Hugo に Google Form ベースの問い合わせを作った話

package p

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

var googleFormURL = os.Getenv("GOOGLE_FORM_URL")
var successURL = os.Getenv("SUCCESS_URL")
var failURL = os.Getenv("FAIL_URL")

type inquiry struct {
    name     string
    email    string
    message  string
}

func (i *inquiry) sendToGoogleForm() (*http.Response, error) {
    // Set up body parameters. Google Form does not accept POST with JSON.
    f := url.Values{}
    f.Add("entry.XXXXXXXX", i.name)
    f.Add("entry.XXXXXXXX", i.email)
    f.Add("entry.XXXXXXXX", i.message)

    req, err := http.NewRequest("POST", googleFormURL, strings.NewReader(f.Encode()))
    if err != nil {
        return nil, err
    }

    req.Header.Add("Content-Type", "application/x-www-form-urlencoded")

    // Send the request and get a response from Slack API.
    httpClient := &http.Client{}
    return httpClient.Do(req)
}

func newInquiry(r *http.Request) (*inquiry, error) {
    // Return error when the request method is not POST.
    if r.Method != http.MethodPost {
        return nil, errors.New("Invalid Request Method")
    }

    // Return error when the media type is invalid.
    if r.Header.Get("Content-Type") != "application/x-www-form-urlencoded" {
        return nil, errors.New("Invalid Content Type")
    }

    return &inquiry{
        name:     r.FormValue("name"),
        email:    r.FormValue("email"),
        message:  r.FormValue("message"),
    }, nil
}

// ContactForm is a function to send a request to Google Form and redirect based on the response.
func ContactForm(w http.ResponseWriter, r *http.Request) {
    // Extract parameters from the request.
    inq, err := newInquiry(r)
    if err != nil {
        log.Print("Failed to parse the request from web", err)
        http.Redirect(w, r, failURL, http.StatusFound)
        return
    }

    // Send the request and get a response from Google Form.
    res, err := inq.sendToGoogleForm()
    defer res.Body.Close()

    // Redirect to error page when failed.
    if err != nil {
        log.Print("Could not send a request to Google Form: ", err)
        http.Redirect(w, r, failURL, http.StatusFound)
        return
    }

    if res.StatusCode != 200 {
        b, _ := ioutil.ReadAll(res.Body)
        log.Print("Bad request to Google Form: ", string(b))
        http.Redirect(w, r, failURL, http.StatusFound)
        return
    }

    // Redirect to a page that tells it is done.
    http.Redirect(w, r, successURL, http.StatusFound)
}