/*
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
}