use super::entry::*;
use super::table::*;
use bigdecimal::BigDecimal;
use std::iter;
use std::str::FromStr;

fn symbols() -> impl Iterator<Item = (Option<UnitPrefix>, BaseUnit, String)> {
    ENTRIES.iter().flat_map(|entry| {
        iter::once((None, ""))
            .chain(entry.prefixes.iter().flat_map(|prefix| {
                prefix
                    .keywords()
                    .iter()
                    .map(|keyword| (Some(*prefix), *keyword))
            }))
            .flat_map(move |(prefix, psym)| {
                entry
                    .symbols
                    .iter()
                    .map(move |sym| (prefix, entry.base, format!("{}{}", psym, sym)))
            })
    })
}

pub fn parse_symbol(s: &str) -> Option<(Option<UnitPrefix>, BaseUnit)> {
    symbols()
        .find(|(_, _, sym)| sym.eq_ignore_ascii_case(s))
        .map(|(prefix, base, _)| (prefix, base))
}

pub fn parse_num_symbol(s: &str) -> Option<(&str, &str)> {
    symbols()
        .find(|(_, _, sym)| {
            s.strip_suffix(sym.as_str())
                .and_then(|s| BigDecimal::from_str(s).ok())
                .is_some()
        })
        .map(|(_, _, sym)| {
            let len = s.len() - sym.len();
            (&s[..len], &s[len..])
        })
}