package proc

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

func TestReadCgroup(t *testing.T) {
	tests := []struct {
		name       string
		cgroupFile string
		wantPath   string
		wantErr    bool
	}{
		{
			name: "cgroup v2 unified",
			cgroupFile: `0::/kubepods/pod-abc/container-123
`,
			wantPath: "/kubepods/pod-abc/container-123",
			wantErr:  false,
		},
		{
			name: "cgroup v2 with trailing newline",
			cgroupFile: `0::/docker/abc123def456
`,
			wantPath: "/docker/abc123def456",
			wantErr:  false,
		},
		{
			name: "cgroup v1 multiple controllers",
			cgroupFile: `12:blkio:/user.slice
11:memory:/docker/abc123
10:cpu,cpuacct:/docker/abc123
9:pids:/docker/abc123
`,
			wantPath: "/docker/abc123",
			wantErr:  false,
		},
		{
			name: "cgroup v2 preferred over v1",
			cgroupFile: `11:memory:/docker/old-path
0::/kubepods/new-path
`,
			wantPath: "/kubepods/new-path",
			wantErr:  false,
		},
		{
			name:       "empty file",
			cgroupFile: "",
			wantPath:   "",
			wantErr:    false,
		},
		{
			name: "root cgroup",
			cgroupFile: `0::/
`,
			wantPath: "/",
			wantErr:  false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Create a temp directory structure mimicking /proc
			tmpDir := t.TempDir()
			procDir := filepath.Join(tmpDir, "proc")
			pidDir := filepath.Join(procDir, "1234")

			if err := os.MkdirAll(pidDir, 0755); err != nil {
				t.Fatalf("Failed to create pid dir: %v", err)
			}

			if err := os.WriteFile(filepath.Join(pidDir, "cgroup"), []byte(tt.cgroupFile), 0644); err != nil {
				t.Fatalf("Failed to write cgroup file: %v", err)
			}

			got, err := ReadCgroup(procDir, 1234)
			if (err != nil) != tt.wantErr {
				t.Errorf("ReadCgroup() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			if !tt.wantErr && got.Path != tt.wantPath {
				t.Errorf("ReadCgroup() path = %q, want %q", got.Path, tt.wantPath)
			}
		})
	}
}

func TestReadCgroup_FileNotFound(t *testing.T) {
	tmpDir := t.TempDir()

	_, err := ReadCgroup(tmpDir, 1234)
	if err == nil {
		t.Error("ReadCgroup() expected error for missing file, got nil")
	}
}