package analytics

import (
	"os"
	"path/filepath"
	"runtime"
	"sync"
	"testing"
)

func TestDaySaltIsStableAndRotates(t *testing.T) {
	dir := t.TempDir()
	a, err := DaySalt(dir, "2026-09-07")
	if err != nil || len(a) != 32 {
		t.Fatalf("salt: %v len=%d", err, len(a))
	}
	b, _ := DaySalt(dir, "2026-09-07")
	if string(a) != string(b) {
		t.Fatal("same day must return the same salt (restart-stable)")
	}
	if runtime.GOOS != "windows" {
		st, _ := os.Stat(filepath.Join(dir, "analytics-salt-2026-09-07"))
		if st.Mode().Perm() != 0o600 {
			t.Fatalf("mode %v", st.Mode().Perm())
		}
	}
	c, _ := DaySalt(dir, "2026-09-08")
	if string(c) == string(a) {
		t.Fatal("a new day must salt afresh")
	}
	if _, err := os.Stat(filepath.Join(dir, "analytics-salt-2026-09-07")); !os.IsNotExist(err) {
		t.Fatal("rotation must delete the previous day's salt")
	}
}

func TestDaySaltConcurrentCallersAgree(t *testing.T) {
	dir := t.TempDir()
	const n = 8
	results := make([][]byte, n)
	errs := make([]error, n)
	var wg sync.WaitGroup
	wg.Add(n)
	for i := 0; i < n; i++ {
		i := i
		go func() {
			defer wg.Done()
			results[i], errs[i] = DaySalt(dir, "2026-09-07")
		}()
	}
	wg.Wait()
	for i, err := range errs {
		if err != nil {
			t.Fatalf("goroutine %d: %v", i, err)
		}
		if len(results[i]) != 32 {
			t.Fatalf("goroutine %d: len=%d", i, len(results[i]))
		}
	}
	for i := 1; i < n; i++ {
		if string(results[i]) != string(results[0]) {
			t.Fatalf("goroutine %d's salt disagrees with goroutine 0's", i)
		}
	}
}