"""CRUD de tablas en Google BigQuery."""

from .client import BQClient
from google.cloud import bigquery


# ---------------------------------------------------------------------------
# Helpers de serializacion
# ---------------------------------------------------------------------------

def _schema_field_to_dict(field: bigquery.SchemaField) -> dict:
    """Convierte un SchemaField a dict serializable."""
    result = {
        "name": field.name,
        "type": field.field_type,
        "mode": field.mode,
        "description": field.description or "",
    }
    if field.fields:
        result["fields"] = [_schema_field_to_dict(f) for f in field.fields]
    return result


def _schema_to_dicts(schema: list) -> list[dict]:
    """Convierte una lista de SchemaField a lista de dicts."""
    return [_schema_field_to_dict(f) for f in schema]


def _dict_to_schema_field(d: dict) -> bigquery.SchemaField:
    """Convierte un dict a SchemaField."""
    nested = [_dict_to_schema_field(f) for f in d.get("fields", [])]
    return bigquery.SchemaField(
        name=d["name"],
        field_type=d.get("type", "STRING"),
        mode=d.get("mode", "NULLABLE"),
        description=d.get("description", ""),
        fields=nested,
    )


def _table_to_dict(table: bigquery.Table) -> dict:
    """Convierte un objeto Table del SDK a dict plano serializable."""
    partitioning = None
    if table.time_partitioning:
        partitioning = {
            "type": table.time_partitioning.type_,
            "field": table.time_partitioning.field or "",
        }
    elif table.range_partitioning:
        partitioning = {
            "type": "RANGE",
            "field": table.range_partitioning.field,
        }

    clustering = None
    if table.clustering_fields:
        clustering = list(table.clustering_fields)

    return {
        "table_id": table.table_id,
        "dataset_id": table.dataset_id,
        "project": table.project,
        "full_id": table.full_table_id or f"{table.project}.{table.dataset_id}.{table.table_id}",
        "schema": _schema_to_dicts(table.schema or []),
        "num_rows": table.num_rows,
        "num_bytes": table.num_bytes,
        "created": table.created.isoformat() if table.created else None,
        "modified": table.modified.isoformat() if table.modified else None,
        "type": table.table_type or "TABLE",
        "partitioning": partitioning,
        "clustering": clustering,
        "description": table.description or "",
        "labels": dict(table.labels or {}),
    }


# ---------------------------------------------------------------------------
# Funciones CRUD
# ---------------------------------------------------------------------------

def bq_create_table(
    client: BQClient,
    dataset_id: str,
    table_id: str,
    schema: list[dict],
    partitioning: dict | None = None,
    clustering: list[str] | None = None,
    description: str = "",
    labels: dict | None = None,
) -> dict:
    """Crea una tabla en BigQuery con schema, particionamiento y clustering opcionales.

    Usa `client._client.create_table()` del SDK oficial.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset donde crear la tabla.
        table_id: ID (nombre) de la tabla a crear.
        schema: Lista de dicts con definicion de columnas. Cada dict:
            {"name": "col", "type": "STRING", "mode": "NULLABLE", "description": "..."}
            Tipos validos: STRING, INTEGER, FLOAT, BOOLEAN, BYTES, DATE, DATETIME,
            TIME, TIMESTAMP, RECORD, NUMERIC, BIGNUMERIC, JSON, GEOGRAPHY.
            Modos: NULLABLE, REQUIRED, REPEATED.
        partitioning: Dict de configuracion de particion o None. Ejemplo:
            {"type": "DAY", "field": "created_at"}
            Tipos: DAY, MONTH, YEAR, HOUR. Field vacio usa pseudo-columna _PARTITIONTIME.
        clustering: Lista de columnas para clustering (max 4) o None.
            Ejemplo: ["country", "status"]
        description: Descripcion de la tabla.
        labels: Etiquetas clave-valor para la tabla. Ejemplo: {"env": "prod"}.

    Returns:
        Dict con metadata de la tabla creada: table_id, dataset_id, project,
        full_id, schema, num_rows, num_bytes, created, modified, type,
        partitioning, clustering, description, labels.

    Raises:
        google.api_core.exceptions.Conflict: Si la tabla ya existe.
        google.api_core.exceptions.NotFound: Si el dataset no existe.
        google.api_core.exceptions.BadRequest: Si el schema es invalido.

    Example:
        >>> table = bq_create_table(client, "mi_dataset", "ventas", [
        ...     {"name": "id", "type": "INTEGER", "mode": "REQUIRED"},
        ...     {"name": "fecha", "type": "DATE", "mode": "NULLABLE"},
        ...     {"name": "monto", "type": "FLOAT", "mode": "NULLABLE"},
        ... ], partitioning={"type": "MONTH", "field": "fecha"},
        ...    clustering=["id"])
        >>> print(table["full_id"])
    """
    table_ref = f"{client.project_id}.{dataset_id}.{table_id}"
    bq_schema = [_dict_to_schema_field(f) for f in schema]

    table = bigquery.Table(table_ref, schema=bq_schema)

    if partitioning:
        table.time_partitioning = bigquery.TimePartitioning(
            type_=partitioning.get("type", "DAY"),
            field=partitioning.get("field") or None,
        )

    if clustering:
        table.clustering_fields = clustering

    if description:
        table.description = description

    if labels:
        table.labels = labels

    created = client._client.create_table(table)
    return _table_to_dict(created)


def bq_get_table(client: BQClient, dataset_id: str, table_id: str) -> dict:
    """Obtiene los metadatos completos de una tabla BigQuery.

    Usa `client._client.get_table()` del SDK oficial.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset que contiene la tabla.
        table_id: ID (nombre) de la tabla.

    Returns:
        Dict con: table_id, dataset_id, project, full_id, schema (lista de dicts),
        num_rows, num_bytes, created (ISO 8601), modified (ISO 8601), type
        (TABLE, VIEW, MATERIALIZED_VIEW, EXTERNAL), partitioning (dict o None),
        clustering (lista de strings o None), description, labels.

    Raises:
        google.api_core.exceptions.NotFound: Si la tabla no existe.

    Example:
        >>> tabla = bq_get_table(client, "mi_dataset", "ventas")
        >>> print(tabla["num_rows"], tabla["schema"])
    """
    table_ref = f"{client.project_id}.{dataset_id}.{table_id}"
    table = client._client.get_table(table_ref)
    return _table_to_dict(table)


def bq_list_tables(client: BQClient, dataset_id: str) -> list[dict]:
    """Lista todas las tablas de un dataset BigQuery.

    Usa `client._client.list_tables()` del SDK oficial.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset a listar.

    Returns:
        Lista de dicts resumidos, uno por tabla. Cada dict contiene:
        table_id, full_id, type (TABLE, VIEW, MATERIALIZED_VIEW, EXTERNAL).

    Raises:
        google.api_core.exceptions.NotFound: Si el dataset no existe.

    Example:
        >>> tablas = bq_list_tables(client, "mi_dataset")
        >>> for t in tablas:
        ...     print(t["table_id"], t["type"])
    """
    dataset_ref = f"{client.project_id}.{dataset_id}"
    tables = client._client.list_tables(dataset_ref)
    return [
        {
            "table_id": t.table_id,
            "full_id": f"{t.project}.{t.dataset_id}.{t.table_id}",
            "type": t.table_type or "TABLE",
        }
        for t in tables
    ]


def bq_update_table(
    client: BQClient,
    dataset_id: str,
    table_id: str,
    schema: list[dict] | None = None,
    description: str | None = None,
    labels: dict | None = None,
) -> dict:
    """Actualiza metadatos de una tabla BigQuery.

    Usa `client._client.update_table()` del SDK oficial. Solo modifica los
    campos no-None. Para schema, BigQuery SOLO permite agregar columnas nuevas
    al final — no se pueden eliminar ni modificar columnas existentes.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset que contiene la tabla.
        table_id: ID (nombre) de la tabla a actualizar.
        schema: Lista de dicts con el schema completo nuevo (incluye columnas
            existentes + nuevas). Solo se permiten adiciones. None = sin cambios.
        description: Nueva descripcion de la tabla. None = sin cambios.
        labels: Nuevas etiquetas clave-valor. None = sin cambios.

    Returns:
        Dict con la metadata actualizada de la tabla (misma estructura que bq_get_table).

    Raises:
        google.api_core.exceptions.NotFound: Si la tabla no existe.
        google.api_core.exceptions.BadRequest: Si se intenta eliminar columnas.

    Example:
        >>> tabla = bq_update_table(client, "mi_dataset", "ventas",
        ...     description="Tabla de ventas actualizada",
        ...     labels={"env": "prod", "team": "data"})
        >>> tabla = bq_update_table(client, "mi_dataset", "ventas",
        ...     schema=[
        ...         {"name": "id", "type": "INTEGER", "mode": "REQUIRED"},
        ...         {"name": "nueva_col", "type": "STRING", "mode": "NULLABLE"},
        ...     ])
    """
    table_ref = f"{client.project_id}.{dataset_id}.{table_id}"
    table = client._client.get_table(table_ref)

    fields_to_update = []

    if schema is not None:
        table.schema = [_dict_to_schema_field(f) for f in schema]
        fields_to_update.append("schema")

    if description is not None:
        table.description = description
        fields_to_update.append("description")

    if labels is not None:
        table.labels = labels
        fields_to_update.append("labels")

    if not fields_to_update:
        return _table_to_dict(table)

    updated = client._client.update_table(table, fields_to_update)
    return _table_to_dict(updated)


def bq_delete_table(client: BQClient, dataset_id: str, table_id: str) -> None:
    """Elimina permanentemente una tabla de BigQuery.

    Usa `client._client.delete_table()` del SDK oficial. IRREVERSIBLE — no hay
    papelera de reciclaje. Considerar exportar datos antes de eliminar.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset que contiene la tabla.
        table_id: ID (nombre) de la tabla a eliminar.

    Raises:
        google.api_core.exceptions.NotFound: Si la tabla no existe.

    Example:
        >>> bq_delete_table(client, "mi_dataset", "tabla_temporal")
    """
    table_ref = f"{client.project_id}.{dataset_id}.{table_id}"
    client._client.delete_table(table_ref)


def bq_preview_rows(
    client: BQClient,
    dataset_id: str,
    table_id: str,
    max_results: int = 10,
) -> dict:
    """Obtiene una muestra de filas de una tabla BigQuery sin ejecutar query.

    Usa `client._client.list_rows()` del SDK oficial — no genera costes de
    procesamiento de bytes (no es una query SQL). Ideal para vista previa rapida.

    Args:
        client: Cliente autenticado BQClient.
        dataset_id: ID del dataset que contiene la tabla.
        table_id: ID (nombre) de la tabla a previsualizar.
        max_results: Numero maximo de filas a retornar. Default: 10.

    Returns:
        Dict con:
        - columns: lista de strings con nombres de columnas
        - rows: lista de listas con valores de cada fila
        - total_rows: numero total de filas en la tabla (no en el preview)

    Raises:
        google.api_core.exceptions.NotFound: Si la tabla no existe.

    Example:
        >>> preview = bq_preview_rows(client, "mi_dataset", "ventas", max_results=5)
        >>> print(preview["columns"])
        >>> for row in preview["rows"]:
        ...     print(row)
        >>> print(f"Total en tabla: {preview['total_rows']}")
    """
    table_ref = f"{client.project_id}.{dataset_id}.{table_id}"
    table = client._client.get_table(table_ref)
    rows_iter = client._client.list_rows(table, max_results=max_results)

    columns = [f.name for f in rows_iter.schema]
    rows = [list(row.values()) for row in rows_iter]

    return {
        "columns": columns,
        "rows": rows,
        "total_rows": table.num_rows,
    }