Adjust file format and update documentation

Author: jgoerzen

README.md

@@ -187,29 +187,29 @@ UI does, this mode allows multiple blocks of each type.  `--batch` reads from
 stdin.  Each line must begin with a command, a colon, and then details.  The
 commands are:
 
-* `TEXTSTART`: Starts a new text block.  Any previous text lines will be printed
+* `LABELLE-LABEL-SPEC-VERSION:1` must be the first line.
+* `TEXT`: Starts a new text block.  Any previous text lines will be printed
   first.
-* `TEXTADD`: Adds an additional line to the current block of text.  Used to
-  create multiline text blocks.
-* `QRSTART`: Creates a QR code block
-* `QRADD`: Adds additional lines to the text that will be encoded to form the QR
-  code (rarely used)
+* `NEWLINE`: Adds an additional line to the current block of text or QR. Used to
+  create multiline blocks.
+* `QR`: Creates a QR code block
 
 For instance, this input:
 
 ```text
-TEXTSTART:FD12
-TEXTADD:2013
-QRSTART:1234
-TEXTSTART:BIG
-TEXTSTART:LINE1
-TEXTADD:LINE2
-QRSTART:12345
+LABELLE-LABEL-SPEC-VERSION:1
+TEXT:FD12
+NEWLINE:2013
+QR:1234
+TEXT:BIG
+TEXT:LINE1
+NEWLINE:LINE2
+QR:12345
 ```
 
 Creates a label with:
 
-* A 2-line text block (first like `FD12`, second line `2013`)
+* A 2-line text block (first line `FD12`, second line `2013`)
 * Then, a QR code for 1234
 * Then, a line-line text block with the text `BIG`
 * Then, another 2-line text block

src/labelle/cli/cli.py

@@ -505,45 +505,48 @@ def render_text(lines):
         render_engines.append(PictureRenderEngine(picture))
 
     if batch:
-        text_accumulator: List[str] = []
-        qr_accumulator: List[str] = []
-
-        def flush_text():
-            nonlocal text_accumulator
-            if len(text_accumulator) > 0:
-                render_text(text_accumulator)
-                text_accumulator = []
-
-        def flush_qr():
-            nonlocal qr_accumulator
-            if len(qr_accumulator) > 0:
+        accumulator: List[str] = []
+        accumulator_type: str = "empty"
+
+        def flush_all():
+            nonlocal accumulator
+            nonlocal accumulator_type
+            if accumulator_type == "text":
+                render_text(accumulator)
+            elif accumulator_type == "qr":
                 render_engines.append(
-                    QrRenderEngine(qr_callback("\n".join(qr_accumulator)))
+                    QrRenderEngine(qr_callback("\n".join(accumulator)))
                 )
-                qr_accumulator = []
 
-        def flush_both():
-            flush_text()
-            flush_qr()
+            accumulator = []
+            accumulator_type = "empty"
+
+        # Verify version
+        line = sys.stdin.readline().strip()
+        parts = line.split(":", 1)
+        if not (parts[0] == "LABELLE-LABEL-SPEC-VERSION" and parts[1] == "1"):
+            err_console = Console(stderr=True)
+            err_console.print(
+                "Error: Batch doesn't begin with LABELLE-LABEL-SPEC-VERSION:1"
+            )
+            raise typer.Exit()
 
         for line in sys.stdin:
             line = line.rstrip("\r\n")
             parts = line.split(":", 1)
-            if parts[0] == "TEXTSTART":
-                flush_both()
-                text_accumulator.append(parts[1])
-            elif parts[0] == "TEXTADD":
-                flush_qr()
-                text_accumulator.append(parts[1])
-            elif parts[0] == "QRSTART":
-                flush_both()
-                qr_accumulator.append(parts[1])
-            elif parts[0] == "QRADD":
-                flush_text()
-                qr_accumulator.append(parts[1])
+            if parts[0] == "TEXT":
+                flush_all()
+                accumulator_type = "text"
+                accumulator.append(parts[1])
+            elif parts[0] == "QR":
+                flush_all()
+                accumulator_type = "qr"
+                accumulator.append(parts[1])
+            elif parts[0] == "NEWLINE":
+                accumulator.append(parts[1])
             else:
                 print("WARNING: invalid command", line)
-        flush_both()
+        flush_all()
 
     if fixed_length is None:
         min_label_mm_len = min_length