import asyncio
import uuid

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.adventure_chunk import AdventureChunk
from app.rag.embeddings import embed_query

DEFAULT_TOP_K = 5
# Same calibration as the rulebook RAG (app/rag/retrieval.py) — see there for how these were chosen.
MAX_DISTANCE = 0.6
MAX_BLOCK_CHARS = 4000


async def build_adventure_rag_block(
    session: AsyncSession, game_id: uuid.UUID, query: str, top_k: int = DEFAULT_TOP_K
) -> str:
    # Chunk 0 (the adventure's opening) is always included alongside the similarity search:
    # on the very first turns the player's message is often just answering Session-0 questions
    # and won't necessarily be similar to the adventure's actual hook, so pure similarity search
    # could miss the beginning entirely and leave the DM to improvise instead of following it.
    opening = (
        await session.execute(
            select(AdventureChunk)
            .where(AdventureChunk.game_id == game_id, AdventureChunk.chunk_index == 0)
        )
    ).scalar_one_or_none()

    query_embedding = await asyncio.to_thread(embed_query, query)
    distance = AdventureChunk.embedding.cosine_distance(query_embedding)
    rows = (
        await session.execute(
            select(AdventureChunk, distance.label("distance"))
            .where(AdventureChunk.game_id == game_id)
            .order_by(distance)
            .limit(top_k)
        )
    ).all()

    relevant = [chunk for chunk, dist in rows if dist <= MAX_DISTANCE]
    if opening is not None and opening.id not in {c.id for c in relevant}:
        relevant.insert(0, opening)

    if not relevant:
        return ""

    parts = [
        "Auszüge aus dem vorgegebenen Abenteuer — halte dich strikt daran (siehe Systemanweisung):"
    ]
    used_chars = 0
    for chunk in relevant:
        entry = f"\n{chunk.content}"
        if used_chars + len(entry) > MAX_BLOCK_CHARS and used_chars > 0:
            break
        parts.append(entry)
        used_chars += len(entry)
    return "\n".join(parts)