refactor: rewrite CLI and internal architecture (#41)

## Description

The old architecture used a monolithic `main()` with a custom arg parser, an event-emitter-based runtime, and a plugin system for optional features.
This PR rewrites the CLI and internal architecture to be modular, extensible, and built around a registry of interchangeable components.

- Replace custom CLI arg parsing with Cobra subcommands (`convert`, `reduce`, `engine list`).
- Introduce a registry system (`internal/registry`) for marshalers, codecs, and engines, with BFS-based conversion path resolution.
- Add type-erased adapter layer (`internal/cli`) with `Repr`, `Engine`, `Process`, `Marshaler`, and `Conversion` interfaces wrapping generic `pkg/` types.
- Replace the event-emitter-based `Runtime` with a simpler `Engine`/`Process` model (`pkg/engine`).
- Add generic `Codec[T, U]` and `Marshaler[T]` interfaces (`pkg/codec`).
- Merge `saccharine/token` sub-package into `saccharine` and rename scanner functions from `parse*` to `scan*`.
- Make saccharine-to-lambda conversion bidirectional (encode and decode).
- Add `lambda.Marshaler` and `saccharine.Marshaler` implementing `codec.Marshaler`.
- Remove old infrastructure: `pkg/runtime`, `pkg/expr`, `internal/plugins`, `internal/statistics`.
- Add `make lint` target and update golangci-lint config.

### Decisions

- Cobra was chosen for the CLI framework to support nested subcommands and standard flag handling.
- The registry uses BFS to find conversion paths between representations, allowing multi-hop conversions without hardcoding routes.
- Type erasure via `cli.Repr` (wrapping `any`) enables the registry to work with heterogeneous types while keeping `pkg/` generics type-safe.
- The old plugin/event system was removed entirely rather than adapted, since the new `Process` model can support hooks differently in the future.

## Benefits

- Subcommands make the CLI self-documenting and easier to extend with new functionality.
- The registry pattern decouples representations, conversions, and engines, making it trivial to add new ones.
- BFS conversion routing means adding a single codec automatically enables transitive conversions.
- Simpler `Engine`/`Process` model reduces complexity compared to the event-emitter runtime.
- Consolidating the `token` sub-package reduces import depth and package sprawl.

## Checklist

- [x] Code follows conventional commit format.
- [x] Branch follows naming convention (`<type>/<description>`). Always use underscores.
- [ ] Tests pass (if applicable).
- [ ] Documentation updated (if applicable).

Reviewed-on: #41
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
This commit was merged in pull request #41.
This commit is contained in:
2026-02-07 03:25:32 +00:00
committed by Maxim Hutz
parent f2c8d9f7d2
commit a3ee34732e
41 changed files with 1007 additions and 637 deletions

View File

@@ -3,65 +3,29 @@ package main
import (
"os"
"git.maximhutz.com/max/lambda/internal/cli"
"git.maximhutz.com/max/lambda/internal/config"
"git.maximhutz.com/max/lambda/internal/plugins"
"git.maximhutz.com/max/lambda/pkg/convert"
"git.maximhutz.com/max/lambda/pkg/normalorder"
"git.maximhutz.com/max/lambda/pkg/saccharine"
"github.com/spf13/cobra"
)
func main() {
// Parse CLI arguments.
options, err := config.FromArgs()
cli.HandleError(err)
logger := options.GetLogger()
logger.Info("using program arguments", "args", os.Args)
logger.Info("parsed CLI options", "options", options)
// Get input.
input, err := options.Source.Extract()
cli.HandleError(err)
// Parse code into syntax tree.
ast, err := saccharine.Parse(input)
cli.HandleError(err)
logger.Info("parsed syntax tree", "tree", ast)
// Compile expression to lambda calculus.
compiled := convert.SaccharineToLambda(ast)
logger.Info("compiled λ expression", "tree", compiled.String())
// Create reducer with the compiled expression.
runtime := normalorder.NewRuntime(compiled)
// If the user selected to track CPU performance, attach a profiler.
if options.Profile != "" {
plugins.NewPerformance(options.Profile, runtime)
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, _ []string) error {
return cmd.Help()
},
}
// If the user selected to produce a step-by-step explanation, attach an
// observer.
if options.Explanation {
plugins.NewExplanation(runtime)
}
cmd.AddCommand(LambdaConvert())
cmd.AddCommand(LambdaEngine())
cmd.AddCommand(LambdaReduce())
// If the user opted to track statistics, attach a tracker.
if options.Statistics {
plugins.NewStatistics(runtime)
}
// If the user selected for verbose debug logs, attach a reduction tracker.
if options.Verbose {
plugins.NewLogs(logger, runtime)
}
// Run reduction.
runtime.Run()
// Return the final reduced result.
result := runtime.Expression().String()
err = options.Destination.Write(result)
cli.HandleError(err)
return cmd
}
func main() {
lambda := Lambda()
if err := lambda.Execute(); err != nil {
os.Exit(1)
}
}

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@@ -0,0 +1,94 @@
package main
import (
"fmt"
"os"
"path/filepath"
"strings"
"github.com/spf13/cobra"
)
// inferReprFromPath returns the repr type based on file extension.
func inferReprFromPath(path string) (string, error) {
switch ext := strings.ToLower(filepath.Ext(path)); ext {
case ".lambda", ".lam", ".lc":
return "lambda", nil
case ".saccharine", ".sch":
return "saccharine", nil
default:
return "", fmt.Errorf("unknown file extension '%s'", ext)
}
}
func LambdaConvert() *cobra.Command {
var inputReprFlag, outputReprFlag string
cmd := &cobra.Command{
Use: "convert <input-file> <output-file>",
Short: "Convert between lambda calculus representations",
SilenceUsage: true,
RunE: func(cmd *cobra.Command, args []string) error {
if len(args) != 2 {
return cmd.Help()
}
var err error
inputPath, outputPath := args[0], args[1]
// Use flag if provided, otherwise infer from extension.
inputRepr := inputReprFlag
if inputRepr == "" {
if inputRepr, err = inferReprFromPath(inputPath); err != nil {
return fmt.Errorf("input file: %w", err)
}
}
outputRepr := outputReprFlag
if outputRepr == "" {
if outputRepr, err = inferReprFromPath(outputPath); 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)
}
// Convert to output repr if different.
result, err := r.ConvertTo(repr, outputRepr)
if err != nil {
return fmt.Errorf("converting %s to %s: %w", inputRepr, outputRepr, err)
}
// Marshal output.
output, err := r.Marshal(result)
if err != nil {
return fmt.Errorf("unmarshaling output: %w", err)
}
// Write output file.
err = os.WriteFile(outputPath, []byte(output), 0644)
if err != nil {
return fmt.Errorf("writing output file: %w", err)
}
return nil
},
}
cmd.Flags().StringVar(&inputReprFlag, "from", "", "Input representation (inferred from extension if unset)")
cmd.Flags().StringVar(&outputReprFlag, "to", "", "Output representation (inferred from extension if unset)")
return cmd
}

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@@ -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
}

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@@ -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
}

109
cmd/lambda/lambda_reduce.go Normal file
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@@ -0,0 +1,109 @@
package main
import (
"fmt"
"github.com/spf13/cobra"
"git.maximhutz.com/max/lambda/internal/cli"
"git.maximhutz.com/max/lambda/internal/config"
)
func LambdaReduce() *cobra.Command {
var inputReprFlag string
var engineFlag string
cmd := &cobra.Command{
Use: "reduce <input-file>",
Short: "Reduce a lambda calculus expression",
SilenceUsage: true,
Aliases: []string{"run"},
RunE: func(cmd *cobra.Command, args []string) error {
var err error
if len(args) != 1 {
return cmd.Help()
}
inputPath := args[0]
// Get input source.
var source config.Source
if inputPath == "-" {
source = config.StdinSource{}
} else {
source = config.FileSource{Path: inputPath}
}
destination := config.StdoutDestination{}
r := GetRegistry()
// Get input.
input, err := source.Extract()
if err != nil {
return err
}
// Use flag if provided, otherwise infer from extension.
inputRepr := inputReprFlag
if inputRepr == "" {
if inputRepr, err = inferReprFromPath(inputPath); err != nil {
return fmt.Errorf("input file: %w", err)
}
}
// Find engine.
var engine cli.Engine
if engineFlag == "" {
if engine, err = r.GetDefaultEngine(inputRepr); err != nil {
return err
}
} else {
if engine, err = r.GetEngine(engineFlag); err != nil {
return err
}
}
// Parse code into syntax tree.
repr, err := r.Unmarshal(input, inputRepr)
if err != nil {
return err
}
// Compile expression to lambda calculus.
compiled, err := r.ConvertTo(repr, "lambda")
if err != nil {
return err
}
// Create process.
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 destination.Write(output)
},
}
cmd.Flags().StringVar(&inputReprFlag, "from", "", "Input representation (inferred from extension if unset)")
cmd.Flags().StringVarP(&engineFlag, "engine", "e", "", "Reduction engine (inferred from '--input' if unset)")
return cmd
}

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@@ -1,85 +0,0 @@
package main
import (
"os"
"path/filepath"
"strings"
"testing"
"git.maximhutz.com/max/lambda/pkg/convert"
"git.maximhutz.com/max/lambda/pkg/normalorder"
"git.maximhutz.com/max/lambda/pkg/saccharine"
"github.com/stretchr/testify/assert"
)
// Helper function to run a single sample through the lambda runtime.
func runSample(samplePath string) (string, error) {
// Read the sample file.
input, err := os.ReadFile(samplePath)
if err != nil {
return "", err
}
// Parse code into syntax tree.
ast, err := saccharine.Parse(string(input))
if err != nil {
return "", err
}
// Compile expression to lambda calculus.
compiled := convert.SaccharineToLambda(ast)
// Create and run the reducer.
reducer := normalorder.NewRuntime(compiled)
reducer.Run()
return reducer.Expression().String() + "\n", nil
}
// Test that all samples produce expected output.
func TestSamplesValidity(t *testing.T) {
// Discover all .test files in the tests directory.
testFiles, err := filepath.Glob("../../tests/*.test")
assert.NoError(t, err, "Failed to read tests directory.")
assert.NotEmpty(t, testFiles, "No '*.test' files found in directory.")
for _, testPath := range testFiles {
// Build expected file path.
expectedPath := strings.TrimSuffix(testPath, filepath.Ext(testPath)) + ".expected"
name := strings.TrimSuffix(filepath.Base(testPath), filepath.Ext(testPath))
t.Run(name, func(t *testing.T) {
// Run the sample and capture output.
actual, err := runSample(testPath)
assert.NoError(t, err, "Failed to run sample.")
// Read expected output.
expectedBytes, err := os.ReadFile(expectedPath)
assert.NoError(t, err, "Failed to read expected output.")
expected := string(expectedBytes)
// Compare outputs.
assert.Equal(t, expected, actual, "Output does not match expected.")
})
}
}
// Benchmark all samples using sub-benchmarks.
func BenchmarkSamples(b *testing.B) {
// Discover all .test files in the tests directory.
testFiles, err := filepath.Glob("../../tests/*.test")
assert.NoError(b, err, "Failed to read tests directory.")
assert.NotEmpty(b, testFiles, "No '*.test' files found in directory.")
for _, path := range testFiles {
name := strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
b.Run(name, func(b *testing.B) {
for b.Loop() {
_, err := runSample(path)
assert.NoError(b, err, "Failed to run sample.")
}
})
}
}

26
cmd/lambda/registry.go Normal file
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@@ -0,0 +1,26 @@
package main
import (
"git.maximhutz.com/max/lambda/internal/cli"
"git.maximhutz.com/max/lambda/internal/registry"
"git.maximhutz.com/max/lambda/pkg/convert"
"git.maximhutz.com/max/lambda/pkg/engine/normalorder"
"git.maximhutz.com/max/lambda/pkg/lambda"
"git.maximhutz.com/max/lambda/pkg/saccharine"
)
func GetRegistry() *registry.Registry {
r := registry.New()
// Codecs
r.MustAddConversions(cli.ConvertCodec(convert.Saccharine2Lambda{}, "saccharine", "lambda")...)
// Engines
r.MustAddEngine(cli.ConvertEngine(normalorder.Engine{}, "normalorder", "lambda"))
// Marshalers
r.MustAddMarshaler(cli.ConvertMarshaler(lambda.Marshaler{}, "lambda"))
r.MustAddMarshaler(cli.ConvertMarshaler(saccharine.Marshaler{}, "saccharine"))
return r
}