LUA Lag Compensation version 0.4

--LUA Lag Compensation version 0.3 by FlooD
--thx to Jermuk for his custom server, which first encouraged me to make lag compensation.
--thx to lasthope and def3ct for initial testing.
--thx to 3rr0r for ideas and suggestions for refining the code.

parse("mp_damagefactor 0")

BUFFER_SIZE = 25
frame = 0

buffer = {}
buffer[1] = {} --x buffer
buffer[2] = {} --y buffer

function clearbuffer(id)
    buffer[1][id] = {}
    buffer[2][id] = {}
end

for i = 1, 32 do
    clearbuffer(i)
end

addhook("leave", "clearbuffer")
addhook("die", "clearbuffer")

addhook("always", "updatebuffer")
function updatebuffer()
    frame = frame + 1
    for i = 1, 32 do
        buffer[1][i][frame], buffer[2][i][frame] = player(i, "x"), player(i, "y")
        buffer[1][i][frame - BUFFER_SIZE], buffer[2][i][frame - BUFFER_SIZE] = nil, nil
    end
end

addhook("attack", "onattack")
function onattack(id)
    local wpn = player(id, "weapon")

    local rot = player(id, "rot")
    local start_x = player(id, "x")
    local start_y = player(id, "y")
    local end_x = start_x + (3 * itemtype(wpn, "range")) * math.sin(math.rad(rot))
    local end_y = start_y - (3 * itemtype(wpn, "range")) * math.cos(math.rad(rot))
    local tile_x = math.floor(start_x / 32)
    local tile_y = math.floor(start_y / 32)
    --the following huge if statement will set tile_x and tile_y to the first wall the bullet hits.
    if rot > 0 and rot < 90 then
        while (not tile(tile_x, tile_y, "wall")) do
            if intersect(start_x, start_y, end_x, end_y, topixel(tile_x + 1), topixel(tile_y), 32) then
                tile_x = tile_x + 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x), topixel(tile_y - 1), 32) then
                tile_y = tile_y - 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x + 1), topixel(tile_y - 1), 32) then
                tile_x, tile_y = tile_x + 1, tile_y - 1
            else --unlikely or impossible, but here for safety.
                break
            end
        end
    elseif rot > 90 and rot < 180 then
        while (not tile(tile_x, tile_y, "wall")) do
            if intersect(start_x, start_y, end_x, end_y, topixel(tile_x + 1), topixel(tile_y), 32) then
                tile_x = tile_x + 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x), topixel(tile_y + 1), 32) then
                tile_y = tile_y + 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x + 1), topixel(tile_y + 1), 32) then
                tile_x, tile_y = tile_x + 1, tile_y + 1
            else
                break
            end
        end
    elseif rot > -180 and rot < -90 then
        while (not tile(tile_x, tile_y, "wall")) do
            if intersect(start_x, start_y, end_x, end_y, topixel(tile_x - 1), topixel(tile_y), 32) then
                tile_x = tile_x - 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x), topixel(tile_y + 1), 32) then
                tile_y = tile_y + 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x - 1), topixel(tile_y + 1), 32) then
                tile_x, tile_y = tile_x - 1, tile_y + 1
            else
                break
            end
        end
    elseif rot > -90 and rot < 0 then
        while (not tile(tile_x, tile_y, "wall")) do
            if intersect(start_x, start_y, end_x, end_y, topixel(tile_x - 1), topixel(tile_y), 32) then
                tile_x = tile_x - 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x), topixel(tile_y - 1), 32) then
                tile_y = tile_y - 1
            elseif intersect(start_x, start_y, end_x, end_y, topixel(tile_x - 1), topixel(tile_y - 1), 32) then
                tile_x, tile_y = tile_x - 1, tile_y - 1
            else
                break
            end
        end
    elseif rot == 0 then
        while not tile(tile_x, tile_y, "wall") and topixel(tile_y) >= end_y do
            tile_y = tile_y - 1
        end
    elseif rot == 90 then
        while not tile(tile_x, tile_y, "wall") and topixel(tile_x) <= end_x do
            tile_x = tile_x + 1
        end
    elseif rot == 180 then
        while not tile(tile_x, tile_y, "wall") and topixel(tile_y) <= end_y do
            tile_y = tile_y + 1
        end
    elseif rot == -90 then
        while not tile(tile_x, tile_y, "wall") and topixel(tile_x) >= end_x do
            tile_x = tile_x - 1
        end
    end

    local temp_x, temp_y = end_x, end_y
    end_x, end_y = intersect(start_x, start_y, temp_x, temp_y, topixel(tile_x), topixel(tile_y), 32)

    if not (end_x  or end_y) then --unlikely or impossible, but here for safety.
        end_x, end_y = temp_x, temp_y
    end

    local frames = math.floor(player(id, "ping") / 20)
    if frames > (BUFFER_SIZE - 1) then
        frames = (BUFFER_SIZE - 1)
    end

    local alive = player(0, "tableliving")
    for _, v in ipairs(alive) do
        if ((game("sv_friendlyfire") == 1) or (player(v, "team") ~= player(id, "team"))) and (v ~= id) and intersect(start_x, start_y, end_x, end_y, buffer[1][v][frame - frames], buffer[2][v][frame - frames], 24) then
            local newarmor = player(v, "armor") - itemtype(wpn, "dmg")
            if newarmor < 0 then
                newarmor = 0
            end
            local newhealth = player(v, "health") - (itemtype(wpn, "dmg") - math.floor(game("mp_kevlar") * (player(v, "armor") - newarmor)))
            if newhealth > 0 then
                parse("sethealth "..v.." "..newhealth)
                parse("setarmor "..v.." "..newarmor)
            else
                parse("customkill "..id.." "..itemtype(wpn, "name").." "..v)
            end
        end
    end
end

function topixel(tile)
    return (tile * 32) + 16
end

function isinorder(s, i, e)
    return (e >= i and i >= s) or (e <= i and i <= s)
end

function intersect(sx, sy, ex, ey, bx, by, bl)
    bl = bl / 2

    if math.abs(sx - bx) <= bl and math.abs(sy - by) <= bl then
        if math.abs(ex - bx) <= bl and math.abs(ey - by) <= bl then
            return ex, ey
        else
            return intersect(ex, ey, sx, sy, bx, by, bl)
        end
    end

    local i_x, i_y

    if ey > sy then
        i_y = by - bl
    elseif ey < sy then
        i_y = by + bl
    end
    if i_y and isinorder(sy, i_y, ey) then
        i_x = ((ex - sx) * i_y + (sx * ey - sy * ex)) / (ey - sy)
        if math.abs(i_x - bx) <= bl and isinorder(sx, i_x, ex) then
            return i_x, i_y
        end
    end

    if ex > sx then
        i_x = bx - bl
    elseif ex < sx then
        i_x = bx + bl
    end
    if i_x and isinorder(sx, i_x, ex) then
        i_y = ((ey - sy) * i_x + (sy * ex - sx * ey)) / (ex - sx)
        if math.abs(i_y - by) <= bl and isinorder(sy, i_y, ey) then
            return i_x, i_y
        end
    end
end