Add validator for existing input files

src/config/validate.rs

@@ -3,6 +3,8 @@ use std::vec::Vec;
 
 pub type ValidationResult = Result<(), String>;
 
+use config::read;
+
 
 fn check_required_keys(config: &Value) -> ValidationResult {
     for key in vec!(
@@ -11,7 +13,17 @@ fn check_required_keys(config: &Value) -> ValidationResult {
         "title"
     ).iter() {
         if config.get(key).is_none() {
-            return Err("Missing key".into());
+            return Err(format!("Missing required key {}.", key));
+        }
+    }
+    return Ok(());
+}
+
+fn check_input_files(config: &Value) -> ValidationResult {
+    let files = read::get_input_files(config);
+    for file in files.iter() {
+        if !file.exists() || !file.is_file() {
+            return Err(format!("Cannot find input file at {}.", file.as_path().display()));
         }
     }
     return Ok(());
@@ -31,6 +43,7 @@ pub fn unwrap_group(config: &Value, funcs: Vec<&Fn(&Value) -> ValidationResult>)
 
 pub fn validate(config: &Value) -> ValidationResult {
     return unwrap_group(config, vec!(
-        &check_required_keys
+        &check_required_keys,
+        &check_input_files
     ));
 }