domino.go

package main

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

func main() {
    http.HandleFunc("/", dominoHandler)
    log.Fatal(http.ListenAndServe(":8080", nil))
}

func dominoHandler(w http.ResponseWriter, r *http.Request) {
    query := r.URL.Query()
    log.Printf("Received request: %v\n", query)
    a := query["a"]
    if a == nil || len(a[0]) == 0 {
        log.Println("No a=... in query, returning random word")
        fmt.Fprintf(w, "pseudorandom")
        return
    }
    addrs := strings.Split(a[0], ",")
    next_hop := fmt.Sprintf("http://192.168.21.%s:9001/?a=%s", addrs[0], strings.Join(addrs[1:], ","))
    resp, err := http.Get(next_hop)
    if err != nil {
        log.Printf("Error retrieving %s: %v", next_hop, err)
        w.WriteHeader(http.StatusInternalServerError)
        fmt.Fprintf(w, "Error retrieving %s\n", next_hop)
        return
    }
    defer resp.Body.Close()
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        log.Printf("Error reading response body: %v", err)
        w.WriteHeader(http.StatusInternalServerError)
        fmt.Fprintf(w, "Failed to read response body from %s", next_hop)
        return
    }
    if len(body) == 0 {
        fmt.Fprintf(w, "random")
    } else {
        fmt.Fprintf(w, "%s,random", body)
    }
}