"""
VTT chunk reassembly logic.
"""

import os
from typing import List
from pathlib import Path
from vtt_utils import VTTFile, Subtitle


class VTTReassembler:
    """Reassembles translated VTT chunks into a single file."""

    @staticmethod
    def reassemble(chunks: List[VTTFile], original_filename: str,
                   output_dir: str) -> str:
        """
        Reassemble translated chunks into a single VTT file.

        Args:
            chunks: List of translated VTTFile chunks
            original_filename: Original filename (without path)
            output_dir: Directory to save the reassembled file

        Returns:
            Path to the output file
        """
        # Combine all subtitles from all chunks
        all_subtitles: List[Subtitle] = []
        for chunk in chunks:
            all_subtitles.extend(chunk.subtitles)

        # Create new VTT file
        final_vtt = VTTFile.__new__(VTTFile)
        final_vtt.filepath = ""
        final_vtt.subtitles = all_subtitles

        # Generate output filename
        name_without_ext = os.path.splitext(original_filename)[0]
        output_filename = f"{name_without_ext}-EN.vtt"
        output_path = os.path.join(output_dir, output_filename)

        # Save to disk
        final_vtt.save(output_path)

        return output_path

    @staticmethod
    def get_output_filename(original_filename: str) -> str:
        """
        Generate output filename from original filename.

        Args:
            original_filename: Original VTT filename

        Returns:
            Output filename with '-EN' suffix
        """
        name_without_ext = os.path.splitext(original_filename)[0]
        return f"{name_without_ext}-EN.vtt"