feat: 支持下载 cc 字幕 (#234)

crates/bili_sync/src/bilibili/mod.rs

@@ -25,6 +25,7 @@ mod danmaku;
 mod error;
 mod favorite_list;
 mod submission;
+mod subtitle;
 mod video;
 mod watch_later;
 
@@ -197,4 +198,26 @@ mod tests {
         assert!(videos.iter().all(|v| matches!(v, VideoInfo::Submission { .. })));
         assert!(videos.iter().rev().is_sorted_by_key(|v| v.release_datetime()));
     }
+
+    #[ignore = "only for manual test"]
+    #[tokio::test]
+    async fn test_subtitle_parse() -> Result<()> {
+        let bili_client = BiliClient::new();
+        let Ok(Some(mixin_key)) = bili_client.wbi_img().await.map(|wbi_img| wbi_img.into()) else {
+            panic!("获取 mixin key 失败");
+        };
+        set_global_mixin_key(mixin_key);
+        let video = Video::new(&bili_client, "BV1gLfnY8E6D".to_string());
+        let pages = video.get_pages().await?;
+        println!("pages: {:?}", pages);
+        let subtitles = video.get_subtitles(&pages[0]).await?;
+        for subtitle in subtitles {
+            println!(
+                "{}: {}",
+                subtitle.lan,
+                subtitle.body.to_string().chars().take(200).collect::<String>()
+            );
+        }
+        Ok(())
+    }
 }

crates/bili_sync/src/bilibili/subtitle.rs

@@ -0,0 +1,75 @@
+use std::fmt::Display;
+
+#[derive(Debug, serde::Deserialize)]
+pub struct SubTitlesInfo {
+    pub subtitles: Vec<SubTitleInfo>,
+}
+
+#[derive(Debug, serde::Deserialize)]
+pub struct SubTitleInfo {
+    pub lan: String,
+    pub subtitle_url: String,
+}
+
+pub struct SubTitle {
+    pub lan: String,
+    pub body: SubTitleBody,
+}
+
+#[derive(Debug, serde::Deserialize)]
+pub struct SubTitleBody(pub Vec<SubTitleItem>);
+
+#[derive(Debug, serde::Deserialize)]
+pub struct SubTitleItem {
+    from: f64,
+    to: f64,
+    content: String,
+}
+
+impl SubTitleInfo {
+    pub fn is_ai_sub(&self) -> bool {
+        // ai： aisubtitle.hdslb.com/bfs/ai_subtitle/xxxx
+        // 非 ai： aisubtitle.hdslb.com/bfs/subtitle/xxxx
+        self.subtitle_url.contains("ai_subtitle")
+    }
+}
+
+impl Display for SubTitleBody {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for (idx, item) in self.0.iter().enumerate() {
+            writeln!(f, "{}", idx)?;
+            writeln!(f, "{} --> {}", format_time(item.from), format_time(item.to))?;
+            writeln!(f, "{}", item.content)?;
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+fn format_time(time: f64) -> String {
+    let (second, millisecond) = (time.trunc(), (time.fract() * 1e3) as u32);
+    let (hour, minute, second) = (
+        (second / 3600.0) as u32,
+        ((second % 3600.0) / 60.0) as u32,
+        (second % 60.0) as u32,
+    );
+    format!("{:02}:{:02}:{:02},{:03}", hour, minute, second, millisecond)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_format_time() {
+        // float 解析会有精度问题，但误差几毫秒应该不太关键
+        // 想再健壮一点就得手写 serde_json 解析拆分秒和毫秒，然后分别处理了
+        let testcases = [
+            (0.0, "00:00:00,000"),
+            (1.5, "00:00:01,500"),
+            (206.45, "00:03:26,449"),
+            (360001.23, "100:00:01,229"),
+        ];
+        for (time, expect) in testcases.iter() {
+            assert_eq!(super::format_time(*time), *expect);
+        }
+    }
+}

crates/bili_sync/src/bilibili/video.rs

@@ -8,6 +8,7 @@ use crate::bilibili::analyzer::PageAnalyzer;
 use crate::bilibili::client::BiliClient;
 use crate::bilibili::credential::encoded_query;
 use crate::bilibili::danmaku::{DanmakuElem, DanmakuWriter, DmSegMobileReply};
+use crate::bilibili::subtitle::{SubTitle, SubTitleBody, SubTitleInfo, SubTitlesInfo};
 use crate::bilibili::{Validate, VideoInfo, MIXIN_KEY};
 
 static MASK_CODE: u64 = 2251799813685247;
@@ -164,6 +165,44 @@ impl<'a> Video<'a> {
             .validate()?;
         Ok(PageAnalyzer::new(res["data"].take()))
     }
+
+    pub async fn get_subtitles(&self, page: &PageInfo) -> Result<Vec<SubTitle>> {
+        let mut res = self
+            .client
+            .request(Method::GET, "https://api.bilibili.com/x/player/wbi/v2")
+            .await
+            .query(&encoded_query(
+                vec![("cid", &page.cid.to_string()), ("bvid", &self.bvid), ("aid", &self.aid)],
+                MIXIN_KEY.load().as_deref(),
+            ))
+            .send()
+            .await?
+            .json::<serde_json::Value>()
+            .await?
+            .validate()?;
+        // 接口返回的信息，包含了一系列的字幕，每个字幕包含了字幕的语言和 json 下载地址
+        let subtitles_info: SubTitlesInfo = serde_json::from_value(res["data"]["subtitle"].take())?;
+        let tasks = subtitles_info
+            .subtitles
+            .into_iter()
+            .filter(|v| !v.is_ai_sub())
+            .map(|v| self.get_subtitle(v))
+            .collect::<FuturesUnordered<_>>();
+        tasks.try_collect().await
+    }
+
+    async fn get_subtitle(&self, info: SubTitleInfo) -> Result<SubTitle> {
+        let mut res = self
+            .client
+            .client // 这里可以直接使用 inner_client，因为该请求不需要鉴权
+            .request(Method::GET, format!("https:{}", &info.subtitle_url).as_str(), None)
+            .send()
+            .await?
+            .json::<serde_json::Value>()
+            .await?;
+        let body: SubTitleBody = serde_json::from_value(res["body"].take())?;
+        Ok(SubTitle { lan: info.lan, body })
+    }
 }
 
 fn bvid_to_aid(bvid: &str) -> u64 {