feat: better structured internal

internal/config/config.go

@@ -0,0 +1,11 @@
+package config
+
+// Arguments given to program.
+type Config struct {
+	// The source code given to the program.
+	Source Source
+	// Whether or not to print debug logs.
+	Verbose bool
+	// Whether or not to print an explanation of the reduction.
+	Explanation bool
+}

internal/config/get_logger.go

@@ -0,0 +1,22 @@
+package config
+
+import (
+	"log/slog"
+	"os"
+)
+
+// Define the correct logger for the program to use.
+func (this Config) GetLogger() *slog.Logger {
+	var level slog.Level
+	if this.Verbose {
+		level = slog.LevelInfo
+	} else {
+		level = slog.LevelError
+	}
+
+	return slog.New(
+		slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+			Level: level,
+		}),
+	)
+}

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
+}

internal/config/source.go

@@ -0,0 +1,29 @@
+package config
+
+import (
+	"io"
+	"os"
+)
+
+// Defines the consumption of different types of input sources.
+type Source interface {
+	// Get the data.
+	Pull() (string, error)
+}
+
+// A source coming from a string.
+type StringSource struct{ data string }
+
+func (this StringSource) Pull() (string, error) { return this.data, nil }
+
+// A source coming from standard input.
+type StdinSource struct{}
+
+func (this StdinSource) Pull() (string, error) {
+	data, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return "", err
+	}
+
+	return string(data), nil
+}