"""
document_loader.py
Parses uploaded files (PDF, DOCX, TXT/MD) into plain text.
"""

import os
from pathlib import Path


def load_documents(file_paths: list[str]) -> list[dict]:
    """
    Given a list of file paths, parse each into a dict:
      { "source": filename, "text": full text content }
    Supports: .pdf, .docx, .txt, .md
    """
    docs = []
    for path in file_paths:
        if path is None:
            continue
        ext = Path(path).suffix.lower()
        name = Path(path).name
        try:
            if ext == ".pdf":
                text = _load_pdf(path)
            elif ext == ".docx":
                text = _load_docx(path)
            elif ext in (".txt", ".md", ".csv"):
                text = _load_text(path)
            else:
                print(f"[Loader] Unsupported file type: {ext} — skipping {name}")
                continue

            if text.strip():
                docs.append({"source": name, "text": text})
            else:
                print(f"[Loader] Empty content from {name} — skipping")
        except Exception as e:
            print(f"[Loader] Failed to load {name}: {e}")

    return docs


def _load_pdf(path: str) -> str:
    import fitz  # PyMuPDF
    doc = fitz.open(path)
    pages = []
    for page in doc:
        pages.append(page.get_text("text"))
    doc.close()
    return "\n".join(pages)


def _load_docx(path: str) -> str:
    from docx import Document
    doc = Document(path)

    parts: list[str] = []

    # Body paragraphs (existing)
    for p in doc.paragraphs:
        if p.text.strip():
            parts.append(p.text.strip())

    # Tables — previously skipped entirely
    for table in doc.tables:
        for row in table.rows:
            cells = [cell.text.strip() for cell in row.cells if cell.text.strip()]
            if cells:
                parts.append("\t".join(cells))

    return "\n".join(parts)


def _load_text(path: str) -> str:
    """Load plain text files. CSVs are parsed into natural-language row sentences."""
    ext = Path(path).suffix.lower()
    if ext == ".csv":
        return _load_csv(path)
    with open(path, "r", encoding="utf-8", errors="ignore") as f:
        return f.read()


def _load_csv(path: str) -> str:
    """
    Parse a CSV file into natural-language sentences.

    Each row becomes:   "ColumnA: value1. ColumnB: value2. ..."
    This makes tabular data semantically meaningful to the LLM rather
    than presenting it as raw comma-separated text.
    """
    import csv

    rows: list[str] = []
    with open(path, "r", encoding="utf-8", errors="ignore", newline="") as f:
        reader = csv.DictReader(f)
        if reader.fieldnames is None:
            # Fallback to raw text for headerless CSVs
            f.seek(0)
            return f.read()

        for row in reader:
            parts = [f"{col}: {val.strip()}" for col, val in row.items() if val and val.strip()]
            if parts:
                rows.append(". ".join(parts) + ".")

    return "\n".join(rows)