"""Durable, account-scoped ordered Today plans."""

import json
import sqlite3
import time
from pathlib import Path


class TodayPlanFull(ValueError):
    """Raised when an add would exceed the bounded Today plan."""


class TodayStore:
    def __init__(
        self,
        path: str | Path,
        *,
        limit: int = 5,
        timeout: float = 1.0,
        operation_limit: int = 4096,
        operation_retention_seconds: float = 30 * 24 * 60 * 60,
        clock=time.time,
    ):
        self.path = Path(path)
        self.limit = limit
        self.timeout = timeout
        self.operation_limit = operation_limit
        self.operation_retention_seconds = operation_retention_seconds
        self.clock = clock

    def _connect(self) -> sqlite3.Connection:
        self.path.parent.mkdir(parents=True, exist_ok=True)
        connection = sqlite3.connect(self.path, timeout=self.timeout)
        connection.execute("PRAGMA journal_mode=WAL")
        connection.execute(
            """
            CREATE TABLE IF NOT EXISTS today_plans (
                login TEXT PRIMARY KEY,
                revision INTEGER NOT NULL,
                ids TEXT NOT NULL
            )
            """
        )
        connection.execute(
            """
            CREATE TABLE IF NOT EXISTS today_operations (
                login TEXT NOT NULL,
                operation_id TEXT NOT NULL,
                created_at REAL NOT NULL,
                PRIMARY KEY (login, operation_id)
            )
            """
        )
        columns = {row[1] for row in connection.execute("PRAGMA table_info(today_operations)")}
        if "created_at" not in columns:
            connection.execute("ALTER TABLE today_operations ADD COLUMN created_at REAL")
        connection.execute(
            "UPDATE today_operations SET created_at = ? WHERE created_at IS NULL",
            (self.clock(),),
        )
        connection.commit()
        return connection

    def _record_operation(self, connection: sqlite3.Connection, login: str, operation_id: str) -> None:
        now = self.clock()
        connection.execute(
            "INSERT INTO today_operations(login, operation_id, created_at) VALUES (?, ?, ?)",
            (login, operation_id, now),
        )
        connection.execute(
            "DELETE FROM today_operations WHERE login = ? AND created_at < ?",
            (login, now - self.operation_retention_seconds),
        )
        connection.execute(
            "DELETE FROM today_operations WHERE login = ? AND rowid NOT IN "
            "(SELECT rowid FROM today_operations WHERE login = ? "
            "ORDER BY created_at DESC, rowid DESC LIMIT ?)",
            (login, login, self.operation_limit),
        )

    @staticmethod
    def _normalize_login(login: str) -> str:
        normalized = login.strip().lower()
        if not normalized:
            raise ValueError("login is required")
        return normalized

    @staticmethod
    def _snapshot(row) -> dict:
        if row is None:
            return {"revision": 0, "ids": []}
        return {"revision": int(row[0]), "ids": json.loads(row[1])}

    def get(self, login: str) -> dict:
        with self._connect() as connection:
            row = connection.execute(
                "SELECT revision, ids FROM today_plans WHERE login = ?",
                (self._normalize_login(login),),
            ).fetchone()
        return self._snapshot(row)

    def apply(
        self,
        login: str,
        operation_id: str,
        action: str,
        item_id: str,
        *,
        direction: str | None = None,
    ) -> dict:
        login = self._normalize_login(login)
        if not operation_id or not item_id:
            raise ValueError("operation_id and item_id are required")
        if action not in {"add", "remove", "move"}:
            raise ValueError("unsupported Today action")
        if action == "move" and direction not in {"up", "down"}:
            raise ValueError("move direction must be up or down")

        with self._connect() as connection:
            connection.execute("BEGIN IMMEDIATE")
            row = connection.execute(
                "SELECT revision, ids FROM today_plans WHERE login = ?", (login,)
            ).fetchone()
            snapshot = self._snapshot(row)
            duplicate = connection.execute(
                "SELECT 1 FROM today_operations WHERE login = ? AND operation_id = ?",
                (login, operation_id),
            ).fetchone()
            if duplicate:
                return snapshot

            ids = list(snapshot["ids"])
            changed = False
            if action == "add":
                if item_id not in ids:
                    if len(ids) >= self.limit:
                        raise TodayPlanFull("Today is limited to five items")
                    ids.append(item_id)
                    changed = True
            elif action == "remove":
                if item_id in ids:
                    ids.remove(item_id)
                    changed = True
            else:
                try:
                    index = ids.index(item_id)
                except ValueError:
                    index = -1
                target = index - 1 if direction == "up" else index + 1
                if index >= 0 and 0 <= target < len(ids):
                    ids[index], ids[target] = ids[target], ids[index]
                    changed = True

            revision = snapshot["revision"] + (1 if changed else 0)
            if row is None:
                connection.execute(
                    "INSERT INTO today_plans(login, revision, ids) VALUES (?, ?, ?)",
                    (login, revision, json.dumps(ids, separators=(",", ":"))),
                )
            elif changed:
                connection.execute(
                    "UPDATE today_plans SET revision = ?, ids = ? WHERE login = ?",
                    (revision, json.dumps(ids, separators=(",", ":")), login),
                )
            self._record_operation(connection, login, operation_id)
            return {"revision": revision, "ids": ids}

    def apply_batch(self, login: str, operations: list[dict]) -> dict:
        """Apply an ordered batch with one lock and receipt per operation."""
        login = self._normalize_login(login)
        with self._connect() as connection:
            connection.execute("BEGIN IMMEDIATE")
            row = connection.execute(
                "SELECT revision, ids FROM today_plans WHERE login = ?", (login,)
            ).fetchone()
            snapshot = self._snapshot(row)
            ids = list(snapshot["ids"])
            revision = snapshot["revision"]
            accepted: list[str] = []
            duplicates: list[str] = []
            rejected: list[dict[str, str]] = []

            for operation in operations:
                operation_id = operation.get("operation_id", "")
                action = operation.get("action", "")
                item_id = operation.get("item_id", "")
                direction = operation.get("direction")
                if not operation_id or not item_id:
                    raise ValueError("operation_id and item_id are required")
                if action not in {"add", "remove", "move"}:
                    raise ValueError("unsupported Today action")
                if action == "move" and direction not in {"up", "down"}:
                    raise ValueError("move direction must be up or down")
                duplicate = connection.execute(
                    "SELECT 1 FROM today_operations WHERE login = ? AND operation_id = ?",
                    (login, operation_id),
                ).fetchone()
                if duplicate:
                    duplicates.append(operation_id)
                    continue

                base_revision = operation.get("base_revision")
                if base_revision is None:
                    base_revision = snapshot["revision"]
                if not isinstance(base_revision, int) or isinstance(base_revision, bool) or base_revision < 0:
                    raise ValueError("base_revision must be a non-negative integer")
                if base_revision < snapshot["revision"]:
                    self._record_operation(connection, login, operation_id)
                    rejected.append({"operation_id": operation_id, "reason": "stale_intent"})
                    continue

                changed = False
                if action == "add":
                    if item_id not in ids:
                        if len(ids) >= self.limit:
                            rejected.append({"operation_id": operation_id, "reason": "today_full"})
                            continue
                        ids.append(item_id)
                        changed = True
                elif action == "remove":
                    if item_id in ids:
                        ids.remove(item_id)
                        changed = True
                else:
                    try:
                        index = ids.index(item_id)
                    except ValueError:
                        index = -1
                    target = index - 1 if direction == "up" else index + 1
                    if index >= 0 and 0 <= target < len(ids):
                        ids[index], ids[target] = ids[target], ids[index]
                        changed = True
                revision += 1 if changed else 0
                self._record_operation(connection, login, operation_id)
                accepted.append(operation_id)

            serialized = json.dumps(ids, separators=(",", ":"))
            if row is None:
                connection.execute(
                    "INSERT INTO today_plans(login, revision, ids) VALUES (?, ?, ?)",
                    (login, revision, serialized),
                )
            elif accepted:
                connection.execute(
                    "UPDATE today_plans SET revision = ?, ids = ? WHERE login = ?",
                    (revision, serialized, login),
                )
            return {
                "revision": revision,
                "ids": ids,
                "accepted_operation_ids": accepted,
                "duplicate_operation_ids": duplicates,
                "rejected_operations": rejected,
            }