# src/chat_helpers.py
"""URL extraction, message/upload validation, request parsing."""

import re
import os
import json
import logging
from fastapi import HTTPException
from fastapi import UploadFile
from typing import List

logger = logging.getLogger(__name__)


def extract_urls(text: str) -> List[str]:
    """Extract URLs from text using regex pattern."""
    url_pattern = r'https?://[^\s<>"{}|\\^`\[\]]+'
    urls = re.findall(url_pattern, text)
    cleaned_urls = []
    for url in urls:
        url = re.sub(r'[.,;:!?\)]+$', '', url)
        cleaned_urls.append(url)
    return cleaned_urls


def validate_message(message: str) -> str:
    """Validate message input."""
    if not message:
        raise HTTPException(status_code=400, detail="Message is required")

    message = message.strip()
    if len(message) == 0:
        raise HTTPException(status_code=400, detail="Message cannot be empty")

    if len(message) > 50000:
        raise HTTPException(status_code=400, detail="Message exceeds maximum length")

    return message


def validate_file_upload(file: UploadFile) -> UploadFile:
    """Validate uploaded file meets requirements."""
    if not file or not file.filename:
        raise HTTPException(
            status_code=400,
            detail={
                "error": "INVALID_FILE",
                "message": "No file uploaded or invalid filename"
            }
        )

    try:
        file.file.seek(0, 2)
        file_size = file.file.tell()
        file.file.seek(0)

        if file_size == 0:
            raise HTTPException(
                status_code=400,
                detail={
                    "error": "EMPTY_FILE",
                    "message": "File is empty"
                }
            )

        if file_size > 10 * 1024 * 1024:
            raise HTTPException(
                status_code=400,
                detail={
                    "error": "FILE_TOO_LARGE",
                    "message": "File size exceeds 10MB limit"
                }
            )
    except IOError as e:
        logger.error(f"Error reading file size for {file.filename}: {e}")
        raise HTTPException(
            status_code=500,
            detail={
                "error": "FILE_READ_ERROR",
                "message": "Error reading uploaded file"
            }
        )

    allowed_extensions = {'.txt', '.py', '.html', '.md', '.json', '.csv', '.js',
                         '.png', '.jpg', '.jpeg', '.gif', '.bmp', '.webp', '.pdf',
                         '.webm', '.wav', '.mp3', '.m4a', '.ogg'}

    _, ext = os.path.splitext(file.filename.lower())

    if ext not in allowed_extensions:
        raise HTTPException(
            status_code=400,
            detail={
                "error": "UNSUPPORTED_FILE_TYPE",
                "message": f"File type '{ext}' not allowed",
                "allowed_types": sorted(allowed_extensions)
            }
        )

    return file


def coerce_message_and_session(req_json: dict | None, message: str | None,
                               session: str | None, session_manager,
                               allow_empty: bool = False):
    """Extract message and session from request, with validation.

    If allow_empty=True (e.g. attachment-only sends), the message-required
    check is skipped and an empty/whitespace message is normalized to "".
    """
    try:
        if message is None or session is None:
            if req_json is None:
                raise HTTPException(
                    status_code=400,
                    detail={
                        "error": "MISSING_PARAMETERS",
                        "message": "Missing 'message' and/or 'session' in request"
                    }
                )
            message = message or req_json.get("message")
            session = session or req_json.get("session")

        if allow_empty and (message is None or not str(message).strip()):
            message = ""
        else:
            message = validate_message(message)

        if not session:
            raise HTTPException(
                status_code=400,
                detail={
                    "error": "VALIDATION_ERROR",
                    "message": "Session ID is required"
                }
            )
        try:
            session_manager.get_session(session)
        except KeyError:
            raise HTTPException(
                status_code=404,
                detail={
                    "error": "SESSION_NOT_FOUND",
                    "message": f"Session '{session}' not found"
                }
            )

        return message, session
    except HTTPException:
        raise
    except json.JSONDecodeError as e:
        logger.error(f"JSON decode error: {e}")
        raise HTTPException(
            status_code=400,
            detail={
                "error": "INVALID_JSON",
                "message": "Invalid JSON in request body"
            }
        )
    except Exception as e:
        logger.error(f"Unexpected error in coerce_message_and_session: {e}")
        raise HTTPException(
            status_code=400,
            detail={
                "error": "REQUEST_PROCESSING_ERROR",
                "message": "Error processing request"
            }
        )