import { charCount } from '@/lib/articleSeo'
import type { ArticleSeo } from '@/lib/articleSeo'
import type { Site } from '@/composables/useSites'

export type PreviewDevice = 'desktop' | 'mobile'

export const PREVIEW_LIMITS: Record<PreviewDevice, { title: number; description: number }> = {
	desktop: { title: 60, description: 160 },
	mobile: { title: 70, description: 120 },
}

export const TITLE_RANGE = { min: 30, max: 60 }
export const DESCRIPTION_RANGE = { min: 70, max: 160 }

const DEFAULT_TEMPLATE = '%title% | %site%'
const SENTENCE_END = /^(.+?[.!?])(\s|$)/s

export type TitleSource = 'seo_title' | 'title'
export type DescriptionSource = 'seo_description' | 'excerpt' | 'body' | 'site' | 'none'

export function truncateText(text: string, max: number) {
	const characters = [...text]
	return characters.length > max
		? `${characters
				.slice(0, max - 1)
				.join('')
				.trimEnd()}…`
		: text
}

const BLOCK_BOUNDARY = /<\/?(p|div|h[1-6]|li|ul|ol|blockquote|pre|tr|br|hr)\b[^>]*>/gi
const SKIPPED_ELEMENTS = 'script, style'

export function bodyText(html: string) {
	const parsed = new DOMParser().parseFromString(
		html.replace(BLOCK_BOUNDARY, ' $& '),
		'text/html',
	)
	parsed.querySelectorAll(SKIPPED_ELEMENTS).forEach((element) => element.remove())
	return (parsed.body.textContent ?? '').replace(/\s+/g, ' ').trim()
}

export function firstSentence(html: string) {
	const text = bodyText(html)
	const match = SENTENCE_END.exec(text)
	return match ? match[1]! : text
}

const TEMPLATE_TOKEN = /%title%|%site%/g

export function applyTitleTemplate(template: string, title: string, siteName: string) {
	return (template || DEFAULT_TEMPLATE)
		.replace(TEMPLATE_TOKEN, (token) => (token === '%title%' ? title : siteName))
		.trim()
}

export function siteDisplayName(site: Site | undefined) {
	return site?.site_name || site?.name || ''
}

export interface SeoPreviewInput {
	seo: ArticleSeo
	title: string
	body: string
	site: Site | undefined
}

export function previewTitleSource(input: SeoPreviewInput): TitleSource {
	return input.seo.seo_title.trim() ? 'seo_title' : 'title'
}

export function previewTitle(input: SeoPreviewInput) {
	const base = input.seo.seo_title.trim() || input.title
	return applyTitleTemplate(input.site?.title_template ?? '', base, siteDisplayName(input.site))
}

export function previewDescriptionSource(input: SeoPreviewInput): DescriptionSource {
	if (input.seo.seo_description.trim()) {
		return 'seo_description'
	}
	if (input.seo.excerpt.trim()) {
		return 'excerpt'
	}
	if (firstSentence(input.body)) {
		return 'body'
	}
	return input.site?.default_description ? 'site' : 'none'
}

export function previewDescription(input: SeoPreviewInput) {
	const sources: Record<DescriptionSource, string> = {
		seo_description: input.seo.seo_description.trim(),
		excerpt: input.seo.excerpt.trim(),
		body: firstSentence(input.body),
		site: input.site?.default_description ?? '',
		none: '',
	}
	return sources[previewDescriptionSource(input)]
}

export function titleIsCut(title: string, device: PreviewDevice) {
	return charCount(title) > PREVIEW_LIMITS[device].title
}

export function socialTitle(input: SeoPreviewInput) {
	return input.seo.social_title.trim() || previewTitle(input)
}

export function socialDescription(input: SeoPreviewInput) {
	return input.seo.social_description.trim() || previewDescription(input)
}

export function hasSocialOverrides(seo: ArticleSeo) {
	return Boolean(seo.social_title || seo.social_description || seo.social_image_id !== null)
}

export type SocialImageSource = 'social' | 'cover' | 'site' | 'none'

export function socialImageSource(seo: ArticleSeo, siteHasImage: boolean): SocialImageSource {
	if (seo.social_image_id !== null) {
		return 'social'
	}
	if (seo.cover_image_id !== null) {
		return 'cover'
	}
	return siteHasImage ? 'site' : 'none'
}