# model_utils.py
from typing import List, Optional
import re

import os
import numpy as np
import torch
from transformers import AutoTokenizer, AutoModelForCausalLM
from sentence_transformers import SentenceTransformer
from sentence_transformers.util import cos_sim

import qa_store
from loader import (
    load_curriculum, 
    load_manual_qa, 
    rebuild_combined_qa, 
    load_glossary, 
    sync_download_manual_qa,  # <--- Import it
    sync_download_cache,     # <--- Add this import
    sync_upload_cache,       # <--- Add this import
    CACHE_PATH               # <--- Add this import
)

# -----------------------------
# Base chat model
# -----------------------------
MODEL_NAME = "SeaLLMs/SeaLLMs-v3-1.5B-Chat"
EMBED_MODEL_NAME = "sentence-transformers/paraphrase-multilingual-MiniLM-L12-v2"

BASE_DIR = os.path.dirname(os.path.abspath(__file__))
CACHE_FILE = os.path.join(BASE_DIR, "data", "cached_embeddings.pt")

device = "cuda" if torch.cuda.is_available() else "cpu"

tokenizer = AutoTokenizer.from_pretrained(MODEL_NAME)
# Use float16 on GPU to save memory, float32 on CPU
dtype = torch.float16 if torch.cuda.is_available() else torch.float32
model = AutoModelForCausalLM.from_pretrained(MODEL_NAME, torch_dtype=dtype)
model.to(device)
model.eval()

embed_model = SentenceTransformer(EMBED_MODEL_NAME)
embed_model = embed_model.to(device)

# Number of textbook entries to include in the RAG context
MAX_CONTEXT_ENTRIES = 4


# -----------------------------
# Embedding builders
# -----------------------------

# 👇👇👇 ADD THIS NEW FUNCTION 👇👇👇
def admin_force_rebuild_cache() -> str:
    """
    Forcedly re-calculate all embeddings and upload to cloud.
    Triggered by Teacher Panel button.
    """
    status_msg = []
    
    # 1. Compute Textbook
    print("[ADMIN] Rebuilding Textbook Embeddings...")
    texts = []
    for e in qa_store.ENTRIES:
        chapter = e.get("chapter_title", "") or ""
        section = e.get("section_title", "") or ""
        text = e.get("text", "") or ""
        texts.append(f"{chapter}\n{section}\n{text}")
    
    if texts:
        qa_store.TEXT_EMBEDDINGS = embed_model.encode(texts, convert_to_tensor=True)
        status_msg.append(f"✅ Textbook ({len(texts)})")

    # 2. Compute Glossary
    print("[ADMIN] Rebuilding Glossary Embeddings...")
    gloss_texts = [f"{i.get('term')} :: {i.get('definition')}" for i in qa_store.GLOSSARY]
    
    if gloss_texts:
        qa_store.GLOSSARY_EMBEDDINGS = embed_model.encode(
            gloss_texts, convert_to_numpy=True, normalize_embeddings=True
        )
        status_msg.append(f"✅ Glossary ({len(gloss_texts)})")

    # 3. Save to Disk
    print("[ADMIN] Saving to disk...")
    torch.save({
        "textbook": qa_store.TEXT_EMBEDDINGS,
        "glossary": qa_store.GLOSSARY_EMBEDDINGS
    }, CACHE_PATH)

    # 4. Upload to Cloud
    upload_status = sync_upload_cache()
    return f"Rebuild Complete: {', '.join(status_msg)} | {upload_status}"

def _build_entry_embeddings() -> None:
    """
    Load pre-computed embeddings if available, otherwise build them.
    """
    if not getattr(qa_store, "ENTRIES", None):
        qa_store.TEXT_EMBEDDINGS = None
        return

    # 1. Try Loading from Cache
    if os.path.exists(CACHE_FILE):
        try:
            print(f"[INFO] Loading cached embeddings from {CACHE_FILE}...")
            cache = torch.load(CACHE_FILE, map_location=device)
            if "textbook" in cache and cache["textbook"] is not None:
                # Validate size matches
                if len(cache["textbook"]) == len(qa_store.ENTRIES):
                    qa_store.TEXT_EMBEDDINGS = cache["textbook"].to(device)
                    print("[INFO] Textbook embeddings loaded successfully.")
                    return
                else:
                    print("[WARN] Cache size mismatch (Data changed?). Re-computing...")
        except Exception as e:
            print(f"[WARN] Failed to load cache: {e}")

    # 2. Fallback: Compute from scratch (The old slow way)
    print("[INFO] Computing textbook embeddings from scratch...")
    texts: List[str] = []
    for e in qa_store.ENTRIES:
        chapter = e.get("chapter_title", "") or e.get("chapter", "") or ""
        section = e.get("section_title", "") or e.get("section", "") or ""
        text = e.get("text", "") or ""
        combined = f"{chapter}\n{section}\n{text}"
        texts.append(combined)

    qa_store.TEXT_EMBEDDINGS = embed_model.encode(
        texts,
        convert_to_tensor=True,
        show_progress_bar=False,
    )


def _build_glossary_embeddings() -> None:
    """Create embeddings for glossary terms + definitions."""
    if not getattr(qa_store, "GLOSSARY", None):
        qa_store.GLOSSARY_EMBEDDINGS = None
        print("[INFO] No glossary terms to embed.")
        return

    # Embed term + definition together
    texts = [
        f"{item.get('term', '')} :: {item.get('definition', '')}"
        for item in qa_store.GLOSSARY
    ]

    embeddings = embed_model.encode(
        texts,
        convert_to_numpy=True,
        normalize_embeddings=True,
    )
    qa_store.GLOSSARY_EMBEDDINGS = embeddings
    print(f"[INFO] Built glossary embeddings for {len(texts)} terms.")


# -----------------------------
# Load data once at import time
# -----------------------------
sync_download_manual_qa()
sync_download_cache()        # <--- Add this line!
load_curriculum()
load_manual_qa()
load_glossary()
rebuild_combined_qa()
_build_entry_embeddings()
_build_glossary_embeddings()

# -----------------------------
# System prompt (Natural Science)
# -----------------------------
SYSTEM_PROMPT = (
    "ທ່ານແມ່ນຜູ້ຊ່ວຍເຫຼືອດ້ານວິທະຍາສາດທໍາມະຊາດ "
    "ສໍາລັບນັກຮຽນຊັ້ນ ມ.1-ມ.4. "
    "ຕອບແຕ່ພາສາລາວ ໃຫ້ຕອບສັ້ນໆ 2–3 ປະໂຫຍກ ແລະເຂົ້າໃຈງ່າຍ. "
    "ໃຫ້ອີງຈາກຂໍ້ມູນອ້າງອີງຂ້າງລຸ່ມນີ້ເທົ່ານັ້ນ. "
    "ຖ້າຂໍ້ມູນບໍ່ພຽງພໍ ຫຼືບໍ່ຊັດເຈນ ໃຫ້ບອກວ່າບໍ່ແນ່ໃຈ."
)


# -----------------------------
# Helper: history formatting
# -----------------------------
def _format_history(history: Optional[List]) -> str:
    """
    Convert last few chat turns into a Lao conversation snippet
    to give the model context for follow-up questions.
    Gradio history format: [[user_msg, bot_msg], [user_msg, bot_msg], ...]
    """
    if not history:
        return ""

    # keep only the last 3 turns to avoid very long prompts
    recent = history[-3:]

    lines: List[str] = []
    for turn in recent:
        if not isinstance(turn, (list, tuple)) or len(turn) != 2:
            continue
        user_msg, bot_msg = turn
        lines.append(f"ນັກຮຽນ: {user_msg}")
        lines.append(f"ອາຈານ AI: {bot_msg}")

    if not lines:
        return ""

    joined = "\n".join(lines) + "\n\n"
    return joined


# -----------------------------
# RAG: retrieve textbook context
# -----------------------------
def retrieve_context(question: str, max_entries: int = MAX_CONTEXT_ENTRIES) -> str:
    """
    Embedding-based retrieval over textbook entries.
    Falls back to concatenated raw knowledge if embeddings are missing.
    """
    if not getattr(qa_store, "ENTRIES", None):
        # Fallback: raw knowledge (if available) or empty string
        return getattr(qa_store, "RAW_KNOWLEDGE", "")

    if qa_store.TEXT_EMBEDDINGS is None:
        top_entries = qa_store.ENTRIES[:max_entries]
    else:
        # 1) Encode the question
        q_vec = embed_model.encode(
            question,
            convert_to_tensor=True,
            show_progress_bar=False,
        )

        # 2) Cosine similarity with all entry embeddings
        sims = cos_sim(q_vec, qa_store.TEXT_EMBEDDINGS)[0]  # shape [N]

        # 3) Take top-k
        top_indices = torch.topk(sims, k=min(max_entries, sims.shape[0])).indices
        top_entries = [qa_store.ENTRIES[i] for i in top_indices.tolist()]

    # Build context string for the prompt
    context_blocks: List[str] = []
    for e in top_entries:
        header = (
            f"[ຊັ້ນ {e.get('grade','')}, "
            f"ໜ່ວຍ {e.get('unit','')}, "
            f"ບົດ {e.get('chapter_title','')}, "
            f"ຫົວຂໍ້ {e.get('section_title','')}]"
        )
        context_blocks.append(f"{header}\n{e.get('text','')}")

    return "\n\n".join(context_blocks)


# -----------------------------
# Glossary-based answering
# -----------------------------

def normalize_lao_text(text: str) -> str:
    """
    Clean Lao text for accurate matching.
    Removes punctuation and extra spaces.
    """
    if not text: 
        return ""
    
    # 1. Lowercase
    text = text.lower().strip()
    
    # 2. Remove punctuation (Using the safe single-quote format)
    text = re.sub(r'[?.!,;։:\'\""“”‘’]', "", text)
    
    # 3. Collapse multiple spaces into one (THIS WAS MISSING)
    text = re.sub(r"\s+", " ", text)
    
    return text.strip()

def answer_from_glossary(message: str) -> Optional[str]:
    """
    Try to answer using the glossary index.
    Tier 1: Exact/Substring match (Sorted by Length to fix overlap bugs).
    Tier 2: Vector embedding match (Fallback).
    """
    if not getattr(qa_store, "GLOSSARY", None):
        return None

    norm_msg = normalize_lao_text(message)
    
    # --- FIX START: Sort by Length + Exact Match ---
    
    # 1. Sort glossary terms by length (Longest first) 
    # This ensures we match "ນັກວິທະຍາສາດ" (14 chars) BEFORE "ວິທະຍາສາດ" (11 chars)
    sorted_glossary = sorted(
        qa_store.GLOSSARY, 
        key=lambda x: len(normalize_lao_text(x.get("term", ""))), 
        reverse=True
    )

    for item in sorted_glossary:
        term_raw = item.get("term", "")
        norm_term = normalize_lao_text(term_raw)
        
        if not norm_term:
            continue

        # Condition A: EXACT Match (Perfect precision) 
        # Example: User types "ນັກວິທະຍາສາດ"
        is_exact = (norm_msg == norm_term)
        
        # Condition B: Substring Match (High precision for questions)
        # Example: User types "ນັກວິທະຍາສາດ ແມ່ນຫຍັງ"
        # We enforce a length check so "Science" doesn't match a huge paragraph about Pollution.
        is_substring = (norm_term in norm_msg) and (len(norm_msg) < len(norm_term) + 20)

        if is_exact or is_substring:
            definition = item.get("definition", "").strip()
            example = item.get("example", "").strip()
            
            # Return the result immediately once the longest match is found
            if example:
                return f"{definition} ຕົວຢ່າງ: {example}"
            return definition
            
    # --- FIX END ---

    # If no text match, proceed to Vector Similarity (Tier 2)
    if qa_store.GLOSSARY_EMBEDDINGS is None:
        return None

    q_emb = embed_model.encode(
        [message],
        convert_to_numpy=True,
        normalize_embeddings=True,
    )[0]

    sims = np.dot(qa_store.GLOSSARY_EMBEDDINGS, q_emb)
    best_idx = int(np.argmax(sims))
    best_sim = float(sims[best_idx])

    # Threshold 0.65 to prevent weak matches
    if best_sim < 0.65: 
        return None

    item = qa_store.GLOSSARY[best_idx]
    definition = item.get("definition", "").strip()
    example = item.get("example", "").strip()

    if example:
        return f"{definition} ຕົວຢ່າງ: {example}"
    return definition


# -----------------------------
# Prompt + LLM generation
# -----------------------------
def build_prompt(question: str, history: Optional[List] = None) -> str:
    context = retrieve_context(question, max_entries=MAX_CONTEXT_ENTRIES)
    history_block = _format_history(history)

    return f"""{SYSTEM_PROMPT}

{history_block}ຂໍ້ມູນອ້າງອີງ:
{context}

ຄຳຖາມ: {question}

ຄຳຕອບດ້ວຍພາສາລາວ:"""


def generate_answer(question: str, history: Optional[List] = None) -> str:
    prompt = build_prompt(question, history)
    inputs = tokenizer(prompt, return_tensors="pt").to(device)

    with torch.no_grad():
        outputs = model.generate(
            **inputs,
            max_new_tokens=160,
            do_sample=False,
        )

    generated_ids = outputs[0][inputs["input_ids"].shape[1]:]
    answer = tokenizer.decode(generated_ids, skip_special_tokens=True).strip()

    # Enforce 2–3 sentence answers for students
    sentences = re.split(r"(?<=[\.?!…])\s+", answer)
    short_answer = " ".join(sentences[:3]).strip()
    return short_answer if short_answer else answer


# -----------------------------
# QA lookup (exact + fuzzy)
# -----------------------------
def answer_from_qa(question: str) -> Optional[str]:
    """
    1) Exact match in QA_INDEX
    2) Fuzzy match via word overlap with ALL_QA_KNOWLEDGE
    """
    norm_q = qa_store.normalize_question(question)
    if not norm_q:
        return None

    # Exact match
    if norm_q in qa_store.QA_INDEX:
        return qa_store.QA_INDEX[norm_q]

    # Fuzzy match
    q_terms = [t for t in norm_q.split(" ") if len(t) > 1]
    if not q_terms:
        return None

    best_score = 0
    best_answer: Optional[str] = None

    for item in qa_store.ALL_QA_KNOWLEDGE:
        stored_terms = [t for t in item["norm_q"].split(" ") if len(t) > 1]
        overlap = sum(1 for t in q_terms if t in stored_terms)
        if overlap > best_score:
            best_score = overlap
            best_answer = item["a"]

    # require at least 2 overlapping words to accept fuzzy match
    if best_score >= 2 and best_answer is not None:
        # optional: log when fuzzy match is used
        print(f"[FUZZY MATCH] score={best_score} -> {best_answer[:50]!r}")
        return best_answer

    return None


# -----------------------------
# Main chatbot entry
# -----------------------------
def laos_science_bot(message: str, history: List) -> str:
    """
    Main chatbot function for Student tab (Gradio ChatInterface).
    """
    if not message.strip():
        return "ກະລຸນາພິມຄໍາຖາມກ່ອນ."

    # 0) Try glossary first for key concepts
    gloss = answer_from_glossary(message)
    if gloss:
        return gloss

    # 1) Try exact / fuzzy Q&A first
    direct = answer_from_qa(message)
    if direct:
        return direct

    # 2) Fall back to LLM + retrieved context
    try:
        answer = generate_answer(message, history)
    except Exception as e:  # noqa: BLE001
        return f"ລະບົບມີບັນຫາ: {e}"

    return answer