github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/talks/2013/highperf/mart/1/mart.go (about)

     1  // +build OMIT
     2  
     3  package mart
     4  
     5  import (
     6  	"bytes"
     7  	"fmt"
     8  	"math/rand"
     9  	"net/http"
    10  	"strconv"
    11  	"strings"
    12  
    13  	"appengine"
    14  	"appengine/datastore"
    15  	"appengine/mail"
    16  	"appengine/user"
    17  
    18  	"github.com/mjibson/appstats"
    19  )
    20  
    21  func init() {
    22  	http.HandleFunc("/", front)
    23  	http.Handle("/checkout", appstats.NewHandler(checkout))
    24  	http.HandleFunc("/admin/populate", adminPopulate)
    25  }
    26  
    27  func front(w http.ResponseWriter, r *http.Request) {
    28  	if r.URL.Path != "/" {
    29  		http.NotFound(w, r)
    30  		return
    31  	}
    32  	fmt.Fprintf(w, "Hello, welcome to Gopher Mart!")
    33  }
    34  
    35  const (
    36  	numItems = 100 // number of different items for sale
    37  
    38  	appAdmin = "noreply@google.com" // an admin of this app, for sending mail
    39  )
    40  
    41  // Item represents an item for sale in Gopher Mart.
    42  type Item struct {
    43  	Name  string
    44  	Price float64
    45  }
    46  
    47  func itemKey(c appengine.Context, i int) *datastore.Key {
    48  	return datastore.NewKey(c, "Item", fmt.Sprintf("item%04d", i), 0, nil)
    49  }
    50  
    51  func checkout(c appengine.Context, w http.ResponseWriter, r *http.Request) {
    52  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
    53  	num, err := strconv.Atoi(r.FormValue("num"))
    54  	if err == nil && (num < 1 || num > 30) {
    55  		err = fmt.Errorf("%d out of range [1,30]", num)
    56  	}
    57  	if err != nil {
    58  		http.Error(w, fmt.Sprintf("bad number of items: %v", err), http.StatusBadRequest)
    59  		return
    60  	}
    61  
    62  	// Pick random items.
    63  	keys := make([]*datastore.Key, num)
    64  	for i := range keys {
    65  		keys[i] = itemKey(c, rand.Intn(numItems))
    66  	}
    67  
    68  	// Dumb load.
    69  	var items []*Item
    70  	for _, key := range keys {
    71  		item := new(Item)
    72  		if err := datastore.Get(c, key, item); err != nil {
    73  			http.Error(w, fmt.Sprintf("datastore.Get: %v", err), http.StatusBadRequest)
    74  			return
    75  		}
    76  		items = append(items, item)
    77  	}
    78  
    79  	// Print items.
    80  	var b bytes.Buffer
    81  	fmt.Fprintf(&b, "Here's what you bought:\n")
    82  	var sum float64
    83  	for _, item := range items {
    84  		fmt.Fprintf(&b, "\t%s", item.Name)
    85  		fmt.Fprint(&b, strings.Repeat("\t", (40-len(item.Name)+7)/8))
    86  		fmt.Fprintf(&b, "$%5.2f\n", item.Price)
    87  		sum += item.Price
    88  	}
    89  	fmt.Fprintln(&b, strings.Repeat("-", 55))
    90  	fmt.Fprintf(&b, "\tTotal:\t\t\t\t\t$%.2f\n", sum)
    91  
    92  	w.Write(b.Bytes())
    93  
    94  	sendReceipt(c, user.Current(c).Email, b.String())
    95  }
    96  
    97  func sendReceipt(c appengine.Context, dst, body string) {
    98  	msg := &mail.Message{
    99  		Sender:  appAdmin,
   100  		To:      []string{dst},
   101  		Subject: "Your Gopher Mart receipt",
   102  		Body:    body,
   103  	}
   104  	if err := mail.Send(c, msg); err != nil {
   105  		c.Errorf("mail.Send: %v", err)
   106  	}
   107  }
   108  
   109  func adminPopulate(w http.ResponseWriter, r *http.Request) {
   110  	c := appengine.NewContext(r)
   111  	for i := range [numItems]struct{}{} { // r hates this. tee hee.
   112  		key := itemKey(c, i)
   113  		good := goods[rand.Intn(len(goods))]
   114  		item := &Item{
   115  			// TODO: vary names more
   116  			Name:  fmt.Sprintf("%s %dg", good.name, i+1),
   117  			Price: float64(rand.Intn(1999)+1) / 100,
   118  		}
   119  		if _, err := datastore.Put(c, key, item); err != nil {
   120  			http.Error(w, err.Error(), 500)
   121  			return
   122  		}
   123  	}
   124  	fmt.Fprintf(w, "ok. %d items populated.", numItems)
   125  }
   126  
   127  var goods = [...]struct {
   128  	name string
   129  }{
   130  	{"Gopher Bran"},
   131  	{"Gopher Flakes"},
   132  	{"Gopher Grease"},
   133  	{"Gopher Litter"},
   134  }