#!/usr/bin/env python3
"""Hexview — hex dump viewer with ASCII side panel."""
import argparse, os, sys


def color(text, code):
    return f"\033[{code}m{text}\033[0m" if sys.stdout.isatty() else text


def hex_dump(data, width=16, show_ascii=True, show_offset=True,
             color_ascii=True, group=2):
    result = []
    addr_len = max(4, len(str(len(data) - 1)))
    
    for i in range(0, len(data), width):
        chunk = data[i:i + width]
        line = ""
        
        # Offset
        if show_offset:
            off = color(f"{i:0{addr_len}x}", "36") if color_ascii else f"{i:0{addr_len}x}"
            line += f"{off}  "
        
        # Hex bytes
        hex_parts = []
        for j in range(0, len(chunk), group):
            group_bytes = chunk[j:j + group]
            hex_parts.append(" ".join(f"{b:02x}" for b in group_bytes))
        
        hex_str = " ".join(hex_parts)
        hex_str = color(hex_str, "37") if color_ascii else hex_str
        line += hex_str
        
        # Padding for short lines
        expected = width * 2 + (width // group - 1) * (group * 2 + 1)
        # Calculate required padding
        line += " " * (3 * (width // group) + 1)
        
        # ASCII representation
        if show_ascii:
            line += "  "
            for b in chunk:
                if 32 <= b < 127:
                    char = chr(b)
                    if char in "<>&'\"":
                        char = "."
                    line += color(char, "32") if color_ascii else char
                else:
                    line += color(".", "90") if color_ascii else "."
        
        result.append(line.rstrip())
    
    return "\n".join(result)


def main():
    parser = argparse.ArgumentParser(
        description="Hexview — hex dump viewer",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=(
            "Examples:\n"
            "  hexview file.bin              # Hex dump a file\n"
            "  hexview file.bin --width 32   # 32 bytes per row\n"
            "  hexview file.bin --no-ascii   # Hide ASCII panel\n"
            "  hexview file.bin --raw        # No color, pipe-friendly\n"
        ),
    )
    parser.add_argument("file", help="File to dump")
    parser.add_argument("--width", type=int, default=16,
                        help="Bytes per row (default: 16)")
    parser.add_argument("--no-ascii", action="store_true",
                        help="Hide ASCII representation")
    parser.add_argument("--no-offset", action="store_true",
                        help="Hide offset column")
    parser.add_argument("--no-color", action="store_true",
                        help="Disable color output")
    parser.add_argument("--group", type=int, default=2,
                        help="Bytes per group (default: 2)")
    parser.add_argument("--length", "-n", type=int,
                        help="Number of bytes to show")
    parser.add_argument("--offset", type=lambda x: int(x, 0), default=0,
                        help="Start offset")
    parser.add_argument("--version", action="version",
                        version="hexview 1.0.0")
    
    args = parser.parse_args()
    
    if not os.path.exists(args.file):
        print(f"Error: File '{args.file}' not found", file=sys.stderr)
        sys.exit(1)
    
    try:
        with open(args.file, "rb") as f:
            if args.offset:
                f.seek(args.offset)
            data = f.read(args.length or -1)
    except PermissionError:
        print(f"Error: Permission denied reading '{args.file}'",
              file=sys.stderr)
        sys.exit(1)
    except Exception as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)
    
    if not data:
        print(f"{color('(empty)', '90')}")
        return
    
    show_ascii = not args.no_ascii
    show_offset = not args.no_offset
    use_color = sys.stdout.isatty() and not args.no_color
    
    print(f"File: {args.file}  ({len(data)} bytes)")
    print(f"{color('─' * 60, '90')}")
    
    output = hex_dump(data, width=args.width, show_ascii=show_ascii,
                      show_offset=show_offset, color_ascii=use_color,
                      group=args.group)
    print(output)


if __name__ == "__main__":
    main()