neser 0.1.1

NESER - NES Emulator in Rust - is a NES emulator written in Rust. It aims to be a high-quality, hardware-accurate emulator that is also easy to use and extend. It supports a wide range of NES games and features, including various mappers, audio processing, and input handling. NESER is designed to be modular and extensible, allowing developers to easily add new features or support for additional hardware. It can be run using one of two frontends: a native desktop application using SDL2, or a web application using WebAssembly. The desktop application provides a high-performance, feature-rich experience with support for various input devices and display options, while the web application allows users to play NES games directly in their browsers without needing to install any software in a BYOR manner (Bring Your Own Roms).
Documentation 
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//! Mapper 110 - Sachen SA-020A (deprecated iNES duplicate assignment)
//!
//! Specifications:
//! - Legacy assignment: <https://www.nesdev.org/wiki/INES_Mapper_110>
//! - Canonical implementation: <https://www.nesdev.org/wiki/INES_Mapper_243>
//!
//! Known Limitations:
//! - Mapper 110 is an obsolete duplicate assignment for Sachen SA-020A.
//! - This implementation intentionally mirrors mapper 243 behavior.

use crate::cartridge::mapper243::Mapper243;

/// Mapper 110 - obsolete iNES duplicate assignment for Sachen SA-020A.
///
/// Per NesDev, mapper 110 should behave like mapper 243 and is kept only for
/// compatibility with legacy ROM headers.
pub type Mapper110 = Mapper243;

#[cfg(test)]
mod tests {
    use crate::cartridge::NametableLayout;
    use crate::cartridge::mapper::{Mapper, MapperContext, create_mapper};
    use crate::cartridge::test_helpers::banked_data;

    fn create_mapper110(
        prg_rom: Vec<u8>,
        chr_rom: Vec<u8>,
        mirroring: NametableLayout,
    ) -> std::io::Result<Box<dyn Mapper>> {
        create_mapper(MapperContext::new_for_test(
            110, prg_rom, chr_rom, mirroring,
        ))
    }

    #[test]
    fn mapper_110_is_registered_in_factory() {
        let prg_rom = banked_data(32 * 1024, 2);
        let chr_rom = banked_data(8 * 1024, 8);
        let mapper = create_mapper110(prg_rom, chr_rom, NametableLayout::Vertical);
        assert!(mapper.is_ok(), "Mapper 110 should be creatable via factory");
    }

    #[test]
    fn mapper_110_prg_bank_switching_matches_sa020a_register_5() {
        let prg_rom = banked_data(32 * 1024, 2);
        let chr_rom = banked_data(8 * 1024, 8);
        let mut mapper = create_mapper110(prg_rom, chr_rom, NametableLayout::Vertical).unwrap();

        assert_eq!(mapper.read_prg(0x8000), 0);

        mapper.write_prg(0x4100, 5);
        mapper.write_prg(0x4101, 1);
        assert_eq!(mapper.read_prg(0x8000), 1);

        mapper.write_prg(0x4101, 0);
        assert_eq!(mapper.read_prg(0x8000), 0);
    }

    #[test]
    fn mapper_110_chr_and_mirroring_match_sa020a_registers() {
        let prg_rom = banked_data(32 * 1024, 1);
        let chr_rom = banked_data(8 * 1024, 8);
        let mut mapper = create_mapper110(prg_rom, chr_rom, NametableLayout::Vertical).unwrap();

        mapper.write_prg(0x4100, 2);
        mapper.write_prg(0x4101, 0x0A); // bit1=1 (H mirroring), bit3=1 (CHR bit0)

        mapper.write_prg(0x4100, 4);
        mapper.write_prg(0x4101, 0x02); // CHR bit1=1

        mapper.write_prg(0x4100, 6);
        mapper.write_prg(0x4101, 0x02); // CHR bit2=1

        assert_eq!(mapper.read_chr(0x0000), 7);
        assert_eq!(mapper.get_mirroring(), NametableLayout::Horizontal);
    }
}