Login light
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/

// See page 195.

// Http4 is an e-commerce server that registers the /list and /price
// endpoint by calling http.HandleFunc.
package main

import (
    "fmt"
    "log"
    "net/http"
)

//!+main

func main() {
    db := database{"shoes": 50, "socks": 5}
    http.HandleFunc("/list", db.list)
    http.HandleFunc("/price", db.price)
    log.Fatal(http.ListenAndServe("localhost:8000", nil))
}

//!-main

type dollars float32

func (d dollars) String() string { return fmt.Sprintf("$%.2f", d) }

type database map[string]dollars

func (db database) list(w http.ResponseWriter, req *http.Request) {
    for item, price := range db {
        fmt.Fprintf(w, "%s: %s\n", item, price)
    }
}

func (db database) price(w http.ResponseWriter, req *http.Request) {
    item := req.URL.Query().Get("item")
    if price, ok := db[item]; ok {
        fmt.Fprintf(w, "%s\n", price)
    } else {
        w.WriteHeader(http.StatusNotFound) // 404
        fmt.Fprintf(w, "no such item: %q\n", item)
    }
}