photovoter_backend/main.py

from fastapi import FastAPI
from fastapi.responses import JSONResponse

from datetime import datetime
from uuid import uuid4
import sqlite3


# use database residing here
DB_LOCATION = (
    "../testbox/photovoter.dblite"  # Q: any allowances for this being not OUR database?
)

app = FastAPI()
con = sqlite3.connect(DB_LOCATION)
con.row_factory = sqlite3.Row
cur = con.cursor()  # NB! single is enough for now, we might require multiple later


@app.get("/new_session", responses={503: {"description": "Unable to initiate session"}})
async def new_session():
    """Start a new session"""
    # add session to the database
    time = datetime.utcnow().replace(microsecond=0).isoformat()
    tries = 3  # something is very wrong with our random, if we miss 3 times
    for i in range(tries):
        try:
            # generate a cookie
            cookie = uuid4().hex
            cur.execute(
                """INSERT INTO sessions(cookie, time)
                            VALUES(:cookie, :time)
                        """,
                {"cookie": cookie, "time": time},
            )
            con.commit()
        except sqlite3.IntegrityError as e:
            if i < tries - 1 and str(e) == "UNIQUE constraint failed: sessions.cookie":
                continue
            elif str(e) == "UNIQUE constraint failed: sessions.cookie":
                return JSONResponse(status_code=503)
            else:
                raise
        break

    # return new session cookie
    return {"cookie": cookie}


@app.get(
    "/next_picture/{cookie}",
    responses={
        204: {"description": "All available images have been appraised"},
        409: {"description": "Uninitiated session"},
    },
)
async def next_picture(cookie: str):
    """Request new picture to rate."""
    # check if the cookie is valid
    cur.execute(
        """SELECT sessionid 
            FROM sessions 
            WHERE cookie = :cookie
            LIMIT 1""",
        {"cookie": cookie},
    )
    sessionid = cur.fetchone()
    if sessionid is None:
        return JSONResponse(status_code=409)

    # take not rated picture from the database
    # do not insert anything in the database yet
    # return this picture

    # SELECT all images EXCEPT images with marks from the current session ->
    # -> SELECT paths for these images
    # FIXME[0]: can this be done better?
    cur.execute(
        """SELECT imgid, resizedpath
                FROM images
                WHERE imgid IN  (SELECT imgid
                                    FROM images
                                    EXCEPT
                                    SELECT imgid
                                    FROM marks
                                    WHERE sessionid = :sessionid)
                LIMIT 1
    """,
        {"sessionid": sessionid["sessionid"]},
    )
    r = cur.fetchone()
    if r is not None:
        return {"picture_id": r["imgid"], "picture_uri": r["resizedpath"]}
    else:
        # All available pics have been voted for by this sessionid
        return JSONResponse(status_code=204)


@app.get(
    "/rate_picture/{cookie}/{picture_id}/{mark}",
    responses={
        406: {"description": "Already appraised"},
        409: {"description": "Uninitiated session"},
    },
)
async def rate_picture(cookie: str, picture_id: int, mark: int):
    """Submit a rating for the picture"""
    # check if the cookie is valid
    cur.execute(
        """SELECT sessionid 
            FROM sessions 
            WHERE cookie = :cookie
            LIMIT 1""",
        {"cookie": cookie},
    )
    sessionid = cur.fetchone()
    if sessionid is None:
        return JSONResponse(status_code=409)

    # add new mark to the session table
    try:
        cur.execute(
            """INSERT INTO marks(imgid, sessionid, mark)
                        VALUES(:imgid,:sessionid,:mark)
                    """,
            {"imgid": picture_id, "sessionid": sessionid["sessionid"], "mark": mark},
        )
        con.commit()
    except sqlite3.IntegrityError as e:
        if str(e) == "UNIQUE constraint failed: marks.imgid, marks.sessionid":
            return JSONResponse(status_code=406)

    return {"status": "success"}