import type { Byline } from '@/lib/articleTypes'
import { SEO_KEYS, type ArticleSeo, type SeoKey } from '@/lib/articleSeo'

export interface StoredDraft {
	title?: string
	body?: string
	meta?: { site_id: number | null; authors: Byline[] }
	seo?: ArticleSeo
	mirrored_at: string
}

const DRAFT_PREFIX = 'renewcms:article-draft:'

const NULLABLE_NUMBER_KEYS: SeoKey[] = ['cover_image_id', 'social_image_id']
const BOOLEAN_KEYS: SeoKey[] = ['noindex']

type UnknownRecord = Record<string, unknown>

function isRecord(value: unknown): value is UnknownRecord {
	return typeof value === 'object' && value !== null && !Array.isArray(value)
}

function isOptionalString(value: unknown) {
	return value === undefined || typeof value === 'string'
}

function isNullableNumber(value: unknown) {
	return value === null || typeof value === 'number'
}

function isByline(value: unknown) {
	return (
		isRecord(value) &&
		typeof value.id === 'number' &&
		typeof value.name === 'string' &&
		typeof value.slug === 'string'
	)
}

function isMeta(value: unknown) {
	return (
		value === undefined ||
		(isRecord(value) &&
			isNullableNumber(value.site_id) &&
			Array.isArray(value.authors) &&
			value.authors.every(isByline))
	)
}

function isSeoValue(key: SeoKey, value: unknown) {
	if (NULLABLE_NUMBER_KEYS.includes(key)) {
		return isNullableNumber(value)
	}
	return BOOLEAN_KEYS.includes(key) ? typeof value === 'boolean' : typeof value === 'string'
}

function isSeo(value: unknown) {
	return (
		value === undefined ||
		(isRecord(value) &&
			SEO_KEYS.every((key) => value[key] === undefined || isSeoValue(key, value[key])))
	)
}

function isMirrorTime(value: unknown) {
	return typeof value === 'string' && !Number.isNaN(new Date(value).getTime())
}

function isStoredDraft(value: unknown): value is StoredDraft {
	return (
		isRecord(value) &&
		isOptionalString(value.title) &&
		isOptionalString(value.body) &&
		isMeta(value.meta) &&
		isSeo(value.seo) &&
		isMirrorTime(value.mirrored_at)
	)
}

function keyOf(userId: number, articleId: number) {
	return `${DRAFT_PREFIX}${userId}:${articleId}`
}

export function readStoredDraft(userId: number | null, articleId: number): StoredDraft | null {
	if (userId === null) {
		return null
	}
	try {
		const raw = sessionStorage.getItem(keyOf(userId, articleId))
		const parsed: unknown = raw === null ? null : JSON.parse(raw)
		return isStoredDraft(parsed) ? parsed : null
	} catch {
		return null
	}
}

export function writeStoredDraft(userId: number | null, articleId: number, draft: StoredDraft) {
	if (userId === null) {
		return
	}
	try {
		sessionStorage.setItem(keyOf(userId, articleId), JSON.stringify(draft))
	} catch {
		return
	}
}

export function removeStoredDraft(userId: number | null, articleId: number) {
	if (userId === null) {
		return
	}
	try {
		sessionStorage.removeItem(keyOf(userId, articleId))
	} catch {
		return
	}
}

export function removeStoredDraftsOf(userId: number | undefined) {
	if (userId === undefined) {
		return
	}
	try {
		const prefix = `${DRAFT_PREFIX}${userId}:`
		const owned = Object.keys(sessionStorage).filter((key) => key.startsWith(prefix))
		owned.forEach((key) => sessionStorage.removeItem(key))
	} catch {
		return
	}
}