"""
utils/export.py — CSV and Excel export helpers for report data.
"""

import csv
import logging
import os
from datetime import datetime

logger = logging.getLogger("export")


def _timestamp() -> str:
    return datetime.now().strftime("%Y%m%d_%H%M%S")


def export_csv(rows: list, columns: list, base_filename: str, save_dir: str) -> str:
    """
    Write rows (list of dicts) to a CSV file.
    Returns the full path of the written file.
    """
    filename = f"{base_filename}_{_timestamp()}.csv"
    filepath = os.path.join(save_dir, filename)

    try:
        with open(filepath, "w", newline="", encoding="utf-8-sig") as fh:
            writer = csv.DictWriter(fh, fieldnames=columns, extrasaction="ignore")
            writer.writeheader()
            for row in rows:
                # Convert non-string types (date, datetime) to string
                clean = {k: (str(v) if v is not None else "") for k, v in row.items()}
                writer.writerow(clean)
        logger.info(f"[EXPORT] CSV written: {filepath} ({len(rows)} rows)")
        return filepath
    except Exception as e:
        logger.error(f"CSV export failed: {e}")
        raise


def export_excel(rows: list, columns: list, base_filename: str,
                 save_dir: str, sheet_title: str = "Report") -> str:
    """
    Write rows (list of dicts) to an .xlsx file with basic formatting.
    Returns the full path of the written file.
    """
    try:
        import openpyxl
        from openpyxl.styles import Font, PatternFill, Alignment, Border, Side
    except ImportError:
        raise RuntimeError(
            "openpyxl is required for Excel export.\n"
            "Install it with: pip install openpyxl"
        )

    filename = f"{base_filename}_{_timestamp()}.xlsx"
    filepath = os.path.join(save_dir, filename)

    wb = openpyxl.Workbook()
    ws = wb.active
    ws.title = sheet_title[:31]   # Excel sheet name limit

    # ── Header style ──────────────────────────────────────────────────────────
    header_fill   = PatternFill("solid", fgColor="7C6AF7")   # accent purple
    header_font   = Font(bold=True, color="FFFFFF", name="Calibri", size=11)
    header_align  = Alignment(horizontal="center", vertical="center", wrap_text=True)
    thin_border   = Border(
        bottom=Side(style="thin", color="45475A"),
        right=Side(style="thin",  color="45475A"),
    )

    # ── Write header row ──────────────────────────────────────────────────────
    for col_idx, col_name in enumerate(columns, start=1):
        cell = ws.cell(row=1, column=col_idx, value=col_name.replace("_", " ").title())
        cell.font    = header_font
        cell.fill    = header_fill
        cell.alignment = header_align
        cell.border  = thin_border

    ws.row_dimensions[1].height = 22

    # ── Write data rows ───────────────────────────────────────────────────────
    alt_fill = PatternFill("solid", fgColor="2A2A3E")
    for row_idx, row in enumerate(rows, start=2):
        fill = alt_fill if row_idx % 2 == 0 else PatternFill("solid", fgColor="1E1E2E")
        for col_idx, col_name in enumerate(columns, start=1):
            val = row.get(col_name)
            if val is None:
                val = ""
            cell = ws.cell(row=row_idx, column=col_idx, value=str(val))
            cell.font      = Font(name="Calibri", size=10, color="CDD6F4")
            cell.fill      = fill
            cell.alignment = Alignment(vertical="center", wrap_text=False)
            cell.border    = thin_border

    # ── Auto-width columns (capped at 60) ─────────────────────────────────────
    for col_idx, col_name in enumerate(columns, start=1):
        col_letter = openpyxl.utils.get_column_letter(col_idx)
        header_len = len(col_name.replace("_", " ").title())
        max_data_len = max(
            (len(str(row.get(col_name) or "")) for row in rows),
            default=0
        )
        ws.column_dimensions[col_letter].width = min(max(header_len, max_data_len) + 4, 60)

    # ── Freeze top row ────────────────────────────────────────────────────────
    ws.freeze_panes = "A2"

    wb.save(filepath)
    logger.info(f"[EXPORT] Excel written: {filepath} ({len(rows)} rows)")
    return filepath