Postpone ASS generation (#64)

config/example.jsonc

@@ -48,6 +48,16 @@
     // -ac 1 -y "${output}"`.
     "script": ""
   },
+  "subtitle": {
+    // The style of subtitles. It can be one of the `traditional` or `karaoke`.
+    //
+    // * `traditional`: render subtitles by lines.
+    // * `karaoke`: render subtitles by words. Certain lyrics without karaoke
+    //   format support will fallback to `traditional` rendering.
+    //
+    // If it is unspecified, `karaoke` will be used by default.
+    "style": "karaoke"
+  },
   "providers": {
     "mv": {
       "bilibili": {

server/components/downloader.js

@@ -76,10 +76,13 @@ class Downloader {
     this.downloading = true;
     entry.onDownload();
     const lyrics = entry.lyrics();
-    const lyricsPath = `${this.location}/${lyrics.id()}.ass`;
+    const lyricsPath = `${this.location}/${lyrics.id()}.json`;
     if (!fs.existsSync(lyricsPath)) {
       try {
-        fs.writeFileSync(lyricsPath, await lyrics.formattedLyrics());
+        fs.writeFileSync(
+          lyricsPath,
+          JSON.stringify(await lyrics.formattedLyrics())
+        );
       } catch (e) {
         console.error(e);
         // Clean up.

server/components/index.js

@@ -2,3 +2,4 @@ export { default as Database } from "./database";
 export { default as Downloader } from "./downloader";
 export { default as Encoder } from "./encoder";
 export { default as Player } from "./player";
+export { default as Subtitler } from "./subtitler";

server/components/subtitler.js

@@ -0,0 +1,151 @@
+import { Style } from "../models/lyrics/common/lyrics";
+import { padStart } from "../utils";
+
+const compileWord = (word) => {
+  const duration = Math.round((word["endTime"] - word["startTime"]) * 100);
+  return `{\\K${duration}}${word["word"]}`;
+};
+
+const formatTime = (time) => {
+  const hour = parseInt(String(time / 3600));
+  const min = parseInt(String((time - 3600 * hour) / 60));
+  const sec = parseInt(String(time - 3600 * hour - 60 * min));
+  const mil = Math.min(
+    Math.round((time - 3600 * hour - 60 * min - sec) * 100),
+    99
+  );
+  return `${hour}:${padStart(min, 2)}:${padStart(sec, 2)}.${padStart(mil, 2)}`;
+};
+
+const formatColor = (color) => {
+  return color.toUpperCase().replace("#", "&H");
+};
+
+class Subtitler {
+  ASS_STYLES = ["K1", "K2"];
+
+  style = Style.Karaoke;
+  // TODO: These constants should be configurable.
+  ADVANCE = 5;
+  DELAY = 1;
+  FONTSIZE = 24;
+  PRIMARY_COLOR = "#000000FF";
+  SECONDARY_COLOR = "#00FFFFFF";
+  OUTLINE_COLOR = "#00000000";
+  BACKGROUND_COLOR = "#00000000";
+  BOLD = false;
+  OUTLINE = 2;
+  SHADOW = 0;
+
+  constructor(style) {
+    this.style = style;
+  }
+
+  compile = (lines, lyrics) => {
+    const style = this.bestStyle(lyrics.style());
+    const dialogues = this.dialogues(lines, style);
+    const header = this.header(lyrics.title());
+    return `${header}\n${dialogues}`;
+  };
+
+  header = (title) => {
+    // prettier-ignore
+    return `[Script Info]
+Title: ${title}
+ScriptType: v4.00+
+
+[V4+ Styles]
+Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
+Style: K1,Source Han Serif,${this.FONTSIZE},${formatColor(this.PRIMARY_COLOR)},${formatColor(this.SECONDARY_COLOR)},${formatColor(this.OUTLINE_COLOR)},${formatColor(this.BACKGROUND_COLOR)},${this.BOLD ? 1 : 0},0,0,0,100,100,0,0,1,${this.OUTLINE},${this.SHADOW},1,60,30,80,1
+Style: K2,Source Han Serif,${this.FONTSIZE},${formatColor(this.PRIMARY_COLOR)},${formatColor(this.SECONDARY_COLOR)},${formatColor(this.OUTLINE_COLOR)},${formatColor(this.BACKGROUND_COLOR)},${this.BOLD ? 1 : 0},0,0,0,100,100,0,0,1,${this.OUTLINE},${this.SHADOW},3,30,60,40,1
+[Events]
+Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
+`;
+  };
+
+  dialogue = (line, style, assStyle, advance) => {
+    let words;
+    switch (style) {
+      case Style.Traditional:
+        words = `{\\K${Math.round(advance * 100)}}{\\K0}`;
+        words += line["line"];
+        break;
+      case Style.Karaoke:
+        words = `{\\K${Math.round(advance * 100)}}`;
+        words += line["words"].map(compileWord).join("");
+        break;
+      default:
+        throw new Error(`unexpected style "${style}"`);
+    }
+    return `Dialogue: 0,${formatTime(line["startTime"] - advance)},${formatTime(
+      line["endTime"] + this.DELAY
+    )},${assStyle},,0,0,0,,${words}`;
+  };
+
+  dialogues = (lines, style) => {
+    let result = [];
+    let displays = new Array(this.ASS_STYLES.length).fill(0);
+    for (const line of lines) {
+      // Escape empty lines.
+      if (!line["line"]) {
+        continue;
+      }
+
+      // Identify new paragraphs.
+      let newParagraph = false;
+      const lastEndTime = Math.max(...displays);
+      if (lastEndTime < line["startTime"] - this.ADVANCE) {
+        // Assert there is a new paragraph if there are more than `advance`
+        // blank.
+        newParagraph = true;
+      }
+
+      // Calculate lyrics show in advance time.
+      const priorEndTime = Math.min(...displays);
+      let index = 0;
+      if (!newParagraph) {
+        index = displays.indexOf(priorEndTime);
+      }
+      let advance = Math.max(line["startTime"] - priorEndTime, 0);
+      if (newParagraph) {
+        advance = Math.min(advance, this.ADVANCE);
+      }
+
+      const assStyle = this.ASS_STYLES[index];
+      result.push(this.dialogue(line, style, assStyle, advance));
+
+      // Clean up.
+      if (newParagraph) {
+        displays.fill(line["startTime"] - advance);
+      }
+      displays[index] = line["endTime"] + this.DELAY;
+    }
+    return result.join("\n");
+  };
+
+  bestStyle = (style) => {
+    switch (style) {
+      case Style.Traditional:
+        switch (this.style) {
+          case Style.Traditional:
+          case Style.Karaoke:
+            return Style.Traditional;
+          default:
+            throw new Error(`unexpected style "${this.style}"`);
+        }
+      case Style.Karaoke:
+        switch (this.style) {
+          case Style.Traditional:
+            return Style.Traditional;
+          case Style.Karaoke:
+            return Style.Karaoke;
+          default:
+            throw new Error(`unexpected style "${this.style}"`);
+        }
+      default:
+        throw new Error(`unexpected style "${style}"`);
+    }
+  };
+}
+
+export default Subtitler;

server/models/lyrics/common/lyrics.js

@@ -14,27 +14,15 @@ class Word {
     this.endTime = endTime;
   }
 
-  compile = () => {
-    const duration = Math.round((this.endTime - this.startTime) * 100);
-    return `{\\K${duration}}${this.word}`;
+  format = () => {
+    return {
+      word: this.word,
+      startTime: this.startTime,
+      endTime: this.endTime,
+    };
   };
 }
 
-const padTime = (timeComponent) => {
-  return String(timeComponent).padStart(2, "0");
-};
-
-const convertTime = (time) => {
-  const hour = parseInt(String(time / 3600));
-  const min = parseInt(String((time - 3600 * hour) / 60));
-  const sec = parseInt(String(time - 3600 * hour - 60 * min));
-  const mil = Math.min(
-    Math.round((time - 3600 * hour - 60 * min - sec) * 100),
-    99
-  );
-  return `${hour}:${padTime(min)}:${padTime(sec)}.${padTime(mil)}`;
-};
-
 class Line {
   line;
   startTime;
@@ -47,25 +35,13 @@ class Line {
     this.endTime = endTime;
   }
 
-  isEmpty = () => {
-    return this.line.trim().length === 0;
-  };
-
-  compile = (style, assStyle, advance, delay) => {
-    let words = this.line;
-    switch (style) {
-      case Style.Traditional:
-        break;
-      case Style.Karaoke:
-        words = `{\\K${Math.round(advance * 100)}}`;
-        words += this.words.map((value) => value.compile()).join("");
-        break;
-      default:
-        throw new Error(`unexpected style "${style}"`);
-    }
-    return `Dialogue: 0,${convertTime(this.startTime - advance)},${convertTime(
-      this.endTime + delay
-    )},${assStyle},,0,0,0,,${words}`;
+  format = () => {
+    return {
+      line: this.line,
+      startTime: this.startTime,
+      endTime: this.endTime,
+      words: this.words.map((value) => value.format()),
+    };
   };
 }
 

server/models/lyrics/index.js

@@ -1 +1,3 @@
+export { Style } from "./common";
+
 export { Provider as PetitLyricsProvider } from "./petit-lyrics";

server/models/lyrics/petit-lyrics/entry.js

@@ -1,7 +1,6 @@
 import fetch from "node-fetch";
 import { parseStringPromise as parseXMLString } from "xml2js";
 import { Line, Style, Word } from "../common";
-import { compile, header } from "../utils";
 
 const NAME = "petit_lyrics";
 
@@ -74,7 +73,6 @@ class Entry {
   };
 
   formattedLyrics = async () => {
-    const h = header(this.title_);
     const rawLyrics = await this.rawLyrics();
     const text = await parseXMLString(rawLyrics);
 
@@ -96,8 +94,7 @@ class Entry {
       }
       ls.push(l);
     }
-    const result = compile(this.style(), ls);
-    return `${h}${result}`;
+    return ls.map((value) => value.format());
   };
 
   rawLyrics = async () => {