"""
fitscheck is a command line script based on pyfits for verifying
and updating the CHECKSUM and DATASUM keywords of .fits files.
Fitscheck can also detect and often fix other FITS standards
violations.  fitscheck facilitates re-writing the non-standard
checksums originally generated by pyfits with standard checksums which
will interoperate with cfitsio.

fitscheck will refuse to write new checksums if the checksum keywords
are missing or their values are bad.  Use --force to write new
checksums regardless of whether or not they currently exist or pass.
Use --ignore-missing to tolerate missing checksum keywords without
comment.

Example uses of fitscheck:

1. Verify and update checksums, tolerating non-standard checksums, updating to
   standard checksum::

    $ fitscheck --checksum either --write *.fits

2. Write new checksums,  even if existing checksums are bad or missing::

    $ fitscheck --write --force *.fits

3. Verify standard checksums and FITS compliance without changing the files::

    $ fitscheck --compliance *.fits

4. Verify original nonstandard checksums only::

    $ fitscheck --checksum nonstandard *.fits

5. Only check and fix compliance problems,  ignoring checksums::

    $ fitscheck --checksum none --compliance --write *.fits

6. Verify standard interoperable checksums::

    $ fitscheck *.fits

7. Delete checksum keywords::

    $ fitscheck --checksum none --write *.fits
"""


import logging
import optparse
import sys
import textwrap
import warnings

import pyfits


log = logging.getLogger('fitscheck')


warnings.filterwarnings('error', message='Checksum verification failed')
warnings.filterwarnings('error', message='Datasum verification failed')
warnings.filterwarnings('ignore', message='Overwriting existing file')


def handle_options(args):
    if not len(args):
        args = ['-h']

    parser = optparse.OptionParser(usage=textwrap.dedent("""
        fitscheck [options] <.fits files...>

        .e.g. fitscheck example.fits

        Verifies and optionally re-writes the CHECKSUM and DATASUM keywords
        for a .fits file.
        Optionally detects and fixes FITS standard compliance problems.
        """.strip()))

    parser.add_option(
        '-k', '--checksum', dest='checksum_kind',
        type='choice', choices=['standard', 'nonstandard', 'either', 'none'],
        help='Choose FITS checksum mode or none.  Defaults standard.',
        default='standard', metavar='[standard | nonstandard | either | none]')

    parser.add_option(
        '-w', '--write', dest='write_file',
        help='Write out file checksums and/or FITS compliance fixes.',
        default=False, action='store_true')

    parser.add_option(
        '-f', '--force', dest='force',
        help='Do file update even if original checksum was bad.',
        default=False, action='store_true')

    parser.add_option(
        '-c', '--compliance', dest='compliance',
        help='Do FITS compliance checking; fix if possible.',
        default=False, action='store_true')

    parser.add_option(
        '-i', '--ignore-missing', dest='ignore_missing',
        help='Ignore missing checksums.',
        default=False, action='store_true')

    parser.add_option(
        '-v', '--verbose', dest='verbose', help='Generate extra output.',
        default=False, action='store_true')

    global OPTIONS
    OPTIONS, fits_files = parser.parse_args(args)

    if OPTIONS.checksum_kind == 'none':
        OPTIONS.checksum_kind = False

    return fits_files


def setup_logging():
    if OPTIONS.verbose:
        log.setLevel(logging.INFO)
    else:
        log.setLevel(logging.WARNING)

    handler = logging.StreamHandler()
    handler.setFormatter(logging.Formatter('%(message)s'))
    log.addHandler(handler)


def verify_checksums(filename):
    """
    Prints a message if any HDU in `filename` has a bad checksum or datasum.
    """

    errors = 0
    try:
        hdulist = pyfits.open(filename, checksum=OPTIONS.checksum_kind)
    except UserWarning as w:
        remainder = '.. ' + ' '.join(str(w).split(' ')[1:]).strip()
        # if "Checksum" in str(w) or "Datasum" in str(w):
        log.warn('BAD %r %s' % (filename, remainder))
        return 1
    if not OPTIONS.ignore_missing:
        for i, hdu in enumerate(hdulist):
            if not hdu._checksum:
                log.warn('MISSING %r .. Checksum not found in HDU #%d' %
                         (filename, i))
                return 1
            if not hdu._datasum:
                log.warn('MISSING %r .. Datasum not found in HDU #%d' %
                         (filename, i))
                return 1
    if not errors:
        log.info('OK %r' % filename)
    return errors


def verify_compliance(filename):
    """Check for FITS standard compliance."""

    hdulist = pyfits.open(filename)
    try:
        hdulist.verify('exception')
    except pyfits.VerifyError as e:
        log.warn('NONCOMPLIANT %r .. %s' %
                 (filename), str(e).replace('\n', ' '))
        return 1
    return 0


def update(filename):
    """
    Sets the ``CHECKSUM`` and ``DATASUM`` keywords for each HDU of `filename`.

    Also updates fixes standards violations if possible and requested.
    """

    hdulist = pyfits.open(filename)
    try:
        output_verify = 'silentfix' if OPTIONS.compliance else 'ignore'
        hdulist.writeto(filename, checksum=OPTIONS.checksum_kind, clobber=True,
                        output_verify=output_verify)
    except pyfits.VerifyError:
        pass  # unfixable errors already noted during verification phase
    finally:
        hdulist.close()


def process_file(filename):
    """
    Handle a single .fits file,  returning the count of checksum and compliance
    errors.
    """

    try:
        checksum_errors = verify_checksums(filename)
        if OPTIONS.compliance:
            compliance_errors = verify_compliance(filename)
        else:
            compliance_errors = 0
        if OPTIONS.write_file and checksum_errors == 0 or OPTIONS.force:
            update(filename)
        return checksum_errors + compliance_errors
    except Exception as e:
        log.error('EXCEPTION %r .. %s' % (filename, e))
        return 1


def main():
    """
    Processes command line parameters into options and files,  then checks
    or update FITS DATASUM and CHECKSUM keywords for the specified files.
    """

    errors = 0
    fits_files = handle_options(sys.argv[1:])
    setup_logging()
    for filename in fits_files:
        errors += process_file(filename)
    if errors:
        log.warn('%d errors' % errors)
    return int(bool(errors))
