package runner

import (
	"context"
	"errors"
	"path/filepath"
	"runtime"
	"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)

// JobResult represents the result of a Lua script execution
type JobResult struct {
	Value any   // Return value from Lua
	Error error // Error if any
}

// StateWrapper wraps a Lua state with its sandbox
type StateWrapper struct {
	state   *luajit.State // The Lua state
	sandbox *Sandbox      // Associated sandbox
	index   int           // Index for debugging
}

// LuaRunner runs Lua scripts using a pool of Lua states
type LuaRunner struct {
	states       []*StateWrapper     // Pool of Lua states
	stateSem     chan int            // Semaphore with state indexes
	poolSize     int                 // Size of the state pool
	initFunc     StateInitFunc       // Optional function to initialize Lua states
	moduleLoader *NativeModuleLoader // Native module loader for require
	isRunning    atomic.Bool         // Flag indicating if the runner is active
	mu           sync.RWMutex        // Mutex for thread safety
	debug        bool                // Enable debug logging
}

// WithPoolSize sets the state pool size
func WithPoolSize(size int) RunnerOption {
	return func(r *LuaRunner) {
		if size > 0 {
			r.poolSize = 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 with a pool of states
func NewRunner(options ...RunnerOption) (*LuaRunner, error) {
	// Default configuration
	runner := &LuaRunner{
		poolSize: runtime.GOMAXPROCS(0), // Default pool size to number of CPUs
		debug:    false,
	}

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

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

	// Initialize states and semaphore
	runner.states = make([]*StateWrapper, runner.poolSize)
	runner.stateSem = make(chan int, runner.poolSize)

	// Create and initialize all states
	for i := 0; i < runner.poolSize; i++ {
		wrapper, err := runner.initState(i)
		if err != nil {
			runner.Close() // Clean up already created states
			return nil, err
		}

		runner.states[i] = wrapper
		runner.stateSem <- i // Add index to semaphore
	}

	runner.isRunning.Store(true)

	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 creates and initializes a new state
func (r *LuaRunner) initState(index int) (*StateWrapper, error) {
	r.debugLog("Initializing Lua state %d", index)

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

	// Create sandbox
	sandbox := NewSandbox()
	if r.debug {
		sandbox.EnableDebug()
	}

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

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

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

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

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

	r.debugLog("State %d initialization complete", index)

	return &StateWrapper{
		state:   state,
		sandbox: sandbox,
		index:   index,
	}, nil
}

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

	// Create a result channel
	resultChan := make(chan JobResult, 1)

	// Get a state index with timeout
	var stateIndex int
	select {
	case stateIndex = <-r.stateSem:
		// Got a state
	case <-ctx.Done():
		return nil, ctx.Err()
	}

	// Launch a goroutine to execute the job
	go func() {
		// Make sure to return the state to the pool when done
		defer func() {
			// Only return if runner is still open
			if r.isRunning.Load() {
				select {
				case r.stateSem <- stateIndex:
					// State returned to pool
				default:
					// Pool is full or closed (shouldn't happen)
				}
			}
		}()

		// Execute the job
		var result JobResult

		r.mu.RLock()
		state := r.states[stateIndex]
		r.mu.RUnlock()

		if state == nil {
			result = JobResult{nil, errors.New("state is not initialized")}
		} else {
			// Set script directory for module resolution
			if scriptPath != "" {
				r.mu.Lock()
				r.moduleLoader.config.ScriptDir = filepath.Dir(scriptPath)
				r.mu.Unlock()
			}

			// Convert context
			var ctxMap map[string]any
			if execCtx != nil {
				ctxMap = execCtx.Values
			}

			// Execute in sandbox
			value, err := state.sandbox.Execute(state.state, bytecode, ctxMap)
			result = JobResult{value, err}
		}

		// Send result
		select {
		case resultChan <- result:
			// Result sent
		default:
			// Result channel closed or full (shouldn't happen with buffered channel)
		}
	}()

	// Wait for result with context
	select {
	case result := <-resultChan:
		return result.Value, result.Error
	case <-ctx.Done():
		// Note: we can't cancel the Lua execution, but we can stop waiting for it
		// The state will be returned to the pool when the goroutine completes
		return nil, ctx.Err()
	}
}

// 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)

	// Drain the semaphore (non-blocking)
	for {
		select {
		case <-r.stateSem:
			// Drained one slot
		default:
			// Empty
			goto drained
		}
	}
drained:

	// Clean up all states
	for i := 0; i < len(r.states); i++ {
		if r.states[i] != nil {
			r.states[i].state.Cleanup()
			r.states[i].state.Close()
			r.states[i] = nil
		}
	}

	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()

	// Check if runner is closed
	if !r.isRunning.Load() {
		return false
	}

	// Create a new semaphore
	newSem := make(chan int, cap(r.stateSem))

	// Drain the current semaphore (non-blocking)
	for {
		select {
		case <-r.stateSem:
			// Drained one slot
		default:
			// Empty
			goto drained
		}
	}
drained:

	r.stateSem = newSem

	// Reinitialize all states
	success := true
	for i := 0; i < len(r.states); i++ {
		// Clean up old state
		if r.states[i] != nil {
			r.states[i].state.Cleanup()
			r.states[i].state.Close()
		}

		// Initialize new state
		wrapper, err := r.initState(i)
		if err != nil {
			r.debugLog("Failed to reinitialize state %d: %v", i, err)
			success = false
			r.states[i] = nil
			continue
		}

		r.states[i] = wrapper

		// Add to semaphore
		select {
		case newSem <- i:
			// Added to semaphore
		default:
			// Semaphore full (shouldn't happen)
		}
	}

	return success
}

// ResetModuleCache clears non-core modules from package.loaded in all states
func (r *LuaRunner) ResetModuleCache() {
	if r.moduleLoader != nil {
		r.debugLog("Resetting module cache in all states")
		r.mu.RLock()
		defer r.mu.RUnlock()

		for i := 0; i < len(r.states); i++ {
			if r.states[i] != nil && r.states[i].state != nil {
				r.moduleLoader.ResetModules(r.states[i].state)
			}
		}
	}
}

// ReloadAllModules reloads all modules into package.loaded in all states
func (r *LuaRunner) ReloadAllModules() error {
	if r.moduleLoader != nil {
		r.debugLog("Reloading all modules in all states")
		r.mu.RLock()
		defer r.mu.RUnlock()

		for i := 0; i < len(r.states); i++ {
			if r.states[i] != nil && r.states[i].state != nil {
				if err := r.moduleLoader.PreloadAllModules(r.states[i].state); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

// RefreshModuleByName invalidates a specific module in package.loaded in all states
func (r *LuaRunner) RefreshModuleByName(modName string) bool {
	r.mu.RLock()
	defer r.mu.RUnlock()

	success := true
	for i := 0; i < len(r.states); i++ {
		if r.states[i] != nil && r.states[i].state != nil {
			r.debugLog("Refreshing module %s in state %d", modName, i)
			if err := r.states[i].state.DoString(`package.loaded["` + modName + `"] = nil`); err != nil {
				success = false
			}
		}
	}
	return success
}

// AddModule adds a module to all sandbox environments
func (r *LuaRunner) AddModule(name string, module any) {
	r.debugLog("Adding module %s to all sandboxes", name)
	r.mu.RLock()
	defer r.mu.RUnlock()

	for i := 0; i < len(r.states); i++ {
		if r.states[i] != nil && r.states[i].sandbox != nil {
			r.states[i].sandbox.AddModule(name, module)
		}
	}
}

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

	count := 0

	// Get count from the first available state
	for i := 0; i < len(r.states); i++ {
		if r.states[i] != nil && r.states[i].state != nil {
			// Execute a Lua snippet to count modules
			if res, err := r.states[i].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)
				}
			}
			break
		}
	}

	return count
}