import std.string: format;
import std.asserterror: AssertError;
import meta.nameof: symbolnameof; // useful but not necessary


align (1) struct Uint24 {
    alias typeof(*this) ThisType; // Can this be avoided?

    // can be replaced by the struct name if symbolnameof isn't available
    const name = symbolnameof!(ThisType);

    const uint init = 0; // this init doesn't work well with typedef:
                         // typedef Uint24 Uint24b = 10;
    const uint min = 0;
    const uint max = (1 << 24) - 1; // 16_777_215

    ushort low = init & 0xffff;
    ubyte up = init >> 16;

    static ThisType opCall(long n) {
        ThisType self;
        assert(n >= this.min && n <= this.max,
               format("%s(%d) not representable in 24 bits.", name, n));
        self.low = n & 0xffff;
        self.up = n >> 16;
        return self;
    }

    void opAssign(long n) {
        assert(n >= this.min && n <= this.max,
               format("%s(%d) not representable in 24 bits.", name, n));
        low = n & 0xffff;
        up = n >> 16;
    }

    uint opCast() {
        //return (up << 16) | low; // worse?
        return *(cast(uint*)(cast(void*)this));
    }

    uint val() {
        return *(cast(uint*)(cast(void*)this));
    }

    bool opEquals(ThisType other) {
        //return (this.up == other.up) && (this.low == other.low); // worse?
        uint self_uint = *(cast(uint*)(cast(void*)this));
        uint other_uint = *(cast(uint*)(cast(void*)(&other)));
        return self_uint == other_uint;
    }

    bool opEquals(long n) {
        uint self_uint = *(cast(uint*)(cast(void*)this));
        return self_uint == n;
    }

    bool opEquals(int n) {
        uint self_uint = *(cast(uint*)(cast(void*)this));
        return self_uint == n;
    }

    int opCmp(ThisType other) {
        uint self_uint = *(cast(uint*)(cast(void*)this));
        uint other_uint = *(cast(uint*)(cast(void*)(&other)));
        if (self_uint > other_uint)
            return 1;
        if (self_uint < other_uint)
            return -1;
        return 0;
    }

    int opCmp(long n) {
        uint self_uint = *(cast(uint*)(cast(void*)this));

        if (self_uint > n)
            return 1;
        else
            return self_uint < n ? -1 : 0;
    }

    int opCmp(int n) {
        uint self_uint = *(cast(uint*)(cast(void*)this));

        if (self_uint > n)
            return 1;
        else
            return self_uint < n ? -1 : 0;
    }


    string toString() {
        uint self_uint = *(cast(uint*)(cast(void*)this));
        return format("%s(%d)", name, self_uint);
    }
}