From efffb7474d695fc09f94e8aabcf54f160146b9a8 Mon Sep 17 00:00:00 2001
From: Aaron LI <aaronly.me@outlook.com>
Date: Mon, 3 Oct 2016 20:34:33 +0800
Subject: Add custom configuration checkers.

These additional checker functions validate the required configs whether
provided by the user config file, as well as against necessary contexts.
---
 fg21sim/configs/__init__.py |  1 +
 fg21sim/configs/validate.py | 94 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 fg21sim/configs/validate.py

diff --git a/fg21sim/configs/__init__.py b/fg21sim/configs/__init__.py
index b1fe70f..bbfbbd7 100644
--- a/fg21sim/configs/__init__.py
+++ b/fg21sim/configs/__init__.py
@@ -2,5 +2,6 @@
 # MIT license
 
 from .manager import ConfigManager
+from .validate import validate_configs
 
 configs = ConfigManager()
diff --git a/fg21sim/configs/validate.py b/fg21sim/configs/validate.py
new file mode 100644
index 0000000..b9accdf
--- /dev/null
+++ b/fg21sim/configs/validate.py
@@ -0,0 +1,94 @@
+# Copyright (c) 2016 Weitian LI <liweitianux@live.com>
+# MIT license
+
+"""
+Custom validations for the configurations.
+"""
+
+from ..errors import ConfigError
+
+
+def _check_missing(configs, keys):
+    """Check whether the mandatory config is provided by the user."""
+    if isinstance(keys, str):
+        keys = [keys, ]
+    for key in keys:
+        if not configs.getn(key):
+            raise ConfigError('config "%s" missing' % key)
+    return True
+
+
+def check_common(configs):
+    """Check the "[common]" section of the configurations."""
+    _check_missing(configs, "common/data_dir")
+    return True
+
+
+def check_frequency(configs):
+    """Check the "[frequency]" section of the configurations."""
+    if configs.getn("frequency/type") == "custom":
+        _check_missing(configs, "frequency/frequencies")
+    elif configs.getn("frequency/type") == "calc":
+        _check_missing(configs, ["frequency/start",
+                                 "frequency/stop",
+                                 "frequency/step"])
+    return True
+
+
+def check_output(configs):
+    """Check the "[output]" section of the configurations."""
+    if configs.getn("output/combine"):
+        _check_missing(configs, "output/output_dir")
+    return True
+
+
+def check_galactic_synchrotron(configs):
+    """Check the "[galactic][synchrotron]" section of the configurations."""
+    _check_missing(configs, ["galactic/synchrotron/template",
+                             "galactic/synchrotron/template_freq",
+                             "galactic/synchrotron/template_unit",
+                             "galactic/synchrotron/indexmap"])
+    if configs.getn("galactic/synchrotron/save"):
+        _check_missing(configs, "galactic/synchrotron/output_dir")
+    return True
+
+
+# Available checkers to validate the configurations
+_CHECKERS = [
+    check_common,
+    check_frequency,
+    check_output,
+    check_galactic_synchrotron,
+]
+
+
+def validate_configs(configs, checkers=_CHECKERS):
+    """Validate the configurations through the supplied checkers.
+
+    These checker usually validate on the global scale, and validate
+    some specific configs against their contexts.
+
+    Parameters
+    ----------
+    configs : `ConfigManager` object
+        An `ConfigManager` object contains both default and user
+        configurations.
+    checkers : list of functions
+        List of checker functions through which the configurations
+        will be validated.
+
+    Returns
+    -------
+    bool
+        True if the configurations pass all checker functions, otherwise,
+        the `ConfigError` will be raised with corresponding message.
+
+    Raises
+    ------
+    ConfigError
+        If any configuration failed the check, a `ConfigError` with
+        details will be raised.
+    """
+    for checker in checkers:
+        checker(configs)
+    return True
-- 
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