require 'luabit.bit';
require 'luabit.hex';

do

local function shift(s)
    s1 = tonumber((string.sub(s, 1, 2)), 16);
    s2 = bit.blshift(tonumber((string.sub(s, 3, 4)), 16), 8);
    s3 = bit.blshift(tonumber((string.sub(s, 5, 6)), 16), 16);
    s4 = bit.blshift(tonumber((string.sub(s, 7, 8)), 16), 24);
    sa = bit.bor(bit.bor(bit.bor(s1, s2), s3), s4);
    return sa;
end

local function bitwise(m)
    s1 = shift(string.sub(m, 1, 8));
    s2 = shift(string.sub(m, 9, 16));
    s3 = shift(string.sub(m, 17, 24));
    s4 = shift(string.sub(m, 25, 32));
    sa = s1 + s2 + s3 + s4;
    return sa;
end

local function str2point(str)
    md5 = ngx.md5(str);
    point = bitwise(md5);
    return point;
end


-- sps = aring
-- sp = point
local function search(sp, sps, pstart, pend, n)
    n = n + 1;
    local mid, mod = math.modf((pstart + pend) / 2);
    if n > 20 then
        ngx.log(ngx.ERR, 'the point ' .. sp .. ' cycle index exceed 20');
        ngx.exit(509);
    end
    if sps[mid] >= sp and sps[mid - 1] < sp then
        return sps[mid];
    elseif sps[mid + 1] >= sp and sps[mid] < sp then
        return sps[mid + 1];
    elseif sps[mid] > sp then
        pend = mid;
        return search(sp, sps, pstart, pend, n);
    elseif sps[mid] < sp then
        pstart = mid;
        return search(sp, sps, pstart, pend, n);
    end
end

-- fps = points
-- frs = rings
-- fnode = node name
local function findhost(fp, fps, ffls, fsgls, fls, frs, fnode)
    local fflag = ffls.get(fnode);
    if fflag == 's' then
        --ngx.say('single <br>');
        return fsgls.get(fnode);
    elseif fflag == 'h' then
        local ps = fps.get(fnode);
        local fend = table.getn(ps);

        if fp <= ps[1] or ps[fend] < fp then
            return frs.get(fnode).get(ps[1]);
        else
            tp = search(fp, ps, 1, fend, 0);
            if tp ~= nil then
                return frs.get(fnode).get(tp);
            else
                ngx.log(ngx.ERR, 'search ring error ' .. fp .. '<br>');
            end
        end
    elseif fflag == 'l' then
        floops = fls.get(fnode);
        total = table.getn(floops);
        math.randomseed(os.time());
        rp = math.random(1, total);
        return floops[rp];
    end
end

ring = {
    shift = shift,
    bitwise = bitwise,
    str2point = str2point,
    findhost = findhost,
}

end