Bring back chapters

markut.go

@@ -51,6 +51,14 @@ func (chunk Chunk) Duration() Millis {
 	return chunk.End - chunk.Start
 }
 
+type Chapter struct {
+	Loc Loc
+	Timestamp Millis
+	Label string
+}
+
+const MinYouTubeChapterDuration Millis = 10*1000;
+
 func typeCheckArgs(loc Loc, argsStack []Token, signature ...TokenKind) (args []Token, err error, nextStack []Token) {
 	if len(argsStack) < len(signature) {
 		err = &DiagErr{
@@ -87,6 +95,7 @@ type Cut struct {
 type EvalContext struct {
 	inputPath string
 	chunks []Chunk
+	chapters []Chapter
 	cuts []Cut
 	modified_cuts []int
 
@@ -116,6 +125,11 @@ func (context EvalContext) PrintSummary() {
 		}
 	}
 	fmt.Println()
+	fmt.Println("Chapters:")
+	for _, chapter := range context.chapters {
+		fmt.Printf("- %s - %s\n", millisToTs(chapter.Timestamp), chapter.Label)
+	}
+	fmt.Println()
 	fmt.Printf("Chunks Count: %d\n", len(context.chunks))
 	fmt.Printf("Cuts Count: %d\n", len(context.chunks) - 1)
 	fmt.Println()
@@ -151,6 +165,8 @@ func evalMarkutFile(path string) (context EvalContext, ok bool) {
 	lexer := NewLexer(string(content), path)
 	token := Token{}
 	argsStack := []Token{}
+	chapStack := []Chapter{}
+	var chapOffset Millis = 0
 	for {
 		token, err = lexer.Next()
 		if err != nil {
@@ -280,6 +296,19 @@ func evalMarkutFile(path string) (context EvalContext, ok bool) {
 				}
 				n := len(argsStack)
 				argsStack = append(argsStack, argsStack[n-1])
+			case "chapter":
+				args, err, argsStack = typeCheckArgs(token.Loc, argsStack, TokenString, TokenTimestamp)
+				if err != nil {
+					fmt.Printf("%s: ERROR: type check failed for %s\n", token.Loc, command)
+					fmt.Printf("%s\n", err)
+					ok = false
+					return
+				}
+				chapStack = append(chapStack, Chapter{
+					Loc: args[1].Loc,
+					Label: string(args[0].Text),
+					Timestamp: args[1].Timestamp,
+				})
 			case "puts":
 				args, err, argsStack = typeCheckArgs(token.Loc, argsStack, TokenString)
 				if err != nil {
@@ -437,6 +466,26 @@ func evalMarkutFile(path string) (context EvalContext, ok bool) {
 				}
 
 				context.chunks = append(context.chunks, chunk)
+
+				for _, chapter := range chapStack {
+					if chapter.Timestamp < chunk.Start || chunk.End < chapter.Timestamp {
+						fmt.Printf("%s: ERROR: the timestamp %s of chapter \"%s\" is outside of the the current chunk\n", chapter.Loc, millisToTs(chapter.Timestamp), chapter.Label)
+						fmt.Printf("%s: NOTE: which starts at %s\n", start.Loc, millisToTs(start.Timestamp))
+						fmt.Printf("%s: NOTE: and ends at %s\n", end.Loc, millisToTs(end.Timestamp))
+						ok = false
+						return
+					}
+
+					context.chapters = append(context.chapters, Chapter{
+						Loc: chapter.Loc,
+						Timestamp: chapter.Timestamp - chunk.Start + chapOffset,
+						Label: chapter.Label,
+					})
+				}
+
+				chapOffset += chunk.End - chunk.Start
+
+				chapStack = []Chapter{}
 			default:
 				fmt.Printf("%s: ERROR: Unknown command %s\n", token.Loc, command)
 				ok = false
@@ -449,13 +498,31 @@ func evalMarkutFile(path string) (context EvalContext, ok bool) {
 		}
 	}
 
+	for i := 0; i + 1 < len(context.chapters); i += 1 {
+		duration := context.chapters[i + 1].Timestamp - context.chapters[i].Timestamp;
+		// TODO: angled brackets are not allowed on YouTube. Let's make `chapters` check for that too.
+		if duration < MinYouTubeChapterDuration {
+			fmt.Printf("%s: ERROR: the chapter \"%s\" has duration %s which is shorter than the minimal allowed YouTube chapter duration which is %s (See https://support.google.com/youtube/answer/9884579)\n", context.chapters[i].Loc, context.chapters[i].Label, millisToTs(duration), millisToTs(MinYouTubeChapterDuration));
+			fmt.Printf("%s: NOTE: the chapter ends here\n", context.chapters[i + 1].Loc);
+			ok = false;
+			return;
+		}
+	}
+
 	if len(argsStack) > 0 {
 		ok = false;
 		for i := range argsStack {
 			fmt.Printf("%s: ERROR: unused argument\n", argsStack[i].Loc)
 		}
 	}
 
+	if len(chapStack) > 0 {
+		ok = false;
+		for i := range argsStack {
+			fmt.Printf("%s: ERROR: unused chapter\n", chapStack[i].Loc)
+		}
+	}
+
 	return
 }