diff --git a/heudiconv/cli/run.py b/heudiconv/cli/run.py
index f6af3d1..8a38182 100644
--- a/heudiconv/cli/run.py
+++ b/heudiconv/cli/run.py
@@ -1,109 +1,15 @@
 #!/usr/bin/env python
 
+import logging
 import os
-import os.path as op
-from argparse import ArgumentParser
 import sys
+from argparse import ArgumentParser
 
-from .. import __version__, __packagename__
-from ..parser import get_study_sessions
-from ..utils import load_heuristic, anonymize_sid, treat_infofile, SeqInfo
-from ..convert import prep_conversion
-from ..bids import populate_bids_templates, tuneup_bids_json_files
-from ..queue import queue_conversion
+from .. import __version__
+from ..main import workflow
 
-import inspect
-import logging
 lgr = logging.getLogger(__name__)
 
-INIT_MSG = "Running {packname} version {version} latest {latest}".format
-
-
-def is_interactive():
-   """Return True if all in/outs are tty"""
-   # TODO: check on windows if hasattr check would work correctly and add value:
-   return sys.stdin.isatty() and sys.stdout.isatty() and sys.stderr.isatty()
-
-
-def setup_exceptionhook():
-    """
-    Overloads default sys.excepthook with our exceptionhook handler.
-
-    If interactive, our exceptionhook handler will invoke pdb.post_mortem;
-    if not interactive, then invokes default handler.
-    """
-    def _pdb_excepthook(type, value, tb):
-        if is_interactive():
-            import traceback
-            import pdb
-            traceback.print_exception(type, value, tb)
-            # print()
-            pdb.post_mortem(tb)
-        else:
-            lgr.warning(
-              "We cannot setup exception hook since not in interactive mode")
-
-    sys.excepthook = _pdb_excepthook
-
-
-def process_extra_commands(outdir, args):
-    """
-    Perform custom command instead of regular operations. Supported commands:
-    ['treat-json', 'ls', 'populate-templates']
-
-    Parameters
-    ----------
-    outdir : String
-        Output directory
-    args : Namespace
-        arguments
-    """
-    if args.command == 'treat-jsons':
-        for f in args.files:
-            treat_infofile(f)
-    elif args.command == 'ls':
-        ensure_heuristic_arg(args)
-        heuristic = load_heuristic(args.heuristic)
-        heuristic_ls = getattr(heuristic, 'ls', None)
-        for f in args.files:
-            study_sessions = get_study_sessions(
-                args.dicom_dir_template, [f], heuristic, outdir,
-                args.session, args.subjs, grouping=args.grouping)
-            print(f)
-            for study_session, sequences in study_sessions.items():
-                suf = ''
-                if heuristic_ls:
-                    suf += heuristic_ls(study_session, sequences)
-                print(
-                    "\t%s %d sequences%s"
-                    % (str(study_session), len(sequences), suf)
-                )
-    elif args.command == 'populate-templates':
-        ensure_heuristic_arg(args)
-        heuristic = load_heuristic(args.heuristic)
-        for f in args.files:
-            populate_bids_templates(f, getattr(heuristic, 'DEFAULT_FIELDS', {}))
-    elif args.command == 'sanitize-jsons':
-        tuneup_bids_json_files(args.files)
-    elif args.command == 'heuristics':
-        from ..utils import get_known_heuristics_with_descriptions
-        for name_desc in get_known_heuristics_with_descriptions().items():
-            print("- %s: %s" % name_desc)
-    elif args.command == 'heuristic-info':
-        ensure_heuristic_arg(args)
-        from ..utils import get_heuristic_description
-        print(get_heuristic_description(args.heuristic, full=True))
-    else:
-        raise ValueError("Unknown command %s", args.command)
-    return
-
-
-def ensure_heuristic_arg(args):
-    from ..utils import get_known_heuristic_names
-    if not args.heuristic:
-        raise ValueError("Specify heuristic using -f. Known are: %s"
-                         % ', '.join(get_known_heuristic_names()))
-
 
 def main(argv=None):
     parser = get_parser()
@@ -113,25 +19,9 @@ def main(argv=None):
         lgr.warning("Nothing to be done - displaying usage help")
         parser.print_help()
         sys.exit(1)
-    # To be done asap so anything random is deterministic
-    if args.random_seed is not None:
-        import random
-        random.seed(args.random_seed)
-        import numpy
-        numpy.random.seed(args.random_seed)
-    # Ensure only supported bids options are passed
-    if args.debug:
-        lgr.setLevel(logging.DEBUG)
-    # Should be possible but only with a single subject -- will be used to
-    # override subject deduced from the DICOMs
-    if args.files and args.subjs and len(args.subjs) > 1:
-        raise ValueError(
-            "Unable to processes multiple `--subjects` with files"
-        )
 
-    if args.debug:
-        setup_exceptionhook()
-    process_args(args)
+    kwargs = vars(args)
+    workflow(**kwargs)
 
 
 def get_parser():
@@ -140,238 +30,147 @@ def get_parser():
     parser = ArgumentParser(description=docstr)
     parser.add_argument('--version', action='version', version=__version__)
     group = parser.add_mutually_exclusive_group()
-    group.add_argument('-d', '--dicom_dir_template', dest='dicom_dir_template',
-                       help='location of dicomdir that can be indexed with '
-                       'subject id {subject} and session {session}. Tarballs '
-                       '(can be compressed) are supported in addition to '
-                       'directory. All matching tarballs for a subject are '
-                       'extracted and their content processed in a single '
-                       'pass. If multiple tarballs are found, each is '
-                       'assumed to be a separate session and the --ses '
-                       'argument is ignored. Note that you might need to '
-                       'surround the value with quotes to avoid {...} being '
-                       'considered by shell')
-    group.add_argument('--files', nargs='*',
-                       help='Files (tarballs, dicoms) or directories '
-                       'containing files to process. Cannot be provided if '
-                       'using --dicom_dir_template.')
-    parser.add_argument('-s', '--subjects', dest='subjs', type=str, nargs='*',
-                        help='list of subjects - required for dicom template. '
-                        'If not provided, DICOMS would first be "sorted" and '
-                        'subject IDs deduced by the heuristic')
-    parser.add_argument('-c', '--converter',
-                        choices=('dcm2niix', 'none'), default='dcm2niix',
-                        help='tool to use for DICOM conversion. Setting to '
-                        '"none" disables the actual conversion step -- useful'
-                        'for testing heuristics.')
-    parser.add_argument('-o', '--outdir', default=os.getcwd(),
-                        help='output directory for conversion setup (for '
-                        'further customization and future reference. This '
-                        'directory will refer to non-anonymized subject IDs')
-    parser.add_argument('-l', '--locator', default=None,
-                        help='study path under outdir.  If provided, '
-                        'it overloads the value provided by the heuristic. '
-                        'If --datalad is enabled, every directory within '
-                        'locator becomes a super-dataset thus establishing a '
-                        'hierarchy. Setting to "unknown" will skip that dataset')
-    parser.add_argument('-a', '--conv-outdir', default=None,
-                        help='output directory for converted files. By default '
-                        'this is identical to --outdir. This option is most '
-                        'useful in combination with --anon-cmd')
-    parser.add_argument('--anon-cmd', default=None,
-                        help='command to run to convert subject IDs used for '
-                        'DICOMs to anonymized IDs. Such command must take a '
-                        'single argument and return a single anonymized ID. '
-                        'Also see --conv-outdir')
-    parser.add_argument('-f', '--heuristic', dest='heuristic',
-                        help='Name of a known heuristic or path to the Python'
-                             'script containing heuristic')
-    parser.add_argument('-p', '--with-prov', action='store_true',
-                        help='Store additional provenance information. '
-                        'Requires python-rdflib.')
-    parser.add_argument('-ss', '--ses', dest='session', default=None,
-                        help='session for longitudinal study_sessions, default '
-                        'is none')
-    parser.add_argument('-b', '--bids', nargs='*',
-                        metavar=('BIDSOPTION1', 'BIDSOPTION2'),
-                        choices=['notop'],
-                        dest='bids_options',
-                        help='flag for output into BIDS structure. Can also '
-                        'take bids specific options, e.g., --bids notop.'
-                        'The only currently supported options is'
-                        '"notop", which skips creation of top-level bids '
-                        'files. This is useful when running in batch mode to '
-                        'prevent possible race conditions.')
-    parser.add_argument('--overwrite', action='store_true', default=False,
-                        help='flag to allow overwriting existing converted files')
-    parser.add_argument('--datalad', action='store_true',
-                        help='Store the entire collection as DataLad '
-                        'dataset(s). Small files will be committed directly to '
-                        'git, while large to annex. New version (6) of annex '
-                        'repositories will be used in a "thin" mode so it '
-                        'would look to mortals as just any other regular '
-                        'directory (i.e. no symlinks to under .git/annex).  '
-                        'For now just for BIDS mode.')
-    parser.add_argument('--dbg', action='store_true', dest='debug',
-                        help='Do not catch exceptions and show exception '
-                        'traceback')
-    parser.add_argument('--command',
-                        choices=(
-                            'heuristics', 'heuristic-info',
-                            'ls', 'populate-templates',
-                            'sanitize-jsons', 'treat-jsons',
-                        ),
-                        help='custom actions to be performed on provided '
-                        'files instead of regular operation.')
-    parser.add_argument('-g', '--grouping', default='studyUID',
-                        choices=('studyUID', 'accession_number', 'all', 'custom'),
-                        help='How to group dicoms (default: by studyUID)')
-    parser.add_argument('--minmeta', action='store_true',
-                        help='Exclude dcmstack meta information in sidecar '
-                        'jsons')
-    parser.add_argument('--random-seed', type=int, default=None,
-                        help='Random seed to initialize RNG')
-    parser.add_argument('--dcmconfig', default=None,
-                        help='JSON file for additional dcm2niix configuration')
+    group.add_argument(
+        '-d', '--dicom_dir_template',
+        dest='dicom_dir_template',
+        help='Location of dicomdir that can be indexed with subject id '
+             '{subject} and session {session}. Tarballs (can be compressed) '
+             'are supported in addition to directory. All matching tarballs '
+             'for a subject are extracted and their content processed in a '
+             'single pass. If multiple tarballs are found, each is assumed to '
+             'be a separate session and the --ses argument is ignored. Note '
+             'that you might need to surround the value with quotes to avoid '
+             '{...} being considered by shell')
+    group.add_argument(
+        '--files',
+        nargs='*',
+        help='Files (tarballs, dicoms) or directories containing files to '
+             'process. Cannot be provided if using --dicom_dir_template.')
+    parser.add_argument(
+        '-s', '--subjects',
+        dest='subjs',
+        type=str,
+        nargs='*',
+        help='List of subjects - required for dicom template. If not '
+             'provided, DICOMS would first be "sorted" and subject IDs '
+             'deduced by the heuristic.')
+    parser.add_argument(
+        '-c', '--converter',
+        choices=('dcm2niix', 'none'),
+        default='dcm2niix',
+        help='Tool to use for DICOM conversion. Setting to "none" disables '
+             'the actual conversion step -- useful for testing heuristics.')
+    parser.add_argument(
+        '-o', '--outdir',
+        default=os.getcwd(),
+        help='Output directory for conversion setup (for further '
+             'customization and future reference. This directory will refer '
+             'to non-anonymized subject IDs.')
+    parser.add_argument(
+        '-l', '--locator',
+        default=None,
+        help='Study path under outdir. If provided, it overloads the value '
+             'provided by the heuristic. If --datalad is enabled, every '
+             'directory within locator becomes a super-dataset thus '
+             'establishing a hierarchy. Setting to "unknown" will skip that '
+             'dataset.')
+    parser.add_argument(
+        '-a', '--conv-outdir',
+        default=None,
+        help='Output directory for converted files. By default this is '
+             'identical to --outdir. This option is most useful in '
+             'combination with --anon-cmd.')
+    parser.add_argument(
+        '--anon-cmd',
+        default=None,
+        help='Command to run to convert subject IDs used for DICOMs to '
+             'anonymized IDs. Such command must take a single argument and '
+             'return a single anonymized ID. Also see --conv-outdir.')
+    parser.add_argument(
+        '-f', '--heuristic',
+        dest='heuristic',
+        help='Name of a known heuristic or path to the Python script '
+             'containing heuristic.')
+    parser.add_argument(
+        '-p', '--with-prov',
+        action='store_true',
+        help='Store additional provenance information. Requires python-rdflib.')
+    parser.add_argument(
+        '-ss', '--ses',
+        dest='session',
+        default=None,
+        help='Session for longitudinal study_sessions. Default is None.')
+    parser.add_argument(
+        '-b', '--bids',
+        nargs='*',
+        metavar=('BIDSOPTION1', 'BIDSOPTION2'),
+        choices=['notop'],
+        dest='bids_options',
+        help='Flag for output into BIDS structure. Can also take BIDS-'
+             'specific options, e.g., --bids notop. The only currently '
+             'supported options is "notop", which skips creation of '
+             'top-level BIDS files. This is useful when running in batch '
+             'mode to prevent possible race conditions.')
+    parser.add_argument(
+        '--overwrite',
+        action='store_true',
+        default=False,
+        help='Overwrite existing converted files.')
+    parser.add_argument(
+        '--datalad',
+        action='store_true',
+        help='Store the entire collection as DataLad dataset(s). Small files '
+             'will be committed directly to git, while large to annex. New '
+             'version (6) of annex repositories will be used in a "thin" '
+             'mode so it would look to mortals as just any other regular '
+             'directory (i.e. no symlinks to under .git/annex). For now just '
+             'for BIDS mode.')
+    parser.add_argument(
+        '--dbg',
+        action='store_true',
+        dest='debug',
+        help='Do not catch exceptions and show exception traceback.')
+    parser.add_argument(
+        '--command',
+        choices=(
+            'heuristics', 'heuristic-info',
+            'ls', 'populate-templates',
+            'sanitize-jsons', 'treat-jsons',
+        ),
+        help='Custom action to be performed on provided files instead of '
+             'regular operation.')
+    parser.add_argument(
+        '-g', '--grouping',
+        default='studyUID',
+        choices=('studyUID', 'accession_number', 'all', 'custom'),
+        help='How to group dicoms (default: by studyUID).')
+    parser.add_argument(
+        '--minmeta',
+        action='store_true',
+        help='Exclude dcmstack meta information in sidecar jsons.')
+    parser.add_argument(
+        '--random-seed',
+        type=int,
+        default=None,
+        help='Random seed to initialize RNG.')
+    parser.add_argument(
+        '--dcmconfig',
+        default=None,
+        help='JSON file for additional dcm2niix configuration.')
     submission = parser.add_argument_group('Conversion submission options')
-    submission.add_argument('-q', '--queue', choices=("SLURM", None),
-                            default=None,
-                            help='batch system to submit jobs in parallel')
-    submission.add_argument('--queue-args', dest='queue_args', default=None,
-                            help='Additional queue arguments passed as '
-                            'single string of Argument=Value pairs space '
-                            'separated.')
+    submission.add_argument(
+        '-q', '--queue',
+        choices=("SLURM", None),
+        default=None,
+        help='Batch system to submit jobs in parallel.')
+    submission.add_argument(
+        '--queue-args',
+        dest='queue_args',
+        default=None,
+        help='Additional queue arguments passed as a single string of '
+             'space-separated Argument=Value pairs.')
     return parser
 
 
-def process_args(args):
-    """Given a structure of arguments from the parser perform computation"""
-
-    # Deal with provided files or templates
-    # pre-process provided list of files and possibly sort into groups/sessions
-    # Group files per each study/sid/session
-
-    outdir = op.abspath(args.outdir)
-
-    try:
-        import etelemetry
-        latest = etelemetry.get_project("nipy/heudiconv")
-    except Exception as e:
-        lgr.warning("Could not check for version updates: %s", str(e))
-        latest = {"version": 'Unknown'}
-
-    lgr.info(INIT_MSG(packname=__packagename__,
-                      version=__version__,
-                      latest=latest["version"]))
-
-    if args.command:
-        process_extra_commands(outdir, args)
-        return
-    #
-    # Load heuristic -- better do it asap to make sure it loads correctly
-    #
-    if not args.heuristic:
-        raise RuntimeError("No heuristic specified - add to arguments and rerun")
-
-    if args.queue:
-        lgr.info("Queuing %s conversion", args.queue)
-        iterarg, iterables = ("files", len(args.files)) if args.files else \
-                             ("subjects", len(args.subjs))
-        queue_conversion(args.queue, iterarg, iterables, args.queue_args)
-        sys.exit(0)
-
-    heuristic = load_heuristic(args.heuristic)
-
-    study_sessions = get_study_sessions(args.dicom_dir_template, args.files,
-                                        heuristic, outdir, args.session,
-                                        args.subjs, grouping=args.grouping)
-
-    # extract tarballs, and replace their entries with expanded lists of files
-    # TODO: we might need to sort so sessions are ordered???
-    lgr.info("Need to process %d study sessions", len(study_sessions))
-
-    # processed_studydirs = set()
-
-    for (locator, session, sid), files_or_seqinfo in study_sessions.items():
-
-        # Allow for session to be overloaded from command line
-        if args.session is not None:
-            session = args.session
-        if args.locator is not None:
-            locator = args.locator
-        if not len(files_or_seqinfo):
-            raise ValueError("nothing to process?")
-        # that is how life is ATM :-/ since we don't do sorting if subj
-        # template is provided
-        if isinstance(files_or_seqinfo, dict):
-            assert(isinstance(list(files_or_seqinfo.keys())[0], SeqInfo))
-            dicoms = None
-            seqinfo = files_or_seqinfo
-        else:
-            dicoms = files_or_seqinfo
-            seqinfo = None
-
-        if locator == 'unknown':
-            lgr.warning("Skipping unknown locator dataset")
-            continue
-
-        anon_sid = anonymize_sid(sid, args.anon_cmd) if args.anon_cmd else None
-        if args.anon_cmd:
-            lgr.info('Anonymized {} to {}'.format(sid, anon_sid))
-
-        study_outdir = op.join(outdir, locator or '')
-        anon_outdir = args.conv_outdir or outdir
-        anon_study_outdir = op.join(anon_outdir, locator or '')
-
-        # TODO: --datalad  cmdline option, which would take care about initiating
-        # the outdir -> study_outdir datasets if not yet there
-        if args.datalad:
-            from ..external.dlad import prepare_datalad
-            dlad_sid = sid if not anon_sid else anon_sid
-            dl_msg = prepare_datalad(anon_study_outdir, anon_outdir, dlad_sid,
-                                     session, seqinfo, dicoms,
-                                     args.bids_options)
-
-        lgr.info("PROCESSING STARTS: {0}".format(
-            str(dict(subject=sid, outdir=study_outdir, session=session))))
-
-        prep_conversion(sid,
-                        dicoms,
-                        study_outdir,
-                        heuristic,
-                        converter=args.converter,
-                        anon_sid=anon_sid,
-                        anon_outdir=anon_study_outdir,
-                        with_prov=args.with_prov,
-                        ses=session,
-                        bids_options=args.bids_options,
-                        seqinfo=seqinfo,
-                        min_meta=args.minmeta,
-                        overwrite=args.overwrite,
-                        dcmconfig=args.dcmconfig,
-                        grouping=args.grouping,)
-
-        lgr.info("PROCESSING DONE: {0}".format(
-            str(dict(subject=sid, outdir=study_outdir, session=session))))
-
-        if args.datalad:
-            from ..external.dlad import add_to_datalad
-            msg = "Converted subject %s" % dl_msg
-            # TODO:  whenever propagate to supers work -- do just
-            # ds.save(msg=msg)
-            #  also in batch mode might fail since we have no locking ATM
-            #  and theoretically no need actually to save entire study
-            #  we just need that
-            add_to_datalad(outdir, study_outdir, msg, args.bids_options)
-
-    # if args.bids:
-    #     # Let's populate BIDS templates for folks to take care about
-    #     for study_outdir in processed_studydirs:
-    #         populate_bids_templates(study_outdir)
-    #
-    # TODO: record_collection of the sid/session although that information
-    # is pretty much present in .heudiconv/SUBJECT/info so we could just poke there
-
-
 if __name__ == "__main__":
     main()
diff --git a/heudiconv/main.py b/heudiconv/main.py
new file mode 100644
index 0000000..56401de
--- /dev/null
+++ b/heudiconv/main.py
@@ -0,0 +1,365 @@
+import logging
+import os.path as op
+import sys
+
+from . import __version__, __packagename__
+from .bids import populate_bids_templates, tuneup_bids_json_files
+from .convert import prep_conversion
+from .parser import get_study_sessions
+from .queue import queue_conversion
+from .utils import anonymize_sid, load_heuristic, treat_infofile, SeqInfo
+
+lgr = logging.getLogger(__name__)
+
+
+INIT_MSG = "Running {packname} version {version} latest {latest}".format
+
+
+def is_interactive():
+    """Return True if all in/outs are tty"""
+    # TODO: check on windows if hasattr check would work correctly and add value:
+    return sys.stdin.isatty() and sys.stdout.isatty() and sys.stderr.isatty()
+
+
+def setup_exceptionhook():
+    """
+    Overloads default sys.excepthook with our exceptionhook handler.
+
+    If interactive, our exceptionhook handler will invoke pdb.post_mortem;
+    if not interactive, then invokes default handler.
+    """
+    def _pdb_excepthook(type, value, tb):
+        if is_interactive():
+            import traceback
+            import pdb
+            traceback.print_exception(type, value, tb)
+            # print()
+            pdb.post_mortem(tb)
+        else:
+            lgr.warning(
+              "We cannot setup exception hook since not in interactive mode")
+
+    sys.excepthook = _pdb_excepthook
+
+
+def process_extra_commands(outdir, command, files, dicom_dir_template,
+                           heuristic, session, subjs, grouping):
+    """
+    Perform custom command instead of regular operations. Supported commands:
+    ['treat-json', 'ls', 'populate-templates']
+
+    Parameters
+    ----------
+    outdir : str
+        Output directory
+    command : {'treat-json', 'ls', 'populate-templates'}
+        Heudiconv command to run
+    files : list of str
+        List of files
+    dicom_dir_template : str
+        Location of dicomdir that can be indexed with subject id
+        {subject} and session {session}. Tarballs (can be compressed)
+        are supported in addition to directory. All matching tarballs
+        for a subject are extracted and their content processed in a
+        single pass. If multiple tarballs are found, each is assumed to
+        be a separate session and the 'session' argument is ignored.
+    heuristic : str
+        Path to heuristic file or name of builtin heuristic.
+    session : str
+        Session identifier
+    subjs : list of str
+        List of subject identifiers
+    grouping : {'studyUID', 'accession_number', 'all', 'custom'}
+        How to group dicoms.
+    """
+    if command == 'treat-jsons':
+        for f in files:
+            treat_infofile(f)
+    elif command == 'ls':
+        ensure_heuristic_arg(heuristic)
+        heuristic = load_heuristic(heuristic)
+        heuristic_ls = getattr(heuristic, 'ls', None)
+        for f in files:
+            study_sessions = get_study_sessions(
+                dicom_dir_template, [f], heuristic, outdir,
+                session, subjs, grouping=grouping)
+            print(f)
+            for study_session, sequences in study_sessions.items():
+                suf = ''
+                if heuristic_ls:
+                    suf += heuristic_ls(study_session, sequences)
+                print(
+                    "\t%s %d sequences%s"
+                    % (str(study_session), len(sequences), suf)
+                )
+    elif command == 'populate-templates':
+        ensure_heuristic_arg(heuristic)
+        heuristic = load_heuristic(heuristic)
+        for f in files:
+            populate_bids_templates(f, getattr(heuristic, 'DEFAULT_FIELDS', {}))
+    elif command == 'sanitize-jsons':
+        tuneup_bids_json_files(files)
+    elif command == 'heuristics':
+        from .utils import get_known_heuristics_with_descriptions
+        for name_desc in get_known_heuristics_with_descriptions().items():
+            print("- %s: %s" % name_desc)
+    elif command == 'heuristic-info':
+        ensure_heuristic_arg(heuristic)
+        from .utils import get_heuristic_description
+        print(get_heuristic_description(heuristic, full=True))
+    else:
+        raise ValueError("Unknown command %s" % command)
+    return
+
+
+def ensure_heuristic_arg(heuristic=None):
+    """
+    Check that the heuristic argument was provided.
+    """
+    from .utils import get_known_heuristic_names
+    if not heuristic:
+        raise ValueError("Specify heuristic using -f. Known are: %s"
+                         % ', '.join(get_known_heuristic_names()))
+
+
+def workflow(*, dicom_dir_template=None, files=None, subjs=None,
+             converter='dcm2niix', outdir='.', locator=None, conv_outdir=None,
+             anon_cmd=None, heuristic=None, with_prov=False, session=None,
+             bids_options=None, overwrite=False, datalad=False, debug=False,
+             command=None, grouping='studyUID', minmeta=False,
+             random_seed=None, dcmconfig=None, queue=None, queue_args=None):
+    """Run the HeuDiConv conversion workflow.
+
+    Parameters
+    ----------
+    dicom_dir_template : str or None, optional
+        Location of dicomdir that can be indexed with subject id
+        {subject} and session {session}. Tarballs (can be compressed)
+        are supported in addition to directory. All matching tarballs
+        for a subject are extracted and their content processed in a
+        single pass. If multiple tarballs are found, each is assumed to
+        be a separate session and the 'session' argument is ignored.
+        Mutually exclusive with 'files'. Default is None.
+    files : list or None, optional
+        Files (tarballs, dicoms) or directories containing files to
+        process. Mutually exclusive with 'dicom_dir_template'. Default is None.
+    subjs : list or None, optional
+        List of subjects - required for dicom template. If not
+        provided, DICOMS would first be "sorted" and subject IDs
+        deduced by the heuristic. Default is None.
+    converter : {'dcm2niix', None}, optional
+        Tool to use for DICOM conversion. Setting to None disables
+        the actual conversion step -- useful for testing heuristics.
+        Default is None.
+    outdir : str, optional
+        Output directory for conversion setup (for further
+        customization and future reference. This directory will refer
+        to non-anonymized subject IDs.
+        Default is '.' (current working directory).
+    locator : str or 'unknown' or None, optional
+        Study path under outdir. If provided, it overloads the value
+        provided by the heuristic. If 'datalad=True', every
+        directory within locator becomes a super-dataset thus
+        establishing a hierarchy. Setting to "unknown" will skip that
+        dataset. Default is None.
+    conv_outdir : str or None, optional
+        Output directory for converted files. By default this is
+        identical to --outdir. This option is most useful in
+        combination with 'anon_cmd'. Default is None.
+    anon_cmd : str or None, optional
+        Command to run to convert subject IDs used for DICOMs to
+        anonymized IDs. Such command must take a single argument and
+        return a single anonymized ID. Also see 'conv_outdir'. Default is None.
+    heuristic : str or None, optional
+        Name of a known heuristic or path to the Python script containing
+        heuristic. Default is None.
+    with_prov : bool, optional
+        Store additional provenance information. Requires python-rdflib.
+        Default is False.
+    session : str or None, optional
+        Session for longitudinal study_sessions. Default is None.
+    bids_options : str or None, optional
+        Flag for output into BIDS structure. Can also take BIDS-
+        specific options, e.g., --bids notop. The only currently
+        supported options is "notop", which skips creation of
+        top-level BIDS files. This is useful when running in batch
+        mode to prevent possible race conditions. Default is None.
+    overwrite : bool, optional
+        Overwrite existing converted files. Default is False.
+    datalad : bool, optional
+        Store the entire collection as DataLad dataset(s). Small files
+        will be committed directly to git, while large to annex. New
+        version (6) of annex repositories will be used in a "thin"
+        mode so it would look to mortals as just any other regular
+        directory (i.e. no symlinks to under .git/annex). For now just
+        for BIDS mode. Default is False.
+    debug : bool, optional
+        Do not catch exceptions and show exception traceback. Default is False.
+    command : {'heuristics', 'heuristic-info', 'ls', 'populate-templates',
+               'sanitize-jsons', 'treat-jsons', None}, optional
+        Custom action to be performed on provided files instead of regular
+        operation. Default is None.
+    grouping : {'studyUID', 'accession_number', 'all', 'custom'}, optional
+        How to group dicoms. Default is 'studyUID'.
+    minmeta : bool, optional
+        Exclude dcmstack meta information in sidecar jsons. Default is False.
+    random_seed : int or None, optional
+        Random seed to initialize RNG. Default is None.
+    dcmconfig : str or None, optional
+        JSON file for additional dcm2niix configuration. Default is None.
+    queue : {'SLURM', None}, optional
+        Batch system to submit jobs in parallel. Default is None.
+        If set, will cause scheduling of conversion and return without performing
+        any further action.
+    queue_args : str or None, optional
+        Additional queue arguments passed as single string of space-separated
+        Argument=Value pairs. Default is None.
+
+    Notes
+    -----
+    All parameters in this function must be called as keyword arguments.
+    """
+
+    # To be done asap so anything random is deterministic
+    if random_seed is not None:
+        import random
+        random.seed(random_seed)
+        import numpy
+        numpy.random.seed(random_seed)
+    # Ensure only supported bids options are passed
+    if debug:
+        lgr.setLevel(logging.DEBUG)
+    # Should be possible but only with a single subject -- will be used to
+    # override subject deduced from the DICOMs
+    if files and subjs and len(subjs) > 1:
+        raise ValueError(
+            "Unable to processes multiple `--subjects` with files"
+        )
+
+    if debug:
+        setup_exceptionhook()
+
+    # Deal with provided files or templates
+    # pre-process provided list of files and possibly sort into groups/sessions
+    # Group files per each study/sid/session
+
+    outdir = op.abspath(outdir)
+
+    try:
+        import etelemetry
+        latest = etelemetry.get_project("nipy/heudiconv")
+    except Exception as e:
+        lgr.warning("Could not check for version updates: %s", str(e))
+        latest = {"version": 'Unknown'}
+
+    lgr.info(INIT_MSG(packname=__packagename__,
+                      version=__version__,
+                      latest=latest["version"]))
+
+    if command:
+        process_extra_commands(outdir, command, files, dicom_dir_template,
+                               heuristic, session, subjs, grouping)
+        return
+    #
+    # Load heuristic -- better do it asap to make sure it loads correctly
+    #
+    if not heuristic:
+        raise RuntimeError("No heuristic specified - add to arguments and rerun")
+
+    if queue:
+        lgr.info("Queuing %s conversion", queue)
+        iterarg, iterables = ("files", len(files)) if files else \
+                             ("subjects", len(subjs))
+        queue_conversion(queue, iterarg, iterables, queue_args)
+        return
+
+    heuristic = load_heuristic(heuristic)
+
+    study_sessions = get_study_sessions(dicom_dir_template, files,
+                                        heuristic, outdir, session,
+                                        subjs, grouping=grouping)
+
+    # extract tarballs, and replace their entries with expanded lists of files
+    # TODO: we might need to sort so sessions are ordered???
+    lgr.info("Need to process %d study sessions", len(study_sessions))
+
+    # processed_studydirs = set()
+
+    locator_manual, session_manual = locator, session
+    for (locator, session, sid), files_or_seqinfo in study_sessions.items():
+
+        # Allow for session to be overloaded from command line
+        if session_manual is not None:
+            session = session_manual
+        if locator_manual is not None:
+            locator = locator_manual
+        if not len(files_or_seqinfo):
+            raise ValueError("nothing to process?")
+        # that is how life is ATM :-/ since we don't do sorting if subj
+        # template is provided
+        if isinstance(files_or_seqinfo, dict):
+            assert(isinstance(list(files_or_seqinfo.keys())[0], SeqInfo))
+            dicoms = None
+            seqinfo = files_or_seqinfo
+        else:
+            dicoms = files_or_seqinfo
+            seqinfo = None
+
+        if locator == 'unknown':
+            lgr.warning("Skipping unknown locator dataset")
+            continue
+
+        anon_sid = anonymize_sid(sid, anon_cmd) if anon_cmd else None
+        if anon_cmd:
+            lgr.info('Anonymized {} to {}'.format(sid, anon_sid))
+
+        study_outdir = op.join(outdir, locator or '')
+        anon_outdir = conv_outdir or outdir
+        anon_study_outdir = op.join(anon_outdir, locator or '')
+
+        if datalad:
+            from .external.dlad import prepare_datalad
+            dlad_sid = sid if not anon_sid else anon_sid
+            dl_msg = prepare_datalad(anon_study_outdir, anon_outdir, dlad_sid,
+                                     session, seqinfo, dicoms,
+                                     bids_options)
+
+        lgr.info("PROCESSING STARTS: {0}".format(
+            str(dict(subject=sid, outdir=study_outdir, session=session))))
+
+        prep_conversion(sid,
+                        dicoms,
+                        study_outdir,
+                        heuristic,
+                        converter=converter,
+                        anon_sid=anon_sid,
+                        anon_outdir=anon_study_outdir,
+                        with_prov=with_prov,
+                        ses=session,
+                        bids_options=bids_options,
+                        seqinfo=seqinfo,
+                        min_meta=minmeta,
+                        overwrite=overwrite,
+                        dcmconfig=dcmconfig,
+                        grouping=grouping,)
+
+        lgr.info("PROCESSING DONE: {0}".format(
+            str(dict(subject=sid, outdir=study_outdir, session=session))))
+
+        if datalad:
+            from .external.dlad import add_to_datalad
+            msg = "Converted subject %s" % dl_msg
+            # TODO:  whenever propagate to supers work -- do just
+            # ds.save(msg=msg)
+            #  also in batch mode might fail since we have no locking ATM
+            #  and theoretically no need actually to save entire study
+            #  we just need that
+            add_to_datalad(outdir, study_outdir, msg, bids_options)
+
+    # if bids:
+    #     # Let's populate BIDS templates for folks to take care about
+    #     for study_outdir in processed_studydirs:
+    #         populate_bids_templates(study_outdir)
+    #
+    # TODO: record_collection of the sid/session although that information
+    # is pretty much present in .heudiconv/SUBJECT/info so we could just poke there

Make main workflow callable from Python
<!-- DO NOT DELETE THIS! 
This template is used to facilitate issue resolution.
All text in <!-> tags will not be displayed.
-->

### Summary
<!-- If you are having conversion troubles, please share as much
relevant information as possible. This includes, but is not limited to:
- log of conversion
- heuristic
-->
Currently, heudiconv's main workflow is included in the same function that parses the CLI arguments. With a little refactoring, we could separate these two a bit to allow users to call heudiconv from within Python. I think it would be fairly easy, and it would help users like me who prefer to call heudiconv within larger Python scripts.

This is somewhat related to [this NeuroStars post](https://neurostars.org/t/is-there-any-way-to-use-dcm2bids-or-neudiconv-with-python/4949) (specifically point 2).
diff --git a/heudiconv/tests/test_main.py b/heudiconv/tests/test_main.py
index 9129137..0274f99 100644
--- a/heudiconv/tests/test_main.py
+++ b/heudiconv/tests/test_main.py
@@ -1,9 +1,7 @@
 # TODO: break this up by modules
 
-from heudiconv.cli.run import (
-    main as runner,
-    process_args,
-)
+from heudiconv.cli.run import main as runner
+from heudiconv.main import workflow
 from heudiconv import __version__
 from heudiconv.utils import (create_file_if_missing,
                              set_readonly,
@@ -288,12 +286,7 @@ def test_cache(tmpdir):
 
 def test_no_etelemetry():
     # smoke test at large - just verifying that no crash if no etelemetry
-    class args:
-        outdir = '/dev/null'
-        command = 'ls'
-        heuristic = 'reproin'
-        files = []  # Nothing to list
-
     # must not fail if etelemetry no found
     with patch.dict('sys.modules', {'etelemetry': None}):
-        process_args(args)
+        workflow(outdir='/dev/null', command='ls',
+                 heuristic='reproin', files=[])

pip install -e .[all]
parse_log_pytest
requirements.txt
pytest pytest-cov pytest-xdist pytest-mock pytest-asyncio
apt-get update apt-get install -y gcc
3.8
requirements.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
annexremote==1.6.6
backports.tarfile==1.2.0
boto3==1.37.23
botocore==1.37.23
certifi==2025.1.31
cffi==1.17.1
chardet==5.2.0
charset-normalizer==3.4.1
ci-info==0.3.0
click==8.1.8
coverage==7.6.1
cryptography==44.0.2
datalad==1.1.3
dcmstack==0.9.0
distro==1.9.0
etelemetry==0.3.1
exceptiongroup==1.2.2
execnet==2.1.1
fasteners==0.19
filelock==3.16.1
-e git+https://github.com/nipy/heudiconv.git@a1a7cb594c5c0584868593c4516cccf4700689df#egg=heudiconv
humanize==4.10.0
idna==3.10
importlib_metadata==8.5.0
importlib_resources==6.4.5
iniconfig==2.1.0
inotify==0.2.10
iso8601==2.1.0
isodate==0.6.1
jaraco.classes==3.4.0
jaraco.context==6.0.1
jaraco.functools==4.1.0
jeepney==0.9.0
jmespath==1.0.1
keyring==25.5.0
keyrings.alt==5.0.2
looseversion==1.3.0
lxml==5.3.1
mock==5.2.0
more-itertools==10.5.0
msgpack==1.1.0
networkx==3.1
nibabel==5.2.1
nipype==1.8.6
nose==1.3.7
numpy==1.24.4
packaging==24.2
pathlib==1.0.1
patool==1.12
platformdirs==4.3.6
pluggy==1.5.0
prov==2.0.1
pycparser==2.22
pydicom==2.4.4
pydot==3.0.4
pylibjpeg-libjpeg==2.2.0
pyparsing==3.1.4
pytest==8.3.5
pytest-asyncio==0.24.0
pytest-cov==5.0.0
pytest-mock==3.14.0
pytest-xdist==3.6.1
python-dateutil==2.9.0.post0
python-gitlab==4.13.0
rdflib==6.3.2
requests==2.32.3
requests-toolbelt==1.0.0
s3transfer==0.11.4
scipy==1.10.1
SecretStorage==3.3.3
simplejson==3.20.1
six==1.17.0
swebench_matterhorn @ file:///swebench_matterhorn
tinydb==4.8.2
tomli==2.2.1
tqdm==4.67.1
traits==6.3.2
typing_extensions==4.13.0
urllib3==1.26.20
zipp==3.20.2

name: heudiconv
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=3.0.16=h5eee18b_0
  - pip=24.2=py38h06a4308_0
  - python=3.8.20=he870216_0
  - readline=8.2=h5eee18b_0
  - setuptools=75.1.0=py38h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.44.0=py38h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - annexremote==1.6.6
      - backports-tarfile==1.2.0
      - boto3==1.37.23
      - botocore==1.37.23
      - certifi==2025.1.31
      - cffi==1.17.1
      - chardet==5.2.0
      - charset-normalizer==3.4.1
      - ci-info==0.3.0
      - click==8.1.8
      - coverage==7.6.1
      - cryptography==44.0.2
      - datalad==1.1.3
      - dcmstack==0.9.0
      - distro==1.9.0
      - etelemetry==0.3.1
      - exceptiongroup==1.2.2
      - execnet==2.1.1
      - fasteners==0.19
      - filelock==3.16.1
      - humanize==4.10.0
      - idna==3.10
      - importlib-metadata==8.5.0
      - importlib-resources==6.4.5
      - iniconfig==2.1.0
      - inotify==0.2.10
      - iso8601==2.1.0
      - isodate==0.6.1
      - jaraco-classes==3.4.0
      - jaraco-context==6.0.1
      - jaraco-functools==4.1.0
      - jeepney==0.9.0
      - jmespath==1.0.1
      - keyring==25.5.0
      - keyrings-alt==5.0.2
      - looseversion==1.3.0
      - lxml==5.3.1
      - mock==5.2.0
      - more-itertools==10.5.0
      - msgpack==1.1.0
      - networkx==3.1
      - nibabel==5.2.1
      - nipype==1.8.6
      - nose==1.3.7
      - numpy==1.24.4
      - packaging==24.2
      - pathlib==1.0.1
      - patool==1.12
      - platformdirs==4.3.6
      - pluggy==1.5.0
      - prov==2.0.1
      - pycparser==2.22
      - pydicom==2.4.4
      - pydot==3.0.4
      - pylibjpeg-libjpeg==2.2.0
      - pyparsing==3.1.4
      - pytest==8.3.5
      - pytest-asyncio==0.24.0
      - pytest-cov==5.0.0
      - pytest-mock==3.14.0
      - pytest-xdist==3.6.1
      - python-dateutil==2.9.0.post0
      - python-gitlab==4.13.0
      - rdflib==6.3.2
      - requests==2.32.3
      - requests-toolbelt==1.0.0
      - s3transfer==0.11.4
      - scipy==1.10.1
      - secretstorage==3.3.3
      - simplejson==3.20.1
      - six==1.17.0
      - swebench-matterhorn==0.0.0
      - tinydb==4.8.2
      - tomli==2.2.1
      - tqdm==4.67.1
      - traits==6.3.2
      - typing-extensions==4.13.0
      - urllib3==1.26.20
      - zipp==3.20.2
prefix: /opt/conda/envs/heudiconv

heudiconv/tests/test_main.py::test_main_help heudiconv/tests/test_main.py::test_main_version heudiconv/tests/test_main.py::test_create_file_if_missing heudiconv/tests/test_main.py::test_populate_bids_templates heudiconv/tests/test_main.py::test_add_participant_record heudiconv/tests/test_main.py::test_get_formatted_scans_key_row heudiconv/tests/test_main.py::test_add_rows_to_scans_keys_file heudiconv/tests/test_main.py::test__find_subj_ses heudiconv/tests/test_main.py::test_make_readonly heudiconv/tests/test_main.py::test_no_etelemetry
heudiconv/tests/test_main.py::test_prepare_for_datalad heudiconv/tests/test_main.py::test_cache
heudiconv/cli/run.py heudiconv/main.py
heudiconv/cli/run.py heudiconv/main.py