Refactor

Refactor into four major components:

1. Common: Things shared among all other components.
2. Lang: P4-language-related components.
3. Runtime: Components required to run a P4 program.
4. Parser: Components for parsing a P4 program from source.

Other components:

1. Macros
2. Tests
3. TreeSitterExtensions: Extra tree sitter functionality

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/Common/Execution.swift

@@ -0,0 +1,104 @@
+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+//
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+open class ProgramExecution: CustomStringConvertible {
+    public var scopes: Scopes = Scopes()
+
+    public init() {}
+
+    open var description: String {
+        return "Runtime:\nScopes: \(scopes)"
+    }
+}
+
+
+public struct Scope: CustomStringConvertible{
+    var variables: [Variable] = Array()
+    public init() {}
+
+    public var description: String {
+        var result = String()
+        for v in variables {
+            result += "\(v)\n"
+        }
+        return result
+    }
+
+    public var count: Int {
+        get {
+            variables.count
+        }
+    }
+
+    public func lookup(identifier: Identifier) -> Variable? {
+        for v in variables {
+            if v == identifier {
+                return v
+            }
+        }
+        return .none
+    }
+
+    public mutating func declare(variable: Variable) -> Scope {
+        var s = self
+        s.variables.append(variable)
+        return s
+    }
+}
+
+public struct Scopes: CustomStringConvertible {
+    var scopes: [Scope] = Array()
+
+    public init() {}
+
+    public mutating func enter() {
+        scopes.append(Scope())
+    }
+
+    public mutating func exit() {
+        let _ = scopes.popLast()
+    }
+
+    public var description: String {
+        var result = String()
+        for s in scopes {
+            result += "Scope:\n\(s)\n"
+        }
+
+        return result
+    }
+
+    public var current: Scope? {
+        get {
+            scopes.last
+        }
+    }
+
+    public func declare(variable: Variable) -> Scopes {
+        var s = self
+        if var scope = s.scopes.popLast() {
+            s.scopes.append(scope.declare(variable: variable))
+        }
+        return s
+    }
+
+    public var count: Int {
+        get {
+            scopes.count
+        }
+    }
+}