"""Core evidence verifier for Intelligence Pipeline v3.

Validates offsets, entity-evidence associations, and numeric consistency
for extracted candidates against source text and evidence spans.
"""

from __future__ import annotations

import re
from dataclasses import dataclass, field
from datetime import datetime, timezone

from services.intelligence_pipeline_v3.verification.models import (
    AssociationVerification,
    NumericVerification,
    OffsetVerification,
    RejectedCandidate,
    RejectionReason,
    VerificationReport,
)


@dataclass
class EvidenceSpan:
    """Minimal evidence span representation for verification."""

    id: str
    start_char: int
    end_char: int
    text: str


@dataclass
class Entity:
    """Minimal entity representation for verification."""

    id: str
    literal_text: str
    evidence_ids: list[str]


@dataclass
class NumericFact:
    """Minimal numeric fact representation for verification."""

    id: str
    literal_value: str
    normalized_value: float | None
    evidence_ids: list[str]


@dataclass
class Candidate:
    """Generic candidate for full verification."""

    candidate_type: str
    candidate_id: str
    candidate_data: dict = field(default_factory=dict)
    evidence_ids: list[str] = field(default_factory=list)
    literal_text: str | None = None
    normalized_value: float | None = None


# Regex for extracting numbers from text (integers, decimals, negative)
_NUMBER_RE = re.compile(r"-?\d[\d,]*\.?\d*")


def _extract_numbers(text: str) -> list[float]:
    """Extract all numeric values from a string."""
    results: list[float] = []
    for match in _NUMBER_RE.finditer(text):
        try:
            # Remove commas before parsing
            cleaned = match.group().replace(",", "")
            results.append(float(cleaned))
        except ValueError:
            continue
    return results


class EvidenceVerifier:
    """Verifies evidence spans, entity associations, and numeric consistency.

    Implements requirement 8 (Evidence Verification and Grounding):
    - Validates span offsets match source text
    - Checks entity text appears in linked evidence spans
    - Verifies numeric values can be found in evidence text
    - Produces a full verification report with rejected candidates
    """

    def __init__(self, numeric_tolerance: float = 0.01) -> None:
        """Initialize the verifier.

        Args:
            numeric_tolerance: Relative tolerance for numeric comparison (default 1%).
        """
        self._numeric_tolerance = numeric_tolerance
        self._rejected: list[RejectedCandidate] = []

    @property
    def rejected_candidates(self) -> list[RejectedCandidate]:
        """All rejected candidates accumulated during verification."""
        return list(self._rejected)

    def reset(self) -> None:
        """Clear accumulated rejected candidates."""
        self._rejected = []

    def verify_offsets(
        self, spans: list[EvidenceSpan], source_text: str
    ) -> list[OffsetVerification]:
        """Check that each span's text matches the source at declared offsets.

        Args:
            spans: Evidence spans with start_char, end_char, and text.
            source_text: The full original document text.

        Returns:
            A list of OffsetVerification results, one per span.
        """
        results: list[OffsetVerification] = []
        for span in spans:
            # Bounds check
            if span.start_char < 0 or span.end_char > len(source_text):
                results.append(
                    OffsetVerification(
                        span_id=span.id,
                        valid=False,
                        reason=(
                            f"Offset out of bounds: start={span.start_char}, "
                            f"end={span.end_char}, source_length={len(source_text)}"
                        ),
                    )
                )
                self._reject_span(span, RejectionReason.INVALID_OFFSET)
                continue

            if span.end_char <= span.start_char:
                results.append(
                    OffsetVerification(
                        span_id=span.id,
                        valid=False,
                        reason=f"Invalid range: end_char ({span.end_char}) <= start_char ({span.start_char})",
                    )
                )
                self._reject_span(span, RejectionReason.INVALID_OFFSET)
                continue

            # Extract text at offsets and compare
            actual_text = source_text[span.start_char : span.end_char]
            if actual_text == span.text:
                results.append(OffsetVerification(span_id=span.id, valid=True))
            else:
                results.append(
                    OffsetVerification(
                        span_id=span.id,
                        valid=False,
                        reason=(
                            f"Text mismatch at [{span.start_char}:{span.end_char}]: "
                            f"expected {span.text!r}, found {actual_text!r}"
                        ),
                    )
                )
                self._reject_span(span, RejectionReason.TEXT_MISMATCH)

        return results

    def verify_entity_association(
        self, entity: Entity, evidence_spans: list[EvidenceSpan]
    ) -> AssociationVerification:
        """Check that entity text appears in at least one linked evidence span.

        The check is case-insensitive to handle variation in capitalization.

        Args:
            entity: Entity with literal_text and evidence_ids.
            evidence_spans: All available evidence spans.

        Returns:
            AssociationVerification indicating whether the entity is supported.
        """
        # Build a map of span_id -> span for quick lookup
        span_map = {s.id: s for s in evidence_spans}
        entity_lower = entity.literal_text.lower()

        for eid in entity.evidence_ids:
            span = span_map.get(eid)
            if span and entity_lower in span.text.lower():
                return AssociationVerification(entity_id=entity.id, valid=True)

        reason = (
            f"Entity text {entity.literal_text!r} not found in any linked evidence span "
            f"(checked {len(entity.evidence_ids)} spans)"
        )
        self._rejected.append(
            RejectedCandidate(
                candidate_type="entity",
                candidate_data={
                    "entity_id": entity.id,
                    "literal_text": entity.literal_text,
                    "evidence_ids": entity.evidence_ids,
                },
                rejection_reason=RejectionReason.ENTITY_NOT_IN_EVIDENCE,
                stage="entity_association_verification",
                timestamp=datetime.now(tz=timezone.utc),
            )
        )
        return AssociationVerification(
            entity_id=entity.id, valid=False, reason=reason
        )

    def verify_numeric_consistency(
        self, fact: NumericFact, evidence_spans: list[EvidenceSpan]
    ) -> NumericVerification:
        """Check that a numeric fact's value can be found in its evidence text.

        Looks for the literal value or the normalized value within the text of
        linked evidence spans. Uses tolerance-aware comparison for normalized values.

        Args:
            fact: Numeric fact with literal_value, normalized_value, and evidence_ids.
            evidence_spans: All available evidence spans.

        Returns:
            NumericVerification indicating whether the value was found.
        """
        span_map = {s.id: s for s in evidence_spans}
        expected_str = fact.literal_value

        # First: check if literal value string appears in any linked span
        for eid in fact.evidence_ids:
            span = span_map.get(eid)
            if span and fact.literal_value in span.text:
                return NumericVerification(
                    fact_id=fact.id,
                    valid=True,
                    found_value=fact.literal_value,
                    expected_value=expected_str,
                )

        # Second: if we have a normalized value, look for numeric matches
        if fact.normalized_value is not None:
            for eid in fact.evidence_ids:
                span = span_map.get(eid)
                if not span:
                    continue
                numbers = _extract_numbers(span.text)
                for num in numbers:
                    if self._values_match(num, fact.normalized_value):
                        return NumericVerification(
                            fact_id=fact.id,
                            valid=True,
                            found_value=str(num),
                            expected_value=expected_str,
                        )

        # Rejection
        reason = (
            f"Value {expected_str!r} (normalized={fact.normalized_value}) "
            f"not found in evidence spans"
        )
        self._rejected.append(
            RejectedCandidate(
                candidate_type="fact",
                candidate_data={
                    "fact_id": fact.id,
                    "literal_value": fact.literal_value,
                    "normalized_value": fact.normalized_value,
                    "evidence_ids": fact.evidence_ids,
                },
                rejection_reason=RejectionReason.NUMERIC_INCONSISTENCY,
                stage="numeric_consistency_verification",
                timestamp=datetime.now(tz=timezone.utc),
            )
        )
        return NumericVerification(
            fact_id=fact.id,
            valid=False,
            found_value=None,
            expected_value=expected_str,
            reason=reason,
        )

    def verify_all(
        self,
        candidates: list[Candidate],
        evidence_spans: list[EvidenceSpan],
        source_text: str,
    ) -> VerificationReport:
        """Run full verification across all candidates.

        Performs offset verification on spans, then entity association and
        numeric consistency for each candidate as appropriate.

        Args:
            candidates: All extraction candidates to verify.
            evidence_spans: All evidence spans in the document.
            source_text: Full original document text.

        Returns:
            A VerificationReport summarizing the verification results.
        """
        self.reset()

        # Step 1: Verify all span offsets
        offset_results = self.verify_offsets(evidence_spans, source_text)
        valid_span_ids = {r.span_id for r in offset_results if r.valid}

        # Step 2: Filter spans to only valid ones for downstream checks
        valid_spans = [s for s in evidence_spans if s.id in valid_span_ids]

        total = len(candidates)
        verified = 0

        for candidate in candidates:
            # Filter candidate's evidence_ids to only valid spans
            linked_valid_spans = [
                s for s in valid_spans if s.id in set(candidate.evidence_ids)
            ]

            if not linked_valid_spans and candidate.evidence_ids:
                # All linked spans were invalid
                self._rejected.append(
                    RejectedCandidate(
                        candidate_type=candidate.candidate_type,
                        candidate_data=candidate.candidate_data,
                        rejection_reason=RejectionReason.INVALID_OFFSET,
                        stage="full_verification",
                        timestamp=datetime.now(tz=timezone.utc),
                    )
                )
                continue

            # Entity association check
            if candidate.literal_text is not None:
                entity = Entity(
                    id=candidate.candidate_id,
                    literal_text=candidate.literal_text,
                    evidence_ids=candidate.evidence_ids,
                )
                assoc = self.verify_entity_association(entity, valid_spans)
                if not assoc.valid:
                    continue

            # Numeric consistency check
            if candidate.normalized_value is not None:
                fact = NumericFact(
                    id=candidate.candidate_id,
                    literal_value=candidate.literal_text or str(candidate.normalized_value),
                    normalized_value=candidate.normalized_value,
                    evidence_ids=candidate.evidence_ids,
                )
                num_check = self.verify_numeric_consistency(fact, valid_spans)
                if not num_check.valid:
                    continue

            verified += 1

        rejected = total - verified
        coverage_rate = verified / total if total > 0 else 1.0

        # Build rejection breakdown
        breakdown: dict[str, int] = {}
        for rc in self._rejected:
            key = rc.rejection_reason.value
            breakdown[key] = breakdown.get(key, 0) + 1

        return VerificationReport(
            total_candidates=total,
            verified=verified,
            rejected=rejected,
            coverage_rate=coverage_rate,
            rejection_breakdown=breakdown,
        )

    def _values_match(self, found: float, expected: float) -> bool:
        """Compare two numeric values with tolerance."""
        if expected == 0:
            return abs(found) < self._numeric_tolerance
        return abs(found - expected) / abs(expected) <= self._numeric_tolerance

    def _reject_span(self, span: EvidenceSpan, reason: RejectionReason) -> None:
        """Record a span rejection."""
        self._rejected.append(
            RejectedCandidate(
                candidate_type="evidence_span",
                candidate_data={
                    "span_id": span.id,
                    "start_char": span.start_char,
                    "end_char": span.end_char,
                    "text": span.text[:100],  # Truncate for storage
                },
                rejection_reason=reason,
                stage="offset_verification",
                timestamp=datetime.now(tz=timezone.utc),
            )
        )