"""REST API handlers for game operations."""

import collections
import json
import re
import time
from datetime import datetime, timezone

import tornado.web

from game.factory import BoardFactory, DIRECTIONS
from models.category import Category
from models.game import Game, Word

# Per-IP rate limit: tracks {ip: deque of timestamps}
_rate_buckets = collections.defaultdict(collections.deque)

# Limits: (max_requests, window_seconds)
RATE_LIMITS = {
    "default": (60, 60),
    "new_game": (10, 60),
}


def _check_rate(ip, bucket="default"):
    max_requests, window = RATE_LIMITS[bucket]
    now = time.monotonic()
    timestamps = _rate_buckets[f"{bucket}:{ip}"]
    while timestamps and timestamps[0] <= now - window:
        timestamps.popleft()
    if len(timestamps) >= max_requests:
        return False
    timestamps.append(now)
    return True


_PLAYER_NAME_RE = re.compile(r"^[a-zA-Z0-9 ]+$")
MAX_PLAYER_NAME_LEN = 20


def _sanitize_player_name(raw):
    """Validate and sanitize a player name. Returns name or None (invalid)."""
    if not isinstance(raw, str):
        return "Anonymous"
    name = raw.strip()
    if not name:
        return "Anonymous"
    if len(name) > MAX_PLAYER_NAME_LEN:
        name = name[:MAX_PLAYER_NAME_LEN]
    if not _PLAYER_NAME_RE.match(name):
        return None
    return name


class BaseAPIHandler(tornado.web.RequestHandler):
    """Base handler for JSON API endpoints."""

    def set_default_headers(self):
        self.set_header("Content-Type", "application/json")

    def get_session(self):
        Session = self.application.settings["session_factory"]
        return Session()

    def check_rate_limit(self, bucket="default"):
        """Return True if request is allowed, else write 429 and return False."""
        if not _check_rate(self.request.remote_ip, bucket):
            self.set_status(429)
            self.write(json.dumps({"error": "Too many requests"}))
            return False
        return True

    def write_error(self, status_code, **kwargs):
        self.write(json.dumps({"error": self._reason}))


class CategoriesHandler(BaseAPIHandler):
    """``GET /api/categories`` -- list all word categories."""

    def get(self):
        session = self.get_session()
        try:
            categories = session.query(Category).all()
            self.write(json.dumps([{"id": c.id, "name": c.name} for c in categories]))
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()


class NewGameHandler(BaseAPIHandler):
    """``POST /api/game/new`` -- create a new game.

    Expects JSON body with ``category_id`` and optional ``board_size`` (8-20)
    and ``word_count`` (3-30).
    """

    def post(self):
        if not self.check_rate_limit("new_game"):
            return
        session = self.get_session()
        try:
            try:
                data = json.loads(self.request.body)
            except (json.JSONDecodeError, TypeError):
                self.set_status(400)
                self.write(json.dumps({"error": "Invalid JSON"}))
                return

            if "category_id" not in data:
                self.set_status(400)
                self.write(json.dumps({"error": "category_id is required"}))
                return

            category_id = data["category_id"]

            try:
                board_size = int(data.get("board_size", 10))
            except (TypeError, ValueError):
                self.set_status(400)
                self.write(json.dumps({"error": "board_size must be a number"}))
                return
            board_size = max(8, min(20, board_size))

            try:
                word_count = int(data.get("word_count", 8))
            except (TypeError, ValueError):
                self.set_status(400)
                self.write(json.dumps({"error": "word_count must be a number"}))
                return
            word_count = max(3, min(30, word_count))

            player_name = _sanitize_player_name(data.get("player_name", ""))
            if player_name is None:
                self.set_status(400)
                self.write(
                    json.dumps(
                        {
                            "error": "Player name may only contain"
                            " letters, numbers, and spaces"
                        }
                    )
                )
                return

            category = session.query(Category).filter_by(id=category_id).first()
            if not category:
                self.set_status(404)
                self.write(json.dumps({"error": "Category not found"}))
                return

            factory = BoardFactory(session)
            game, words = factory.create(
                category_id=category_id,
                board_size=board_size,
                word_count=word_count,
            )

            if not words:
                self.set_status(500)
                self.write(json.dumps({"error": "Failed to generate board with words"}))
                return

            game.player_name = player_name
            session.add(game)
            for w in words:
                session.add(w)
            session.commit()

            self.write(json.dumps(self._game_to_dict(game)))
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()

    def _game_to_dict(self, game):
        return {
            "id": game.id,
            "board_size": game.board_size,
            "player_name": game.player_name,
            "category": game.category.name,
            "grid": game.grid,
            "words": [{"text": w.text, "found": w.found} for w in game.words],
            "started_at": game.started_at.isoformat() + "Z",
            "status": game.status,
            "completed_at": None,
        }


class GameStateHandler(BaseAPIHandler):
    """``GET /api/game/<id>`` -- retrieve current game state."""

    def get(self, game_id):
        session = self.get_session()
        try:
            game = session.query(Game).filter_by(id=game_id).first()
            if not game:
                self.set_status(404)
                self.write(json.dumps({"error": "Game not found"}))
                return
            self.write(
                json.dumps(
                    {
                        "id": game.id,
                        "board_size": game.board_size,
                        "player_name": game.player_name,
                        "category": game.category.name,
                        "grid": game.grid,
                        "words": [
                            {"text": w.text, "found": w.found} for w in game.words
                        ],
                        "started_at": game.started_at.isoformat() + "Z",
                        "status": game.status,
                        "completed_at": (
                            game.completed_at.isoformat() + "Z"
                            if game.completed_at
                            else None
                        ),
                    }
                )
            )
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()


class GuessHandler(BaseAPIHandler):
    """``POST /api/game/<id>/guess`` -- submit a word guess.

    Accepts either ``{"word": "..."}`` for text input or
    ``{"cells": [{"row": N, "col": N}, ...]}`` for click selection.
    """

    def post(self, game_id):
        if not self.check_rate_limit():
            return
        session = self.get_session()
        try:
            game = session.query(Game).filter_by(id=game_id).first()
            if not game:
                self.set_status(404)
                self.write(json.dumps({"error": "Game not found"}))
                return

            try:
                data = json.loads(self.request.body)
            except (json.JSONDecodeError, TypeError):
                self.set_status(400)
                self.write(json.dumps({"error": "Invalid JSON"}))
                return

            if "word" in data:
                result = self._handle_text_guess(session, game, data["word"])
            elif "cells" in data:
                result = self._handle_click_guess(session, game, data["cells"])
            else:
                self.set_status(400)
                self.write(json.dumps({"error": "Provide 'word' or 'cells'"}))
                return

            self.write(json.dumps(result))
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()

    def _handle_text_guess(self, session, game, guess_text):
        if not isinstance(guess_text, str):
            return self._miss_response(game, session)
        guess_text = guess_text.upper().strip()
        word = (
            session.query(Word)
            .filter_by(game_id=game.id, text=guess_text, found=False)
            .first()
        )
        if not word:
            return self._miss_response(game, session)

        return self._mark_found(session, game, word)

    def _handle_click_guess(self, session, game, cells):
        grid = game.grid
        try:
            letters = "".join(grid[c["row"]][c["col"]] for c in cells)
        except (IndexError, KeyError, TypeError):
            return self._miss_response(game, session)

        word = (
            session.query(Word)
            .filter_by(game_id=game.id, text=letters, found=False)
            .first()
        )
        if not word:
            return self._miss_response(game, session)

        dr, dc = DIRECTIONS[word.direction]
        expected_cells = [
            {"row": word.start_row + i * dr, "col": word.start_col + i * dc}
            for i in range(len(word.text))
        ]
        if cells != expected_cells:
            return self._miss_response(game, session)

        return self._mark_found(session, game, word)

    def _mark_found(self, session, game, word):
        word.found = True
        word.found_at = datetime.now(timezone.utc)

        unfound = session.query(Word).filter_by(game_id=game.id, found=False).count()
        if unfound == 0:
            game.status = "completed"
            game.completed_at = datetime.now(timezone.utc)

        session.commit()

        dr, dc = DIRECTIONS[word.direction]
        cells = [
            {"row": word.start_row + i * dr, "col": word.start_col + i * dc}
            for i in range(len(word.text))
        ]

        return {
            "correct": True,
            "word": word.text,
            "cells": cells,
            "words": [{"text": w.text, "found": w.found} for w in game.words],
            "status": game.status,
            "player_name": game.player_name,
            "completed_at": (
                game.completed_at.isoformat() + "Z" if game.completed_at else None
            ),
        }

    def _miss_response(self, game, session):
        return {
            "correct": False,
            "word": None,
            "cells": [],
            "words": [{"text": w.text, "found": w.found} for w in game.words],
            "status": game.status,
            "player_name": game.player_name,
            "completed_at": None,
        }


class ScoreboardAPIHandler(BaseAPIHandler):
    """``GET /api/scoreboard`` -- leaderboards and popular categories."""

    def get(self):
        session = self.get_session()
        try:
            categories = session.query(Category).all()

            leaderboards = {}
            for cat in categories:
                completed = (
                    session.query(Game)
                    .filter(
                        Game.category_id == cat.id,
                        Game.status == "completed",
                        Game.completed_at.isnot(None),
                    )
                    .all()
                )
                completed.sort(
                    key=lambda g: (g.completed_at - g.started_at).total_seconds()
                )
                top = completed[:10]
                if top:
                    leaderboards[cat.name] = [
                        {
                            "player_name": g.player_name,
                            "time_seconds": (
                                g.completed_at - g.started_at
                            ).total_seconds(),
                            "board_size": g.board_size,
                            "word_count": len(g.words),
                            "completed_at": g.completed_at.isoformat() + "Z",
                        }
                        for g in top
                    ]

            popular = []
            for cat in categories:
                count = (
                    session.query(Game)
                    .filter(
                        Game.category_id == cat.id,
                        Game.status == "completed",
                    )
                    .count()
                )
                popular.append(
                    {
                        "id": cat.id,
                        "name": cat.name,
                        "completed_games": count,
                    }
                )
            popular.sort(key=lambda x: x["completed_games"], reverse=True)

            self.write(
                json.dumps(
                    {
                        "leaderboards": leaderboards,
                        "popular_categories": popular,
                    }
                )
            )
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()