From ac753a4f064320e17eda5ce8fe3d50c0b8686d33 Mon Sep 17 00:00:00 2001
From: Matthieu Monsch <matthieu.monsch@gmail.com>
Date: Sat, 11 Nov 2023 17:41:55 -0800
Subject: [PATCH] Add addon callback support

---
 packages/highs-addon/index.d.ts           | 32 +++++++++++++++++
 packages/highs-addon/src/solver.cc        | 43 +++++++++++++++++++++++
 packages/highs-addon/src/solver.h         |  4 +++
 packages/highs-solver/test/solver.test.ts |  7 ++++
 4 files changed, 86 insertions(+)

diff --git a/packages/highs-addon/index.d.ts b/packages/highs-addon/index.d.ts
index f2f176f..c57eef2 100644
--- a/packages/highs-addon/index.d.ts
+++ b/packages/highs-addon/index.d.ts
@@ -22,6 +22,10 @@ export declare class Solver {
     weights: Matrix
   ): void;
 
+  setCallback(cb: Callback): void;
+  startCallback(tp: CallbackType): void;
+  stopCallback(tp: CallbackType): void;
+
   run(cb: (err: Error) => void): void;
   getModelStatus(): ModelStatus;
   getInfo(): Info;
@@ -168,3 +172,31 @@ export type SolutionStatus = number;
 
 // https://github.com/ERGO-Code/HiGHS/blob/master/src/lp_data/HConst.h#L127
 export type SolutionStyle = number;
+
+// https://ergo-code.github.io/HiGHS/stable/callbacks/
+export type Callback = (inputs: CallbackInputs) => CallbackOutputs;
+
+// https://github.com/ERGO-Code/HiGHS/blob/master/src/lp_data/HConst.h#L209
+export type CallbackType = number;
+
+export interface CallbackInputs {
+  // Simplex interrupt
+  readonly simplex_iteration_count?: number;
+  // IPM interrupt
+  readonly ipm_iteration_count?: number;
+  // MIP improving solution
+  readonly mip_solution?: unknown;
+  // MIP interrupt
+  readonly running_time?: number;
+  readonly objective_function_value?: number;
+  readonly num_nodes?: number;
+  readonly primal_bound?: number;
+  readonly dual_bound?: number;
+  readonly mip_gap?: number;
+  // Unknown
+  readonly [name: string]: unknown;
+}
+
+export interface CallbackOutputs {
+  readonly user_interrupt: number;
+}
diff --git a/packages/highs-addon/src/solver.cc b/packages/highs-addon/src/solver.cc
index dbe8c9c..121c17b 100644
--- a/packages/highs-addon/src/solver.cc
+++ b/packages/highs-addon/src/solver.cc
@@ -428,6 +428,49 @@ Napi::Value Solver::GetInfo(const Napi::CallbackInfo& info) {
   return obj;
 }
 
+// Callbacks
+
+void Solver::SetCallback(const Napi::CallbackInfo& info) {
+  // TODO. Need to figure out how best to call JS from worker.
+}
+
+int ToCallbackType(const Napi::Env& env, const Napi::Value& val) {
+  int tp = val.As<Napi::Number>().Int32Value();
+  if (tp < 0 || tp > HighsCallbackType::kNumCallbackType) {
+    ThrowError(env, "Unexpected callback type");
+    return -1;
+  }
+  return tp;
+}
+
+void Solver::StartCallback(const Napi::CallbackInfo& info) {
+  Napi::Env env = info.Env();
+  int length = info.Length();
+  if (length != 1 || !info[0].IsNumber()) {
+    ThrowTypeError(env, "Expected 1 argument [number]");
+    return;
+  }
+  int tp = ToCallbackType(env, info[0]);
+  if (tp < 0) {
+    return;
+  }
+  this->highs_->startCallback(tp);
+}
+
+void Solver::StopCallback(const Napi::CallbackInfo& info) {
+  Napi::Env env = info.Env();
+  int length = info.Length();
+  if (length != 1 || !info[0].IsNumber()) {
+    ThrowTypeError(env, "Expected 1 argument [number]");
+    return;
+  }
+  int tp = ToCallbackType(env, info[0]);
+  if (tp < 0) {
+    return;
+  }
+  this->highs_->stopCallback(tp);
+}
+
 // Solutions
 
 Napi::Value ToFloat64Array(const Napi::Env& env, const std::vector<double>& vec) {
diff --git a/packages/highs-addon/src/solver.h b/packages/highs-addon/src/solver.h
index d0497cd..62c2b59 100644
--- a/packages/highs-addon/src/solver.h
+++ b/packages/highs-addon/src/solver.h
@@ -21,6 +21,10 @@ class Solver : public Napi::ObjectWrap<Solver> {
   void ChangeColsCost(const Napi::CallbackInfo& info);
   void AddRows(const Napi::CallbackInfo& info);
 
+  void SetCallback(const Napi::CallbackInfo& info);
+  void StartCallback(const Napi::CallbackInfo& info);
+  void StopCallback(const Napi::CallbackInfo& info);
+
   void Run(const Napi::CallbackInfo& info);
   Napi::Value GetModelStatus(const Napi::CallbackInfo& info);
   Napi::Value GetInfo(const Napi::CallbackInfo& info);
diff --git a/packages/highs-solver/test/solver.test.ts b/packages/highs-solver/test/solver.test.ts
index 48d9bc4..287d93f 100644
--- a/packages/highs-solver/test/solver.test.ts
+++ b/packages/highs-solver/test/solver.test.ts
@@ -191,4 +191,11 @@ describe('solver', () => {
       });
     }
   });
+
+  describe('handles callbacks', () => {
+    test('simple', async () => {
+      const solver = sut.Solver.create();
+      await solver.setModelFromFile(loader.localUrl('simple.lp'));
+    });
+  });
 });