"""

combine_batch_outputs.py

Merges two or more .json files in MD output format, optionally
writing the results to another .json file.

* Concatenates image lists, erroring if images are not unique.
* Errors if class lists are conflicting; errors on unrecognized fields.
* Checks compatibility in info structs, within reason.

File format:

https://github.com/agentmorris/MegaDetector/tree/main/megadetector/api/batch_processing#batch-processing-api-output-format

Command-line use:

combine_batch_outputs input1.json input2.json ... inputN.json output.json

This does no checking for redundancy; if you are looking to ensemble
the results of multiple model versions, see merge_detections.py.

"""

#%% Constants and imports

import argparse
import sys
import json
from megadetector.utils import ct_utils


#%% Merge functions

def combine_batch_output_files(input_files,
                               output_file=None,
                               require_uniqueness=True,
                               verbose=True):
    """
    Merges the list of MD results files [input_files] into a single
    dictionary, optionally writing the result to [output_file].

    Always overwrites [output_file] if it exists.

    Args:
        input_files (list of str): paths to JSON detection files
        output_file (str, optional): path to write merged JSON
        require_uniqueness (bool, optional): whether to require that the images in
            each list of images be unique
        verbose (bool, optional): enable additional debug output

    Returns:
        dict: merged dictionaries loaded from [input_files], identical to what's
        written to [output_file] if [output_file] is not None
    """

    def print_if_verbose(s):
        if verbose:
            print(s)

    input_dicts = []
    for fn in input_files:
        print_if_verbose('Loading results from {}'.format(fn))
        with open(fn, 'r', encoding='utf-8') as f:
            input_dicts.append(json.load(f))

    print_if_verbose('Merging results')
    merged_dict = combine_batch_output_dictionaries(
        input_dicts, require_uniqueness=require_uniqueness)

    print_if_verbose('Writing output to {}'.format(output_file))
    if output_file is not None:
        ct_utils.write_json(output_file, merged_dict)

    return merged_dict


def combine_batch_output_dictionaries(input_dicts, require_uniqueness=True):
    """
    Merges the list of MD results dictionaries [input_dicts] into a single dict.
    See module header comment for details on merge rules.

    Args:
        input_dicts (list of dicts): list of dicts in which each dict represents the
            contents of a MD output file
        require_uniqueness (bool, optional): whether to require that the images in
            each input dict be unique; if this is True and image filenames are
            not unique, an error is raised.

    Returns:
        dict: merged MD results
    """

    # Map image filenames to detections, we'll convert to a list later
    images = {}
    info = {}
    detection_categories = {}
    classification_categories = {}
    n_redundant_images = 0
    n_images = 0

    known_fields = ['info', 'detection_categories', 'classification_categories',
                    'images']

    for input_dict in input_dicts:

        for k in input_dict:
            if k not in known_fields:
                print(f'Warning: unrecognized batch output field: {k}')

        # Check compatibility of detection categories
        for cat_id in input_dict['detection_categories']:
            cat_name = input_dict['detection_categories'][cat_id]
            if cat_id in detection_categories:
                assert detection_categories[cat_id] == cat_name, (
                    'Detection category mismatch')
            else:
                detection_categories[cat_id] = cat_name

        # Check compatibility of classification categories
        if 'classification_categories' in input_dict:
            for cat_id in input_dict['classification_categories']:
                cat_name = input_dict['classification_categories'][cat_id]
                if cat_id in classification_categories:
                    assert classification_categories[cat_id] == cat_name, (
                        'Classification category mismatch')
                else:
                    classification_categories[cat_id] = cat_name

        # Merge image lists, checking uniqueness
        for im in input_dict['images']:
            # Normalize path separators so we don't treat images as different if they
            # were processed on different OS's
            im['file'] = im['file'].replace('\\','/')
            im_file = im['file']
            if require_uniqueness:
                assert im_file not in images, f'Duplicate image: {im_file}'
                images[im_file] = im
                n_images += 1
            else:
                if im_file in images:
                    n_redundant_images += 1
                    previous_im = images[im_file]
                    # Replace a previous failure with a success
                    if ('detections' in im) and ('detections' not in previous_im):
                        images[im_file] = im
                        print(f'Replacing previous failure for image: {im_file}')
                else:
                    images[im_file] = im
                    n_images += 1

        # Merge info dicts, don't check completion time fields
        if len(info) == 0:
            info = input_dict['info']
        else:
            info_compare = input_dict['info']
            assert info_compare['detector'] == info['detector'], (
                'Incompatible detection versions in merging')
            assert info_compare['format_version'] == info['format_version'], (
                'Incompatible batch output versions in merging')
            if 'classifier' in info_compare:
                if 'classifier' in info:
                    assert info['classifier'] == info_compare['classifier']
                else:
                    info['classifier'] = info_compare['classifier']

    # ...for each dictionary

    if n_redundant_images > 0:
        print(f'Warning: found {n_redundant_images} redundant images '
              f'(out of {n_images} total) during merge')

    # Convert merged image dictionaries to a sorted list
    sorted_images = sorted(images.values(), key=lambda im: im['file'])

    merged_dict = {'info': info,
                   'detection_categories': detection_categories,
                   'classification_categories': classification_categories,
                   'images': sorted_images}
    return merged_dict

# ...combine_batch_output_files()


def combine_api_shard_files(input_files, output_file=None):
    """
    Merges the list of .json-formatted API shard files [input_files] into a single
    list of dictionaries, optionally writing the result to [output_file].

    This operates on mostly-deprecated API shard files, not MegaDetector results files.
    If you don't know what an API shard file is, you don't want this function.

    Args:
        input_files (list of str): files to merge
        output_file (str, optional): file to which we should write merged results

    Returns:
        dict: merged results

    :meta private:
    """

    input_lists = []
    print('Loading input files')
    for fn in input_files:
        input_lists.append(json.load(open(fn)))

    detections = []
    # detection_list = input_lists[0]
    for detection_list in input_lists:
        assert isinstance(detection_list, list)
        # d = detection_list[0]
        for d in detection_list:
            assert 'file' in d
            assert 'max_detection_conf' in d
            assert 'detections' in d
            detections.extend([d])

    print('Writing output')
    if output_file is not None:
        ct_utils.write_json(output_file, detections)

    return detections

# ...combine_api_shard_files()


#%% Command-line driver

def main(): # noqa

    parser = argparse.ArgumentParser()
    parser.add_argument(
        'input_paths', nargs='+',
        help='List of input .json files')
    parser.add_argument(
        'output_path',
        help='Output .json file')

    if len(sys.argv[1:]) == 0:
        parser.print_help()
        parser.exit()

    args = parser.parse_args()
    combine_batch_output_files(args.input_paths, args.output_path)

if __name__ == '__main__':
    main()
