from __future__ import annotations

from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session, joinedload, subqueryload

from app.core.dependencies import get_current_user
from app.database.session import get_db
from app.models.knowledge_item import KnowledgeItem, KnowledgeStatus, KnowledgeType
from app.models.user import User
from app.models.workspace import Workspace


router = APIRouter(
    prefix="/knowledge",
    tags=["Knowledge"],
)


def _knowledge_response(item: KnowledgeItem) -> dict:
    dv = item.document_version
    evidence_list = []
    for ev in (item.evidence or []):
        evidence_list.append({
            "quote": ev.quote,
            "page_number": ev.page_number,
            "section": ev.section,
            "confidence": ev.confidence,
            "source_type": ev.source_type,
        })

    # Include the most recent proposal info for governance context
    proposal_info = None
    if item.proposals:
        # Get the most recent proposal (by created_at or just first)
        latest_proposal = sorted(
            item.proposals,
            key=lambda p: p.created_at or "",
            reverse=True,
        )[0]
        proposal_info = {
            "id": str(latest_proposal.id),
            "status": latest_proposal.status.value,
            "proposal_type": latest_proposal.proposal_type.value,
        }

    return {
        "id": str(item.id),
        "workspace_id": str(item.workspace_id),
        "document_version_id": str(item.document_version_id),
        "filename": dv.filename if dv else None,
        "type": item.type.value,
        "title": item.title,
        "value": item.value,
        "summary": item.summary,
        "attributes": item.attributes,
        "confidence": item.confidence,
        "status": item.status.value,
        "proposal": proposal_info,
        "evidence": evidence_list,
        "created_at": item.created_at,
        "updated_at": item.updated_at,
    }


@router.get("")
def list_knowledge(
    workspace_id: UUID,
    status: str | None = None,
    type: str | None = None,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db),
):
    workspace = (
        db.query(Workspace)
        .filter(
            Workspace.id == workspace_id,
            Workspace.created_by == current_user.id,
        )
        .first()
    )
    if workspace is None:
        raise HTTPException(
            status_code=403,
            detail="You do not have access to this workspace.",
        )

    query = db.query(KnowledgeItem).filter(
        KnowledgeItem.workspace_id == workspace_id,
    )

    if status:
        status_upper = status.upper()

        # Special case: "ARCHIVED" means knowledge items whose proposal
        # has been archived or the knowledge item itself is marked ARCHIVED.
        if status_upper == "ARCHIVED":
            from app.models.proposal import Proposal, ProposalStatus
            from sqlalchemy import select
            archived_ki_ids = (
                select(Proposal.knowledge_item_id)
                .filter(
                    Proposal.knowledge_item_id.isnot(None),
                    Proposal.status == ProposalStatus.ARCHIVED,
                )
            )
            query = query.filter(
                (KnowledgeItem.status == KnowledgeStatus.ARCHIVED)
                | KnowledgeItem.id.in_(archived_ki_ids)
            )
        elif status_upper == "PENDING":
            # PENDING means genuinely untouched — PENDING knowledge with
            # a PENDING proposal (not archived, not decided).
            from app.models.proposal import Proposal, ProposalStatus
            from sqlalchemy import select
            archived_or_rejected_ki_ids = (
                select(Proposal.knowledge_item_id)
                .filter(
                    Proposal.knowledge_item_id.isnot(None),
                    Proposal.status.in_([ProposalStatus.ARCHIVED, ProposalStatus.REJECTED]),
                )
            )
            query = query.filter(
                KnowledgeItem.status == KnowledgeStatus.PENDING,
                ~KnowledgeItem.id.in_(archived_or_rejected_ki_ids),
            )
        else:
            try:
                ks = KnowledgeStatus(status_upper)
                query = query.filter(KnowledgeItem.status == ks)
            except ValueError:
                pass

    if type:
        try:
            kt = KnowledgeType(type.upper())
            query = query.filter(KnowledgeItem.type == kt)
        except ValueError:
            pass

    items = (
        query
        .options(
            joinedload(KnowledgeItem.document_version),   # 1 JOIN — gets filename
            subqueryload(KnowledgeItem.evidence),          # 1 extra query for all evidence
            subqueryload(KnowledgeItem.proposals),         # 1 extra query for all proposals
        )
        .order_by(KnowledgeItem.created_at.desc())
        .limit(200)
        .all()
    )
    return [_knowledge_response(i) for i in items]


@router.get("/search")
def search_knowledge(
    workspace_id: UUID,
    q: str,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db),
):
    """
    Hybrid search: lexical (ILIKE) + vector (pgvector cosine similarity),
    merged with Reciprocal Rank Fusion (RRF).
    """
    workspace = (
        db.query(Workspace)
        .filter(
            Workspace.id == workspace_id,
            Workspace.created_by == current_user.id,
        )
        .first()
    )
    if workspace is None:
        raise HTTPException(
            status_code=403,
            detail="You do not have access to this workspace.",
        )

    # --- Lexical search (substring match on title/value/summary) ---
    lexical_items = (
        db.query(KnowledgeItem)
        .options(
            joinedload(KnowledgeItem.document_version),
            subqueryload(KnowledgeItem.evidence),
            subqueryload(KnowledgeItem.proposals),
        )
        .filter(
            KnowledgeItem.workspace_id == workspace_id,
            (
                KnowledgeItem.title.ilike(f"%{q}%")
                | KnowledgeItem.value.ilike(f"%{q}%")
                | KnowledgeItem.summary.ilike(f"%{q}%")
            ),
        )
        .order_by(KnowledgeItem.created_at.desc())
        .limit(30)
        .all()
    )

    # --- Vector search (embed query, find nearest chunks, map to knowledge items) ---
    vector_items = []
    try:
        from app.services.embedding_service import EmbeddingService
        from app.models.document_chunk import DocumentChunk
        from app.models.document_version import DocumentVersion

        embedding_service = EmbeddingService()
        query_embedding = embedding_service.embed(q)

        if query_embedding:
            # Find nearest chunks in this workspace's documents
            nearest_chunks = (
                db.query(DocumentChunk)
                .join(DocumentVersion, DocumentChunk.document_version_id == DocumentVersion.id)
                .filter(
                    DocumentVersion.document.has(workspace_id=workspace_id),
                    DocumentChunk.embedding.isnot(None),
                )
                .order_by(DocumentChunk.embedding.cosine_distance(query_embedding))
                .limit(20)
                .all()
            )

            # Map chunks to knowledge items via document_version_id
            if nearest_chunks:
                version_ids = list({c.document_version_id for c in nearest_chunks})
                vector_items = (
                    db.query(KnowledgeItem)
                    .options(
                        joinedload(KnowledgeItem.document_version),
                        subqueryload(KnowledgeItem.evidence),
                        subqueryload(KnowledgeItem.proposals),
                    )
                    .filter(
                        KnowledgeItem.workspace_id == workspace_id,
                        KnowledgeItem.document_version_id.in_(version_ids),
                    )
                    .limit(30)
                    .all()
                )
    except Exception:
        # If vector search fails (model not loaded, etc.), fall back to lexical only
        pass

    # --- RRF merge (Reciprocal Rank Fusion, k=60) ---
    k = 60
    scores: dict[str, float] = {}
    item_map: dict[str, KnowledgeItem] = {}

    # Score lexical results
    for rank, item in enumerate(lexical_items):
        item_id = str(item.id)
        scores[item_id] = scores.get(item_id, 0) + 1.0 / (k + rank + 1)
        item_map[item_id] = item

    # Score vector results
    for rank, item in enumerate(vector_items):
        item_id = str(item.id)
        scores[item_id] = scores.get(item_id, 0) + 1.0 / (k + rank + 1)
        item_map[item_id] = item

    # Sort by RRF score descending
    ranked_ids = sorted(scores.keys(), key=lambda x: scores[x], reverse=True)

    results = [item_map[item_id] for item_id in ranked_ids[:30]]
    return [_knowledge_response(i) for i in results]


@router.get("/{item_id}")
def get_knowledge_item(
    item_id: UUID,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db),
):
    from app.models.proposal import Proposal
    from app.models.review import Review
    from app.models.commit import Commit

    item = db.query(KnowledgeItem).filter(KnowledgeItem.id == item_id).first()
    if item is None:
        raise HTTPException(status_code=404, detail="Knowledge item not found.")

    workspace = (
        db.query(Workspace)
        .filter(
            Workspace.id == item.workspace_id,
            Workspace.created_by == current_user.id,
        )
        .first()
    )
    if workspace is None:
        raise HTTPException(status_code=403, detail="You do not have access to this item.")

    # Get proposals related to this knowledge item
    proposals = (
        db.query(Proposal)
        .filter(Proposal.knowledge_item_id == item_id)
        .order_by(Proposal.created_at.desc())
        .all()
    )

    history = []
    for p in proposals:
        entry = {
            "type": "proposal",
            "proposal_id": str(p.id),
            "proposal_type": p.proposal_type.value,
            "status": p.status.value,
            "summary": p.summary,
            "timestamp": p.created_at.isoformat() if p.created_at else None,
        }
        history.append(entry)

        # If proposal was reviewed, add the review event
        if p.reviewed_at:
            history.append({
                "type": "decision",
                "proposal_id": str(p.id),
                "status": p.status.value,
                "timestamp": p.reviewed_at.isoformat(),
            })

        # If approved, find the commit
        if p.status.value == "APPROVED":
            commit = (
                db.query(Commit)
                .filter(Commit.proposal_id == p.id)
                .first()
            )
            if commit:
                history.append({
                    "type": "commit",
                    "commit_id": str(commit.id),
                    "message": commit.message,
                    "timestamp": commit.committed_at.isoformat() if commit.committed_at else None,
                })

    # Sort history by timestamp
    history.sort(key=lambda h: h.get("timestamp") or "", reverse=True)

    resp = _knowledge_response(item)
    resp["history"] = history
    return resp