qv/cmd/web/handlers.go

package main

import (
	api "code.dlmw.ch/dlmw/qv/internal"
	"code.dlmw.ch/dlmw/qv/internal/validator"
	"encoding/json"
	"fmt"
	"math/rand"
	"net/http"
	"time"
)

type createElectionRequestWithValidator struct {
	api.CreateElectionRequest
	validator.Validator
}

func (app *application) createElection(w http.ResponseWriter, r *http.Request) {
	var request createElectionRequestWithValidator

	if err := app.unmarshalRequest(r, &request); err != nil {
		app.clientError(w, http.StatusBadRequest, err.Error())
		return
	}

	if !isRequestValid(&request) {
		app.unprocessableEntityError(w, request.Validator)
		return
	}

	electionId, err := app.elections.Insert(
		request.Name,
		request.Tokens,
		request.AreVotersKnown,
		request.MaxVoters,
		request.Choices,
		request.ExpiresAt,
	)
	if err != nil {
		app.serverError(w, r, err)
		return
	}

	var res []byte
	if request.AreVotersKnown {
		voterIdentities := make([]string, 0, request.MaxVoters)
		for i := 0; i < request.MaxVoters; i++ {
			randomIdentity := randomVoterIdentity()
			_, err := app.voters.Insert(randomIdentity, electionId)
			if err != nil {
				app.serverError(w, r, err)
			}
			voterIdentities = append(voterIdentities, randomIdentity)
		}

		res, err = json.Marshal(api.CreateElectionResponse{VoterIdentities: &voterIdentities})
		if err != nil {
			app.serverError(w, r, err)
			return
		}
	}

	w.Header().Set("Location", fmt.Sprintf("/election/%v", electionId))
	w.Write(res)
}

func isRequestValid(r *createElectionRequestWithValidator) bool {
	r.CheckField(validator.NotBlank(r.Name), "name", "must not be blank")
	r.CheckField(validator.GreaterThan(r.Tokens, 0), "tokens", "must be greater than 0")
	r.CheckField(validator.After(r.ExpiresAt, time.Now()), "expiresAt", "must expire in a future date")
	r.CheckField(validator.GreaterThan(len(r.Choices), 1), "choices", "there must be more than 1 choice")

	if r.AreVotersKnown {
		r.CheckField(
			validator.GreaterThan(r.MaxVoters, 0),
			"maxVoters",
			"must be greater than 0 when voters are known",
		)
	} else {
		r.CheckField(
			validator.GreaterThanOrEquals(r.MaxVoters, 0),
			"maxVoters",
			"must be a positive number",
		)
	}

	return r.Valid()
}

func randomVoterIdentity() string {
	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	b := make([]byte, 16)
	for i := range b {
		b[i] = charset[rand.Intn(len(charset))]
	}
	return string(b)
}