#!/usr/bin/python


import argparse
import json
import sys

import jsonpointer

parser = argparse.ArgumentParser(
    description='Resolve a JSON pointer on JSON files')

# Accept pointer as option, as file or as first positional argument
ptr_group = parser.add_mutually_exclusive_group()

ptr_group.add_argument('-f', '--pointer-file', type=argparse.FileType('r'),
                       help='File containing a JSON pointer expression')

ptr_group.add_argument('-p', '--pointer', type=str,
                       help='A JSON pointer expression')

parser.add_argument('POINTER', type=str, nargs='?',
                    help='A JSON pointer expression (if neither -f nor -p '
                         'is given)')

parser.add_argument('FILE', type=str, nargs='+',
                    help='Files for which the pointer should be resolved')
parser.add_argument('--indent', type=int, default=None,
                    help='Indent output by n spaces')
parser.add_argument('-v', '--version', action='version',
                    version='%(prog)s ' + jsonpointer.__version__)


def main():
    try:
        ok = resolve_files()
    except KeyboardInterrupt:
        sys.exit(1)

    if not ok:
        sys.exit(1)


def parse_pointer(args):
    """ Return the pointer and the list of files to resolve it on

    If the pointer is given via -f or -p, a POINTER positional argument is
    actually the first file. """
    files = args.FILE

    if args.pointer is not None or args.pointer_file is not None:
        if args.POINTER is not None:
            files = [args.POINTER] + files

        if args.pointer is not None:
            ptr = args.pointer
        else:
            ptr = args.pointer_file.read().strip()

    elif args.POINTER is not None:
        ptr = args.POINTER

    else:
        parser.error('a JSON pointer is required (POINTER, -p or -f)')

    # Catches e.g. `jsonpointer a.json b.json`, where the pointer was omitted
    # and the first file would otherwise be used as the pointer
    try:
        jsonpointer.JsonPointer(ptr)
    except jsonpointer.JsonPointerException as e:
        parser.error('invalid JSON pointer %r: %s' % (ptr, e))

    return ptr, files


def resolve_files():
    """ Resolve a JSON pointer on JSON files

    Returns False if the pointer could not be resolved on at least one
    file. """
    args = parser.parse_args()

    ptr, files = parse_pointer(args)
    ok = True

    for name in files:
        try:
            f = argparse.FileType('r')(name)
        except argparse.ArgumentTypeError as e:
            parser.error(str(e))

        doc = json.load(f)
        try:
            result = jsonpointer.resolve_pointer(doc, ptr)
            print(json.dumps(result, indent=args.indent))
        except jsonpointer.JsonPointerException as e:
            print('Could not resolve pointer: %s' % str(e), file=sys.stderr)
            ok = False

    return ok


if __name__ == "__main__":
    main()
