package config

import (
	"bytes"
	"io"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

func TestConfigFilePreservesDefaultsWithoutSharingMutableData(t *testing.T) {
	type cfg struct {
		Writer io.Writer                `json:"-"`
		Secret string                   `json:"-"`
		Values map[string]int64         `json:"values"`
		Timers map[string]time.Duration `json:"timers"`
		ID     int64                    `json:"id"`
	}
	var writer bytes.Buffer
	base := cfg{Writer: &writer, Secret: "borrowedSecret", Values: map[string]int64{"old": 7}, ID: 9007199254740993}
	file := filepath.Join(t.TempDir(), "config.json")
	if err := os.WriteFile(file, []byte(`{"values":{"new":2},"timers":{"retry":"2s"}}`), 0600); err != nil {
		t.Fatal(err)
	}
	next, err := DecodeFile(file, base)
	if err != nil {
		t.Fatal(err)
	}
	if next.Writer != &writer || next.Secret != base.Secret || next.ID != base.ID || next.Timers["retry"] != 2*time.Second || len(base.Values) != 1 {
		t.Fatal("defaults lost or mutated")
	}
	next.Values["old"] = 9
	if base.Values["old"] != 7 {
		t.Fatal("defaults shared map")
	}
	if err = os.WriteFile(file, []byte(`{"values":{"secretValue":"credential-super-secret"}}`), 0600); err != nil {
		t.Fatal(err)
	}
	if _, err = DecodeFile(file, base); err == nil || strings.Contains(err.Error(), "credential-super-secret") {
		t.Fatal("decode error leaked contents", err)
	}
}