app.py

from fastapi import FastAPI, Request
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates
import chess
from datasets import load_dataset
import pickle
import time
from pyroaring import BitMap

def board_to_tokens(board):
    return [(board.piece_at(sq).symbol(), chess.square_name(sq)) for sq in chess.SQUARES if board.piece_at(sq)]
    
def get_puzzle_positions(fen, moves_uci):
    positions = []
    
    board = chess.Board(fen)
    
    board.push_uci(moves_uci.split()[0])
    positions.append(board.copy())
    
    for move_uci in moves_uci.split()[1:]:
        board.push_uci(move_uci)
        positions.append(board.copy())
    
    return positions

def load_index(path='chess_index.pkl'):
    with open(path, 'rb') as f: data = pickle.load(f)
    return data['index'], data['metadata']

def query_positions(index, metadata, query_tokens):
    result = index[query_tokens[0]].copy() if query_tokens[0] in index else BitMap()
    for token in query_tokens[1:]:
        if token in index: result &= index[token]
        else: return BitMap()
            
    return [(pos_id, metadata[pos_id]) for pos_id in result]

dset = load_dataset("Lichess/chess-puzzles", split="train")
index, metadata = load_index()
app = FastAPI()
app.mount("/static", StaticFiles(directory="static"), name="static")
templates = Jinja2Templates(directory="templates")

@app.get("/")
def read_root(request: Request):
    return templates.TemplateResponse("index.html", {"request": request})



@app.post("/search")
async def search(data: dict):
    start = time.time()
    board = chess.Board(data['fen'])
    query_tokens = board_to_tokens(board)
    matches = query_positions(index, metadata, query_tokens)
    
    seen_puzzles = {}
    for pos_id, (puzzle_row, move_idx) in matches:
        if puzzle_row not in seen_puzzles:
            seen_puzzles[puzzle_row] = (pos_id, move_idx)
    
    results = []
    for puzzle_row, (pos_id, move_idx) in seen_puzzles.items():
        row = dset[puzzle_row]
        positions = get_puzzle_positions(row['FEN'], row['Moves'])
        matched_board = positions[move_idx]
        
        results.append({
            "PuzzleId": row['PuzzleId'],
            "FEN": matched_board.fen(),
            "Moves": row['Moves'],
            "Rating": row['Rating'],
            "Popularity": row['Popularity'],
            "Themes": row['Themes'],
            "MatchedMove": move_idx
        })
    
    elapsed_ms = (time.time() - start) * 1000
    return {"count": len(results), "results": results, "time_ms": elapsed_ms}