// A barebones gopher server written in Golang
// This fork in particular uses flags instead of environment variables.
// Copyright:
// (C) 2021 Shokara Kou
// (C) 2023 Izuru Yakumo

package main

import (
	"bufio"
	"io"
	"log"
	"net"
	"os"
	"strings"
	"flag"
)

var (
	ADDR_IP string
	ADDR_PORT string
	HOSTNAME string
	SRVDIR string
)

func formatLine(line string) string {
	trimmed := strings.TrimRight(line, "\r\n")
	splitted := strings.Split(trimmed, "\t")

	if len(splitted) == 3 {
		return line
	} else if len(splitted) == 2 {
		line += "\t" + HOSTNAME + "\t" + ADDR_PORT
	} else if len(splitted) == 1 {
		line += "\tErr\t" + HOSTNAME + "\t" + ADDR_PORT
	}

	return line + "\n"
}

func writeError(c net.Conn, msg string) {
	c.Write([]byte(formatLine("3" + msg)))
}

func printGophermap(c net.Conn, dir string) {
	file, err := os.Open(dir + "/Gophermap")
	if err != nil {
		writeError(c, err.Error())
		log.Println(err)
	}
	defer func() {
		if err = file.Close(); err != nil {
			log.Println(err)
		}
	}()

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		c.Write([]byte(formatLine(scanner.Text()) + "\n"))
	}

	c.Write([]byte(".\r\n"))
}

func printFile(c net.Conn, path string) {
	file, err := os.Open(path)
	if err != nil {
		writeError(c, err.Error())
		log.Println(err)
	}
	defer func() {
		if err = file.Close(); err != nil {
			log.Println(err)
		}
	}()

	const bufSz = 1024
	b := make([]byte, bufSz)

	for {
		readSz, err := file.Read(b)
		if err != nil {
			if err != io.EOF {
				log.Println(err)
			}
			break
		}

		c.Write(b[:readSz])
	}
}

func connHandle(c net.Conn) {
	data, err := bufio.NewReader(c).ReadString('\n')
	if err != nil {
		log.Println(err)
		return
	}

	selector := strings.TrimRight(data, "\r\n")

	if selector == "" {
		printGophermap(c, "./")
	} else if strings.Contains(selector, "..") {
		writeError(c, "Selector contains ..")
	} else if selector[0] == '/' {
		info, err := os.Stat(selector[1:])
		if err != nil {
			writeError(c, err.Error())
			log.Println(err)

			c.Close()
			return
		}

		if info.IsDir() {
			printGophermap(c, selector[1:])
		} else {
			printFile(c, selector[1:])
		}
	} else {
		writeError(c, "Selector doesn't start with a /")
	}

	c.Close()
}

func init() {
	flag.StringVar(&ADDR_IP, "i", "0.0.0.0", "IP address for Tokiko to listen on .Default is 0.0.0.0")
	flag.StringVar(&ADDR_PORT, "p", "70", "Port for Tokiko to listen on. Default is 70")
	flag.StringVar(&HOSTNAME, "h", "localhost", "Hostname that gets printed for links. Default is localhost")
	flag.StringVar(&SRVDIR, "s", ".", "Root directory that gets served. Default is current directory")
}
func main() {
	flag.Parse()
	
	LISTEN_ADDR := ADDR_IP + ":" + ADDR_PORT
	log.Printf("Starting thomomys on %s\n", LISTEN_ADDR)

	os.Chdir(SRVDIR)

	l, err := net.Listen("tcp", LISTEN_ADDR)
	if err != nil {
		log.Fatal(err)
		return
	}
	defer l.Close()
	
	for {
		c, err := l.Accept()
		if err != nil {
			log.Println(err)
			return
		}

		go connHandle(c)
	}
}