package runner

import (
	"context"
	"errors"
	"path/filepath"
	"sync"
	"sync/atomic"

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

// Common errors
var (
	ErrRunnerClosed = errors.New("lua runner is closed")
	ErrInitFailed   = errors.New("initialization failed")
)

// StateInitFunc is a function that initializes a Lua state
type StateInitFunc func(*luajit.State) error

// RunnerOption defines a functional option for configuring the LuaRunner
type RunnerOption func(*LuaRunner)

// Result channel pool to reduce allocations
var resultChanPool = sync.Pool{
	New: func() interface{} {
		return make(chan JobResult, 1)
	},
}

// LuaRunner runs Lua scripts using a single Lua state
type LuaRunner struct {
	state        *luajit.State       // The Lua state
	jobQueue     chan job            // Channel for incoming jobs
	isRunning    atomic.Bool         // Flag indicating if the runner is active
	mu           sync.RWMutex        // Mutex for thread safety
	wg           sync.WaitGroup      // WaitGroup for clean shutdown
	initFunc     StateInitFunc       // Optional function to initialize Lua state
	bufferSize   int                 // Size of the job queue buffer
	moduleLoader *NativeModuleLoader // Native module loader for require
	sandbox      *Sandbox            // The sandbox environment
	debug        bool                // Enable debug logging
}

// WithBufferSize sets the job queue buffer size
func WithBufferSize(size int) RunnerOption {
	return func(r *LuaRunner) {
		if size > 0 {
			r.bufferSize = size
		}
	}
}

// WithInitFunc sets the init function for the Lua state
func WithInitFunc(initFunc StateInitFunc) RunnerOption {
	return func(r *LuaRunner) {
		r.initFunc = initFunc
	}
}

// WithLibDirs sets additional library directories
func WithLibDirs(dirs ...string) RunnerOption {
	return func(r *LuaRunner) {
		if r.moduleLoader == nil || r.moduleLoader.config == nil {
			r.moduleLoader = NewNativeModuleLoader(&RequireConfig{
				LibDirs: dirs,
			})
		} else {
			r.moduleLoader.config.LibDirs = dirs
		}
	}
}

// WithDebugEnabled enables debug output
func WithDebugEnabled() RunnerOption {
	return func(r *LuaRunner) {
		r.debug = true
	}
}

// NewRunner creates a new LuaRunner
func NewRunner(options ...RunnerOption) (*LuaRunner, error) {
	// Default configuration
	runner := &LuaRunner{
		bufferSize: 10, // Default buffer size
		sandbox:    NewSandbox(),
		debug:      false,
	}

	// Apply options
	for _, opt := range options {
		opt(runner)
	}

	// Create job queue
	runner.jobQueue = make(chan job, runner.bufferSize)
	runner.isRunning.Store(true)

	// Set up module loader if not already initialized
	if runner.moduleLoader == nil {
		requireConfig := &RequireConfig{
			ScriptDir: "",
			LibDirs:   []string{},
		}
		runner.moduleLoader = NewNativeModuleLoader(requireConfig)
	}

	// Initialize Lua state
	if err := runner.initState(true); err != nil {
		return nil, err
	}

	// Start the event loop
	runner.wg.Add(1)
	go runner.processJobs()

	return runner, nil
}

// debugLog logs a message if debug mode is enabled
func (r *LuaRunner) debugLog(format string, args ...interface{}) {
	if r.debug {
		logger.Debug("[LuaRunner] "+format, args...)
	}
}

// initState initializes or reinitializes the Lua state
func (r *LuaRunner) initState(initial bool) error {
	r.debugLog("Initializing Lua state (initial=%v)", initial)

	// Clean up existing state if there is one
	if r.state != nil {
		r.debugLog("Cleaning up existing state")
		// Always call Cleanup before Close to properly free function pointers
		r.state.Cleanup()
		r.state.Close()
		r.state = nil
	}

	// Create fresh state
	state := luajit.New()
	if state == nil {
		return errors.New("failed to create Lua state")
	}
	r.debugLog("Created new Lua state")

	// Set up require paths and mechanism
	if err := r.moduleLoader.SetupRequire(state); err != nil {
		r.debugLog("Failed to set up require: %v", err)
		state.Cleanup()
		state.Close()
		return ErrInitFailed
	}
	r.debugLog("Require system initialized")

	// Initialize all core modules from the registry
	if err := GlobalRegistry.Initialize(state); err != nil {
		r.debugLog("Failed to initialize core modules: %v", err)
		state.Cleanup()
		state.Close()
		return ErrInitFailed
	}
	r.debugLog("Core modules initialized")

	// Check if http module is properly registered
	testResult, err := state.ExecuteWithResult(`
		if type(http) == "table" and type(http.client) == "table" and
		   type(http.client.get) == "function" then
			return true
		else
			return false
		end
	`)
	if err != nil || testResult != true {
		r.debugLog("HTTP module verification failed: %v, result: %v", err, testResult)
	} else {
		r.debugLog("HTTP module verified OK")
	}

	// Verify __http_request function
	testResult, _ = state.ExecuteWithResult(`return type(__http_request)`)
	r.debugLog("__http_request function is of type: %v", testResult)

	// Set up sandbox after core modules are initialized
	if err := r.sandbox.Setup(state); err != nil {
		r.debugLog("Failed to set up sandbox: %v", err)
		state.Cleanup()
		state.Close()
		return ErrInitFailed
	}
	r.debugLog("Sandbox environment set up")

	// Preload all modules into package.loaded
	if err := r.moduleLoader.PreloadAllModules(state); err != nil {
		r.debugLog("Failed to preload modules: %v", err)
		state.Cleanup()
		state.Close()
		return errors.New("failed to preload modules")
	}
	r.debugLog("All modules preloaded")

	// Run init function if provided
	if r.initFunc != nil {
		if err := r.initFunc(state); err != nil {
			r.debugLog("Custom init function failed: %v", err)
			state.Cleanup()
			state.Close()
			return ErrInitFailed
		}
		r.debugLog("Custom init function completed")
	}

	// Test for HTTP module again after full initialization
	testResult, err = state.ExecuteWithResult(`
		if type(http) == "table" and type(http.client) == "table" and
		   type(http.client.get) == "function" then
			return true
		else
			return false
		end
	`)
	if err != nil || testResult != true {
		r.debugLog("Final HTTP module verification failed: %v, result: %v", err, testResult)
	} else {
		r.debugLog("Final HTTP module verification OK")
	}

	r.state = state
	r.debugLog("State initialization complete")
	return nil
}

// processJobs handles the job queue
func (r *LuaRunner) processJobs() {
	defer r.wg.Done()
	defer func() {
		if r.state != nil {
			r.debugLog("Cleaning up Lua state in processJobs")
			r.state.Cleanup()
			r.state.Close()
			r.state = nil
		}
	}()

	for job := range r.jobQueue {
		// Execute the job and send result
		result := r.executeJob(job)
		select {
		case job.Result <- result:
			// Result sent successfully
		default:
			// Result channel closed or full, discard the result
		}
	}
}

// executeJob runs a script in the sandbox environment
func (r *LuaRunner) executeJob(j job) JobResult {
	// If the job has a script path, update script dir for module resolution
	if j.ScriptPath != "" {
		r.mu.Lock()
		r.moduleLoader.config.ScriptDir = filepath.Dir(j.ScriptPath)
		r.mu.Unlock()
	}

	// Convert context for sandbox
	var ctx map[string]any
	if j.Context != nil {
		ctx = j.Context.Values
	}

	r.mu.RLock()
	defer r.mu.RUnlock()

	if r.state == nil {
		return JobResult{nil, errors.New("lua state is not initialized")}
	}

	// Execute in sandbox
	value, err := r.sandbox.Execute(r.state, j.Bytecode, ctx)
	return JobResult{value, err}
}

// RunWithContext executes a Lua script with context and timeout
func (r *LuaRunner) RunWithContext(ctx context.Context, bytecode []byte, execCtx *Context, scriptPath string) (any, error) {
	r.mu.RLock()
	if !r.isRunning.Load() {
		r.mu.RUnlock()
		return nil, ErrRunnerClosed
	}
	r.mu.RUnlock()

	// Get a result channel from the pool
	resultChanInterface := resultChanPool.Get()
	resultChan := resultChanInterface.(chan JobResult)

	// Make sure to clear any previous results
	select {
	case <-resultChan:
		// Drain the channel if it has a value
	default:
		// Channel is already empty
	}

	j := job{
		Bytecode:   bytecode,
		Context:    execCtx,
		ScriptPath: scriptPath,
		Result:     resultChan,
	}

	// Submit job with context
	select {
	case r.jobQueue <- j:
		// Job submitted
	case <-ctx.Done():
		// Return the channel to the pool before exiting
		resultChanPool.Put(resultChan)
		return nil, ctx.Err()
	}

	// Wait for result with context
	var result JobResult
	select {
	case result = <-resultChan:
		// Got result
	case <-ctx.Done():
		// Return the channel to the pool before exiting
		resultChanPool.Put(resultChan)
		return nil, ctx.Err()
	}

	// Return the channel to the pool
	resultChanPool.Put(resultChan)

	return result.Value, result.Error
}

// Run executes a Lua script
func (r *LuaRunner) Run(bytecode []byte, execCtx *Context, scriptPath string) (any, error) {
	return r.RunWithContext(context.Background(), bytecode, execCtx, scriptPath)
}

// Close gracefully shuts down the LuaRunner
func (r *LuaRunner) Close() error {
	r.mu.Lock()
	defer r.mu.Unlock()

	if !r.isRunning.Load() {
		return ErrRunnerClosed
	}

	r.isRunning.Store(false)
	close(r.jobQueue)

	// Wait for event loop to finish
	r.wg.Wait()

	return nil
}

// NotifyFileChanged handles file change notifications from watchers
func (r *LuaRunner) NotifyFileChanged(filePath string) bool {
	r.debugLog("File change detected: %s", filePath)

	r.mu.Lock()
	defer r.mu.Unlock()

	// Reset the entire state on file changes
	err := r.initState(false)
	if err != nil {
		r.debugLog("Failed to reinitialize state: %v", err)
		return false
	}

	r.debugLog("State successfully reinitialized")
	return true
}

// ResetModuleCache clears non-core modules from package.loaded
func (r *LuaRunner) ResetModuleCache() {
	if r.moduleLoader != nil {
		r.debugLog("Resetting module cache")
		r.moduleLoader.ResetModules(r.state)
	}
}

// ReloadAllModules reloads all modules into package.loaded
func (r *LuaRunner) ReloadAllModules() error {
	if r.moduleLoader != nil {
		r.debugLog("Reloading all modules")
		return r.moduleLoader.PreloadAllModules(r.state)
	}
	return nil
}

// RefreshModuleByName invalidates a specific module in package.loaded
func (r *LuaRunner) RefreshModuleByName(modName string) bool {
	if r.state != nil {
		r.debugLog("Refreshing module: %s", modName)
		if err := r.state.DoString(`package.loaded["` + modName + `"] = nil`); err != nil {
			return false
		}
		return true
	}
	return false
}

// AddModule adds a module to the sandbox environment
func (r *LuaRunner) AddModule(name string, module any) {
	r.debugLog("Adding module: %s", name)
	r.sandbox.AddModule(name, module)
}

// GetModuleCount returns the number of loaded modules
func (r *LuaRunner) GetModuleCount() int {
	r.mu.RLock()
	defer r.mu.RUnlock()

	count := 0

	// Get module count from Lua
	if r.state != nil {
		// Execute a Lua snippet to count modules
		if res, err := r.state.ExecuteWithResult(`
			local count = 0
			for _ in pairs(package.loaded) do
				count = count + 1
			end
			return count
		`); err == nil {
			if num, ok := res.(float64); ok {
				count = int(num)
			}
		}
	}

	return count
}