mech nitrogen filtering 2 (#19868)

* target oxygen logic

* filter out nitrogen when low on oxygen

* vvrw and datafield for everything

* :trollface:

* bruh does work

* tagless chicken

* move into atmos, make it not depend on mech

* update mech prototype

---------

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Atmos/Components/AirFilterComponent.cs

@@ -0,0 +1,46 @@
+using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Atmos;
+
+namespace Content.Server.Atmos.Components;
+
+/// <summary>
+/// This is basically a reverse scrubber but using <see cref="GetFilterAirEvent"/>.
+/// </summary>
+[RegisterComponent, Access(typeof(AirFilterSystem))]
+public sealed partial class AirFilterComponent : Component
+{
+    /// <summary>
+    /// Gases that will be filtered out of internal air
+    /// </summary>
+    [DataField(required: true)]
+    public HashSet<Gas> Gases = new();
+
+    /// <summary>
+    /// Gases that will be filtered out of internal air to maintain oxygen ratio.
+    /// When oxygen is below <see cref="TargetOxygen"/>, these gases will be filtered instead of <see cref="Gases"/>.
+    /// </summary>
+    [DataField(required: true)]
+    public HashSet<Gas> OverflowGases = new();
+
+    /// <summary>
+    /// Minimum oxygen fraction before it will start removing <see cref="OverflowGases"/>.
+    /// </summary>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public float TargetOxygen = 0.21f;
+
+    /// <summary>
+    /// Gas to consider oxygen for <see cref="TargetOxygen"/> and <see cref="OverflowGases"/> logic.
+    /// </summary>
+    /// <remarks>
+    /// For slime you might want to change this to be nitrogen, and overflowgases to remove oxygen.
+    /// However theres still no real danger since standard atmos is mostly nitrogen so nitrogen tends to 100% anyway.
+    /// </remarks>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public Gas Oxygen = Gas.Oxygen;
+
+    /// <summary>
+    /// Fraction of target volume to transfer every second.
+    /// </summary>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public float TransferRate = 0.1f;
+}

Content.Server/Atmos/Components/AirIntakeComponent.cs

@@ -0,0 +1,29 @@
+using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Atmos;
+
+namespace Content.Server.Atmos.Components;
+
+/// <summary>
+/// This is basically a siphon vent for <see cref="GetFilterAirEvent"/>.
+/// </summary>
+[RegisterComponent, Access(typeof(AirFilterSystem))]
+public sealed partial class AirIntakeComponent : Component
+{
+    /// <summary>
+    /// Target pressure change for a single atmos tick
+    /// </summary>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public float TargetPressureChange = 5f;
+
+    /// <summary>
+    /// How strong the intake pump is, it will be able to replenish air from lower pressure areas.
+    /// </summary>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public float PumpPower = 2f;
+
+    /// <summary>
+    /// Pressure to intake gases up to, maintains pressure of the air volume.
+    /// </summary>
+    [DataField, ViewVariables(VVAccess.ReadWrite)]
+    public float Pressure = Atmospherics.OneAtmosphere;
+}