From 7173bee935bed9ab4d7e52d1386f32ff64ad7b72 Mon Sep 17 00:00:00 2001
From: Jake Howard <git@theorangeone.net>
Date: Wed, 29 Mar 2017 18:43:35 +0100
Subject: [PATCH] Allow validation

---
 md_pdf/cli.py             |  2 ++
 md_pdf/config/validate.py | 19 +++++++++++++++++++
 md_pdf/exceptions.py      |  4 ++++
 3 files changed, 25 insertions(+)

diff --git a/md_pdf/cli.py b/md_pdf/cli.py
index a34d545..bf10bed 100644
--- a/md_pdf/cli.py
+++ b/md_pdf/cli.py
@@ -3,6 +3,7 @@ from md_pdf.args import parse_args
 from md_pdf.exceptions import PrematureExit
 from md_pdf.build import build
 from md_pdf.config.read import load_config
+from md_pdf.config.validate import validate_config
 
 
 FORMAT = "[%(levelname)s]: %(message)s"
@@ -13,6 +14,7 @@ def cli():
     args = parse_args()
     try:
         config = load_config()
+        validate_config(config)
         build(args, config)
     except PrematureExit:
         return 0
diff --git a/md_pdf/config/validate.py b/md_pdf/config/validate.py
index e69de29..f01e83c 100644
--- a/md_pdf/config/validate.py
+++ b/md_pdf/config/validate.py
@@ -0,0 +1,19 @@
+from md_pdf.exceptions import ConfigValidationException
+
+
+REQUIRED_KEYS = [
+    'output',
+    'input'
+]
+
+
+def check_required_keys(config):
+    missing_keys = [key for key in REQUIRED_KEYS if key not in config]
+    if missing_keys:
+        raise ConfigValidationException("Missing required keys: {}".format(missing_keys))
+
+
+def validate_config(config):
+    check_required_keys(config)
+
+
diff --git a/md_pdf/exceptions.py b/md_pdf/exceptions.py
index abc8e8e..c608b52 100644
--- a/md_pdf/exceptions.py
+++ b/md_pdf/exceptions.py
@@ -1,2 +1,6 @@
 class PrematureExit(Exception):
     pass
+
+
+class ConfigValidationException(Exception):
+    pass