commit af869235fc37e2ad17981e04872f1d4172e4de15
Author: Chakib Benziane <chakib.benz@gmail.com>
Date:   Mon Oct 12 21:44:19 2015 +0200

    consume youtube api with golang

diff --git a/youtube.go b/youtube.go
new file mode 100644
index 0000000..e873c0d
--- /dev/null
+++ b/youtube.go
@@ -0,0 +1,229 @@
+//TODO
+// 1- Build model for basic youtube API answer
+// We need to put the data into model using JSON Unmarshal
+
+// 2- Test simple channel request based on user handle (we only need channel ID)
+
+// 3- Now we need to get the content inside Items in each Answer
+
+// 4- Get Playlists list from a channel
+
+// 5- Get Videos(PlayListItems) lists from playlist
+
+// DONE
+//
+// 6- Ignore empty results
+
+// 7- Handle Pagination (not today :))
+//
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/url"
+)
+
+// Global variables
+var (
+	YOUTUBE_API_KEY = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+
+	YOUTUBE_API_ENDPOINT = "https://www.googleapis.com/youtube/v3/"
+
+	TEST_CHANNEL_HANDLE = "TotalHalibut"
+)
+
+/////////////////////////////
+//////////// MODELS
+///////////////////////////
+
+// model for a generic youtube answer
+// We only define the fields we want to capture
+// from the json answer from the API
+
+type PageInfo struct {
+	TotalResults   int
+	ResultsPerPage int
+}
+
+type YoutubeAnswer struct {
+	Kind  string
+	Etag  string
+	Items []Item
+	PageInfo
+
+	// Will be used to get the actual we need (resources)
+	// Now we need to get the content inside Items in each Answer
+	// Let's build a type(model) for one Item
+	// interface{} means any type like void* in C
+	// Now we can use the ChannelItem type
+}
+
+type PlayList struct {
+}
+
+type ChannelItem struct {
+}
+
+type ResourceId struct {
+	VideoId string
+}
+
+type PlayListItemSnippet struct {
+	ResourceId ResourceId
+}
+
+type PlayListItem struct {
+	Snippet PlayListItemSnippet
+}
+
+// Our container type Item
+// We will embed other type of Items here
+// to extract data we want from our resources with json.Unmarshal
+// Unmarshal should set to nil json fields which are not defined
+// There might be a cleaner way to do this
+// Ref on embedding: https://github.com/luciotato/golang-notes/blob/master/OOP.md#golang-embedding-is-akin-to-multiple-inheritance-with-non-virtual-methods
+
+type Item struct {
+	Id string
+	ChannelItem
+	PlayList
+	PlayListItem
+}
+
+////////////////////////////
+////// API Functions
+///////////////////////////
+
+// Helper function to build our youtube query URL
+func buildUrl(resource string, params map[string]string) string {
+
+	// we build a url.Values object from a map of key,values
+
+	queryParams := url.Values{}
+
+	// Automatically add the API key params to all our calls
+	queryParams.Set("key", YOUTUBE_API_KEY)
+
+	for k, v := range params {
+		queryParams.Set(k, v)
+	}
+
+	// Build URL
+	queryUrl := fmt.Sprint(YOUTUBE_API_ENDPOINT, resource, "?", queryParams.Encode())
+	return queryUrl
+}
+
+// We can make this function more generic and reuse it for other resources
+// Since youtube API sends the actual data inside ITEMS we make a func
+// that returns the list of Items based on the resource and params we pass
+// This func returns a list of any kind of Item type (channel, playlist, video ...)
+
+func getResource(resource string, params map[string]string) []Item {
+
+	queryUrl := buildUrl(resource, params)
+	resp, err := http.Get(queryUrl)
+
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	data, _ := ioutil.ReadAll(resp.Body)
+
+	answer := &YoutubeAnswer{}
+	jsonErr := json.Unmarshal(data, answer)
+
+	if jsonErr != nil {
+		log.Fatal(err)
+	}
+
+	// We need to make an type embedding so we can have polymorphism
+	// Interfaces are used to implement methods , my mistake
+	// We want to return a list of any "kind" if Item
+
+	return answer.Items
+}
+
+func getChannelId(channelHandle string) string {
+
+	// Use our buildUrl func
+	params := map[string]string{
+		"key":         YOUTUBE_API_KEY,
+		"forUsername": channelHandle,
+		"part":        "id",
+	}
+
+	queryUrl := buildUrl("channels", params)
+
+	// Test request
+	resp, err := http.Get(queryUrl)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	data, _ := ioutil.ReadAll(resp.Body)
+	answer := &YoutubeAnswer{}
+	jsonErr := json.Unmarshal(data, answer)
+
+	if jsonErr != nil {
+		log.Fatal(err)
+	}
+
+	return answer.Items[0].Id
+}
+
+///////////////////////////////////
+
+func main() {
+
+	// Get channel data
+	channelParams := map[string]string{
+		"forUsername": TEST_CHANNEL_HANDLE,
+		"part":        "id",
+	}
+	channel := getResource("channels", channelParams)[0]
+
+	// Use channel Id to get list of playlists
+
+	playlistsParams := map[string]string{
+		"part":      "id",
+		"channelId": channel.Id,
+	}
+
+	playlists := getResource("playlists", playlistsParams)
+
+	// Step 2 get list of playlists from channel
+
+	fmt.Printf("Id for channel %s is: %s\n", TEST_CHANNEL_HANDLE, channel.Id)
+	fmt.Println("_________Playlists IDS___________\n")
+
+	// Step 3 get list of videos inside each playlist
+	// Videos are PlayListItem objects
+	// We want the id of videos also (part=id,snippet)
+
+	for _, pl := range playlists {
+		fmt.Printf("\n%+v", pl)
+
+		fmt.Printf("playlist: %s\n", pl.Id)
+
+		playListItemsParams := map[string]string{
+			"part":       "id,snippet",
+			"playlistId": pl.Id,
+		}
+
+		playListItems := getResource("playlistItems", playListItemsParams)
+
+		fmt.Printf("video IDs for playlist %s:\n", pl.Id)
+
+		for _, plI := range playListItems {
+			fmt.Printf("video id : %s\n", plI.PlayListItem.Snippet.ResourceId.VideoId)
+
+		}
+
+	}
+
+	return
+}