/*
 * file-utils.vala
 *
 * File system operations for valaq.
 * This class provides utility functions for file operations.
 */

/**
 * Utility class for file system operations.
 *
 * Provides comprehensive file system functionality including VAPI file discovery,
 * path resolution, validation, and security checks. This class handles
 * the complex task of locating VAPI files across multiple standard directories
 * and provides safe file access with proper validation.
 */
public class FileUtils : Object {
    
    /**
     * Array of VAPI search paths in order of preference.
     *
     * These paths are searched sequentially when resolving VAPI file names.
     * The order is important for precedence - earlier paths have priority.
     */
    private string[] vapi_search_paths;
    
    /**
     * Creates a new FileUtils instance.
     *
     * Initializes the VAPI search paths with standard system directories
     and any additional fallback paths that might exist on the system.
     */
    public FileUtils () {
        // Initialize VAPI search paths
        initialize_vapi_search_paths ();
    }
    
    /**
     * Initializes the VAPI search paths in order of preference.
     */
    private void initialize_vapi_search_paths () {
        vapi_search_paths = new string[0];
        
        // Primary search path
        vapi_search_paths += "/usr/share/vala-0.56/vapi";
        
        // Secondary search path
        vapi_search_paths += "/usr/share/vala/vapi";
        
        // Additional fallback paths (for backward compatibility)
        string[] fallback_paths = {
            "/usr/share/vala-0.54/vapi",
            "/usr/share/vala-0.52/vapi",
            "/usr/local/share/vala/vapi"
        };
        
        foreach (string path in fallback_paths) {
            if (file_exists (path)) {
                vapi_search_paths += path;
            }
        }
    }
    
    /**
     * Gets the VAPI search paths.
     *
     * @return Array of VAPI search paths in order of preference
     */
    public string[] get_vapi_search_paths () {
        return vapi_search_paths;
    }
    
    /**
     * Checks if a file exists.
     *
     * @param path Path to the file
     * @return True if file exists, false otherwise
     */
    public bool file_exists (string path) {
        return File.new_for_path (path).query_exists ();
    }
    
    /**
     * Checks if a path is a VAPI file.
     *
     * Determines if the given path points to a VAPI file by checking
     * the file extension. This is used for filtering and validation.
     *
     * @param path Path to check
     * @return True if path is a VAPI file, false otherwise
     */
    public bool is_vapi_file (string path) {
        return path.has_suffix (".vapi");
    }
    
    /**
     * Finds VAPI files in a directory.
     *
     * Scans the specified directory for files with .vapi extension.
     * Returns full paths to all found VAPI files. Handles directory
     * access errors gracefully and continues operation.
     *
     * @param directory Directory path to search for VAPI files
     * @return Array of VAPI file paths found in directory
     */
    public Gee.ArrayList<string> find_vapi_files (string directory) {
        var vapi_files = new Gee.ArrayList<string> ();
        
        try {
            var dir = File.new_for_path (directory);
            if (!dir.query_exists ()) {
                stderr.printf ("Warning: VAPI directory does not exist: %s\n", directory);
                return vapi_files;
            }
            
            var enumerator = dir.enumerate_children (
                FileAttribute.STANDARD_NAME + "," + FileAttribute.STANDARD_TYPE,
                FileQueryInfoFlags.NONE
            );
            
            FileInfo file_info;
            while ((file_info = enumerator.next_file ()) != null) {
                string filename = file_info.get_name ();
                if (is_vapi_file (filename)) {
                    vapi_files.add (Path.build_filename (directory, filename));
                }
            }
        } catch (Error e) {
            stderr.printf ("Error scanning VAPI directory: %s\n", e.message);
        }
        
        return vapi_files;
    }
    
    /**
     * Finds VAPI files across all search paths.
     *
     * Scans all configured VAPI directories and returns a consolidated
     * list of available VAPI files. Removes duplicates based on basename
     * to avoid showing the same file from multiple directories.
     *
     * @return Array of VAPI file paths with duplicates removed
     */
    public Gee.ArrayList<string> find_all_vapi_files () {
        var all_vapi_files = new Gee.ArrayList<string> ();
        var seen_files = new Gee.HashSet<string> ();
        
        foreach (string search_path in vapi_search_paths) {
            var vapi_files = find_vapi_files (search_path);
            
            foreach (string file_path in vapi_files) {
                var file = File.new_for_path (file_path);
                string basename = file.get_basename ();
                
                // Avoid duplicates by checking basename
                if (!seen_files.contains (basename)) {
                    seen_files.add (basename);
                    all_vapi_files.add (file_path);
                }
            }
        }
        
        return all_vapi_files;
    }
    
    /**
     * Resolves a VAPI file name across all search paths.
     * Supports both basenames (e.g., "zlib.vapi") and names without extension (e.g., "zlib").
     * The first found file is used, with primary search path taking precedence.
     *
     * @param vapi_name Name of the VAPI file (with or without .vapi extension)
     * @return Full path to the VAPI file, or null if not found
     */
    public string? resolve_vapi_file (string vapi_name) {
        // Validate input
        if (vapi_name == "" || vapi_name.strip () == "") {
            return null;
        }
        
        // Check if this is a full path (contains path separators)
        if (vapi_name.contains ("/") || vapi_name.contains ("\\")) {
            // For full paths, we don't resolve through search paths
            // Just check if the file exists as-is
            return file_exists (vapi_name) ? vapi_name : null;
        }
        
        // This is a basename - ensure it has .vapi extension for searching
        string filename = vapi_name;
        if (!filename.has_suffix (".vapi")) {
            filename += ".vapi";
        }
        
        // First, check the current working directory
        string current_dir = Environment.get_current_dir ();
        string current_dir_path = Path.build_filename (current_dir, filename);
        if (file_exists (current_dir_path)) {
            return current_dir_path;
        }
        
        // Then search in all VAPI paths in order of preference
        foreach (string search_path in vapi_search_paths) {
            string full_path = Path.build_filename (search_path, filename);
            if (file_exists (full_path)) {
                return full_path;
            }
        }
        
        return null;
    }
    
    /**
     * Gets information about which search path contains a VAPI file.
     *
     * @param vapi_name Name of the VAPI file (with or without .vapi extension)
     * @return Array containing [search_path, full_path], or null if not found
     */
    public string[]? find_vapi_file_location (string vapi_name) {
        // Ensure the name has .vapi extension
        string filename = vapi_name;
        if (!filename.has_suffix (".vapi")) {
            filename += ".vapi";
        }
        
        // Search in all paths in order of preference
        foreach (string search_path in vapi_search_paths) {
            string full_path = Path.build_filename (search_path, filename);
            if (file_exists (full_path)) {
                return { search_path, full_path };
            }
        }
        
        return null;
    }
    
    /**
     * Gets the default VAPI directory.
     *
     * @return Path to the default VAPI directory (first in search paths)
     */
    public string get_default_vapi_directory () {
        // Return the first search path that exists
        foreach (string path in vapi_search_paths) {
            if (file_exists (path)) {
                return path;
            }
        }
        
        // Default fallback to the primary search path
        return vapi_search_paths.length > 0 ? vapi_search_paths[0] : "/usr/share/vala/vapi";
    }
    
    /**
     * Validates a file path for security and accessibility.
     *
     * Performs security checks to prevent directory traversal attacks
     * and ensures the path is within allowed directories. This is
     * crucial for preventing unauthorized file access.
     *
     * Security measures:
     * - Prevents "../" directory traversal
     * - Restricts access to VAPI directories and current working directory
     * - Allows absolute paths to existing VAPI files
     *
     * @param path Path to validate for security and accessibility
     * @return True if path is safe and allowed, false otherwise
     */
    public bool validate_path (string path) {
        // Check for directory traversal attempts
        if (path.contains ("../") || path.contains ("..\\")) {
            return false;
        }
        
        // Convert to absolute path and check if it's within allowed directories
        var file = File.new_for_path (path);
        string absolute_path;
        
        try {
            absolute_path = file.get_path ();
        } catch (Error e) {
            return false;
        }
        
        // Allow paths in any VAPI search directory or current working directory
        string[] allowed_prefixes = {};
        
        // Add all VAPI search paths
        foreach (string vapi_path in vapi_search_paths) {
            allowed_prefixes += vapi_path;
        }
        
        // Add current working directory
        allowed_prefixes += Environment.get_current_dir ();
        
        foreach (string prefix in allowed_prefixes) {
            if (absolute_path.has_prefix (prefix)) {
                return true;
            }
        }
        
        // Also allow absolute paths to VAPI files directly
        if (absolute_path.has_suffix (".vapi") && file_exists (absolute_path)) {
            return true;
        }
        
        return false;
    }
}