import os
import logging
import io
from typing import Optional
import aiosqlite as sqlite3
from PIL import Image


class MemeUtil:
    """
    Meme Utils
    """

    def __init__(self, constants) -> None:
        self.constants = constants
        self.meme_db_path = os.path.join("/usr/local/share", "sqlite_dbs", "meme.db")

    def is_png(self, buffer: bytes | io.BytesIO) -> bool:
        """
        Check if image (in-memory buffer, or bytes) is a PNG
        Args:
            buffer (bytes|io.BytesIO)
        Returns:
            bool
        """
        # Accepts either bytes or a BytesIO-like object
        if isinstance(buffer, io.BytesIO):
            if hasattr(buffer, "read") and hasattr(buffer, "seek"):
                pos = buffer.tell()
                buffer.seek(0)
                signature = buffer.read(8)
                buffer.seek(pos)
        else:
            signature = buffer[:8]
        return signature == b"\x89PNG\r\n\x1a\n"

    def convert_to_png(self, in_buffer: io.BytesIO) -> bytes:
        """
        Convert an in-memory buffer to PNG
        Args:
            in_buffer (io.BytesIO)
        Returns:
            bytes
        """
        in_buffer.seek(0)
        with Image.open(in_buffer) as im:
            if im.format == "PNG":
                raise ValueError("Already a PNG")
            out_buffer = io.BytesIO()
            im.save(out_buffer, format="PNG")
            out_buffer.seek(0)
        return out_buffer.read()

    async def get_meme_by_id(self, meme_id: int) -> Optional[bytes]:
        """
        Get meme by id
        Args:
            meme_id (int)
        Returns:
            Optional[bytes]
        """
        ret_image: Optional[bytes] = None
        buffer: Optional[io.BytesIO] = None
        async with sqlite3.connect(self.meme_db_path, timeout=5) as db_conn:
            db_conn.row_factory = sqlite3.Row
            query: str = "SELECT image FROM memes WHERE id = ? LIMIT 1"
            async with await db_conn.execute(query, (meme_id,)) as db_cursor:
                result = await db_cursor.fetchone()
                if not result:
                    return None
                buffer = io.BytesIO(result["image"])
                is_png = self.is_png(buffer)
                if not is_png:
                    logging.debug("Converting %s, not detected as PNG", meme_id)
                    ret_image = self.convert_to_png(buffer)
                else:
                    ret_image = result["image"]
                return ret_image

    async def list_memes(self, page: int) -> Optional[list]:
        """
        List memes (paginated)
        Args:
            page (id)
        Returns:
            list
        """
        out_result: list = []
        async with sqlite3.connect(self.meme_db_path, timeout=5) as db_conn:
            db_conn.row_factory = sqlite3.Row
            rows_per_page: int = 10
            offset: int = (page - 1) * rows_per_page
            query: str = "SELECT id, timestamp FROM memes ORDER BY timestamp DESC LIMIT 10 OFFSET ?"
            async with await db_conn.execute(query, (offset,)) as db_cursor:
                results = await db_cursor.fetchall()
                for result in results:
                    result_id = result["id"]
                    result_timestamp = result["timestamp"]
                    out_result.append(
                        {
                            "id": result_id,
                            "timestamp": result_timestamp,
                        }
                    )
        return out_result