"""Single-document claim extraction logic.

Given one Type/Document atom, this module:

  1. Builds the extraction prompt from the versioned template
  2. Calls Qwen 397B (REASONING role) for structured JSON output
  3. Parses + validates each claim:
     - Required fields present and right types
     - Stance is in the allowed enum
     - Confidence above threshold
     - Quote is a verbatim substring of the source (programmatic check —
       this is the cheap defense against LLM hallucination)
  4. Returns a list of ExtractedClaim dataclasses ready for the pusher.

The pusher (push.py) takes ExtractedClaim and creates a Type/Claim atom in
Atomic, with the proper tag inheritance and a stable hash-based source_url.
"""

from __future__ import annotations

import hashlib
import re
from dataclasses import dataclass
from pathlib import Path
from typing import Any

from shared.config import LlmRole
from shared.llm_client import LlmClient, LlmError
from shared.logging import get_logger

log = get_logger(__name__)

PROMPT_VERSION = "v1"
PROMPT_PATH = Path(__file__).resolve().parent / "prompts" / f"claim_extraction_{PROMPT_VERSION}.md"
ALLOWED_STANCES = {"ASSERTS", "REPORTS", "REFUTES", "QUESTIONS", "NEUTRAL"}
MIN_CONFIDENCE = 0.7
MIN_CLAIM_CHARS = 20
MIN_QUOTE_CHARS = 10
MAX_QUOTE_CHARS = 600
MAX_INPUT_CHARS = 120_000  # ~30K tokens, well under Qwen's 262K context

_PROMPT_TEMPLATE: str | None = None


def _load_prompt() -> str:
    global _PROMPT_TEMPLATE
    if _PROMPT_TEMPLATE is None:
        _PROMPT_TEMPLATE = PROMPT_PATH.read_text(encoding="utf-8")
    return _PROMPT_TEMPLATE


# ============================================================ data structures


@dataclass(slots=True, frozen=True)
class ExtractedClaim:
    claim: str
    quote: str
    stance: str             # uppercase: ASSERTS / REPORTS / REFUTES / QUESTIONS / NEUTRAL
    confidence: float

    def stable_hash(self) -> str:
        """8-char SHA-1 of canonicalized claim text — used in source_url fragment."""
        canonical = " ".join(self.claim.lower().strip().split())
        return hashlib.sha1(canonical.encode("utf-8")).hexdigest()[:8]


@dataclass(slots=True)
class ExtractionResult:
    """What `extract_claims_from_atom` returns."""

    raw_count: int          # how many items the LLM returned
    valid: list[ExtractedClaim]
    rejected: dict[str, int]  # reason → count
    backend: str            # which backend served the request


# ============================================================ extraction core


async def extract_claims_from_atom(
    llm: LlmClient,
    *,
    title: str,
    language: str,
    content: str,
    max_tokens_out: int = 6000,
) -> ExtractionResult:
    """Run the extraction LLM call and validate the results.

    Raises LlmError on transport / JSON parse failure (caller decides whether
    to retry or skip the document).
    """
    prompt = _load_prompt().replace("{title}", title)
    prompt = prompt.replace("{language}", language)
    truncated = content[:MAX_INPUT_CHARS]
    if len(content) > MAX_INPUT_CHARS:
        truncated += "\n\n[document truncated for extraction]"
    prompt = prompt.replace("{content}", truncated)

    result, usage = await llm.chat_json(
        role=LlmRole.REASONING,
        system=(
            "You are a precise information extractor. Output strictly valid "
            "JSON, no commentary, no markdown fences."
        ),
        user=prompt,
        max_tokens=max_tokens_out,
        temperature=0.0,
    )

    if not isinstance(result, dict) or "claims" not in result:
        raise LlmError(
            f"unexpected response shape: keys={list(result.keys()) if isinstance(result, dict) else type(result).__name__}"
        )

    raw_claims = result.get("claims") or []
    if not isinstance(raw_claims, list):
        raise LlmError(f"`claims` is not a list: {type(raw_claims).__name__}")

    valid: list[ExtractedClaim] = []
    rejected: dict[str, int] = {}

    norm_source = _normalize_for_match(content)

    for raw in raw_claims:
        outcome = _parse_one(raw, norm_source)
        if isinstance(outcome, ExtractedClaim):
            valid.append(outcome)
        else:
            rejected[outcome] = rejected.get(outcome, 0) + 1

    # Dedup within this batch by stable hash
    seen: set[str] = set()
    deduped: list[ExtractedClaim] = []
    for c in valid:
        h = c.stable_hash()
        if h in seen:
            rejected["intra_batch_duplicate"] = rejected.get("intra_batch_duplicate", 0) + 1
            continue
        seen.add(h)
        deduped.append(c)

    return ExtractionResult(
        raw_count=len(raw_claims),
        valid=deduped,
        rejected=rejected,
        backend=str(usage.get("backend", "")),
    )


# ============================================================ validation


def _parse_one(raw: Any, norm_source: str) -> ExtractedClaim | str:
    """Validate one raw item from the LLM. Returns ExtractedClaim or error reason str."""
    if not isinstance(raw, dict):
        return "not_a_dict"

    claim = (raw.get("claim") or "").strip()
    quote = (raw.get("quote") or "").strip()
    stance = (raw.get("stance") or "").strip().upper()
    try:
        confidence = float(raw.get("confidence", 0))
    except (TypeError, ValueError):
        return "bad_confidence_type"

    if len(claim) < MIN_CLAIM_CHARS:
        return "claim_too_short"
    if len(quote) < MIN_QUOTE_CHARS:
        return "quote_too_short"
    if len(quote) > MAX_QUOTE_CHARS:
        return "quote_too_long"
    if stance not in ALLOWED_STANCES:
        return "bad_stance"
    if confidence < MIN_CONFIDENCE:
        return "low_confidence"

    # The critical anti-hallucination check: the quote must actually appear
    # in the source document (after whitespace normalization).
    if not _quote_in_source(quote, norm_source):
        return "quote_not_in_source"

    return ExtractedClaim(
        claim=claim,
        quote=quote,
        stance=stance,
        confidence=confidence,
    )


_WHITESPACE_RE = re.compile(r"\s+")


def _normalize_for_match(s: str) -> str:
    """Collapse runs of whitespace and normalize quote chars for substring match."""
    s = s.replace("\u2018", "'").replace("\u2019", "'")
    s = s.replace("\u201c", '"').replace("\u201d", '"')
    s = s.replace("\u2013", "-").replace("\u2014", "-")
    return _WHITESPACE_RE.sub(" ", s).strip()


def _quote_in_source(quote: str, norm_source: str) -> bool:
    return _normalize_for_match(quote) in norm_source