package main

import (
    "container/ring"
    "fmt"
    "github.com/hpcloud/tail"
    "encoding/json"
    "net/http"
    "os"
    "regexp"
    "strconv"
    "strings"
    "time"
)

func fileHandler(w http.ResponseWriter, r *http.Request, s string) {
    fn := r.URL.Path[5:len(r.URL.Path)]

    for _, v := range whitelist {
        if !strings.Contains(v, fn) {
            sendFile(w, fn, "", "Permission denied")
        return
        }
    }

    if _, err := os.Stat(fn); err != nil {
       sendFile(w, fn, "", "No such file or directory")
       return
    }

    if (watch == false) {
        t, err := tail.TailFile(fn, tail.Config{Follow: false})
    watch = true
    }

    if (err == nil) {
       fmt.Println(err)
    }

    var m = ""

    w.WriteHeader(http.StatusOK)
    for line := range t.Lines {
        m += fmt.Sprintf("%s\n", line.Text)
        logring.Value = line.Text
        logring = logring.Next()
    }
    if m != m_prev {
        sendFile(w, fn, m, "")
        m_prev = m
    }
}

func sendFile(w http.ResponseWriter, fn string, m string, err string) {
    json.NewEncoder(w).Encode(map[string]string{"time": strconv.FormatInt(t_ms(), 16), "Filename": fn, "Text": m, "error": err})
}

func t_ms() (int64) {
    now := time.Now()
    ns := now.UnixNano()
    ms := ns / 1000000
    return ms
}

func makeHandler(fn func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        m := validPath.FindStringSubmatch(r.URL.Path)
        if m == nil {
            http.NotFound(w, r)
            return
        }
        fmt.Println("makeHandler::request::" + r.RequestURI)
        fn(w, r, m[2])
    }
}

var prj = "httptail"
var version = "0.1.0"
var server_inet6 = "[fdef:c181:4234:7978:6::1]:8080"
var whitelist = map[int]string{
    0: "/var/log",
}

var logring = ring.New(1000)
var validPath = regexp.MustCompile("^/(tail*|auth)/(.*)$")
var watch bool = false
var m_prev = ""

func main() {
    uid := os.Getuid()
    t.Filename = ""

    if (uid == -1) {
        fmt.Println("Windows is unsupported")
        }

    if (uid == 0) {
            fmt.Println("Refusing to run as root")
        return
    }

    http.HandleFunc("/tail/", makeHandler(fileHandler))

        fmt.Println("Serving " + prj + " " + version + " on " + server_inet6)
        http.ListenAndServe(server_inet6, nil)
    t.Cleanup()
}