"""
Insta-AutoApp — OEM Manual Ingestion Pipeline

Converts the 2023 Ford Bronco Owner's Manual (PDF) into a FAISS vector index
for semantic retrieval. This script runs ONCE before the app can be used.

Usage:
    1. Place the PDF in data/
    2. Run: python ingest.py
    3. Output: data/index.faiss + data/index.pkl
"""

import logging
import os
import pickle
import sys
import time

import faiss
import fitz  # PyMuPDF
import numpy as np
from sentence_transformers import SentenceTransformer

from config import (
    MANUAL_PDF_PATH, MANUAL_PDF_FILENAME,
    FAISS_INDEX_PATH, FAISS_DOCSTORE_PATH,
    EMBEDDING_MODEL, CHUNK_SIZE, CHUNK_OVERLAP,
)

logging.basicConfig(level=logging.INFO, format="%(asctime)s - %(levelname)s - %(message)s")
logger = logging.getLogger(__name__)


# ── Low-value content filter ─────────────────────────────────────────

LOW_VALUE_MARKERS = [
    "table of contents", "all rights reserved", "edition date",
    "visual search", "copyright", "printed in",
]


def is_low_value(text: str) -> bool:
    """Filter out TOC, copyright, legal, and navigation-only pages."""
    lowered = text.lower().strip()
    if len(lowered) < 50:
        return True
    if any(marker in lowered for marker in LOW_VALUE_MARKERS):
        dots_ratio = lowered.count(".") / max(len(lowered), 1)
        if dots_ratio > 0.05:
            return True
    if lowered.count("copyright") > 0 and len(lowered) < 300:
        return True
    return False


# ── Chunking ─────────────────────────────────────────────────────────

def chunk_text(text: str, page_num: int, chunk_size: int = CHUNK_SIZE, overlap: int = CHUNK_OVERLAP) -> list:
    """Split text into overlapping chunks with page metadata."""
    words = text.split()
    chunks = []
    start = 0
    while start < len(words):
        end = start + chunk_size
        chunk_text = " ".join(words[start:end])
        if len(chunk_text.strip()) > 30:
            chunks.append({
                "text": chunk_text.strip(),
                "page": page_num,
                "source": MANUAL_PDF_FILENAME,
            })
        start += chunk_size - overlap
    return chunks


# ── Main pipeline ────────────────────────────────────────────────────

def main():
    logger.info("=" * 60)
    logger.info("Insta-AutoApp — FAISS Index Builder")
    logger.info("=" * 60)

    # Check PDF exists
    if not os.path.exists(MANUAL_PDF_PATH):
        logger.error(
            f"PDF not found: {MANUAL_PDF_PATH}\n"
            f"Please place '{MANUAL_PDF_FILENAME}' in the data/ directory."
        )
        sys.exit(1)

    # Step 1: Extract text from PDF
    logger.info(f"Loading PDF: {MANUAL_PDF_PATH}")
    doc = fitz.open(MANUAL_PDF_PATH)
    logger.info(f"PDF loaded: {len(doc)} pages")

    # Step 2: Extract and filter pages
    all_chunks = []
    pages_kept = 0
    pages_skipped = 0
    for page_num in range(len(doc)):
        page = doc[page_num]
        text = page.get_text()
        if is_low_value(text):
            pages_skipped += 1
            continue
        pages_kept += 1
        page_chunks = chunk_text(text, page_num + 1)
        all_chunks.extend(page_chunks)

    doc.close()
    logger.info(f"Pages processed: {pages_kept} kept, {pages_skipped} filtered out")
    logger.info(f"Chunks created: {len(all_chunks)}")

    if not all_chunks:
        logger.error("No chunks were created. Check the PDF file.")
        sys.exit(1)

    # Step 3: Embed chunks
    logger.info(f"Loading embedding model: {EMBEDDING_MODEL}")
    embedder = SentenceTransformer(EMBEDDING_MODEL)

    logger.info("Embedding chunks (this may take 1-3 minutes)...")
    start_time = time.time()
    texts = [c["text"] for c in all_chunks]
    embeddings = embedder.encode(texts, show_progress_bar=True, normalize_embeddings=True)
    embeddings = np.array(embeddings, dtype=np.float32)
    elapsed = time.time() - start_time
    logger.info(f"Embedding complete: {embeddings.shape[0]} vectors, {embeddings.shape[1]} dimensions ({elapsed:.1f}s)")

    # Step 4: Build FAISS index
    logger.info("Building FAISS index...")
    dimension = embeddings.shape[1]
    index = faiss.IndexFlatIP(dimension)  # Inner product (cosine sim with normalized vecs)
    index.add(embeddings)
    logger.info(f"FAISS index built: {index.ntotal} vectors")

    # Step 5: Save to disk
    out_dir = os.path.dirname(FAISS_INDEX_PATH)
    if out_dir:
        os.makedirs(out_dir, exist_ok=True)
    faiss.write_index(index, FAISS_INDEX_PATH)
    with open(FAISS_DOCSTORE_PATH, "wb") as f:
        pickle.dump(all_chunks, f)

    logger.info(f"Index saved: {FAISS_INDEX_PATH}")
    logger.info(f"Metadata saved: {FAISS_DOCSTORE_PATH}")
    logger.info("=" * 60)
    logger.info("DONE. You can now run: python app.py")
    logger.info("=" * 60)


if __name__ == "__main__":
    main()