from abc import ABC, abstractmethod
import sys
from typing import (
    IO,
    TYPE_CHECKING,
    Iterable,
    Iterator,
    List,
    Mapping,
    Optional,
    Sequence,
    Union,
)

from pandas._config import get_option

from pandas._typing import Dtype, FrameOrSeriesUnion

from pandas.core.indexes.api import Index

from pandas.io.formats import format as fmt
from pandas.io.formats.printing import pprint_thing

if TYPE_CHECKING:
    from pandas.core.frame import DataFrame


def _put_str(s: Union[str, Dtype], space: int) -> str:
    """
    Make string of specified length, padding to the right if necessary.

    Parameters
    ----------
    s : Union[str, Dtype]
        String to be formatted.
    space : int
        Length to force string to be of.

    Returns
    -------
    str
        String coerced to given length.

    Examples
    --------
    >>> pd.io.formats.info._put_str("panda", 6)
    'panda '
    >>> pd.io.formats.info._put_str("panda", 4)
    'pand'
    """
    return str(s)[:space].ljust(space)


def _sizeof_fmt(num: Union[int, float], size_qualifier: str) -> str:
    """
    Return size in human readable format.

    Parameters
    ----------
    num : int
        Size in bytes.
    size_qualifier : str
        Either empty, or '+' (if lower bound).

    Returns
    -------
    str
        Size in human readable format.

    Examples
    --------
    >>> _sizeof_fmt(23028, '')
    '22.5 KB'

    >>> _sizeof_fmt(23028, '+')
    '22.5+ KB'
    """
    for x in ["bytes", "KB", "MB", "GB", "TB"]:
        if num < 1024.0:
            return f"{num:3.1f}{size_qualifier} {x}"
        num /= 1024.0
    return f"{num:3.1f}{size_qualifier} PB"


def _initialize_memory_usage(
    memory_usage: Optional[Union[bool, str]] = None,
) -> Union[bool, str]:
    """Get memory usage based on inputs and display options."""
    if memory_usage is None:
        memory_usage = get_option("display.memory_usage")
    return memory_usage


class BaseInfo(ABC):
    """
    Base class for DataFrameInfo and SeriesInfo.

    Parameters
    ----------
    data : DataFrame or Series
        Either dataframe or series.
    memory_usage : bool or str, optional
        If "deep", introspect the data deeply by interrogating object dtypes
        for system-level memory consumption, and include it in the returned
        values.
    """

    data: FrameOrSeriesUnion
    memory_usage: Union[bool, str]

    @property
    @abstractmethod
    def dtypes(self) -> Iterable[Dtype]:
        """
        Dtypes.

        Returns
        -------
        dtypes : sequence
            Dtype of each of the DataFrame's columns (or one series column).
        """

    @property
    @abstractmethod
    def dtype_counts(self) -> Mapping[str, int]:
        """Mapping dtype - number of counts."""

    @property
    @abstractmethod
    def non_null_counts(self) -> Sequence[int]:
        """Sequence of non-null counts for all columns or column (if series)."""

    @property
    @abstractmethod
    def memory_usage_bytes(self) -> int:
        """
        Memory usage in bytes.

        Returns
        -------
        memory_usage_bytes : int
            Object's total memory usage in bytes.
        """

    @property
    def memory_usage_string(self) -> str:
        """Memory usage in a form of human readable string."""
        return f"{_sizeof_fmt(self.memory_usage_bytes, self.size_qualifier)}\n"

    @property
    def size_qualifier(self) -> str:
        size_qualifier = ""
        if self.memory_usage:
            if self.memory_usage != "deep":
                # size_qualifier is just a best effort; not guaranteed to catch
                # all cases (e.g., it misses categorical data even with object
                # categories)
                if (
                    "object" in self.dtype_counts
                    or self.data.index._is_memory_usage_qualified()
                ):
                    size_qualifier = "+"
        return size_qualifier

    @abstractmethod
    def render(
        self,
        *,
        buf: Optional[IO[str]],
        max_cols: Optional[int],
        verbose: Optional[bool],
        show_counts: Optional[bool],
    ) -> None:
        """
        Print a concise summary of a %(klass)s.

        This method prints information about a %(klass)s including
        the index dtype%(type_sub)s, non-null values and memory usage.
        %(version_added_sub)s\

        Parameters
        ----------
        data : %(klass)s
            %(klass)s to print information about.
        verbose : bool, optional
            Whether to print the full summary. By default, the setting in
            ``pandas.options.display.max_info_columns`` is followed.
        buf : writable buffer, defaults to sys.stdout
            Where to send the output. By default, the output is printed to
            sys.stdout. Pass a writable buffer if you need to further process
            the output.
        %(max_cols_sub)s
        memory_usage : bool, str, optional
            Specifies whether total memory usage of the %(klass)s
            elements (including the index) should be displayed. By default,
            this follows the ``pandas.options.display.memory_usage`` setting.

            True always show memory usage. False never shows memory usage.
            A value of 'deep' is equivalent to "True with deep introspection".
            Memory usage is shown in human-readable units (base-2
            representation). Without deep introspection a memory estimation is
            made based in column dtype and number of rows assuming values
            consume the same memory amount for corresponding dtypes. With deep
            memory introspection, a real memory usage calculation is performed
            at the cost of computational resources.
        %(show_counts_sub)s

        Returns
        -------
        None
            This method prints a summary of a %(klass)s and returns None.

        See Also
        --------
        %(see_also_sub)s

        Examples
        --------
        %(examples_sub)s
        """


class DataFrameInfo(BaseInfo):
    """
    Class storing dataframe-specific info.
    """

    def __init__(
        self,
        data: "DataFrame",
        memory_usage: Optional[Union[bool, str]] = None,
    ):
        self.data: "DataFrame" = data
        self.memory_usage = _initialize_memory_usage(memory_usage)

    @property
    def dtype_counts(self) -> Mapping[str, int]:
        return _get_dataframe_dtype_counts(self.data)

    @property
    def dtypes(self) -> Iterable[Dtype]:
        """
        Dtypes.

        Returns
        -------
        dtypes
            Dtype of each of the DataFrame's columns.
        """
        return self.data.dtypes

    @property
    def ids(self) -> Index:
        """
        Column names.

        Returns
        -------
        ids : Index
            DataFrame's column names.
        """
        return self.data.columns

    @property
    def col_count(self) -> int:
        """Number of columns to be summarized."""
        return len(self.ids)

    @property
    def non_null_counts(self) -> Sequence[int]:
        """Sequence of non-null counts for all columns or column (if series)."""
        return self.data.count()

    @property
    def memory_usage_bytes(self) -> int:
        if self.memory_usage == "deep":
            deep = True
        else:
            deep = False
        return self.data.memory_usage(index=True, deep=deep).sum()

    def render(
        self,
        *,
        buf: Optional[IO[str]],
        max_cols: Optional[int],
        verbose: Optional[bool],
        show_counts: Optional[bool],
    ) -> None:
        printer = DataFrameInfoPrinter(
            info=self,
            max_cols=max_cols,
            verbose=verbose,
            show_counts=show_counts,
        )
        printer.to_buffer(buf)


class InfoPrinterAbstract:
    """
    Class for printing dataframe or series info.
    """

    def to_buffer(self, buf: Optional[IO[str]] = None) -> None:
        """Save dataframe info into buffer."""
        table_builder = self._create_table_builder()
        lines = table_builder.get_lines()
        if buf is None:  # pragma: no cover
            buf = sys.stdout
        fmt.buffer_put_lines(buf, lines)

    @abstractmethod
    def _create_table_builder(self) -> "TableBuilderAbstract":
        """Create instance of table builder."""


class DataFrameInfoPrinter(InfoPrinterAbstract):
    """
    Class for printing dataframe info.

    Parameters
    ----------
    info : DataFrameInfo
        Instance of DataFrameInfo.
    max_cols : int, optional
        When to switch from the verbose to the truncated output.
    verbose : bool, optional
        Whether to print the full summary.
    show_counts : bool, optional
        Whether to show the non-null counts.
    """

    def __init__(
        self,
        info: DataFrameInfo,
        max_cols: Optional[int] = None,
        verbose: Optional[bool] = None,
        show_counts: Optional[bool] = None,
    ):
        self.info = info
        self.data = info.data
        self.verbose = verbose
        self.max_cols = self._initialize_max_cols(max_cols)
        self.show_counts = self._initialize_show_counts(show_counts)

    @property
    def max_rows(self) -> int:
        """Maximum info rows to be displayed."""
        return get_option("display.max_info_rows", len(self.data) + 1)

    @property
    def exceeds_info_cols(self) -> bool:
        """Check if number of columns to be summarized does not exceed maximum."""
        return bool(self.col_count > self.max_cols)

    @property
    def exceeds_info_rows(self) -> bool:
        """Check if number of rows to be summarized does not exceed maximum."""
        return bool(len(self.data) > self.max_rows)

    @property
    def col_count(self) -> int:
        """Number of columns to be summarized."""
        return self.info.col_count

    def _initialize_max_cols(self, max_cols: Optional[int]) -> int:
        if max_cols is None:
            return get_option("display.max_info_columns", self.col_count + 1)
        return max_cols

    def _initialize_show_counts(self, show_counts: Optional[bool]) -> bool:
        if show_counts is None:
            return bool(not self.exceeds_info_cols and not self.exceeds_info_rows)
        else:
            return show_counts

    def _create_table_builder(self) -> "DataFrameTableBuilder":
        """
        Create instance of table builder based on verbosity and display settings.
        """
        if self.verbose:
            return DataFrameTableBuilderVerbose(
                info=self.info,
                with_counts=self.show_counts,
            )
        elif self.verbose is False:  # specifically set to False, not necessarily None
            return DataFrameTableBuilderNonVerbose(info=self.info)
        else:
            if self.exceeds_info_cols:
                return DataFrameTableBuilderNonVerbose(info=self.info)
            else:
                return DataFrameTableBuilderVerbose(
                    info=self.info,
                    with_counts=self.show_counts,
                )


class TableBuilderAbstract(ABC):
    """
    Abstract builder for info table.
    """

    _lines: List[str]
    info: BaseInfo

    @abstractmethod
    def get_lines(self) -> List[str]:
        """Product in a form of list of lines (strings)."""

    @property
    def data(self) -> FrameOrSeriesUnion:
        return self.info.data

    @property
    def dtypes(self) -> Iterable[Dtype]:
        """Dtypes of each of the DataFrame's columns."""
        return self.info.dtypes

    @property
    def dtype_counts(self) -> Mapping[str, int]:
        """Mapping dtype - number of counts."""
        return self.info.dtype_counts

    @property
    def display_memory_usage(self) -> bool:
        """Whether to display memory usage."""
        return bool(self.info.memory_usage)

    @property
    def memory_usage_string(self) -> str:
        """Memory usage string with proper size qualifier."""
        return self.info.memory_usage_string

    @property
    def non_null_counts(self) -> Sequence[int]:
        return self.info.non_null_counts

    def add_object_type_line(self) -> None:
        """Add line with string representation of dataframe to the table."""
        self._lines.append(str(type(self.data)))

    def add_index_range_line(self) -> None:
        """Add line with range of indices to the table."""
        self._lines.append(self.data.index._summary())

    def add_dtypes_line(self) -> None:
        """Add summary line with dtypes present in dataframe."""
        collected_dtypes = [
            f"{key}({val:d})" for key, val in sorted(self.dtype_counts.items())
        ]
        self._lines.append(f"dtypes: {', '.join(collected_dtypes)}")


class DataFrameTableBuilder(TableBuilderAbstract):
    """
    Abstract builder for dataframe info table.

    Parameters
    ----------
    info : DataFrameInfo.
        Instance of DataFrameInfo.
    """

    def __init__(self, *, info: DataFrameInfo):
        self.info: DataFrameInfo = info

    def get_lines(self) -> List[str]:
        self._lines = []
        if self.col_count == 0:
            self._fill_empty_info()
        else:
            self._fill_non_empty_info()
        return self._lines

    def _fill_empty_info(self) -> None:
        """Add lines to the info table, pertaining to empty dataframe."""
        self.add_object_type_line()
        self.add_index_range_line()
        self._lines.append(f"Empty {type(self.data).__name__}")

    @abstractmethod
    def _fill_non_empty_info(self) -> None:
        """Add lines to the info table, pertaining to non-empty dataframe."""

    @property
    def data(self) -> "DataFrame":
        """DataFrame."""
        return self.info.data

    @property
    def ids(self) -> Index:
        """Dataframe columns."""
        return self.info.ids

    @property
    def col_count(self) -> int:
        """Number of dataframe columns to be summarized."""
        return self.info.col_count

    def add_memory_usage_line(self) -> None:
        """Add line containing memory usage."""
        self._lines.append(f"memory usage: {self.memory_usage_string}")


class DataFrameTableBuilderNonVerbose(DataFrameTableBuilder):
    """
    Dataframe info table builder for non-verbose output.
    """

    def _fill_non_empty_info(self) -> None:
        """Add lines to the info table, pertaining to non-empty dataframe."""
        self.add_object_type_line()
        self.add_index_range_line()
        self.add_columns_summary_line()
        self.add_dtypes_line()
        if self.display_memory_usage:
            self.add_memory_usage_line()

    def add_columns_summary_line(self) -> None:
        self._lines.append(self.ids._summary(name="Columns"))


class TableBuilderVerboseMixin(TableBuilderAbstract):
    """
    Mixin for verbose info output.
    """

    SPACING: str = " " * 2
    strrows: Sequence[Sequence[str]]
    gross_column_widths: Sequence[int]
    with_counts: bool

    @property
    @abstractmethod
    def headers(self) -> Sequence[str]:
        """Headers names of the columns in verbose table."""

    @property
    def header_column_widths(self) -> Sequence[int]:
        """Widths of header columns (only titles)."""
        return [len(col) for col in self.headers]

    def _get_gross_column_widths(self) -> Sequence[int]:
        """Get widths of columns containing both headers and actual content."""
        body_column_widths = self._get_body_column_widths()
        return [
            max(*widths)
            for widths in zip(self.header_column_widths, body_column_widths)
        ]

    def _get_body_column_widths(self) -> Sequence[int]:
        """Get widths of table content columns."""
        strcols: Sequence[Sequence[str]] = list(zip(*self.strrows))
        return [max(len(x) for x in col) for col in strcols]

    def _gen_rows(self) -> Iterator[Sequence[str]]:
        """
        Generator function yielding rows content.

        Each element represents a row comprising a sequence of strings.
        """
        if self.with_counts:
            return self._gen_rows_with_counts()
        else:
            return self._gen_rows_without_counts()

    @abstractmethod
    def _gen_rows_with_counts(self) -> Iterator[Sequence[str]]:
        """Iterator with string representation of body data with counts."""

    @abstractmethod
    def _gen_rows_without_counts(self) -> Iterator[Sequence[str]]:
        """Iterator with string representation of body data without counts."""

    def add_header_line(self) -> None:
        header_line = self.SPACING.join(
            [
                _put_str(header, col_width)
                for header, col_width in zip(self.headers, self.gross_column_widths)
            ]
        )
        self._lines.append(header_line)

    def add_separator_line(self) -> None:
        separator_line = self.SPACING.join(
            [
                _put_str("-" * header_colwidth, gross_colwidth)
                for header_colwidth, gross_colwidth in zip(
                    self.header_column_widths, self.gross_column_widths
                )
            ]
        )
        self._lines.append(separator_line)

    def add_body_lines(self) -> None:
        for row in self.strrows:
            body_line = self.SPACING.join(
                [
                    _put_str(col, gross_colwidth)
                    for col, gross_colwidth in zip(row, self.gross_column_widths)
                ]
            )
            self._lines.append(body_line)

    def _gen_non_null_counts(self) -> Iterator[str]:
        """Iterator with string representation of non-null counts."""
        for count in self.non_null_counts:
            yield f"{count} non-null"

    def _gen_dtypes(self) -> Iterator[str]:
        """Iterator with string representation of column dtypes."""
        for dtype in self.dtypes:
            yield pprint_thing(dtype)


class DataFrameTableBuilderVerbose(DataFrameTableBuilder, TableBuilderVerboseMixin):
    """
    Dataframe info table builder for verbose output.
    """

    def __init__(
        self,
        *,
        info: DataFrameInfo,
        with_counts: bool,
    ):
        self.info = info
        self.with_counts = with_counts
        self.strrows: Sequence[Sequence[str]] = list(self._gen_rows())
        self.gross_column_widths: Sequence[int] = self._get_gross_column_widths()

    def _fill_non_empty_info(self) -> None:
        """Add lines to the info table, pertaining to non-empty dataframe."""
        self.add_object_type_line()
        self.add_index_range_line()
        self.add_columns_summary_line()
        self.add_header_line()
        self.add_separator_line()
        self.add_body_lines()
        self.add_dtypes_line()
        if self.display_memory_usage:
            self.add_memory_usage_line()

    @property
    def headers(self) -> Sequence[str]:
        """Headers names of the columns in verbose table."""
        if self.with_counts:
            return [" # ", "Column", "Non-Null Count", "Dtype"]
        return [" # ", "Column", "Dtype"]

    def add_columns_summary_line(self) -> None:
        self._lines.append(f"Data columns (total {self.col_count} columns):")

    def _gen_rows_without_counts(self) -> Iterator[Sequence[str]]:
        """Iterator with string representation of body data without counts."""
        yield from zip(
            self._gen_line_numbers(),
            self._gen_columns(),
            self._gen_dtypes(),
        )

    def _gen_rows_with_counts(self) -> Iterator[Sequence[str]]:
        """Iterator with string representation of body data with counts."""
        yield from zip(
            self._gen_line_numbers(),
            self._gen_columns(),
            self._gen_non_null_counts(),
            self._gen_dtypes(),
        )

    def _gen_line_numbers(self) -> Iterator[str]:
        """Iterator with string representation of column numbers."""
        for i, _ in enumerate(self.ids):
            yield f" {i}"

    def _gen_columns(self) -> Iterator[str]:
        """Iterator with string representation of column names."""
        for col in self.ids:
            yield pprint_thing(col)


def _get_dataframe_dtype_counts(df: "DataFrame") -> Mapping[str, int]:
    """
    Create mapping between datatypes and their number of occurences.
    """
    # groupby dtype.name to collect e.g. Categorical columns
    return df.dtypes.value_counts().groupby(lambda x: x.name).sum()