// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

use crate::expression_tree::Expression;
use crate::expression_tree::Unit;
use itertools::Itertools;
use smol_str::SmolStr;
use strum::IntoEnumIterator;

pub fn unescape_string(string: &str) -> Option<SmolStr> {
    if string.contains('\n') {
        // FIXME: new line in string literal not yet supported
        return None;
    }
    let string = string.strip_prefix('"').or_else(|| string.strip_prefix('}'))?;
    let string = string.strip_suffix('"').or_else(|| string.strip_suffix("\\{"))?;
    if !string.contains('\\') {
        return Some(string.into());
    }
    let mut result = String::with_capacity(string.len());
    let mut pos = 0;
    loop {
        let stop = match string[pos..].find('\\') {
            Some(stop) => pos + stop,
            None => {
                result += &string[pos..];
                return Some(result.into());
            }
        };
        if stop + 1 >= string.len() {
            return None;
        }
        result += &string[pos..stop];
        pos = stop + 2;
        match string.as_bytes()[stop + 1] {
            b'"' => result += "\"",
            b'\\' => result += "\\",
            b'n' => result += "\n",
            b'u' => {
                if string.as_bytes().get(pos)? != &b'{' {
                    return None;
                }
                let end = string[pos..].find('}')? + pos;
                let x = u32::from_str_radix(&string[pos + 1..end], 16).ok()?;
                result.push(std::char::from_u32(x)?);
                pos = end + 1;
            }
            _ => return None,
        }
    }
}

#[test]
fn test_unescape_string() {
    assert_eq!(unescape_string(r#""foo_bar""#), Some("foo_bar".into()));
    assert_eq!(unescape_string(r#""foo\"bar""#), Some("foo\"bar".into()));
    assert_eq!(unescape_string(r#""foo\\\"bar""#), Some("foo\\\"bar".into()));
    assert_eq!(unescape_string(r#""fo\na\\r""#), Some("fo\na\\r".into()));
    assert_eq!(unescape_string(r#""fo\xa""#), None);
    assert_eq!(unescape_string(r#""fooo\""#), None);
    assert_eq!(unescape_string(r#""f\n\n\nf""#), Some("f\n\n\nf".into()));
    assert_eq!(unescape_string(r#""music\♪xx""#), None);
    assert_eq!(unescape_string(r#""music\"♪\"🎝""#), Some("music\"♪\"🎝".into()));
    assert_eq!(unescape_string(r#""foo_bar"#), None);
    assert_eq!(unescape_string(r#""foo_bar\"#), None);
    assert_eq!(unescape_string(r#"foo_bar""#), None);
    assert_eq!(unescape_string(r#""d\u{8}a\u{d4}f\u{Ed3}""#), Some("d\u{8}a\u{d4}f\u{ED3}".into()));
    assert_eq!(unescape_string(r#""xxx\""#), None);
    assert_eq!(unescape_string(r#""xxx\u""#), None);
    assert_eq!(unescape_string(r#""xxx\uxx""#), None);
    assert_eq!(unescape_string(r#""xxx\u{""#), None);
    assert_eq!(unescape_string(r#""xxx\u{22""#), None);
    assert_eq!(unescape_string(r#""xxx\u{qsdf}""#), None);
    assert_eq!(unescape_string(r#""xxx\u{1234567890}""#), None);
}

pub fn parse_number_literal(s: SmolStr) -> Result<Expression, SmolStr> {
    let bytes = s.as_bytes();
    let mut end = 0;
    while end < bytes.len() && matches!(bytes[end], b'0'..=b'9' | b'.') {
        end += 1;
    }
    let val = s[..end].parse().map_err(|_| "Cannot parse number literal".to_owned())?;
    let unit = s[end..].parse().map_err(|_| {
        format!(
            "Invalid unit '{}'. Valid units are: {}",
            s.get(end..).unwrap_or(&s),
            Unit::iter().filter(|x| !x.to_string().is_empty()).join(", ")
        )
    })?;
    Ok(Expression::NumberLiteral(val, unit))
}

#[test]
fn test_parse_number_literal() {
    use crate::expression_tree::Unit;
    use smol_str::{ToSmolStr, format_smolstr};

    fn doit(s: &str) -> Result<(f64, Unit), SmolStr> {
        parse_number_literal(s.into()).map(|e| match e {
            Expression::NumberLiteral(a, b) => (a, b),
            _ => panic!(),
        })
    }

    assert_eq!(doit("10"), Ok((10., Unit::None)));
    assert_eq!(doit("10phx"), Ok((10., Unit::Phx)));
    assert_eq!(doit("10.0phx"), Ok((10., Unit::Phx)));
    assert_eq!(doit("10.0"), Ok((10., Unit::None)));
    assert_eq!(doit("1.1phx"), Ok((1.1, Unit::Phx)));
    assert_eq!(doit("10.10"), Ok((10.10, Unit::None)));
    assert_eq!(doit("10000000"), Ok((10000000., Unit::None)));
    assert_eq!(doit("10000001phx"), Ok((10000001., Unit::Phx)));

    let cannot_parse = Err("Cannot parse number literal".to_smolstr());
    assert_eq!(doit("12.10.12phx"), cannot_parse);

    let valid_units = Unit::iter().filter(|x| x.to_string().len() > 0).join(", ");
    let wrong_unit_spaced =
        Err(format_smolstr!("Invalid unit ' phx'. Valid units are: {}", valid_units));
    assert_eq!(doit("10000001 phx"), wrong_unit_spaced);
    let wrong_unit_oo = Err(format_smolstr!("Invalid unit 'oo'. Valid units are: {}", valid_units));
    assert_eq!(doit("12.12oo"), wrong_unit_oo);
    let wrong_unit_euro =
        Err(format_smolstr!("Invalid unit '€'. Valid units are: {}", valid_units));
    assert_eq!(doit("12.12€"), wrong_unit_euro);
}
