from __future__ import annotations

import re
from dataclasses import dataclass
from enum import IntEnum
from io import BytesIO
from typing import TYPE_CHECKING, Any, cast

from .._codecs import fill_from_encoding
from .._codecs.core_font_metrics import CORE_FONT_METRICS
from .._font import Font
from .._utils import logger_warning
from ..constants import AnnotationDictionaryAttributes, BorderStyles, FieldDictionaryAttributes, PageAttributes
from ..errors import PdfReadError
from ..generic import (
    DecodedStreamObject,
    DictionaryObject,
    IndirectObject,
    NameObject,
    NumberObject,
    RectangleObject,
)
from ..generic._base import ByteStringObject, TextStringObject

if TYPE_CHECKING:
    from pypdf._writer import PdfWriter

    from .._page import PageObject

DEFAULT_FONT_SIZE_IN_MULTILINE = 12


@dataclass
class BaseStreamConfig:
    """A container representing the basic layout of an appearance stream."""
    rectangle: RectangleObject | tuple[float, float, float, float] = (0.0, 0.0, 0.0, 0.0)
    border_width: int = 1  # The width of the border in points
    border_style: str = BorderStyles.SOLID


class BaseStreamAppearance(DecodedStreamObject):
    """A class representing the very base of an appearance stream, that is, a rectangle and a border."""

    def __init__(self, layout: BaseStreamConfig | None) -> None:
        """
        Takes the appearance stream layout as an argument.

        Args:
            layout: The basic layout parameters.
        """
        super().__init__()
        self._layout = layout or BaseStreamConfig()
        self[NameObject("/Type")] = NameObject("/XObject")
        self[NameObject("/Subtype")] = NameObject("/Form")
        self[NameObject("/BBox")] = RectangleObject(self._layout.rectangle)


class TextAlignment(IntEnum):
    """Defines the alignment options for text within a form field's appearance stream."""

    LEFT = 0
    CENTER = 1
    RIGHT = 2


class TextStreamAppearance(BaseStreamAppearance):
    """
    A class representing the appearance stream for a text-based form field.

    This class generates the content stream (the `ap_stream_data`) that dictates
    how text is rendered within a form field's bounding box. It handles properties
    like font, font size, color, multiline text, and text selection highlighting.
    """

    def _scale_text(
        self,
        font: Font,
        font_size: float,
        leading_factor: float,
        field_width: float,
        field_height: float,
        text: str,
        min_font_size: float,
        font_size_step: float = 0.2
    ) -> tuple[list[tuple[float, str]], float]:
        """
        Takes a piece of text and scales it to field_width or field_height, given font_name
        and font_size. Wraps text where necessary.

        Args:
            font: The font to be used.
            font_size: The font size in points.
            leading_factor: The line distance.
            field_width: The width of the field in which to fit the text.
            field_height: The height of the field in which to fit the text.
            text: The text to fit with the field.
            min_font_size: The minimum font size at which to scale the text.
            font_size_step: The amount by which to decrement font size per step while scaling.

        Returns:
            The text in the form of list of tuples, each tuple containing the length of a line
            and its contents, and the font_size for these lines and lengths.
        """
        orig_text = text
        paragraphs = text.replace("\n", "\r").split("\r")
        wrapped_lines = []
        current_line_words: list[str] = []
        current_line_width: float = 0
        space_width = font.space_width * font_size / 1000
        for paragraph in paragraphs:
            if not paragraph.strip():
                wrapped_lines.append((0.0, ""))
                continue
            words = paragraph.split(" ")
            for i, word in enumerate(words):
                word_width = font.text_width(word) * font_size / 1000
                test_width = current_line_width + word_width + (space_width if i else 0)
                if test_width > field_width and current_line_words:
                    wrapped_lines.append((current_line_width, " ".join(current_line_words)))
                    current_line_words = [word]
                    current_line_width = word_width
                elif not current_line_words and word_width > field_width:
                    wrapped_lines.append((word_width, word))
                    current_line_words = []
                    current_line_width = 0
                else:
                    if current_line_words:
                        current_line_width += space_width
                    current_line_words.append(word)
                    current_line_width += word_width
            if current_line_words:
                wrapped_lines.append((current_line_width, " ".join(current_line_words)))
                current_line_words = []
                current_line_width = 0
        # Estimate total height.
        estimated_total_height = font_size + (len(wrapped_lines) - 1) * leading_factor * font_size
        if estimated_total_height > field_height:
            # Text overflows height; Retry with smaller font size.
            new_font_size = font_size - font_size_step
            if new_font_size >= min_font_size:
                return self._scale_text(
                    font,
                    new_font_size,
                    leading_factor,
                    field_width,
                    field_height,
                    orig_text,
                    min_font_size,
                    font_size_step
                )
        return wrapped_lines, round(font_size, 1)

    def _generate_appearance_stream_data(
        self,
        text: str,
        selection: list[str] | None ,
        font: Font,
        font_glyph_byte_map: dict[str, bytes] | None = None,
        font_name: str = "/Helv",
        font_size: float = 0.0,
        font_color: str = "0 g",
        is_multiline: bool = False,
        alignment: TextAlignment = TextAlignment.LEFT,
        is_comb: bool = False,
        max_length: int | None = None
    ) -> bytes:
        """
        Generates the raw bytes of the PDF appearance stream for a text field.

        This private method assembles the PDF content stream operators to draw
        the provided text within the specified rectangle. It handles text positioning,
        font application, color, and special formatting like selected text.

        Args:
            text: The text to be rendered in the form field.
            selection: An optional list of strings that should be highlighted as selected.
            font: The font to use.
            font_glyph_byte_map: An optional dictionary mapping characters to their
                byte representation for glyph encoding.
            font_name: The name of the font resource to use (e.g., "/Helv").
            font_size: The font size. If 0, it is automatically calculated
                based on whether the field is multiline or not.
            font_color: The color to apply to the font, represented as a PDF
                graphics state string (e.g., "0 g" for black).
            is_multiline: A boolean indicating if the text field is multiline.
            alignment: Text alignment, can be TextAlignment.LEFT, .RIGHT, or .CENTER.
            is_comb: Boolean that designates fixed-length fields, where every character
                fills one "cell", such as in a postcode.
            max_length: Used if is_comb is set. The maximum number of characters for a fixed-
                length field.

        Returns:
            A byte string containing the PDF content stream data.

        """
        rectangle = self._layout.rectangle
        font_glyph_byte_map = font_glyph_byte_map or {}
        if isinstance(rectangle, tuple):
            rectangle = RectangleObject(rectangle)
        leading_factor = (font.font_descriptor.bbox[3] - font.font_descriptor.bbox[1]) / 1000.0

        # Set margins based on border width and style, but never less than 1 point
        factor = 2 if self._layout.border_style in {"/B", "/I"} else 1
        margin = max(self._layout.border_width * factor, 1)
        field_height = rectangle.height - 2 * margin
        field_width = rectangle.width - 4 * margin

        # If font_size is 0, apply the logic for multiline or large-as-possible font
        if font_size == 0:
            min_font_size = 4.0       # The mininum font size
            if selection:             # Don't wrap text when dealing with a /Ch field, in order to prevent problems
                is_multiline = False  # with matching "selection" with "line" later on.
            if is_multiline:
                font_size = DEFAULT_FONT_SIZE_IN_MULTILINE
                lines, font_size = self._scale_text(
                    font,
                    font_size,
                    leading_factor,
                    field_width,
                    field_height,
                    text,
                    min_font_size
                )
            else:
                max_vertical_size = field_height / leading_factor
                text_width_unscaled = font.text_width(text) / 1000
                max_horizontal_size = field_width / (text_width_unscaled or 1)
                font_size = round(max(min(max_vertical_size, max_horizontal_size), min_font_size), 1)
                lines = [(text_width_unscaled * font_size, text)]
        elif is_comb:
            if max_length and len(text) > max_length:
                logger_warning(
                    (
                        "Length of text %(text)s exceeds maximum length (%(max_length)d) "
                        "of field, input truncated."
                    ),
                    source=__name__,
                    text=text,
                    max_length=max_length,
                )
            # We act as if each character is one line, because we draw it separately later on
            lines = [(
                font.text_width(char) * font_size / 1000,
                char
            ) for index, char in enumerate(text) if index < (max_length or len(text))]
        else:
            lines = [(
                font.text_width(line) * font_size / 1000,
                line
            ) for line in text.replace("\n", "\r").split("\r")]

        # Set the vertical offset
        if is_multiline:
            y_offset = rectangle.height + margin - font.font_descriptor.bbox[3] * font_size / 1000.0
        else:
            y_offset = margin + ((field_height - font.font_descriptor.ascent * font_size / 1000) / 2)
        default_appearance = f"{font_name} {font_size} Tf {font_color}"

        ap_stream = (
            f"q\n/Tx BMC \nq\n{2 * margin} {margin} {field_width} {field_height} "
            f"re\nW\nBT\n{default_appearance}\n"
        ).encode()
        current_x_pos: float = 0  # Initial virtual position within the text object.

        for line_number, (line_width, line) in enumerate(lines):
            if selection and line in selection:
                # Might be improved, but cannot find how to get fill working => replaced with lined box
                ap_stream += (
                    f"1 {y_offset - (line_number * font_size * leading_factor) - 1} "
                    f"{rectangle.width - 2} {font_size + 2} re\n"
                    f"0.5 0.5 0.5 rg s\n{default_appearance}\n"
                ).encode()

            # Calculate the desired absolute starting X for the current line
            desired_abs_x_start: float = 0
            if is_comb and max_length:
                # Calculate the width of a cell for one character
                cell_width = rectangle.width / max_length
                # Space from the left edge of the cell to the character's baseline start
                # line_width here is the *actual* character width in points for the single character 'line'
                centering_offset_in_cell = (cell_width - line_width) / 2
                # Absolute start X = (Cell Index, i.e., line_number * Cell Width) + Centering Offset
                desired_abs_x_start = (line_number * cell_width) + centering_offset_in_cell
            elif alignment == TextAlignment.RIGHT:
                desired_abs_x_start = rectangle.width - margin * 2 - line_width
            elif alignment == TextAlignment.CENTER:
                desired_abs_x_start = (rectangle.width - line_width) / 2
            else:  # Left aligned; default
                desired_abs_x_start = margin * 2
            # Calculate x_rel_offset: how much to move from the current_x_pos
            # to reach the desired_abs_x_start.
            x_rel_offset = desired_abs_x_start - current_x_pos

            # Y-offset:
            y_rel_offset: float = 0
            if line_number == 0:
                y_rel_offset = y_offset  # Initial vertical position
            elif is_comb:
                y_rel_offset = 0.0  # DO NOT move vertically for subsequent characters
            else:
                y_rel_offset = - font_size * leading_factor  # Move down by line height

            # Td is a relative translation (Tx and Ty).
            # It updates the current text position.
            ap_stream += f"{x_rel_offset} {y_rel_offset} Td\n".encode()
            # Update current_x_pos based on the Td operation for the next iteration.
            # This is the X position where the *current line* will start.
            current_x_pos = desired_abs_x_start

            encoded_line: list[bytes] = [
                font_glyph_byte_map.get(c, c.encode("utf-16-be")) for c in line
            ]
            if any(len(c) >= 2 for c in encoded_line):
                ap_stream += b"<" + (b"".join(encoded_line)).hex().encode() + b"> Tj\n"
            else:
                ap_stream += b"(" + b"".join(encoded_line) + b") Tj\n"
        ap_stream += b"ET\nQ\nEMC\nQ\n"
        return ap_stream

    def __init__(
        self,
        layout: BaseStreamConfig | None = None,
        text: str = "",
        selection: list[str] | None = None,
        font: Font | None = None,
        font_resource: DictionaryObject | IndirectObject | None = None,
        font_name: str = "/Helv",
        font_size: float = 0.0,
        font_color: str = "0 g",
        is_multiline: bool = False,
        alignment: TextAlignment = TextAlignment.LEFT,
        is_comb: bool = False,
        max_length: int | None = None
    ) -> None:
        """
        Initializes a TextStreamAppearance object.

        This constructor creates a new PDF stream object configured as an XObject
        of subtype Form. It uses the `_appearance_stream_data` method to generate
        the content for the stream.

        Args:
            layout: The basic layout parameters.
            text: The text to be rendered in the form field.
            selection: An optional list of strings that should be highlighted as selected.
            font: A Font object. Falls back to Type 1 Helvetica if not given.
            font_resource: An optional variable that represents a PDF font dictionary. Falls back
                to Type 1 Helvetica if not given.
            font_name: The name of the font resource, e.g., "/Helv".
            font_size: The font size. If 0, it's auto-calculated.
            font_color: The font color string.
            is_multiline: A boolean indicating if the text field is multiline.
            alignment: Text alignment, can be TextAlignment.LEFT, .RIGHT, or .CENTER.
            is_comb: Boolean that designates fixed-length fields, where every character
                fills one "cell", such as in a postcode.
            max_length: Used if is_comb is set. The maximum number of characters for a fixed-
                length field.

        """
        super().__init__(layout)

        if not font or not font_resource:
            font_name = "/Helv"
            core_font_metrics = CORE_FONT_METRICS["Helvetica"]
            font = Font(
                name="Helvetica",
                character_map={},
                encoding=dict(zip(range(256), fill_from_encoding("cp1252"))),  # WinAnsiEncoding
                sub_type="Type1",
                font_descriptor=core_font_metrics.font_descriptor,
                character_widths=core_font_metrics.character_widths
            )
            font_resource = font.as_font_resource()

        font_glyph_byte_map: dict[str, bytes] = {}
        if isinstance(font.encoding, str):
            font.character_map.pop(-1, None)  # Remove -1 key that does not map a character
            for k, v in font.character_map.items():
                font_glyph_byte_map[v] = k.encode(font.encoding)
        else:
            font_glyph_byte_map = {v: bytes((k,)) for k, v in font.encoding.items()}
            font_encoding_rev = {v: bytes((k,)) for k, v in font.encoding.items()}
            for key, value in font.character_map.items():
                font_glyph_byte_map[value] = font_encoding_rev.get(key, key)

        ap_stream_data = self._generate_appearance_stream_data(
            text,
            selection,
            font,
            font_glyph_byte_map,
            font_name=font_name,
            font_size=font_size,
            font_color=font_color,
            is_multiline=is_multiline,
            alignment=alignment,
            is_comb=is_comb,
            max_length=max_length
        )

        self.set_data(ByteStringObject(ap_stream_data))
        self[NameObject("/Length")] = NumberObject(len(ap_stream_data))
        # Update Resources with font information
        self[NameObject("/Resources")] = DictionaryObject({
            NameObject("/Font"): DictionaryObject({
                NameObject(font_name): getattr(font_resource, "indirect_reference", font_resource)
            })
        })

    @staticmethod
    def _find_annotation_font_resource(
            font_name: str,
            annotation: DictionaryObject,
            acro_form: DictionaryObject,
            text: str
        ) -> tuple[str, Font]:
        # Try to find a resource dictionary for the font by examining the annotation and, if that fails,
        # the AcroForm resources dictionary
        acro_form_resources: Any = cast(
            DictionaryObject,
            annotation.get_inherited(
                "/DR",
                acro_form.get("/DR", DictionaryObject()),
            ),
        )
        acro_form_font_resources = acro_form_resources.get("/Font", DictionaryObject())
        font_resource = acro_form_font_resources.get(font_name, None)
        if font_resource:
            font = Font.from_font_resource(font_resource)
        else:
            # Normally, we should have found a font resource by now. However, when a user has provided a specific
            # font name, we may not have found the associated font resource among the AcroForm resources. Also, in
            # case of the 14 Adobe Core fonts, we may be expected to construct a font resource ourselves.
            if font_name.removeprefix("/") not in CORE_FONT_METRICS:
                # Default to Helvetica if we haven't found a font resource and cannot construct one ourselves.
                logger_warning(
                    "Font dictionary for %(font_name)s not found; defaulting to Helvetica.",
                    source=__name__,
                    font_name=font_name,
                )
                font_name = "/Helvetica"
            core_font_metrics = CORE_FONT_METRICS[font_name.removeprefix("/")]
            font = Font(
                name=font_name.removeprefix("/"),
                character_map={},
                encoding=dict(zip(range(256), fill_from_encoding("cp1252"))),  # WinAnsiEncoding
                sub_type="Type1",
                font_descriptor=core_font_metrics.font_descriptor,
                character_widths=core_font_metrics.character_widths
            )

        # If we have found a font resource, it still might not be able to encode the text value we received.
        encodable = font.can_encode(text)

        if not encodable:
            # If we have a font file, we can try to produce a new font resource with an encoding
            # that does include the necessary characters.
            if font.font_descriptor.font_file and font.sub_type == "TrueType":
                try:
                    font = font.from_truetype_font_file(BytesIO(font.font_descriptor.font_file.get_data()))
                    font_name = "/PYPDF1"  # This means we most probably do not clash with an existing font name
                    encodable = font.can_encode(text)
                except (ImportError, PdfReadError) as e:
                    logger_warning("Unable to use embedded font for encoding: %(e)s", source=__name__, e=e)

            if not encodable:
                logger_warning(
                    (
                        "Text string '%(text)s' contains characters not supported by font encoding. "
                        "This may result in text corruption. "
                        "Consider calling writer.update_page_form_field_values with auto_regenerate=True."
                    ),
                    source=__name__,
                    text=text,
                )

        return font_name, font

    @staticmethod
    def _sync_appearance_stream_font_resources(
        writer: PdfWriter,
        font_name: str,
        font: Font,
        target_resource_dict: DictionaryObject,
        page: PageObject | None = None
    ) -> IndirectObject:
        """
        Unified helper to sync fonts from an AP stream to a target resource dictionary (e.g., AcroForm /DR).
        Will sync to page resources as well when page is added to the arguments.
        """
        target_fonts = target_resource_dict.setdefault(NameObject("/Font"), DictionaryObject()).get_object()
        if font_name not in target_fonts:
            font_resource_reference = font._add_to_writer(
                writer,
                target_fonts,
                NameObject(font_name)
            )
        else:
            font_resource_reference = target_fonts[font_name]

        if page:
            page_fonts_resource = cast(DictionaryObject, page[PageAttributes.RESOURCES]).setdefault(
                NameObject("/Font"), DictionaryObject()
            ).get_object()
            if font_name not in page_fonts_resource:
                page_fonts_resource[NameObject(font_name)] = getattr(
                    font_resource_reference, "indirect_reference", font_resource_reference
                )

        return font_resource_reference

    @classmethod
    def from_text_annotation(
        cls,
        writer: PdfWriter,
        page: PageObject,
        flatten: bool,
        acro_form: DictionaryObject,  # _root_object[CatalogDictionary.ACRO_FORM])
        field: DictionaryObject,
        annotation: DictionaryObject,
        user_font_name: str = "",
        user_font_size: float = -1,
    ) -> TextStreamAppearance:
        """
        Creates a TextStreamAppearance object from a text field annotation.

        This class method is a factory for creating a `TextStreamAppearance`
        instance by extracting all necessary information (bounding box, font,
        text content, etc.) from the PDF field and annotation dictionaries.
        It respects inheritance for properties like default appearance (`/DA`).

        Args:
            writer: The PdfWriter instance that we are creating text stream appearances for.
            page: The page that we are processing annotations for.
            flatten: Whether we flatten text annotations or not. If true, add new font resource
                to the page font resources. Otherwise, add them to the AcroForm resources.
            acro_form: The root AcroForm dictionary from the PDF catalog.
            field: The field dictionary object.
            annotation: The widget annotation dictionary object associated with the field.
            user_font_name: An optional user-provided font name to override the
                default. Defaults to an empty string.
            user_font_size: An optional user-provided font size to override the
                default. A value of -1 indicates no override.

        Returns:
            A new `TextStreamAppearance` instance configured for the given field.

        """
        # Calculate rectangle dimensions
        _rectangle = cast(RectangleObject, annotation[AnnotationDictionaryAttributes.Rect])
        rectangle = RectangleObject((0, 0, abs(_rectangle[2] - _rectangle[0]), abs(_rectangle[3] - _rectangle[1])))

        # Get default appearance dictionary from annotation
        default_appearance = annotation.get_inherited(
            AnnotationDictionaryAttributes.DA,
            acro_form.get(AnnotationDictionaryAttributes.DA, None),
        )
        if not default_appearance:
            # Create a default appearance if none was found in the annotation
            default_appearance = TextStringObject("/Helv 0 Tf 0 g")
        else:
            default_appearance = default_appearance.get_object()

        # Retrieve field text and selected values
        field_flags = field.get(FieldDictionaryAttributes.Ff, 0)
        if (
                field.get(FieldDictionaryAttributes.FT, "/Tx") == "/Ch" and
                field_flags & FieldDictionaryAttributes.FfBits.Combo == 0
        ):
            text = "\n".join(annotation.get_inherited(FieldDictionaryAttributes.Opt, []))
            selection = field.get("/V", [])
            if not isinstance(selection, list):
                selection = [selection]
        else:  # /Tx
            text = field.get("/V", "")
            selection = []

        # Escape parentheses (PDF 1.7 reference, table 3.2, Literal Strings)
        text = text.replace("\\", "\\\\").replace("(", r"\(").replace(")", r"\)")

        # Derive font name, size and color from the default appearance. Also set
        # user-provided font name and font size in the default appearance, if given.
        # For a font name, this presumes that we can find an associated font resource
        # dictionary. Uses the variable font_properties as an intermediate.
        # As per the PDF spec:
        # "At a minimum, the string [that is, default_appearance] shall include a Tf (text
        # font) operator along with its two operands, font and size" (Section 12.7.4.3
        # "Variable text" of the PDF 2.0 specification).
        font_properties = [prop for prop in re.split(r"\s", default_appearance) if prop]
        da_font_name = font_properties.pop(font_properties.index("Tf") - 2)
        font_size = float(font_properties.pop(font_properties.index("Tf") - 1))
        font_properties.remove("Tf")
        font_color = " ".join(font_properties)
        # Determine the font name to use, prioritizing the user's input
        if user_font_name:
            font_name = user_font_name
        else:
            font_name = da_font_name
        # Determine the font size to use, prioritizing the user's input
        if user_font_size > 0:
            font_size = user_font_size

        font_name, font = cls._find_annotation_font_resource(font_name, annotation, acro_form, text)

        # Change the /DA information if we changed the font name
        if font_name != da_font_name:
            annotation[NameObject("/DA")] = TextStringObject(default_appearance.replace(da_font_name, font_name))

        # Synchronise font resources
        font_resource_reference = cls._sync_appearance_stream_font_resources(
            writer,
            font_name,
            font,
            acro_form.setdefault(NameObject("/DR"), DictionaryObject()),
            page if flatten else None,
        )

        # Retrieve formatting information
        is_comb = False
        max_length = None
        if field_flags & FieldDictionaryAttributes.FfBits.Comb:
            is_comb = True
            max_length = annotation.get("/MaxLen")
        is_multiline = False
        if field_flags & FieldDictionaryAttributes.FfBits.Multiline:
            is_multiline = True
        alignment = field.get("/Q", TextAlignment.LEFT)
        border_width = 1
        border_style = BorderStyles.SOLID
        if "/BS" in field:
            border_width = cast(DictionaryObject, field["/BS"]).get("/W", border_width)
            border_style = cast(DictionaryObject, field["/BS"]).get("/S", border_style)

        # Create the TextStreamAppearance instance
        layout = BaseStreamConfig(rectangle=rectangle, border_width=border_width, border_style=border_style)
        new_appearance_stream = cls(
            layout,
            text,
            selection,
            font,
            font_resource_reference,
            font_name=font_name,
            font_size=font_size,
            font_color=font_color,
            is_multiline=is_multiline,
            alignment=alignment,
            is_comb=is_comb,
            max_length=max_length
        )

        if AnnotationDictionaryAttributes.AP in annotation:
            for key, value in (
                cast(DictionaryObject, annotation[AnnotationDictionaryAttributes.AP]).get("/N", {}).items()
            ):
                if key in {"/BBox", "/Length", "/Subtype", "/Type", "/Filter"}:
                    continue
                # Don't overwrite font resources added by TextAppearanceStream.__init__
                if key == "/Resources":
                    if "/Font" not in value:
                        value.get_object()[NameObject("/Font")] = DictionaryObject()
                    value["/Font"].get_object()[NameObject(font_name)] = getattr(
                        font_resource_reference, "indirect_reference", font_resource_reference
                    )
                else:
                    new_appearance_stream[key] = value

        return new_appearance_stream
