GMod Achievement System

local curid = 0
local bits = 0
local nettable = {}

-- FIXME: Put into separate PR
function math.BitCount( num )
    if ( num == 0 ) then
        return 0
    end

    return math.floor( math.log( num, 2 ) ) + 1
end

if ( SERVER ) then
    achievements = {}

    util.AddNetworkString( "GMod_Achievements" )
    util.AddNetworkString( "GMod_Achievements_Sync" )
    util.AddNetworkString( "GMod_Achievements_New" )


    -- Shared functions --

    function achievements.Register( name, func --[[= nil]], update --[[= true]] )
        -- FIXME: Typecheck func

        if ( nettable[ name ] == nil ) then
            nettable[ name ] = curid

            if ( func != nil ) then
                nettable[ curid ] = func
            end

            bits = math.BitCount( curid )
            curid = curid + 1

            if ( update == nil || update ) then
                net.Start( "GMod_Achievements_New" )
                    net.WriteString( name )
                net.Broadcast()
            end
        else
            nettable[ nettable[ name ] ] = func
        end
    end

    function achievements.Exists( name )
        return nettable[ name ] != nil
    end

    function achievements.GetFunction( name )
        local id = nettable[ name ]

        if ( id == nil ) then
            return nil
        end

        return nettable[ id ]
    end


    -- Server functions --

    function achievements.Call( name, plys --[[= player.GetAll()]], ... )
        -- FIXME: Typecheck plys

        local id = nettable[ name ]

        if ( id == nil ) then
            ErrorNoHalt( string.format( "Attempted to call unregistered achievement '%s'", name ) )
            return false
        end

        net.Start( "GMod_Achievements" )
            net.WriteUInt( id, bits )

            local func = nettable[ id ]

            if ( func != nil ) then
                func( ... )
            end
        if ( plys == nil ) then
            net.Broadcast()
        else
            net.Send( plys )
        end

        return true
    end

    function achievements.Sync( plys --[[= player.GetAll()]] )
        -- FIXME: Typecheck plys

        net.Start( "GMod_Achievements_Sync" )
            net.WriteUInt( curid, 32 )

            for id = 0, curid - 1 do
                net.WriteString( nettable[ id ] )
            end
        if ( plys == nil ) then
            net.Broadcast()
        else
            net.Send( plys )
        end
    end

    -- FIXME: https://github.com/Facepunch/garrysmod-requests/issues/718
    hook.Add( "PlayerInitialSpawn", "GMod_Achievements", function( ply )
        local id = "GMod_Achievements_" .. ply:SteamID64()

        hook.Add( "SetupMove", id, function( pply, _, cmd )
            if ( !ply:IsValid() ) then
                hook.Remove( "SetupMove", id )
            elseif ( pply == ply && cmd:IsForced() ) then
                achievements.Sync( ply )
                hook.Remove( "SetupMove", id )
            end
        end)
    end )
else
    local funcs = {}


    -- Shared functions --

    function achievements.Register( name, func --[[= nil]] )
        -- FIXME: Typecheck func

        funcs[ name ] = func
        local id = nettable[ name ]

        if ( id ~= nil ) then
            nettable[ id ] = func
        end
    end

    function achievements.Exists( name )
        return nettable[ name ] != nil || funcs[ name ] != nil
    end

    function achievements.GetFunction( name )
        return funcs[ name ]
    end


    -- Client functions --

    function achievements.Pooled( name )
        return nettable[ name ] != nil
    end

    net.Receive( "GMod_Achievements", function()
        local func = nettable[ net.ReadUInt( bits ) ]

        if ( func != nil ) then
            func()
        end
    end )

    net.Receive( "GMod_Achievements_Sync", function()
        curid = net.ReadUInt( 32 )

        for id = 0, curid - 1 do
            local name = net.ReadString()
            nettable[ name ] = id
            nettable[ id ] = funcs[ name ]
        end
    end )

    net.Receive( "GMod_Achievements_New", function()
        bits = math.BitCount( curid )

        local name = net.ReadString()
        nettable[ name ] = curid
        nettable[ curid ] = funcs[ name ]

        curid = curid + 1
    end )
end

achievements.Register( "BalloonPopped", Either( CLIENT, achievements.BalloonPopped, nil ) )
achievements.Register( "EatBall", Either( CLIENT, achievements.EatBall, nil ) )
achievements.Register( "SpawnedNPC", Either( CLIENT, achievements.SpawnedNPC, nil ) )
achievements.Register( "SpawnedProp", Either( CLIENT, achievements.SpawnedProp, nil ) )
achievements.Register( "SpawnedRagdoll", Either( CLIENT, achievements.SpawnedRagdoll, nil ) )

achievements.Register( "Remover", Either( CLIENT, function()
    for i = 0, net.ReadUInt( 32 ) do
        achievements.Remover()
    end
end, function( count --[[= 1]] )
    if ( isnumber( count ) ) then
        net.WriteUInt( count, 32 )
    else
        net.WriteUInt( 1, 32 )
    end
end ) )