// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2023 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/graph.h"

#include "absl/container/flat_hash_set.h"
#include "gtest/gtest.h"

namespace ceres::internal {

TEST(Graph, EmptyGraph) {
  Graph<int> graph;
  EXPECT_EQ(graph.vertices().size(), 0);
}

TEST(Graph, AddVertexAndEdge) {
  Graph<int> graph;
  graph.AddVertex(0);
  graph.AddVertex(1);
  graph.AddEdge(0, 1);

  const absl::flat_hash_set<int>& vertices = graph.vertices();
  EXPECT_EQ(vertices.size(), 2);
  EXPECT_EQ(graph.Neighbors(0).size(), 1);
  EXPECT_EQ(graph.Neighbors(1).size(), 1);
}

TEST(Graph, AddVertexIdempotence) {
  Graph<int> graph;
  graph.AddVertex(0);
  graph.AddVertex(1);
  graph.AddEdge(0, 1);

  const absl::flat_hash_set<int>& vertices = graph.vertices();

  EXPECT_EQ(vertices.size(), 2);

  // Try adding the vertex again with a new weight.
  graph.AddVertex(0);
  EXPECT_EQ(vertices.size(), 2);

  // Rest of the graph remains the same.
  EXPECT_EQ(graph.Neighbors(0).size(), 1);
  EXPECT_EQ(graph.Neighbors(1).size(), 1);
}

TEST(Graph, DieOnNonExistentVertex) {
  Graph<int> graph;
  graph.AddVertex(0);
  graph.AddVertex(1);
  graph.AddEdge(0, 1);

  EXPECT_DEATH_IF_SUPPORTED(graph.Neighbors(2), "key not found");
}

TEST(WeightedGraph, EmptyGraph) {
  WeightedGraph<int> graph;
  EXPECT_EQ(graph.vertices().size(), 0);
}

TEST(WeightedGraph, AddVertexAndEdge) {
  WeightedGraph<int> graph;
  graph.AddVertex(0, 1.0);
  graph.AddVertex(1, 2.0);
  graph.AddEdge(0, 1, 0.5);

  const absl::flat_hash_set<int>& vertices = graph.vertices();
  EXPECT_EQ(vertices.size(), 2);
  EXPECT_EQ(graph.VertexWeight(0), 1.0);
  EXPECT_EQ(graph.VertexWeight(1), 2.0);
  EXPECT_EQ(graph.Neighbors(0).size(), 1);
  EXPECT_EQ(graph.Neighbors(1).size(), 1);
  EXPECT_EQ(graph.EdgeWeight(0, 1), 0.5);
  EXPECT_EQ(graph.EdgeWeight(1, 0), 0.5);
}

TEST(WeightedGraph, AddVertexIdempotence) {
  WeightedGraph<int> graph;
  graph.AddVertex(0, 1.0);
  graph.AddVertex(1, 2.0);
  graph.AddEdge(0, 1, 0.5);

  const absl::flat_hash_set<int>& vertices = graph.vertices();

  EXPECT_EQ(vertices.size(), 2);

  // Try adding the vertex again with a new weight.
  graph.AddVertex(0, 3.0);
  EXPECT_EQ(vertices.size(), 2);

  // The vertex weight is reset.
  EXPECT_EQ(graph.VertexWeight(0), 3.0);

  // Rest of the graph remains the same.
  EXPECT_EQ(graph.VertexWeight(1), 2.0);
  EXPECT_EQ(graph.Neighbors(0).size(), 1);
  EXPECT_EQ(graph.Neighbors(1).size(), 1);
  EXPECT_EQ(graph.EdgeWeight(0, 1), 0.5);
  EXPECT_EQ(graph.EdgeWeight(1, 0), 0.5);
}

TEST(WeightedGraph, DieOnNonExistentVertex) {
  WeightedGraph<int> graph;
  graph.AddVertex(0, 1.0);
  graph.AddVertex(1, 2.0);
  graph.AddEdge(0, 1, 0.5);

  EXPECT_DEATH_IF_SUPPORTED(graph.VertexWeight(2), "key not found");
  EXPECT_DEATH_IF_SUPPORTED(graph.Neighbors(2), "key not found");
}

TEST(WeightedGraph, NonExistentEdge) {
  WeightedGraph<int> graph;
  graph.AddVertex(0, 1.0);
  graph.AddVertex(1, 2.0);
  graph.AddEdge(0, 1, 0.5);

  // Default value for non-existent edges is 0.
  EXPECT_EQ(graph.EdgeWeight(2, 3), 0);
}

}  // namespace ceres::internal