"""Shared helpers for DataForge CLI commands."""

from __future__ import annotations

from collections.abc import Iterable
from pathlib import Path
from typing import cast

import pandas as pd
import typer
import yaml

from dataforge.verifier.schema import (
    AggregateDependency,
    AggregateLiteral,
    DomainBound,
    FunctionalDependency,
    Schema,
)


def schema_from_mapping(raw_mapping: object) -> Schema:
    """Build a Schema from a raw YAML mapping-like payload.

    Args:
        raw_mapping: Untrusted YAML-decoded value.

    Returns:
        Parsed Schema object.

    Raises:
        typer.BadParameter: If the payload is not a mapping.
    """
    if raw_mapping is None:
        mapping: dict[str, object] = {}
    elif isinstance(raw_mapping, dict):
        mapping = raw_mapping
    else:
        raise typer.BadParameter("Schema payload must be a YAML mapping.")

    columns: dict[str, str] = {}
    raw_columns = mapping.get("columns", {})
    if isinstance(raw_columns, dict):
        columns = {str(key): str(value) for key, value in raw_columns.items()}

    fds: list[FunctionalDependency] = []
    raw_fds = mapping.get("functional_dependencies", [])
    if isinstance(raw_fds, list):
        for raw_fd in raw_fds:
            if not isinstance(raw_fd, dict):
                continue
            raw_determinant = raw_fd.get("determinant", [])
            determinant_values = (
                tuple(str(value) for value in raw_determinant)
                if isinstance(raw_determinant, Iterable)
                and not isinstance(raw_determinant, (str, bytes))
                else ()
            )
            fds.append(
                FunctionalDependency(
                    determinant=determinant_values,
                    dependent=str(raw_fd.get("dependent", "")),
                )
            )

    raw_pii_columns = mapping.get("pii_columns", [])
    pii_columns = (
        frozenset(str(value) for value in raw_pii_columns)
        if isinstance(raw_pii_columns, Iterable) and not isinstance(raw_pii_columns, (str, bytes))
        else frozenset()
    )

    bounds: list[DomainBound] = []
    raw_bounds = mapping.get("domain_bounds", {})
    if isinstance(raw_bounds, dict):
        for column, bound_payload in raw_bounds.items():
            if not isinstance(bound_payload, dict):
                continue
            bounds.append(
                DomainBound(
                    column=str(column),
                    min_value=(
                        float(bound_payload["min"])
                        if bound_payload.get("min") is not None
                        else None
                    ),
                    max_value=(
                        float(bound_payload["max"])
                        if bound_payload.get("max") is not None
                        else None
                    ),
                    inclusive_min=bool(bound_payload.get("inclusive_min", True)),
                    inclusive_max=bool(bound_payload.get("inclusive_max", True)),
                )
            )

    aggregate_dependencies: list[AggregateDependency] = []
    raw_aggregates = mapping.get("aggregate_dependencies", [])
    if isinstance(raw_aggregates, list):
        for raw_dependency in raw_aggregates:
            if not isinstance(raw_dependency, dict):
                continue
            raw_aggregate = str(raw_dependency.get("aggregate", "")).lower()
            if raw_aggregate not in {"sum", "avg"}:
                continue
            raw_group_by = raw_dependency.get("group_by", [])
            group_by = (
                tuple(str(value) for value in raw_group_by)
                if isinstance(raw_group_by, Iterable) and not isinstance(raw_group_by, (str, bytes))
                else ()
            )
            aggregate_dependencies.append(
                AggregateDependency(
                    source_column=str(raw_dependency.get("source_column", "")),
                    aggregate=cast(AggregateLiteral, raw_aggregate),
                    target_column=str(raw_dependency.get("target_column", "")),
                    group_by=group_by,
                )
            )

    return Schema(
        columns=columns,
        functional_dependencies=tuple(fds),
        pii_columns=pii_columns,
        domain_bounds=tuple(bounds),
        aggregate_dependencies=tuple(aggregate_dependencies),
    )


def load_schema(schema_path: Path) -> Schema:
    """Load a Schema from a YAML file.

    Args:
        schema_path: Path to the YAML schema file.

    Returns:
        Parsed Schema object.

    Raises:
        typer.BadParameter: If the schema file is malformed or unreadable.
    """
    try:
        raw = yaml.safe_load(schema_path.read_text(encoding="utf-8"))
    except OSError as exc:
        raise typer.BadParameter(f"Could not read schema file '{schema_path}': {exc}") from exc

    if raw is not None and not isinstance(raw, dict):
        raise typer.BadParameter(f"Schema file '{schema_path}' must be a YAML mapping.")
    return schema_from_mapping(raw)


def read_csv(path: Path) -> pd.DataFrame:
    """Read a CSV using conservative string-preserving defaults.

    Args:
        path: CSV path.

    Returns:
        A DataFrame with string-preserved values.
    """
    return pd.read_csv(path, dtype=str, keep_default_na=False, na_filter=False)