from __future__ import annotations
from pathlib import Path
from typing import List, Tuple
import zipfile
import imghdr
import nibabel as nib


class FileValidator:
    # Supported file extensions and their descriptions
    SUPPORTED_EXTENSIONS = {
        # Images
        ".jpg": "JPEG image",
        ".jpeg": "JPEG image",
        ".png": "PNG image",
        ".tif": "TIFF image",
        ".tiff": "TIFF image",
        ".webp": "WebP image",
        ".bmp": "Bitmap image",
        ".gif": "GIF image",
        # Medical formats
        ".nii": "NIfTI image",
        ".nii.gz": "Compressed NIfTI image",
        ".dcm": "DICOM image",
        # Video
        ".mp4": "MP4 video",
        ".mov": "QuickTime video",
        ".webm": "WebM video",
        ".mkv": "Matroska video",
        # Audio
        ".mp3": "MP3 audio",
        ".wav": "WAV audio",
        ".ogg": "Ogg audio",
        ".flac": "FLAC audio",
        ".m4a": "M4A audio",
        # Documents
        ".pdf": "PDF document",
        # Directories
        "dir": "Directory (for DICOM series)",
        # Archives
        ".zip": "ZIP archive (for DICOM series)",
    }

    NON_IMAGE_EXTENSIONS = {
        ".mp4", ".mov", ".webm", ".mkv",
        ".mp3", ".wav", ".ogg", ".flac", ".m4a",
        ".pdf",
    }

    @classmethod
    def validate_files(cls, paths: List[str]) -> Tuple[List[str], List[str]]:
        """
        Validate a list of file paths.
        Returns (valid_paths, error_messages)
        """
        valid_paths = []
        errors = []

        for path in paths:
            if not path:
                continue

            try:
                p = Path(path)

                # Check if path exists
                if not p.exists():
                    errors.append(f"File not found: {path}")
                    continue

                # Handle ZIP files first (potential DICOM archives)
                if p.suffix.lower() == ".zip":
                    try:
                        with zipfile.ZipFile(p) as zf:
                            # Check if zip contains .dcm files
                            has_dicom = any(
                                name.lower().endswith(".dcm") for name in zf.namelist()
                            )
                            if has_dicom:
                                valid_paths.append(path)
                                continue
                            else:
                                errors.append(
                                    f"ZIP file contains no DICOM files: {path}"
                                )
                                continue
                    except Exception as e:
                        errors.append(f"Invalid ZIP file {path}: {str(e)}")
                        continue

                # Handle directories
                if p.is_dir():
                    # Use _is_dicom_file for better validation
                    if any(cls._is_dicom_file(f) for f in p.glob("*")):
                        valid_paths.append(path)
                    else:
                        errors.append(
                            f"Directory contains no valid DICOM files: {path}"
                        )
                    continue

                # For single DICOM files, use proper validation
                if p.suffix.lower() == ".dcm" or cls._is_dicom_file(p):
                    valid_paths.append(path)
                    continue

                # Check file extension - Fix NIfTI handling
                ext = p.suffix.lower()
                name = p.name.lower()

                # Handle compound extensions
                if name.endswith(".nii.gz"):
                    ext = ".nii.gz"
                elif ext == ".gz" and p.stem.lower().endswith(".nii"):
                    ext = ".nii.gz"
                elif name.endswith(".nii"):
                    ext = ".nii"

                # Special validation for NIfTI files
                if ext in [".nii", ".nii.gz"]:
                    try:
                        img = nib.load(str(p))
                        img.header  # Try to access header to verify file
                        valid_paths.append(path)
                    except Exception as e:
                        errors.append(f"Invalid NIfTI file {path}: {str(e)}")
                    continue

                # Check file extension
                if ext not in cls.SUPPORTED_EXTENSIONS:
                    errors.append(
                        f"Unsupported file type: {path}\n"
                        f"Supported formats: {', '.join(cls.SUPPORTED_EXTENSIONS.keys())}"
                    )
                    continue

                # Additional validation for image files
                if ext in [".jpg", ".jpeg", ".png", ".tif", ".tiff"]:
                    img_type = imghdr.what(path)
                    if not img_type:
                        errors.append(f"Invalid or corrupted image file: {path}")
                        continue

                # Non-image media (video/audio/pdf) skips imghdr — just accept
                # the file if its extension is on the known list.
                valid_paths.append(path)

            except Exception as e:
                errors.append(f"Error processing {path}: {str(e)}")

        return valid_paths, errors

    @classmethod
    def _is_dicom_file(cls, path: Path) -> bool:
        """Check if file is DICOM by extension or DICM magic number"""
        if path.suffix.lower() == ".dcm":
            return True
        try:
            with open(path, "rb") as f:
                f.seek(128)
                return f.read(4) == b"DICM"
        except Exception:
            return False

    @classmethod
    def get_supported_formats_md(cls) -> str:
        """Return markdown-formatted string of supported formats"""
        md = "**Supported File Formats:**\n\n"
        for ext, desc in cls.SUPPORTED_EXTENSIONS.items():
            md += f"- `{ext}`: {desc}\n"
        return md