package main

import (
    "fmt"
    "io"
    "log"
    "net/http"
    "os"
    "strings"
)

const (
    // MethodPurge declaration for Varnish.
    MethodPurge = "PURGE"
)

var (
    varnishList = MakeVarnishList()
    status = "200 Purged"
)

// MakeVarnishList reads the list of varnish servers from a file on disk.
func MakeVarnishList() []string {
    Data, err := os.ReadFile("./varnish")
    if err != nil {
        log.Fatal(err)
    }
    sliceData := strings.Split(string(Data), ",")
    return sliceData
}

// PurgeHandler handles PURGE request to broadcast it to all varnish instances.
func PurgeHandler(w http.ResponseWriter, r *http.Request) {
    url := r.URL.String()
    status := SendToVarnish(url)
    if status != "200 Purged" {
        w.WriteHeader(405)
    }
    io.WriteString(w, status)
}

// SendToVarnish send to all varnish servers define in varnishList the PURGE request.
func SendToVarnish(url string) string {
    status = "200 Purged"
    // Take url to ban as argument.
    // Loop over the list of Varnish servers and send PURGE request to each.
    for i := 0; i < len(varnishList); i++ {
        //status = "200 Purged"
        client := &http.Client{}
        domain := strings.Trim(varnishList[i], "\r\n")
        req, err := http.NewRequest(MethodPurge, domain + url, nil)
        if err != nil {
            log.Fatal("NewRequest: %s", err)
        }
        resp, err := client.Do(req)
        if err != nil {
            log.Fatal("Client.do: %s", err)
        }
        //fmt.Printf("Resp: %v\n", resp)
        if resp.StatusCode != 200 {
            status = "405 Not Allowed"
        }
        fmt.Println("Purge URL" + " " + domain + url + " : " + status)
    }
    return status
}

// HealthHandler handles healthcheck requests and return 200.
func HealthHandler(w http.ResponseWriter, r *http.Request) {
    io.WriteString(w, "OK")
}

func main() {
    http.HandleFunc("/", PurgeHandler)
    http.HandleFunc("/healthcheck", HealthHandler)
    log.Fatal(http.ListenAndServe(":6081",nil))
}