basic package graph implemented

Sources/apk/Graph/ApkPackageGraph.swift

@@ -0,0 +1,64 @@
+/*
+ * darwin-apk © 2024 Gay Pizza Specifications
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+class ApkPackageGraph {
+  let pkgIndex: ApkIndex
+
+  private var _nodes = [ApkPackageGraphNode]()
+
+  var nodes: [ApkPackageGraphNode] { self._nodes }
+  var shallowIsolates: [ApkPackageGraphNode] { self._nodes.filter(\.parents.isEmpty) }
+  var deepIsolates: [ApkPackageGraphNode] { self._nodes.filter(\.children.isEmpty) }
+
+  init(index: ApkIndex) {
+    self.pkgIndex = index
+  }
+
+  func buildGraphNode() {
+    var provides = [String: Int]()
+
+    for (idx, package) in self.pkgIndex.packages.enumerated() {
+      provides[package.name] = idx
+      for provision in package.provides {
+        provides[provision.name] = idx
+      }
+    }
+
+    for package in pkgIndex.packages {
+      self._nodes.append(.init(
+        package: package,
+        children: package.dependencies.compactMap { dependency in
+          guard let id = provides[dependency.requirement.name] else {
+            return nil
+          }
+          return .init(self, id: id, constraint: .dep(version: dependency.requirement.versionSpec))
+        } + package.provides.compactMap { provision in
+          guard let id = provides[provision.name] else {
+            return nil
+          }
+          return .init(self, id: id, constraint: .provision)
+        } + package.installIf.compactMap { installIf in
+          guard let id = provides[installIf.requirement.name] else {
+            return nil
+          }
+          return .init(self, id: id, constraint: .installIf(version: installIf.requirement.versionSpec ))
+        }
+      ))
+    }
+
+    var reverseDependencies = [ApkIndexRequirementRef: [ApkIndexRequirementRef]]()
+    for (index, node) in self._nodes.enumerated() {
+      for child in node.children {
+        reverseDependencies[child, default: []].append(
+          .init(self, id: index, constraint: child.constraint)
+        )
+      }
+    }
+
+    for (ref, parents) in reverseDependencies {
+      self._nodes[ref.packageID].parents = parents
+    }
+  }
+}