import { URL } from 'node:url';
import { Inject, Injectable } from '@nestjs/common';
import * as parse5 from 'parse5';
import { Window } from 'happy-dom';
import { DI } from '@/di-symbols.js';
import type { Config } from '@/config.js';
import { intersperse } from '@/misc/prelude/array.js';
import type { IMentionedRemoteUsers } from '@/models/entities/Note.js';
import { bindThis } from '@/decorators.js';
import * as TreeAdapter from '../../node_modules/parse5/dist/tree-adapters/default.js';
import type * as mfm from 'mfm-js';

const treeAdapter = TreeAdapter.defaultTreeAdapter;

const urlRegex = /^https?:\/\/[\w\/:%#@$&?!()\[\]~.,=+\-]+/;
const urlRegexFull = /^https?:\/\/[\w\/:%#@$&?!()\[\]~.,=+\-]+$/;

@Injectable()
export class MfmService {
	constructor(
		@Inject(DI.config)
		private config: Config,
	) {
	}

	@bindThis
	public fromHtml(html: string, hashtagNames?: string[]): string {
		// some AP servers like Pixelfed use br tags as well as newlines
		html = html.replace(/<br\s?\/?>\r?\n/gi, '\n');

		const dom = parse5.parseFragment(html);

		let text = '';

		for (const n of dom.childNodes) {
			analyze(n);
		}

		return text.trim();

		function getText(node: TreeAdapter.Node): string {
			if (treeAdapter.isTextNode(node)) return node.value;
			if (!treeAdapter.isElementNode(node)) return '';
			if (node.nodeName === 'br') return '\n';

			if (node.childNodes) {
				return node.childNodes.map(n => getText(n)).join('');
			}

			return '';
		}

		function appendChildren(childNodes: TreeAdapter.ChildNode[]): void {
			if (childNodes) {
				for (const n of childNodes) {
					analyze(n);
				}
			}
		}

		function analyze(node: TreeAdapter.Node) {
			if (treeAdapter.isTextNode(node)) {
				text += node.value;
				return;
			}

			// Skip comment or document type node
			if (!treeAdapter.isElementNode(node)) return;

			switch (node.nodeName) {
				case 'br': {
					text += '\n';
					break;
				}

				case 'a':
				{
					const txt = getText(node);
					const rel = node.attrs.find(x => x.name === 'rel');
					const href = node.attrs.find(x => x.name === 'href');

					// ハッシュタグ
					if (hashtagNames && href && hashtagNames.map(x => x.toLowerCase()).includes(txt.toLowerCase())) {
						text += txt;
					// メンション
					} else if (txt.startsWith('@') && !(rel && rel.value.startsWith('me '))) {
						const part = txt.split('@');

						if (part.length === 2 && href) {
							//#region ホスト名部分が省略されているので復元する
							const acct = `${txt}@${(new URL(href.value)).hostname}`;
							text += acct;
							//#endregion
						} else if (part.length === 3) {
							text += txt;
						}
					// その他
					} else {
						const generateLink = () => {
							if (!href && !txt) {
								return '';
							}
							if (!href) {
								return txt;
							}
							if (!txt || txt === href.value) {	// #6383: Missing text node
								if (href.value.match(urlRegexFull)) {
									return href.value;
								} else {
									return `<${href.value}>`;
								}
							}
							if (href.value.match(urlRegex) && !href.value.match(urlRegexFull)) {
								return `[${txt}](<${href.value}>)`;	// #6846
							} else {
								return `[${txt}](${href.value})`;
							}
						};

						text += generateLink();
					}
					break;
				}

				case 'h1':
				{
					text += '【';
					appendChildren(node.childNodes);
					text += '】\n';
					break;
				}

				case 'b':
				case 'strong':
				{
					text += '**';
					appendChildren(node.childNodes);
					text += '**';
					break;
				}

				case 'small':
				{
					text += '<small>';
					appendChildren(node.childNodes);
					text += '</small>';
					break;
				}

				case 's':
				case 'del':
				{
					text += '~~';
					appendChildren(node.childNodes);
					text += '~~';
					break;
				}

				case 'i':
				case 'em':
				{
					text += '<i>';
					appendChildren(node.childNodes);
					text += '</i>';
					break;
				}

				// block code (<pre><code>)
				case 'pre': {
					if (node.childNodes.length === 1 && node.childNodes[0].nodeName === 'code') {
						text += '\n```\n';
						text += getText(node.childNodes[0]);
						text += '\n```\n';
					} else {
						appendChildren(node.childNodes);
					}
					break;
				}

				// inline code (<code>)
				case 'code': {
					text += '`';
					appendChildren(node.childNodes);
					text += '`';
					break;
				}

				case 'blockquote': {
					const t = getText(node);
					if (t) {
						text += '\n> ';
						text += t.split('\n').join('\n> ');
					}
					break;
				}

				case 'p':
				case 'h2':
				case 'h3':
				case 'h4':
				case 'h5':
				case 'h6':
				{
					text += '\n\n';
					appendChildren(node.childNodes);
					break;
				}

				// other block elements
				case 'div':
				case 'header':
				case 'footer':
				case 'article':
				case 'li':
				case 'dt':
				case 'dd':
				{
					text += '\n';
					appendChildren(node.childNodes);
					break;
				}

				default:	// includes inline elements
				{
					appendChildren(node.childNodes);
					break;
				}
			}
		}
	}

	@bindThis
	public toHtml(nodes: mfm.MfmNode[] | null, mentionedRemoteUsers: IMentionedRemoteUsers = []) {
		if (nodes == null) {
			return null;
		}

		const { window } = new Window();

		const doc = window.document;

		function appendChildren(children: mfm.MfmNode[], targetElement: any): void {
			if (children) {
				for (const child of children.map(x => (handlers as any)[x.type](x))) targetElement.appendChild(child);
			}
		}

		const handlers: { [K in mfm.MfmNode['type']]: (node: mfm.NodeType<K>) => any } = {
			bold: (node) => {
				const el = doc.createElement('b');
				appendChildren(node.children, el);
				return el;
			},

			small: (node) => {
				const el = doc.createElement('small');
				appendChildren(node.children, el);
				return el;
			},

			strike: (node) => {
				const el = doc.createElement('del');
				appendChildren(node.children, el);
				return el;
			},

			italic: (node) => {
				const el = doc.createElement('i');
				appendChildren(node.children, el);
				return el;
			},

			fn: (node) => {
				const el = doc.createElement('i');
				appendChildren(node.children, el);
				return el;
			},

			blockCode: (node) => {
				const pre = doc.createElement('pre');
				const inner = doc.createElement('code');
				inner.textContent = node.props.code;
				pre.appendChild(inner);
				return pre;
			},

			center: (node) => {
				const el = doc.createElement('div');
				appendChildren(node.children, el);
				return el;
			},

			emojiCode: (node) => {
				return doc.createTextNode(`\u200B:${node.props.name}:\u200B`);
			},

			unicodeEmoji: (node) => {
				return doc.createTextNode(node.props.emoji);
			},

			hashtag: (node) => {
				const a = doc.createElement('a');
				a.setAttribute('href', `${this.config.url}/tags/${node.props.hashtag}`);
				a.textContent = `#${node.props.hashtag}`;
				a.setAttribute('rel', 'tag');
				return a;
			},

			inlineCode: (node) => {
				const el = doc.createElement('code');
				el.textContent = node.props.code;
				return el;
			},

			mathInline: (node) => {
				const el = doc.createElement('code');
				el.textContent = node.props.formula;
				return el;
			},

			mathBlock: (node) => {
				const el = doc.createElement('code');
				el.textContent = node.props.formula;
				return el;
			},

			link: (node) => {
				const a = doc.createElement('a');
				a.setAttribute('href', node.props.url);
				appendChildren(node.children, a);
				return a;
			},

			mention: (node) => {
				const a = doc.createElement('a');
				const { username, host, acct } = node.props;
				const remoteUserInfo = mentionedRemoteUsers.find(remoteUser => remoteUser.username === username && remoteUser.host === host);
				a.setAttribute('href', remoteUserInfo ? (remoteUserInfo.url ? remoteUserInfo.url : remoteUserInfo.uri) : `${this.config.url}/${acct}`);
				a.className = 'u-url mention';
				a.textContent = acct;
				return a;
			},

			quote: (node) => {
				const el = doc.createElement('blockquote');
				appendChildren(node.children, el);
				return el;
			},

			text: (node) => {
				const el = doc.createElement('span');
				const nodes = node.props.text.split(/\r\n|\r|\n/).map(x => doc.createTextNode(x));

				for (const x of intersperse<FIXME | 'br'>('br', nodes)) {
					el.appendChild(x === 'br' ? doc.createElement('br') : x);
				}

				return el;
			},

			url: (node) => {
				const a = doc.createElement('a');
				a.setAttribute('href', node.props.url);
				a.textContent = node.props.url;
				return a;
			},

			search: (node) => {
				const a = doc.createElement('a');
				a.setAttribute('href', `https://www.google.com/search?q=${node.props.query}`);
				a.textContent = node.props.content;
				return a;
			},

			plain: (node) => {
				const el = doc.createElement('span');
				appendChildren(node.children, el);
				return el;
			},
		};

		appendChildren(nodes, doc.body);

		return `<p>${doc.body.innerHTML}</p>`;
	}
}