1 files changed, 97 insertions, 0 deletions
diff --git a/src/options.cpp b/src/options.cpp
new file mode 100644
index 0000000..a52a0bc
--- /dev/null
+++ b/src/options.cpp
@@ -0,0 +1,97 @@
+#include <string>
+#include <iostream>
+
+#include "options.hpp"
+
+void print_usage(const std::string & invocation)
+{
+  std::cerr << "Usage:" << std::endl;
+  std::cerr << invocation << " " << usage_args << std::endl;
+}
+
+void print_help(const std::string & invocation)
+{
+  print_usage(invocation);
+  std::cerr << "FIXME: Write help." << std::endl;
+}
+
+int parse_opts(int argc, char ** argv, Options & opts)
+{
+  std::string invocation(argv[0]);
+  
+  for (int i = 1; i < argc; ++i)
+  {
+    std::string arg(argv[i]);
+
+    if (arg == std::string("-h") || arg == std::string("--help"))
+    {
+      print_help(invocation);
+      return 2;
+    }
+
+    else if (arg == std::string("-l") || arg == std::string("--laplacian"))
+    {
+      if (i+1 < argc && argv[i+1][0] != '-')
+        opts.infile = std::string(argv[++i]);
+      else
+      {
+        std::cerr << "Missing argument to --laplacian." << std::endl;
+        print_usage(invocation);
+        return 1;
+      }
+    }
+
+    else if (arg == std::string("--vals"))
+    {
+       if (i+1 < argc && argv[i+1][0] != '-')
+        opts.outfile_vals = std::string(argv[++i]);
+      else
+      {
+        std::cerr << "Missing argument to --vals." << std::endl;
+        print_usage(invocation);
+        return 1;
+      }
+    }
+
+    else if (arg == std::string("--vecs"))
+    {
+       if (i+1 < argc && argv[i+1][0] != '-')
+        opts.outfile_vecs = std::string(argv[++i]);
+      else
+      {
+        std::cerr << "Missing argument to --vecs." << std::endl;
+        print_usage(invocation);
+        return 1;
+      }
+    }
+
+    else
+    {
+      std::cout << "The argument \"" << arg << "\" will be dealt with by PETSc/SLEPc if they understand it. Otherwise it will be silently ignored." << std::endl;
+    }
+  }
+
+  // Begin options validation. 
+  if (opts.infile.empty())
+  {
+    std::cerr << "Missing Laplacian file." << std::endl;
+    print_usage(invocation);
+    return 1;
+  }
+   
+  if (opts.outfile_vecs.empty())
+  {
+    std::cerr << "Missing output eigenvectors file." << std::endl;
+    print_usage(invocation);
+    return 1;
+  }
+  if (opts.outfile_vals.empty())
+  {
+    std::cerr << "Missing output eigenvalues file." << std::endl;
+    print_usage(invocation);
+    return 1;
+  }
+  // End validation.
+  
+  return 0;
+}