"""Parse source xlsx files into structured source line data.

Validates the expected 5 column headers (case sensitive):
EN_GB, Copy Type, Creative Guidance, Visual Ref, Char Limit

Skips rows where EN_GB is empty. Detects \\n in EN_GB for is_display_format.
"""

from typing import Any

from openpyxl import load_workbook

REQUIRED_HEADERS = ["EN_GB", "Copy Type", "Creative Guidance", "Visual Ref", "Char Limit"]


class SourceFileParseError(Exception):
    """Raised when the source file has validation errors."""
    pass


def parse_source_file(file_path: str) -> list[dict[str, Any]]:
    """Parse a source xlsx file and return a list of source line dicts.

    Args:
        file_path: Absolute path to the xlsx file.

    Returns:
        List of dicts with keys: en_gb, copy_type, creative_guidance,
        visual_ref, char_limit, is_display_format.

    Raises:
        SourceFileParseError: If headers are invalid or file cannot be read.
    """
    try:
        wb = load_workbook(file_path, read_only=True, data_only=True)
    except Exception as exc:
        raise SourceFileParseError(f"Cannot open xlsx file: {exc}")

    ws = wb.active
    if ws is None:
        raise SourceFileParseError("Workbook has no active sheet")

    # Read and validate headers from first row
    rows = ws.iter_rows(min_row=1, max_row=1, values_only=True)
    first_row = next(rows, None)
    if first_row is None:
        raise SourceFileParseError("File is empty - no header row found")

    headers = [str(cell).strip() if cell else "" for cell in first_row]

    # Validate all required headers exist (case sensitive)
    for required in REQUIRED_HEADERS:
        if required not in headers:
            raise SourceFileParseError(
                f"Missing required header '{required}'. "
                f"Found headers: {headers}. "
                f"Expected: {REQUIRED_HEADERS}"
            )

    # Build column index map
    col_map = {header: idx for idx, header in enumerate(headers)}

    # Parse data rows
    source_lines: list[dict[str, Any]] = []
    for row in ws.iter_rows(min_row=2, values_only=True):
        en_gb_idx = col_map["EN_GB"]
        en_gb_raw = row[en_gb_idx] if en_gb_idx < len(row) else None

        # Skip rows where EN_GB is empty
        if en_gb_raw is None or str(en_gb_raw).strip() == "":
            continue

        en_gb = str(en_gb_raw).strip()

        # Detect display format: presence of \n in EN_GB text
        is_display_format = "\n" in en_gb

        def _get_cell(header: str) -> str | None:
            idx = col_map.get(header)
            if idx is None or idx >= len(row):
                return None
            val = row[idx]
            if val is None:
                return None
            return str(val).strip() or None

        source_lines.append({
            "en_gb": en_gb,
            "copy_type": _get_cell("Copy Type"),
            "creative_guidance": _get_cell("Creative Guidance"),
            "visual_ref": _get_cell("Visual Ref"),
            "char_limit": _get_cell("Char Limit"),
            "is_display_format": is_display_format,
        })

    wb.close()
    return source_lines