import { Download } from '../../shared/interfaces/download.interface'
import { IPCEmitHandler } from '../../shared/IPCHandler'
import { ChartDownload } from './ChartDownload'
import { DownloadQueue } from './DownloadQueue'

class DownloadHandler implements IPCEmitHandler<'download'> {
	event = 'download' as const

	downloadQueue: DownloadQueue = new DownloadQueue()
	currentDownload: ChartDownload = undefined
	retryWaiting: ChartDownload[] = []

	handler(data: Download) {
		switch (data.action) {
			case 'add': this.addDownload(data); break
			case 'retry': this.retryDownload(data); break
			case 'cancel': this.cancelDownload(data); break
		}
	}

	private addDownload(data: Download) {
		const filesHash = data.data.driveData.filesHash // Note: using versionID would cause chart packs to download multiple times
		if (this.currentDownload?.hash == filesHash || this.downloadQueue.isDownloadingLink(filesHash)) {
			return
		}

		const newDownload = new ChartDownload(data.versionID, data.data)
		this.addDownloadEventListeners(newDownload)
		if (this.currentDownload == undefined) {
			this.currentDownload = newDownload
			newDownload.beginDownload()
		} else {
			this.downloadQueue.push(newDownload)
		}
	}

	private retryDownload(data: Download) {
		const index = this.retryWaiting.findIndex(download => download.versionID == data.versionID)
		if (index != -1) {
			const retryDownload = this.retryWaiting.splice(index, 1)[0]
			retryDownload.displayRetrying()
			if (this.currentDownload == undefined) {
				this.currentDownload = retryDownload
				retryDownload.retry()
			} else {
				this.downloadQueue.push(retryDownload)
			}
		}
	}

	private cancelDownload(data: Download) {
		if (this.currentDownload?.versionID == data.versionID) {
			this.currentDownload.cancel()
			this.currentDownload = undefined
			this.startNextDownload()
		} else {
			this.downloadQueue.remove(data.versionID)
		}
	}

	private addDownloadEventListeners(download: ChartDownload) {
		download.on('complete', () => {
			this.currentDownload = undefined
			this.startNextDownload()
		})

		download.on('error', () => {
			this.retryWaiting.push(this.currentDownload)
			this.currentDownload = undefined
			this.startNextDownload()
		})
	}

	private startNextDownload() {
		if (!this.downloadQueue.isEmpty()) {
			this.currentDownload = this.downloadQueue.shift()
			if (this.currentDownload.hasFailed) {
				this.currentDownload.retry()
			} else {
				this.currentDownload.beginDownload()
			}
		}
	}
}

export const downloadHandler = new DownloadHandler()