from __future__ import annotations

import functools
import typing as t

from sqlglot import exp
from sqlglot.helper import (
    ensure_list,
    is_date_unit,
    is_iso_date,
    is_iso_datetime,
    seq_get,
)
from sqlglot.optimizer.scope import Scope, traverse_scope
from sqlglot.schema import Schema, ensure_schema
from sqlglot.dialects.dialect import Dialect

if t.TYPE_CHECKING:
    from sqlglot._typing import B, E

    BinaryCoercionFunc = t.Callable[[exp.Expression, exp.Expression], exp.DataType.Type]
    BinaryCoercions = t.Dict[
        t.Tuple[exp.DataType.Type, exp.DataType.Type],
        BinaryCoercionFunc,
    ]

    from sqlglot.dialects.dialect import DialectType, AnnotatorsType


def annotate_types(
    expression: E,
    schema: t.Optional[t.Dict | Schema] = None,
    annotators: t.Optional[AnnotatorsType] = None,
    coerces_to: t.Optional[t.Dict[exp.DataType.Type, t.Set[exp.DataType.Type]]] = None,
    dialect: DialectType = None,
) -> E:
    """
    Infers the types of an expression, annotating its AST accordingly.

    Example:
        >>> import sqlglot
        >>> schema = {"y": {"cola": "SMALLINT"}}
        >>> sql = "SELECT x.cola + 2.5 AS cola FROM (SELECT y.cola AS cola FROM y AS y) AS x"
        >>> annotated_expr = annotate_types(sqlglot.parse_one(sql), schema=schema)
        >>> annotated_expr.expressions[0].type.this  # Get the type of "x.cola + 2.5 AS cola"
        <Type.DOUBLE: 'DOUBLE'>

    Args:
        expression: Expression to annotate.
        schema: Database schema.
        annotators: Maps expression type to corresponding annotation function.
        coerces_to: Maps expression type to set of types that it can be coerced into.

    Returns:
        The expression annotated with types.
    """

    schema = ensure_schema(schema, dialect=dialect)

    return TypeAnnotator(schema, annotators, coerces_to).annotate(expression)


def _coerce_date_literal(l: exp.Expression, unit: t.Optional[exp.Expression]) -> exp.DataType.Type:
    date_text = l.name
    is_iso_date_ = is_iso_date(date_text)

    if is_iso_date_ and is_date_unit(unit):
        return exp.DataType.Type.DATE

    # An ISO date is also an ISO datetime, but not vice versa
    if is_iso_date_ or is_iso_datetime(date_text):
        return exp.DataType.Type.DATETIME

    return exp.DataType.Type.UNKNOWN


def _coerce_date(l: exp.Expression, unit: t.Optional[exp.Expression]) -> exp.DataType.Type:
    if not is_date_unit(unit):
        return exp.DataType.Type.DATETIME
    return l.type.this if l.type else exp.DataType.Type.UNKNOWN


def swap_args(func: BinaryCoercionFunc) -> BinaryCoercionFunc:
    @functools.wraps(func)
    def _swapped(l: exp.Expression, r: exp.Expression) -> exp.DataType.Type:
        return func(r, l)

    return _swapped


def swap_all(coercions: BinaryCoercions) -> BinaryCoercions:
    return {**coercions, **{(b, a): swap_args(func) for (a, b), func in coercions.items()}}


class _TypeAnnotator(type):
    def __new__(cls, clsname, bases, attrs):
        klass = super().__new__(cls, clsname, bases, attrs)

        # Highest-to-lowest type precedence, as specified in Spark's docs (ANSI):
        # https://spark.apache.org/docs/3.2.0/sql-ref-ansi-compliance.html
        text_precedence = (
            exp.DataType.Type.TEXT,
            exp.DataType.Type.NVARCHAR,
            exp.DataType.Type.VARCHAR,
            exp.DataType.Type.NCHAR,
            exp.DataType.Type.CHAR,
        )
        numeric_precedence = (
            exp.DataType.Type.DOUBLE,
            exp.DataType.Type.FLOAT,
            exp.DataType.Type.DECIMAL,
            exp.DataType.Type.BIGINT,
            exp.DataType.Type.INT,
            exp.DataType.Type.SMALLINT,
            exp.DataType.Type.TINYINT,
        )
        timelike_precedence = (
            exp.DataType.Type.TIMESTAMPLTZ,
            exp.DataType.Type.TIMESTAMPTZ,
            exp.DataType.Type.TIMESTAMP,
            exp.DataType.Type.DATETIME,
            exp.DataType.Type.DATE,
        )

        for type_precedence in (text_precedence, numeric_precedence, timelike_precedence):
            coerces_to = set()
            for data_type in type_precedence:
                klass.COERCES_TO[data_type] = coerces_to.copy()
                coerces_to |= {data_type}

        # NULL can be coerced to any type, so e.g. NULL + 1 will have type INT
        klass.COERCES_TO[exp.DataType.Type.NULL] = {
            *text_precedence,
            *numeric_precedence,
            *timelike_precedence,
        }

        return klass


class TypeAnnotator(metaclass=_TypeAnnotator):
    NESTED_TYPES = {
        exp.DataType.Type.ARRAY,
    }

    # Specifies what types a given type can be coerced into (autofilled)
    COERCES_TO: t.Dict[exp.DataType.Type, t.Set[exp.DataType.Type]] = {}

    # Coercion functions for binary operations.
    # Map of type pairs to a callable that takes both sides of the binary operation and returns the resulting type.
    BINARY_COERCIONS: BinaryCoercions = {
        **swap_all(
            {
                (t, exp.DataType.Type.INTERVAL): lambda l, r: _coerce_date_literal(
                    l, r.args.get("unit")
                )
                for t in exp.DataType.TEXT_TYPES
            }
        ),
        **swap_all(
            {
                # text + numeric will yield the numeric type to match most dialects' semantics
                (text, numeric): lambda l, r: t.cast(
                    exp.DataType.Type, l.type if l.type in exp.DataType.NUMERIC_TYPES else r.type
                )
                for text in exp.DataType.TEXT_TYPES
                for numeric in exp.DataType.NUMERIC_TYPES
            }
        ),
        **swap_all(
            {
                (exp.DataType.Type.DATE, exp.DataType.Type.INTERVAL): lambda l, r: _coerce_date(
                    l, r.args.get("unit")
                ),
            }
        ),
    }

    def __init__(
        self,
        schema: Schema,
        annotators: t.Optional[AnnotatorsType] = None,
        coerces_to: t.Optional[t.Dict[exp.DataType.Type, t.Set[exp.DataType.Type]]] = None,
        binary_coercions: t.Optional[BinaryCoercions] = None,
    ) -> None:
        self.schema = schema
        self.annotators = annotators or Dialect.get_or_raise(schema.dialect).ANNOTATORS
        self.coerces_to = (
            coerces_to or Dialect.get_or_raise(schema.dialect).COERCES_TO or self.COERCES_TO
        )
        self.binary_coercions = binary_coercions or self.BINARY_COERCIONS

        # Caches the ids of annotated sub-Expressions, to ensure we only visit them once
        self._visited: t.Set[int] = set()

        # Maps an exp.SetOperation's id (e.g. UNION) to its projection types. This is computed if the
        # exp.SetOperation is the expression of a scope source, as selecting from it multiple times
        # would reprocess the entire subtree to coerce the types of its operands' projections
        self._setop_column_types: t.Dict[int, t.Dict[str, exp.DataType | exp.DataType.Type]] = {}

    def _set_type(
        self, expression: exp.Expression, target_type: t.Optional[exp.DataType | exp.DataType.Type]
    ) -> None:
        expression.type = target_type or exp.DataType.Type.UNKNOWN  # type: ignore
        self._visited.add(id(expression))

    def annotate(self, expression: E) -> E:
        for scope in traverse_scope(expression):
            self.annotate_scope(scope)
        return self._maybe_annotate(expression)  # This takes care of non-traversable expressions

    def annotate_scope(self, scope: Scope) -> None:
        selects = {}
        for name, source in scope.sources.items():
            if not isinstance(source, Scope):
                continue

            expression = source.expression
            if isinstance(expression, exp.UDTF):
                values = []

                if isinstance(expression, exp.Lateral):
                    if isinstance(expression.this, exp.Explode):
                        values = [expression.this.this]
                elif isinstance(expression, exp.Unnest):
                    values = [expression]
                elif not isinstance(expression, exp.TableFromRows):
                    values = expression.expressions[0].expressions

                if not values:
                    continue

                selects[name] = {
                    alias: column.type
                    for alias, column in zip(expression.alias_column_names, values)
                }
            elif isinstance(expression, exp.SetOperation) and len(expression.left.selects) == len(
                expression.right.selects
            ):
                selects[name] = col_types = self._setop_column_types.setdefault(id(expression), {})

                if not col_types:
                    # Process a chain / sub-tree of set operations
                    for set_op in expression.walk(
                        prune=lambda n: not isinstance(n, (exp.SetOperation, exp.Subquery))
                    ):
                        if not isinstance(set_op, exp.SetOperation):
                            continue

                        if set_op.args.get("by_name"):
                            r_type_by_select = {
                                s.alias_or_name: s.type for s in set_op.right.selects
                            }
                            setop_cols = {
                                s.alias_or_name: self._maybe_coerce(
                                    t.cast(exp.DataType, s.type),
                                    r_type_by_select.get(s.alias_or_name)
                                    or exp.DataType.Type.UNKNOWN,
                                )
                                for s in set_op.left.selects
                            }
                        else:
                            setop_cols = {
                                ls.alias_or_name: self._maybe_coerce(
                                    t.cast(exp.DataType, ls.type), t.cast(exp.DataType, rs.type)
                                )
                                for ls, rs in zip(set_op.left.selects, set_op.right.selects)
                            }

                        # Coerce intermediate results with the previously registered types, if they exist
                        for col_name, col_type in setop_cols.items():
                            col_types[col_name] = self._maybe_coerce(
                                col_type, col_types.get(col_name, exp.DataType.Type.NULL)
                            )

            else:
                selects[name] = {s.alias_or_name: s.type for s in expression.selects}

        # First annotate the current scope's column references
        for col in scope.columns:
            if not col.table:
                continue

            source = scope.sources.get(col.table)
            if isinstance(source, exp.Table):
                self._set_type(col, self.schema.get_column_type(source, col))
            elif source:
                if col.table in selects and col.name in selects[col.table]:
                    self._set_type(col, selects[col.table][col.name])
                elif isinstance(source.expression, exp.Unnest):
                    self._set_type(col, source.expression.type)

        # Then (possibly) annotate the remaining expressions in the scope
        self._maybe_annotate(scope.expression)

    def _maybe_annotate(self, expression: E) -> E:
        if id(expression) in self._visited:
            return expression  # We've already inferred the expression's type

        annotator = self.annotators.get(expression.__class__)

        return (
            annotator(self, expression)
            if annotator
            else self._annotate_with_type(expression, exp.DataType.Type.UNKNOWN)
        )

    def _annotate_args(self, expression: E) -> E:
        for value in expression.iter_expressions():
            self._maybe_annotate(value)

        return expression

    def _maybe_coerce(
        self,
        type1: exp.DataType | exp.DataType.Type,
        type2: exp.DataType | exp.DataType.Type,
    ) -> exp.DataType | exp.DataType.Type:
        """
        Returns type2 if type1 can be coerced into it, otherwise type1.

        If either type is parameterized (e.g. DECIMAL(18, 2) contains two parameters),
        we assume type1 does not coerce into type2, so we also return it in this case.
        """
        if isinstance(type1, exp.DataType):
            if type1.expressions:
                return type1
            type1_value = type1.this
        else:
            type1_value = type1

        if isinstance(type2, exp.DataType):
            if type2.expressions:
                return type1
            type2_value = type2.this
        else:
            type2_value = type2

        # We propagate the UNKNOWN type upwards if found
        if exp.DataType.Type.UNKNOWN in (type1_value, type2_value):
            return exp.DataType.Type.UNKNOWN

        return type2_value if type2_value in self.coerces_to.get(type1_value, {}) else type1_value

    def _annotate_binary(self, expression: B) -> B:
        self._annotate_args(expression)

        left, right = expression.left, expression.right
        left_type, right_type = left.type.this, right.type.this  # type: ignore

        if isinstance(expression, (exp.Connector, exp.Predicate)):
            self._set_type(expression, exp.DataType.Type.BOOLEAN)
        elif (left_type, right_type) in self.binary_coercions:
            self._set_type(expression, self.binary_coercions[(left_type, right_type)](left, right))
        else:
            self._set_type(expression, self._maybe_coerce(left_type, right_type))

        return expression

    def _annotate_unary(self, expression: E) -> E:
        self._annotate_args(expression)

        if isinstance(expression, exp.Not):
            self._set_type(expression, exp.DataType.Type.BOOLEAN)
        else:
            self._set_type(expression, expression.this.type)

        return expression

    def _annotate_literal(self, expression: exp.Literal) -> exp.Literal:
        if expression.is_string:
            self._set_type(expression, exp.DataType.Type.VARCHAR)
        elif expression.is_int:
            self._set_type(expression, exp.DataType.Type.INT)
        else:
            self._set_type(expression, exp.DataType.Type.DOUBLE)

        return expression

    def _annotate_with_type(
        self, expression: E, target_type: exp.DataType | exp.DataType.Type
    ) -> E:
        self._set_type(expression, target_type)
        return self._annotate_args(expression)

    @t.no_type_check
    def _annotate_by_args(
        self,
        expression: E,
        *args: str,
        promote: bool = False,
        array: bool = False,
    ) -> E:
        self._annotate_args(expression)

        expressions: t.List[exp.Expression] = []
        for arg in args:
            arg_expr = expression.args.get(arg)
            expressions.extend(expr for expr in ensure_list(arg_expr) if expr)

        last_datatype = None
        for expr in expressions:
            expr_type = expr.type

            # Stop at the first nested data type found - we don't want to _maybe_coerce nested types
            if expr_type.args.get("nested"):
                last_datatype = expr_type
                break

            if not expr_type.is_type(exp.DataType.Type.UNKNOWN):
                last_datatype = self._maybe_coerce(last_datatype or expr_type, expr_type)

        self._set_type(expression, last_datatype or exp.DataType.Type.UNKNOWN)

        if promote:
            if expression.type.this in exp.DataType.INTEGER_TYPES:
                self._set_type(expression, exp.DataType.Type.BIGINT)
            elif expression.type.this in exp.DataType.FLOAT_TYPES:
                self._set_type(expression, exp.DataType.Type.DOUBLE)

        if array:
            self._set_type(
                expression,
                exp.DataType(
                    this=exp.DataType.Type.ARRAY, expressions=[expression.type], nested=True
                ),
            )

        return expression

    def _annotate_timeunit(
        self, expression: exp.TimeUnit | exp.DateTrunc
    ) -> exp.TimeUnit | exp.DateTrunc:
        self._annotate_args(expression)

        if expression.this.type.this in exp.DataType.TEXT_TYPES:
            datatype = _coerce_date_literal(expression.this, expression.unit)
        elif expression.this.type.this in exp.DataType.TEMPORAL_TYPES:
            datatype = _coerce_date(expression.this, expression.unit)
        else:
            datatype = exp.DataType.Type.UNKNOWN

        self._set_type(expression, datatype)
        return expression

    def _annotate_bracket(self, expression: exp.Bracket) -> exp.Bracket:
        self._annotate_args(expression)

        bracket_arg = expression.expressions[0]
        this = expression.this

        if isinstance(bracket_arg, exp.Slice):
            self._set_type(expression, this.type)
        elif this.type.is_type(exp.DataType.Type.ARRAY):
            self._set_type(expression, seq_get(this.type.expressions, 0))
        elif isinstance(this, (exp.Map, exp.VarMap)) and bracket_arg in this.keys:
            index = this.keys.index(bracket_arg)
            value = seq_get(this.values, index)
            self._set_type(expression, value.type if value else None)
        else:
            self._set_type(expression, exp.DataType.Type.UNKNOWN)

        return expression

    def _annotate_div(self, expression: exp.Div) -> exp.Div:
        self._annotate_args(expression)

        left_type, right_type = expression.left.type.this, expression.right.type.this  # type: ignore

        if (
            expression.args.get("typed")
            and left_type in exp.DataType.INTEGER_TYPES
            and right_type in exp.DataType.INTEGER_TYPES
        ):
            self._set_type(expression, exp.DataType.Type.BIGINT)
        else:
            self._set_type(expression, self._maybe_coerce(left_type, right_type))
            if expression.type and expression.type.this not in exp.DataType.REAL_TYPES:
                self._set_type(
                    expression, self._maybe_coerce(expression.type, exp.DataType.Type.DOUBLE)
                )

        return expression

    def _annotate_dot(self, expression: exp.Dot) -> exp.Dot:
        self._annotate_args(expression)
        self._set_type(expression, None)
        this_type = expression.this.type

        if this_type and this_type.is_type(exp.DataType.Type.STRUCT):
            for e in this_type.expressions:
                if e.name == expression.expression.name:
                    self._set_type(expression, e.kind)
                    break

        return expression

    def _annotate_explode(self, expression: exp.Explode) -> exp.Explode:
        self._annotate_args(expression)
        self._set_type(expression, seq_get(expression.this.type.expressions, 0))
        return expression

    def _annotate_unnest(self, expression: exp.Unnest) -> exp.Unnest:
        self._annotate_args(expression)
        child = seq_get(expression.expressions, 0)

        if child and child.is_type(exp.DataType.Type.ARRAY):
            expr_type = seq_get(child.type.expressions, 0)
        else:
            expr_type = None

        self._set_type(expression, expr_type)
        return expression

    def _annotate_struct_value(
        self, expression: exp.Expression
    ) -> t.Optional[exp.DataType] | exp.ColumnDef:
        alias = expression.args.get("alias")
        if alias:
            return exp.ColumnDef(this=alias.copy(), kind=expression.type)

        # Case: key = value or key := value
        if expression.expression:
            return exp.ColumnDef(this=expression.this.copy(), kind=expression.expression.type)

        return expression.type

    def _annotate_struct(self, expression: exp.Struct) -> exp.Struct:
        self._annotate_args(expression)
        self._set_type(
            expression,
            exp.DataType(
                this=exp.DataType.Type.STRUCT,
                expressions=[self._annotate_struct_value(expr) for expr in expression.expressions],
                nested=True,
            ),
        )
        return expression

    @t.overload
    def _annotate_map(self, expression: exp.Map) -> exp.Map: ...

    @t.overload
    def _annotate_map(self, expression: exp.VarMap) -> exp.VarMap: ...

    def _annotate_map(self, expression):
        self._annotate_args(expression)

        keys = expression.args.get("keys")
        values = expression.args.get("values")

        map_type = exp.DataType(this=exp.DataType.Type.MAP)
        if isinstance(keys, exp.Array) and isinstance(values, exp.Array):
            key_type = seq_get(keys.type.expressions, 0) or exp.DataType.Type.UNKNOWN
            value_type = seq_get(values.type.expressions, 0) or exp.DataType.Type.UNKNOWN

            if key_type != exp.DataType.Type.UNKNOWN and value_type != exp.DataType.Type.UNKNOWN:
                map_type.set("expressions", [key_type, value_type])
                map_type.set("nested", True)

        self._set_type(expression, map_type)
        return expression

    def _annotate_to_map(self, expression: exp.ToMap) -> exp.ToMap:
        self._annotate_args(expression)

        map_type = exp.DataType(this=exp.DataType.Type.MAP)
        arg = expression.this
        if arg.is_type(exp.DataType.Type.STRUCT):
            for coldef in arg.type.expressions:
                kind = coldef.kind
                if kind != exp.DataType.Type.UNKNOWN:
                    map_type.set("expressions", [exp.DataType.build("varchar"), kind])
                    map_type.set("nested", True)
                    break

        self._set_type(expression, map_type)
        return expression

    def _annotate_extract(self, expression: exp.Extract) -> exp.Extract:
        self._annotate_args(expression)
        part = expression.name
        if part == "TIME":
            self._set_type(expression, exp.DataType.Type.TIME)
        elif part == "DATE":
            self._set_type(expression, exp.DataType.Type.DATE)
        else:
            self._set_type(expression, exp.DataType.Type.INT)
        return expression
