use crate::model::cell::CellValue;

/// Format a CellValue for display with number formatting options.
pub fn format_value(v: Option<&CellValue>, comma: bool, decimals: u8) -> String {
    match v {
        Some(CellValue::Number(n)) => format_f64(*n, comma, decimals),
        Some(CellValue::Text(s)) => s.clone(),
        None => String::new(),
    }
}

/// Parse a number format string like ",.0" into (use_commas, decimal_places).
pub fn parse_number_format(fmt: &str) -> (bool, u8) {
    let comma = fmt.contains(',');
    let decimals = fmt
        .rfind('.')
        .and_then(|i| fmt[i + 1..].parse::<u8>().ok())
        .unwrap_or(0);
    (comma, decimals)
}

/// Format an f64 with optional comma grouping and decimal places.
pub fn format_f64(n: f64, comma: bool, decimals: u8) -> String {
    let formatted = format!("{:.prec$}", n, prec = decimals as usize);
    if !comma {
        return formatted;
    }
    let (int_part, dec_part) = if let Some(dot) = formatted.find('.') {
        (&formatted[..dot], Some(&formatted[dot..]))
    } else {
        (&formatted[..], None)
    };
    let is_neg = int_part.starts_with('-');
    let digits = if is_neg { &int_part[1..] } else { int_part };
    let mut result = String::new();
    for (idx, c) in digits.chars().rev().enumerate() {
        if idx > 0 && idx % 3 == 0 {
            result.push(',');
        }
        result.push(c);
    }
    if is_neg {
        result.push('-');
    }
    let mut out: String = result.chars().rev().collect();
    if let Some(dec) = dec_part {
        out.push_str(dec);
    }
    out
}