Cheat interface

[perrello]

A lot of cores have to option to add cheats. Currently this is not in Nostalgist but would be a great addition. Somehow the project does not work local on my pc and i gave up trying. So instead of an MR i started this discussion.

I have cheats working in my project and the gist of it is:

export function filterEnabledCheats(cheats: Cheat[]): Cheat[] {
    return cheats.filter(c => c.enabled && c.code && c.code.trim().length > 0);
}

export function freeCheatPointers(
    Module: RetroArchEmscriptenModule,
    pointers: number[]
): void {
    for (const ptr of pointers) {
        try {
            Module._free(ptr);
        } catch {
            /* do something*/
        }
    }
}

export function prepareCheatSlots(
    Module: RetroArchEmscriptenModule,
    count: number
): void {
    // reset struct
    Module._cmd_cheat_realloc(0);

    if (count > 0) {
        Module._cmd_cheat_realloc(count);
    }
}

export function addCheatToModule(
    Module: RetroArchEmscriptenModule,
    index: number,
    cheat: Cheat
): number | null {
    if (!cheat.code || !cheat.code.trim()) {
        return null;
    }

    const ptr = Module.stringToNewUTF8(cheat.code);

    Module._cmd_cheat_set_code(index, ptr);
    Module._cmd_cheat_toggle_index(index, 1);

    return ptr;
}

export function applyAllCheats(Module: RetroArchEmscriptenModule): void {
    Module._cmd_cheat_apply_cheats();
}

export function handleCheats(
    Module: RetroArchEmscriptenModule,
    cheats: Cheat[],
    previousPtrs: number[] = []
): number[] {

    const enabled = filterEnabledCheats(cheats);

    freeCheatPointers(Module, previousPtrs);

    prepareCheatSlots(Module, enabled.length);

    if (enabled.length === 0) {
        applyAllCheats(Module);
        return [];
    }

    const newPtrs: number[] = [];

    enabled.forEach((cheat, index) => {
        const ptr = addCheatToModule(Module, index, cheat);
        if (ptr !== null) {
            newPtrs.push(ptr);
        }
    });

    applyAllCheats(Module);

    return newPtrs;
}