#!/usr/bin/env python
from __future__ import annotations

import re
import unicodedata

_SINGLE_LETTER_RE = re.compile(r"^[A-Za-z]$")
_OPTION_LINE_RE = re.compile(r"(?im)(?:^|[\n\r])\s*([A-Z])\s*[\)\.\:：、]")
_OPTION_LIST_RE = re.compile(
    r"\b[A-Z]\b(?:\s*(?:,|，|/|、|&|\band\b|\bor\b)\s*\b[A-Z]\b)+",
    flags=re.IGNORECASE,
)
_OPTION_RANGE_RE = re.compile(r"\b([A-Z])\s*-\s*([A-Z])\b", flags=re.IGNORECASE)


def detect_task_type(answer: str) -> str:
    answer_text = str(answer or "").strip()
    if _SINGLE_LETTER_RE.fullmatch(answer_text):
        return "mcq"
    return "fill_blank"


def parse_valid_options(question: str) -> set[str]:
    text = str(question or "")
    options: set[str] = set()

    for match in _OPTION_LINE_RE.finditer(text):
        options.add(match.group(1).upper())

    list_text = re.sub(r"(?i)\s*,?\s*(?:and|or)\s*", ", ", text)
    for match in _OPTION_LIST_RE.finditer(list_text):
        letters = [letter.upper() for letter in re.findall(r"\b([A-Z])\b", match.group(0), flags=re.IGNORECASE)]
        if len(letters) >= 2:
            options.update(letters)

    for match in _OPTION_RANGE_RE.finditer(text):
        start = ord(match.group(1).upper())
        end = ord(match.group(2).upper())
        if start > end:
            start, end = end, start
        if 0 <= (end - start) <= 25:
            for code in range(start, end + 1):
                options.add(chr(code))

    options = {ch for ch in options if "A" <= ch <= "Z"}
    if not options:
        return {chr(code) for code in range(ord("A"), ord("Z") + 1)}
    return options


def _last_valid_match(response_text: str, pattern: str, valid_options: set[str]) -> str:
    matches = list(re.finditer(pattern, response_text, flags=re.IGNORECASE | re.MULTILINE))
    for match in reversed(matches):
        candidate = match.group(1).upper()
        if candidate in valid_options:
            return candidate.lower()
    return ""


def extract_mcq_pred(response_text: str, valid_options: set[str]) -> str:
    text = str(response_text or "")
    if not text:
        return ""

    patterns = [
        r"\*\*\s*(?:final\s+answer|answer|option|choice)?\s*[:：]?\s*([A-Z])\s*\*\*",
        r"(?:^|\b)(?:final\s+answer|answer|option|choice)\s*(?:is|:|：)\s*(?:\*\*)?\s*([A-Z])\s*(?:\*\*)?",
        r"(?:^|\b)(?:answer|option|choice)\s+([A-Z])\b",
        r"(?:^|\b)(?:i\s+(?:choose|pick)|my\s+answer\s+is)\s*[:：]?\s*(?:\*\*)?\s*([A-Z])\s*(?:\*\*)?",
        r"^\s*(?:\*\*)?\s*([A-Z])\s*(?:\*\*)?\s*$",
        r"^\s*[\(\[]?\s*(?:\*\*)?\s*([A-Z])\s*(?:\*\*)?\s*[\)\].,:;!\s]*$",
    ]

    for pattern in patterns:
        pred = _last_valid_match(text, pattern, valid_options)
        if pred:
            return pred

    tail_matches = list(
        re.finditer(
            r"(?:\*\*)?\b([A-Z])\b(?:\*\*)?[\)\].,:;!?\s]*$",
            text.strip(),
            flags=re.IGNORECASE | re.MULTILINE,
        )
    )
    for match in reversed(tail_matches):
        candidate = match.group(1).upper()
        if candidate in valid_options:
            return candidate.lower()
    return ""


def _is_edge_punct(ch: str) -> bool:
    return unicodedata.category(ch).startswith("P")


def strip_edge_punctuation(text: str) -> str:
    value = str(text or "")
    start = 0
    end = len(value)
    while start < end and _is_edge_punct(value[start]):
        start += 1
    while end > start and _is_edge_punct(value[end - 1]):
        end -= 1
    return value[start:end]


def _strip_markdown_wrappers(text: str) -> str:
    value = str(text or "").strip()
    while value:
        changed = False
        for left, right in (("**", "**"), ("__", "__"), ("`", "`")):
            if value.startswith(left) and value.endswith(right) and len(value) >= len(left) + len(right):
                value = value[len(left) : len(value) - len(right)].strip()
                changed = True
        if not changed:
            break
    return value


def clean_fill_candidate(text: str) -> str:
    value = _strip_markdown_wrappers(str(text or "").strip())
    value = value.strip()
    value = strip_edge_punctuation(value).strip()
    return value


def extract_fill_pred(response_text: str) -> str:
    text = str(response_text or "")
    if not text:
        return ""

    patterns = [
        r"\*\*\s*(?:final\s+answer|answer|答案)\s*[:：]\s*(.*?)\s*\*\*",
        r"(?:^|[\n\r])\s*(?:final\s+answer|answer|答案)\s*[:：]\s*(.+)$",
    ]
    for pattern in patterns:
        matches = list(re.finditer(pattern, text, flags=re.IGNORECASE | re.MULTILINE))
        for match in reversed(matches):
            candidate = clean_fill_candidate(match.group(1))
            if candidate:
                return candidate

    lines = [line.strip() for line in text.splitlines() if line.strip()]
    if not lines:
        return ""

    candidate = lines[-1]
    candidate = re.sub(r"^(?:[-*•>]+)\s*", "", candidate)
    candidate = re.sub(r"^(?:final\s+answer|answer|答案)\s*[:：]\s*", "", candidate, flags=re.IGNORECASE)
    return clean_fill_candidate(candidate)


def normalize_fill_text(text: str) -> str:
    value = unicodedata.normalize("NFKC", str(text or ""))
    value = value.casefold()
    value = re.sub(r"\s+", " ", value).strip()
    value = strip_edge_punctuation(value).strip()
    value = re.sub(r"\s+", " ", value).strip()
    return value


def grade_response(question: str, answer: str, response_text: str) -> dict:
    answer_text = str(answer or "").strip()
    task_type = detect_task_type(answer_text)

    if task_type == "mcq":
        valid_options = parse_valid_options(question)
        pred_raw = extract_mcq_pred(response_text, valid_options)
        pred_norm = pred_raw.lower() if pred_raw else ""
        answer_norm = answer_text.lower()
        extract_ok = bool(pred_norm)
        correct = bool(answer_norm) and pred_norm == answer_norm
        pred = pred_norm
    else:
        pred_raw = extract_fill_pred(response_text)
        pred_norm = normalize_fill_text(pred_raw)
        answer_norm = normalize_fill_text(answer_text)
        extract_ok = bool(pred_norm)
        correct = bool(answer_norm) and pred_norm == answer_norm
        pred = pred_raw

    return {
        "task_type": task_type,
        "pred": pred,
        "pred_raw": pred_raw,
        "pred_norm": pred_norm,
        "answer_norm": answer_norm,
        "extract_ok": extract_ok,
        "correct": correct,
    }