perf: Optimize asciinema cast processing with line-by-line streaming and early exit

scripts/redact-cast.py

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 import json
 import os
-import re
 import sys
 
 import pyte
@@ -16,44 +15,47 @@ def main():
     input_file = sys.argv[1]
     output_file = sys.argv[2]
     
-    # Read and parse the cast file
-    with open(input_file, "r") as f:
-        # First line is header
-        header = f.readline().strip()
+    # Count total lines for progress bar
+    total_lines = sum(1 for _ in open(input_file, 'r'))
 
-        # Parse header to extract terminal dimensions
+    with open(input_file, "r") as fin, open(output_file, "w") as fout:
+        # Process header
+        header = fin.readline().strip()
+        fout.write(header + "\n")
+        
+        # Parse header for terminal dimensions
         header_data = json.loads(header)
         width = header_data.get("width", 80)
         height = header_data.get("height", 24)
-
         print(f"Terminal dimensions: {width}x{height}")
         
-        # Initialize pyte screen and stream with dimensions from header
+        # Initialize terminal emulator
         screen = pyte.Screen(width, height)
         stream = pyte.Stream(screen)
         
-        # Read the events
-        events = [json.loads(line) for line in f if line.strip()]
+        # Process events line by line
+        for line in tqdm(fin, desc="Processing events", total=total_lines-1):
+            if not line.strip():
+                continue
                 
-    # Write the header to the output file
-    with open(output_file, "w") as f:
-        f.write(header + "\n")
+            event = json.loads(line)
             
-        # Process each event through the terminal emulator and stream to file
-        for event in tqdm(events, desc="Processing events"):
-            # Process the event in the terminal
-            if len(event) >= 3 and event[1] == "o":  # Output event
+            # Only run terminal emulation for output events
+            if len(event) >= 3 and event[1] == "o":
                 stream.feed(event[2])
                 
-                # Check if "Atuin" is visible on screen
-                if any(
-                        ("Atuin" in line)
-                        for line in screen.display
-                ):
+                # Check if "Atuin" is visible on screen - exit early if found
+                atuin_visible = False
+                for display_line in screen.display:
+                    if "Atuin" in display_line:
+                        atuin_visible = True
+                        break
+                        
+                if atuin_visible:
                     continue  # Skip this event
             
-            # Write this event directly to the output file
-            f.write(json.dumps(event) + "\n")
+            # Write event to output file
+            fout.write(json.dumps(event) + "\n")
 
 
 if __name__ == "__main__":