internal/models"
)

type ImportProcessor[T models.ListensResult | models.LovesResult] interface {
	ImportBackend() models.ImportBackend
	Process(ctx context.Context, wg *sync.WaitGroup, results chan T, out chan models.ImportResult, progress chan models.TransferProgress)
	Import(export T, result models.ImportResult, out chan models.ImportResult, progress chan models.TransferProgress) (models.ImportResult, error)
}

type ListensImportProcessor struct {
	Backend models.ListensImport
}

func (p ListensImportProcessor) ImportBackend() models.ImportBackend {
	return p.Backend
}

func (p ListensImportProcessor) Process(ctx context.Context, wg *sync.WaitGroup, results chan models.ListensResult, out chan models.ImportResult, progress chan models.TransferProgress) {
	process(ctx, wg, p, results, out, progress)
}

func (p ListensImportProcessor) Import(export models.ListensResult, result models.ImportResult, out chan models.ImportResult, progress chan models.TransferProgress) (models.ImportResult, error) {
	if export.Error != nil {
		return result, export.Error
	}

	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 {
		return importResult, err
	}
	return importResult, nil
}

type LovesImportProcessor struct {
	Backend models.LovesImport
}

func (p LovesImportProcessor) ImportBackend() models.ImportBackend {
	return p.Backend
}

func (p LovesImportProcessor) Process(ctx context.Context, wg *sync.WaitGroup, results chan models.LovesResult, out chan models.ImportResult, progress chan models.TransferProgress) {
	process(ctx, wg, p, results, out, progress)
}

func (p LovesImportProcessor) Import(export models.LovesResult, result models.ImportResult, out chan models.ImportResult, progress chan models.TransferProgress) (models.ImportResult, error) {
	if export.Error != nil {
		return result, export.Error
	}

	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 {
		return importResult, err
	}
	return importResult, nil
}

func process[R models.LovesResult | models.ListensResult, P ImportProcessor[R]](
	ctx context.Context, wg *sync.WaitGroup,
	processor P, results chan R,
	out chan models.ImportResult,
	progress chan models.TransferProgress,
) {
	wg.Add(1)
	defer wg.Done()
	defer close(out)
	result := models.ImportResult{}
	p := models.TransferProgress{}

	if err := processor.ImportBackend().StartImport(); err != nil {
		out <- handleError(result, err, progress)
		return
	}

	for exportResult := range results {
		select {
		case <-ctx.Done():
			processor.ImportBackend().FinishImport()
			out <- handleError(result, ctx.Err(), progress)
			return
		default:
			importResult, err := processor.Import(exportResult, result, out, progress)
			result.Update(importResult)
			if err != nil {
				processor.ImportBackend().FinishImport()
				out <- handleError(result, err, progress)
				return
			}
			progress <- p.FromImportResult(result, false)
		}
	}

	if err := processor.ImportBackend().FinishImport(); err != nil {
		out <- handleError(result, err, progress)
		return
	}

	progress <- p.FromImportResult(result, true)
	out <- result
}

func handleError(result models.ImportResult, err error, progress chan models.TransferProgress) models.ImportResult {
	result.Error = err
	p := models.TransferProgress{}.FromImportResult(result, false)
	p.Import.Abort()
	progress <- p
	return result
}