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

@@ -1,7 +1,7 @@
 // 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
@@ -15,42 +15,16 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-public class Identifier: CustomStringConvertible, Equatable {
-    var name: String
+open class ProgramExecution: CustomStringConvertible {
+    public var scopes: Scopes = Scopes()
 
-    public init(name: String) {
-        self.name = name
-    }
+    public init() {}
 
-    public var description: String {
-        return "\(name)"
-    }
-
-    public static func ==(lhs: Identifier, rhs: Identifier) -> Bool {
-        return lhs.name == rhs.name
+    open var description: String {
+        return "Runtime:\nScopes: \(scopes)"
     }
 }
 
-public class Variable: Identifier {
-    var constant: Bool
-    var value: ValueType
-
-    public init(name: String, withValue value: ValueType, isConstant constant: Bool) {
-        self.constant = constant
-        self.value = value
-        super.init(name: name)
-    }
-
-    public override var description: String {
-        return "\(super.description) = \(value) \(constant ? "(constant)" : "")"
-    }
-
-    public var value_type: ValueType {
-        get {
-            value
-        }
-    }
-}
 
 public struct Scope: CustomStringConvertible{
     var variables: [Variable] = Array()
@@ -78,6 +52,12 @@ public struct Scope: CustomStringConvertible{
         }
         return .none
     }
+
+    public mutating func declare(variable: Variable) -> Scope {
+        var s = self
+        s.variables.append(variable)
+        return s
+    }
 }
 
 public struct Scopes: CustomStringConvertible {
@@ -108,14 +88,17 @@ public struct Scopes: CustomStringConvertible {
         }
     }
 
+    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
         }
     }
 }
-
-public struct Program {
-    public var parsers: [P4.Parser] = Array()
-    public init() {}
-}

Sources/Common/ProgramTypes.swift

@@ -1,7 +1,7 @@
 // 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
@@ -15,6 +15,44 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+
+public class Identifier: CustomStringConvertible, Equatable {
+    var name: String
+
+    public init(name: String) {
+        self.name = name
+    }
+
+    public var description: String {
+        return "\(name)"
+    }
+
+    public static func ==(lhs: Identifier, rhs: Identifier) -> Bool {
+        return lhs.name == rhs.name
+    }
+}
+
+public class Variable: Identifier {
+    var constant: Bool
+    var value: ValueType
+
+    public init(name: String, withValue value: ValueType, isConstant constant: Bool) {
+        self.constant = constant
+        self.value = value
+        super.init(name: name)
+    }
+
+    public override var description: String {
+        return "\(super.description) = \(value) \(constant ? "(constant)" : "")"
+    }
+
+    public var value_type: ValueType {
+        get {
+            value
+        }
+    }
+}
+
 public enum ValueType: CustomStringConvertible, Equatable {
     case Boolean(Bool)
     case Int(Int)

Sources/Common/Protocols.swift

@@ -0,0 +1,33 @@
+// 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/>.
+
+public protocol EvaluatableExpression {
+    /// Evaluate an expression for a given execution
+    /// - Parameters
+    ///  - execution: The execution context in which to evaluate the expression
+    /// - Returns: The value of expression
+    func evaluate(execution: ProgramExecution) -> ValueType
+}
+
+public protocol EvaluatableParserStatement {
+    /// Evaluate a statement for a given execution
+    /// - Parameters
+    ///  - execution: The execution context in which to evaluate the parser statement
+    /// - Returns: An updated execution after evaluating the parser statement
+    func evaluate(execution: ProgramExecution) -> ProgramExecution
+}
+

Sources/Common/Support.swift

@@ -1,7 +1,7 @@
 // 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

Sources/Lang/Parser.swift

@@ -0,0 +1,133 @@
+// 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/>.
+
+import Common
+
+public struct LocalElements {
+
+}
+
+public struct LocalElement {
+
+}
+
+public struct ParserTransitionStatement {
+  public init() {}
+}
+
+public struct VariableDeclarationStatement {
+  public var variable: Variable
+  public init(withVariable variable: Variable) {
+    self.variable = variable
+  }
+}
+
+public struct ExpressionStatement {
+  public init() {}
+}
+
+public struct ParserState: Equatable, CustomStringConvertible {
+
+  public private(set) var state_name: String
+  public private(set) var local_elements: [EvaluatableParserStatement]
+  public private(set) var statements: [EvaluatableParserStatement]
+  public private(set) var transition: ParserTransitionStatement?
+
+  public var description: String {
+    return "Name: \(state_name)"
+  }
+
+  public static func == (lhs: ParserState, rhs: ParserState) -> Bool {
+    return lhs.state_name == rhs.state_name
+  }
+
+  /// Construct a ParserState
+  public init(
+    name: String, withLocalElements localElements: [EvaluatableParserStatement]?,
+    withStatements statements: [EvaluatableParserStatement]?,
+    withTransition transitionStatement: ParserTransitionStatement
+  ) {
+    state_name = name
+    transition = transitionStatement
+    local_elements = localElements ?? Array()
+    self.statements = statements ?? Array()
+  }
+
+  /// (private) constructor (no transition)
+  ///
+  /// accept and reject are the only final states and they are constructed internally.
+  init(name: String) {
+    state_name = name
+    transition = .none
+    local_elements = Array()
+    statements = Array()
+  }
+}
+
+public struct ParserStates {
+  public var states: [ParserState] = Array()
+}
+
+nonisolated(unsafe) public let accept: ParserState = ParserState(name: "accept")
+nonisolated(unsafe) public let reject: ParserState = ParserState(name: "reject")
+
+public struct Parser {
+  public var states: [ParserState] = Array()
+  public var count: Int {
+    states.count
+  }
+
+  public init() {}
+
+  public func findStartState() -> ParserState? {
+    for state in states {
+      if state.state_name == "start" {
+        return state
+      }
+    }
+    return .none
+  }
+}
+
+public class ParserExecution: ProgramExecution {
+
+    private init(state: ParserState) {
+      self.state = state
+      super.init()
+    }
+
+    public static func create(_ parser: Parser) -> Result<ParserExecution> {
+        guard let start_state = parser.findStartState() else {
+            return Result.Error(Error(withMessage: "Could not find the start state"))
+        }
+        let new = ParserExecution(state: start_state)
+
+        return Result.Ok(new)
+    }
+
+    public var state: ParserState
+
+    public func transition(toNextState state: ParserState) -> ParserExecution {
+        let next = self
+        next.state = state
+        return next
+    }
+
+    public override var description: String {
+        return "Execution: \(super.description)\nCurrent State: \(state)"
+    }
+}

Sources/Lang/Program.swift

@@ -0,0 +1,21 @@
+// 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/>.
+
+public struct Program {
+    public var parsers: [Parser] = Array()
+    public init() {}
+}

Sources/Lang/Types.swift

@@ -1,7 +1,7 @@
 // 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

Sources/Macros/Macros.swift

@@ -1,7 +1,7 @@
 // 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

Sources/P4/Parser.swift

@@ -1,163 +0,0 @@
-// 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/>.
-
-public struct LocalElements {
-
-}
-
-public struct LocalElement {
-
-}
-
-public class ParserExecution: ProgramExecution {
-    public var state: ParserState
-
-    public init(_ state: ParserState) {
-        self.state = state
-    }
-
-    public func transition(toNextState state: ParserState) -> ParserExecution {
-        let next = self
-        next.state = state
-        return next
-    }
-
-    public override var description: String {
-        return "Execution: \(super.description)\nCurrent State: \(state)"
-    }
-}
-
-public protocol Expression {
-    /// Evaluate an expression for a given execution
-    /// - Parameters
-    ///  - execution: The execution context in which to evaluate the expression
-    /// - Returns: The value of expression
-    func evaluate(execution: ParserExecution) -> Value
-}
-
-public protocol ParserStatement {
-    /// Evaluate a statement for a given execution
-    /// - Parameters
-    ///  - execution: The execution context in which to evaluate the parser statement
-    /// - Returns: An updated execution after evaluating the parser statement
-    func evaluate(execution: ParserExecution) -> ParserExecution
-}
-
-public struct ParserTransitionStatement: ParserStatement {
-    public init() {}
-    public func evaluate(execution: ParserExecution) -> ParserExecution {
-        return execution 
-    }
-}
-
-public struct VariableDeclarationStatement: ParserStatement {
-    public var variable: Variable
-    public init(withVariable variable: Variable) {
-        self.variable = variable
-    }
-
-    public func evaluate(execution: ParserExecution) -> ParserExecution {
-        execution.scopes.scopes[0].variables.append(self.variable)
-        return execution
-    }
-}
-
-public struct ExpressionStatement: ParserStatement {
-    public init() {}
-    public func evaluate(execution: ParserExecution) -> ParserExecution {
-        return execution
-    }
-}
-
-public struct ParserState: Equatable, CustomStringConvertible {
-
-    public private(set) var state_name: String
-    public private(set) var local_elements: [ParserStatement]
-    public private(set) var statements: [ParserStatement]
-    public private(set) var transition: ParserTransitionStatement?
-
-    public var description: String {
-        return "Name: \(state_name)"
-    }
-
-    public static func == (lhs: ParserState, rhs: ParserState) -> Bool {
-        return lhs.state_name == rhs.state_name
-    }
-
-    /// Construct a ParserState
-    public init(name: String, withLocalElements localElements: [ParserStatement]?, withStatements statements: [ParserStatement]?, withTransition transitionStatement: ParserTransitionStatement) {
-        state_name = name
-        transition = transitionStatement
-        local_elements = localElements ?? Array()
-        self.statements = statements ?? Array()
-    }
-
-    func evaluate(execution: ParserExecution) -> ParserExecution {
-        var currentExecution = execution
-
-        // First, evaluate the local elements.
-        for local_element in local_elements {
-            currentExecution = local_element.evaluate(execution: currentExecution)
-        }
-
-        // Then, evaluate the statements.
-        for statement in statements {
-            currentExecution = statement.evaluate(execution: currentExecution)
-        }
-
-        return if let transition = transition {
-            currentExecution.transition(toNextState: accept)
-        } else {
-            currentExecution.transition(toNextState: reject)
-        }
-    }
-
-    /// (private) constructor (no transition)
-    /// 
-    /// accept and reject are the only final states and they are constructed internally.
-    init(name: String) {
-        state_name = name
-        transition = .none
-        local_elements = Array()
-        statements = Array()
-    }
-}
-
-public struct ParserStates {
-    public var states: [ParserState] = Array()
-}
-
-nonisolated(unsafe) public let accept: ParserState = ParserState(name: "accept")
-nonisolated(unsafe) public let reject: ParserState = ParserState(name: "reject")
-
-public struct Parser {
-    public var states: [ParserState] = Array()
-    public var count: Int {
-        states.count
-    }
-
-    public init() {}
-
-    public func findStartState() -> Optional<ParserState> {
-        for state in states {
-            if state.state_name == "start" {
-                return state
-            }
-        }
-        return .none
-    }
-}

Sources/P4/Runtime.swift

@@ -1,56 +0,0 @@
-// 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/>.
-
-public class ProgramExecution: CustomStringConvertible {
-    public var scopes: Scopes = Scopes()
-
-    public init() {}
-
-    public var description: String {
-        return "Runtime:\nScopes: \(scopes)"
-    }
-}
-
-//public struct ParserRuntime: ProgramRuntime {
-public class ParserRuntime: CustomStringConvertible {
-    var execution: ParserExecution
-
-    init(execution: ParserExecution) {
-        self.execution = execution
-    }
-
-    public static func create(program: P4.Parser) -> Result<ParserRuntime> {
-        // First, find the start state.
-        guard let start_state = program.findStartState() else {
-            return Result.Error(Error(withMessage: "Could not find the start state"))
-        }
-        return Result.Ok(P4.ParserRuntime(execution: P4.ParserExecution(start_state)))
-    }
-
-    public func run(input: P4.Packet) -> Result<ParserExecution> {
-        execution.scopes.enter()
-        while execution.state != P4.accept && execution.state != P4.reject {
-            execution = execution.state.evaluate(execution: execution)
-        }
-        return .Ok(execution)
-    }
-
-    public var description: String {
-        //return "\(super.description)\nState: \(execution?.description ?? "N/A")\nError: \(error?.description ?? "None")"
-        return "Runtime:\nExecution: \(execution)"
-    }
-}

Sources/Parser/Parser.swift

@@ -1,7 +1,7 @@
 // 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
@@ -15,46 +15,48 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-import P4
+import Common
+import Lang
+import Runtime
 import SwiftTreeSitter
-import TreeSitterP4
 import TreeSitterExtensions
+import TreeSitterP4
 
 let p4lang = Language(tree_sitter_p4())
 
 public protocol ParseableValueType {
-  static func Parse(type: String, withValue value: String) -> Result<P4.ValueType>
+  static func Parse(type: String, withValue value: String) -> Result<ValueType>
 }
 
 // This seems unnecessary because all the value types are in a single enum?
-extension P4.ValueType: ParseableValueType {
-  public static func Parse(type: String, withValue value: String) -> Result<P4.ValueType> {
+extension ValueType: ParseableValueType {
+  public static func Parse(type: String, withValue value: String) -> Result<ValueType> {
     if type == "bool" {
       // Default
       if value == "" {
-        return .Ok(P4.ValueType.Boolean(false))
+        return .Ok(ValueType.Boolean(false))
       }
 
       if value == "true" {
-        return .Ok(P4.ValueType.Boolean(true))
+        return .Ok(ValueType.Boolean(true))
       } else if value == "false" {
-        return .Ok(P4.ValueType.Boolean(false))
+        return .Ok(ValueType.Boolean(false))
       }
       return .Error(Error(withMessage: "Cannot convert \(value) into boolean value"))
 
     } else if type == "string" {
-      return .Ok(P4.ValueType.String(value))
+      return .Ok(ValueType.String(value))
 
     } else if type == "int" {
       // Default
       if value == "" {
-        return .Ok(P4.ValueType.Int(0))
+        return .Ok(ValueType.Int(0))
       }
 
       guard let parsed_value = Swift.Int(value) else {
         return .Error(Error(withMessage: "Cannot convert \(value) into integer value"))
       }
-      return .Ok(P4.ValueType.Int(parsed_value))
+      return .Ok(ValueType.Int(parsed_value))
     }
 
     return .Error(Error(withMessage: "Invalid type"))
@@ -62,11 +64,13 @@ extension P4.ValueType: ParseableValueType {
 }
 
 public protocol ParseableParserStatement {
-  static func Parse(node: Node, inTree tree: MutableTree) -> Result<P4.ParserStatement?>
+  static func Parse(node: Node, inTree tree: MutableTree) -> Result<EvaluatableParserStatement?>
 }
 
-extension P4.ExpressionStatement: ParseableParserStatement {
-  public static func Parse(node: Node, inTree tree: MutableTree) -> Result<P4.ParserStatement?> {
+extension ExpressionStatement: ParseableParserStatement {
+  public static func Parse(
+    node: Node, inTree tree: MutableTree
+  ) -> Result<EvaluatableParserStatement?> {
     guard
       let parser_state_query = try? SwiftTreeSitter.Query(
         language: p4lang,
@@ -82,16 +86,16 @@ extension P4.ExpressionStatement: ParseableParserStatement {
     let expression_capture = query_result.captures(named: "expression")
     if !expression_capture.isEmpty {
       // TODO: Actually create an ExpressionStatement
-      return Result.Ok(P4.ExpressionStatement())
+      return Result.Ok(ExpressionStatement())
     }
-
     return Result.Ok(.none)
-
   }
 }
 
-extension P4.VariableDeclarationStatement: ParseableParserStatement {
-  public static func Parse(node: Node, inTree tree: MutableTree) -> Result<P4.ParserStatement?> {
+extension VariableDeclarationStatement: ParseableParserStatement {
+  public static func Parse(
+    node: Node, inTree tree: MutableTree
+  ) -> Result<EvaluatableParserStatement?> {
     guard
       let parser_state_query = try? SwiftTreeSitter.Query(
         language: p4lang,
@@ -125,10 +129,10 @@ extension P4.VariableDeclarationStatement: ParseableParserStatement {
         ""
       }
 
-    return switch P4.ValueType.Parse(type: type_name, withValue: value) {
+    return switch ValueType.Parse(type: type_name, withValue: value) {
     case Result.Ok(let value_type):
       Result.Ok(
-        P4.VariableDeclarationStatement(
+        VariableDeclarationStatement(
           withVariable: Variable(name: variable_name, withValue: value_type, isConstant: false)))
     case Result.Error(let e):
       Result.Error(e)
@@ -139,9 +143,10 @@ extension P4.VariableDeclarationStatement: ParseableParserStatement {
 public struct Parser {
 
   public struct P4Parser {
+
     static func LocalElements(
       node: Node, inTree tree: MutableTree
-    ) -> Result<[P4.ParserStatement]> {
+    ) -> Result<[EvaluatableParserStatement]> {
 
       guard
         let parser_le_statement_query = try? SwiftTreeSitter.Query(
@@ -154,15 +159,15 @@ public struct Parser {
       }
 
       let localElementsParsers: [ParseableParserStatement.Type] = [
-        P4.VariableDeclarationStatement.self
+        VariableDeclarationStatement.self
       ]
 
-      var localElements: [P4.ParserStatement] = Array()
+      var localElements: [EvaluatableParserStatement] = Array()
 
       let qr = parser_le_statement_query.execute(node: node, in: tree)
       for raw_le_statement in qr {
         let raw_le_statement_capture = raw_le_statement.captures(named: "parser-local-element")
-        var parsed_le_statement: P4.ParserStatement? = .none
+        var parsed_le_statement: EvaluatableParserStatement? = .none
 
         for le_parser in localElementsParsers {
           if case Result.Ok(.some(let parsed)) = le_parser.Parse(
@@ -187,7 +192,7 @@ public struct Parser {
 
     static func Statements(
       node: Node, inTree tree: MutableTree
-    ) -> Result<[P4.ParserStatement]> {
+    ) -> Result<[EvaluatableParserStatement]> {
 
       guard
         let parser_statement_query = try? SwiftTreeSitter.Query(
@@ -200,16 +205,16 @@ public struct Parser {
       }
 
       let statementParsers: [ParseableParserStatement.Type] = [
-        P4.ExpressionStatement.self, P4.VariableDeclarationStatement.self,
+        ExpressionStatement.self, VariableDeclarationStatement.self,
       ]
 
-      var statements: [P4.ParserStatement] = Array()
+      var statements: [EvaluatableParserStatement] = Array()
 
       let qr = parser_statement_query.execute(node: node, in: tree)
       for raw_statement in qr {
         let raw_statement_capture = raw_statement.captures(named: "parser-statement")
 
-        var parsed_statement: P4.ParserStatement? = .none
+        var parsed_statement: EvaluatableParserStatement? = .none
 
         // Iterate through statement parsers and give each one a chance.
         for parser in statementParsers {
@@ -234,12 +239,11 @@ public struct Parser {
 
     static func TransitionStatement(
       node: Node, inTree tree: MutableTree
-    ) -> P4.ParserTransitionStatement?
-    {
-      return P4.ParserTransitionStatement()
+    ) -> ParserTransitionStatement? {
+      return ParserTransitionStatement()
     }
 
-    static func State(node: Node, inTree tree: MutableTree) -> Result<P4.ParserState> {
+    static func State(node: Node, inTree tree: MutableTree) -> Result<ParserState> {
       guard
         let parser_state_query = try? SwiftTreeSitter.Query(
           language: p4lang,
@@ -273,10 +277,10 @@ public struct Parser {
         if !state_le_capture.isEmpty {
           LocalElements(node: state_le_capture[0].node, inTree: tree)
         } else {
-          Result.Ok([P4.ParserStatement]())
+          Result.Ok([EvaluatableParserStatement]())
         }
 
-      guard case Result<[P4.ParserStatement]>.Ok(let parsed_les) = maybe_parsed_les else {
+      guard case Result<[EvaluatableParserStatement]>.Ok(let parsed_les) = maybe_parsed_les else {
         return Result.Error(maybe_parsed_les.error()!)
       }
 
@@ -284,22 +288,24 @@ public struct Parser {
         if !statements_capture.isEmpty {
           Statements(node: statements_capture[0].node, inTree: tree)
         } else {
-          Result.Ok([P4.ParserStatement]())
+          Result.Ok([EvaluatableParserStatement]())
         }
-      guard case Result<[P4.ParserStatement]>.Ok(let parsed_statements) = maybe_parsed_statements
+      guard
+        case Result<[EvaluatableParserStatement]>.Ok(let parsed_statements) =
+          maybe_parsed_statements
       else {
         return Result.Error(maybe_parsed_statements.error()!)
       }
 
       // TODO: Validate that there is only one!
       return Result.Ok(
-        P4.ParserState(
+        ParserState(
           name: parsed_state_name, withLocalElements: parsed_les,
           withStatements: parsed_statements,
           withTransition: transition_statement))
     }
   }
-  static func Parser(node: Node, inTree tree: MutableTree) -> Result<P4.Parser> {
+  static func Parser(node: Node, inTree tree: MutableTree) -> Result<Lang.Parser> {
     guard
       let parser_state_query = try? SwiftTreeSitter.Query(
         language: p4lang,
@@ -311,7 +317,7 @@ public struct Parser {
         Error(withMessage: "Could not compile the parser state tree sitter query"))
     }
 
-    var parser = P4.Parser()
+    var parser = Lang.Parser()
 
     // Build a state from each one listed.
     for parser_states in parser_state_query.execute(node: node, in: tree) {
@@ -323,7 +329,7 @@ public struct Parser {
     return Result.Ok(parser)
   }
 
-  public static func Program(_ source: String) -> Result<P4.Program> {
+  public static func Program(_ source: String) -> Result<Program> {
     let p = SwiftTreeSitter.Parser.init()
 
     do {
@@ -350,7 +356,7 @@ public struct Parser {
         Error(withMessage: "Could not compile the parser declaration tree sitter query"))
     }
 
-    var program: P4.Program = P4.Program()
+    var program = Lang.Program()
 
     let parser_qc = parser_declaration_query.execute(in: tree)
 

Sources/Runtime/Parser.swift

@@ -0,0 +1,50 @@
+// 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/>.
+
+import Common
+import Lang
+
+
+
+extension ParserTransitionStatement: EvaluatableParserTransitionStatement {
+  // TODO: Currently transitions to accept.
+  func transition(execution: ProgramExecution) -> (ParserState, ProgramExecution) {
+    return (accept, execution)
+  }
+}
+
+extension ParserState: EvaluatableParserState {
+  public func evaluate(execution: ProgramExecution) -> (ParserState, ProgramExecution) {
+    var currentExecution = execution
+
+    // First, evaluate the local elements.
+    for local_element in local_elements {
+      currentExecution = local_element.evaluate(execution: currentExecution)
+    }
+
+    // Then, evaluate the statements.
+    for statement in statements {
+      currentExecution = statement.evaluate(execution: currentExecution)
+    }
+
+    return if let transition = transition {
+      transition.transition(execution: currentExecution)
+    } else {
+      (reject, currentExecution)
+    }
+  }
+}

Sources/Runtime/Program.swift

@@ -0,0 +1,33 @@
+// 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/>.
+
+import Lang
+import Common
+
+extension VariableDeclarationStatement: EvaluatableParserStatement {
+  public func evaluate(execution: ProgramExecution) -> ProgramExecution {
+    let new_scopes = execution.scopes.declare(variable: self.variable)
+    execution.scopes = new_scopes
+    return execution
+  }
+}
+
+extension ExpressionStatement: EvaluatableParserStatement {
+  public func evaluate(execution: ProgramExecution) -> ProgramExecution {
+    return execution
+  }
+}

Sources/Runtime/Protocols.swift

@@ -0,0 +1,31 @@
+// 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/>.
+
+import Common
+import Lang
+
+protocol EvaluatableParserState {
+  func evaluate(execution: ProgramExecution) -> (ParserState, ProgramExecution)
+}
+
+protocol EvaluatableParserTransitionStatement {
+  func transition(execution: ProgramExecution) -> (ParserState, ProgramExecution)
+}
+
+public protocol Execution {
+    func execute() -> (ParserState, ProgramExecution)
+}

Sources/Runtime/Runtime.swift

@@ -0,0 +1,58 @@
+// 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/>.
+
+import Common
+import Lang
+
+public class ParserRuntime: CustomStringConvertible {
+  var execution: ParserExecution
+
+  init(execution: ParserExecution) {
+    self.execution = execution
+  }
+
+  public static func create(program: Lang.Parser) -> Result<ParserRuntime> {
+    switch ParserExecution.create(program) {
+    case .Ok(let execution): return .Ok(Runtime.ParserRuntime(execution: execution))
+    case .Error(let error): return .Error(error)
+
+    }
+  }
+
+  public func run(input: Packet) -> Result<(ParserState, ProgramExecution)> {
+    execution.scopes.enter()
+    return .Ok(execution.execute())
+  }
+
+  public var description: String {
+    //return "\(super.description)\nState: \(execution?.description ?? "N/A")\nError: \(error?.description ?? "None")"
+    return "Runtime:\nExecution: \(execution)"
+  }
+}
+
+extension ParserExecution: Execution {
+  public func execute() -> (ParserState, ProgramExecution) {
+    var execution = self as ProgramExecution
+    var state = self.state
+
+    // Evaluate until the state is either accept or reject.
+    while state != accept && state != reject {
+      (state, execution) = self.state.evaluate(execution: execution)
+    }
+    return (state, execution)
+  }
+}

Sources/TreeSitterExtensions/Extensions.swift

@@ -1,7 +1,7 @@
 // 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