package graph

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestNewDependencyGraph(t *testing.T) {
	graph := NewDependencyGraph()
	assert.NotNil(t, graph)
	assert.Equal(t, 0, len(graph.GetAllTasks()))
}

func TestAddTask(t *testing.T) {
	graph := NewDependencyGraph()

	task := &Task{ID: "T1", Title: "Task 1"}
	err := graph.AddTask(task)

	assert.NoError(t, err)
	retrieved, exists := graph.GetTask("T1")
	assert.True(t, exists)
	assert.Equal(t, "T1", retrieved.ID)
}

func TestAddTaskNil(t *testing.T) {
	graph := NewDependencyGraph()
	err := graph.AddTask(nil)
	assert.Error(t, err)
}

func TestAddTaskDuplicate(t *testing.T) {
	graph := NewDependencyGraph()

	task := &Task{ID: "T1", Title: "Task 1"}
	graph.AddTask(task)

	err := graph.AddTask(task)
	assert.Error(t, err)
}

func TestAddDependency(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})

	err := graph.AddDependency("T2", "T1")
	assert.NoError(t, err)

	deps, _ := graph.GetDependencies("T2")
	assert.Equal(t, 1, len(deps))
	assert.Equal(t, "T1", deps[0])
}

func TestAddDependencyNotFound(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})

	err := graph.AddDependency("T2", "T1")
	assert.Error(t, err)
}

func TestValidateGraphNoCycles(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T2")

	err := graph.ValidateGraph()
	assert.NoError(t, err)
}

func TestValidateGraphWithCycle(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T2")
	graph.AddDependency("T1", "T3") // Creates cycle

	err := graph.ValidateGraph()
	assert.Error(t, err)
}

func TestGetTopologicalOrder(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T2")

	graph.ValidateGraph()
	order, err := graph.GetTopologicalOrder()

	assert.NoError(t, err)
	assert.Equal(t, 3, len(order))
	assert.Equal(t, "T1", order[0])
	assert.Equal(t, "T2", order[1])
	assert.Equal(t, "T3", order[2])
}

func TestGetReadyTasks(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T1")

	ready := graph.GetReadyTasks()
	assert.Equal(t, 1, len(ready))
	assert.Equal(t, "T1", ready[0])

	graph.MarkCompleted("T1")
	ready = graph.GetReadyTasks()
	assert.Equal(t, 2, len(ready))
}

func TestMarkCompleted(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	err := graph.MarkCompleted("T1")

	assert.NoError(t, err)
	status, _ := graph.GetTaskStatus("T1")
	assert.Equal(t, "completed", status)
}

func TestMarkFailed(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	err := graph.MarkFailed("T1")

	assert.NoError(t, err)
	status, _ := graph.GetTaskStatus("T1")
	assert.Equal(t, "failed", status)
}

func TestGetDependencies(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T3", "T1")
	graph.AddDependency("T3", "T2")

	deps, _ := graph.GetDependencies("T3")
	assert.Equal(t, 2, len(deps))
}

func TestGetDependents(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})
	graph.AddTask(&Task{ID: "T3", Title: "Task 3"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T1")

	dependents, _ := graph.GetDependents("T1")
	assert.Equal(t, 2, len(dependents))
}

func TestCanExecuteTask(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})

	graph.AddDependency("T2", "T1")

	assert.False(t, graph.CanExecuteTask("T2"))

	graph.MarkCompleted("T1")
	assert.True(t, graph.CanExecuteTask("T2"))
}

func TestGetGraphStats(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	graph.AddTask(&Task{ID: "T2", Title: "Task 2"})

	graph.MarkCompleted("T1")

	stats := graph.GetGraphStats()
	assert.Equal(t, 2, stats["total_tasks"])
	assert.Equal(t, 1, stats["completed_tasks"])
	assert.Equal(t, 1, stats["pending_tasks"])
}

func TestClear(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1", Title: "Task 1"})
	assert.Equal(t, 1, len(graph.GetAllTasks()))

	graph.Clear()
	assert.Equal(t, 0, len(graph.GetAllTasks()))
}

func TestMultipleDependencies(t *testing.T) {
	graph := NewDependencyGraph()

	for i := 1; i <= 5; i++ {
		id := string(rune(48 + i))
		graph.AddTask(&Task{ID: "T" + id, Title: "Task " + id})
	}

	// Chain: T1 -> T2 -> T3 -> T4 -> T5
	for i := 2; i <= 5; i++ {
		graph.AddDependency("T"+string(rune(48+i)), "T"+string(rune(48+i-1)))
	}

	ready := graph.GetReadyTasks()
	assert.Equal(t, 1, len(ready))
	assert.Equal(t, "T1", ready[0])
}

func TestDiamondDependency(t *testing.T) {
	graph := NewDependencyGraph()

	// Diamond: T1 -> (T2, T3) -> T4
	graph.AddTask(&Task{ID: "T1"})
	graph.AddTask(&Task{ID: "T2"})
	graph.AddTask(&Task{ID: "T3"})
	graph.AddTask(&Task{ID: "T4"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T1")
	graph.AddDependency("T4", "T2")
	graph.AddDependency("T4", "T3")

	graph.ValidateGraph()
	order, _ := graph.GetTopologicalOrder()

	assert.Equal(t, 4, len(order))
	assert.Equal(t, "T1", order[0])
	assert.Equal(t, "T4", order[3])
}

func TestGetCriticalPath(t *testing.T) {
	graph := NewDependencyGraph()

	graph.AddTask(&Task{ID: "T1"})
	graph.AddTask(&Task{ID: "T2"})
	graph.AddTask(&Task{ID: "T3"})
	graph.AddTask(&Task{ID: "T4"})

	graph.AddDependency("T2", "T1")
	graph.AddDependency("T3", "T2")
	graph.AddDependency("T4", "T3")

	graph.ValidateGraph()
	graph.GetTopologicalOrder()

	path := graph.GetCriticalPath()
	assert.Greater(t, len(path), 0)
	assert.Equal(t, "T1", path[0])
}

func TestComplexGraph(t *testing.T) {
	graph := NewDependencyGraph()

	// Create 10 tasks with complex dependencies
	for i := 1; i <= 10; i++ {
		id := string(rune(48 + i%10))
		if i >= 10 {
			id = "T" + id
		} else {
			id = "T0" + id
		}
		graph.AddTask(&Task{ID: id})
	}

	// Add various dependencies
	graph.AddDependency("T02", "T01")
	graph.AddDependency("T03", "T01")
	graph.AddDependency("T04", "T02")
	graph.AddDependency("T04", "T03")

	graph.ValidateGraph()
	order, _ := graph.GetTopologicalOrder()
	assert.Equal(t, 10, len(order))
}

func TestTaskWithMetadata(t *testing.T) {
	graph := NewDependencyGraph()

	task := &Task{
		ID:    "T1",
		Title: "Task 1",
		Metadata: map[string]interface{}{
			"priority": "high",
			"owner":    "team-a",
		},
	}

	graph.AddTask(task)
	retrieved, _ := graph.GetTask("T1")
	assert.Equal(t, "high", retrieved.Metadata["priority"])
}

func TestGetAllTasks(t *testing.T) {
	graph := NewDependencyGraph()

	for i := 1; i <= 5; i++ {
		id := string(rune(48 + i))
		graph.AddTask(&Task{ID: "T" + id})
	}

	all := graph.GetAllTasks()
	assert.Equal(t, 5, len(all))
}

func BenchmarkAddTask(b *testing.B) {
	graph := NewDependencyGraph()

	for i := 0; i < b.N; i++ {
		id := string(rune(48 + i%100))
		graph.AddTask(&Task{ID: "T" + id})
	}
}

func BenchmarkAddDependency(b *testing.B) {
	graph := NewDependencyGraph()

	for i := 0; i < 1000; i++ {
		graph.AddTask(&Task{ID: "T" + string(rune(48+i%100))})
	}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		from := "T" + string(rune(48+i%100))
		to := "T" + string(rune(48+(i+1)%100))
		graph.AddDependency(from, to)
	}
}

func BenchmarkGetReadyTasks(b *testing.B) {
	graph := NewDependencyGraph()

	for i := 1; i <= 100; i++ {
		id := "T" + string(rune(48+i%100))
		graph.AddTask(&Task{ID: id})
	}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		graph.GetReadyTasks()
	}
}