import logging
import re
from pathlib import Path

logger = logging.getLogger(__name__)

MAX_FILE_SIZE = 5 * 1024 * 1024  # 5 MB


def load_txt(path: str) -> str:
    return Path(path).read_text(encoding="utf-8", errors="replace")


def load_md(path: str) -> str:
    text = Path(path).read_text(encoding="utf-8", errors="replace")
    # Strip markdown syntax: headers, bold/italic, links, code fences
    text = re.sub(r"^#{1,6}\s+", "", text, flags=re.MULTILINE)
    text = re.sub(r"\*{1,3}(.+?)\*{1,3}", r"\1", text)
    text = re.sub(r"`{1,3}[^`]*`{1,3}", "", text, flags=re.DOTALL)
    text = re.sub(r"!\[.*?\]\(.*?\)", "", text)
    text = re.sub(r"\[(.+?)\]\(.*?\)", r"\1", text)
    text = re.sub(r"^\s*[-*+]\s+", "", text, flags=re.MULTILINE)
    return text


def load_pdf(path: str) -> str:
    try:
        import pdfplumber
    except ImportError:
        logger.warning("pdfplumber not installed, cannot load PDF: %s", path)
        return ""

    pages = []
    with pdfplumber.open(path) as pdf:
        for i, page in enumerate(pdf.pages, start=1):
            page_text = page.extract_text() or ""
            pages.append(f"--- strona {i} ---\n{page_text}")
    return "\n".join(pages)


def load_file(path: str) -> str:
    p = Path(path)
    ext = p.suffix.lower()
    if ext == ".pdf":
        return load_pdf(path)
    if ext == ".md":
        return load_md(path)
    return load_txt(path)


def build_corpus(file_paths: list) -> dict[str, list[str]]:
    corpus: dict[str, list[str]] = {}
    for fp in file_paths:
        p = Path(fp)
        try:
            size = p.stat().st_size
            if size > MAX_FILE_SIZE:
                logger.warning("Plik %s przekracza 5 MB (%d B) - pomijam.", p.name, size)
                continue
            text = load_file(str(p))
            corpus[p.name] = text.splitlines()
        except Exception as exc:
            logger.warning("Nie można wczytać pliku %s: %s", p.name, exc)
    return corpus