refactor: move BPM fetching logic into provider package

internal/provider/bpm.go

@@ -0,0 +1,180 @@
+package provider
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	neturl "net/url"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/PuerkitoBio/goquery"
+)
+
+type BPMProvider struct{}
+
+type BPMKey struct {
+	BPM string
+	Key string
+}
+
+func (p BPMProvider) Fetch(ctx context.Context, httpClient *http.Client, artist, title, duration string) (BPMKey, error) {
+	url, err := p.findSongURL(ctx, httpClient, artist, title, duration)
+	if err != nil {
+		return BPMKey{}, err
+	}
+
+	html, err := p.fetchPage(ctx, httpClient, url)
+	if err != nil {
+		return BPMKey{}, err
+	}
+
+	return p.parse(html)
+}
+
+func (p BPMProvider) findSongURL(ctx context.Context, httpClient *http.Client, artist, title, duration string) (string, error) {
+	rootUrl := "https://songbpm.com"
+	reqUrl := rootUrl + "/searches"
+
+	values := neturl.Values{}
+	values.Add("query", fmt.Sprintf("%s %s", artist, title))
+
+	req, err := http.NewRequestWithContext(ctx, "POST", reqUrl, bytes.NewBufferString(values.Encode()))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Origin", "https://songbpm.com")
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	doc, err := goquery.NewDocumentFromReader(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	var (
+		found bool
+		url   string
+	)
+
+	doc.Find("a.flex.flex-col").EachWithBreak(func(_ int, selection *goquery.Selection) bool {
+		lowerSelection := strings.ToLower(selection.Text())
+		lowerTitle := strings.ToLower(title)
+		lowerArtist := strings.ToLower(artist)
+		if !strings.Contains(lowerSelection, lowerTitle) || !strings.Contains(lowerSelection, lowerArtist) {
+			return true
+		}
+
+		durationStr := strings.TrimSpace(selection.Find("div.flex-1.flex-col.items-center").Eq(1).Find("span.text-2xl").Text())
+		parts := strings.Split(durationStr, ":")
+		if len(parts) != 2 {
+			return true
+		}
+		minutes, err := strconv.Atoi(parts[0])
+		if err != nil {
+			return true
+		}
+		seconds, err := strconv.Atoi(parts[1])
+		if err != nil {
+			return true
+		}
+
+		foundDuration := minutes*60 + seconds
+		wantDuration, err := strconv.Atoi(duration)
+		if err != nil {
+			return true
+		}
+
+		const durationToleranceSec = 2
+		if foundDuration <= (wantDuration-durationToleranceSec) || foundDuration >= (wantDuration+durationToleranceSec) {
+			return true
+		}
+
+		url = selection.AttrOr("href", "")
+		found = true
+
+		return false
+	})
+
+	if !found {
+		return "", fmt.Errorf("no data found")
+	}
+
+	return rootUrl + url, nil
+}
+
+func (p BPMProvider) fetchPage(ctx context.Context, httpClient *http.Client, url string) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return "", err
+	}
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return string(body), nil
+}
+
+func (p BPMProvider) parse(html string) (BPMKey, error) {
+	bpmRegex := regexp.MustCompile(`tempo of <span[^>]*>(\d+) BPM`)
+	bpmMatch := bpmRegex.FindStringSubmatch(html)
+
+	keyRegex := regexp.MustCompile(`with a <span[^>]*>([A-G](?:♯|#|♭|b)?(?:/[A-G](?:♯|#|♭|b)?)?)</span> key`)
+	keyMatch := keyRegex.FindStringSubmatch(html)
+
+	modeRegex := regexp.MustCompile(`a  <span[^>]*>([a-z]+)</span> mode`)
+	modeMatch := modeRegex.FindStringSubmatch(html)
+
+	if len(bpmMatch) != 2 || len(keyMatch) != 2 || len(modeMatch) != 2 {
+		return BPMKey{}, fmt.Errorf("no data found")
+	}
+
+	isMinor := false
+	bpm := bpmMatch[1]
+	key := keyMatch[1]
+	if modeMatch[1] == "minor" {
+		isMinor = true
+	}
+
+	if strings.Contains(key, "/") {
+		parts := strings.Split(key, "/")
+		key = parts[0]
+	}
+
+	key = strings.ReplaceAll(key, "♯", "#")
+	key = strings.ReplaceAll(key, "♭", "b")
+
+	if isMinor && !strings.HasSuffix(key, "m") {
+		key += "m"
+	}
+
+	return BPMKey{
+		BPM: bpm,
+		Key: key,
+	}, nil
+
+}