"""Paste input → a single-conversation ParsedExport (source="paste").

Mirrors the backend `prompt_card.adapters.paste` (the reuse target) and adds markdown variants. Accepts:
  - role markers at line start: User:/You:/Human:/Me:/Prompt:/Q:  and  Assistant:/AI:/ChatGPT:/Claude:/GPT:/Bot:/Gemini:/Answer:/Response:/A:
  - separators `:` `>` `-` (en-dash too), e.g. "User -" / "AI >"
  - markdown: **User**:, __Assistant__:, "## Assistant", "> User:", "- User:"
  - plain alternating turns (blank-line-separated blocks) → user/assistant starting with user
Requires >=2 user turns (same substance bar as the export path) so all five axes can show signal.
Single conversation only; we never fetch share URLs (paste text only — legal safety).
"""
from __future__ import annotations

import re

from .parser import Conversation, Turn, ParsedExport, ParseError

_USER_WORDS = {"user", "you", "human", "me", "prompt", "q"}
_ASST_WORDS = {"assistant", "ai", "chatgpt", "chat gpt", "gpt", "claude", "bot", "gemini",
               "model", "answer", "response", "a"}
# line -> (role_word, separator?, rest). Strips leading markdown (#, >, -, *, spaces) and bold/italic.
_LINE = re.compile(r"^[\s>#\-]*[*_]{0,3}\s*([A-Za-z][A-Za-z ]{0,11})\s*[*_]{0,3}\s*([:>–-])?\s*(.*)$")


def _marker(line: str):
    """Return (role, rest_text) if the line opens a turn, else None."""
    stripped_lead = re.sub(r"^[\s>#\-]+", "", line)
    had_md = (stripped_lead != line.lstrip()) or "*" in line[:3] or "_" in line[:3]
    m = _LINE.match(line)
    if not m:
        return None
    word, sep, rest = m.group(1).strip().lower(), m.group(2), m.group(3)
    if not (sep or had_md):           # a bare word with no separator/markdown is prose, not a marker
        return None
    if word in _USER_WORDS:
        return "user", rest
    if word in _ASST_WORDS:
        return "assistant", rest
    return None


def _validate(turns: list[Turn]) -> list[Conversation]:
    user_n = sum(1 for t in turns if t.role == "user")
    if user_n < 2:
        raise ParseError("Paste a conversation with at least 2 of YOUR messages "
                         "(use 'User:' / 'Assistant:' markers, or blank lines between turns).")
    return [Conversation(turns=turns)]


def parse_paste(text: str) -> ParsedExport:
    if not isinstance(text, str) or not text.strip():
        raise ParseError("Nothing to analyze — paste a conversation first.")

    marked, role, buf = [], None, []

    def flush():
        if role and buf:
            t = "\n".join(buf).strip()
            if t:
                marked.append(Turn(role=role, text=t))

    for ln in text.splitlines():
        hit = _marker(ln)
        if hit:
            flush()
            role, buf = hit[0], ([hit[1]] if hit[1] else [])
        elif role is not None:
            buf.append(ln)
    flush()

    if marked:
        return ParsedExport(source="paste", conversations=_validate(marked))

    # no markers: blank-line blocks, alternating user/assistant starting with the user
    blocks = [b.strip() for b in re.split(r"\n\s*\n", text) if b.strip()]
    if len(blocks) < 2:
        blocks = [ln.strip() for ln in text.splitlines() if ln.strip()]
    roles = ("user", "assistant")
    turns = [Turn(role=roles[i % 2], text=b) for i, b in enumerate(blocks)]
    return ParsedExport(source="paste", conversations=_validate(turns))