"""Symbol resolver: maps textual mentions to canonical company identities.

Uses an in-memory alias index built from company registry data. Returns
ranked candidates with confidence scores and ambiguity margins. Does NOT
invent tickers for unresolved mentions.
"""

from __future__ import annotations

from services.intelligence_pipeline_v3.resolution.alias_index import (
    AliasIndex,
    IndexEntry,
    build_alias_index,
)
from services.intelligence_pipeline_v3.resolution.models import (
    MatchType,
    MentionType,
    ResolutionCandidate,
    ResolutionResult,
    UnresolvedMention,
    UnresolvedReason,
)

# Ambiguity threshold: if the gap between top-2 candidates is below this,
# the result is marked as ambiguous.
_AMBIGUITY_THRESHOLD = 0.15


class SymbolResolver:
    """Resolve document mentions to canonical company identifiers.

    Usage:
        resolver = SymbolResolver()
        resolver.load_registry(companies)
        result = resolver.resolve("Apple")
    """

    def __init__(self, ambiguity_threshold: float = _AMBIGUITY_THRESHOLD) -> None:
        self._index = AliasIndex()
        self._ambiguity_threshold = ambiguity_threshold

    @property
    def index(self) -> AliasIndex:
        """Access the underlying alias index."""
        return self._index

    def load_registry(self, companies: list[dict]) -> None:
        """Load company data into the alias index.

        Each company dict should contain at minimum:
            - id: str (company UUID)
            - ticker: str
            - legal_name: str

        Optional fields:
            - aliases: list[dict] with keys "alias" and optionally "alias_type"
              OR list[tuple[str, str]] of (alias_text, alias_type)

        Uses `build_alias_index` to construct the full index from registry data.
        """
        self._index = build_alias_index(companies)

    def resolve(
        self,
        mention: str,
        context: str = "",
        mention_type: MentionType = MentionType.explicit,
    ) -> ResolutionResult:
        """Resolve a textual mention to ranked company candidates.

        Args:
            mention: The text to resolve (ticker, name, alias, etc.)
            context: Optional surrounding text for future disambiguation use.
            mention_type: Whether this is an explicit mention or inferred exposure.

        Returns:
            ResolutionResult with ranked candidates, ambiguity margin, and metadata.
            If no match is found, candidates list is empty.
        """
        entries = self._index.lookup(mention)

        if not entries:
            return ResolutionResult(
                candidates=[],
                ambiguity_margin=1.0,
                is_ambiguous=False,
                mention_type=mention_type,
            )

        # Deduplicate by company_id, keeping the best match type per company.
        best_per_company: dict[str, IndexEntry] = {}
        for entry in entries:
            existing = best_per_company.get(entry.company_id)
            if existing is None or _match_priority(entry.match_type) > _match_priority(existing.match_type):
                best_per_company[entry.company_id] = entry

        # Score candidates.
        candidates: list[ResolutionCandidate] = []
        for entry in best_per_company.values():
            confidence = _score_match(entry.match_type, mention, entry)
            candidates.append(
                ResolutionCandidate(
                    company_id=entry.company_id,
                    ticker=entry.ticker,
                    name=entry.name,
                    confidence=confidence,
                    match_type=MatchType(entry.match_type),
                )
            )

        # Sort by confidence descending.
        candidates.sort(key=lambda c: c.confidence, reverse=True)

        # Calculate ambiguity margin.
        if len(candidates) >= 2:
            ambiguity_margin = candidates[0].confidence - candidates[1].confidence
        else:
            ambiguity_margin = 1.0

        is_ambiguous = ambiguity_margin < self._ambiguity_threshold

        return ResolutionResult(
            candidates=candidates,
            ambiguity_margin=ambiguity_margin,
            is_ambiguous=is_ambiguous,
            mention_type=mention_type,
        )

    def resolve_or_unresolved(
        self,
        mention: str,
        start_char: int,
        end_char: int,
        context: str = "",
        mention_type: MentionType = MentionType.explicit,
    ) -> ResolutionResult | UnresolvedMention:
        """Resolve a mention, returning UnresolvedMention if no match found.

        This ensures unresolved mentions are preserved with their literal text
        and position rather than having a ticker invented.
        """
        result = self.resolve(mention, context=context, mention_type=mention_type)

        if not result.candidates:
            return UnresolvedMention(
                literal_text=mention,
                start_char=start_char,
                end_char=end_char,
                reason=UnresolvedReason.not_in_registry,
            )

        if result.is_ambiguous:
            return UnresolvedMention(
                literal_text=mention,
                start_char=start_char,
                end_char=end_char,
                reason=UnresolvedReason.ambiguous,
            )

        return result


def _match_priority(match_type: str) -> int:
    """Higher priority = stronger match type."""
    priorities = {
        "exact_ticker": 3,
        "exact_name": 2,
        "alias": 1,
        "fuzzy": 0,
    }
    return priorities.get(match_type, 0)


def _score_match(match_type: str, mention: str, entry: IndexEntry) -> float:
    """Score a match based on type and exact-match quality.

    Exact ticker matches get highest confidence, then exact name, then alias.
    """
    base_scores = {
        "exact_ticker": 0.95,
        "exact_name": 0.90,
        "alias": 0.80,
        "fuzzy": 0.50,
    }
    return base_scores.get(match_type, 0.50)