// Get the libraries
const fs = require('fs'); // For modifying and reading files
const express = require('express'); // For running a webserver in nodejs
const showdown  = require('showdown') // For converting markdown to html on demand, https://showdownjs.com/
const crypto = require('crypto'); // For encrypting passwords, I use sha512
// fromUnixTime(): Create a date from a Unix timestamp (in seconds). Decimal values will be discarded.
// format(): Return the formatted date string in the given format. The result may vary by locale.
// getUnixTime(): Get the seconds timestamp of the given date.
// find out more at https://date-fns.org/ \or docs: https://date-fns.org/docs/Getting-Startedyyyyyyyy
const { fromUnixTime, format, getUnixTime } = require("date-fns") // A date utility library

// There's only one possible argument, so we can just check if the user passed that one
// TODO I plan on adding more such as --help and --post so I should make this more robust at some point
if (process.argv[2] == "--first-time") {
    initialise() // Creates any files such users.js, posts.js, comments.js or config.js if they are not present
}

// Define the modules now so they are global
let users // contains a list of users, each user is an object containing username,prettyname,hash and description
let posts // contains a list of posts,
let comments // contains a list of comments
let config // contains a set of configuration for the site, see example-config.js for an example

try {
    // We're going to try and import the modules,
    users = require('./users.js');
    posts = require('./posts.js');
    comments = require('./comments.js');
    config = require('./config.js');
}
catch (error) {
    // if they don't all import then 
    // inform the user to pass --first-time and exit with an error code
    console.log("A file is missing!")
    console.log("Run with --first-time to initialise the program")
    console.log(error)
    process.exit(1)
}

// https://showdownjs.com/docs/available-options
let converter = new showdown.Converter({
    simpleLineBreaks: true, // Parse line breaks as <br/> in paragraphs (GitHub-style behavior).
    tables: true, // Enable support for tables syntax.
    strikethrough: true, // Enable support for strikethrough: ~~text~~
    tasklists: true, // Enable support for GitHub style tasklists. - [x] and - [ ]
    encodeEmails: true, //Enable automatic obfuscation of email addresses. emails are encoded via character entities
    headerLevelStart: 3, //Set starting level for the heading tags.
})

// The footer div is globale because it's a site wide, so define it here
let footer_div = config.site_wide_footer
footer_div = replace_format_indicators(footer_div)

// Define stuff to do with express (nodejs webserver)
const app = express();
app.use(express.urlencoded({ extended: true }));
app.use(express.json());
app.use(express.static(config.root_path));

// Initialise the program by creating users.js, comments.js, posts.js and config.js
// All require default content in them to start off with
// Then exit successfully
// returns nothing
function initialise() {
    try {
        const users = require("./users.js");
    }
    catch (error) {
        console.log("Creating users file")
        fs.writeFileSync(`${__dirname}/users.js`, `export const users = []`)
    }
    try {
        const posts = require("./posts.js");
    }
    catch (error) {
        console.log("Creating posts file")
        fs.writeFileSync(`${__dirname}/posts.js`, `export const posts = []`)
    }
    try {
        const comments = require("./comments.js");
    }
    catch (error) {
        console.log("Creating comments file")
        fs.writeFileSync(`${__dirname}/comments.js`, `export const comments = []\nexport const counter = 0`)
    }
    try {
        const config = require("./config.js");
    }
    catch (error) {
        console.log("Copying the example config to config.js")
        console.log("!!! PLEASE MODIFY config.js TO YOUR NEEDS !!!")
        fs.copyFile('example-config.js', 'config.js', (err) => {
            console.log("Error copying file")
        })
    }
    console.log("Successfully initialised")
    process.exit(0)
}

// The users are stored as a list of objects [ user_object, user_object, user_object ]
// So you cannot easily find the userID (position in list) from the username
// This function returns the username for a given userID by looping over every user
// if the user is present, it returns the index of the user (integer)
// if the user is not present it returns -1
function get_userID(username) {
	for (let i = 0; i < users.users.length; i++) { // Loop over every user
		if (users.users[i]['username'] == username) {
			return i // If the username matches then return the index of that user
		}
	}
	return -1 // If user is not present, return -1
}

// The configuration defines a date format using the date-fns (a datetime library) syntax 
// eg "yyyy-MM-dd"
// this converts unix time (an integer) into a string that is formatted according to config.js
// uses date-fns's fromUnixTime() and format() functions
// returns the formatted date (string)
function unix_time_to_date_format(unix_time) {
	date = fromUnixTime(unix_time)
	formatted_date = format(date, config.date_format)
	return formatted_date
}

// This is similar to the above function, however, instead of formatting to the users
// configuration, it formats to RFC-822 which is the date format used by RSS feeds
// eg "Mon, 23 May 2025 18:59:59 +0100"
// accepts unix time (int)
// returns the formatted date (string)
function unix_time_to_rss_date(unix_time) {
	date = fromUnixTime(unix_time)
	formatted_date = format(date, "EEE, dd MMM yyyy HH:mm:ss")
	return `${formatted_date} ${config.time_zone}`
}

// This function accepts a list of strings eg ["string1","string2,"string3"] (any length)
// then returns a string of them each pointing to a seperate url
// eg "<a href="/tag/string1">string1</a>, <a href="/tag/string2">string2</a>, <a href="/tag/string3">string3</a>"
// this is so you can have a list of tags that each point to their individual tag page
// returns: string
function hyperlink_tags(tags) {
	string = "" // Initialises the string
	for (let tag_index = 0; tag_index < tags.length; tag_index++) { // Loop over each tag
		string += `<a href="/tag/${tags[tag_index]}">${tags[tag_index]}</a>` // Adds the tag to the string as a HTML href
		if (tag_index < tags.length - 1) { // If there are more tags, then insert a comma
			string += ", ";
		}
	}
	return string
}

// See the readme format indicators section for a full list of format indicators
// This function replaces the format indicators in a template to the content they represent
// accepts the template (string),
// the post index (int) as an optional paramter to indicate what post is to be used (for replacing things like content and titles of posts)
// the tag (strig) as an optional parameter to indicate what tag is being used (for /tag/:tag pages)
// the user index (int) is an optional parameter to indicate what user is to be used (for replacng things like the header of the user page)
// returns the template with it's format indiactors replaced (string)
function replace_format_indicators(template, post_index=-1, tag_name="tag", user_index=-1) {
    output_string = template // These should always be replaceable
            .replaceAll("%%", "&#37;")
            .replaceAll("%J", "/delete_account")
            .replaceAll("%P", "/post")
            .replaceAll("%O", `/edit/${post_index}`)
            .replaceAll("%Q", "/signup")
            .replaceAll("%R", "/rss")
            .replaceAll("%Y", config.site_name)
            .replaceAll("%W", config.site_description)
            .replaceAll("%Z", config.attribution)
            .replaceAll("%S", config.seperator)
    if (post_index >= 0) { // These can only be replaced if a post is specified (by default the post id is -1)
	    post_object = posts.posts[post_index] // Defines the post object for easy reference
        output_string = output_string
            .replaceAll("%A", (post_object["tags"]))
            .replaceAll("%B", (hyperlink_tags(post_object["tags"])))
            .replaceAll("%C", converter.makeHtml(post_object["content"]))
            .replaceAll("%D", unix_time_to_date_format(post_object["pubdate"]))
            .replaceAll("%E", unix_time_to_date_format(post_object["editdate"]))
            .replaceAll("%F", users.users[post_object["userID"]]['prettyname'])
            .replaceAll("%G", tag_name)
            .replaceAll("%I", converter.makeHtml(users.users[post_object['userID']]['description']))
            .replaceAll("%L", `/post/${post_index}`)
            .replaceAll("%M", return_comments(post_index))
            .replaceAll("%N", users.users[post_object["userID"]]['username'])
            .replaceAll("%S", config.seperator)
            .replaceAll("%T", post_object["title"])
            .replaceAll("%U", `/user/${users.users[post_object["userID"]]['username']}`)
            .replaceAll("%X", `<form method="POST" action="/submit_comment">
                    <input type="hidden" name="post_index" value="${post_index}">
                    <input placeholder="username" name="name"><br/>
                    <textarea placeholder="comment" name="content"></textarea><br/>
                    <button type="submit">Submit</button>
                </form>`)
    }
    if (user_index >= 0) { // these should only be replaced if a user is specified (by default the user id is -1)
        output_string = output_string
            .replaceAll("%F", users.users[user_index]['prettyname'])
            .replaceAll("%G", tag_name)
            .replaceAll("%I", converter.makeHtml(users.users[user_index]['description']))
            .replaceAll("%L", `/post/${post_index}`)
            .replaceAll("%N", users.users[user_index]['username'])
            .replaceAll("%S", config.seperator)
            .replaceAll("%U", `/user/${users.users[user_index]['username']}`)
    }
    if (config.enable_hitcount == true) { // Finally, the hitcounter should only be replaced if config.enable_hitcount is true
        output_string = output_string
            .replaceAll("%H", fs.readFileSync('hitcount.txt'))
    }

	return output_string
}

// This escapes some potentially dangerous HTML characters with their HTML entities
// https://www.freeformatter.com/html-entities.html
// accepts a string
// returns a string with some character replaced by their entities
function escape_input(input) {
    let output = input
        .replaceAll("<", "&lt;")
        .replaceAll(">", "&gt;")
        .replaceAll("\\", "&#92;")
        .replaceAll('"', "&#34;")
        .replaceAll("'", "&#39;")
        .replaceAll("/", "&#47;")
        .replaceAll("%", "&#37;")
    return output
}

// TODO make the formatting customisable
function return_comments(post_id) {
    const post_comments = comments.comments[post_id]
    let comment_content = ""
    for (let comment_index = 0; comment_index < post_comments.length; comment_index++) {
        let comment = {...post_comments[comment_index]};
        comment['content'] = comment['content']
            .replaceAll(/>> ([0-9]*)/g, "<a href='#$1'>>> $1</a>")
            .replaceAll(/&gt;&gt; ([0-9]*)/g, "<a href='#$1'>>> $1</a>")
            .replaceAll("\n", "<br/>")
        comment_content += `<div id="${comment['id']}">${comment['name']} ${unix_time_to_date_format(comment['pubdate'])} No. ${comment['id']}<br/>${comment['content']}</div><br/>`
    }
    return comment_content
}

// RSS protocol gets
app.get(config.rss_path, (req,res) => {
	if (config.rss == false) {
		res.send("Sorry, RSS is disabled!")
	}
	else {
		let rss_content = `<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0">
    <channel>
        <title>${config.site_name}</title>
        <link>${config.site_url}</link>
        <description>${config.site_description}</description>
        `
		for (let i = posts.posts.length-1; i >= 0; i--) {
		    rss_content += `
			<item>
			    <title>${posts.posts[i]["title"]}</title>
			    <link>${config.site_url}/post/${i}</link>
			    <description><![CDATA[${converter.makeHtml(posts.posts[i]["content"])}]]></description>
			    <guid isPermaLink="true">${config.site_url}/post/${i}</guid>
			    <pubDate>${unix_time_to_rss_date(posts.posts[i]['pubdate'])}</pubDate>`
			for (let j = 0; j < posts.posts[i]['tags'].length; j++) {
				rss_content += `<category><![CDATA[${posts.posts[i]['tags'][j]}]]></category>`
			};
			rss_content += "</item>"
		}
		rss_content += `
	    </channel>
	</rss>`
		res.setHeader('content-type', 'application/rss+xml');
		res.send(rss_content)
	};
});

app.get("/", (req,res) => {
	if (config.enable_hitcount) {
		let hitcount = parseInt(fs.readFileSync('hitcount.txt'))
		hitcount += 1
		console.log(`/ Is loaded, hitcount: ${hitcount}`)
		fs.writeFileSync(`${__dirname}/hitcount.txt`, `${hitcount}`, 'utf-8');
	}

	header_div = config.timeline_header
	header_div = replace_format_indicators(header_div);
	posts_div = "";
	counter = posts.posts.length - 1;
	while ((counter >= 0) && (counter > (posts.posts.length - (config.timeline_length + 1))))
	{
		let post = config.timeline_post_format;
		posts_div += replace_format_indicators(post, counter);
		counter -= 1;
	}
	res.send(`<html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body><div id="header">${header_div}</div><div id="posts">${posts_div}</div></body><footer>${footer_div}</footer></html>`);
}); // /
app.get("/user/:username", (req, res) => {
	header_div = config.user_page_header
	header_div = replace_format_indicators(header_div,-1,"tag",get_userID(req.params.username))
	posts_div = "";
	for (let post_index = posts.posts.length-1; post_index >= 0; post_index--)	{
		if (users.users[posts.posts[post_index]["userID"]]["username"] == req.params.username) {
			let post = config.user_post_format;
			posts_div += replace_format_indicators(post, post_index);
		}
	}
	res.send(`<html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body><div id="header">${header_div}</div><div id="posts">${posts_div}</div></body><footer>${footer_div}</footer></html>`);
}); // /user/:username
app.get("/post/:post_index", (req, res) => {
	post_div = "";
	let post = config.post_page_format;
	post_div += replace_format_indicators(post, req.params.post_index);
	res.send(`<html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body><div id="posts">${post_div}</div></body><footer>${footer_div}</footer></html>`);
}); // /post/:post_index
app.get("/tag/:tag", (req,res) => {
	const tag = req.params.tag
	let header_div = config.tag_page_header
	header_div = replace_format_indicators(header_div,0,tag)
	let page_content = ""
	for (let i = posts.posts.length-1; i >= 0; i--) {
		if (posts.posts[i]['tags'].includes(tag)) {
			let post = config.tag_post_format;
			page_content += replace_format_indicators(post, i);
		};
	};
	res.send(`<html><style>${config.css}</style><body><div id="header">${header_div}</div><div id="posts">${page_content}</div></body><footer>${footer_div}</footer></html>`);
}); // /tag/:tag

app.get("/post", (req,res) => {
	res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><form action="/submit_post" method="POST">
	<input placeholder="username" required name="username"><br/>
	<input placeholder="password" type="password" required id="password" name="password"><br/>
	<input placeholder="title" required name="title"><br/>
	<textarea placeholder="post content*" required name="content"></textarea><br/>
	<input placeholder="Tags (comma seperated)" name="tags"><br/>
	<input type="submit" value="Submit"><br/>
    <small>* Markdown supported</small>
</form></html>`);
}); // /post
app.get("/signup", (req,res) => {
    // if the server does allow signup
    if (config.allow_signup == true) {
        // Send the page for signing up to the server
        res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><form action="/submit_signup" method="POST">
        <input placeholder="username" required name="username"><br/>
        <input placeholder="prettyname" required name="prettyname"><br/>
        <input placeholder="password" type="password" required id="password" name="password"><br/>
        <textarea placeholder="description (social links, what you do etc), supports markdown" id="description" name="description"></textarea><br/>
        <label>${config.signup_agreement}: </label><input type="checkbox" name="agreement" required><br/>
        <input type="submit" value="Submit"><br/></form></html>`);
    }
    // if the server does not allow signup
    else if (config.allow_signup == false) {
        res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body>${config.signups_unavailable}</body></html>`)
    }
    // If allow_signup is undefined or not a boolean, error
    else {
        res.redirect(301,"/")
        console.log("Error, invalid value for allow_signup (bool)")
    }
}); // /signup
app.get("/delete_account", (req,res) => {
        res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><form action="/submit_delete_account" method="POST">
        <input placeholder="username" required name="username"><br/>
        <input placeholder="password" type="password" required id="password" name="password"><br/>
        <label>${config.delete_account_confirmation}: </label><input type="checkbox" name="agreement" required><br/>
        <input type="submit" value="Submit"><br/></form></html>`);
}); // /delete_account
app.get("/edit/:post_id", (req,res) => {
	const post_id = req.params.post_id
	const post = posts.posts[post_id]
	const user = users.users[post['userID']]
	res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head>
	<form action="/submit_edit" method="POST" onsubmit="sha512password()">
		<input name="userID" type="hidden" value="${post['userID']}">
		<input name="postID" type="hidden" value="${post_id}">
		<input placeholder="${user['prettyname']}'s password" type="password" required id="password" name="password"><br/>
		<input placeholder="title" value="${post['title']}" required name="title"><br/>
		<textarea placeholder="content" required name="content">${post['content']}</textarea><br/>
		<input placeholder="tags (comma seperated)" value="${post['tags']}" name="tags"><br/>
		<label>Delete forever (no undo): </label><input name="delete" type="checkbox"><br/>
		<input type="submit" value="Submit"><br/>
        <small>* Markdown supported</small>
	</form></html>`);
}); // /edit/:post_id

app.post("/submit_comment", (req,res) => {
	const unix_timestamp = getUnixTime(new Date())
    let name = escape_input(req.body.name)
    if (name == "") {
        name = config.default_username
    }
    new_comment = {
        "name": name,
        "content": escape_input(req.body.content),
        "id": comments.counter,
        "pubdate": unix_timestamp
    };
    let counter = comments.counter+1;
    comments.comments[req.body.post_index].push(new_comment);
	fs.writeFileSync(`${__dirname}/comments.js`, `export const comments = ${JSON.stringify(comments.comments)}\nexport const counter = ${counter}`, 'utf-8');

    res.redirect(301,`/post/${req.body.post_index}`)
}); // /submit_comment
app.post("/submit_post", (req,res) => {
	const password = crypto.createHash('sha512').update(req.body.password).digest('hex');
	const username = escape_input(req.body.username)
	const title = escape_input(req.body.title)
	const content = escape_input(req.body.content)
	const tags = escape_input(req.body.tags).split(',');
	const unix_timestamp = getUnixTime(new Date())
	console.log(username, "is submitting a post titled:", title);	

	if (get_userID(username) == -1) {
		res.send("User does not exist")	
	}

	else if (users.users[get_userID(username)]['hash'] == password) { // Password matches
		posts.posts.push({
			"userID": get_userID(username),
			"title": title,
			"content": content,
			"pubdate": unix_timestamp,
			"editdate": unix_timestamp,
			"tags": tags,
		})
		fs.writeFileSync(`${__dirname}/posts.js`, `export const posts = ${JSON.stringify(posts.posts)}`, 'utf-8');
        comments.comments.push([])
        fs.writeFileSync(`${__dirname}/comments.js`, `export const comments = ${JSON.stringify(comments.comments)}\nexport const counter = ${comments.counter}`)
		res.redirect(302, "/");
	}
	else {
		res.send(`Invalid Password for user`,username);
	}
}); // /submit_post
app.post("/submit_signup", (req,res) => {
    const password =  crypto.createHash('sha512').update(req.body.password).digest('hex');
    const username = escape_input(req.body.username)
    const prettyname = escape_input(req.body.prettyname)
    const description = escape_input(req.body.description)

    // Check that signups are allowed
    if (config.allow_signup == true) {
        // get_userID will return -1 if the user does not exist
        // so this checks that the user does not exist
        if (get_userID(username) == -1) {
            users.users.push({
                "username": username,
                "prettyname": prettyname,
                "hash": password,
                "description": description,
            })
            fs.writeFileSync(`${__dirname}/users.js`, `export const users = ${JSON.stringify(users.users)}`, 'utf-8');
            res.redirect(301, `/user/${username}`)
        }
        // if the user does exist then
        else {
            res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body>${config.user_exists}</body></html>`)
        }
    }
    else if (config.allow_signup == false) {
        res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body>${config.signups_unavailable}</body></html>`)
    }
    // If allow_signup is undefined or not a boolean, error
    else {
        res.redirect(301,"/")
        console.log("Error, invalid value for allow_signup (bool)")
    }
}); // /submit_signup
app.post("/submit_delete_account", (req,res) => {
    // Get the form info
    const password = crypto.createHash("sha512").update(req.body.password).digest("hex");
    const username = escape_input(req.body.username)
    // get the userID
    const userID = get_userID(username)

    if (userID >= 0) { // The user exists
        if (password == users.users[userID]['hash']) { // password matches
            console.log(username, "(userID:", userID, ") is trying deleting their account")
            // Delete the user
            users.users.splice(userID,1)
            // Delete all their posts
            for (let postid = 0; postid < posts.posts.length; postid++) { // loop over all posts
                if (posts.posts[postid]['userID'] == userID) { // if userID matches
                    posts.posts.splice(postid,1) // delete the post
                    comments.comments.splice(postid,1) // the comments for this post should also be delete
                }
            };
            // Write these changes
            fs.writeFileSync(`${__dirname}/users.js`, `export const users = ${JSON.stringify(users.users)}`, 'utf-8');
		    fs.writeFileSync(`${__dirname}/posts.js`, `export const posts = ${JSON.stringify(posts.posts)}`, 'utf-8'); 
	        fs.writeFileSync(`${__dirname}/comments.js`, `export const comments = ${JSON.stringify(comments.comments)}\nexport const counter = ${comments.counter}`, 'utf-8');
            res.redirect(301,"/")
        }
        else { // password does not match
            res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body>${config.incorrect_password}</body></html>`)
        };
    }
    else {
        res.send(`</html><head><meta charset="${config.charset}"><style>${config.css}</style></head><body>${config.user_doesnt_exist}</body></html>`)
    }
}); // /submit_delete_account
app.post("/submit_edit", (req,res) => {
	const password = crypto.createHash('sha512').update(req.body.password).digest('hex');
	const postID = req.body.postID
	const userID = req.body.userID
	const title = req.body.title
	const content = req.body.content
	const tags = req.body.tags.split(',');
	const delete_bool = req.body.delete
	const unix_timestamp = getUnixTime(new Date())
	console.log(users.users[userID]['prettyname'], "is editting the post titled:", title);	

	if (users.users[userID]['hash'] == password) { // password matches
		let post = posts.posts[postID]
		post['title'] = title
		post['content'] = content
		post['tags'] = tags
		post['editdate'] = unix_timestamp
		if (typeof delete_bool != "undefined") {
			console.log("Deleting post!")
			posts.posts.splice(postID,1)
            comments.comments.splice(postID,1)
		    fs.writeFileSync(`${__dirname}/comments.js`, `export const comments = ${JSON.stringify(comments.comments)}\nexport const counter = ${comments.counter}`, 'utf-8');
		}
		fs.writeFileSync(`${__dirname}/posts.js`, `export const posts = ${JSON.stringify(posts.posts)}`, 'utf-8');
		res.redirect(302, "/");
	}
	else {
		res.send(`Invalid Password for user`,users.users[userID]['prettyname']);
	}
}); // /submit_edit

app.listen(config.port, () => {
	console.log(`Server is running at http://localhost:${config.port} in ${config.root_path}`);
});