--[[
    When an object has a different entrance and exit surface material, the damage lost is calculated using the average resistance of the two.

    penmod: How easy it is for a bullet to go through the material (0.001 to 1.0).
    dmgmod: How much of the damaging power of the bullet is preserved while going through the material (0.001 to 1.0).
]]

local mat_translation = {
    [MAT_CONCRETE] = {
        name = "concrete",
        penmod = 0.5,
        dmgmod = 0.25
    },
    [MAT_DIRT] = {
        name = "dirt",
        penmod = 0.6,
        dmgmod = 0.3
    },
    [MAT_EGGSHELL] =    "The egg sacs in the antlion tunnels in HL2: EP2",
    [MAT_FLESH] = {
        name = "flesh",
        penmod = 0.9,
        dmgmod = 0.5
    },
    [MAT_GRATE] =    {
        name = "grate",
        penmod = 0.95,
        dmgmod = 0.99
    },
    [MAT_CLIP] = "Unused",
    [MAT_SNOW] = {
        name = "snow",
        penmod = 0.85,
        dmgmod = 0.5
    },
    [MAT_PLASTIC] =    {
        name = "plastic",
        penmod = 0.3,
        dmgmod = 0.25
    },
    [MAT_METAL] = {
        name = "metal",
        penmod = 0.4,
        dmgmod = 0.3
    },
    [MAT_SAND] = {
        name = "sand",
        penmod = 0.3,
        dmgmod = 0.25
    },
    [MAT_FOLIAGE] = {
        name = "foliage",
        penmod = 0.95,
        dmgmod = 0.5
    },
    [MAT_COMPUTER] = {
        name = "computer",
        penmod = 0.4,
        dmgmod = 0.45
    },
    [MAT_SLOSH] =    {
        name = "Water, slime",
        penmod = 0.3
    },
    [MAT_TILE] = {
        name = "tile",
        penmod = 0.7,
        dmgmod = 0.3
    },
    [MAT_VENT] = {
        name = "vent",
        penmod = 0.6,
        dmgmod = 0.45
    },
    [MAT_WOOD] = {
        name = "wood",
        penmod = 0.9,
        dmgmod = 0.6
    },
    [MAT_DEFAULT] =    {
        name = "default",
        penmod = 1.0,
        dmgmod = 0.5
    },
    [MAT_GLASS] = {
        name = "glass",
        penmod = 0.99,
        dmgmod = 0.5
    },
    [MAT_WARPSHIELD] =    "\"wierd-looking jello effect for advisor shield.\"",
}
mat_translation[MAT_GRASS] = table.Copy(mat_translation[MAT_DIRT])
mat_translation[MAT_GRASS].name = "grass"
mat_translation[MAT_ALIENFLESH] = table.Copy(mat_translation[MAT_FLESH])
mat_translation[MAT_ALIENFLESH].name = "alien flesh"
mat_translation[MAT_BLOODYFLESH] = table.Copy(mat_translation[MAT_FLESH])
mat_translation[MAT_BLOODYFLESH].name = "bloody flesh"
mat_translation[MAT_ANTLION] =    table.Copy(mat_translation[MAT_FLESH])
mat_translation[MAT_ANTLION].name = "antlion"

local function calc_lost_damage(wep, enter_trace, exit_trace, currentDamage)
    local enter_data = mat_translation[enter_trace.MatType] or mat_translation[MAT_DEFAULT]
    local exit_data = mat_translation[exit_trace.MatType] or mat_translation[MAT_DEFAULT]

    local is_solid_surf = bit.band(bit.rshift(enter_trace.Contents, 3), CONTENTS_SOLID) ~= 0
    local is_light_surf = bit.band(bit.rshift(enter_trace.SurfaceFlags, 7), SURF_LIGHT) ~= 0

    local thickness, modifier, lostDamage, finalDamageModifier, combinedPenetrationModifier

    if enter_trace.MatType == MAT_GLASS or enter_trace.MatType == MAT_GRATE then
        combinedPenetrationModifier = 3
        finalDamageModifier = .05
    elseif is_solid_surf or is_light_surf then
        combinedPenetrationModifier = 1
        finalDamageModifier = .16
    else
        combinedPenetrationModifier = (enter_data.penmod + exit_data.penmod) / 2
        finalDamageModifier = .16
    end

    if enter_trace.MatType == exit_trace.MatType then
        if enter_trace.MatType == MAT_DIRT or enter_trace.MatType == MAT_WOOD then
            combinedPenetrationModifier = 3
        elseif enter_trace.MatType == MAT_PLASTIC then
            combinedPenetrationModifier = 2
        end
    end

    thickness = (exit_trace.HitPos - enter_trace.HitPos):LengthSqr()
    modifier = math.max(1 / combinedPenetrationModifier, 0)

    local penetrationPower = wep.PenetrationPower or 1
    lostDamage = math.max(
        ((modifier * thickness) / 24)
        + ((currentDamage * finalDamageModifier)
            + (math.max(3.75 / penetrationPower, 0) * 3 * modifier)), 0)

    if lostDamage > currentDamage then
        return currentDamage
    end

    return lostDamage
end

function SWEP:BulletCallback(atk, tr, dmg, pens)
    if CLIENT and not IsFirstTimePredicted() then return end

    local impacts = sv_showimpacts:GetInt()
    local penetrations = sv_showimpacts_penetration:GetInt()
    pens = pens or 0

    if impacts == 1 or (CLIENT and impacts == 2) or (SERVER and impacts == 3) then
        debugoverlay.Box(tr.HitPos, Vector(1,1,1), -Vector(1,1,1), sv_showimpacts_time:GetFloat(), CLIENT and Color(255,0,0,128) or Color(0,0,255,128))
    end

    local mat = mat_translation[tr.MatType] or mat_translation[MAT_DEFAULT]
    if SERVER and penetrations ~= 0 then
        local nice_dist = util.NiceMetric(util.HUtoCM(tr.HitPos:Distance(tr.StartPos)))

        debugoverlay.EntityTextAtPosition(tr.HitPos, -2, mat.name, sv_showimpacts_time:GetFloat(), Color(0,255,0, 64))
        debugoverlay.EntityTextAtPosition(tr.HitPos, 0, "^", sv_showimpacts_time:GetFloat(), Color(255, 154, 0, 64))

        if penetrations == 2 then
            debugoverlay.EntityTextAtPosition(tr.HitPos, 1, dmg:GetDamage(), sv_showimpacts_time:GetFloat(), Color(255,0,0))
            debugoverlay.EntityTextAtPosition(tr.HitPos, 2, nice_dist, sv_showimpacts_time:GetFloat(), Color(255, 129, 62))
        else
            debugoverlay.EntityTextAtPosition(tr.HitPos, 1, string.format("DAMAGE APPLIED:  %d", dmg:GetDamage()), sv_showimpacts_time:GetFloat(), Color(255,0,0))
            debugoverlay.EntityTextAtPosition(tr.HitPos, 2, string.format("TOTAL DISTANCE:  %s", nice_dist), sv_showimpacts_time:GetFloat(), Color(255, 129, 62))
        end
    end

    if pens > 3 then return end
    if tr.HitSky then return end

    -- Bullet Penetration
    local dir = tr.Normal
    local back_tr

    local filter = not tr.Entity:IsWorld() and tr.Entity or nil
    for i = 1, 1000 do
        local new_tr = util.TraceLine({
            endpos = tr.HitPos,
            start = tr.HitPos + dir * i,
            --filter = filter
        })

        --print(new_tr.Entity, new_tr.HitNoDraw, new_tr.StartSolid, not (new_tr.HitNoDraw or new_tr.StartSolid))

        if not (new_tr.HitNoDraw or new_tr.StartSolid) then
            --print("found back_tr", new_tr.Entity)
            back_tr = new_tr
            break
        end
    end

    if not back_tr then return end
    local back_mat = mat_translation[back_tr.MatType] or mat_translation[MAT_DEFAULT]

    local original_damage = dmg:GetDamage()
    local dmg_lost = calc_lost_damage(self, tr, back_tr, original_damage)
    dmg:SetDamage(original_damage - dmg_lost)

    if dmg:GetDamage() <= 0 then
        --print("STOPPED!")
        return
    end

    if SERVER and penetrations ~= 0 then
        local nice_dist = util.NiceMetric(util.HUtoCM(tr.HitPos:Distance(back_tr.StartPos)))

        debugoverlay.Line(tr.HitPos, back_tr.StartPos, sv_showimpacts_time:GetFloat(), Color(16,192,192), true)

        if penetrations == 2 then
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -3, nice_dist, sv_showimpacts_time:GetFloat(), Color(255,128,128))
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -2, string.format("%d", dmg:GetDamage() - original_damage), sv_showimpacts_time:GetFloat(), Color(255,0,0, 64))
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -1, back_mat.name, sv_showimpacts_time:GetFloat(), Color(32,128,196, 64))
        else
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -3, string.format("THICKNESS: %s", nice_dist), sv_showimpacts_time:GetFloat(), Color(255,128,128))
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -2, string.format("LOST DAMAGE: %d", original_damage - dmg:GetDamage()), sv_showimpacts_time:GetFloat(), Color(255,0,0, 64))
            debugoverlay.EntityTextAtPosition(back_tr.HitPos, -1, back_mat.name, sv_showimpacts_time:GetFloat(), Color(32,128,196, 64))
        end
    end

    local data = EffectData()
    data:SetOrigin(back_tr.HitPos)
    data:SetStart(back_tr.StartPos)
    data:SetSurfaceProp(back_tr.SurfaceProps)
    data:SetDamageType(dmg:GetDamageType())
    data:SetHitBox(back_tr.HitBox)
    data:SetEntity(back_tr.Entity)

    if SERVER or (CLIENT and IsFirstTimePredicted()) then
        util.Effect("Impact", data, not game.SinglePlayer())
    end

    self:FireBullets({
        Src = back_tr.HitPos,
        Dir = dir,
        Num = 1,
        AmmoType = self.Primary.Ammo,
        Tracer = 0,
        Attacker = self:GetOwner(),
        Spread = vector_origin,
        Damage = dmg:GetDamage(),
        Distance = self.BulletDistance,
        Callback = function(atk, tr, dmg) self:BulletCallback(atk, tr, dmg, pens + 1) end
    })
end