--by pavetr.top/ds
-- Define ConVars for tracer settings
CreateClientConVar("tracer_hit_color", "0 255 0", true, false, "Tracer color on hit")
CreateClientConVar("tracer_miss_color", "255 0 0", true, false, "Tracer color on miss")
CreateClientConVar("tracer_thickness", "2", true, false, "Thickness of bullet tracers")
CreateClientConVar("tracer_alpha", "255", true, false, "Transparency of bullet tracers (0-255)")
CreateClientConVar("tracer_fade", "1", true, false, "Enable tracer fading (1 = Yes, 0 = No)")
CreateClientConVar("tracer_fade_seconds", "1", true, false, "Time for tracers to fade out")
CreateClientConVar("tracer_mat", "sprites/physbeam", true, false,"Material for the trail (some do not support color)")

tracerTable = tracerTable or {}

local function GetTracerColor(hit, alphaOverride)
    local colorConVar = hit and "tracer_hit_color" or "tracer_miss_color"
    local colorStr = GetConVar(colorConVar):GetString()
    local r, g, b = string.match(colorStr, "(%d+) (%d+) (%d+)")
    local alpha = alphaOverride or GetConVar("tracer_alpha"):GetInt()
    return Color(tonumber(r) or 255, tonumber(g) or 255, tonumber(b) or 255, alpha)
end

-- Bullet Tracer Hook
hook.Add("PlayerTraceAttack", "BulletTracer", function(ent, dmg, dir, trace)
    if not IsFirstTimePredicted() then return end

    local vHitPos = trace.HitPos
    local vSrc = trace.StartPos

    if IsValid(ent) and ent:IsPlayer() then
        local initialHealth = ent:Health()
        timer.Simple(0.02, function()
            if not IsValid(ent) then return end
            local newHealth = ent:Health()
            local didHit = newHealth < initialHealth
            local fadeTime = GetConVar("tracer_fade_seconds"):GetFloat()

            table.insert(tracerTable, {
                startPos = vSrc,
                endPos = vHitPos,
                timeLeft = fadeTime,
                maxTime = fadeTime,
                color = GetTracerColor(didHit),
                thickness = GetConVar("tracer_thickness"):GetFloat(),
                didHit = didHit
            })
        end)
    else
        local fadeTime = GetConVar("tracer_fade_seconds"):GetFloat()
        table.insert(tracerTable, {
            startPos = vSrc,
            endPos = vHitPos,
            timeLeft = fadeTime,
            maxTime = fadeTime,
            color = GetTracerColor(false),
            thickness = GetConVar("tracer_thickness"):GetFloat(),
            didHit = false
        })
    end
end)

-- Draw Tracers
hook.Add("PostDrawOpaqueRenderables", "DrawBulletTracers", function()
    if not tracerTable then return end

    local material = Material(GetConVar("tracer_mat"):GetString())
    render.SetMaterial(material)
    local fadeEnabled = GetConVar("tracer_fade"):GetBool()

    for i = #tracerTable, 1, -1 do
        local tracer = tracerTable[i]
        local fadeFactor = fadeEnabled and (tracer.timeLeft / tracer.maxTime) or 1
        local alpha = GetConVar("tracer_alpha"):GetInt() * fadeFactor
        local color = GetTracerColor(tracer.didHit, alpha)

        render.StartBeam(2)
        render.AddBeam(tracer.startPos, tracer.thickness, 0, color)
        render.AddBeam(tracer.endPos, tracer.thickness, 1, color)
        render.EndBeam()

        if fadeEnabled then
            tracer.timeLeft = tracer.timeLeft - FrameTime()
            if tracer.timeLeft <= 0 then
                table.remove(tracerTable, i)
            end
        end
    end
end)