// SPDX-License-Identifier: MIT

package expr

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// TestToJSONGolden checks toJSON(fromJSON(x)) against the output of the
// reference implementation for each testdata/tojson/NAME.json. The .golden
// files are generated by gen/golden.mjs.
func TestToJSONGolden(t *testing.T) {
	inputs, err := filepath.Glob("testdata/tojson/*.json")
	if err != nil || len(inputs) < 30 {
		t.Fatalf("golden inputs: %v (%d found)", err, len(inputs))
	}
	for _, in := range inputs {
		name := strings.TrimSuffix(filepath.Base(in), ".json")
		t.Run(name, func(t *testing.T) {
			text, err := os.ReadFile(in)
			if err != nil {
				t.Fatal(err)
			}
			// NAME.golden is the answer of the JavaScript reference. Where
			// the C# runner answers differently, NAME.runner holds its
			// answer and is what this package follows (see PORTING.md).
			want, err := os.ReadFile(strings.TrimSuffix(in, ".json") + ".runner")
			fromRunner := err == nil
			if os.IsNotExist(err) {
				want, err = os.ReadFile(strings.TrimSuffix(in, ".json") + ".golden")
			}
			if err != nil {
				t.Fatal(err)
			}
			v, err := FromJSON(text)
			if err != nil {
				t.Fatal(err)
			}
			if got := ToJSON(v); got != string(want) {
				t.Errorf("toJSON mismatch\n got: %q\nwant: %q", got, want)
			}
			if fromRunner {
				// The runner's output is not JSON in general: numbers have 15
				// significant digits and NaN and Infinity are bare words.
				return
			}
			// The golden output is itself JSON that must round-trip.
			v2, err := FromJSON(want)
			if err != nil {
				t.Fatalf("golden output does not parse: %v", err)
			}
			if got := ToJSON(v2); got != string(want) {
				t.Errorf("toJSON is not stable\n got: %q\nwant: %q", got, want)
			}
		})
	}
}