"""
Script de ingesta: vectoriza los capítulos de ESL e ISLP en ChromaDB.

Uso:
    python -m rag_books_mcp.ingest --books-dir ../ebook

Esto crea/actualiza la base vectorial en ./chroma_db/
"""

import os
import re
import argparse
from pathlib import Path

import chromadb
from chromadb.utils.embedding_functions import SentenceTransformerEmbeddingFunction


# --- Configuración ---
EMBEDDING_MODEL = "all-MiniLM-L6-v2"
CHUNK_SIZE = 600  # tokens aprox (caracteres / 4)
CHUNK_OVERLAP = 100
CHROMA_DIR = Path(__file__).parent.parent / "chroma_db"

BOOKS_CONFIG = {
    "esl": {
        "dir_name": "capitulos_TheElementsOfStatisticalLearning",
        "collection": "esl_chapters",
        "full_name": "The Elements of Statistical Learning (Hastie, Tibshirani, Friedman)",
    },
    "islp": {
        "dir_name": "capitulos_islp",
        "collection": "islp_chapters",
        "full_name": "An Introduction to Statistical Learning with Python (James, Witten, Hastie, Tibshirani)",
    },
    "fes": {
        "dir_name": "capitulos_fes",
        "collection": "fes_chapters",
        "full_name": "Feature Engineering and Selection (Kuhn, Johnson)",
    },
    "pdsh": {
        "dir_name": "capitulos_pdsh",
        "collection": "pdsh_chapters",
        "full_name": "Python Data Science Handbook (VanderPlas)",
    },
    "r4ds": {
        "dir_name": "capitulos_r4ds",
        "collection": "r4ds_chapters",
        "full_name": (
            "R for Data Science, 2nd Edition "
            "(Wickham, Çetinkaya-Rundel, Grolemund) — examples in R; "
            "principles transfer to pandas/Python"
        ),
        # ⚠️ R4DS está bajo licencia CC BY-NC-ND 3.0 US (NoDerivatives).
        # Originalmente local_only=True para no redistribuir; se cambió a False
        # para uso académico explícito. La decisión y el mecanismo de takedown
        # están documentados en DATA_CARD.md.
        "local_only": False,
    },
}


def extract_chapter_info(filename: str) -> dict:
    """Extrae número de archivo y nombre del capítulo del filename."""
    # Formato: 04_3_Linear_Methods_for_Regression.md
    stem = Path(filename).stem
    parts = stem.split("_", 1)
    file_order = parts[0] if parts else "00"
    chapter_title = parts[1].replace("_", " ") if len(parts) > 1 else stem
    return {"file_order": file_order, "chapter_title": chapter_title}


def split_by_sections(text: str, chapter_title: str) -> list[dict]:
    """
    Divide el texto en secciones usando headers markdown (# y ##).
    Cada sección se subdivide en chunks si es muy larga.
    """
    # Patrón para detectar headers de nivel 1-3
    header_pattern = re.compile(r"^(#{1,3})\s+(.+)$", re.MULTILINE)

    sections = []
    matches = list(header_pattern.finditer(text))

    if not matches:
        # Sin headers, tratar todo como una sección
        sections.append({"title": chapter_title, "level": 1, "content": text.strip()})
    else:
        # Texto antes del primer header
        pre_text = text[: matches[0].start()].strip()
        if pre_text and len(pre_text) > 50:
            sections.append({"title": chapter_title, "level": 1, "content": pre_text})

        for i, match in enumerate(matches):
            level = len(match.group(1))
            title = match.group(2).strip()
            start = match.end()
            end = matches[i + 1].start() if i + 1 < len(matches) else len(text)
            content = text[start:end].strip()

            if content and len(content) > 30:
                sections.append({"title": title, "level": level, "content": content})

    return sections


def chunk_text(text: str, chunk_size: int = CHUNK_SIZE, overlap: int = CHUNK_OVERLAP) -> list[str]:
    """
    Divide texto en chunks por caracteres con overlap.
    Intenta cortar en saltos de línea o puntos para no romper oraciones.
    """
    # Convertir chunk_size de tokens aprox a caracteres (1 token ≈ 4 chars)
    char_size = chunk_size * 4
    char_overlap = overlap * 4

    if len(text) <= char_size:
        return [text]

    chunks = []
    start = 0

    while start < len(text):
        end = start + char_size

        if end < len(text):
            # Buscar un buen punto de corte (párrafo o punto)
            # Primero intentar doble newline (párrafo)
            cut_point = text.rfind("\n\n", start + char_size // 2, end)
            if cut_point == -1:
                # Intentar punto seguido de espacio
                cut_point = text.rfind(". ", start + char_size // 2, end)
                if cut_point != -1:
                    cut_point += 1  # incluir el punto
            if cut_point == -1:
                # Intentar newline simple
                cut_point = text.rfind("\n", start + char_size // 2, end)
            if cut_point == -1:
                cut_point = end

            end = cut_point

        chunk = text[start:end].strip()
        if chunk:
            chunks.append(chunk)

        start = end - char_overlap
        if start >= len(text):
            break

    return chunks


def clean_text(text: str) -> str:
    """Limpia artefactos de la extracción PDF / scraping HTML."""
    # Eliminar YAML frontmatter al inicio (---\nkey: value\n---)
    text = re.sub(r"^---\s*\n.*?\n---\s*\n", "", text, count=1, flags=re.DOTALL)
    # Eliminar marcadores de página
    text = re.sub(r"---\s*Página\s*\d+\s*---", "", text)
    # Eliminar líneas con solo números (números de página sueltos)
    text = re.sub(r"^\d+\s*$", "", text, flags=re.MULTILINE)
    # Reducir múltiples líneas vacías
    text = re.sub(r"\n{4,}", "\n\n\n", text)
    # Eliminar copyright notices
    text = re.sub(r"©.*?(?:\n|$)", "", text)
    return text.strip()


def ingest_book(books_dir: Path, book_key: str, client: chromadb.ClientAPI, embedding_fn):
    """Ingesta un libro completo en ChromaDB."""
    config = BOOKS_CONFIG[book_key]
    chapters_dir = books_dir / config["dir_name"]

    if not chapters_dir.exists():
        print(f"  ⚠️  Directorio no encontrado: {chapters_dir}")
        return 0

    # Crear o obtener colección (reset si existe)
    try:
        client.delete_collection(config["collection"])
    except Exception:
        pass

    collection = client.get_or_create_collection(
        name=config["collection"],
        embedding_function=embedding_fn,
        metadata={"hnsw:space": "cosine"},
    )

    total_chunks = 0
    md_files = sorted(chapters_dir.glob("*.md"))
    # Excluir READMEs y notas auxiliares: solo capítulos NN_*.md
    md_files = [f for f in md_files if not f.name.upper().startswith("README")]

    print(f"\n  📚 {config['full_name']}")
    print(f"     Archivos encontrados: {len(md_files)}")

    for md_file in md_files:
        chapter_info = extract_chapter_info(md_file.name)
        raw_text = md_file.read_text(encoding="utf-8")
        text = clean_text(raw_text)

        if len(text) < 100:
            continue

        # Dividir en secciones
        sections = split_by_sections(text, chapter_info["chapter_title"])

        for section in sections:
            # Dividir secciones largas en chunks
            chunks = chunk_text(section["content"])

            for i, chunk in enumerate(chunks):
                chunk_id = f"{book_key}_{chapter_info['file_order']}_{section['title'][:30]}_{i}"
                # Sanitizar ID
                chunk_id = re.sub(r"[^a-zA-Z0-9_-]", "_", chunk_id)

                metadata = {
                    "book": book_key,
                    "book_full_name": config["full_name"],
                    "chapter": chapter_info["chapter_title"],
                    "section": section["title"],
                    "section_level": section["level"],
                    "chunk_index": i,
                    "total_chunks_in_section": len(chunks),
                    "file": md_file.name,
                }

                collection.add(
                    ids=[chunk_id],
                    documents=[chunk],
                    metadatas=[metadata],
                )
                total_chunks += 1

        print(f"     ✓ {md_file.name} → {len(sections)} secciones")

    print(f"     Total chunks: {total_chunks}")
    return total_chunks


def main():
    parser = argparse.ArgumentParser(description="Ingesta de libros ESL/ISLP en ChromaDB")
    parser.add_argument(
        "--books-dir",
        type=Path,
        default=Path(__file__).parent.parent.parent / "ebook",
        help="Directorio raíz con las carpetas de capítulos",
    )
    parser.add_argument(
        "--chroma-dir",
        type=Path,
        default=CHROMA_DIR,
        help="Directorio para la base de datos ChromaDB",
    )
    args = parser.parse_args()

    print("🔧 Inicializando embedding model...")
    embedding_fn = SentenceTransformerEmbeddingFunction(model_name=EMBEDDING_MODEL)

    print(f"🗄️  ChromaDB persistente en: {args.chroma_dir}")
    client = chromadb.PersistentClient(path=str(args.chroma_dir))

    print("\n📖 Iniciando ingesta de libros...")
    total = 0
    for book_key in BOOKS_CONFIG:
        total += ingest_book(args.books_dir, book_key, client, embedding_fn)

    print(f"\n✅ Ingesta completada. Total de chunks vectorizados: {total}")
    print(f"   Base de datos en: {args.chroma_dir}")


if __name__ == "__main__":
    main()