import { ReactNode } from 'react';
import ReactMarkdown from 'react-markdown';
import { readdirSync, readFileSync } from 'fs';
import { join } from 'path';

import Seperator from '../../components/seperator';
import Navbar from '../../components/navbar';
// import Button from '../../components/button';
import Image from '../../components/image';
import Chapters, { chapter } from '../../components/chapters';
import Tags from '../../components/tag';

interface ArticleMeta {
	title?: string;
	subtitle?: string;
	author?: string;
	tags?: Array<string>;
	date?: string;
	chapters?: Array<chapter>;
}

var headingLevel = (input: string) => input?.match(/^[#]+/)[0]?.length || 0;

var sectionID = (input: string) => input
	.replace(/[()\[\]{}!@#$%^&*<>?,./\;':"\\|=+]/g, "")
	.replace(/\s/g, "-")
	.toLowerCase();

function Heading(props: {
	children?: ReactNode;
	level?: number;
}) {
	var HeadingTag = "h" + props.level as keyof JSX.IntrinsicElements;
	return <HeadingTag id={sectionID(props.children[0].props.children)} children={props.children}/>
}

export default function Post(props: {
	content: string,
	meta: ArticleMeta
}) {
	return <div>
		<div className="centeredPage">
			<div className="titleWrapper">
				<h1>{props.meta.title}</h1>
				<p className="subtile">{props.meta.subtitle}</p>
				{ props.meta.tags && <Tags tags={props.meta.tags}/> }
			</div>
			<div className="navAreaWrapper">
				<div className="sticky">
					<Navbar/>
					<Chapters chapters={props.meta.chapters}/>
				</div>
			</div>
			<div className="contentWrapper">
				<ReactMarkdown
				children={props.content}
				renderers={{
					image: Image,
					thematicBreak: Seperator,
					heading: Heading,
				}}/>
			</div>
		</div>
	</div>
}

var parseTag = {
	"title": (val: string) => val,
	"subtitle": (val: string) => val,
	"author": (val: string) => val,
	"tags": (val: string) => val.split(",").map(i => i.trim()),
	"date": (val: string) => new Date(val).toDateString(),
}

function parseMeta(file: Array<string>): ArticleMeta {
	var meta: ArticleMeta = {};

	file.forEach(line => {
		if (!line.startsWith("[meta]: ")) return;
		var tags = line.match(/\[meta\]:\s+\<(.+?)\>\s+\((.+?)\)/);
		if (!tags || !tags[1] || !tags[2]) return;
		if (!parseTag.hasOwnProperty(tags[1])) return;
		meta[tags[1]] = parseTag[tags[1]](tags[2]);
	});

	return meta;
}

function parseToCRecursive(headings: Array<string>): Array<chapter> {
	interface WIPchapter extends chapter {
		unparsedChildren?: Array<string>;
	}
	var children: Array<WIPchapter> = []

	var lowestLevel = headingLevel(headings[0]);
	var currentChildIndex = -1;
	for (var i in headings) {
		var localLevel = headingLevel(headings[i]);
		if (localLevel == lowestLevel) {
			var chapterName = headings[i].match(/^[#]+\s+(.+)/)[1];
			children.push({
				name: chapterName,
				sectionLink: sectionID(chapterName),
				unparsedChildren: [],
			});
			currentChildIndex += 1;
		} else {
			children[currentChildIndex].unparsedChildren.push(headings[i])
		}
	}

	children.map(child => {
		child.children = parseToCRecursive(child.unparsedChildren)
		delete child.unparsedChildren;

		return child
	})

	return children as Array<chapter>;
}

function parseToC(file: Array<string>): Array<chapter> {
	var chapterStrings = file.filter(line => line.startsWith("#"));
	return parseToCRecursive(chapterStrings);
}

function preprocessor(fileContent: string) {
	var fileAsArr = fileContent.split("\n");
	var meta = parseMeta(fileAsArr);
	meta.chapters = parseToC(fileAsArr);
	var result = fileAsArr.join("\n").trim()
	return { meta, result }
}

export function getStaticProps(props: {params: { id: string }}) {
	var filename = join("posts/", props.params.id + ".md")
	var filecontent = readFileSync(filename).toString().trim()

	var parsed = preprocessor(filecontent);

	return {
		props: {
			content: parsed.result,
			meta: parsed.meta,
		},
	}
}

export function getStaticPaths() {
	var files = readdirSync("posts").filter(f => f.endsWith(".md"));

	return {
		paths: files.map((f) => {
			return {
				params: {
					id: f.substr(0, f.length - 3)
				}
			}
		}),
		fallback: false,
	}
}