"""
Flask app for YAML file I/O.

Provides web interface for reading and updating YAML file content.
Handles HTTP GET (view) and POST (update) at '/data', and serves index page at '/'.

Author: Isaak Buslovich
Date: 2023-12-21
"""
from flask import Flask, request, jsonify, send_from_directory
import yaml
from pathlib import Path
import logging

app = Flask(__name__, static_folder='.', static_url_path='')
logging.basicConfig(level=logging.INFO)

DATA_FILE = 'data.yaml'


def read_yaml():
    """
    Reads and returns content from the YAML file.

    Returns:
        dict: A dictionary with the key 'text' containing file content.
        None: If an error occurs, along with an error message.
    """
    file_path = Path(DATA_FILE)
    try:
        if not file_path.is_file():
            logging.info("YAML file not found. Returning empty data.")
            return {'text': ''}, None
        with file_path.open() as file:
            data = yaml.safe_load(file) or {}
            return {'text': data.get('text', '')}, None
    except yaml.YAMLError as e:
        logging.error(f"YAML Error: {e}", exc_info=True)
        return None, f"YAML parsing error: {e}"
    except IOError as e:
        logging.error(f"IO Error: {e}", exc_info=True)
        return None, f"File I/O error: {e}"
    except Exception as e:
        logging.error(f"Unexpected Error: {e}", exc_info=True)
        return None, f"Unexpected error: {e}"


def write_yaml(content):
    """
    Writes content to the YAML file.

    Args:
        content (str): The text content to be saved in the file.

    Returns:
        bool: True if the operation was successful, False otherwise.
        None: If successful, or an error message if an error occurs.
    """
    file_path = Path(DATA_FILE)
    try:
        with file_path.open('w') as file:
            yaml.dump({'text': content}, file)
            return True, None
    except Exception as e:
        logging.error(f"Error writing YAML file: {e}", exc_info=True)
        return False, f"Error writing file: {e}"


@app.route('/data', methods=['GET', 'POST'])
def handle_data():
    """
    Handles GET and POST requests to '/data'.
    GET: Returns the content of the YAML file.
    POST: Updates the content of the YAML file.

    Returns:
        JSON response for GET requests.
        Text message for POST requests.
    """
    if request.method == 'GET':
        data, error = read_yaml()
        if error:
            return error, 500
        return jsonify(data), 200
    elif request.method == 'POST':
        content = request.json.get('text', '')
        success, error = write_yaml(content)
        if error:
            return error, 500
        return "File saved successfully", 200


@app.route('/')
def index():
    """
    Serves the main index HTML page.

    Returns:
        HTML content of the main page.
    """
    return send_from_directory('.', 'index.html')


if __name__ == '__main__':
    app.run(debug=True)