geam 0.1.1

Experimental Rust-embedded execution runtime for typed Gleam programs
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use super::super::schema::{PopConstructions, PopError, PopOk, PopPairIndex, PopResult};
use super::StringProvider;
use crate::gleam_stdlib::GleamStdlibHostProfile;
use crate::{
    HostCall, HostCallCompletion, HostCallError, HostConstructions, HostFailure, HostList,
};
use ecow::EcoString;
use num_bigint::BigInt;
use num_traits::ToPrimitive;
use unicode_segmentation::UnicodeSegmentation;

pub(in crate::gleam_stdlib::string) fn pop_grapheme<'call, Profile>(
    mut call: HostCall<'call, Profile, StringProvider<Profile>, PopResult>,
    constructions: HostConstructions<'call, PopConstructions>,
    string: EcoString,
) -> Result<HostCallCompletion<'call, PopResult>, HostCallError>
where
    Profile: GleamStdlibHostProfile,
{
    let Some(grapheme) = string.graphemes(true).next() else {
        return Ok(call.return_custom::<PopError>(((), ())));
    };
    let rest = EcoString::from(&string[grapheme.len()..]);
    let pair = call.construct_tuple(
        constructions.at::<PopPairIndex>(),
        (grapheme.into(), (rest, ())),
    );
    Ok(call.return_custom::<PopOk>((pair, ())))
}

pub(in crate::gleam_stdlib::string) fn unsafe_int_to_utf_codepoint(
    value: BigInt,
) -> Result<char, HostFailure> {
    value
        .to_u32()
        .and_then(char::from_u32)
        .ok_or_else(|| HostFailure::new("integer is not a valid Unicode codepoint"))
}

pub(in crate::gleam_stdlib::string) fn from_utf_codepoints<'call, Profile>(
    mut call: HostCall<'call, Profile, StringProvider<Profile>, EcoString>,
    values: HostList<'call, char>,
) -> Result<HostCallCompletion<'call, EcoString>, HostCallError>
where
    Profile: GleamStdlibHostProfile,
{
    let mut string = String::new();
    let mut index = 0;
    while let Some(value) = call.list_item(values, index) {
        string.push(value);
        index += 1;
    }
    Ok(call.return_value(string.into()))
}

pub(in crate::gleam_stdlib::string) fn utf_codepoint_to_int(value: char) -> BigInt {
    BigInt::from(u32::from(value))
}

#[cfg(test)]
mod tests {
    use super::{unsafe_int_to_utf_codepoint, utf_codepoint_to_int};
    use num_bigint::BigInt;

    #[test]
    fn converts_exact_unicode_scalar_values() {
        assert_eq!(unsafe_int_to_utf_codepoint(65.into()), Ok('A'));
        assert_eq!(
            utf_codepoint_to_int('\u{10ffff}'),
            BigInt::from(0x10ffff_u32)
        );
        assert_eq!(
            unsafe_int_to_utf_codepoint((-1).into())
                .expect_err("negative codepoint should fail")
                .message(),
            "integer is not a valid Unicode codepoint",
        );
        assert_eq!(
            unsafe_int_to_utf_codepoint(0xd800_u32.into())
                .expect_err("surrogate should fail")
                .message(),
            "integer is not a valid Unicode codepoint",
        );
        assert_eq!(
            unsafe_int_to_utf_codepoint(BigInt::from(u64::MAX))
                .expect_err("unrepresentable codepoint should fail")
                .message(),
            "integer is not a valid Unicode codepoint",
        );
    }
}