package cli

import (
	"flag"
	"fmt"
)

// Arguments given to program.
type Options struct {
	// The source code given to the program.
	Input string
	// Whether or not to print debug logs.
	Verbose bool
	// Whether or not to print an explanation of the reduction.
	Explanation bool
}

// Extract the program configuration from the command-line arguments.
func ParseOptions() (*Options, 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.")
	}

	return &Options{
		Input:       flag.Arg(0),
		Verbose:     *verbose,
		Explanation: *explanation,
	}, nil
}