utils.py

"""
Utility functions for StudentHub
"""

from datetime import datetime
import json
import csv
import os

class DateTimeEncoder(json.JSONEncoder):
    def default(self, obj):
        """Handles special case of date serialization"""
        if isinstance(obj, datetime):
            return obj.isoformat()
        return super().default(obj)
    
class DateTimeDecoder(json.JSONDecoder):
    def __init__(self, *args, **kwargs):
        super().__init__(object_hook=self.object_hook, *args, **kwargs)

    def object_hook(self, obj):
        """Handles special case of date deserialization, including nested structures"""
        return self._decode_dates(obj)
    
    def _decode_dates(self, value):
        if isinstance(value, dict):
            return {k: self._decode_dates(v) for k, v in value.items()}
        elif isinstance(value, list):
            return [self._decode_dates(item) for item in value]
        elif isinstance(value, str):
            try:
                return datetime.fromisoformat(value)
            except ValueError:
                return value
        else:
            return value

def format_date(date_string):
    """Convert date string to datetime object"""
    # TODO: Add error handling for invalid date formats
    try:
        myDate = datetime.strptime(date_string, "%Y-%m-%d")
        return myDate
    except ValueError:
        return "error"


def calculate_days_remaining(deadline):
    """Calculate days remaining until deadline"""
    today = datetime.now()
    delta = deadline - today
    return delta.days


def validate_grade(grade):
    """Validate if grade is between 0 and 100"""
    if grade < 0 or grade > 100:
        return False
    return True


def save_to_json(data, filename):
    """Save data to JSON file"""
    with open(filename, 'w') as f:
        # NOTE: Edit DateTimeEncoder accordingly if StudentManager contains other non serializable types
        json.dump(data, f, indent=4, cls=DateTimeEncoder)

def load_from_json(filename):
    """Load data from JSON file"""
    try:
        with open(filename, 'r') as f:
            # NOTE: Edit DateTimeDecoder accordingly if StudentManager contains other non serializable types
            return {
                "data": json.load(f, cls=DateTimeDecoder),
                "status": 0
            }
    except FileNotFoundError:
        return {
            "data" : None,
            "status": 1
        }
    except json.JSONDecodeError as e:
        os.remove(filename)
        return {
            "data" : None,
            "status": 2
        }


def get_priority_level(days_remaining):
    """Determine priority based on days remaining"""
    if days_remaining < 0:
        return "OVERDUE"
    elif days_remaining <= 3:
        return "HIGH"
    elif days_remaining <= 7:
        return "MEDIUM"
    else:
        return "LOW"

def export_to_csv(data, filename, headers=None):
    """Export list of dicts to CSV"""
    if not data:
        raise ValueError("No data to export")

    if headers is None:
        headers = list(data[0].keys())

    with open(filename, "w", newline="") as f:
        writer = csv.DictWriter(f, fieldnames=headers)
        writer.writeheader()
        writer.writerows(data)