Add input validation to shodan convert command

shodan/__main__.py

@@ -37,6 +37,7 @@
 import requests
 import time
 import json
+from shodan.cli.validation import check_input_file_type
 
 # The file converters that are used to go from .json.gz to various other formats
 from shodan.cli.converter import CsvConverter, KmlConverter, GeoJsonConverter, ExcelConverter, ImagesConverter
@@ -93,7 +94,7 @@ def main():
 
 @main.command()
 @click.option('--fields', help='List of properties to output.', default=None)
-@click.argument('input', metavar='<input file>', type=click.Path(exists=True))
+@click.argument('input', metavar='<input file>', type=click.Path(exists=True), callback=check_input_file_type)
 @click.argument('format', metavar='<output format>', type=click.Choice(CONVERTERS.keys()))
 def convert(fields, input, format):
     """Convert the given input data file into a different format. The following file formats are supported:

shodan/cli/validation.py

@@ -0,0 +1,15 @@
+import click
+
+
+def check_input_file_type(ctx, param, value):
+    """
+    Click callback method used for file type input validation.
+    :param ctx: Python Click library Context object.
+    :param param: Python Click Context object params attribute.
+    :param value: Value passed in for a given command line parameter.
+    """
+    idx = value.find(".")
+
+    if idx == -1 or value[idx:] != ".json.gz":
+        raise click.BadParameter("Input file type must be '.json.gz'")
+    return value