import argparse
import sys
import json
import jsonschema
import jsonschema.validators
from jsonschema.exceptions import SchemaError, ValidationError
from referencing import Registry, Resource
from referencing.jsonschema import DRAFT202012

parser = argparse.ArgumentParser(
    description="Validate a JSON document against a JSON schema"
)
parser.add_argument("-f", "--file",
                    help="file containing the JSON document to validate. " +
                    "If absent, the JSON document is read from the standard input")
parser.add_argument("-s", "--schema", required=True, 
                    help="file containing the schema definition"
                    )
parser.add_argument("-r", "--resource", nargs="+", default=[],
                    help="additional schemas to be added to the registry for reference resolution")

if __name__ == "__main__":
    args = parser.parse_args()
    # Load the schema and any additional resources and add them to the registry for reference resolution
    # The schema is last in the list: it will remain stored in schema_dict at the end of the for loop
    registry = Registry()
    for schema_file in (*args.resource, args.schema):
        with open(file=schema_file, mode="r") as f:
            schema = json.load(f)
        resource = Resource.from_contents(
            contents=schema,
            default_specification=DRAFT202012
        )
        registry = resource @ registry
    # Load the JSON document to validate
    with open(file=args.file, mode="r") if args.file else sys.stdin as f:
        document = json.load(f)
    # Set the validator with the desired schema and check the schema itself before validating the document
    validator = jsonschema.validators.validator_for(schema)(schema, registry=registry)
    try:
        validator.check_schema(schema)
    except SchemaError as e:
        print("Schema check failed.")
        print(f"{e.message}")
        exit(1)
    # Validate the document
    try:
        validator.validate(document)
        print("Valid!")
    except ValidationError as e:
        print("Validation failed.")
        print(f"{e.message}")
        exit(1)