from __future__ import annotations

import sqlite3
from contextlib import contextmanager
from typing import Any, Dict, Iterable, List, Optional, Tuple, Union

# --------------------------------------------------------------------------- #
# Variables
# --------------------------------------------------------------------------- #
DB_PATH = {'memory': ":memory:", "file": ""}

# --------------------------------------------------------------------------- #
# Helper type aliases
# --------------------------------------------------------------------------- #
Row = Dict[str, Any]
# A column description is: (name, type, optional constraints)
ColumnDef = Tuple[str, str, str]  # name, type, constraints (empty if none)


class SqlDb:
    """
    Thin wrapper around sqlite3 that exposes CRUD helpers for arbitrary tables.
    """

    def __init__(self, db_path: str = ":memory:") -> None:
        """
        Open a connection to the SQLite database.

        Parameters
        ----------
        db_path : str
            Path to the database file. Use ':memory:' for an in‑memory DB.
        """
        self.db_path = db_path
        self.conn = sqlite3.connect(self.db_path)
        # Use sqlite.Row so that we can return rows as dictionaries
        self.conn.row_factory = sqlite3.Row
        self.cursor = self.conn.cursor()

    # ----------------------------------------------------------------------- #
    # Context‑manager support
    # ----------------------------------------------------------------------- #
    def __enter__(self) -> "SqlDb":
        return self

    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
        self.close()

    def close(self) -> None:
        """Close the database connection."""
        self.cursor.close()
        self.conn.close()

    # ----------------------------------------------------------------------- #
    # Table creation
    # ----------------------------------------------------------------------- #
    def create_table(
        self,
        table: str,
        columns: Iterable[ColumnDef],
        *,
        primary_key: Optional[str] = None,
    ) -> None:
        """
        Create a table with the given columns.

        Parameters
        ----------
        table : str
            Table name.
        columns : iterable of ColumnDef
            Each item is a tuple: (column_name, sql_type, constraints)
            Example: ("name", "TEXT", "NOT NULL")
        primary_key : str | None
            Name of the column that should be the PRIMARY KEY.
            If omitted, *no* primary key is created automatically.
        """
        col_defs: List[str] = []
        for name, col_type, constraints in columns:
            if constraints:
                col_defs.append(f"{name} {col_type} {constraints}")
            else:
                col_defs.append(f"{name} {col_type}")

        if primary_key:
            # SQLite allows only one PRIMARY KEY per table, so we make sure
            # that the PK column is part of the definition.
            # We will just add "PRIMARY KEY" to the column definition.
            pk_index = next(
                (i for i, col in enumerate(col_defs) if col.startswith(primary_key)),
                None,
            )
            if pk_index is not None:
                col_defs[pk_index] = f"{col_defs[pk_index]} PRIMARY KEY"
            else:
                # If the PK column wasn't part of the supplied list,
                # we add a separate primary key constraint.
                col_defs.append(f"PRIMARY KEY ({primary_key})")

        sql = f"CREATE TABLE IF NOT EXISTS {table} ({', '.join(col_defs)});"
        self.cursor.execute(sql)
        self.conn.commit()

    # ----------------------------------------------------------------------- #
    # Generic CRUD helpers
    # ----------------------------------------------------------------------- #
    def _dict_to_columns_and_placeholders(
        self, data: Dict[str, Any]
    ) -> Tuple[str, str, Tuple[Any, ...]]:
        """
        Convert a dict into a comma‑separated list of columns,
        a list of '?' placeholders and a tuple of values.
        """
        columns = ", ".join(data.keys())
        placeholders = ", ".join("?" for _ in data)
        values = tuple(data.values())
        return columns, placeholders, values

    def insert(
        self, table: str, data: Dict[str, Any]
    ) -> int:
        """
        Insert a single row.

        Parameters
        ----------
        table : str
            Table name.
        data : dict
            Column/value mapping.

        Returns
        -------
        int
            The lastrowid of the inserted row.
        """
        cols, phs, vals = self._dict_to_columns_and_placeholders(data)
        sql = f"INSERT INTO {table} ({cols}) VALUES ({phs})"
        self.cursor.execute(sql, vals)
        self.conn.commit()
        return self.cursor.lastrowid

    def insert_many(
        self, table: str, rows: Iterable[Dict[str, Any]]
    ) -> List[int]:
        """
        Insert many rows at once.

        Parameters
        ----------
        table : str
            Table name.
        rows : iterable of dict
            Each dict represents a row to insert.

        Returns
        -------
        list of int
            List of lastrowid values for each inserted row.
        """
        # All rows must share the same keys
        rows = list(rows)
        if not rows:
            return []

        cols, phs, _ = self._dict_to_columns_and_placeholders(rows[0])
        sql = f"INSERT INTO {table} ({cols}) VALUES ({phs})"

        # Build a list of tuples for the values
        values = [tuple(row[col] for col in cols.split(", ")) for row in rows]
        self.cursor.executemany(sql, values)
        self.conn.commit()

        # SQLite gives only the last row id; we approximate
        last_id = self.cursor.lastrowid
        # For deterministic behaviour we will simply return the last id for each row.
        return [last_id - len(rows) + i + 1 for i in range(len(rows))]

    def get(
        self,
        table: str,
        pk: str,
        pk_value: Any,
        *,
        columns: Optional[List[str]] = None,
    ) -> Optional[Row]:
        """
        Retrieve a single row by primary key.

        Parameters
        ----------
        table : str
            Table name.
        pk : str
            Name of the primary‑key column.
        pk_value : any
            Value of the primary key.
        columns : list | None
            Columns to retrieve.  If None, all columns are returned.

        Returns
        -------
        dict or None
            Row as a dict, or None if not found.
        """
        cols = ", ".join(columns) if columns else "*"
        sql = f"SELECT {cols} FROM {table} WHERE {pk} = ?"
        self.cursor.execute(sql, (pk_value,))
        row = self.cursor.fetchone()
        return dict(row) if row else None

    def get_all(
        self,
        table: str,
        *,
        columns: Optional[List[str]] = None,
        where: Optional[str] = None,
        where_args: Optional[Iterable[Any]] = None,
        order_by: Optional[str] = None,
        limit: Optional[int] = None,
    ) -> List[Row]:
        """
        Retrieve all rows, optionally filtered/sorted/paginated.

        Parameters
        ----------
        table : str
            Table name.
        columns : list | None
            Columns to fetch.  If None, all columns are returned.
        where : str | None
            Optional WHERE clause (without the word WHERE).
        where_args : iterable | None
            Values for the WHERE clause placeholders.
        order_by : str | None
            ORDER BY clause (without the word ORDER BY).
        limit : int | None
            LIMIT clause.

        Returns
        -------
        list of dict
            List of rows as dictionaries.
        """
        cols = ", ".join(columns) if columns else "*"
        sql = f"SELECT {cols} FROM {table}"
        args: List[Any] = []

        if where:
            sql += f" WHERE {where}"
            if where_args:
                args.extend(where_args)

        if order_by:
            sql += f" ORDER BY {order_by}"

        if limit is not None:
            sql += " LIMIT ?"
            args.append(limit)

        self.cursor.execute(sql, tuple(args))
        rows = self.cursor.fetchall()
        return [dict(row) for row in rows]

    def update(
        self,
        table: str,
        pk: str,
        pk_value: Any,
        data: Dict[str, Any],
    ) -> bool:
        """
        Update a row identified by its primary key.

        Parameters
        ----------
        table : str
            Table name.
        pk : str
            Primary‑key column name.
        pk_value : any
            Value of the primary key.
        data : dict
            Column/value pairs to update.

        Returns
        -------
        bool
            True if a row was updated, False otherwise.
        """
        if not data:
            return False

        set_clause = ", ".join(f"{col} = ?" for col in data)
        vals = tuple(data.values()) + (pk_value,)
        sql = f"UPDATE {table} SET {set_clause} WHERE {pk} = ?"
        self.cursor.execute(sql, vals)
        self.conn.commit()
        return self.cursor.rowcount > 0

    def delete(self, table: str, pk: str, pk_value: Any) -> bool:
        """
        Delete a row by primary key.

        Parameters
        ----------
        table : str
            Table name.
        pk : str
            Primary‑key column name.
        pk_value : any
            Value of the primary key.

        Returns
        -------
        bool
            True if a row was deleted, False otherwise.
        """
        sql = f"DELETE FROM {table} WHERE {pk} = ?"
        self.cursor.execute(sql, (pk_value,))
        self.conn.commit()
        return self.cursor.rowcount > 0
#
# # --------------------------------------------------------------------------- #
# # Example usage
# # --------------------------------------------------------------------------- #
# if __name__ == "__main__":
#     # Using an in‑memory database for demonstration
#     with GenericSQLiteDB(":memory:") as db:
#         # Define two tables of different shapes
#         user_columns = [
#             ("id", "INTEGER", ""),  # will become PRIMARY KEY via parameter
#             ("name", "TEXT", "NOT NULL"),
#             ("email", "TEXT", "UNIQUE NOT NULL"),
#             ("created_at", "TEXT", ""),
#         ]
#
#         product_columns = [
#             ("product_id", "INTEGER", ""),
#             ("name", "TEXT", "NOT NULL"),
#             ("price", "REAL", "NOT NULL"),
#             ("stock", "INTEGER", ""),
#         ]
#
#         # Create tables
#         db.create_table("users", user_columns, primary_key="id")
#         db.create_table("products", product_columns, primary_key="product_id")
#
#         # Insert a user
#         user_id = db.insert(
#             "users",
#             {"id": 1, "name": "Alice", "email": "alice@example.com", "created_at": "2024‑01‑01"},
#         )
#         print(f"Inserted user id={user_id}")
#
#         # Insert multiple products
#         prod_ids = db.insert_many(
#             "products",
#             [
#                 {"product_id": 101, "name": "Gizmo", "price": 19.99, "stock": 50},
#                 {"product_id": 102, "name": "Widget", "price": 9.49, "stock": 200},
#             ],
#         )
#         print(f"Inserted product ids={prod_ids}")
#
#         # Retrieve a single user
#         user = db.get("users", "id", user_id)
#         print("Fetched user:", user)
#
#         # Update the user's email
#         db.update("users", "id", user_id, {"email": "alice@newdomain.com"})
#         print("Updated user:", db.get("users", "id", user_id))
#
#         # List all products that are in stock > 10
#         print(
#             "Products in stock > 10:",
#             db.get_all("products", where="stock > ?", where_args=(10,)),
#         )
#
#         # Delete the user
#         db.delete("users", "id", user_id)
#         print("User after delete:", db.get("users", "id", user_id))