import pandas as pd
import json
from filelock import FileLock, Timeout
import time

import datetime

"""
TODO change to use new tempate
TODO change names to be more clear
"""

def ReadDatabase(file_path):
    """ 
    Reads the database for which slots are available

    ``REQUIRES``: ``File_Path`` where the file is
    
    ``PROMISES``: ``JSON`` Interview Available Slots

    ``Developed in part by``: Ahmad, Brock

    ``Contact``: ahmad.ahmad1@ucalgary.ca, darkicewolf50@gmail.com

    """

    
    # Define the path to the Excel file and the lock file
    excel_file_path = file_path
    lock_file_path = file_path + ".lock"

    # Retry parameters
    max_retries = 60  # Maximum number of retries if the file is locked
    retry_interval = 0.5  # Wait time (in seconds) between retries

    retries = 0
    while retries < max_retries:
        try:
            # Attempt to acquire a shared read (non-blocking) access
            with FileLock(lock_file_path, timeout=0):  # Non-blocking, checks if the lock exists
                # Load the Excel file into a pandas DataFrame
                df = pd.read_excel(excel_file_path, sheet_name="Interview TimeTable")

                # Initialize the dictionary to store the structured data
                interview_data = {}

                # Group the DataFrame by Date, Start Time, and Slot for organization
                for _, row in df.iterrows():
                    date = str(row['Date']).split(" ")[0]
                    start_time = str(row['Start Time Slot'])
                    slot = int(row['Slot']) if not pd.isna(row['Slot']) else 0

                    # Returns the number of interviewees in the slot; returns 0 if empty
                    interviewee_amount = len(str(row['Interviewee Name (What to call them)']).split()) if str(row['Interviewee Name (What to call them)']) != "nan" else 0

                    # Check if the slot is available for an interviewee to attend
                    available_slots = interviewee_amount != slot
                    if available_slots:
                        # Initialize nested structure if not present
                        if date not in interview_data:
                            interview_data[date] = {}
                        # Add the start time and duration if not present
                        if start_time not in interview_data[date]:
                            interview_data[date][start_time] = {
                                'Meeting Duration': row['Meeting Duration'],
                            }
                return interview_data  # Successfully read the database

        except Timeout:
            # File is locked; wait and retry
            retries += 1
            print(f"File is locked, retrying ({retries}/{max_retries})...")
            time.sleep(retry_interval)

    # If max retries are exceeded, raise an error
    raise RuntimeError("Unable to access the database after multiple attempts due to a file lock.")


# Example usage of the ReadDatabase function
if __name__ == "__main__":
    import datetime
    year_donation = int(str(datetime.datetime.now().year)[2:]) + 1 # gets the last two digits of the current year then adds 1 for the current season
    # name based off the 2025 naming system
    # Define the path to the Excel file and the lock file
    file_name = f"../Interviews/OR{year_donation}-L-Interview Data.xlsx"
    try:
        data = ReadDatabase(file_name)
        print(json.dumps(data, indent=4))
    except RuntimeError as e:
        print(e)