<?php

namespace KTXC\Module;

/**
 * Custom autoloader for modules that allows PascalCase namespaces
 * with lowercase folder names.
 * 
 * This breaks from PSR-4 convention to allow:
 * - Folder: modules/contacts_manager/
 * - Namespace: KTXM\ContactsManager\
 * 
 * The autoloader scans lazily - only when a KTXM class is first requested.
 */
class ModuleAutoloader
{
    private string $modulesRoot;
    private array $namespaceMap = [];
    private bool $scanned = false;
    
    public function __construct(string $modulesRoot)
    {
        $this->modulesRoot = rtrim($modulesRoot, '/');
    }
    
    /**
     * Register the autoloader
     */
    public function register(): void
    {
        spl_autoload_register([$this, 'loadClass']);
    }
    
    /**
     * Unregister the autoloader
     */
    public function unregister(): void
    {
        spl_autoload_unregister([$this, 'loadClass']);
    }
    
    /**
     * Scan the modules directory and build a map of namespaces to folder paths
     * This is called lazily on the first KTXM class request
     */
    private function scan(): void
    {
        if ($this->scanned) {
            return;
        }
        
        $this->namespaceMap = [];
        
        if (!is_dir($this->modulesRoot)) {
            $this->scanned = true;
            return;
        }
        
        $moduleDirs = glob($this->modulesRoot . '/*', GLOB_ONLYDIR);
        foreach ($moduleDirs as $moduleDir) {
            $moduleFile = $moduleDir . '/lib/Module.php';
            if (!file_exists($moduleFile)) {
                continue;
            }
            
            // Extract the namespace from Module.php
            $namespace = $this->extractNamespace($moduleFile);
            if ($namespace) {
                $this->namespaceMap[$namespace] = basename($moduleDir);
            }
        }
        
        $this->scanned = true;
    }
    
    /**
     * Load a class by its fully qualified name
     * 
     * @param string $className Fully qualified class name (e.g., KTXM\ContactsManager\Module)
     * @return bool True if the class was loaded, false otherwise
     */
    public function loadClass(string $className): bool
    {
        try {
            // Only handle classes in the KTXM namespace
            if (!str_starts_with($className, 'KTXM\\')) {
                return false;
            }
            
            // Extract the namespace segment (e.g., ContactsManager from KTXM\ContactsManager\Module)
            $parts = explode('\\', $className);
            if (count($parts) < 2) {
                $this->logError("Invalid class name format: $className (expected at least 2 namespace parts)");
                return false;
            }
            
            $namespaceSegment = $parts[1];
            
            // Check if we already have a mapping for this namespace
            if (!isset($this->namespaceMap[$namespaceSegment])) {
                // Scan only if we haven't scanned yet (this happens once, on first module access)
                if (!$this->scanned) {
                    $this->scan();
                    
                    // Check again after scanning
                    if (!isset($this->namespaceMap[$namespaceSegment])) {
                        $this->logError("No module found for namespace segment: $namespaceSegment (class: $className)");
                        return false;
                    }
                } else {
                    $this->logError("Module not found after scan: $namespaceSegment (class: $className)");
                    return false;
                }
            }
            
            $folderName = $this->namespaceMap[$namespaceSegment];
            
            // Reconstruct the relative path
            // KTXM\ContactsManager\Module -> contacts_manager/lib/Module.php
            // KTXM\ContactsManager\Something -> contacts_manager/lib/Something.php
            $relativePath = 'lib/' . implode('/', array_slice($parts, 2)) . '.php';
            $filePath = $this->modulesRoot . '/' . $folderName . '/' . $relativePath;
            
            if (file_exists($filePath)) {
                require_once $filePath;
                return true;
            }
            
            $this->logError("File not found for class $className at path: $filePath");
            return false;
            
        } catch (\Throwable $e) {
            $this->logError("Exception in ModuleAutoloader while loading $className: " . $e->getMessage(), [
                'exception' => $e,
                'file' => $e->getFile(),
                'line' => $e->getLine(),
            ]);
            return false;
        }
    }
    
    /**
     * Log an error from the autoloader
     * 
     * @param string $message Error message
     * @param array $context Additional context
     */
    private function logError(string $message, array $context = []): void
    {
        // Log to PHP error log
        error_log('[ModuleAutoloader] ' . $message);
        
        if (!empty($context)) {
            error_log('[ModuleAutoloader Context] ' . json_encode($context));
        }
    }
    
    /**
     * Extract namespace from a Module.php file
     * 
     * @param string $filePath Path to the Module.php file (at modules/{handle}/lib/Module.php)
     * @return string|null The namespace segment (e.g., 'ContactsManager')
     */
    private function extractNamespace(string $filePath): ?string
    {
        if (!file_exists($filePath)) {
            return null;
        }
        
        $content = file_get_contents($filePath);
        if ($content === false) {
            return null;
        }
        
        // Match namespace declaration: namespace KTXM\<Namespace>;
        if (preg_match('/^\s*namespace\s+KTXM\\\\([a-zA-Z0-9_]+)\s*;/m', $content, $matches)) {
            return $matches[1];
        }
        
        return null;
    }
}