"""Repository boundaries for Chroma-backed evidence and project memory."""

from __future__ import annotations

import json
from dataclasses import dataclass
from typing import Any, Iterable, Sequence

from app.observability.operation import observe_operation
from app.rag.chromadb_client import ChromaDBClient
from app.rag.models import EvidenceType, EvidenceUnit, SourceKind


PAPER_EVIDENCE_COLLECTION = "paper_evidence"


@dataclass(frozen=True)
class VectorCandidate:
    item_id: str
    text: str
    metadata: dict[str, Any]
    distance: float | None
    score: float


class PaperEvidenceIndex:
    def __init__(self, db: ChromaDBClient | None = None) -> None:
        self.db = db or ChromaDBClient()

    def replace_document(
        self,
        project_id: str,
        document_id: str,
        units: Sequence[EvidenceUnit],
    ) -> int:
        where = {"$and": [{"project_id": project_id}, {"document_id": document_id}]}
        self.db.delete_where(PAPER_EVIDENCE_COLLECTION, where)
        indexable = [
            unit
            for unit in units
            if unit.index_text.strip() and unit.source_kind is not SourceKind.STUDENT_ANNOTATION
        ]
        for batch in _batches(indexable, 128):
            self.db.upsert(
                PAPER_EVIDENCE_COLLECTION,
                documents=[unit.index_text for unit in batch],
                metadatas=[_evidence_metadata(unit) for unit in batch],
                ids=[unit.evidence_id for unit in batch],
            )
        return len(indexable)

    def search(
        self,
        project_id: str,
        query: str,
        limit: int = 30,
        *,
        document_ids: Sequence[str] | None = None,
        evidence_types: set[EvidenceType] | None = None,
        consumer: str | None = None,
    ) -> list[VectorCandidate]:
        if not project_id or not query.strip():
            return []
        clauses: list[dict[str, Any]] = [{"project_id": project_id}]
        if document_ids:
            clauses.append({"document_id": {"$in": list(document_ids)}})
        if evidence_types:
            clauses.append({"element_type": {"$in": [item.value for item in evidence_types]}})
        where = clauses[0] if len(clauses) == 1 else {"$and": clauses}
        with observe_operation(
            "embedding.query",
            subsystem="embedding",
            consumer=consumer,
            attributes={"collection_role": "paper_evidence"},
        ) as op:
            embedding = self.db.embedder.embed([query])[0]
            op.add_count("query_chars", len(query))
        rows = self.db.query_raw(
            PAPER_EVIDENCE_COLLECTION,
            embedding,
            n_results=limit,
            where=where,
            consumer=consumer,
            raise_on_failure=True,
        )
        return [_candidate(row) for row in rows]

    def delete_document(self, project_id: str, document_id: str) -> None:
        self.db.delete_where(
            PAPER_EVIDENCE_COLLECTION,
            {"$and": [{"project_id": project_id}, {"document_id": document_id}]},
        )

    def delete_project(self, project_id: str) -> None:
        self.db.delete_where(PAPER_EVIDENCE_COLLECTION, {"project_id": project_id})


def _candidate(row: dict[str, Any]) -> VectorCandidate:
    distance = row.get("distance")
    return VectorCandidate(
        item_id=str(row["id"]),
        text=str(row.get("text") or ""),
        metadata=dict(row.get("metadata") or {}),
        distance=float(distance) if distance is not None else None,
        score=_distance_score(distance),
    )


def _distance_score(distance: Any) -> float:
    if distance is None:
        return 0.0
    value = max(0.0, float(distance))
    return 1.0 / (1.0 + value)


def _evidence_metadata(unit: EvidenceUnit) -> dict[str, Any]:
    return {
        "project_id": unit.project_id,
        "document_id": unit.document_id,
        "evidence_id": unit.evidence_id,
        "element_type": unit.element_type.value,
        "page_start": unit.page_start,
        "page_end": unit.page_end,
        "parent_id": unit.parent_id or "",
        "section_path": " > ".join(unit.section_path),
        "source_kind": unit.source_kind.value,
        "bbox_json": json.dumps(unit.bbox_norm.rounded(), separators=(",", ":")) if unit.bbox_norm else "",
    }


def _batches(items: Sequence[Any], size: int) -> Iterable[Sequence[Any]]:
    for start in range(0, len(items), size):
        yield items[start : start + size]