gridcraft/crates/xlsx/src/fmla.rs

//! Formula text conversion between the model (canonical text, no `=`) and files (`_xlfn.`
//! prefixes for newer functions).

use gridcraft_formula::Expr;
use gridcraft_model::Formula;

/// Formula text for a file.
pub fn to_file(f: &Formula) -> String {
    match f.expr() {
        Some(e) => expr_to_file(e),
        None => f.text.clone(),
    }
}

/// Arbitrary formula text (names, CF, validation) for a file. Unparseable text is kept.
pub fn text_to_file(text: &str) -> String {
    let body = text.strip_prefix('=').unwrap_or(text);
    match gridcraft_formula::parse(body) {
        Ok(e) => expr_to_file(e),
        Err(_) => body.to_string(),
    }
}

fn expr_to_file(e: Expr) -> String {
    let e = e.map(&mut |x| match x {
        Expr::Call(name, args) => match crate::tables::file_function_name(&name) {
            Some(n) => Expr::Call(n, args),
            None => Expr::Call(name, args),
        },
        other => other,
    });
    gridcraft_formula::print(&e)
}

/// Formula text read from a file → model text (strips prefixes when it parses).
pub fn from_file(text: &str) -> String {
    let body = text.strip_prefix('=').unwrap_or(text);
    match gridcraft_formula::parse(body) {
        Ok(e) => gridcraft_formula::print(&e),
        Err(_) => body.to_string(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn prefixes() {
        assert_eq!(to_file(&Formula::new("XLOOKUP(1,A:A,B:B)+SUM(A1)")), "_xlfn.XLOOKUP(1,A:A,B:B)+SUM(A1)");
        assert_eq!(to_file(&Formula::new("FILTER(A1:A3,B1:B3)")), "_xlfn._xlws.FILTER(A1:A3,B1:B3)");
        assert_eq!(from_file("_xlfn.XLOOKUP(1,A:A,B:B)"), "XLOOKUP(1,A:A,B:B)");
        assert_eq!(text_to_file("=IFS(A1>0,1)"), "_xlfn.IFS(A1>0,1)");
    }
}