package main

import (

"encoding/json"

"errors"

"flag"

"fmt"

"io/ioutil"

"log"

"net/http"

"net/url"

"os"

"code.google.com/p/google-api-go-client/googleapi/transport"

"code.google.com/p/google-api-go-client/youtube/v3"

)

var (

query = flag.String("query", "Google", "Freebase search term")

maxResults = flag.Int64("max-results", 25, "Max YouTube results")

resultType = flag.String("type", "channel", "YouTube result type: video, playlist, or channel")

)

const developerKey = "YOUR DEVELOPER KEY HERE"

const freebaseSearchURL = "https://www.googleapis.com/freebase/v1/search?%s"

// Notable is struct for unmarshalling JSON values from the API.

type Notable struct {

Name string

ID string

}

// FreebaseTopic is struct for unmarshalling JSON values from the API.

type FreebaseTopic struct {

Mid string

ID string

Name string

Notable Notable

Lang string

Score float64

}

// FreebaseResponse is struct for unmarshalling JSON values from the Freebase API.

type FreebaseResponse struct {

Status string

Result []FreebaseTopic

}

func main() {

flag.Parse()

topicID, err := getTopicID(*query)

if err != nil {

log.Fatalf("Cannot fetch topic ID from Freebase: %v", err)

}

err = youtubeSearch(topicID)

if err != nil {

log.Fatalf("Cannot make YouTube API call: %v", err)

}

}

// getTopicID queries Freebase with the given string. It then prompts the user

// to select a topic, then returns the selected topic so that the topic can be

// used to search YouTube for videos, channels or playlists.

func getTopicID(topic string) (string, error) {

urlParams := url.Values{

"query": []string{topic},

"key": []string{developerKey},

}

apiURL := fmt.Sprintf(freebaseSearchURL, urlParams.Encode())

resp, err := http.Get(apiURL)

if err != nil {

return "", err

} else if resp.StatusCode != http.StatusOK {

errorMsg := fmt.Sprintf("Received HTTP status code %v using developer key: %v",

resp.StatusCode, developerKey)

return "", errors.New(errorMsg)

}

body, err := ioutil.ReadAll(resp.Body)

if err != nil {

return "", err

}

var data FreebaseResponse

err = json.Unmarshal(body, &data)

if err != nil {

return "", nil

}

if len(data.Result) == 0 {

return "", errors.New("No matching terms were found in Freebase.")

}

// Print a list of topics for the user to select.

fmt.Println("The following topics were found:")

for index, topic := range data.Result {

if topic.Notable.Name == "" {

topic.Notable.Name = "Unknown"

}

fmt.Printf(" %2d. %s (%s)\r\n", index+1, topic.Name, topic.Notable.Name)

}

prompt := fmt.Sprintf("Enter a topic number to find related YouTube %s [1-%v]: ",

*resultType, len(data.Result))

selection, err := readInt(prompt, 1, len(data.Result))

if err != nil {

return "", nil

}

choice := data.Result[selection-1]

return choice.Mid, nil

}

// readInt reads an integer from standard input and verifies that the value

// is between the allowed min and max values (inclusive).

func readInt(prompt string, min int, max int) (int, error) {

// Loop until we have a valid input.

for {

fmt.Print(prompt)

var i int

_, err := fmt.Fscan(os.Stdin, &i)

if err != nil {

return 0, err

}

if i < min || i > max {

fmt.Println("Invalid input.")

continue

}

return i, nil

}

}

// youtubeSearch searches YouTube for the topic given in the query flag and

// prints the results. This function takes a mid parameter, which specifies

// a value retrieved using the Freebase API.

func youtubeSearch(mid string) error {

client := &http.Client{

Transport: &transport.APIKey{Key: developerKey},

}

service, err := youtube.New(client)

if err != nil {

return err

}

// Make the API call to YouTube.

call := service.Search.List("id,snippet").

TopicId(mid).

Type(*resultType).

MaxResults(*maxResults)

response, err := call.Do()

if err != nil {

return err

}

// Iterate through each item and output it.

for _, item := range response.Items {

itemID := ""

switch item.Id.Kind {

case "youtube#video":

itemID = item.Id.VideoId

case "youtube#channel":

itemID = item.Id.ChannelId

case "youtube#playlist":

itemID = item.Id.PlaylistId

}

fmt.Printf("%v (%v)\r\n", item.Snippet.Title, itemID)

}

return nil

}