interpres/cmd/interpres-decode/main.go

// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

// Command interpres-decode is the toml-test harness adapter and a TOML
// validator. Without flags it reads a TOML document from standard input and
// writes the toml-test "tagged JSON" representation to standard output. With
// -validate it checks the named documents, or standard input when none are
// named, and exits non-zero on the first invalid one:
//
//	interpres-decode -validate config.toml
//
// Run the official suite against the adapter with:
//
//	toml-test ./interpres-decode
package main

import (
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
	"time"

	"sourcedock.dev/petrbalvin/interpres"
)

func main() {
	os.Exit(Run(os.Args[1:], os.Stdin, os.Stdout, os.Stderr))
}

// Run runs the command line and returns the process exit code: 0 success,
// 1 an invalid document, 2 a usage, reading, encoding, or
// unsupported-value error.
func Run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("interpres-decode", flag.ContinueOnError)
	fs.SetOutput(stderr)
	validate := fs.Bool("validate", false, "validate the documents instead of emitting tagged JSON")
	if err := fs.Parse(args); err != nil {
		if errors.Is(err, flag.ErrHelp) {
			return 0
		}
		return 2
	}
	if *validate {
		return validatePaths(fs.Args(), stdin, stderr)
	}
	if fs.NArg() > 0 {
		fmt.Fprintln(stderr, "interpres-decode: the adapter mode takes no arguments; name files with -validate")
		return 2
	}
	data, err := io.ReadAll(stdin)
	if err != nil {
		fmt.Fprintln(stderr, "read stdin:", err)
		return 2
	}
	tree, err := interpres.Parse(data)
	if err != nil {
		fmt.Fprintln(stderr, err)
		return 1
	}
	tagged, err := tag(tree)
	if err != nil {
		fmt.Fprintln(stderr, err)
		return 2
	}
	enc := json.NewEncoder(stdout)
	enc.SetEscapeHTML(false)
	if err := enc.Encode(tagged); err != nil {
		fmt.Fprintln(stderr, "encode:", err)
		return 2
	}
	return 0
}

// validatePaths parses every named file, or standard input when none are
// named, and reports each invalid document on stderr. It returns 0 when all
// documents parse, 1 when one does not, and 2 on a usage or read failure.
func validatePaths(paths []string, stdin io.Reader, stderr io.Writer) int {
	if len(paths) == 0 {
		paths = []string{"-"}
	}
	valid := true
	for _, p := range paths {
		name := p
		var data []byte
		var err error
		if p == "-" {
			data, err = io.ReadAll(stdin)
			name = "<stdin>"
		} else {
			data, err = os.ReadFile(p)
		}
		if err != nil {
			fmt.Fprintf(stderr, "interpres-decode: %s: %v\n", name, err)
			return 2
		}
		if _, err := interpres.Parse(data); err != nil {
			fmt.Fprintf(stderr, "%s: %v\n", name, err)
			valid = false
		}
	}
	if !valid {
		return 1
	}
	return 0
}

// tag converts an interpres value into its toml-test tagged-JSON form. Tables
// become JSON objects and arrays become JSON arrays; scalars are wrapped in a
// {"type", "value"} object. An error is returned for value types the encoder
// has no tagged representation for.
func tag(v any) (any, error) {
	switch x := v.(type) {
	case map[string]any:
		out := make(map[string]any, len(x))
		for k, val := range x {
			tagged, err := tag(val)
			if err != nil {
				return nil, err
			}
			out[k] = tagged
		}
		return out, nil
	case []any:
		out := make([]any, len(x))
		for i, e := range x {
			tagged, err := tag(e)
			if err != nil {
				return nil, err
			}
			out[i] = tagged
		}
		return out, nil
	case []map[string]any:
		out := make([]any, len(x))
		for i, e := range x {
			tagged, err := tag(e)
			if err != nil {
				return nil, err
			}
			out[i] = tagged
		}
		return out, nil
	case string:
		return tagged("string", x), nil
	case bool:
		return tagged("bool", strconv.FormatBool(x)), nil
	case int64:
		return tagged("integer", strconv.FormatInt(x, 10)), nil
	case float64:
		return tagged("float", formatFloat(x)), nil
	case time.Time:
		return tagged("datetime", x.Format(time.RFC3339Nano)), nil
	case interpres.LocalDateTime:
		return tagged("datetime-local", x.Format("2006-01-02T15:04:05.999999999")), nil
	case interpres.LocalDate:
		return tagged("date-local", x.Format("2006-01-02")), nil
	case interpres.LocalTime:
		return tagged("time-local", x.Format("15:04:05.999999999")), nil
	default:
		return nil, fmt.Errorf("unsupported value type %T", v)
	}
}

func tagged(typ, value string) map[string]string {
	return map[string]string{"type": typ, "value": value}
}

func formatFloat(f float64) string {
	switch {
	case math.IsInf(f, 1):
		return "inf"
	case math.IsInf(f, -1):
		return "-inf"
	case math.IsNaN(f):
		return "nan"
	default:
		return strconv.FormatFloat(f, 'g', -1, 64)
	}
}