# MECHWEAP.CPP / .HPP — reconstruction notes

`MechWeapon` (: PoweredSubsystem) is the weapon base: PPC/GaussRifle bind it via
Emitter, the SRMs via ProjectileWeapon/MissileLauncher. The resource streams
rechargeRate / weaponRange / damage / heatCostToFire (+ pip fields).

## Reconstructed

- Statics (ClassDerivations, DefaultData on Subsystem::MessageHandlers/
  AttributeIndex), ctor streaming the tuning fields, damageData prime.
- **View-fire gating (2026-07-21, the look-commit wave):** real `rearFiring` /
  `viewFireEnable` members (1995 binary @0x334/@0x3E0) + `IsRearFiring()` /
  `GetViewFireEnable()` / `SetViewFireEnable()`. The ctor resolves REAR-FIRING
  authentically (binary ctor tail @004b99a8): the mount SEGMENT site name
  (`owner->GetSegment(GetSegmentIndex())`) is tested for the 'b' (back) marker —
  only the back gun ports (`sitelbgunport`/`siterbgunport`) carry it. Spawn
  state = armed for the forward view. `Mech::CommitLookState` re-arms on every
  view change (see MECH.NOTES.md increment 7). Verified: the TEST.EGG mech's
  two rear lasers (ERMLaser_2/3) arm only in LOOK-BACK.

## Fire path (2026-07-21, Phase 5.3.8)

- **The authentic attribute table IS published** (binary @0x511890, IDs pinned):
  PercentDone 0x12 → rechargeLevel, **TriggerState 0x13 → fireImpulse** (the
  streamed per-mech fire-button mappings bind this ID — the real trigger
  wiring), DistanceToTarget 0x14, TargetWithinRange 0x15, WeaponRange 0x16 →
  effectiveRange, EstimatedReadyTime 0x1A, RearFiring 0x1B, WeaponState 0x1C →
  weaponAlarm. Pads bridge our chain gap 2..0x11 (parents publish nothing yet;
  they shrink to the authentic 0x0F..0x11 when the mechsub/heat/powersub
  attribute waves land — SENSOR.HPP pins PoweredSubsystem::NextAttributeID at
  0x0F). **Pads are LOAD-BEARING**: AttributeIndexSet::Build leaves uncovered
  gap slots as UNINITIALIZED GARBAGE (`new IndexEntry[entryCount]`, only
  inherited + listed entries written), so every ID up to the max must be
  covered or Find() on a gap ID returns a wild pointer. Pip* (0x17-0x19) are
  pads → rechargeLevel until the pip members are reconstructed.
- **Fire state machine members**: fireImpulse/previousFireImpulse (the trigger
  sample pair), rechargeLevel, rangeToTarget, effectiveRange,
  estimatedReadyTime, recoil, weaponAlarm (the state carrier: 0 Firing /
  2 Loaded / 3 Loading / 4 trigger-during-load). Spawn = charged + Loaded.
- **CheckFireEdge** (@004b9608): rising-edge on fireImpulse comparing BIT
  PATTERNS as signed ints — TriggerState carries raw ControlsButton ints
  (+(button+1) press / −(button+1) release); the release bit-pattern is a
  negative NaN as float, and an IEEE float compare would latch the detector
  shut after the first release (BT411 task #8). Int compare reproduces the
  binary's x87 semantics exactly.
- **ComputeOutputVoltage** (@004b9c9c): `rechargeLevel = (rechargeRate −
  recoil) / rechargeRate` — the recharge dial.
- **Emitter::EmitterSimulation** (PARTIAL, @004baa88) installed on every
  non-replicant energy weapon: Firing → discharge countdown →
  ResetFiringState(Loading); Loaded + trigger edge → viewFireEnable gate →
  FireWeapon; Loading → recoil decays over the authored RechargeRate seconds →
  Loaded. Deferred within it: the leading PoweredSubsystemSimulation electrical
  step, the destroyed/heat-failure/dead-mech hard gates, the TrackSeekVoltage
  generator charge integration (the partial uses the authored seconds
  directly), and the HasActiveTarget gate (targeting wave).
- **Emitter::FireWeapon** (PARTIAL, @004bace8): discharge bookkeeping (beam
  countdown re-arm, charge spent, recoil loaded). Deferred: the 0.5·V²·EC
  energy/damage/heat closed forms (need the electrical model), the heat dump
  (heat wave), the beam build + Damage submission (targeting + renderer).
- Emitter's index re-chained to MechWeapon's (ChargeLevel at the authentic
  0x1D past the table end); Emitter::DefaultData now binds
  MechWeapon::MessageHandlers.
- DEV hook `BT_FORCE_FIRE=1`: pulses the trigger whenever a weapon is Loaded →
  every armed weapon auto-fires at its authored cadence.

**VERIFIED headlessly**: forward view — PPC_1/2 + ERMLaser_1 cycle
FIRED→LOADED→FIRED at the authored 0.6 s discharge / 1 s recharge, rear lasers
silent; `BT_FORCE_LOOK=3` (look-behind) — ONLY ERMLaser_2/3 fire. The full
view-fire × fire-FSM interlock holds in both directions. Zero Fail. (SRM6s are
MissileLaunchers — the ballistic ProjectileWeaponSimulation is a later
increment.)

## Ballistic fire path (2026-07-21, Phase 5.3.9)

- **ProjectileWeaponSimulation** (PARTIAL, binary @004bbd04 — FULLY RECOVERED
  in the BT411 RE) installed on every non-replicant ballistic weapon.  The
  authentic FSM shape: one trigger-edge sample before the gates; gate 2 (the
  linked AmmoBin dry → pin NoAmmo(7) every frame); Loaded(2): edge →
  viewFireEnable gate → **the ammo pull happens in the CALLER** (a failed pull
  stays Loaded silently; a denied shot does the 4→2 DENIAL BLIP with no ammo
  pulled — early-returning gates from FireWeapon while the caller cycles the
  alarm is exactly the 1995 "denied shot fakes a full firing cycle" defect);
  granted → Firing(0) → FireWeapon → Loading(3) (or NoAmmo if the pull emptied
  the bin), recoil = rechargeRate; Loading(3): recoil bleeds → 0 → Loaded when
  a round is chambered, ComputeOutputVoltage animates the dial; Jammed(5) held
  at full recoil; **NoAmmo(7) is the roach-motel** (re-asserts unconditionally;
  only a mission reset leaves it).  Deferred inside: the leading electrical
  step, gate 1 (destroyed/FailureHeat/mech-disabled), magazine eject, the
  electrical-Ready recoil gate, the heat-scaled jam roll, HasActiveTarget.
- **AmmoBin feed interface**: `GetAmmoState()` (1 round-ready / 2 EMPTY),
  `FeedAmmo()` (pull one round; 0 when dry).  Feed pacing + cook-off join the
  heat wave.
- **ammoBinLink wiring**: the launcher ctor resolves the bin from the
  resource's `ammoBinIndex` (the bin's roster slot) via the owner's subsystem
  table — WIRE-VERIFIED: the raw stream carries 27/29, exactly the
  AmmoBinSRM6_1/2 slots.
- **Resource alignment (wire-verified)**: a raw-stream dump showed the
  ProjectileWeapon field block sits +3 ints past our staged struct — the
  MechWeapon resource ancestry runs three ints short (the pip-family fields,
  not yet broken out).  `resourceAlignPad[3]` re-aligns it; the phantom
  muzzleVelocity/missileCount tail fields were dropped (BT411's verified
  overlay ends at minJamChance; missileCount belongs to MissileLauncher's own
  extension and now reads its true 6).  The full resource-overlay verification
  (every ancestor struct byte-checked) is its own wave.
- MissileLauncher::FireWeapon PARTIAL (@004bcc60: authentically heat + the
  missileCount-salvo Missile spawn ONLY — spawn needs the entity/targeting
  waves).

**VERIFIED headlessly** (BT_FORCE_FIRE): bins resolve with the authored 24
rounds; SRM6s fire 6-missile salvos and reload at the authored 1 s cadence,
rounds counting 24→0; after the 24th salvo the launcher goes DRY and stays
silent across ~3,000 subsequent fire events while the energy weapons keep
cycling — the NoAmmo roach-motel holds.  Zero Fail.

## Still staged

- The Missile entity spawn/seeker, `SendDamage` (damage/networking),
  `CreateStreamedSubsystem` (tool-side model build), the jam roll
  (CheckForJam), magazine eject.
- ~~`MechWeapon::MessageHandlers` declared but not defined~~ — **FIXED
  2026-07-21**: it is now a real defined set (`(0, NULL,
  Subsystem::MessageHandlers)` — no own handlers yet, inherits the chain), and
  `MechWeapon::DefaultData` binds it. This mattered because the surviving CODE
  PPC.CPP binds the inherited name (`PPC::MessageHandlers`) into
  PPC::DefaultData, and a declared-but-undefined static links as a zero-filled
  common block — the same silent-NULL trap as the Emitter::AttributeIndex
  crash. Real weapon handlers (fire/damage messages) come with the combat wave
  (grow the table in place).

## 5.3.16 — targeting + damage delivery

- `HasActiveTarget()` = owner's target slot non-NULL (binary owner+0x388);
  `UpdateTargeting()` (@004b9bdc) refreshes rangeToTarget/targetWithinRange
  from `target->localOrigin` every FSM tick (both weapon families call it
  right after the trigger sample). The Loaded→Firing gate is now the authentic
  `viewFireEnable && HasActiveTarget()` — a denied pull is the one-frame blip.
- `SendDamage(target, damage)`: builds the engine 5-arg
  `Entity::TakeDamageMessage` (inflictor = our mech's EntityID) and Dispatches
  AT the target; the engine handler routes `damageZones[zone]->TakeDamage`.
  INTERIM zone pick = `Random(target->damageZoneCount)` — the authentic
  resolvers are the reticle aimed hit and the cylinder hit-location table
  (unaimed, zone −1 + the Mech TakeDamage override), both later waves.
- Salvo semantics (BT411-verified): **burstCount is NOT in the zone armor
  formula** — one message = one amount×scale application. MissileLauncher
  therefore dispatches ONE message PER MISSILE (each carrying the ctor's
  salvo-split amount, each on its own random zone); a single split message
  would under-deliver the salvo by the round count. Interim all-rounds-hit
  until the Missile entity flight/seeker wave.
- Live-verified (two-mech fight): PPC 11.77/hit (12×chargeRatio², type 4
  Energy), ER-M 3.43 (type 3 Laser), SRM6 5.83×6 (type 2 Explosive); repeat
  hits climb linearly; zones reach 1.0 Burning/Destroyed; no-target runs hold
  fire (0 FIRED across a 65s force-fire run without a target).

## 5.3.18a — salvo economy CORRECTED (BT411 task #62)

The 5.3.16 "one message per missile" loop was ~missileCount-times too lethal.
The arcade fires ONE cluster Missile per trigger and its zone damage lands
EXACTLY ONCE: damageData carries the ctor's salvo-split per-missile amount
with burstCount=missileCount (burstCount feeds only gyro bounce + splash
falloff — never the zone formula). MISLANCH now dispatches a single
SendDamage per salvo (verified 1:1 FIRED:[dmg]). The cluster SPLASH component
arrives with the Missile entity wave (proximity-fuse detonation).