audioaxis/main.go

package main

import (
	"fmt"
	"http"
	"exp/template"
	"os"
	"json"
	"strconv"
	"time"
)

type Song struct {
	Yid string
	Title string
	User string
}
type Playlist struct {
	Id string
}

var templates map[string]*template.Template
const debug = true

func home(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Welcome to Audio Axis!")
}

func playlist(w http.ResponseWriter, r *http.Request) {
	id := r.URL.Path[len("/p/"):]
	if len(id) != 8 {
		http.Redirect(w, r, "/", 303)
		return
	}
	playlist := Playlist{Id: id}

	if debug {
		t, err := template.ParseFile("templates/p.html")
		if err != nil {
			http.Error(w, err.String(), http.StatusInternalServerError)
			return
		}
		err = t.Execute(w, playlist)
		if err != nil {
			w.Write([]byte(err.String()))
			fmt.Fprintln(os.Stderr, err.String())
			return
		}
	} else {
		err := templates["p"].Execute(w, playlist)
		if err != nil {
			fmt.Fprintln(os.Stderr, err.String())
		}
	}
}

func add(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()
	db := <-dbPool
	defer func () {dbPool <- db}()

	pid := getpid(db, q.Get("pid"))
	if pid == -1 {
		http.Error(w, "invalid pid", http.StatusBadRequest)
		return
	}

	err := db.Start()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}
	// unfortunately, MAX(`order`) returns NULL when there is nothing
	// so query for COUNT(`sid`)
	count, err := queryInt(db, "SELECT COUNT(`sid`) FROM `song` WHERE `pid` = ?", pid)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}
	_, err = prepare(db,
			"INSERT INTO `song` (`pid`,`yid`,`title`,`user`,`order`) VALUES(?, ?, ?, ?, ?)",
			pid, q.Get("yid"), q.Get("title"), q.Get("user"), count)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}
	err = db.Commit()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	w.Write([]byte("1"))
	addUpdate(pid, addAction,
			&Song{Yid: q.Get("yid"), Title: q.Get("title"), User: q.Get("user")})
}

func remove(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()

	db := <-dbPool
	defer func () {dbPool <- db}()

	pid := getpid(db, q.Get("pid"))
	if pid == -1 {
		http.Error(w, "invalid pid", http.StatusBadRequest)
		return
	}

	err := db.Start()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	order, err := queryInt(db, "SELECT `order` FROM `song` WHERE `yid` = ? AND `pid` = ?",
			q.Get("yid"), pid)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	_, err = prepare(db, "DELETE FROM `song` WHERE `pid` = ? AND yid = ?",
			pid, q.Get("yid"))
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	_, err = prepare(db, "UPDATE `song` SET `order` = `order`-1 WHERE `order` > ? AND `pid` = ?",
			order, pid)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	err = db.Commit()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	w.Write([]byte("1"))
	addUpdate(pid, removeAction, &Song{Yid: q.Get("yid")})
}

func move(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()

	db := <-dbPool
	defer func () {dbPool <- db}()

	pid := getpid(db, q.Get("pid"))
	if pid == -1 {
		http.Error(w, "invalid pid", http.StatusBadRequest)
		return
	}

	direction, err := strconv.Atoui(q.Get("direction"))
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	err = db.Start()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	order, err := queryInt(db, "SELECT `order` FROM `song` WHERE `yid` = ? AND `pid` = ?",
			q.Get("yid"), pid)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}
	newOrder := order
	if direction == moveUpAction && order > 0 {
		newOrder--
	} else if direction == moveDownAction {
		newOrder++
	} else {
		db.Rollback()
		http.Error(w, "invalid direction or cannot move up", http.StatusBadRequest)
		return
	}

	query, err := prepare(db, "UPDATE `song` SET `order` = ? WHERE `order` = ? AND `pid` = ?",
			order, newOrder, pid)
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	} else if query.AffectedRows != 1 {
		db.Rollback()
		http.Error(w, "invalid direction for this song", http.StatusBadRequest)
		return
	}
	// there are now two songs with that order, so also check yid
	_, err = prepare(db, "UPDATE `song` SET `order` = ? WHERE `order` = ? AND `pid` = ? AND `yid` = ?",
			newOrder, order, pid, q.Get("yid"))
	if err != nil {
		db.Rollback()
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	err = db.Commit()
	if err != nil {
		http.Error(w, err.String(), http.StatusInternalServerError)
		return
	}

	w.Write([]byte("1"))
	addUpdate(pid, direction, &Song{Yid: q.Get("yid")})
}

func poll(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()
	timestamp := q.Get("timestamp")
	if timestamp == "-1" {
		db := <-dbPool
		defer func () {dbPool <- db}()

		query, err := prepare(db,
				"SELECT `yid`,`title`,`user` FROM `playlist` JOIN `song` WHERE `id` = ? ORDER BY `order` ASC",
				q.Get("pid"))

		updates := make([]Update, 0, 2)
		for {
			song := new(Song)
			query.BindResult(&song.Yid, &song.Title, &song.User)
			eof, err := query.Fetch()
			if err != nil {
				http.Error(w, err.String(), http.StatusInternalServerError)
				return
			}
			if eof {
				break
			}
			updates = append(updates, Update{Song: song, Action: addAction, Timestamp: time.Nanoseconds()})
		}
		err = query.FreeResult()
		if err != nil {
			http.Error(w, err.String(), http.StatusInternalServerError)
			return
		}

		output, err := json.MarshalForHTML(updates)
		if err != nil {
			http.Error(w, err.String(), http.StatusInternalServerError)
			return
		}
		w.Write(output)
	} else {
		timestamp, err := strconv.Atoi64(q.Get("timestamp"))
		if err != nil {
			http.Error(w, err.String(), http.StatusInternalServerError)
			return
		}
		update := getUpdates(q.Get("pid"), timestamp)
		if update != nil {
			w.Write([]byte("["))
			for update != nil {
				output, err := json.MarshalForHTML(update)
				if err == nil {
					w.Write(output)
				}
				update = update.Next
				if update != nil {
					w.Write([]byte(","))
				}
			}
			w.Write([]byte("]"))
			return
		}
		w.Write([]byte("[]"))
	}
}

func main() {
	templates = make(map[string]*template.Template)
	for _, path := range []string{"p"} {
		t, err := template.ParseFile("templates/" + path + ".html")
		if err != nil {
			fmt.Println(err)
			return
		}
		templates[path] = t
	}

	initDb()

	http.HandleFunc("/", home)
	http.HandleFunc("/p/", playlist)
	http.HandleFunc("/add/", add)
	http.HandleFunc("/remove/", remove)
	http.HandleFunc("/move/", move)
	http.HandleFunc("/poll/", poll)
	err := http.ListenAndServe("localhost:8000", nil)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}