Task 017: .AGDA File Format

Understanding the .AGDA File Format

The .AGDA file format is associated with Agda, a dependently typed functional programming language and proof assistant. .AGDA files are plain text files containing Agda source code, structured as modules with declarations for datatypes, record types, function definitions, and other constructs. They are typically written and edited using tools like Emacs or Atom, and they support Unicode characters for mathematical notation. Additionally, .AGDA files can be compiled to generate .AGDAI interface files, which store type-checking results and other metadata to optimize compilation and execution. The .AGDA file itself does not have a binary structure but follows a text-based syntax defined by Agda’s grammar.

Below, I address each part of the task based on the information available and reasonable assumptions about the file system properties of .AGDA files. Since .AGDA files are text-based, their intrinsic file system properties are typical of plain text files, and their content follows Agda’s syntax. The programming classes will focus on reading, writing, and extracting basic file system properties, as the internal structure (e.g., declarations, types) requires parsing Agda’s complex syntax, which is beyond simple file format decoding and typically handled by the Agda compiler.

1. Properties of the .AGDA File Format Intrinsic to Its File System

Based on the nature of .AGDA files as plain text files containing Agda source code, the following properties are intrinsic to their representation in the file system:

• File Extension: .agda
• File Type: Plain text file
• Encoding: Typically UTF-8 to support Unicode characters (common in Agda for mathematical symbols)
• File Size: Variable, depending on the content (size in bytes)
• Creation Date: Timestamp when the file was created
• Modification Date: Timestamp of the last modification
• File Path: Absolute or relative path to the file’s location
• File Permissions: Read, write, and execute permissions (e.g., readable/writable by owner, group, others)
• File Name: Name of the file, typically corresponding to the module name (e.g., Basics.agda for module Introduction.Basics)
• Associated Interface File: Presence of a corresponding .agdai file (if compiled), which stores type-checking results
• MIME Type: text/x-agda (unofficial, as Agda-specific MIME types are not widely standardized)
• Line Endings: Platform-dependent (e.g., LF for Unix, CRLF for Windows)
• File Content Structure: Text-based, containing a single top-level module with Agda declarations (e.g., datatypes, functions, postulates)

These properties focus on file system metadata and basic characteristics, as .AGDA files are text files without a complex binary structure. The content (e.g., declarations, types) is part of Agda’s language syntax, not a file format specification like binary formats (e.g., PDF or JPEG).

2. Python Class for .AGDA File Handling

Below is a Python class that opens, reads, writes, and prints the file system properties of an .AGDA file. Since .AGDA files are text-based, the class focuses on file system metadata rather than parsing Agda’s syntax, which would require a full Agda parser.

import os
import datetime
import mimetypes
import stat

class AgdaFileHandler:
    def __init__(self, file_path):
        self.file_path = file_path
        self.properties = {}
        
    def read_properties(self):
        """Read file system properties of the .AGDA file."""
        try:
            # Check if file exists and has .agda extension
            if not self.file_path.endswith('.agda'):
                raise ValueError("File must have .agda extension")
            if not os.path.exists(self.file_path):
                raise FileNotFoundError(f"File {self.file_path} does not exist")
                
            # Get file stats
            file_stats = os.stat(self.file_path)
            
            # Collect properties
            self.properties = {
                'file_extension': '.agda',
                'file_type': 'Plain text',
                'encoding': 'UTF-8',  # Assumed, as Agda supports Unicode
                'file_size_bytes': file_stats.st_size,
                'creation_date': datetime.datetime.fromtimestamp(file_stats.st_ctime).isoformat(),
                'modification_date': datetime.datetime.fromtimestamp(file_stats.st_mtime).isoformat(),
                'file_path': os.path.abspath(self.file_path),
                'file_permissions': stat.filemode(file_stats.st_mode),
                'file_name': os.path.basename(self.file_path),
                'has_agdai': os.path.exists(self.file_path + 'i'),
                'mime_type': mimetypes.guess_type(self.file_path)[0] or 'text/x-agda',
                'line_endings': self._detect_line_endings()
            }
        except Exception as e:
            print(f"Error reading properties: {e}")
            
    def _detect_line_endings(self):
        """Detect line endings in the file."""
        try:
            with open(self.file_path, 'rb') as f:
                first_line = f.readline()
                if b'\r\n' in first_line:
                    return 'CRLF'
                elif b'\n' in first_line:
                    return 'LF'
                return 'Unknown'
        except:
            return 'Unknown'
            
    def print_properties(self):
        """Print all file system properties."""
        if not self.properties:
            print("No properties available. Call read_properties() first.")
            return
        for key, value in self.properties.items():
            print(f"{key}: {value}")
            
    def read_content(self):
        """Read and return the content of the .AGDA file."""
        try:
            with open(self.file_path, 'r', encoding='utf-8') as f:
                return f.read()
        except Exception as e:
            print(f"Error reading file: {e}")
            return None
            
    def write_content(self, content):
        """Write content to the .AGDA file."""
        try:
            with open(self.file_path, 'w', encoding='utf-8') as f:
                f.write(content)
            print(f"Successfully wrote to {self.file_path}")
            # Update properties after writing
            self.read_properties()
        except Exception as e:
            print(f"Error writing to file: {e}")

# Example usage
if __name__ == "__main__":
    # Example with a sample .agda file
    handler = AgdaFileHandler("example.agda")
    try:
        handler.read_properties()
        handler.print_properties()
        content = handler.read_content()
        if content:
            print("\nFile Content:\n", content)
        # Example write operation
        new_content = "module Example where\npostulate A : Set"
        handler.write_content(new_content)
    except Exception as e:
        print(f"Error: {e}")

Explanation:

• The class reads file system properties using os.stat and other Python utilities.
• It checks for the .agda extension and the existence of a corresponding .agdai file.
• The read_content and write_content methods handle file I/O with UTF-8 encoding.
• The print_properties method displays all collected properties.
• Line endings are detected by reading the file in binary mode.
• Error handling ensures robustness for invalid files or permissions issues.

3. Java Class for .AGDA File Handling

Below is a Java class with similar functionality, focusing on file system properties.

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.nio.file.attribute.*;
import java.util.HashMap;
import java.util.Map;

public class AgdaFileHandler {
    private final String filePath;
    private final Map<String, Object> properties;

    public AgdaFileHandler(String filePath) {
        this.filePath = filePath;
        this.properties = new HashMap<>();
    }

    public void readProperties() throws IOException {
        try {
            Path path = Paths.get(filePath);
            if (!filePath.endsWith(".agda")) {
                throw new IllegalArgumentException("File must have .agda extension");
            }
            if (!Files.exists(path)) {
                throw new FileNotFoundException("File " + filePath + " does not exist");
            }

            BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
            File file = new File(filePath);

            properties.clear();
            properties.put("file_extension", ".agda");
            properties.put("file_type", "Plain text");
            properties.put("encoding", "UTF-8");
            properties.put("file_size_bytes", attrs.size());
            properties.put("creation_date", attrs.creationTime().toString());
            properties.put("modification_date", attrs.lastModifiedTime().toString());
            properties.put("file_path", path.toAbsolutePath().toString());
            properties.put("file_permissions", getPermissions(path));
            properties.put("file_name", path.getFileName().toString());
            properties.put("has_agdai", Files.exists(Paths.get(filePath + "i")));
            properties.put("mime_type", Files.probeContentType(path) != null ? Files.probeContentType(path) : "text/x-agda");
            properties.put("line_endings", detectLineEndings());
        } catch (IOException e) {
            System.err.println("Error reading properties: " + e.getMessage());
            throw e;
        }
    }

    private String getPermissions(Path path) throws IOException {
        PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class);
        return PosixFilePermissions.toString(attrs.permissions());
    }

    private String detectLineEndings() throws IOException {
        try (BufferedReader reader = Files.newBufferedReader(Paths.get(filePath), StandardCharsets.UTF_8)) {
            String line = reader.readLine();
            if (line != null) {
                try (RandomAccessFile raf = new RandomAccessFile(filePath, "r")) {
                    byte[] buffer = new byte[1024];
                    int bytesRead = raf.read(buffer);
                    for (int i = 0; i < bytesRead - 1; i++) {
                        if (buffer[i] == '\r' && buffer[i + 1] == '\n') return "CRLF";
                        if (buffer[i] == '\n') return "LF";
                    }
                }
            }
            return "Unknown";
        }
    }

    public void printProperties() {
        if (properties.isEmpty()) {
            System.out.println("No properties available. Call readProperties() first.");
            return;
        }
        properties.forEach((key, value) -> System.out.println(key + ": " + value));
    }

    public String readContent() throws IOException {
        try {
            return Files.readString(Paths.get(filePath), StandardCharsets.UTF_8);
        } catch (IOException e) {
            System.err.println("Error reading file: " + e.getMessage());
            throw e;
        }
    }

    public void writeContent(String content) throws IOException {
        try {
            Files.writeString(Paths.get(filePath), content, StandardCharsets.UTF_8);
            System.out.println("Successfully wrote to " + filePath);
            readProperties(); // Update properties after writing
        } catch (IOException e) {
            System.err.println("Error writing to file: " + e.getMessage());
            throw e;
        }
    }

    public static void main(String[] args) {
        try {
            AgdaFileHandler handler = new AgdaFileHandler("example.agda");
            handler.readProperties();
            handler.printProperties();
            String content = handler.readContent();
            System.out.println("\nFile Content:\n" + content);
            String newContent = "module Example where\npostulate A : Set";
            handler.writeContent(newContent);
        } catch (IOException e) {
            System.err.println("Error: " + e.getMessage());
        }
    }
}

Explanation:

• Uses Java’s Files and Path APIs to read file system metadata.
• Handles POSIX file permissions where supported, with fallback for non-POSIX systems.
• Reads and writes file content using UTF-8 encoding.
• Detects line endings by reading raw bytes.
• Includes error handling for file operations and invalid extensions.

4. JavaScript Class for .AGDA File Handling

Below is a JavaScript class for Node.js, as browser-based JavaScript has limited file system access.

const fs = require('fs').promises;
const path = require('path');
const mime = require('mime-types');

class AgdaFileHandler {
    constructor(filePath) {
        this.filePath = filePath;
        this.properties = {};
    }

    async readProperties() {
        try {
            if (!this.filePath.endsWith('.agda')) {
                throw new Error('File must have .agda extension');
            }
            if (!(await fs.access(this.filePath).then(() => true).catch(() => false))) {
                throw new Error(`File ${this.filePath} does not exist`);
            }

            const stats = await fs.stat(this.filePath);
            this.properties = {
                file_extension: '.agda',
                file_type: 'Plain text',
                encoding: 'UTF-8',
                file_size_bytes: stats.size,
                creation_date: stats.birthtime.toISOString(),
                modification_date: stats.mtime.toISOString(),
                file_path: path.resolve(this.filePath),
                file_permissions: this.getPermissions(stats),
                file_name: path.basename(this.filePath),
                has_agdai: await fs.access(this.filePath + 'i').then(() => true).catch(() => false),
                mime_type: mime.lookup(this.filePath) || 'text/x-agda',
                line_endings: await this.detectLineEndings()
            };
        } catch (error) {
            console.error(`Error reading properties: ${error.message}`);
            throw error;
        }
    }

    getPermissions(stats) {
        const perms = stats.mode.toString(8).slice(-3);
        return `0${perms}`;
    }

    async detectLineEndings() {
        try {
            const buffer = await fs.readFile(this.filePath);
            const text = buffer.toString('utf8', 0, 1024);
            if (text.includes('\r\n')) return 'CRLF';
            if (text.includes('\n')) return 'LF';
            return 'Unknown';
        } catch {
            return 'Unknown';
        }
    }

    printProperties() {
        if (Object.keys(this.properties).length === 0) {
            console.log('No properties available. Call readProperties() first.');
            return;
        }
        for (const [key, value] of Object.entries(this.properties)) {
            console.log(`${key}: ${value}`);
        }
    }

    async readContent() {
        try {
            return await fs.readFile(this.filePath, 'utf8');
        } catch (error) {
            console.error(`Error reading file: ${error.message}`);
            throw error;
        }
    }

    async writeContent(content) {
        try {
            await fs.writeFile(this.filePath, content, 'utf8');
            console.log(`Successfully wrote to ${this.filePath}`);
            await this.readProperties(); // Update properties
        } catch (error) {
            console.error(`Error writing to file: ${error.message}`);
            throw error;
        }
    }
}

// Example usage
(async () => {
    try {
        const handler = new AgdaFileHandler('example.agda');
        await handler.readProperties();
        handler.printProperties();
        const content = await handler.readContent();
        console.log('\nFile Content:\n', content);
        const newContent = 'module Example where\npostulate A : Set';
        await handler.writeContent(newContent);
    } catch (error) {
        console.error('Error:', error.message);
    }
})();

Explanation:

• Uses Node.js fs.promises for asynchronous file operations.
• Requires the mime-types package for MIME type detection.
• Handles file permissions in octal format and detects line endings.
• Supports UTF-8 encoding for reading and writing.
• Asynchronous methods align with Node.js conventions.

5. C Class for .AGDA File Handling

C does not have classes, so I implement a struct with associated functions. This code assumes a POSIX system for file permissions and timestamps.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>

#define MAX_PATH 1024
#define MAX_CONTENT 4096

typedef struct {
    char file_path[MAX_PATH];
    char file_extension[8];
    char file_type[16];
    char encoding[16];
    long file_size_bytes;
    char creation_date[32];
    char modification_date[32];
    char file_name[MAX_PATH];
    char file_permissions[16];
    int has_agdai;
    char mime_type[32];
    char line_endings[8];
} AgdaFileHandler;

void init_handler(AgdaFileHandler* handler, const char* file_path) {
    strncpy(handler->file_path, file_path, MAX_PATH - 1);
    handler->file_path[MAX_PATH - 1] = '\0';
    strcpy(handler->file_extension, "");
    strcpy(handler->file_type, "");
    strcpy(handler->encoding, "");
    handler->file_size_bytes = 0;
    strcpy(handler->creation_date, "");
    strcpy(handler->modification_date, "");
    strcpy(handler->file_name, "");
    strcpy(handler->file_permissions, "");
    handler->has_agdai = 0;
    strcpy(handler->mime_type, "");
    strcpy(handler->line_endings, "");
}

int read_properties(AgdaFileHandler* handler) {
    if (!strstr(handler->file_path, ".agda")) {
        fprintf(stderr, "Error: File must have .agda extension\n");
        return -1;
    }

    struct stat file_stat;
    if (stat(handler->file_path, &file_stat) != 0) {
        fprintf(stderr, "Error: File %s does not exist (%s)\n", handler->file_path, strerror(errno));
        return -1;
    }

    strcpy(handler->file_extension, ".agda");
    strcpy(handler->file_type, "Plain text");
    strcpy(handler->encoding, "UTF-8");
    handler->file_size_bytes = file_stat.st_size;

    struct tm* tm_info;
    tm_info = localtime(&file_stat.st_ctime);
    strftime(handler->creation_date, 32, "%Y-%m-%dT%H:%M:%S", tm_info);
    tm_info = localtime(&file_stat.st_mtime);
    strftime(handler->modification_date, 32, "%Y-%m-%dT%H:%M:%S", tm_info);

    char* base_name = strrchr(handler->file_path, '/');
    strcpy(handler->file_name, base_name ? base_name + 1 : handler->file_path);

    snprintf(handler->file_permissions, 16, "%o", file_stat.st_mode & 0777);

    char agdai_path[MAX_PATH];
    snprintf(agdai_path, MAX_PATH, "%si", handler->file_path);
    handler->has_agdai = access(agdai_path, F_OK) == 0 ? 1 : 0;

    strcpy(handler->mime_type, "text/x-agda");

    FILE* file = fopen(handler->file_path, "rb");
    if (!file) {
        fprintf(stderr, "Error detecting line endings: %s\n", strerror(errno));
        strcpy(handler->line_endings, "Unknown");
        return -1;
    }
    char buffer[1024];
    size_t bytes = fread(buffer, 1, 1023, file);
    buffer[bytes] = '\0';
    if (strstr(buffer, "\r\n")) strcpy(handler->line_endings, "CRLF");
    else if (strchr(buffer, '\n')) strcpy(handler->line_endings, "LF");
    else strcpy(handler->line_endings, "Unknown");
    fclose(file);

    return 0;
}

void print_properties(AgdaFileHandler* handler) {
    if (handler->file_extension[0] == '\0') {
        printf("No properties available. Call read_properties() first.\n");
        return;
    }
    printf("file_extension: %s\n", handler->file_extension);
    printf("file_type: %s\n", handler->file_type);
    printf("encoding: %s\n", handler->encoding);
    printf("file_size_bytes: %ld\n", handler->file_size_bytes);
    printf("creation_date: %s\n", handler->creation_date);
    printf("modification_date: %s\n", handler->modification_date);
    printf("file_path: %s\n", handler->file_path);
    printf("file_permissions: %s\n", handler->file_permissions);
    printf("file_name: %s\n", handler->file_name);
    printf("has_agdai: %d\n", handler->has_agdai);
    printf("mime_type: %s\n", handler->mime_type);
    printf("line_endings: %s\n", handler->line_endings);
}

int read_content(AgdaFileHandler* handler, char* buffer, size_t max_len) {
    FILE* file = fopen(handler->file_path, "r");
    if (!file) {
        fprintf(stderr, "Error reading file: %s\n", strerror(errno));
        return -1;
    }
    size_t bytes = fread(buffer, 1, max_len - 1, file);
    buffer[bytes] = '\0';
    fclose(file);
    return 0;
}

int write_content(AgdaFileHandler* handler, const char* content) {
    FILE* file = fopen(handler->file_path, "w");
    if (!file) {
        fprintf(stderr, "Error writing to file: %s\n", strerror(errno));
        return -1;
    }
    if (fputs(content, file) == EOF) {
        fprintf(stderr, "Error writing content: %s\n", strerror(errno));
        fclose(file);
        return -1;
    }
    fclose(file);
    printf("Successfully wrote to %s\n", handler->file_path);
    return read_properties(handler); // Update properties
}

int main() {
    AgdaFileHandler handler;
    init_handler(&handler, "example.agda");
    
    if (read_properties(&handler) == 0) {
        print_properties(&handler);
        char content[MAX_CONTENT];
        if (read_content(&handler, content, MAX_CONTENT) == 0) {
            printf("\nFile Content:\n%s\n", content);
        }
        const char* new_content = "module Example where\npostulate A : Set";
        write_content(&handler, new_content);
    }
    return 0;
}

Explanation:

• Uses a struct to mimic a class, with functions for operations.
• Reads file system metadata using POSIX stat and access.
• Handles UTF-8 content and detects line endings.
• Includes error handling for file operations.
• Assumes a fixed buffer size for simplicity; production code would need dynamic allocation.

Notes and Limitations

• File Format Parsing: The classes focus on file system properties because .AGDA files are text-based, and their internal structure (declarations, types) requires an Agda parser, which is complex and typically handled by the Agda compiler. Decoding the content (e.g., extracting module names or declarations) would require integrating an Agda parser or lexer, which is beyond the scope of this task.
• .AGDAI Files: The presence of a corresponding .agdai file is checked, but its content is not parsed, as it is a compiled artifact not meant for direct manipulation.
• Cross-Platform: The C and Java code assume POSIX systems for permissions; Windows would require adjustments (e.g., using Windows API for permissions).
• Error Handling: All implementations include robust error handling for file operations and invalid inputs.
• Dependencies: The JavaScript code requires the mime-types package (npm install mime-types).

If you need deeper parsing of .AGDA content (e.g., extracting module names or declarations), please specify, and I can extend the classes to include basic parsing using regular expressions or suggest integrating an Agda-specific library. Let me know if you want example .AGDA files to test these classes or further refinements

The .AGDA file extension is used for source code files in the Agda programming language, a dependently typed functional programming language and proof assistant. These files are plain text files, typically encoded in UTF-8, containing Agda code. There is no binary structure or "decode" process required beyond standard text reading, as the format is not a structured binary format like those for images or archives. No public specification exists for a binary .AGDA format, and searches for such details yield no results beyond the text-based nature of Agda source files.

The associated .agdai files (interface files generated from .agda source) are serialized and compressed internal data used by the Agda typechecker, but their format is not publicly documented or intended for external parsing/writing. It involves Haskell-based serialization with sharing for efficiency, but no detailed byte-level spec is available to implement decoding or writing in other languages.

Given this, I cannot provide classes to "decode" a non-existent binary format. Instead, I'll describe the basic properties and provide simple classes for reading/writing .AGDA as text files, treating them as standard text.

1. List of properties of the .AGDA file format intrinsic to its file system

Since .AGDA is a text format, its "properties" are those of any text file in a file system. There are no format-specific intrinsic properties like headers or magic numbers. Common file system properties include:

• File extension: .agda (case-insensitive in some systems, but typically lowercase)
• MIME type: text/plain or application/x-agda (not standardized)
• Encoding: UTF-8 (as per Agda documentation, supporting Unicode for symbols)
• Size: Variable, determined by content length
• Creation time (ctime): Timestamp when the file was created
• Modification time (mtime): Timestamp when the file was last modified
• Access time (atime): Timestamp when the file was last accessed
• Permissions: Read/write/execute flags for owner, group, and others (e.g., in UNIX-like systems)
• Owner: User ID of the file owner
• Group: Group ID of the file
• Inode number (on UNIX-like systems): Unique identifier in the file system
• File type: Regular file (not directory or link)
• Content: Agda source code syntax, but this is not a file system property—it's application-level

If "intrinsic to its file system" refers to something else, no specific details were found in searches.

2. Python class for .AGDA files

Since it's text, the class simply opens, reads, and writes the file as text.

import os
import stat
import pwd
import grp
import time

class AgdaFileHandler:
    def __init__(self, filepath):
        self.filepath = filepath
        self.content = None
        self.properties = {}

    def open_and_read(self):
        with open(self.filepath, 'r', encoding='utf-8') as f:
            self.content = f.read()
        self._read_properties()
        return self.content

    def _read_properties(self):
        st = os.stat(self.filepath)
        self.properties = {
            'extension': os.path.splitext(self.filepath)[1],
            'mime_type': 'text/plain',  # Assumed
            'encoding': 'utf-8',
            'size': st.st_size,
            'creation_time': time.ctime(st.st_birthtime if hasattr(st, 'st_birthtime') else st.st_ctime),
            'modification_time': time.ctime(st.st_mtime),
            'access_time': time.ctime(st.st_atime),
            'permissions': stat.filemode(st.st_mode),
            'owner': pwd.getpwuid(st.st_uid).pw_name,
            'group': grp.getgrgid(st.st_gid).gr_name,
            'inode': st.st_ino,
        }

    def write(self, new_content):
        with open(self.filepath, 'w', encoding='utf-8') as f:
            f.write(new_content)
        self.content = new_content
        self._read_properties()

    def get_properties(self):
        return self.properties

3. Java class for .AGDA files

Similar to Python, handling as text with file system properties.

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.nio.file.attribute.*;
import java.util.HashMap;
import java.util.Map;

public class AgdaFileHandler {
    private String filepath;
    private String content;
    private Map<String, Object> properties;

    public AgdaFileHandler(String filepath) {
        this.filepath = filepath;
        this.properties = new HashMap<>();
    }

    public String openAndRead() throws IOException {
        this.content = new String(Files.readAllBytes(Paths.get(filepath)), StandardCharsets.UTF_8);
        readProperties();
        return this.content;
    }

    private void readProperties() throws IOException {
        Path path = Paths.get(filepath);
        BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
        PosixFileAttributes posixAttrs = null;
        try {
            posixAttrs = Files.readAttributes(path, PosixFileAttributes.class);
        } catch (UnsupportedOperationException e) {
            // Posix not supported (e.g., Windows)
        }

        properties.put("extension", filepath.substring(filepath.lastIndexOf('.')));
        properties.put("mime_type", "text/plain"); // Assumed
        properties.put("encoding", "utf-8");
        properties.put("size", attrs.size());
        properties.put("creation_time", attrs.creationTime());
        properties.put("modification_time", attrs.lastModifiedTime());
        properties.put("access_time", attrs.lastAccessTime());
        if (posixAttrs != null) {
            properties.put("permissions", posixAttrs.permissions());
            properties.put("owner", posixAttrs.owner().getName());
            properties.put("group", posixAttrs.group().getName());
        }
        properties.put("inode", attrs.fileKey()); // May be null or system-specific
    }

    public void write(String newContent) throws IOException {
        Files.write(Paths.get(filepath), newContent.getBytes(StandardCharsets.UTF_8));
        this.content = newContent;
        readProperties();
    }

    public Map<String, Object> getProperties() {
        return properties;
    }
}

4. JavaScript class for .AGDA files

Using Node.js for file system access, as JavaScript in browsers can't directly access files.

const fs = require('fs');
const path = require('path');
const os = require('os');

class AgdaFileHandler {
    constructor(filepath) {
        this.filepath = filepath;
        this.content = null;
        this.properties = {};
    }

    openAndRead() {
        this.content = fs.readFileSync(this.filepath, 'utf-8');
        this._readProperties();
        return this.content;
    }

    _readProperties() {
        const st = fs.statSync(this.filepath);
        this.properties = {
            extension: path.extname(this.filepath),
            mime_type: 'text/plain', // Assumed
            encoding: 'utf-8',
            size: st.size,
            creation_time: st.birthtime.toString(),
            modification_time: st.mtime.toString(),
            access_time: st.atime.toString(),
            permissions: (st.mode & 0o777).toString(8), // Octal permissions
            owner: st.uid,
            group: st.gid,
            inode: st.ino,
        };
    }

    write(newContent) {
        fs.writeFileSync(this.filepath, newContent, 'utf-8');
        this.content = newContent;
        this._readProperties();
    }

    getProperties() {
        return this.properties;
    }
}

5. C class for .AGDA files

In C, there's no "class" keyword, but we can use structs and functions to simulate a class-like structure. Handling as text with file system properties.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <time.h>
#include <pwd.h>
#include <grp.h>
#include <unistd.h>

typedef struct {
    char *filepath;
    char *content;
    // Properties as key-value, but for simplicity, use struct fields
    char extension[10];
    char mime_type[20];
    char encoding[10];
    long size;
    char creation_time[30];
    char modification_time[30];
    char access_time[30];
    char permissions[10];
    char owner[256];
    char group[256];
    ino_t inode;
} AgdaFileHandler;

void init_AgdaFileHandler(AgdaFileHandler *handler, const char *filepath) {
    handler->filepath = strdup(filepath);
    handler->content = NULL;
    strcpy(handler->mime_type, "text/plain");
    strcpy(handler->encoding, "utf-8");
    // Extension
    const char *dot = strrchr(filepath, '.');
    if (dot) strcpy(handler->extension, dot);
    else handler->extension[0] = '\0';
}

void open_and_read(AgdaFileHandler *handler) {
    FILE *f = fopen(handler->filepath, "r");
    if (!f) {
        perror("Failed to open file");
        return;
    }
    fseek(f, 0, SEEK_END);
    long len = ftell(f);
    fseek(f, 0, SEEK_SET);
    handler->content = malloc(len + 1);
    fread(handler->content, 1, len, f);
    handler->content[len] = '\0';
    fclose(f);
    read_properties(handler);
}

void read_properties(AgdaFileHandler *handler) {
    struct stat st;
    if (stat(handler->filepath, &st) != 0) {
        perror("stat failed");
        return;
    }
    handler->size = st.st_size;
    strcpy(handler->creation_time, ctime(&st.st_ctime));
    strcpy(handler->modification_time, ctime(&st.st_mtime));
    strcpy(handler->access_time, ctime(&st.st_atime));
    sprintf(handler->permissions, "%o", st.st_mode & 0777);
    struct passwd *pw = getpwuid(st.st_uid);
    strcpy(handler->owner, pw ? pw->pw_name : "unknown");
    struct group *gr = getgrgid(st.st_gid);
    strcpy(handler->group, gr ? gr->gr_name : "unknown");
    handler->inode = st.st_ino;
}

void write(AgdaFileHandler *handler, const char *new_content) {
    FILE *f = fopen(handler->filepath, "w");
    if (!f) {
        perror("Failed to write file");
        return;
    }
    fprintf(f, "%s", new_content);
    fclose(f);
    free(handler->content);
    handler->content = strdup(new_content);
    read_properties(handler);
}

void free_AgdaFileHandler(AgdaFileHandler *handler) {
    free(handler->filepath);
    free(handler->content);
}

// Example usage:
// int main() {
//     AgdaFileHandler handler;
//     init_AgdaFileHandler(&handler, "example.agda");
//     open_and_read(&handler);
//     // Use handler.content and properties
//     write(&handler, "new content");
//     free_AgdaFileHandler(&handler);
//     return 0;
// }