import type { InstallJobSnapshot, InstallJobStatus } from '@/helpers/install'

export type DownloadsTab = 'active' | 'history'

export interface DownloadFocusState {
	jobId: string | null
	focused: boolean
	autoFollow: boolean
	lastStatus: InstallJobStatus | null
}

export interface DownloadFocusEffect {
	state: DownloadFocusState
	tab: DownloadsTab | null
	expand: boolean
	scroll: boolean
}

const ACTIVE_STATUSES = new Set<InstallJobStatus>([
	'queued',
	'running',
	'canceling',
	'waiting_for_user',
])

export function focusedDownloadJobId(value: unknown): string | null {
	return typeof value === 'string' && value.length > 0 ? value : null
}

export function createDownloadFocusState(jobId: string | null): DownloadFocusState {
	return {
		jobId,
		focused: false,
		autoFollow: jobId !== null,
		lastStatus: null,
	}
}

export function downloadTabForJob(job: InstallJobSnapshot): DownloadsTab {
	return ACTIVE_STATUSES.has(job.status) ? 'active' : 'history'
}

export function reconcileDownloadFocus(
	state: DownloadFocusState,
	job: InstallJobSnapshot | null,
): DownloadFocusEffect {
	if (!state.jobId || !job || job.job_id !== state.jobId) {
		return { state, tab: null, expand: false, scroll: false }
	}

	const targetTab = downloadTabForJob(job)
	if (!state.focused) {
		return {
			state: {
				...state,
				focused: true,
				autoFollow: targetTab === 'active',
				lastStatus: job.status,
			},
			tab: targetTab,
			expand: true,
			scroll: true,
		}
	}

	const completedWhileFollowing =
		state.autoFollow &&
		state.lastStatus !== null &&
		ACTIVE_STATUSES.has(state.lastStatus) &&
		targetTab === 'history'
	return {
		state: {
			...state,
			autoFollow: completedWhileFollowing ? false : state.autoFollow,
			lastStatus: job.status,
		},
		tab: completedWhileFollowing ? 'history' : null,
		expand: false,
		scroll: false,
	}
}

export function stopDownloadFocusAutoFollow(state: DownloadFocusState): DownloadFocusState {
	return { ...state, autoFollow: false }
}