"""Recognize image file formats based on their first few bytes."""

from os import PathLike

__all__ = ["what"]

#-------------------------#
# Recognize image headers #
#-------------------------#

def what(file, h=None):
 f = None
 try:
 if h is None:
 if isinstance(file, (str, PathLike)):
 f = open(file, 'rb')
 h = f.read(32)
 else:
 location = file.tell()
 h = file.read(32)
 file.seek(location)
 for tf in tests:
 res = tf(h, f)
 if res:
 return res
 finally:
 if f: f.close()
 return None


#---------------------------------#
# Subroutines per image file type #
#---------------------------------#

tests = []

def test_jpeg(h, f):
 """JPEG data in JFIF or Exif format"""
 if h[6:10] in (b'JFIF', b'Exif'):
 return 'jpeg'

tests.append(test_jpeg)

def test_png(h, f):
 if h.startswith(b'211円PNG\r\n032円\n'):
 return 'png'

tests.append(test_png)

def test_gif(h, f):
 """GIF ('87 and '89 variants)"""
 if h[:6] in (b'GIF87a', b'GIF89a'):
 return 'gif'

tests.append(test_gif)

def test_tiff(h, f):
 """TIFF (can be in Motorola or Intel byte order)"""
 if h[:2] in (b'MM', b'II'):
 return 'tiff'

tests.append(test_tiff)

def test_rgb(h, f):
 """SGI image library"""
 if h.startswith(b'001円332円'):
 return 'rgb'

tests.append(test_rgb)

def test_pbm(h, f):
 """PBM (portable bitmap)"""
 if len(h) >= 3 and \
 h[0] == ord(b'P') and h[1] in b'14' and h[2] in b' \t\n\r':
 return 'pbm'

tests.append(test_pbm)

def test_pgm(h, f):
 """PGM (portable graymap)"""
 if len(h) >= 3 and \
 h[0] == ord(b'P') and h[1] in b'25' and h[2] in b' \t\n\r':
 return 'pgm'

tests.append(test_pgm)

def test_ppm(h, f):
 """PPM (portable pixmap)"""
 if len(h) >= 3 and \
 h[0] == ord(b'P') and h[1] in b'36' and h[2] in b' \t\n\r':
 return 'ppm'

tests.append(test_ppm)

def test_rast(h, f):
 """Sun raster file"""
 if h.startswith(b'\x59\xA6\x6A\x95'):
 return 'rast'

tests.append(test_rast)

def test_xbm(h, f):
 """X bitmap (X10 or X11)"""
 if h.startswith(b'#define '):
 return 'xbm'

tests.append(test_xbm)

def test_bmp(h, f):
 if h.startswith(b'BM'):
 return 'bmp'

tests.append(test_bmp)

def test_webp(h, f):
 if h.startswith(b'RIFF') and h[8:12] == b'WEBP':
 return 'webp'

tests.append(test_webp)

def test_exr(h, f):
 if h.startswith(b'\x76\x2f\x31\x01'):
 return 'exr'

tests.append(test_exr)

#--------------------#
# Small test program #
#--------------------#

def test():
 import sys
 recursive = 0
 if sys.argv[1:] and sys.argv[1] == '-r':
 del sys.argv[1:2]
 recursive = 1
 try:
 if sys.argv[1:]:
 testall(sys.argv[1:], recursive, 1)
 else:
 testall(['.'], recursive, 1)
 except KeyboardInterrupt:
 sys.stderr.write('\n[Interrupted]\n')
 sys.exit(1)

def testall(list, recursive, toplevel):
 import sys
 import os
 for filename in list:
 if os.path.isdir(filename):
 print(filename + '/:', end=' ')
 if recursive or toplevel:
 print('recursing down:')
 import glob
 names = glob.glob(os.path.join(glob.escape(filename), '*'))
 testall(names, recursive, 0)
 else:
 print('*** directory (use -r) ***')
 else:
 print(filename + ':', end=' ')
 sys.stdout.flush()
 try:
 print(what(filename))
 except OSError:
 print('*** not found ***')

if __name__ == '__main__':
 test()