from sqlmodel import SQLModel, Field
from datetime import datetime
import pandas as pd
from fastapi import FastAPI

# HeroMeeting has a nullable datetime field called "time"
class HeroMeeting(SQLModel):
    id : int | None = Field(primary_key=True, default=None)
    name : str = Field(max_length=255, default=None)
    time : datetime | None = Field(default=None)

app = FastAPI()

# Create a list of HeroMeeting entries, one of which has datetime set to None
hero_meetings = [
    {"name": "Cape Repair Workshop", "time": datetime(day=7, month=2, year=2022)},
    {"name": "Night Owl Patrol", "time": datetime(day=10, month=2, year=2022)},
    {"name": "Budget Villain Confrontation", "time": datetime(day=12, month=2, year=2022)},
    {"name": "Secret Lair Lease Inspection", "time": datetime(day=15, month=2, year=2022)},
    {"name": "Moral Ambiguity Training", "time": datetime(day=18, month=2, year=2022)},
    {"name": "Bootleg Justice League AGM", "time": datetime(day=20, month=2, year=2022)},
    {"name": "Midnight Mask Exchange", "time": None},
]

# Convert list of HeroMeeting entries into a Pandas DataFrame and back
hero_meetings = pd.DataFrame(hero_meetings)
hero_meetings = hero_meetings.to_dict(orient="records")

@app.post("/get_first_hero_meeting", response_model = HeroMeeting)
def get_first_hero_meeting():
    # WILL NOT raise exception because the datetime is assigned
    return HeroMeeting.model_validate(hero_meetings[0])

@app.post("/get_last_hero_meeting", response_model = HeroMeeting)
def get_last_hero_meeting():
    # WILL raise exception because the datetime has been converted from None to Not a Time (NaT) by Pandas, which is not correctly converted to NONE by SQLAlchemy
    return HeroMeeting.model_validate(hero_meetings[-1])

@app.post("/get_hero_meetings", response_model = list[HeroMeeting])
def get_hero_meetings():
    meetings = []
    
    for meeting in hero_meetings:
        
        # WILL raise an exception once it reaches a meeting with an unset time
        meeting = HeroMeeting.model_validate(meeting)
        meetings.append(meeting)

    return meetings

@app.post("/get_hero_meetings", response_model = list[HeroMeeting])
def get_hero_meetings():
    meetings = []
    
    for meeting in hero_meetings:
    
        # FIX: Explicitly convert Not a Time (NaT) back to None.
        if pd.isna(meeting["time"]): meeting["time"] = None
        
        meeting = HeroMeeting.model_validate(meeting)
        meetings.append(meeting)

    return meetings