/*
    MastoGem, A Mastodon proxy for Gemini
    Copyright (C) 2021 Romain de Laage

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
package main

import (
	"crypto/tls"
	"net/url"
	"log"
	"net"
	"bufio"
	"strconv"
	"fmt"
	"strings"
)

func listen(address, certFile, keyFile string) net.Listener {
	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
		log.Fatalln("loadkeys: %s", err)
	}
	config := &tls.Config{
		ClientAuth:   tls.RequestClientCert,
		Certificates: []tls.Certificate{cert},
		MinVersion:   tls.VersionTLS12,
		InsecureSkipVerify: true,
	}

	listener, err := tls.Listen("tcp", address, config)
	if err != nil {
		log.Fatalln("failed to listen on 0.0.0.0:1965: %s", err)
	}

	return listener
}

func serve(listener net.Listener, baseURL, title, home_message string) {
	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Println(err)
		}

		go handleConn(conn.(*tls.Conn), baseURL, title, home_message)
	}
}

func getRawURL(conn *tls.Conn) (string, error) {
	scanner := bufio.NewScanner(conn)
	if ok := scanner.Scan(); !ok {
		return "", scanner.Err()
	}

	rawURL := scanner.Text()
	if strings.Contains(rawURL, "://") {
		return rawURL, nil
	}

	return fmt.Sprintf("gemini://%s", rawURL), nil
}

func getPath(conn *tls.Conn) (string, error) {
	rawURL, err := getRawURL(conn)
	if err != nil {
		return "", err
	}

	parsedURL, err := url.Parse(rawURL)
	if err != nil {
		return "", err
	}

	return parsedURL.Path, nil
}

func handleConn(conn *tls.Conn, baseURL, title, home_message string) {
	defer conn.Close()

	path, err := getPath(conn)
	if err != nil {
		log.Println("get url: %s", err)
		_, err = fmt.Fprintf(conn, "59 Can't parse request\r\n")
		if err != nil {
			log.Println("send error: %s", err)
			return
		}
		return
	}

	// home
	if path == "" || path == "/" {
		_, err = fmt.Fprintf(conn, "20 text/gemini\r\n# " + title + "\n\n" + home_message)
		if err != nil {
			log.Println("send error: %s", err)
			return
		}
		return
	}

	// profile
	if strings.HasPrefix(path, "/profile/") {
		// skip prefix
		path = path[9:]
		_, err = strconv.ParseUint(path, 10, 64)
		if err != nil {
			log.Println("invalid request: %s", err)
			_, err = fmt.Fprintf(conn, "59 Can't parse request\r\n")
			if err != nil {
				log.Println("send error: %s", err)
				return
			}
			return
		}

		log.Println("Received request for account " + path)

		printProfile(conn, baseURL, path)
	} /* thread */ else if strings.HasPrefix(path, "/thread/") {
		// skip prefix
		path = path[8:]

		_, err = strconv.ParseUint(path, 10, 64)
		if err != nil {
			log.Println("invalid request: %s", err)
			_, err = fmt.Fprintf(conn, "59 Can't parse request\r\n")
			if err != nil {
				log.Println("send error: %s", err)
				return
			}
			return
		}

		log.Println("Received request for thread " + path)

		printThread(conn, baseURL, path)
	} else {
		_, err = fmt.Fprintf(conn, "59 Invalid request\r\n")
		if err != nil {
			log.Println("send: %s", err)
			return
		}
	}
}

func printProfile(conn *tls.Conn, baseURL, profileID string) {
	account, err := getAccount(baseURL, profileID)
	blogs := getBlog(baseURL, profileID)

	if err != nil || blogs == nil {
		_, err = fmt.Fprintf(conn, "40 Remote mastodon instance failed\r\n")
		if err != nil {
			log.Println("handleConn: %s", err)
			return
		}
		return
	}

	_, err = fmt.Fprintf(conn, "20 text/gemini\r\n# Toots for " + account.Name + " account\n")
	if err != nil {
		log.Println("handleConn: %s", err)
		return
	}

	for _, blog := range blogs {
		date := "\n```\n* Posted at " + blog.Date + " *\n```\n"

		text := removeHTMLTags(blog.Content) + "\n"

		_, err = fmt.Fprintf(conn, date + text + "=> /thread/" + blog.Id + " View the thread\n")
		if err != nil {
			log.Println("read blogs: %s", err)
			return
		}
	}

	_, err = fmt.Fprintf(conn, "=> " + account.Url + " Go to " + account.Name + " account")
	if err != nil {
		log.Println("add link: %s", err)
		return
	}
}

func printThread(conn *tls.Conn, baseURL, tootID string) {
	originalToot, err := getToot(baseURL, tootID)
	if err != nil {
		_, err = fmt.Fprintf(conn, "40 Remote mastodon instance failed\r\n")
		if err != nil {
			log.Println("handleConn: %s", err)
			return
		}
		return
	}

	thread, err := getThread(baseURL, tootID)
	if err != nil {
		_, err = fmt.Fprintf(conn, "40 Remote mastodon instance failed\r\n")
		if err != nil {
			log.Println("handleConn: %s", err)
			return
		}
		return
	}

	// Print header
	_, err = fmt.Fprintf(conn, "20 text/gemini\r\n# Ancestors\n")
	if err != nil {
		log.Println("handleConn: %s", err)
		return
	}

	// Print each anscestor
	for _, toot := range thread.Ancestors {
		_, err = fmt.Fprintf(conn, "\n```\n* Posted on " + toot.Date + " by " + toot.Author.Name + " *\n```\n" + removeHTMLTags(toot.Content) + "\n=> /profile/" + toot.Author.Id + " More toots from " + toot.Author.Name + "\n")
		if err != nil {
			log.Println("handleConn: %s", err)
			return
		}
	}

	// Print original toot
	_, err = fmt.Fprintf(conn, "\n# Toot\n\n```\n* Posted on " + originalToot.Date + " by "+ originalToot.Author.Name +" *\n```\n" + removeHTMLTags(originalToot.Content) + "\n=> /profile/" + originalToot.Author.Id + " More toots from " + originalToot.Author.Name + "\n")
	if err != nil {
		log.Println("handleConn: %s", err)
		return
	}

	// Print each descendant
	_, err = fmt.Fprintf(conn, "\n# Descendants\n")
	if err != nil {
		log.Println("handleConn: %s", err)
		return
	}
	for _, toot := range thread.Descendants {
		_, err = fmt.Fprintf(conn, "\n```\n* Posted on " + toot.Date + " by " + toot.Author.Name + " *\n```\n" + removeHTMLTags(toot.Content) + "\n=> /profile/" + toot.Author.Id + " More toots from " + toot.Author.Name + "\n")
		if err != nil {
			log.Println("handleConn: %s", err)
			return
		}
	}
}