feat: better structured internal

internal/config/parse_from_args.go

@@ -0,0 +1,35 @@
+package config
+
+import (
+	"flag"
+	"fmt"
+)
+
+// Extract the program configuration from the command-line arguments.
+func FromArgs() (*Config, error) {
+	// Parse flags.
+	verbose := flag.Bool("v", false, "Verbosity. If set, the program will print logs.")
+	explanation := flag.Bool("x", false, "Explanation. Whether or not to show all reduction steps.")
+	flag.Parse()
+
+	// Parse non-flag arguments.
+	if flag.NArg() == 0 {
+		return nil, fmt.Errorf("No input given.")
+	} else if flag.NArg() > 1 {
+		return nil, fmt.Errorf("More than 1 command-line argument.")
+	}
+
+	// Parse source type.
+	var source Source
+	if flag.Arg(0) == "-" {
+		source = StdinSource{}
+	} else {
+		source = StringSource{data: flag.Arg(0)}
+	}
+
+	return &Config{
+		Source:      source,
+		Verbose:     *verbose,
+		Explanation: *explanation,
+	}, nil
+}