from __future__ import annotations

import abc
import typing as t

from sqlglot import expressions as exp
from sqlglot.dialects.dialect import Dialect
from sqlglot.errors import SchemaError
from sqlglot.helper import dict_depth
from sqlglot.trie import TrieResult, in_trie, new_trie

if t.TYPE_CHECKING:
    from sqlglot.dataframe.sql.types import StructType
    from sqlglot.dialects.dialect import DialectType

    ColumnMapping = t.Union[t.Dict, str, StructType, t.List]


class Schema(abc.ABC):
    """Abstract base class for database schemas"""

    dialect: DialectType

    @abc.abstractmethod
    def add_table(
        self,
        table: exp.Table | str,
        column_mapping: t.Optional[ColumnMapping] = None,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
        match_depth: bool = True,
    ) -> None:
        """
        Register or update a table. Some implementing classes may require column information to also be provided.
        The added table must have the necessary number of qualifiers in its path to match the schema's nesting level.

        Args:
            table: the `Table` expression instance or string representing the table.
            column_mapping: a column mapping that describes the structure of the table.
            dialect: the SQL dialect that will be used to parse `table` if it's a string.
            normalize: whether to normalize identifiers according to the dialect of interest.
            match_depth: whether to enforce that the table must match the schema's depth or not.
        """

    @abc.abstractmethod
    def column_names(
        self,
        table: exp.Table | str,
        only_visible: bool = False,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> t.Sequence[str]:
        """
        Get the column names for a table.

        Args:
            table: the `Table` expression instance.
            only_visible: whether to include invisible columns.
            dialect: the SQL dialect that will be used to parse `table` if it's a string.
            normalize: whether to normalize identifiers according to the dialect of interest.

        Returns:
            The sequence of column names.
        """

    @abc.abstractmethod
    def get_column_type(
        self,
        table: exp.Table | str,
        column: exp.Column | str,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> exp.DataType:
        """
        Get the `sqlglot.exp.DataType` type of a column in the schema.

        Args:
            table: the source table.
            column: the target column.
            dialect: the SQL dialect that will be used to parse `table` if it's a string.
            normalize: whether to normalize identifiers according to the dialect of interest.

        Returns:
            The resulting column type.
        """

    def has_column(
        self,
        table: exp.Table | str,
        column: exp.Column | str,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> bool:
        """
        Returns whether `column` appears in `table`'s schema.

        Args:
            table: the source table.
            column: the target column.
            dialect: the SQL dialect that will be used to parse `table` if it's a string.
            normalize: whether to normalize identifiers according to the dialect of interest.

        Returns:
            True if the column appears in the schema, False otherwise.
        """
        name = column if isinstance(column, str) else column.name
        return name in self.column_names(table, dialect=dialect, normalize=normalize)

    @property
    @abc.abstractmethod
    def supported_table_args(self) -> t.Tuple[str, ...]:
        """
        Table arguments this schema support, e.g. `("this", "db", "catalog")`
        """

    @property
    def empty(self) -> bool:
        """Returns whether the schema is empty."""
        return True


class AbstractMappingSchema:
    def __init__(
        self,
        mapping: t.Optional[t.Dict] = None,
    ) -> None:
        self.mapping = mapping or {}
        self.mapping_trie = new_trie(
            tuple(reversed(t)) for t in flatten_schema(self.mapping, depth=self.depth())
        )
        self._supported_table_args: t.Tuple[str, ...] = tuple()

    @property
    def empty(self) -> bool:
        return not self.mapping

    def depth(self) -> int:
        return dict_depth(self.mapping)

    @property
    def supported_table_args(self) -> t.Tuple[str, ...]:
        if not self._supported_table_args and self.mapping:
            depth = self.depth()

            if not depth:  # None
                self._supported_table_args = tuple()
            elif 1 <= depth <= 3:
                self._supported_table_args = exp.TABLE_PARTS[:depth]
            else:
                raise SchemaError(f"Invalid mapping shape. Depth: {depth}")

        return self._supported_table_args

    def table_parts(self, table: exp.Table) -> t.List[str]:
        if isinstance(table.this, exp.ReadCSV):
            return [table.this.name]
        return [table.text(part) for part in exp.TABLE_PARTS if table.text(part)]

    def find(self, table: exp.Table, raise_on_missing: bool = True) -> t.Optional[t.Any]:
        """
        Returns the schema of a given table.

        Args:
            table: the target table.
            raise_on_missing: whether to raise in case the schema is not found.

        Returns:
            The schema of the target table.
        """
        parts = self.table_parts(table)[0 : len(self.supported_table_args)]
        value, trie = in_trie(self.mapping_trie, parts)

        if value == TrieResult.FAILED:
            return None

        if value == TrieResult.PREFIX:
            possibilities = flatten_schema(trie, depth=dict_depth(trie) - 1)

            if len(possibilities) == 1:
                parts.extend(possibilities[0])
            else:
                message = ", ".join(".".join(parts) for parts in possibilities)
                if raise_on_missing:
                    raise SchemaError(f"Ambiguous mapping for {table}: {message}.")
                return None

        return self.nested_get(parts, raise_on_missing=raise_on_missing)

    def nested_get(
        self, parts: t.Sequence[str], d: t.Optional[t.Dict] = None, raise_on_missing=True
    ) -> t.Optional[t.Any]:
        return nested_get(
            d or self.mapping,
            *zip(self.supported_table_args, reversed(parts)),
            raise_on_missing=raise_on_missing,
        )


class MappingSchema(AbstractMappingSchema, Schema):
    """
    Schema based on a nested mapping.

    Args:
        schema: Mapping in one of the following forms:
            1. {table: {col: type}}
            2. {db: {table: {col: type}}}
            3. {catalog: {db: {table: {col: type}}}}
            4. None - Tables will be added later
        visible: Optional mapping of which columns in the schema are visible. If not provided, all columns
            are assumed to be visible. The nesting should mirror that of the schema:
            1. {table: set(*cols)}}
            2. {db: {table: set(*cols)}}}
            3. {catalog: {db: {table: set(*cols)}}}}
        dialect: The dialect to be used for custom type mappings & parsing string arguments.
        normalize: Whether to normalize identifier names according to the given dialect or not.
    """

    def __init__(
        self,
        schema: t.Optional[t.Dict] = None,
        visible: t.Optional[t.Dict] = None,
        dialect: DialectType = None,
        normalize: bool = True,
    ) -> None:
        self.dialect = dialect
        self.visible = {} if visible is None else visible
        self.normalize = normalize
        self._type_mapping_cache: t.Dict[str, exp.DataType] = {}
        self._depth = 0
        schema = {} if schema is None else schema

        super().__init__(self._normalize(schema) if self.normalize else schema)

    @classmethod
    def from_mapping_schema(cls, mapping_schema: MappingSchema) -> MappingSchema:
        return MappingSchema(
            schema=mapping_schema.mapping,
            visible=mapping_schema.visible,
            dialect=mapping_schema.dialect,
            normalize=mapping_schema.normalize,
        )

    def copy(self, **kwargs) -> MappingSchema:
        return MappingSchema(
            **{  # type: ignore
                "schema": self.mapping.copy(),
                "visible": self.visible.copy(),
                "dialect": self.dialect,
                "normalize": self.normalize,
                **kwargs,
            }
        )

    def add_table(
        self,
        table: exp.Table | str,
        column_mapping: t.Optional[ColumnMapping] = None,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
        match_depth: bool = True,
    ) -> None:
        """
        Register or update a table. Updates are only performed if a new column mapping is provided.
        The added table must have the necessary number of qualifiers in its path to match the schema's nesting level.

        Args:
            table: the `Table` expression instance or string representing the table.
            column_mapping: a column mapping that describes the structure of the table.
            dialect: the SQL dialect that will be used to parse `table` if it's a string.
            normalize: whether to normalize identifiers according to the dialect of interest.
            match_depth: whether to enforce that the table must match the schema's depth or not.
        """
        normalized_table = self._normalize_table(table, dialect=dialect, normalize=normalize)

        if match_depth and not self.empty and len(normalized_table.parts) != self.depth():
            raise SchemaError(
                f"Table {normalized_table.sql(dialect=self.dialect)} must match the "
                f"schema's nesting level: {self.depth()}."
            )

        normalized_column_mapping = {
            self._normalize_name(key, dialect=dialect, normalize=normalize): value
            for key, value in ensure_column_mapping(column_mapping).items()
        }

        schema = self.find(normalized_table, raise_on_missing=False)
        if schema and not normalized_column_mapping:
            return

        parts = self.table_parts(normalized_table)

        nested_set(self.mapping, tuple(reversed(parts)), normalized_column_mapping)
        new_trie([parts], self.mapping_trie)

    def column_names(
        self,
        table: exp.Table | str,
        only_visible: bool = False,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> t.List[str]:
        normalized_table = self._normalize_table(table, dialect=dialect, normalize=normalize)

        schema = self.find(normalized_table)
        if schema is None:
            return []

        if not only_visible or not self.visible:
            return list(schema)

        visible = self.nested_get(self.table_parts(normalized_table), self.visible) or []
        return [col for col in schema if col in visible]

    def get_column_type(
        self,
        table: exp.Table | str,
        column: exp.Column | str,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> exp.DataType:
        normalized_table = self._normalize_table(table, dialect=dialect, normalize=normalize)

        normalized_column_name = self._normalize_name(
            column if isinstance(column, str) else column.this, dialect=dialect, normalize=normalize
        )

        table_schema = self.find(normalized_table, raise_on_missing=False)
        if table_schema:
            column_type = table_schema.get(normalized_column_name)

            if isinstance(column_type, exp.DataType):
                return column_type
            elif isinstance(column_type, str):
                return self._to_data_type(column_type, dialect=dialect)

        return exp.DataType.build("unknown")

    def has_column(
        self,
        table: exp.Table | str,
        column: exp.Column | str,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> bool:
        normalized_table = self._normalize_table(table, dialect=dialect, normalize=normalize)

        normalized_column_name = self._normalize_name(
            column if isinstance(column, str) else column.this, dialect=dialect, normalize=normalize
        )

        table_schema = self.find(normalized_table, raise_on_missing=False)
        return normalized_column_name in table_schema if table_schema else False

    def _normalize(self, schema: t.Dict) -> t.Dict:
        """
        Normalizes all identifiers in the schema.

        Args:
            schema: the schema to normalize.

        Returns:
            The normalized schema mapping.
        """
        normalized_mapping: t.Dict = {}
        flattened_schema = flatten_schema(schema, depth=dict_depth(schema) - 1)

        for keys in flattened_schema:
            columns = nested_get(schema, *zip(keys, keys))

            if not isinstance(columns, dict):
                raise SchemaError(
                    f"Table {'.'.join(keys[:-1])} must match the schema's nesting level: {len(flattened_schema[0])}."
                )

            normalized_keys = [self._normalize_name(key, is_table=True) for key in keys]
            for column_name, column_type in columns.items():
                nested_set(
                    normalized_mapping,
                    normalized_keys + [self._normalize_name(column_name)],
                    column_type,
                )

        return normalized_mapping

    def _normalize_table(
        self,
        table: exp.Table | str,
        dialect: DialectType = None,
        normalize: t.Optional[bool] = None,
    ) -> exp.Table:
        dialect = dialect or self.dialect
        normalize = self.normalize if normalize is None else normalize

        normalized_table = exp.maybe_parse(table, into=exp.Table, dialect=dialect, copy=normalize)

        if normalize:
            for arg in exp.TABLE_PARTS:
                value = normalized_table.args.get(arg)
                if isinstance(value, exp.Identifier):
                    normalized_table.set(
                        arg,
                        normalize_name(value, dialect=dialect, is_table=True, normalize=normalize),
                    )

        return normalized_table

    def _normalize_name(
        self,
        name: str | exp.Identifier,
        dialect: DialectType = None,
        is_table: bool = False,
        normalize: t.Optional[bool] = None,
    ) -> str:
        return normalize_name(
            name,
            dialect=dialect or self.dialect,
            is_table=is_table,
            normalize=self.normalize if normalize is None else normalize,
        ).name

    def depth(self) -> int:
        if not self.empty and not self._depth:
            # The columns themselves are a mapping, but we don't want to include those
            self._depth = super().depth() - 1
        return self._depth

    def _to_data_type(self, schema_type: str, dialect: DialectType = None) -> exp.DataType:
        """
        Convert a type represented as a string to the corresponding `sqlglot.exp.DataType` object.

        Args:
            schema_type: the type we want to convert.
            dialect: the SQL dialect that will be used to parse `schema_type`, if needed.

        Returns:
            The resulting expression type.
        """
        if schema_type not in self._type_mapping_cache:
            dialect = dialect or self.dialect
            udt = Dialect.get_or_raise(dialect).SUPPORTS_USER_DEFINED_TYPES

            try:
                expression = exp.DataType.build(schema_type, dialect=dialect, udt=udt)
                self._type_mapping_cache[schema_type] = expression
            except AttributeError:
                in_dialect = f" in dialect {dialect}" if dialect else ""
                raise SchemaError(f"Failed to build type '{schema_type}'{in_dialect}.")

        return self._type_mapping_cache[schema_type]


def normalize_name(
    identifier: str | exp.Identifier,
    dialect: DialectType = None,
    is_table: bool = False,
    normalize: t.Optional[bool] = True,
) -> exp.Identifier:
    if isinstance(identifier, str):
        identifier = exp.parse_identifier(identifier, dialect=dialect)

    if not normalize:
        return identifier

    # this is used for normalize_identifier, bigquery has special rules pertaining tables
    identifier.meta["is_table"] = is_table
    return Dialect.get_or_raise(dialect).normalize_identifier(identifier)


def ensure_schema(schema: Schema | t.Optional[t.Dict], **kwargs: t.Any) -> Schema:
    if isinstance(schema, Schema):
        return schema

    return MappingSchema(schema, **kwargs)


def ensure_column_mapping(mapping: t.Optional[ColumnMapping]) -> t.Dict:
    if mapping is None:
        return {}
    elif isinstance(mapping, dict):
        return mapping
    elif isinstance(mapping, str):
        col_name_type_strs = [x.strip() for x in mapping.split(",")]
        return {
            name_type_str.split(":")[0].strip(): name_type_str.split(":")[1].strip()
            for name_type_str in col_name_type_strs
        }
    # Check if mapping looks like a DataFrame StructType
    elif hasattr(mapping, "simpleString"):
        return {struct_field.name: struct_field.dataType.simpleString() for struct_field in mapping}
    elif isinstance(mapping, list):
        return {x.strip(): None for x in mapping}

    raise ValueError(f"Invalid mapping provided: {type(mapping)}")


def flatten_schema(
    schema: t.Dict, depth: int, keys: t.Optional[t.List[str]] = None
) -> t.List[t.List[str]]:
    tables = []
    keys = keys or []

    for k, v in schema.items():
        if depth >= 2:
            tables.extend(flatten_schema(v, depth - 1, keys + [k]))
        elif depth == 1:
            tables.append(keys + [k])

    return tables


def nested_get(
    d: t.Dict, *path: t.Tuple[str, str], raise_on_missing: bool = True
) -> t.Optional[t.Any]:
    """
    Get a value for a nested dictionary.

    Args:
        d: the dictionary to search.
        *path: tuples of (name, key), where:
            `key` is the key in the dictionary to get.
            `name` is a string to use in the error if `key` isn't found.

    Returns:
        The value or None if it doesn't exist.
    """
    for name, key in path:
        d = d.get(key)  # type: ignore
        if d is None:
            if raise_on_missing:
                name = "table" if name == "this" else name
                raise ValueError(f"Unknown {name}: {key}")
            return None

    return d


def nested_set(d: t.Dict, keys: t.Sequence[str], value: t.Any) -> t.Dict:
    """
    In-place set a value for a nested dictionary

    Example:
        >>> nested_set({}, ["top_key", "second_key"], "value")
        {'top_key': {'second_key': 'value'}}

        >>> nested_set({"top_key": {"third_key": "third_value"}}, ["top_key", "second_key"], "value")
        {'top_key': {'third_key': 'third_value', 'second_key': 'value'}}

    Args:
        d: dictionary to update.
        keys: the keys that makeup the path to `value`.
        value: the value to set in the dictionary for the given key path.

    Returns:
        The (possibly) updated dictionary.
    """
    if not keys:
        return d

    if len(keys) == 1:
        d[keys[0]] = value
        return d

    subd = d
    for key in keys[:-1]:
        if key not in subd:
            subd = subd.setdefault(key, {})
        else:
            subd = subd[key]

    subd[keys[-1]] = value
    return d
