app.py

import os, pickle, json, gradio as gr
import numpy as np, faiss
from sentence_transformers import SentenceTransformer

# ---------- Optional LLM (OpenAI) ----------
OPENAI_API_KEY = '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'  # add in Space -> Settings -> Secrets
USE_OPENAI = bool(OPENAI_API_KEY)
if USE_OPENAI:
    try:
        from openai import OpenAI
        oai = OpenAI(api_key=OPENAI_API_KEY)
        OPENAI_MODEL = os.getenv("OPENAI_MODEL", "gpt-4o-mini")
    except Exception as e:
        print("[RAG] OpenAI not available:", e)
        USE_OPENAI = False

# ---------- Artifacts you already have ----------
FAISS_PATH = os.getenv("FAISS_PATH", "squad_v2.faiss")
META_PATH  = os.getenv("META_PATH",  "squad_v2_meta.pkl")

CACHE = {
    "index": None,
    "contexts": None,
    "encoder": None,
    "model_name": None
}

def _coerce_text_list(x):
    """Accepts list[str] or list[dict]; extracts text nicely."""
    out = []
    if isinstance(x, list):
        for it in x:
            if isinstance(it, str):
                out.append(it)
            elif isinstance(it, dict):
                # common keys people use
                text = it.get("text") or it.get("content") or it.get("ctx") or ""
                if text:
                    out.append(text)
    return out

def load_artifacts():
    if CACHE["index"] is not None:
        return

    # 1) FAISS
    if not os.path.exists(FAISS_PATH):
        raise FileNotFoundError(f"Missing FAISS index: {FAISS_PATH}")
    index = faiss.read_index(FAISS_PATH)

    # 2) META
    if not os.path.exists(META_PATH):
        raise FileNotFoundError(f"Missing meta file: {META_PATH}")
    with open(META_PATH, "rb") as f:
        meta = pickle.load(f)

    # parse meta
    model_name = "all-MiniLM-L6-v2"
    contexts = None

    if isinstance(meta, dict):
        # common keys
        model_name = meta.get("model") or meta.get("encoder") or model_name
        contexts = (
            meta.get("contexts")
            or meta.get("texts")
            or meta.get("documents")
            or meta.get("corpus")
        )
    else:
        # meta is just a list of contexts
        contexts = meta

    # normalize contexts
    contexts = _coerce_text_list(contexts) if contexts is not None else []
    if not contexts:
        raise ValueError("No contexts found in meta; expected a list of texts.")

    # Align lengths (safeguard)
    ntotal = index.ntotal
    if ntotal != len(contexts):
        m = min(ntotal, len(contexts))
        print(f"[RAG] WARNING: index.ntotal({ntotal}) != contexts({len(contexts)}). Trimming to {m}.")
        # We can’t resize FAISS easily here; instead trim contexts so we never index out of range.
        contexts = contexts[:m]

    # 3) load encoder (lazy; we instantiate now to avoid first-click delay)
    encoder = SentenceTransformer(model_name)

    CACHE.update(index=index, contexts=contexts, encoder=encoder, model_name=model_name)
    print(f"[RAG] Loaded index={FAISS_PATH} (ntotal={CACHE['index'].ntotal}), "
          f"contexts={len(CACHE['contexts'])}, model={CACHE['model_name']}")

def _retrieve(question: str, k: int):
    # encode query; FAISS expects float32
    q_emb = CACHE["encoder"].encode([question]).astype("float32")
    D, I = CACHE["index"].search(q_emb, int(k))
    idxs = I[0].tolist()
    dists = D[0].tolist()
    # guard for any out-of-range due to mismatched sizes
    max_ok = len(CACHE["contexts"]) - 1
    pairs = []
    for j, dist in zip(idxs, dists):
        if 0 <= j <= max_ok:
            pairs.append((j, dist, CACHE["contexts"][j]))
    return pairs

def _build_prompt(question: str, pairs):
    chunks = []
    for i, (_, _d, ctx) in enumerate(pairs, start=1):
        # keep prompt size reasonable
        ctx_short = ctx.strip()
        if len(ctx_short) > 1200:
            ctx_short = ctx_short[:1200] + "..."
        chunks.append(f"[Source {i}] {ctx_short}")
    context_block = "\n\n".join(chunks) if chunks else "(no context)"
    prompt = f"""Answer strictly from the context below. If not answerable, say so.
Include [Source X] citations in your answer.

Context:
{context_block}

Question: {question}
Answer:"""
    return prompt

def answer(question: str, k: int):
    if not question.strip():
        return "Please enter a question.", [], None

    pairs = _retrieve(question, k)
    if not pairs:
        return "No results found in the index.", [], None

    # Build citations list for UI
    citations = [{"rank": i+1, "faiss_dist": round(d, 4), "snippet": ctx[:240] + ("..." if len(ctx) > 240 else "")}
                 for i, (_idx, d, ctx) in enumerate(pairs)]

    if USE_OPENAI:
        prompt = _build_prompt(question, pairs)
        try:
            resp = oai.chat.completions.create(
                model=OPENAI_MODEL,
                messages=[{"role":"user","content":prompt}],
                temperature=0.2
            )
            ans = resp.choices[0].message.content
        except Exception as e:
            ans = f"LLM call failed: {e}\n\nTop results shown below."
    else:
        # Fallback: show top-1 context as the “answer”
        ans = ("(No OPENAI_API_KEY set — showing most relevant context instead.)\n\n" +
               pairs[0][2][:1200])

    # simple JSON for debugging/export
    raw = {
        "k": int(k),
        "answer": ans,
        "citations": citations
    }
    return ans, citations, json.dumps(raw, indent=2)

# ---------- UI ----------
with gr.Blocks(theme=gr.themes.Soft()) as demo:
    gr.Markdown("## Nyxion Labs · Grounded Q&A (SQuAD v2, FAISS)")

    with gr.Row():
        q = gr.Textbox(label="Ask a question", placeholder="e.g., What is the capital of France?")
        k = gr.Slider(1, 10, value=3, step=1, label="Citations (top-k)")

    run_btn = gr.Button("Ask")
    ans_md  = gr.Markdown(label="Answer")
    cites   = gr.Dataframe(headers=["rank","faiss_dist","snippet"], datatype=["number","number","str"],
                           row_count=(0,"dynamic"), label="Retrieved contexts")
    raw_json = gr.JSON(label="Debug / raw response")

    def _startup():
        load_artifacts()
        return "Ready."

    status = gr.Markdown()
    demo.load(_startup, inputs=None, outputs=status)
    run_btn.click(answer, [q, k], [ans_md, cites, raw_json])

if __name__ == "__main__":
    load_artifacts()
    demo.launch()