Fixing ext_to_int and int_to_ext implementations and adding tests.

src/loadcase.rs

@@ -3,10 +3,13 @@ use anyhow::Result;
 use casecsv::read::{read_dir, read_zip};
 use std::path::PathBuf;
 
-pub fn load_case_file(case_path: &PathBuf) -> Result<MPC> {
+pub fn load_case(case_path: &PathBuf) -> Result<MPC> {
     let is_case = match case_path.extension() {
         None => false,
-        Some(os_str) => os_str.to_str() == Some("case"),
+        Some(os_str) => match os_str.to_str() {
+            Some("case") | Some("zip") => true,
+            _ => false,
+        },
     };
 
     let (case, bus, gen, branch, _gencost, _dcline) = if is_case {

src/mpc.rs

@@ -1,9 +1,7 @@
 use crate::order::Order;
-use casecsv::*;
+use casecsv::{Branch, Bus, Gen};
 use sparsetools::csr::CSR;
 
-/// MPC is a MATPOWER case that models a power system as a directed graph
-/// structure.
 #[derive(Clone, Default)]
 pub struct MPC {
     /// System MVA base used for converting power into per-unit quantities.