"""Conservative, exact-match-safe final answer formatting."""

from __future__ import annotations

import re
import unicodedata
from decimal import Decimal, InvalidOperation

_PREFIX = re.compile(
    r"^\s*(?:final\s+answer|answer|submitted\s+answer)\s*:\s*", re.IGNORECASE
)


def format_answer(value: object) -> str:
    """Remove presentation noise without changing answer semantics or case."""
    text = unicodedata.normalize("NFC", str(value or ""))
    text = text.replace("\r\n", "\n").replace("\r", "\n").strip()
    had_prefix = bool(_PREFIX.match(text))
    text = _PREFIX.sub("", text).strip()
    if text.startswith("```") and text.endswith("```"):
        lines = text.splitlines()
        if len(lines) >= 3:
            text = "\n".join(lines[1:-1]).strip()
    if len(text) >= 2 and text[0] == text[-1] and text[0] in {'"', "'", "`"}:
        text = text[1:-1].strip()
    text = re.split(
        r"\n+(?:explanation|reasoning|evidence|source)s?\s*:",
        text,
        maxsplit=1,
        flags=re.IGNORECASE,
    )[0]
    if had_prefix and "\n" in text:
        text = next((line.strip() for line in text.splitlines() if line.strip()), "")
    if had_prefix:
        text = re.split(
            r"\s+(?:because|since)\s+", text, maxsplit=1, flags=re.IGNORECASE
        )[0].strip()
    # GAIA submissions are scalar strings; collapse accidental wrapping while
    # preserving meaningful punctuation, casing, currency symbols, and commas.
    text = re.sub(r"\s+", " ", text).strip()
    if not text:
        raise ValueError("Agent returned an empty answer")
    return text


def apply_requested_format(question: str, answer: object) -> str:
    """Apply only explicit output-format constraints from the question."""
    text = format_answer(answer)
    lowered = question.lower()
    if "usd" in lowered and "two decimal" in lowered:
        numeric = re.sub(r"[^0-9.\-]", "", text)
        try:
            return f"${Decimal(numeric):,.2f}"
        except InvalidOperation:
            return text
    if "ascending order" in lowered and (
        "comma-delimited" in lowered or "comma separated" in lowered
    ):
        values = re.findall(r"-?\d+(?:\.\d+)?", text)
        if values:
            values.sort(key=Decimal)
            return ", ".join(values)
    if "alphabet" in lowered and ("comma" in lowered or "list" in lowered):
        values = [item.strip() for item in text.split(",") if item.strip()]
        if len(values) > 1:
            return ", ".join(sorted(values, key=str.casefold))
    return text