Add asset extractor script

tools/asset_extractor/.gitignore

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+!asset_extractor.py

tools/asset_extractor/asset_extractor.py

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+from pathlib import Path
+import os
+import sys
+
+def extract_assets(variant):
+    print(f'Extract assets from {variant}.')
+    map = {
+        'USA': 'baserom.gba',
+        'EU': 'baserom_eu.gba',
+        'JP': 'baserom_jp.gba',
+        'DEMO': 'baserom_demo.gba'
+    }
+    baserom = None
+    with open(map[variant], 'rb') as file:
+        baserom = bytearray(file.read())
+
+    with open(f'assets_{variant}.csv', 'r') as file:
+        for line in file:
+            (path,start,size,_) = line.split(',')
+            if os.path.isfile(path):
+               print(f'{path} already extracted.') 
+            else:
+                print(f'Extracting {path}...')
+                Path(os.path.dirname(path)).mkdir(parents=True, exist_ok=True)
+                with open(path, 'wb') as output:
+                    output.write(baserom[int(start,16):int(start,16)+int(size,16)])
+def main():
+    
+    if len(sys.argv) == 1:
+        extract_assets('USA')
+    elif len(sys.argv) == 2:
+        extract_assets(sys.argv[1].upper())
+    else:
+        print('Usage: asset_extractor.py VARIANT')
+
+if __name__ == '__main__':
+    main()