package queue

import (
	"testing"
	"time"
)

// TestTaskPrioritizationSpec documents the scheduler's priority and FIFO behavior.
// These tests serve as executable specifications for the queue system.
func TestTaskPrioritizationSpec(t *testing.T) {
	tests := []struct {
		name     string
		tasks    []Task
		expected []string // IDs in expected execution order
	}{
		{
			name: "higher priority runs first",
			tasks: []Task{
				{ID: "low", Priority: 1, CreatedAt: time.Unix(100, 0)},
				{ID: "high", Priority: 10, CreatedAt: time.Unix(100, 0)},
			},
			expected: []string{"high", "low"},
		},
		{
			name: "FIFO for same priority",
			tasks: []Task{
				{ID: "first", Priority: 5, CreatedAt: time.Unix(100, 0)},
				{ID: "second", Priority: 5, CreatedAt: time.Unix(200, 0)},
			},
			expected: []string{"first", "second"},
		},
		{
			name: "mixed priorities and creation times",
			tasks: []Task{
				{ID: "medium-early", Priority: 5, CreatedAt: time.Unix(100, 0)},
				{ID: "high-late", Priority: 10, CreatedAt: time.Unix(300, 0)},
				{ID: "low-early", Priority: 1, CreatedAt: time.Unix(50, 0)},
			},
			expected: []string{"high-late", "medium-early", "low-early"},
		},
		{
			name: "negative priority is lowest",
			tasks: []Task{
				{ID: "negative", Priority: -1, CreatedAt: time.Unix(100, 0)},
				{ID: "positive", Priority: 1, CreatedAt: time.Unix(100, 0)},
			},
			expected: []string{"positive", "negative"},
		},
		{
			name: "zero priority is default",
			tasks: []Task{
				{ID: "zero", Priority: 0, CreatedAt: time.Unix(100, 0)},
				{ID: "positive", Priority: 1, CreatedAt: time.Unix(100, 0)},
			},
			expected: []string{"positive", "zero"},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Create a queue and add tasks
			tmpDir := t.TempDir()
			q, err := NewFilesystemQueue(tmpDir)
			if err != nil {
				t.Fatalf("failed to create queue: %v", err)
			}
			defer q.Close()

			// Add all tasks
			for _, task := range tt.tasks {
				task := task // capture range variable
				if err := q.AddTask(&task); err != nil {
					t.Fatalf("failed to add task %s: %v", task.ID, err)
				}
			}

			// Get tasks in order and verify
			var actual []string
			for i := 0; i < len(tt.tasks); i++ {
				task, err := q.GetNextTask()
				if err != nil {
					t.Fatalf("failed to get task at position %d: %v", i, err)
				}
				if task == nil {
					t.Fatalf("expected task at position %d, got nil", i)
				}
				actual = append(actual, task.ID)
			}

			// Verify order
			if len(actual) != len(tt.expected) {
				t.Errorf("expected %d tasks, got %d", len(tt.expected), len(actual))
			}
			for i, expectedID := range tt.expected {
				if i >= len(actual) {
					break
				}
				if actual[i] != expectedID {
					t.Errorf("position %d: expected %s, got %s", i, expectedID, actual[i])
				}
			}
		})
	}
}

// TestQueueSpec_ClaimAndComplete documents the claim-complete lifecycle
func TestQueueSpec_ClaimAndComplete(t *testing.T) {
	tmpDir := t.TempDir()
	q, err := NewFilesystemQueue(tmpDir)
	if err != nil {
		t.Fatalf("failed to create queue: %v", err)
	}
	defer q.Close()

	// Add a task
	task := &Task{
		ID:        "task-1",
		JobName:   "test-job",
		Priority:  5,
		CreatedAt: time.Now(),
	}
	if err := q.AddTask(task); err != nil {
		t.Fatalf("failed to add task: %v", err)
	}

	// Get the task
	claimed, err := q.GetNextTask()
	if err != nil {
		t.Fatalf("failed to get task: %v", err)
	}
	if claimed == nil {
		t.Fatal("expected to claim a task, got nil")
	}
	if claimed.ID != task.ID {
		t.Errorf("expected task %s, got %s", task.ID, claimed.ID)
	}

	// Verify task is no longer in queue
	tasks, err := q.GetAllTasks()
	if err != nil {
		t.Fatalf("failed to get tasks: %v", err)
	}
	for _, tsk := range tasks {
		if tsk.ID == task.ID {
			t.Error("claimed task should not be in queue")
		}
	}
}

// TestQueueSpec_TaskPriorityOrdering documents numeric priority ordering
func TestQueueSpec_TaskPriorityOrdering(t *testing.T) {
	tmpDir := t.TempDir()
	q, err := NewFilesystemQueue(tmpDir)
	if err != nil {
		t.Fatalf("failed to create queue: %v", err)
	}
	defer q.Close()

	// Add tasks with various priorities
	priorities := []int64{100, 50, 200, 1, 75}
	for i, p := range priorities {
		task := &Task{
			ID:        "task-" + string(rune('a'+i)),
			JobName:   "job-" + string(rune('a'+i)),
			Priority:  p,
			CreatedAt: time.Now(),
		}
		if err := q.AddTask(task); err != nil {
			t.Fatalf("failed to add task: %v", err)
		}
	}

	// Expected order: 200, 100, 75, 50, 1 (descending)
	expected := []string{"task-c", "task-a", "task-e", "task-b", "task-d"}

	for i, expID := range expected {
		task, err := q.GetNextTask()
		if err != nil {
			t.Fatalf("position %d: failed to get task: %v", i, err)
		}
		if task == nil {
			t.Fatalf("position %d: expected task %s, got nil", i, expID)
		}
		if task.ID != expID {
			t.Errorf("position %d: expected %s, got %s", i, expID, task.ID)
		}
	}
}