main.py

import json
from dataclasses import dataclass, field

from fastapi import FastAPI, HTTPException, Response, status


app = FastAPI()


@dataclass
class Channel:
    id: str
    name: str
    tags: list[str] = field(default_factory=list)
    description: str = ""


# channels is a `dict` where keys are `str` and values are `Channel` object
channels: dict[str, Channel] = {}

with open("channels.json", "r", encoding="utf8") as file:
    # encoding="utf8" avoids unicode issues (if there is some encoding data)
    channels_raw: list[dict] = json.load(file)  # load json data to dict

    for channel_raw in channels_raw:
        # it creates a `Channel` object by mapping dict keys to constructor \
        # arguments
        channel = Channel(**channel_raw)
        channels[channel.id] = channel


# server health check
@app.get('/')
def read_root():
    return Response(content="The server is running.")


@app.get("/channels/{channel_id}", response_model=Channel)
def read_item(channel_id: str) -> Channel:
    if channel_id not in channels:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND,
                            detail=f"Channel with id {channel_id} not found.")
    return channels[channel_id]