"""Hybrid search over file_store using RRF fusion of vector + keyword results."""

import asyncio
import datetime
import os
from typing import Final

from ..base_step import BaseStep
from ..file_io import extract_daily_date
from ...components import R
from ...schema import FileChunk
from ...utils import expand_links, render_expansion_lines

_RRF_K: Final = 60
_MAX_CANDIDATES: Final = 200
_DEFAULT_LIMIT_ENV: Final = "REME_SEARCH_LIMIT"
_DEFAULT_LIMIT: Final = 5


def _default_limit() -> int:
    value = os.getenv(_DEFAULT_LIMIT_ENV)
    if value is None:
        return _DEFAULT_LIMIT
    try:
        return int(value)
    except ValueError:
        return _DEFAULT_LIMIT


def _filter_values(value: object) -> set:
    """Normalize a scalar or collection-valued search filter."""
    if isinstance(value, (list, tuple, set, frozenset)):
        return set(value)
    return {value}


@R.register("search_step")
class SearchStep(BaseStep):
    """Hybrid search: run vector + keyword in parallel, fuse via RRF, filter, truncate."""

    TOOL_CONTEXTS_KEY: Final[str] = "tool_contexts"
    SEARCH_SEEN_KEY: Final[str] = "search_seen_chunk_ids"

    def __init__(
        self,
        *args,
        seen_ttl_hours: float = 24,
        **kwargs,
    ):
        super().__init__(*args, **kwargs)
        self.seen_ttl_hours = seen_ttl_hours

    @staticmethod
    def _rrf_merge(
        vector: list[FileChunk],
        keyword: list[FileChunk],
        vector_weight: float,
    ) -> list[FileChunk]:
        """Fuse two ranked lists with Reciprocal Rank Fusion, keyed by chunk.id."""
        text_weight = 1.0 - vector_weight
        merged: dict[str, FileChunk] = {}

        for rank, chunk in enumerate(vector, start=1):
            contrib = vector_weight / (_RRF_K + rank)
            c = chunk.model_copy(deep=False)
            c.scores = {**chunk.scores, "vector": chunk.scores.get("vector", chunk.score), "score": contrib}
            merged[c.id] = c

        for rank, chunk in enumerate(keyword, start=1):
            contrib = text_weight / (_RRF_K + rank)
            existing = merged.get(chunk.id)
            if existing is not None:
                existing.scores = {
                    **existing.scores,
                    "keyword": chunk.scores.get("keyword", chunk.score),
                    "score": existing.scores["score"] + contrib,
                }
            else:
                c = chunk.model_copy(deep=False)
                c.scores = {**chunk.scores, "keyword": chunk.scores.get("keyword", chunk.score), "score": contrib}
                merged[c.id] = c

        results = list(merged.values())
        results.sort(key=lambda r: r.score, reverse=True)
        return results

    @staticmethod
    def _format_scores(scores: dict[str, float], hybrid: bool) -> str:
        """Format scores for the answer line: always show fused; show per-branch when hybrid."""
        parts = [f"score={scores.get('score', 0.0):.4f}"]
        if hybrid:
            for k in ("vector", "keyword"):
                v = scores.get(k)
                parts.append(f"{k}={v:.4f}" if v is not None else f"{k}=-")
        return " ".join(parts)

    @staticmethod
    def _now_ts() -> float:
        return datetime.datetime.now().timestamp()

    def _tool_context_store(self, tool_context_id: str) -> dict:
        """Return the mutable state bucket for a tool context."""
        if self.app_context is not None:
            contexts = self.app_context.metadata.setdefault(self.TOOL_CONTEXTS_KEY, {})
        else:
            contexts = self.kwargs.setdefault(self.TOOL_CONTEXTS_KEY, {})
        return contexts.setdefault(tool_context_id, {})

    def _dedupe_tool_context(
        self,
        chunks: list[FileChunk],
        tool_context_id: str,
        limit: int,
    ) -> tuple[list[FileChunk], dict]:
        now = self.kwargs.get("clock", self._now_ts)()
        ttl = float(
            self.kwargs.get(
                "tool_context_chunk_ttl_seconds",
                float(self.seen_ttl_hours) * 60 * 60,
            ),
        )
        store = self._tool_context_store(tool_context_id)
        seen = store.get(self.SEARCH_SEEN_KEY, {})
        if not isinstance(seen, dict):
            seen = dict.fromkeys(seen, now)
        before_expire = len(seen)
        store[self.SEARCH_SEEN_KEY] = seen = {chunk_id: ts for chunk_id, ts in seen.items() if now - float(ts) < ttl}

        seen_before = len(seen)
        unvisited = [chunk for chunk in chunks if chunk.id not in seen]
        returned = unvisited[:limit]
        for chunk in returned:
            seen[chunk.id] = now

        return returned, {
            "tool_context_id": tool_context_id,
            "seen_before": seen_before,
            "skipped_seen": len(chunks) - len(unvisited),
            "seen_after": len(seen),
            "expired": before_expire - seen_before,
            "ttl_seconds": ttl,
        }

    async def _resolve_tag_filter(
        self,
        raw_tags: object,
        search_filter: dict,
    ) -> tuple[dict, dict | None, str | None]:
        """Merge tag-derived paths into the ordinary file-store filter."""
        if not raw_tags:
            return search_filter, None, None

        if not self.file_store.tag_index_enabled:
            self.logger.warning(
                f"[{self.name}] tags requested but tag_index_unavailable",
            )
            return (
                search_filter,
                {"requested": True, "applied": False, "reason": "tag_index_unavailable"},
                None,
            )
        tag_index = self.file_store.require_tag_index()
        if not tag_index.is_healthy:
            self.logger.warning(f"[{self.name}] tags requested but tag_index_unavailable")
            return (
                search_filter,
                {"requested": True, "applied": False, "reason": "tag_index_unavailable"},
                None,
            )

        normalized_tags = tag_index.normalize_query_tags(raw_tags)
        if not normalized_tags:
            return search_filter, None, "Error: tags contained no valid values"

        allowed_paths = set(await tag_index.paths_for_tags(normalized_tags, match_all=False))
        matched_path_count = len(allowed_paths)
        if not tag_index.is_healthy:
            self.logger.warning(
                f"[{self.name}] tag index became unhealthy during lookup",
            )
            return (
                search_filter,
                {"requested": True, "applied": False, "reason": "tag_index_unavailable"},
                None,
            )

        exact_paths = set()
        has_exact_path_filter = False
        for key in ("path", "paths"):
            if key in search_filter:
                has_exact_path_filter = True
                exact_paths.update(_filter_values(search_filter.pop(key)))
        if has_exact_path_filter:
            allowed_paths.intersection_update(exact_paths)
        search_filter["paths"] = sorted(allowed_paths)
        metadata = {
            "requested": True,
            "applied": True,
            "tags": normalized_tags,
            "matched_paths": matched_path_count,
        }
        return search_filter, metadata, None

    async def execute(self):
        assert self.context is not None
        query: str = (self.context.get("query", "") or "").strip()
        limit: int = int(self.context.get("limit") or _default_limit())
        min_score: float = float(self.context.get("min_score") or 0.0)
        # vector_weight: prefer agent-supplied context value; fallback to YAML kwargs / default 0.7.
        # Convertible numeric inputs are clipped to [0.0, 1.0]; non-numeric inputs are silently ignored.
        raw_vw = self.context.get("vector_weight")
        vector_weight: float | None = None
        if raw_vw is not None:
            try:
                vector_weight = float(raw_vw)
            except (TypeError, ValueError):
                self.logger.warning(
                    f"[{self.name}] non-numeric vector_weight={raw_vw!r}; ignoring and using default 0.7",
                )
                vector_weight = None
        if vector_weight is None:
            vector_weight = float(self.kwargs.get("vector_weight", 0.7))
        vector_weight = max(0.0, min(1.0, vector_weight))
        candidate_multiplier: float = float(self.kwargs.get("candidate_multiplier", 5.0))
        expand_links_enabled: bool = bool(self.kwargs.get("expand_links", True))
        max_links_per_direction: int = int(self.kwargs.get("max_links_per_direction", 10))
        tool_context_id: str = (self.context.get("tool_context_id", "") or "").strip()
        max_search_calls = self.context.get("max_search_calls")
        strict_date_filter: bool = bool(
            self.context.get("strict_date_filter") or self.kwargs.get("strict_date_filter", False),
        )

        if not query:
            self.context.response.success = False
            self.context.response.answer = "Error: query cannot be empty"
            return self.context.response
        assert limit > 0, f"limit must be positive, got {limit}"

        if max_search_calls is not None:
            if not tool_context_id or self.app_context is None:
                raise ValueError("max_search_calls requires an application and tool_context_id")
            maximum = int(max_search_calls)
            if maximum < 1:
                raise ValueError("max_search_calls must be positive")
            budgets = self.app_context.metadata.setdefault("__search_call_budgets", {})
            budget = budgets.setdefault(tool_context_id, {"count": 0, "lock": asyncio.Lock()})
            async with budget["lock"]:
                if budget["count"] >= maximum:
                    self.logger.warning(
                        f"[{self.name}] search budget exhausted context={tool_context_id} limit={maximum}",
                    )
                    self.context.response.success = False
                    self.context.response.answer = f"Error: search call limit of {maximum} reached"
                    return self.context.response
                budget["count"] += 1
                self.logger.info(
                    f"[{self.name}] search budget context={tool_context_id} " f"call={budget['count']}/{maximum}",
                )

        candidates = min(_MAX_CANDIDATES, max(1, int(limit * candidate_multiplier)))
        search_filter: dict = dict(self.context.get("search_filter", {}) or {})
        raw_tags = self.context.get("tags", []) or []

        # Promote top-level date parameters into search_filter for file_store.
        for date_key in ("start_date", "end_date"):
            value = self.context.get(date_key)
            if value and date_key not in search_filter:
                search_filter[date_key] = value

        # Validate and normalize date filters before they reach file_store.
        # _matches_search_filter does lexicographic string comparison against
        # path_date (always a canonical YYYY-MM-DD), so raw caller values like
        # "2026-2-28" or "abc" would produce silently wrong results.
        for date_key in ("start_date", "end_date"):
            raw = search_filter.get(date_key)
            if raw is None:
                continue
            normalized = extract_daily_date(raw)
            if normalized is None:
                # Fallback: accept non-zero-padded dates like "2024-1-5".
                try:
                    normalized = (
                        datetime.datetime.strptime(
                            str(raw).strip(),
                            "%Y-%m-%d",
                        )
                        .date()
                        .isoformat()
                    )
                except ValueError:
                    self.logger.warning(
                        f"Ignoring invalid {date_key}={raw!r}; " f"expected a valid YYYY-MM-DD date.",
                    )
                    del search_filter[date_key]
                    continue
            search_filter[date_key] = normalized

        if strict_date_filter:
            search_filter["strict_date_filter"] = True

        search_filter, tag_filter_metadata, tag_error = await self._resolve_tag_filter(raw_tags, search_filter)
        if tag_error is not None:
            self.context.response.success = False
            self.context.response.answer = tag_error
            if tag_filter_metadata is not None:
                self.context.response.metadata["tag_filter"] = tag_filter_metadata
            return self.context.response

        text_weight = 1.0 - vector_weight
        use_vector = vector_weight > 0.0
        use_keyword = text_weight > 0.0

        if use_vector and use_keyword:
            vector_results, keyword_results = await asyncio.gather(
                self.file_store.vector_search(query, candidates, search_filter),
                self.file_store.keyword_search(query, candidates, search_filter),
            )
        elif use_vector:
            vector_results = await self.file_store.vector_search(query, candidates, search_filter)
            keyword_results = []
        else:
            vector_results = []
            keyword_results = await self.file_store.keyword_search(query, candidates, search_filter)

        self.logger.info(
            f"[{self.name}] query={query!r} candidates={candidates} "
            f"vector_hits={len(vector_results)} keyword_hits={len(keyword_results)}",
        )

        hybrid = bool(vector_results) and bool(keyword_results)
        if not vector_results and not keyword_results:
            fused: list[FileChunk] = []
        elif not keyword_results:
            fused = vector_results
        elif not vector_results:
            fused = keyword_results
        else:
            fused = self._rrf_merge(vector_results, keyword_results, vector_weight)

        if min_score > 0.0:
            fused = [c for c in fused if c.score >= min_score]

        dedup: dict | None = None
        if tool_context_id:
            fused, dedup = self._dedupe_tool_context(fused, tool_context_id, limit)
        else:
            fused = fused[:limit]

        unique_paths = list(dict.fromkeys(c.path for c in fused))
        link_expansion: dict[str, dict] = (
            await expand_links(self.file_store, unique_paths, max_links_per_direction) if expand_links_enabled else {}
        )

        answer_lines: list[str] = []
        for c in fused:
            answer_lines.append(
                f"========== {c.path}:{c.start_line}-{c.end_line} "
                f"[{self._format_scores(c.scores, hybrid)}] ==========\n{c.text}",
            )
            answer_lines.extend(render_expansion_lines(link_expansion.get(c.path, {})))

        self.context.response.answer = "\n".join(answer_lines)
        self.context.response.metadata["results"] = [
            c.model_dump(exclude_none=True, exclude={"embedding"}) for c in fused
        ]
        self.context.response.metadata["link_expansion"] = link_expansion
        self.context.response.metadata["counts"] = {
            "vector": len(vector_results),
            "keyword": len(keyword_results),
            "returned": len(fused),
            "hybrid": hybrid,
        }
        if tag_filter_metadata is not None:
            self.context.response.metadata["tag_filter"] = tag_filter_metadata
        if dedup is not None:
            self.context.response.metadata["dedup"] = dedup
        return self.context.response