package linkinfo

import (
	"encoding/json"
	"errors"
	"fmt"
	"math"
	"net/http"
	"net/url"
	"regexp"
	"strings"
	"time"
)

const youtubeApiUrl = "https://www.googleapis.com/youtube/v3/videos"

var (
	youtubeHosts   = []string{"youtube.com", "youtu.be"}
	durationRegexp = regexp.MustCompile("^00:")
)

type YoutubeOptions struct {
	Option

	Key string
}

type YoutubeInfoApi struct {
	api  *LinkInfoApi
	opts *YoutubeOptions
}

type youtubeResponse struct {
	Error *youtubeError  `json:"error"`
	Items []*youtubeItem `json:"items"`
}

type youtubeError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

type youtubeItem struct {
	Snippet        *youtubeSnippet        `json:"snippet"`
	ContentDetails *youtubeContentDetails `json:"contentDetails"`
}

type youtubeSnippet struct {
	Title       string `json:"title"`
	Description string `json:"description"`
}

type youtubeContentDetails struct {
	Duration string `json:"duration"`
}

func (i *YoutubeInfoApi) Handler(link string) (*LinkInfo, error) {
	u, err := url.Parse(link)

	if err != nil {
		return nil, err
	}

	var id string

	query := u.Query()

	if query != nil && query.Get("v") != "" {
		id = query.Get("v")
	} else if u.Host == "youtu.be" {
		id = u.Path[1:]
	}

	if id == "" {
		return i.api.DefaultLinkHandler(link)
	}

	params := &url.Values{}

	params.Set("id", id)
	params.Set("part", "id, snippet, contentDetails")
	params.Set("key", i.opts.Key)

	req, err := http.NewRequest("GET", youtubeApiUrl+"?"+params.Encode(), nil)

	if err != nil {
		return nil, err
	}

	res, err := i.api.Client.Do(req)

	if err != nil {
		return nil, err
	}

	var response youtubeResponse

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, err
	}

	if response.Error != nil {
		return nil, errors.New(response.Error.Message)
	}

	if len(response.Items) < 1 {
		return nil, errors.New("video not found")
	}

	item := response.Items[0]

	duration, err := time.ParseDuration(strings.ToLower(item.ContentDetails.Duration[2:]))

	trimmedDuration := durationRegexp.ReplaceAllString(humanizeDuration(duration), "")

	ret := &LinkInfo{
		Title:       item.Snippet.Title + " [" + trimmedDuration + "]",
		Description: item.Snippet.Description,
		Duration:    item.ContentDetails.Duration,
	}

	return ret, nil
}

// https://gist.github.com/harshavardhana/327e0577c4fed9211f65#gistcomment-2366908
func humanizeDuration(duration time.Duration) string {
	hours := int64(duration.Hours())
	minutes := int64(math.Mod(duration.Minutes(), 60))
	seconds := int64(math.Mod(duration.Seconds(), 60))

	chunks := []struct {
		singularName string
		amount       int64
	}{
		{"hour", hours},
		{"minute", minutes},
		{"second", seconds},
	}

	parts := make([]string, 0)

	for _, chunk := range chunks {
		parts = append(parts, fmt.Sprintf("%02d", chunk.amount))
	}

	return strings.Join(parts, ":")
}