import pandas as pd
import random
from collections import defaultdict

TIME_SLOTS = ["9:00-10:30", "10:30-12:00", "12:00-1:30", "1:30-3:00"]
DAYS = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]

def generate_timetable(courses_file, rooms_file):
    courses_df = pd.read_csv(courses_file, skipinitialspace=True)
    courses_df.columns = courses_df.columns.str.strip()
    
    rooms_df = pd.read_csv(rooms_file, skipinitialspace=True)
    rooms_df.columns = rooms_df.columns.str.strip()
    rooms_list = rooms_df["Room"].tolist()
    
    timetable_dict = {}
    
    for cls in courses_df["Class"].unique():
        cls_courses = courses_df[courses_df["Class"] == cls].copy()
        
        # Prepare empty timetable
        timetable = {day: {slot: None for slot in TIME_SLOTS} for day in DAYS}
        
        # Keep track of teacher and room occupancy to avoid conflicts
        teacher_schedule = {day: [] for day in DAYS}
        room_schedule = {day: [] for day in DAYS}
        
        for idx, row in cls_courses.iterrows():
            course = row["Course"]
            hours = int(row["Hours"])
            teacher = row["Teacher"]
            
            # How many 1.5-hour slots required
            slots_needed = hours // 1.5
            if hours % 1.5 != 0:
                slots_needed += 1
            
            slots_assigned = 0
            
            attempts = 0
            while slots_assigned < slots_needed and attempts < 100:
                day = random.choice(DAYS)
                slot = random.choice(TIME_SLOTS)
                
                # Check conflicts
                if timetable[day][slot] is None and teacher not in teacher_schedule[day] and len(room_schedule[day]) < len(rooms_list):
                    room = random.choice([r for r in rooms_list if r not in room_schedule[day]])
                    
                    timetable[day][slot] = {
                        "Course": course,
                        "Teacher": teacher,
                        "Room": room
                    }
                    teacher_schedule[day].append(teacher)
                    room_schedule[day].append(room)
                    slots_assigned += 1
                
                attempts += 1
        
        timetable_dict[cls] = timetable
    
    return timetable_dict