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style: restructure cli and registry packages (#43)

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## Description

The `internal/cli` package had grown to contain both CLI utilities (source/destination I/O) and registry-level abstractions (repr, conversion, engine, marshaler).
This PR separates concerns by moving registry types into `internal/registry` and keeping only CLI I/O types in `internal/cli`.
It also simplifies several core abstractions and aligns naming conventions.

- Move `Source`, `Destination` from `internal/config` to `internal/cli`.
- Move `Repr`, `Conversion`, `Engine`, `Process`, `Codec` from `internal/cli` to `internal/registry`.
- Rename "marshalers" to "codecs" throughout the codebase.
- Simplify `codec.Codec[T, U]` to `codec.Codec[T]` (string-based marshaling only).
- Add `codec.Conversion[T, U]` as a function type alias.
- Change `engine.Engine[T]` from an interface to a function type.
- Merge `Engine.Load()` + `Process.Set()` into a single `Engine.Load(Repr)` call.
- Convert `Saccharine2Lambda` from a struct to standalone conversion functions.
- Replace registry methods (`MustAddMarshaler`, `MustAddEngine`, `MustAddConversions`) with generic free functions (`RegisterCodec`, `RegisterEngine`, `RegisterConversion`).
- Remove unused `internal/config` package (`Config`, `GetLogger`, `ParseFromArgs`).
- Remove unused `pkg/emitter` package.
- Rename `Id()` to `ID()` per Go conventions.
- Add documentation comments and enable `checkPublicInterface` lint rule.
- Rename `reduce_one.go` to `reduce_once.go`.

### Decisions

- `Engine[T]` is now a function type (`func(T) (Process[T], error)`) rather than an interface, since the only method was `Load`.
- `Codec[T, U]` was split into `Codec[T]` (string marshaling) and `Conversion[T, U]` (type-to-type conversion function), which better reflects how they are actually used.
- Registration uses free generic functions (`RegisterCodec`, `RegisterEngine`, `RegisterConversion`) instead of methods on `Registry`, enabling type inference at the call site.

## Benefits

- Clearer separation of concerns between CLI I/O and the registry's internal type system.
- Simpler abstractions: fewer interfaces, fewer wrapper types, fewer indirections.
- Removing unused packages (`config`, `emitter`) reduces maintenance burden.
- Naming conventions (`ID`, codecs, `reduce_once`) are more idiomatic.

## Checklist

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

Reviewed-on: #43
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 #43.
This commit is contained in:
Maxim Hutz
2026-02-07 05:39:32 +00:00
committed by Maxim Hutz
parent 58d0823069
commit bbe027e9f4
29 changed files with 250 additions and 453 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
internal/cli/cli.go Normal file
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@@ -0,0 +1,2 @@
// Package cli package provides various utilities to the 'lambda' program.
package cli

67
internal/cli/conversion.go
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@@ -1,67 +0,0 @@
package cli
import (
"fmt"
"git.maximhutz.com/max/lambda/pkg/codec"
)
type Conversion interface {
InType() string
OutType() string
Run(Repr) (Repr, error)
}
type forwardCodec[T, U any] struct {
codec codec.Codec[T, U]
inType, outType string
}
func (c forwardCodec[T, U]) Run(r Repr) (Repr, error) {
t, ok := r.Data().(T)
if !ok {
return nil, fmt.Errorf("could not parse '%v' as '%s'", t, c.inType)
}
u, err := c.codec.Encode(t)
if err != nil {
return nil, err
}
return NewRepr(c.outType, u), nil
}
func (c forwardCodec[T, U]) InType() string { return c.inType }
func (c forwardCodec[T, U]) OutType() string { return c.outType }
type backwardCodec[T, U any] struct {
codec codec.Codec[T, U]
inType, outType string
}
func (c backwardCodec[T, U]) Run(r Repr) (Repr, error) {
u, ok := r.Data().(U)
if !ok {
return nil, fmt.Errorf("could not parse '%v' as '%s'", r, c.outType)
}
t, err := c.codec.Decode(u)
if err != nil {
return nil, err
}
return NewRepr(c.inType, t), nil
}
func (c backwardCodec[T, U]) InType() string { return c.outType }
func (c backwardCodec[T, U]) OutType() string { return c.inType }
func ConvertCodec[T, U any](e codec.Codec[T, U], inType, outType string) []Conversion {
return []Conversion{
forwardCodec[T, U]{e, inType, outType},
backwardCodec[T, U]{e, inType, outType},
}
}

10
internal/config/destination.go → internal/cli/destination.go
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@@ -1,27 +1,29 @@
package config
package cli
import (
"fmt"
"os"
)
// A method of writing output to the user.
// A Destination is method of writing output to the user.
type Destination interface {
// Write data to this destination.
Write(data string) error
}
// A destination writing to stdout.
// An StdoutDestination writes to stdout.
type StdoutDestination struct{}
// Write outputs to standard output.
func (d StdoutDestination) Write(data string) error {
fmt.Println(data)
return nil
}
// A destination writing to a file.
// A FileDestination writes to a file.
type FileDestination struct{ Path string }
// Write outputs to a file.
func (d FileDestination) Write(data string) error {
return os.WriteFile(d.Path, []byte(data+"\n"), 0644)
}

27
internal/cli/engine.go
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@@ -1,27 +0,0 @@
package cli
import "git.maximhutz.com/max/lambda/pkg/engine"
type Engine interface {
Load() Process
Name() string
InType() string
}
type convertedEngine[T any] struct {
engine engine.Engine[T]
name string
inType string
}
func (e convertedEngine[T]) InType() string { return e.inType }
func (e convertedEngine[T]) Name() string { return e.name }
func (e convertedEngine[T]) Load() Process {
return convertedProcess[T]{e.engine.Load(), e.inType}
}
func ConvertEngine[T any](e engine.Engine[T], name, inType string) Engine {
return &convertedEngine[T]{e, name, inType}
}

45
internal/cli/marshaler.go
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@@ -1,45 +0,0 @@
package cli
import (
"fmt"
"reflect"
"git.maximhutz.com/max/lambda/pkg/codec"
)
type Marshaler interface {
codec.Marshaler[Repr]
InType() string
}
type convertedMarshaler[T any] struct {
codec codec.Marshaler[T]
inType string
}
func (c convertedMarshaler[T]) Decode(s string) (Repr, error) {
t, err := c.codec.Decode(s)
if err != nil {
return nil, err
}
return NewRepr(c.inType, t), nil
}
func (c convertedMarshaler[T]) Encode(r Repr) (string, error) {
t, ok := r.Data().(T)
if !ok {
dataType := reflect.TypeOf(r.Data())
allowedType := reflect.TypeFor[T]()
return "", fmt.Errorf("marshaler for '%s' cannot parse '%s'", allowedType, dataType)
}
return c.codec.Encode(t)
}
func (c convertedMarshaler[T]) InType() string { return c.inType }
func ConvertMarshaler[T any](e codec.Marshaler[T], inType string) Marshaler {
return convertedMarshaler[T]{e, inType}
}

21
internal/cli/repr.go
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@@ -1,21 +0,0 @@
package cli
type Repr interface {
// Id returns to name of the objects underlying representation. If is
// assumed that if two Repr objects have the same Id(), they share the same
// representation.
Id() string
Data() any
}
type baseRepr struct {
id string
data any
}
func (r baseRepr) Id() string { return r.id }
func (r baseRepr) Data() any { return r.data }
func NewRepr(id string, data any) Repr { return baseRepr{id, data} }

15
internal/config/source.go → internal/cli/source.go
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@@ -1,24 +1,26 @@
package config
package cli
import (
"io"
"os"
)
// A method of extracting input from the user.
// A Source is a method of extracting input from the user.
type Source interface {
// Fetch data from this source.
// Extract fetches data from this source.
Extract() (string, error)
}
// A source defined by a string.
// A StringSource is defined by a string.
type StringSource struct{ Data string }
// Extract pulls input data from the internal string.
func (s StringSource) Extract() (string, error) { return s.Data, nil }
// A source pulling from standard input.
// A StdinSource pulls from standard input.
type StdinSource struct{}
// Extract pulls input data from standard input.
func (s StdinSource) Extract() (string, error) {
data, err := io.ReadAll(os.Stdin)
if err != nil {
@@ -28,9 +30,10 @@ func (s StdinSource) Extract() (string, error) {
return string(data), nil
}
// A source reading from a file.
// A FileSource reads from a file.
type FileSource struct{ Path string }
// Extract pulls input data from the file source.
func (s FileSource) Extract() (string, error) {
data, err := os.ReadFile(s.Path)
if err != nil {

12
internal/config/config.go
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@@ -1,12 +0,0 @@
// Package "config" parses ad handles the user settings given to the program.
package config
// Configuration settings for the program.
type Config struct {
Source Source // The source code given to the program.
Destination Destination // The destination for the final result.
Verbose bool // Whether or not to print debug logs.
Explanation bool // Whether or not to print an explanation of the reduction.
Profile string // If not nil, print a CPU profile during execution.
Statistics bool // Whether or not to print statistics.
}

23
internal/config/get_logger.go
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@@ -1,23 +0,0 @@
package config
import (
"log/slog"
"os"
)
// Returns a structured logger with the appropriate configurations.
func (c Config) GetLogger() *slog.Logger {
// By default, only print out errors.
level := slog.LevelError
// If the user set the output to be "VERBOSE", return the debug logs.
if c.Verbose {
level = slog.LevelInfo
}
return slog.New(
slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
Level: level,
}),
)
}

56
internal/config/parse_from_args.go
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@@ -1,56 +0,0 @@
package config
import (
"flag"
"fmt"
)
// Extract the program configuration from the command-line arguments.
func FromArgs() (*Config, error) {
// Relevant 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.")
statistics := flag.Bool("s", false, "Statistics. If set, the process will print various statistics about the run.")
profile := flag.String("p", "", "CPU profiling. If an output file is defined, the program will profile its execution and dump its results into it.")
file := flag.String("f", "", "File. If set, read source from the specified file.")
output := flag.String("o", "", "Output. If set, write result to the specified file. Use '-' for stdout (default).")
flag.Parse()
// Parse source type.
var source Source
if *file != "" {
// File flag takes precedence.
if flag.NArg() > 0 {
return nil, fmt.Errorf("cannot specify both -f flag and positional argument")
}
source = FileSource{Path: *file}
} else 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")
} else {
// Positional argument.
if flag.Arg(0) == "-" {
source = StdinSource{}
} else {
source = StringSource{Data: flag.Arg(0)}
}
}
// Parse destination type.
var destination Destination
if *output == "" || *output == "-" {
destination = StdoutDestination{}
} else {
destination = FileDestination{Path: *output}
}
return &Config{
Source: source,
Destination: destination,
Verbose: *verbose,
Explanation: *explanation,
Profile: *profile,
Statistics: *statistics,
}, nil
}

50
internal/registry/codec.go Normal file
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@@ -0,0 +1,50 @@
package registry
import (
"fmt"
"reflect"
"git.maximhutz.com/max/lambda/pkg/codec"
)
type Codec interface {
codec.Codec[Repr]
InType() string
}
type convertedCodec[T any] struct {
codec codec.Codec[T]
inType string
}
func (c convertedCodec[T]) Decode(s string) (Repr, error) {
t, err := c.codec.Decode(s)
if err != nil {
return nil, err
}
return NewRepr(c.inType, t), nil
}
func (c convertedCodec[T]) Encode(r Repr) (string, error) {
t, ok := r.Data().(T)
if !ok {
dataType := reflect.TypeOf(r.Data())
allowedType := reflect.TypeFor[T]()
return "", fmt.Errorf("Codec for '%s' cannot parse '%s'", allowedType, dataType)
}
return c.codec.Encode(t)
}
func (c convertedCodec[T]) InType() string { return c.inType }
func RegisterCodec[T any](registry *Registry, m codec.Codec[T], inType string) error {
if _, ok := registry.codecs[inType]; ok {
return fmt.Errorf("Codec for '%s' already registered", inType)
}
registry.codecs[inType] = convertedCodec[T]{m, inType}
return nil
}

43
internal/registry/conversion.go Normal file
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@@ -0,0 +1,43 @@
package registry
import (
"fmt"
"git.maximhutz.com/max/lambda/pkg/codec"
)
type Conversion interface {
InType() string
OutType() string
Run(Repr) (Repr, error)
}
type convertedConversion[T, U any] struct {
conversion codec.Conversion[T, U]
inType, outType string
}
func (c convertedConversion[T, U]) Run(r Repr) (Repr, error) {
t, ok := r.Data().(T)
if !ok {
return nil, fmt.Errorf("could not parse '%v' as '%s'", t, c.inType)
}
u, err := c.conversion(t)
if err != nil {
return nil, err
}
return NewRepr(c.outType, u), nil
}
func (c convertedConversion[T, U]) InType() string { return c.inType }
func (c convertedConversion[T, U]) OutType() string { return c.outType }
func RegisterConversion[T, U any](registry *Registry, conversion func(T) (U, error), inType, outType string) error {
registry.converter.Add(convertedConversion[T, U]{conversion, inType, outType})
return nil
}

14
internal/registry/converter.go
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@@ -1,27 +1,23 @@
package registry
import (
"git.maximhutz.com/max/lambda/internal/cli"
)
type Converter struct {
data map[string][]cli.Conversion
data map[string][]Conversion
}
func NewConverter() *Converter {
return &Converter{data: map[string][]cli.Conversion{}}
return &Converter{data: map[string][]Conversion{}}
}
func (g *Converter) Add(c cli.Conversion) {
func (g *Converter) Add(c Conversion) {
conversionsFromIn, ok := g.data[c.InType()]
if !ok {
conversionsFromIn = []cli.Conversion{}
conversionsFromIn = []Conversion{}
}
conversionsFromIn = append(conversionsFromIn, c)
g.data[c.InType()] = conversionsFromIn
}
func (g *Converter) ConversionsFrom(t string) []cli.Conversion {
func (g *Converter) ConversionsFrom(t string) []Conversion {
return g.data[t]
}

46
internal/registry/engine.go Normal file
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@@ -0,0 +1,46 @@
package registry
import (
"fmt"
"git.maximhutz.com/max/lambda/pkg/engine"
)
type Engine interface {
Load(Repr) (Process, error)
Name() string
InType() string
}
type convertedEngine[T any] struct {
engine engine.Engine[T]
name string
inType string
}
func (e convertedEngine[T]) InType() string { return e.inType }
func (e convertedEngine[T]) Name() string { return e.name }
func (e convertedEngine[T]) Load(r Repr) (Process, error) {
t, ok := r.Data().(T)
if !ok {
return nil, fmt.Errorf("'ncorrent format '%s' for engine '%s'", r.ID(), e.inType)
}
process, err := e.engine(t)
if err != nil {
return nil, err
}
return convertedProcess[T]{process, e.inType}, nil
}
func RegisterEngine[T any](registry *Registry, e engine.Engine[T], name, inType string) error {
if _, ok := registry.engines[name]; ok {
return fmt.Errorf("engine '%s' already registered", name)
}
registry.engines[name] = &convertedEngine[T]{e, name, inType}
return nil
}

12
internal/cli/process.go → internal/registry/process.go
View File

@@ -1,8 +1,6 @@
package cli
package registry
import (
"fmt"
"git.maximhutz.com/max/lambda/pkg/engine"
)
@@ -28,14 +26,6 @@ func (b convertedProcess[T]) Get() (Repr, error) {
return NewRepr(b.inType, s), nil
}
func (b convertedProcess[T]) Set(r Repr) error {
if t, ok := r.Data().(T); ok {
return b.process.Set(t)
}
return fmt.Errorf("Incorrent format '%s' for engine '%s'.", r.Id(), b.inType)
}
func (b convertedProcess[T]) Step(i int) bool {
return b.process.Step(i)
}

83
internal/registry/registry.go
View File

@@ -4,68 +4,23 @@ import (
"fmt"
"iter"
"maps"
"git.maximhutz.com/max/lambda/internal/cli"
)
type Registry struct {
marshalers map[string]cli.Marshaler
converter *Converter
engines map[string]cli.Engine
codecs map[string]Codec
converter *Converter
engines map[string]Engine
}
func New() *Registry {
return &Registry{
marshalers: map[string]cli.Marshaler{},
converter: NewConverter(),
engines: map[string]cli.Engine{},
codecs: map[string]Codec{},
converter: NewConverter(),
engines: map[string]Engine{},
}
}
func (r *Registry) AddConversions(conversions ...cli.Conversion) error {
for _, conversion := range conversions {
r.converter.Add(conversion)
}
return nil
}
func (r *Registry) MustAddConversions(conversions ...cli.Conversion) {
if err := r.AddConversions(conversions...); err != nil {
panic(err)
}
}
func (r *Registry) AddMarshaler(c cli.Marshaler) error {
if _, ok := r.marshalers[c.InType()]; ok {
return fmt.Errorf("marshaler for '%s' already registered", c.InType())
}
r.marshalers[c.InType()] = c
return nil
}
func (r *Registry) MustAddMarshaler(c cli.Marshaler) {
if err := r.AddMarshaler(c); err != nil {
panic(err)
}
}
func (r *Registry) AddEngine(e cli.Engine) error {
if _, ok := r.engines[e.Name()]; ok {
return fmt.Errorf("engine '%s' already registered", e.Name())
}
r.engines[e.Name()] = e
return nil
}
func (r *Registry) MustAddEngine(e cli.Engine) {
if err := r.AddEngine(e); err != nil {
panic(err)
}
}
func (r Registry) GetEngine(name string) (cli.Engine, error) {
func (r Registry) GetEngine(name string) (Engine, error) {
e, ok := r.engines[name]
if !ok {
return nil, fmt.Errorf("engine '%s' not found", name)
@@ -74,11 +29,11 @@ func (r Registry) GetEngine(name string) (cli.Engine, error) {
return e, nil
}
func (r Registry) ListEngines() iter.Seq[cli.Engine] {
func (r Registry) ListEngines() iter.Seq[Engine] {
return maps.Values(r.engines)
}
func (r *Registry) GetDefaultEngine(id string) (cli.Engine, error) {
func (r *Registry) GetDefaultEngine(id string) (Engine, error) {
for _, engine := range r.engines {
if engine.InType() == id {
return engine, nil
@@ -88,8 +43,8 @@ func (r *Registry) GetDefaultEngine(id string) (cli.Engine, error) {
return nil, fmt.Errorf("no engine for '%s'", id)
}
func (r *Registry) ConvertTo(repr cli.Repr, outType string) (cli.Repr, error) {
path, err := r.ConversionPath(repr.Id(), outType)
func (r *Registry) ConvertTo(repr Repr, outType string) (Repr, error) {
path, err := r.ConversionPath(repr.ID(), outType)
if err != nil {
return nil, err
}
@@ -105,17 +60,17 @@ func (r *Registry) ConvertTo(repr cli.Repr, outType string) (cli.Repr, error) {
return result, err
}
func (r *Registry) Marshal(repr cli.Repr) (string, error) {
m, ok := r.marshalers[repr.Id()]
func (r *Registry) Marshal(repr Repr) (string, error) {
m, ok := r.codecs[repr.ID()]
if !ok {
return "", fmt.Errorf("no marshaler for '%s'", repr.Id())
return "", fmt.Errorf("no marshaler for '%s'", repr.ID())
}
return m.Encode(repr)
}
func (r *Registry) Unmarshal(s string, outType string) (cli.Repr, error) {
m, ok := r.marshalers[outType]
func (r *Registry) Unmarshal(s string, outType string) (Repr, error) {
m, ok := r.codecs[outType]
if !ok {
return nil, fmt.Errorf("no marshaler for '%s'", outType)
}
@@ -137,8 +92,8 @@ func reverse[T any](list []T) []T {
return reversed
}
func (r *Registry) ConversionPath(from, to string) ([]cli.Conversion, error) {
backtrack := map[string]cli.Conversion{}
func (r *Registry) ConversionPath(from, to string) ([]Conversion, error) {
backtrack := map[string]Conversion{}
iteration := []string{from}
for len(iteration) > 0 {
nextIteration := []string{}
@@ -157,7 +112,7 @@ func (r *Registry) ConversionPath(from, to string) ([]cli.Conversion, error) {
iteration = nextIteration
}
reversedPath := []cli.Conversion{}
reversedPath := []Conversion{}
current := to
for current != from {
conversion, ok := backtrack[current]

24
internal/registry/repr.go Normal file
View File

@@ -0,0 +1,24 @@
package registry
// A Repr is a lambda calculus expression. It can have any type of
// representation, so long as that class is known to the registry it is handled
// by.
type Repr interface {
// ID returns the name of the underlying representation. It is assumed that
// if two expressions have the same Id(), they have the same representation.
ID() string
// The base expression data.
Data() any
}
type baseRepr struct {
id string
data any
}
func (r baseRepr) ID() string { return r.id }
func (r baseRepr) Data() any { return r.data }
func NewRepr(id string, data any) Repr { return baseRepr{id, data} }