feat: launch privacy-first local lyrics tool

qq.go

@@ -0,0 +1,170 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const (
+	searchEndpoint   = "https://c.y.qq.com/soso/fcgi-bin/search_for_qq_cp"
+	lyricsEndpoint   = "https://c.y.qq.com/lyric/fcgi-bin/fcg_query_lyric_new.fcg"
+	maxUpstreamBytes = 4 << 20
+)
+
+type song struct {
+	Name     string `json:"name"`
+	MID      string `json:"mid"`
+	Singer   string `json:"singer"`
+	Album    string `json:"album"`
+	Interval int    `json:"interval"`
+}
+
+type lyricResult struct {
+	Lyric string `json:"lyric"`
+	Trans string `json:"trans"`
+	Code  int    `json:"code"`
+}
+
+type qqAPI interface {
+	Search(string, int) ([]song, error)
+	Lyrics(string) (lyricResult, error)
+}
+
+type qqClient struct {
+	httpClient     *http.Client
+	searchEndpoint string
+	lyricsEndpoint string
+}
+
+func newQQClient() *qqClient {
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	transport.MaxIdleConns = 8
+	transport.MaxIdleConnsPerHost = 4
+	transport.ResponseHeaderTimeout = 10 * time.Second
+	return &qqClient{
+		httpClient: &http.Client{
+			Timeout:   15 * time.Second,
+			Transport: transport,
+			CheckRedirect: func(_ *http.Request, _ []*http.Request) error {
+				return errors.New("unexpected redirect from fixed QQ Music endpoint")
+			},
+		},
+		searchEndpoint: searchEndpoint,
+		lyricsEndpoint: lyricsEndpoint,
+	}
+}
+
+func (c *qqClient) Search(keyword string, limit int) ([]song, error) {
+	query := url.Values{
+		"format":     {"json"},
+		"p":          {"1"},
+		"n":          {fmt.Sprint(limit)},
+		"w":          {keyword},
+		"outCharset": {"utf-8"},
+	}
+	var response struct {
+		Code    int    `json:"code"`
+		Message string `json:"message"`
+		Data    struct {
+			Song struct {
+				List []struct {
+					SongName  string `json:"songname"`
+					SongMID   string `json:"songmid"`
+					AlbumName string `json:"albumname"`
+					Interval  int    `json:"interval"`
+					Singer    []struct {
+						Name string `json:"name"`
+					} `json:"singer"`
+				} `json:"list"`
+			} `json:"song"`
+		} `json:"data"`
+	}
+	if err := c.getJSON(c.searchEndpoint, query, &response); err != nil {
+		return nil, err
+	}
+	if response.Code != 0 {
+		return nil, fmt.Errorf("QQ Music search failed: %s", response.Message)
+	}
+	result := make([]song, 0, len(response.Data.Song.List))
+	for _, item := range response.Data.Song.List {
+		if item.SongMID == "" {
+			continue
+		}
+		names := make([]string, 0, len(item.Singer))
+		for _, singer := range item.Singer {
+			if singer.Name != "" {
+				names = append(names, singer.Name)
+			}
+		}
+		result = append(result, song{
+			Name: item.SongName, MID: item.SongMID,
+			Singer: strings.Join(names, " / "), Album: item.AlbumName, Interval: item.Interval,
+		})
+	}
+	return result, nil
+}
+
+func (c *qqClient) Lyrics(mid string) (lyricResult, error) {
+	query := url.Values{
+		"format": {"json"}, "songmid": {mid}, "outCharset": {"utf-8"}, "nobase64": {"1"},
+	}
+	var result lyricResult
+	if err := c.getJSON(c.lyricsEndpoint, query, &result); err != nil {
+		return lyricResult{}, err
+	}
+	if result.Code != 0 || result.Lyric == "" {
+		return lyricResult{}, errors.New("lyrics are not available for this track")
+	}
+	return result, nil
+}
+
+func (c *qqClient) getJSON(endpoint string, query url.Values, destination any) error {
+	request, err := http.NewRequest(http.MethodGet, endpoint+"?"+query.Encode(), nil)
+	if err != nil {
+		return err
+	}
+	request.Header.Set("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 Chrome/131 Safari/537.36")
+	request.Header.Set("Referer", "https://y.qq.com/")
+	request.Header.Set("Origin", "https://y.qq.com")
+	request.Header.Set("Accept", "application/json,text/plain,*/*")
+	response, err := c.httpClient.Do(request)
+	if err != nil {
+		return fmt.Errorf("QQ Music request failed: %w", err)
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		return fmt.Errorf("QQ Music returned HTTP %d", response.StatusCode)
+	}
+	body, err := io.ReadAll(io.LimitReader(response.Body, maxUpstreamBytes+1))
+	if err != nil {
+		return err
+	}
+	if len(body) > maxUpstreamBytes {
+		return errors.New("QQ Music response exceeded the safety limit")
+	}
+	body = unwrapJSONP(body)
+	if err := json.Unmarshal(body, destination); err != nil {
+		return errors.New("QQ Music returned an invalid response")
+	}
+	return nil
+}
+
+func unwrapJSONP(body []byte) []byte {
+	body = bytes.TrimSpace(body)
+	if len(body) == 0 || body[0] == '{' || body[0] == '[' {
+		return body
+	}
+	left := bytes.IndexByte(body, '(')
+	right := bytes.LastIndexByte(body, ')')
+	if left >= 0 && right > left {
+		return bytes.TrimSpace(body[left+1 : right])
+	}
+	return body
+}