// https://developer.fastly.com/solutions/examples/manipulate-query-string

package main

import (
	"context"
	"fmt"
	"io"

	"github.com/fastly/compute-sdk-go/fsthttp"
)

// BackendName is the name of our service backend.
const BackendName = "origin_0"

func main() {
	fsthttp.ServeFunc(func(ctx context.Context, w fsthttp.ResponseWriter, r *fsthttp.Request) {
		// This requires your service to be configured with a backend
		// named "origin_0" and pointing to "https://http-me.glitch.me".
    
    // Use Query() method to store query string parameters as an url.Values map.
    values := r.URL.Query()
    // Add query string parameter.
    values.Add("ccc", "new")
    // Remove any Google Analytics campaign parameters.
    values.Del("utm_campaign")
    values.Del("utm_source")
    // Use Encode() method to transform url.Values map into a URL-encoded string.
    // This sorts the query string parameters in alphabetical order by default. 
    r.URL.RawQuery = values.Encode()
   
		resp, err := r.Send(ctx, BackendName)
		if err != nil {
			w.WriteHeader(fsthttp.StatusBadGateway)
			fmt.Fprintln(w, err.Error())
			return
		}

		w.Header().Reset(resp.Header)
		w.WriteHeader(resp.StatusCode)
		io.Copy(w, resp.Body)
	})
}