module cm3d2.util;

import std.bitmanip;
import std.range;
import std.traits;

ubyte readByte(Range)(ref Range data)
        if (isRandomAccessRange!(Unqual!(Range))
            && is(ElementType!Range == ubyte) && hasSlicing!Range)
{
    auto value = data[0];
    data = data[1 .. $];
    return value;
}

ubyte[] readBytes(Range)(ref Range data, uint count)
        if (isRandomAccessRange!(Unqual!(Range))
            && is(ElementType!Range == ubyte) && hasSlicing!Range)
{
    ubyte[] bytes = new ubyte[count];

    for (auto i = 0; i < count; i++)
    {
        bytes[i] = data.readByte();
    }

    return bytes;
}

string readString(Range)(ref Range data)
        if (isRandomAccessRange!(Unqual!(Range))
            && is(ElementType!Range == ubyte) && hasSlicing!Range)
{
    auto length = 0;
    ubyte[] chars;

    while (true)
    {
        auto lengthByte = data.readByte();

        if (length != 0 && lengthByte < 128)
        {
            break;
        }

        length = length << 8 | lengthByte;

        if (lengthByte < 128)
        {
            break;
        }
    }

    auto value = cast(string) data[0 .. length];
    data = data[length .. $];

    return value;
}

uint readInt(Range)(ref Range data)
        if (isRandomAccessRange!(Unqual!(Range))
            && is(ElementType!Range == ubyte) && hasSlicing!Range)
{
    auto value = littleEndianToNative!uint(data[0 .. 4]);
    data = data[4 .. $];
    return value;
}