Add AMM RDII integration

src/engine/core/SWMMEngine.cpp

@@ -1220,6 +1220,17 @@ void SWMMEngine::stepRouting(double dt_routing) noexcept {
         rdii_.applyRdiiInflows(ctx_);
     }
 
+    // B2a2. RDII inflows (antecedent moisture model) — AMM method
+    if (ctx_.options.rdii_method == RdiiMethod::AMM && amm_.componentCount() > 0) {
+        double avg_rainfall = 0.0;
+        for (int g = 0; g < ctx_.n_gages(); ++g) {
+            avg_rainfall += ctx_.gages.rainfall[static_cast<std::size_t>(g)];
+        }
+        if (ctx_.n_gages() > 0) avg_rainfall /= ctx_.n_gages();
+        double air_temp = climate_.temperature;   // current air temperature (deg F)
+        amm_.computeAll(ctx_, avg_rainfall, air_temp, dt_routing);
+    }
+
     // B2b. Interface file inflows (from upstream model coupling)
     iface_.readInflows(ctx_, ctx_.current_date);
 
@@ -2446,6 +2457,9 @@ void SWMMEngine::initHydraulics() noexcept {
     // 10a. RDII solver: initialize unit hydrograph groups
     rdii_.init(ctx_);
 
+    // 10a2. AMM solver: initialize antecedent moisture model groups
+    amm_.init(ctx_);
+
     // 10b. Non-conduit hydraulic structures (pumps, orifices, weirs, outlets)
     hydstruct_.init(ctx_);
 

src/engine/core/SWMMEngine.hpp

@@ -49,6 +49,7 @@
 #include "../hydrology/LID.hpp"
 #include "../hydrology/Inflow.hpp"
 #include "../hydrology/RDII.hpp"
+#include "../hydrology/AMM.hpp"
 #include "../quality/QualityRouting.hpp"
 #include "../quality/Landuse.hpp"
 #include "../controls/Controls.hpp"
@@ -236,6 +237,7 @@ class SWMMEngine {
     controls::ControlEngine      controls_;     ///< Control rule evaluation
     inflow::InflowSolver         inflow_;       ///< External + DWF inflows
     rdii::RDIISolver             rdii_;         ///< RDII (unit hydrograph convolution)
+    amm::AMMSolver               amm_;          ///< AMM (antecedent moisture model)
     exfil::ExfilSolver           exfil_;        ///< Storage node exfiltration
     inlet::InletSolver           inlet_;        ///< Street inlet capture
     std::vector<int>             culvert_links_;///< Pre-built culvert link indices (avoid per-timestep alloc)

src/engine/core/SimulationContext.hpp

@@ -313,6 +313,7 @@ struct SimulationContext {
     DwfData          dwf_inflows;
     RDIIAssignData   rdii_assigns;
     UnitHydData      unit_hyds;      ///< Parsed [HYDROGRAPHS] data
+    AMMAssignData    amm_assigns;
     PatternData      patterns;
 
     // =========================================================================

src/engine/core/SimulationOptions.hpp

@@ -35,6 +35,17 @@ namespace openswmm {
 // Enumerators matching legacy SWMM enums.h
 // ============================================================================
 
+/**
+ * @brief RDII computation method.
+ *
+ * RTK uses the traditional 3-triangle unit hydrograph convolution.
+ * AMM uses the Antecedent Moisture Model (Edgren et al., JWMM C525).
+ */
+enum class RdiiMethod : int {
+    RTK = 0,  ///< Traditional RTK unit hydrograph (default)
+    AMM = 1   ///< Antecedent Moisture Model
+};
+
 /**
  * @brief Flow unit systems.
  * @see Legacy: FlowUnitsType in enums.h
@@ -293,6 +304,9 @@ struct SimulationOptions {
     /** @brief Ignore RDII. */
     bool ignore_rdii = false;
 
+    /** @brief RDII computation method (RTK or AMM). */
+    RdiiMethod rdii_method = RdiiMethod::RTK;
+
     /** @brief Ignore routing. */
     bool ignore_routing = false;
 

src/engine/data/InflowData.hpp

@@ -17,6 +17,7 @@
 
 #include <vector>
 #include <string>
+#include <unordered_map>
 
 namespace openswmm {
 
@@ -88,6 +89,7 @@ struct RDIIAssignData {
     }
 };
 
+// ============================================================================
 // ============================================================================
 // Unit Hydrograph data (from [HYDROGRAPHS] section)
 // ============================================================================
@@ -122,6 +124,44 @@ struct UnitHydData {
     void add(const UnitHydEntry& e) { entries.push_back(e); }
 };
 
+// ============================================================================
+// AMM assignments (from [AMM] section)
+// ============================================================================
+
+struct AMMAssignData {
+    int count() const { return static_cast<int>(node_idx.size()); }
+
+    std::vector<int>         node_idx;    ///< Target node
+    std::vector<std::string> amm_name;    ///< AMM component group name
+    std::vector<double>      sewer_area;  ///< Tributary sewer area
+
+    void add(int ni, const std::string& name, double area) {
+        node_idx.push_back(ni); amm_name.push_back(name);
+        sewer_area.push_back(area);
+    }
+
+    /// Raw component parameter definition (parsed from [AMM] section).
+    /// Transferred to AMMSolver::addComponentParams() during init().
+    struct ComponentDef {
+        double area      = 0.0;
+        double RD        = 0.0;
+        double PAT       = 0.0;
+        double HHL       = 3600.0;
+        double AMHL      = 28800.0;
+        double cold_SHCF = 0.0;
+        double hot_SHCF  = 0.0;
+        double cold_temp = 30.0;
+        double hot_temp  = 70.0;
+        double TAT       = 0.0;
+        bool   is_baseflow = false;
+        double cold_R    = 0.0;
+        double hot_R     = 0.0;
+    };
+
+    /// Map: component name → parsed parameters (populated by handle_amm).
+    std::unordered_map<std::string, ComponentDef> component_defs;
+};
+
 // ============================================================================
 // Time patterns (from [PATTERNS] section)
 // ============================================================================