package workers

import (
	"context"
	"testing"
	"time"

	luajit "git.sharkk.net/Sky/LuaJIT-to-Go"
)

// This helper function creates real LuaJIT bytecode for our tests. Instead of using
// mocks, we compile actual Lua code into bytecode just like we would in production.
func createTestBytecode(t *testing.T, code string) []byte {
	state := luajit.New()
	if state == nil {
		t.Fatal("Failed to create Lua state")
	}
	defer state.Close()

	bytecode, err := state.CompileBytecode(code, "test")
	if err != nil {
		t.Fatalf("Failed to compile test bytecode: %v", err)
	}

	return bytecode
}

// This test makes sure we can create a worker pool with a valid number of workers,
// and that we properly reject attempts to create a pool with zero or negative workers.
func TestNewPool(t *testing.T) {
	tests := []struct {
		name      string
		workers   int
		expectErr bool
	}{
		{"valid workers", 4, false},
		{"zero workers", 0, true},
		{"negative workers", -1, true},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			pool, err := NewPool(tt.workers)

			if tt.expectErr {
				if err == nil {
					t.Errorf("Expected error for %d workers, got nil", tt.workers)
				}
			} else {
				if err != nil {
					t.Errorf("Unexpected error: %v", err)
				}
				if pool == nil {
					t.Errorf("Expected non-nil pool")
				} else {
					pool.Shutdown()
				}
			}
		})
	}
}

// Here we're testing the basic job submission flow. We run a simple Lua script
// that returns the number 42 and make sure we get that same value back from the worker pool.
func TestPoolSubmit(t *testing.T) {
	pool, err := NewPool(2)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	bytecode := createTestBytecode(t, "return 42")

	result, err := pool.Submit(bytecode, nil)
	if err != nil {
		t.Fatalf("Failed to submit job: %v", err)
	}

	num, ok := result.(float64)
	if !ok {
		t.Fatalf("Expected float64 result, got %T", result)
	}

	if num != 42 {
		t.Errorf("Expected 42, got %f", num)
	}
}

// This test checks how our worker pool handles timeouts. We run a script that takes
// some time to complete and verify two scenarios: one where the timeout is long enough
// for successful completion, and another where we expect the operation to be canceled
// due to a short timeout.
func TestPoolSubmitWithContext(t *testing.T) {
	pool, err := NewPool(2)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	// Create bytecode that sleeps
	bytecode := createTestBytecode(t, `
		-- Sleep for 500ms
		local start = os.time()
		while os.difftime(os.time(), start) < 0.5 do end
		return "done"
	`)

	// Test with timeout that should succeed
	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
	defer cancel()

	result, err := pool.SubmitWithContext(ctx, bytecode, nil)
	if err != nil {
		t.Fatalf("Unexpected error with sufficient timeout: %v", err)
	}
	if result != "done" {
		t.Errorf("Expected 'done', got %v", result)
	}

	// Test with timeout that should fail
	ctx, cancel = context.WithTimeout(context.Background(), 50*time.Millisecond)
	defer cancel()

	_, err = pool.SubmitWithContext(ctx, bytecode, nil)
	if err == nil {
		t.Errorf("Expected timeout error, got nil")
	}
}

// We need to make sure we can pass different types of parameters from Go to Lua and
// get them back properly. This test sends numbers, strings, booleans, and arrays to
// a Lua script and verifies they're all handled correctly in both directions.
func TestJobParameters(t *testing.T) {
	pool, err := NewPool(2)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	bytecode := createTestBytecode(t, `
		return {
			num = params.number,
			str = params.text,
			flag = params.enabled,
			list = {params.table[1], params.table[2], params.table[3]},
		}
	`)

	params := map[string]any{
		"number":  42.5,
		"text":    "hello",
		"enabled": true,
		"table":   []float64{10, 20, 30},
	}

	result, err := pool.Submit(bytecode, params)
	if err != nil {
		t.Fatalf("Failed to submit job: %v", err)
	}

	// Result should be a map
	resultMap, ok := result.(map[string]any)
	if !ok {
		t.Fatalf("Expected map result, got %T", result)
	}

	// Check values
	if resultMap["num"] != 42.5 {
		t.Errorf("Expected num=42.5, got %v", resultMap["num"])
	}
	if resultMap["str"] != "hello" {
		t.Errorf("Expected str=hello, got %v", resultMap["str"])
	}
	if resultMap["flag"] != true {
		t.Errorf("Expected flag=true, got %v", resultMap["flag"])
	}

	arr, ok := resultMap["list"].([]float64)
	if !ok {
		t.Fatalf("Expected []float64, got %T", resultMap["list"])
	}

	expected := []float64{10, 20, 30}
	for i, v := range expected {
		if arr[i] != v {
			t.Errorf("Expected list[%d]=%f, got %f", i, v, arr[i])
		}
	}
}

// A key requirement for our worker pool is that we don't leak state between executions.
// This test confirms that by setting a global variable in one job and then checking
// that it's been cleared before the next job runs on the same worker.
func TestStateReset(t *testing.T) {
	pool, err := NewPool(1) // Use 1 worker to ensure same state is reused
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	// First job sets a global
	bytecode1 := createTestBytecode(t, `
		global_var = "should be cleared"
		return true
	`)

	// Second job checks if global exists
	bytecode2 := createTestBytecode(t, `
		return global_var ~= nil
	`)

	// Run first job
	_, err = pool.Submit(bytecode1, nil)
	if err != nil {
		t.Fatalf("Failed to submit first job: %v", err)
	}

	// Run second job
	result, err := pool.Submit(bytecode2, nil)
	if err != nil {
		t.Fatalf("Failed to submit second job: %v", err)
	}

	// Global should be cleared
	if result.(bool) {
		t.Errorf("Expected global_var to be cleared, but it still exists")
	}
}

// Let's make sure our pool shuts down cleanly. This test confirms that jobs work
// before shutdown, that we get the right error when trying to submit after shutdown,
// and that we properly handle attempts to shut down an already closed pool.
func TestPoolShutdown(t *testing.T) {
	pool, err := NewPool(2)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}

	// Submit a job to verify pool works
	bytecode := createTestBytecode(t, "return 42")
	_, err = pool.Submit(bytecode, nil)
	if err != nil {
		t.Fatalf("Failed to submit job: %v", err)
	}

	// Shutdown
	if err := pool.Shutdown(); err != nil {
		t.Errorf("Shutdown failed: %v", err)
	}

	// Submit after shutdown should fail
	_, err = pool.Submit(bytecode, nil)
	if err != ErrPoolClosed {
		t.Errorf("Expected ErrPoolClosed, got %v", err)
	}

	// Second shutdown should return error
	if err := pool.Shutdown(); err != ErrPoolClosed {
		t.Errorf("Expected ErrPoolClosed on second shutdown, got %v", err)
	}
}

// A robust worker pool needs to handle errors gracefully. This test checks various
// error scenarios: invalid bytecode, Lua runtime errors, nil parameters (which
// should work fine), and unsupported parameter types (which should properly error out).
func TestErrorHandling(t *testing.T) {
	pool, err := NewPool(2)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	// Test invalid bytecode
	_, err = pool.Submit([]byte("not valid bytecode"), nil)
	if err == nil {
		t.Errorf("Expected error for invalid bytecode, got nil")
	}

	// Test Lua runtime error
	bytecode := createTestBytecode(t, `
		error("intentional error")
		return true
	`)

	_, err = pool.Submit(bytecode, nil)
	if err == nil {
		t.Errorf("Expected error from Lua error() call, got nil")
	}

	// Test invalid parameter
	bytecode = createTestBytecode(t, "return param")

	// This should work with nil value
	_, err = pool.Submit(bytecode, map[string]any{
		"param": nil,
	})
	if err != nil {
		t.Errorf("Unexpected error with nil param: %v", err)
	}

	// Complex type that can't be converted
	complex := map[string]any{
		"param": complex128(1 + 2i), // Unsupported type
	}

	_, err = pool.Submit(bytecode, complex)
	if err == nil {
		t.Errorf("Expected error for unsupported parameter type, got nil")
	}
}

// The whole point of a worker pool is concurrent processing, so we need to verify
// it works under load. This test submits multiple jobs simultaneously and makes sure
// they all complete correctly with their own unique results.
func TestConcurrentExecution(t *testing.T) {
	const workers = 4
	const jobs = 20

	pool, err := NewPool(workers)
	if err != nil {
		t.Fatalf("Failed to create pool: %v", err)
	}
	defer pool.Shutdown()

	// Create bytecode that returns its input
	bytecode := createTestBytecode(t, "return params.n")

	// Run multiple jobs concurrently
	results := make(chan int, jobs)
	for i := 0; i < jobs; i++ {
		i := i // Capture loop variable
		go func() {
			params := map[string]any{"n": float64(i)}
			result, err := pool.Submit(bytecode, params)
			if err != nil {
				t.Errorf("Job %d failed: %v", i, err)
				results <- -1
				return
			}

			num, ok := result.(float64)
			if !ok {
				t.Errorf("Job %d: expected float64, got %T", i, result)
				results <- -1
				return
			}

			results <- int(num)
		}()
	}

	// Collect results
	counts := make(map[int]bool)
	for i := 0; i < jobs; i++ {
		result := <-results
		if result != -1 {
			counts[result] = true
		}
	}

	// Verify all jobs were processed
	if len(counts) != jobs {
		t.Errorf("Expected %d unique results, got %d", jobs, len(counts))
	}
}