/// Detect if data is binary or text
/// Returns true if data is likely binary, false if likely text
pub fn is_binary(data: &[u8]) -> bool {
    if data.is_empty() {
        return false;
    }
    
    // First check for known binary file signatures
    if has_binary_signature(data) {
        return true;
    }
    
    // Check for UTF-16 BOM (text)
    if data.len() >= 2 {
        if (data[0] == 0xFF && data[1] == 0xFE) || (data[0] == 0xFE && data[1] == 0xFF) {
            return false; // UTF-16 with BOM is text
        }
    }
    
    // Check for UTF-8 BOM (text)
    if data.len() >= 3 && data[0] == 0xEF && data[1] == 0xBB && data[2] == 0xBF {
        return false; // UTF-8 with BOM is text
    }
    
    // Check if it's valid UTF-8
    if std::str::from_utf8(data).is_ok() {
        // Valid UTF-8, check printable character ratio
        return calculate_printable_ratio(data) < 0.7;
    }
    
    // Not valid UTF-8, check if it might be UTF-16 without BOM
    if looks_like_utf16(data) {
        return false; // Likely UTF-16 text
    }
    
    // Check for TAR format (special case with no magic number)
    if looks_like_tar(data) {
        return true;
    }
    
    // Final fallback: check printable character ratio
    // For 1KB of random data, we expect very few printable characters
    calculate_printable_ratio(data) < 0.7
}

/// Check for known binary file signatures
fn has_binary_signature(data: &[u8]) -> bool {
    // Define binary file signatures with their minimum required lengths
    let signatures: &[(&[u8], usize)] = &[
        // Image formats
        (&[0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A], 8), // PNG
        (&[0xFF, 0xD8, 0xFF], 3), // JPEG (various subtypes)
        (&[0x47, 0x49, 0x46, 0x38, 0x37, 0x61], 6), // GIF87a
        (&[0x47, 0x49, 0x46, 0x38, 0x39, 0x61], 6), // GIF89a
        (&[0x42, 0x4D], 2), // BMP
        (&[0x00, 0x00, 0x01, 0x00], 4), // ICO
        (&[0x49, 0x49, 0x2A, 0x00], 4), // TIFF (little endian)
        (&[0x4D, 0x4D, 0x00, 0x2A], 4), // TIFF (big endian)
        (&[0x52, 0x49, 0x46, 0x46], 4), // WebP (RIFF container)
        (&[0x00, 0x00, 0x00, 0x0C, 0x6A, 0x50, 0x20, 0x20], 8), // JPEG 2000
        
        // Audio/Video formats
        (&[0x49, 0x44, 0x33], 3), // MP3 with ID3v2
        (&[0xFF, 0xFB], 2), // MP3
        (&[0xFF, 0xF3], 2), // MP3
        (&[0xFF, 0xF2], 2), // MP3
        (&[0x4F, 0x67, 0x67, 0x53], 4), // OGG
        (&[0x66, 0x74, 0x79, 0x70], 4), // MP4/M4A/MOV (at offset 4)
        (&[0x52, 0x49, 0x46, 0x46], 4), // WAV/AVI (RIFF)
        (&[0x46, 0x4C, 0x56], 3), // FLV
        (&[0x1A, 0x45, 0xDF, 0xA3], 4), // MKV/WebM
        
        // Archive formats
        (&[0x50, 0x4B, 0x03, 0x04], 4), // ZIP
        (&[0x50, 0x4B, 0x05, 0x06], 4), // ZIP (empty)
        (&[0x50, 0x4B, 0x07, 0x08], 4), // ZIP (spanned)
        (&[0x52, 0x61, 0x72, 0x21, 0x1A, 0x07, 0x00], 7), // RAR v1.5+
        (&[0x52, 0x61, 0x72, 0x21, 0x1A, 0x07, 0x01, 0x00], 8), // RAR v5.0+
        (&[0x1F, 0x8B], 2), // GZIP
        (&[0x42, 0x5A, 0x68], 3), // BZIP2
        (&[0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00], 6), // XZ
        (&[0x28, 0xB5, 0x2F, 0xFD], 4), // Zstandard
        (&[0x04, 0x22, 0x4D, 0x18], 4), // LZ4
        (&[0x1F, 0x9D], 2), // LZW compressed
        (&[0x1F, 0xA0], 2), // LZH compressed
        (&[0x37, 0x7A, 0xBC, 0xAF, 0x27, 0x1C], 6), // 7-Zip
        
        // Document formats
        (&[0x25, 0x50, 0x44, 0x46], 4), // PDF
        (&[0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1], 8), // MS Office (OLE)
        (&[0x50, 0x4B, 0x03, 0x04], 4), // Office Open XML (also ZIP)
        (&[0x7B, 0x5C, 0x72, 0x74, 0x66], 5), // RTF
        
        // Executables and object files
        (&[0x7F, 0x45, 0x4C, 0x46], 4), // ELF
        (&[0x4D, 0x5A], 2), // Windows PE/DOS
        (&[0xCA, 0xFE, 0xBA, 0xBE], 4), // Mach-O (big endian)
        (&[0xFE, 0xED, 0xFA, 0xCE], 4), // Mach-O 32-bit (little endian)
        (&[0xFE, 0xED, 0xFA, 0xCF], 4), // Mach-O 64-bit (little endian)
        (&[0xCE, 0xFA, 0xED, 0xFE], 4), // Mach-O 32-bit (big endian)
        (&[0xCF, 0xFA, 0xED, 0xFE], 4), // Mach-O 64-bit (big endian)
        (&[0xCA, 0xFE, 0xBA, 0xBE], 4), // Java class file
        (&[0xDE, 0xC0, 0x17, 0x0B], 4), // Dalvik executable
        
        // Database formats
        (&[0x53, 0x51, 0x4C, 0x69, 0x74, 0x65, 0x20, 0x66, 0x6F, 0x72, 0x6D, 0x61, 0x74, 0x20, 0x33, 0x00], 16), // SQLite
        (&[0x00, 0x01, 0x00, 0x00], 4), // Palm Database
        
        // Font formats
        (&[0x00, 0x01, 0x00, 0x00, 0x00], 5), // TrueType
        (&[0x4F, 0x54, 0x54, 0x4F], 4), // OpenType
        (&[0x77, 0x4F, 0x46, 0x46], 4), // WOFF
        (&[0x77, 0x4F, 0x46, 0x32], 4), // WOFF2
        
        // Virtual machine formats
        (&[0x76, 0x6D, 0x64, 0x6B], 4), // VMDK
        (&[0x3C, 0x3C, 0x3C, 0x20, 0x4F, 0x72, 0x61, 0x63, 0x6C, 0x65, 0x20, 0x56, 0x4D, 0x20, 0x56, 0x69, 0x72, 0x74, 0x75, 0x61, 0x6C, 0x42, 0x6F, 0x78, 0x20, 0x44, 0x69, 0x73, 0x6B, 0x20, 0x49, 0x6D, 0x61, 0x67, 0x65, 0x20, 0x3E, 0x3E, 0x3E], 39), // VirtualBox VDI
        
        // Disk image formats
        (&[0xEB, 0x3C, 0x90], 3), // FAT12/16/32
        (&[0xEB, 0x58, 0x90], 3), // FAT32
        (&[0x55, 0xAA], 2), // Boot sector (at offset 510)
        
        // Other binary formats
        (&[0x21, 0x3C, 0x61, 0x72, 0x63, 0x68, 0x3E, 0x0A], 8), // AR archive
        (&[0x78, 0x01], 2), // zlib (default compression)
        (&[0x78, 0x9C], 2), // zlib (best compression)
        (&[0x78, 0xDA], 2), // zlib (fast compression)
        (&[0x62, 0x76, 0x78, 0x32], 4), // LZFSE
    ];
    
    for (signature, min_len) in signatures {
        if data.len() >= *min_len && data.starts_with(signature) {
            return true;
        }
    }
    
    // Special case: check for ftyp box in MP4/MOV files (at offset 4)
    if data.len() >= 8 && &data[4..8] == b"ftyp" {
        return true;
    }
    
    false
}

/// Check if data looks like UTF-16 without BOM
fn looks_like_utf16(data: &[u8]) -> bool {
    if data.len() < 4 || data.len() % 2 != 0 {
        return false;
    }
    
    let mut zero_count = 0;
    let pairs = data.len() / 2;
    
    // Check if every other byte is zero (indicating UTF-16)
    for i in 0..pairs {
        if data[i * 2 + 1] == 0 {
            zero_count += 1;
        }
    }
    
    // If more than 50% of odd positions are zero, might be UTF-16
    zero_count as f64 / pairs as f64 > 0.5
}

/// Check if data looks like a TAR archive
fn looks_like_tar(data: &[u8]) -> bool {
    if data.len() < 512 {
        return false;
    }
    
    // TAR header structure validation
    // Filename should not start with null
    if data[0] == 0 {
        return false;
    }
    
    // Check file mode field (should be octal digits)
    for i in 100..108 {
        if data[i] != 0 && (data[i] < b'0' || data[i] > b'7') && data[i] != b' ' {
            return false;
        }
    }
    
    // Check checksum field (should be octal digits or spaces)
    for i in 148..156 {
        if data[i] != 0 && (data[i] < b'0' || data[i] > b'7') && data[i] != b' ' {
            return false;
        }
    }
    
    // Check magic field for POSIX TAR
    if data.len() >= 265 {
        let magic = &data[257..262];
        if magic == b"ustar" {
            return true;
        }
    }
    
    // Additional heuristic: check if the structure looks reasonable
    let has_reasonable_structure = 
        data[0] != 0 && // Filename starts
        data[100..108].iter().all(|&b| b == 0 || (b >= b'0' && b <= b'7') || b == b' '); // Mode field
    
    has_reasonable_structure
}

/// Calculate the ratio of printable characters in the data
fn calculate_printable_ratio(data: &[u8]) -> f64 {
    let printable_count = data.iter().filter(|&&b| {
        b.is_ascii_graphic() || b.is_ascii_whitespace()
    }).count();
    
    printable_count as f64 / data.len() as f64
}