"""Reader for CSV, tab-delimited, and TSV files."""
import csv
MAX_CHUNK_CHARS = 6000

def read_csv_tab(file_path: str, delimiter: str = None) -> list[dict]:
    try:
        from pathlib import Path
        if delimiter is None:
            ext = Path(file_path).suffix.lower()
            delimiter = "\t" if ext in (".tab", ".tsv") else ","

        with open(file_path, "r", encoding="utf-8-sig", errors="replace") as f:
            reader = csv.reader(f, delimiter=delimiter)
            rows = list(reader)

        if not rows:
            return []

        headers = [h.strip().strip('"') for h in rows[0]]
        row_texts = []
        for row in rows[1:]:
            parts = []
            padded_row = list(row) + [""] * max(0, len(headers) - len(row))
            for header, val in zip(headers, padded_row[:len(headers)]):
                val = val.strip().strip('"')
                if val:
                    parts.append(f"{header}: {val}")
            if parts:
                row_texts.append("; ".join(parts))

        pages = []
        header_line = f"Columns: {', '.join(headers)}\n"
        block = []
        block_chars = len(header_line)
        block_start = 1

        for idx, row_text in enumerate(row_texts):
            if block and block_chars + len(row_text) + 1 > MAX_CHUNK_CHARS:
                text = header_line + "\n".join(block)
                pages.append({"page": f"rows_{block_start}-{block_start + len(block) - 1}", "text": text})
                block = []
                block_chars = len(header_line)
                block_start = idx + 1
            block.append(row_text)
            block_chars += len(row_text) + 1

        if block:
            text = header_line + "\n".join(block)
            pages.append({"page": f"rows_{block_start}-{block_start + len(block) - 1}", "text": text})
        return pages
    except Exception as e:
        print(f"Warning: Could not read {file_path}: {e}")
        return []