import re
from dataclasses import dataclass, field
from typing import List, Tuple

import urwid

_DEFAULT_FG_COLOR = "default"  # Urwid's default color string for foreground
_DEFAULT_BG_COLOR = "default"  # Urwid's default color string for background


@dataclass
class _AnsiState:
    """Manages the current state of ANSI SGR attributes."""

    """Initialize the ANSI state with default attributes."""
    fg: str = _DEFAULT_FG_COLOR
    bg: str = _DEFAULT_BG_COLOR
    styles: set[str] = field(default_factory=set)

    def reset(self):
        """Reset all attributes to default."""
        self.fg = _DEFAULT_FG_COLOR
        self.bg = _DEFAULT_BG_COLOR
        self.styles.clear()

    def get_attr_spec(self) -> urwid.AttrSpec:
        """Create an Urwid AttrSpec from the current state."""
        current_fg_color = self.fg
        current_bg_color = self.bg

        # Styles that Urwid's AttrSpec parses from the foreground string
        urwid_supported_styles = {
            "bold",
            "underline",
            "standout",
            "italics",
            "blink",
            "strikethrough",
        }

        active_style_parts = [
            s for s in self.styles if s in urwid_supported_styles
        ]

        # Handle 'reverse' by swapping fg and bg colors
        if "reverse" in self.styles:
            current_fg_color, current_bg_color = (
                current_bg_color,
                current_fg_color,
            )

        # Handle 'conceal' by making fg the same as bg
        if "conceal" in self.styles:
            current_fg_color = current_bg_color

        # Construct the foreground specification string
        fg_spec_parts = []
        if active_style_parts:
            fg_spec_parts.extend(sorted(active_style_parts))

        if current_fg_color != _DEFAULT_FG_COLOR or not fg_spec_parts:
            fg_spec_parts.append(current_fg_color)

        final_fg_spec = ",".join(fg_spec_parts)
        if not final_fg_spec:
            final_fg_spec = _DEFAULT_FG_COLOR

        final_bg_spec = current_bg_color

        return urwid.AttrSpec(final_fg_spec, final_bg_spec)


_ANSI_CONTROL_SEQUENCES = re.compile(
    r"[\x00-\x08\x0B\x0C\x0E-\x1A\x1C-\x1F]"  # C0 control characters
    r"[\x80-\x9F]"  # C1 control characters
    r"\x1bP[^\x1b]*\x1b\\"  # DCS (Device Control String)
    r"\x1b_[^\x1b]*\x1b\\"  # APC (Application Program Command)
    r"\x1b\^[^\x1b]*\x1b\\"  # PM (Privacy Message)
)
_OSC_CONTROL_SEQUENCES = re.compile(
    r"\x1b\][^\x07\x1b]*(\x07|\x1b\\)", re.DOTALL
)
_CSI_CONTROL_SEQUENCES = re.compile(r"(\x1b\[[0-9;?]*)([A-Za-z])")


def _strip_ansi_control_sequences(text: str) -> str:
    """
    Strips non-SGR ANSI escape sequences and other problematic control characters.
    Tabs are NOT handled here; they are expanded later on plain text segments.
    Importantly, \x1b (ESC) is NOT stripped by this function if it's part of an SGR.
    """
    text = _ANSI_CONTROL_SEQUENCES.sub("", text)
    text = _OSC_CONTROL_SEQUENCES.sub("", text)

    # Strip CSI (Control Sequence Introducer) sequences that are NOT SGR (ending in 'm')
    def csi_stripper(match: re.Match) -> str:
        if match.group(2) != "m":
            return ""
        return match.group(0)

    text = _CSI_CONTROL_SEQUENCES.sub(csi_stripper, text)

    if "\r" in text:
        if not text.endswith("\r") and not text.endswith("\r\n"):
            text = text.split("\r")[-1]

    return text


def _expand_tabs_with_col_tracking(
    text: str, starting_col: int, tab_width: int = 8  # default tab width
) -> tuple[str, int]:
    """Expands tabs in a string to spaces, tracking column position."""
    expanded_text = []
    current_col = starting_col
    for char in text:
        if char == "\t":
            spaces_to_add = tab_width - (current_col % tab_width)
            expanded_text.append(" " * spaces_to_add)
            current_col += spaces_to_add
        else:
            expanded_text.append(char)
            current_col += 1
    return "".join(expanded_text), current_col


def _handle_extended_color(
    params: list[str], idx: int, state: _AnsiState, is_fg: bool
) -> int:
    """Handle extended color codes (38;5;n or 38;2;r;g;b for fg, 48 for bg)."""
    if idx >= len(params):
        return idx
    color_mode = params[idx]
    idx += 1
    if color_mode == "5":
        if idx < len(params):
            color_id = params[idx]
            try:
                int(color_id)
                color_val = f"h{color_id}"
                if is_fg:
                    state.fg = color_val
                else:
                    state.bg = color_val
            except ValueError:
                pass
            idx += 1
    elif color_mode == "2":
        if idx + 2 < len(params):
            try:
                r, g, b = params[idx : idx + 3]
                color_val = f"#{int(r):02x}{int(g):02x}{int(b):02x}"
                if is_fg:
                    state.fg = color_val
                else:
                    state.bg = color_val
            except ValueError:
                pass
            idx += 3
        else:
            # Malformed sequence, consume rest of params to avoid misinterpretation.
            return len(params)
    return idx


_ANSI_SGR_PATTERN = re.compile(r"\x1b\[([\d;]*)m")
_ANSI_FG_COLOR_MAP = {
    "30": "black",
    "31": "dark red",
    "32": "dark green",
    "33": "brown",
    "34": "dark blue",
    "35": "dark magenta",
    "36": "dark cyan",
    "37": "light gray",
    "90": "dark gray",
    "91": "light red",
    "92": "light green",
    "93": "yellow",
    "94": "light blue",
    "95": "light magenta",
    "96": "light cyan",
    "97": "white",
}
_ANSI_BG_COLOR_MAP = {
    "40": "black",
    "41": "dark red",
    "42": "dark green",
    "43": "brown",
    "44": "dark blue",
    "45": "dark magenta",
    "46": "dark cyan",
    "47": "light gray",
    "100": "dark gray",
    "101": "light red",
    "102": "light green",
    "103": "yellow",
    "104": "light blue",
    "105": "light magenta",
    "106": "light cyan",
    "107": "white",
}


def ansi_to_urwid_markup(line: str) -> List[Tuple[urwid.AttrSpec, str] | str]:
    """
    Convert a string containing ANSI SGR codes to Urwid markup list.
    Non-SGR control codes are stripped, and tabs are expanded.
    """
    cleaned_line = _strip_ansi_control_sequences(line)

    markup: List[Tuple[urwid.AttrSpec, str] | str] = []
    last_pos = 0
    current_col = 0
    state = _AnsiState()

    for match in _ANSI_SGR_PATTERN.finditer(cleaned_line):
        start, end = match.span()

        if start > last_pos:
            text_segment = cleaned_line[last_pos:start]
            expanded_segment, new_col = _expand_tabs_with_col_tracking(
                text_segment, current_col
            )
            current_col = new_col
            if expanded_segment:
                markup.append((state.get_attr_spec(), expanded_segment))

        last_pos = end

        codes_str = match.group(1)
        if not codes_str or codes_str == "0":
            state.reset()
        else:
            params = codes_str.split(";")
            idx = 0
            while idx < len(params):
                code = params[idx]
                if not code:
                    idx += 1
                    continue
                # turn off black formatting to make code more readable
                # fmt: off
                match code:
                    # add, update, or remove styles based on ANSI codes 
                    case "1": state.styles.add("bold")
                    case "2": state.styles.add("faint")
                    case "3": state.styles.add("italics")
                    case "4": state.styles.add("underline")
                    case "5" | "6": state.styles.add("blink")
                    case "7": state.styles.update({"reverse", "standout"})
                    case "8": state.styles.add("conceal")
                    case "9": state.styles.add("strikethrough")
                    case "21": state.styles.add("underline")
                    case "22": state.styles.difference_update({"bold", "faint"})
                    case "23": state.styles.discard("italics")
                    case "24": state.styles.discard("underline")
                    case "25": state.styles.discard("blink")
                    case "27": state.styles.difference_update({"reverse", "standout"})
                    case "28": state.styles.discard("conceal")
                    case "29": state.styles.discard("strikethrough")
                    # foreground and background color codes
                    case code if code in _ANSI_FG_COLOR_MAP:
                        state.fg = _ANSI_FG_COLOR_MAP[code]
                    case "39":
                        state.fg = _DEFAULT_FG_COLOR
                    case code if code in _ANSI_BG_COLOR_MAP:
                        state.bg = _ANSI_BG_COLOR_MAP[code]
                    case "49":
                        state.bg = _DEFAULT_BG_COLOR
                    # extended color codes
                    case "38":
                        idx = _handle_extended_color(
                            params, idx + 1, state, True
                        )
                        continue
                    case "48":
                        idx = _handle_extended_color(
                            params, idx + 1, state, False
                        )
                        continue
                    # do nothing for unsupported or unrecognized codes
                    case _:
                        pass
                # fmt: on
                # turn on black formatting
                idx += 1

    if last_pos < len(cleaned_line):
        text_segment = cleaned_line[last_pos:]
        expanded_segment, _ = _expand_tabs_with_col_tracking(
            text_segment, current_col
        )
        if expanded_segment:
            markup.append((state.get_attr_spec(), expanded_segment))

    return [
        part
        for part in markup
        if isinstance(part, str) or (isinstance(part, tuple) and part[1])
    ]
