feat: some basic commands

cmd/lambda/lambda.go

@@ -1,55 +1,94 @@
 package main
 
 import (
+	"fmt"
 	"os"
 
-	"git.maximhutz.com/max/lambda/internal/cli"
 	"git.maximhutz.com/max/lambda/internal/config"
+	"github.com/spf13/cobra"
 )
 
-func main() {
-	// Parse CLI arguments.
-	options, err := config.FromArgs()
-	cli.HandleError(err)
+func Lambda() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "lambda",
+		Short: "Lambda calculus interpreter",
+		Long:  "A lambda calculus interpreter supporting multiple representations.",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			// Legacy behavior when no subcommand is given.
+			options, err := config.FromArgs()
+			if err != nil {
+				return err
+			}
 
-	logger := options.GetLogger()
-	logger.Info("using program arguments", "args", os.Args)
-	logger.Info("parsed CLI options", "options", options)
+			logger := options.GetLogger()
+			logger.Info("using program arguments", "args", os.Args)
+			logger.Info("parsed CLI options", "options", options)
 
-	r := GetRegistry()
+			r := GetRegistry()
 
-	// Get input.
-	input, err := options.Source.Extract()
-	cli.HandleError(err)
+			// Get input.
+			input, err := options.Source.Extract()
+			if err != nil {
+				return err
+			}
 
-	// Parse code into syntax tree.
-	repr, err := r.Unmarshal(input, "saccharine")
-	cli.HandleError(err)
-	logger.Info("parsed syntax tree", "tree", repr)
+			// Parse code into syntax tree.
+			repr, err := r.Unmarshal(input, "saccharine")
+			if err != nil {
+				return err
+			}
+			logger.Info("parsed syntax tree", "tree", repr)
 
-	// Compile expression to lambda calculus.
-	compiled, err := r.ConvertTo(repr, "lambda")
-	cli.HandleError(err)
-	logger.Info("compiled λ expression", "tree", compiled)
+			// Compile expression to lambda calculus.
+			compiled, err := r.ConvertTo(repr, "lambda")
+			if err != nil {
+				return err
+			}
+			logger.Info("compiled λ expression", "tree", compiled)
 
-	// Create reducer with the compiled expression.
-	engine, err := r.GetDefaultEngine("lambda")
-	cli.HandleError(err)
+			// Create reducer with the compiled expression.
+			engine, err := r.GetDefaultEngine("lambda")
+			if err != nil {
+				return err
+			}
 
-	process := engine.Load()
-	err = process.Set(compiled)
-	cli.HandleError(err)
-	// Run reduction.
-	for process.Step(1) {
+			process := engine.Load()
+			err = process.Set(compiled)
+			if err != nil {
+				return err
+			}
+
+			// Run reduction.
+			for process.Step(1) {
+			}
+
+			// Return the final reduced result.
+			result, err := process.Get()
+			if err != nil {
+				return err
+			}
+
+			output, err := r.Marshal(result)
+			if err != nil {
+				return err
+			}
+
+			return options.Destination.Write(output)
+		},
 	}
 
-	// Return the final reduced result.
-	result, err := process.Get()
-	cli.HandleError(err)
+	cmd.PersistentFlags().BoolP("verbose", "v", false, "Enable verbose output")
 
-	output, err := r.Marshal(result)
-	cli.HandleError(err)
+	cmd.AddCommand(LambdaConvert())
+	cmd.AddCommand(LambdaEngine())
 
-	err = options.Destination.Write(output)
-	cli.HandleError(err)
+	return cmd
+}
+
+func main() {
+	lambda := Lambda()
+	if err := lambda.Execute(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 }

cmd/lambda/lambda_convert.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"git.maximhutz.com/max/lambda/internal/cli"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+// inferReprFromPath returns the repr type based on file extension.
+func inferReprFromPath(path string) (string, error) {
+	switch ext := strings.ToLower(filepath.Ext(path)); ext {
+	case ".lam", ".lambda":
+		return "lambda", nil
+	case ".sac", ".saccharine":
+		return "saccharine", nil
+	default:
+		return "", fmt.Errorf("unknown file extension '%s'", ext)
+	}
+}
+
+func LambdaConvert() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "convert <input> <output>",
+		Short: "Convert between lambda calculus representations",
+		Args:  cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			inputPath := args[0]
+			outputPath := args[1]
+
+			// Infer repr types from extensions.
+			inputRepr, err := inferReprFromPath(inputPath)
+			if err != nil {
+				return fmt.Errorf("input file: %w", err)
+			}
+
+			outputRepr, err := inferReprFromPath(outputPath)
+			if err != nil {
+				return fmt.Errorf("output file: %w", err)
+			}
+
+			// Read input file.
+			input, err := os.ReadFile(inputPath)
+			if err != nil {
+				return fmt.Errorf("reading input file: %w", err)
+			}
+
+			r := GetRegistry()
+
+			// Parse input into syntax tree.
+			repr, err := r.Unmarshal(string(input), inputRepr)
+			if err != nil {
+				return fmt.Errorf("parsing input: %w", err)
+			}
+
+			if viper.GetBool("verbose") {
+				fmt.Fprintf(os.Stderr, "Parsed %s from %s\n", inputRepr, inputPath)
+			}
+
+			// Convert to output repr if different.
+			var result cli.Repr
+			if inputRepr != outputRepr {
+				result, err = r.ConvertTo(repr, outputRepr)
+				if err != nil {
+					return fmt.Errorf("converting %s to %s: %w", inputRepr, outputRepr, err)
+				}
+
+				if viper.GetBool("verbose") {
+					fmt.Fprintf(os.Stderr, "Converted to %s\n", outputRepr)
+				}
+			} else {
+				result = repr
+			}
+
+			// Marshal output.
+			output, err := r.Marshal(result)
+			if err != nil {
+				return fmt.Errorf("marshaling output: %w", err)
+			}
+
+			// Write output file.
+			err = os.WriteFile(outputPath, []byte(output), 0644)
+			if err != nil {
+				return fmt.Errorf("writing output file: %w", err)
+			}
+
+			if viper.GetBool("verbose") {
+				fmt.Fprintf(os.Stderr, "Wrote %s to %s\n", outputRepr, outputPath)
+			}
+
+			return nil
+		},
+	}
+
+	return cmd
+}

cmd/lambda/lambda_engine.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"github.com/spf13/cobra"
+)
+
+func LambdaEngine() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "engine",
+		Short: "Information about available engines",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return cmd.Help()
+		},
+	}
+
+	cmd.AddCommand(LambdaEngineList())
+
+	return cmd
+}

cmd/lambda/lambda_engine_list.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+func LambdaEngineList() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:     "list",
+		Aliases: []string{"ls"},
+		Short:   "List available engines",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			r := GetRegistry()
+
+			for engine := range r.ListEngines() {
+				fmt.Println(engine.Name())
+			}
+
+			return nil
+		},
+	}
+
+	return cmd
+}