package discovery

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

func TestMemTotalIsReadFromMeminfo(t *testing.T) {
	dir := t.TempDir()
	p := filepath.Join(dir, "meminfo")
	// The real shape, including the fields before and after, so the parser is
	// not tested against something tidier than it will see.
	if err := os.WriteFile(p, []byte(
		"MemTotal:       32876244 kB\nMemFree:         1234 kB\nMemAvailable:   5678 kB\n"), 0o600); err != nil {
		t.Fatal(err)
	}
	if got, want := memTotalMBFrom(p), 32876244/1024; got != want {
		t.Errorf("memTotalMBFrom = %d, want %d", got, want)
	}
}

func TestUnreadableMeminfoReportsUnknownRatherThanZeroMemory(t *testing.T) {
	// Zero means "did not say" everywhere downstream, and placement treats it
	// as no constraint. A node with genuinely no memory is not a case.
	if got := memTotalMBFrom(filepath.Join(t.TempDir(), "absent")); got != 0 {
		t.Errorf("got %d for a missing file", got)
	}
	dir := t.TempDir()
	p := filepath.Join(dir, "meminfo")
	for _, junk := range []string{"", "MemTotal:\n", "MemTotal: not-a-number kB\n", "Other: 1 kB\n"} {
		if err := os.WriteFile(p, []byte(junk), 0o600); err != nil {
			t.Fatal(err)
		}
		if got := memTotalMBFrom(p); got != 0 {
			t.Errorf("got %d for %q", got, junk)
		}
	}
}