// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"bufio"
	"expvar"
	"flag"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"strconv"
)


// hello world, the web server
var helloRequests = expvar.NewInt("hello-requests")

func HelloServer(c *http.Conn, req *http.Request) {
	helloRequests.Add(1)
	io.WriteString(c, "hello, world!\n")
}

// Simple counter server. POSTing to it will set the value.
type Counter struct {
	n int
}

// This makes Counter satisfy the expvar.Var interface, so we can export
// it directly.
func (ctr *Counter) String() string { return fmt.Sprintf("%d", ctr.n) }

func (ctr *Counter) ServeHTTP(c *http.Conn, req *http.Request) {
	switch req.Method {
	case "GET":
		ctr.n++
	case "POST":
		buf := new(bytes.Buffer)
		io.Copy(buf, req.Body)
		body := buf.String()
		if n, err := strconv.Atoi(body); err != nil {
			fmt.Fprintf(c, "bad POST: %v\nbody: [%v]\n", err, body)
		} else {
			ctr.n = n
			fmt.Fprint(c, "counter reset\n")
		}
	}
	fmt.Fprintf(c, "counter = %d\n", ctr.n)
}

// simple file server
var webroot = flag.String("root", "/home/rsc", "web root directory")
var pathVar = expvar.NewMap("file-requests")

func FileServer(c *http.Conn, req *http.Request) {
	c.SetHeader("content-type", "text/plain; charset=utf-8")
	pathVar.Add(req.URL.Path, 1)
	path := *webroot + req.URL.Path // TODO: insecure: use os.CleanName
	f, err := os.Open(path, os.O_RDONLY, 0)
	if err != nil {
		c.WriteHeader(http.StatusNotFound)
		fmt.Fprintf(c, "open %s: %v\n", path, err)
		return
	}
	n, err1 := io.Copy(c, f)
	fmt.Fprintf(c, "[%d bytes]\n", n)
	f.Close()
}

// simple flag server
var booleanflag = flag.Bool("boolean", true, "another flag for testing")

func FlagServer(c *http.Conn, req *http.Request) {
	c.SetHeader("content-type", "text/plain; charset=utf-8")
	fmt.Fprint(c, "Flags:\n")
	flag.VisitAll(func(f *flag.Flag) {
		if f.Value.String() != f.DefValue {
			fmt.Fprintf(c, "%s = %s [default = %s]\n", f.Name, f.Value.String(), f.DefValue)
		} else {
			fmt.Fprintf(c, "%s = %s\n", f.Name, f.Value.String())
		}
	})
}

// simple argument server
func ArgServer(c *http.Conn, req *http.Request) {
	for i, s := range os.Args {
		fmt.Fprint(c, s, " ")
	}
}

// a channel (just for the fun of it)
type Chan chan int

func ChanCreate() Chan {
	c := make(Chan)
	go func(c Chan) {
		for x := 0; ; x++ {
			c <- x
		}
	}(c)
	return c
}

func (ch Chan) ServeHTTP(c *http.Conn, req *http.Request) {
	io.WriteString(c, fmt.Sprintf("channel send #%d\n", <-ch))
}

// exec a program, redirecting output
func DateServer(c *http.Conn, req *http.Request) {
	c.SetHeader("content-type", "text/plain; charset=utf-8")
	r, w, err := os.Pipe()
	if err != nil {
		fmt.Fprintf(c, "pipe: %s\n", err)
		return
	}
	pid, err := os.ForkExec("/bin/date", []string{"date"}, os.Environ(), "", []*os.File{nil, w, w})
	defer r.Close()
	w.Close()
	if err != nil {
		fmt.Fprintf(c, "fork/exec: %s\n", err)
		return
	}
	io.Copy(c, r)
	wait, err := os.Wait(pid, 0)
	if err != nil {
		fmt.Fprintf(c, "wait: %s\n", err)
		return
	}
	if !wait.Exited() || wait.ExitStatus() != 0 {
		fmt.Fprintf(c, "date: %v\n", wait)
		return
	}
}

func main() {
	flag.Parse()

	// The counter is published as a variable directly.
	ctr := new(Counter)
	http.Handle("/counter", ctr)
	expvar.Publish("counter", ctr)

	http.Handle("/go/", http.HandlerFunc(FileServer))
	http.Handle("/flags", http.HandlerFunc(FlagServer))
	http.Handle("/args", http.HandlerFunc(ArgServer))
	http.Handle("/go/hello", http.HandlerFunc(HelloServer))
	http.Handle("/chan", ChanCreate())
	http.Handle("/date", http.HandlerFunc(DateServer))
	err := http.ListenAndServe(":12345", nil)
	if err != nil {
		log.Crash("ListenAndServe: ", err)
	}
}