import re

from yuxi.channel.extensions.slack.constants import (
    SLACK_AGENT_PROMPT_RULES,
    SLACK_MENTION_PATTERN,
    SLACK_TEXT_LIMIT,
)

_LINK_PATTERN = re.compile(r"\[([^\]]*)\]\(([^)]*)\)")
_BOLD_PATTERN = re.compile(r"\*\*(.+?)\*\*")
_ITALIC_PATTERN = re.compile(r"(?<!\*)\*(?!\*)(.+?)(?<!\*)\*(?!\*)")
_STRIKETHROUGH_PATTERN = re.compile(r"~~(.+?)~~")
_HEADING_PATTERN = re.compile(r"^#{1,6}\s+(.+)$", re.MULTILINE)

_FORMAT_TOKEN_PATTERN = re.compile(
    r"""
    \*[^*]+\*        |
    _[^_]+_          |
    ~[^~]+~          |
    `[^`]+`          |
    <[^>]+>
    """,
    re.VERBOSE,
)


def _find_safe_split_position(text: str, pos: int) -> int:
    for match in _FORMAT_TOKEN_PATTERN.finditer(text):
        start, end = match.start(), match.end()
        if start < pos < end:
            before_len = pos - start
            after_len = end - pos
            return start if before_len <= after_len else end
    return pos


def markdown_to_slack(text: str) -> str:
    text = _LINK_PATTERN.sub(r"<\2|\1>", text)
    text = _BOLD_PATTERN.sub(r"*\1*", text)
    text = _ITALIC_PATTERN.sub(r"_\1_", text)
    text = _STRIKETHROUGH_PATTERN.sub(r"~\1~", text)
    text = _HEADING_PATTERN.sub(r"*\1*", text)
    lines = text.split("\n")
    result: list[str] = []
    table_buffer: list[str] = []
    in_table = False

    for line in lines:
        stripped = line.strip()
        if stripped.startswith("|") and stripped.endswith("|"):
            if not in_table:
                in_table = True
                table_buffer = []
            table_buffer.append(stripped)
            continue
        else:
            if in_table:
                in_table = False
                result.extend(_convert_table_rows(table_buffer))
                table_buffer = []
            result.append(line)

    if in_table and table_buffer:
        result.extend(_convert_table_rows(table_buffer))

    return "\n".join(result)


def _convert_table_rows(rows: list[str]) -> list[str]:
    if len(rows) < 2:
        return rows

    def _parse_cells(row: str) -> list[str]:
        return [cell.strip() for cell in row.strip("|").split("|")]

    header = _parse_cells(rows[0])
    separator = _parse_cells(rows[1])
    body_rows = rows[2:]
    is_sep = all(re.fullmatch(r"[-:]{3,}", cell) or re.fullmatch(r":[-:]+:", cell) for cell in separator)

    if not is_sep:
        all_rows = [_parse_cells(r) for r in rows]
    else:
        all_rows = [_parse_cells(r) for r in body_rows]

    if not header:
        return [", ".join(cells) for cells in all_rows]

    bullet_lines: list[str] = []
    for cells in all_rows:
        pairs = [f"{header[i]}: {cells[i]}" if i < len(cells) else f"{header[i]}: " for i in range(len(header))]
        bullet_lines.append("• " + ", ".join(pairs))

    return bullet_lines


def chunk_text(text: str, limit: int = SLACK_TEXT_LIMIT) -> list[str]:
    if not text:
        return []

    if len(text) <= limit:
        return [text]

    chunks: list[str] = []
    paragraphs = text.split("\n\n")

    for para in paragraphs:
        if not para:
            continue
        if len(para) <= limit:
            chunks.append(para)
        else:
            chunks.extend(_chunk_single_paragraph(para, limit))

    merged: list[str] = []
    for chunk in chunks:
        if not merged:
            merged.append(chunk)
            continue
        last = merged[-1]
        candidate = last + "\n\n" + chunk
        if len(candidate) <= limit:
            merged[-1] = candidate
        else:
            merged.append(chunk)

    return merged


def _chunk_single_paragraph(text: str, limit: int) -> list[str]:
    sentences = re.split(r"(?<=[.?!])\s+", text)
    chunks: list[str] = []
    current = ""

    for sentence in sentences:
        if not sentence:
            continue
        if len(sentence) > limit:
            if current:
                chunks.append(current.rstrip())
                current = ""
            chunks.extend(_chunk_by_words(sentence, limit))
        else:
            candidate = (current + " " + sentence).strip() if current else sentence
            if len(candidate) <= limit:
                current = candidate
            else:
                chunks.append(current.rstrip())
                current = sentence

    if current:
        chunks.append(current.rstrip())

    return chunks


def _chunk_by_words(text: str, limit: int) -> list[str]:
    words = text.split(" ")
    chunks: list[str] = []
    current = ""

    for word in words:
        if not word:
            continue
        if not current:
            current = word
            continue
        candidate = current + " " + word
        if len(candidate) <= limit:
            current = candidate
        else:
            chunks.append(current)
            current = word

    if current:
        chunks.append(current)

    safe_chunks: list[str] = []
    for chunk in chunks:
        if len(chunk) <= limit:
            safe_chunks.append(chunk)
        else:
            split_pos = _find_safe_split_position(chunk, limit)
            if split_pos == 0 or split_pos == limit:
                safe_chunks.append(chunk)
            else:
                safe_chunks.append(chunk[:split_pos])
                safe_chunks.append(chunk[split_pos:])

    return safe_chunks


def strip_mentions(text: str) -> str:
    return re.sub(SLACK_MENTION_PATTERN, "", text).strip()


def extract_mentions(text: str) -> list[str]:
    return re.findall(SLACK_MENTION_PATTERN, text)


def get_agent_prompt_rules() -> list[str]:
    return SLACK_AGENT_PROMPT_RULES