// 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 SwiftTreeSitter
import TreeSitterExtensions
import TreeSitterP4

extension CST.Declaration: Parsable {
  public typealias C = CST.Categories.Declaration
  public static func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Categories.Declaration> {

    // Be kind to our user -- if we are at a declaration node, dive into it!
    let declaration_node =
      if node.nodeType == "declaration" {
        node.child(at: 0)!
      } else {
        node
      }

    let declaration_compilers: [String: any Parsable<CST.Categories.Declaration>.Type] = [
      "function_declaration": CST.FunctionDeclaration.self,
      "control_declaration": CST.Control.self,
      //"type_declaration": AST.P4Struct.self,
      "parserDeclaration": CST.Parser.self,
      /// ASSUME: Type declarations are struct declarations.
      "extern_declaration": CST.ExternDeclaration.self,
    ]

    guard let declaration_compiler = declaration_compilers[declaration_node.nodeType!] else {
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Could not find parser for declaration \(declaration_node.nodeType!)"))
    }

    return declaration_compiler.Parse(node: declaration_node, withContext: context).map {
      result in
      .Ok(result)
    }
  }
}

@deriveParsableStatement
extension CST.Declaration: ParsableStatement {}

extension CST.FunctionDeclaration: Parsable {
  public typealias C = CST.Categories.Declaration
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Common.Result<CST.Categories.Declaration> {
    let function_declaration_node = node
    #RequireNodeType<Node, CST.Categories.Declaration>(
      node: function_declaration_node, type: "function_declaration",
      nice_type_name: "Function Declaration")

    var walker = Walker(node: function_declaration_node)
    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: function_declaration_node.toSourceLocation(),
          withError: "Missing function declaration component")))

    let maybe_function_type = CST.Types.ParseType(type: current_node!, withContext: context)
    guard case .Ok(let function_type) = maybe_function_type else {
      return .Error(maybe_function_type.error()!)
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: function_declaration_node.toSourceLocation(),
          withError: "Missing function declaration component")))

    let maybe_function_name = CST.Identifier.ParseExpression(
      node: current_node!, withContext: context)
    guard case .Ok(let function_name) = maybe_function_name else {
      return .Error(maybe_function_name.error()!)
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: function_declaration_node.toSourceLocation(),
          withError: "Missing function declaration component")))

    let maybe_function_parameters = CST.ParameterList.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let function_parameters) = maybe_function_parameters
    else {
      return .Error(maybe_function_parameters.error()!)
    }

    var function_body: CST.BlockStatement? = .none

    walker.next()
    if let body = walker.getNext() {
      let maybe_function_body = CST.BlockStatement.Parse(node: body, withContext: context)

      guard case .Ok(let parsed_function_body) = maybe_function_body else {
        return .Error(maybe_function_body.error()!)
      }
      function_body = parsed_function_body
    } else {

      // If we are in an extern context, no body is okay!

      if !context.extern_context {
        return Result.Error(
          ErrorWithLocation(
            sourceLocation: function_declaration_node.toSourceLocation(),
            withError: "Missing function declaration component"))
      }
    }

    let function_declaration = CST.FunctionDeclaration(
      named: function_name as! CST.Identifier, ofType: function_type,
      withParameters: function_parameters,
      withBody: function_body)

    // Do not use the updated context returned by parsing the body
    // and do not use the function_scope, either.
    // And, do not update the context if we are compiling in an
    // extern context -- the wrapping extern declaration will take care of that.
    return .Ok(
      function_declaration,
    )
  }
}

extension CST.StructDeclaration: Parsable {
  public typealias C = CST.StructDeclaration
  static public func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<CST.StructDeclaration> {
    let struct_declaration_node = node.child(at: 0)!
    var walker = Walker(node: struct_declaration_node)
    var currentNode: Node? = .none

    #RequireNodeType<Node, Result<CST.StructDeclaration>>(
      node: struct_declaration_node, type: "struct_declaration",
      nice_type_name: "struct declaration")

    // Skip the keyword struct
    walker.next()
    #MustOr(
      result: currentNode, thing: walker.getNext(),
      or: Result<CST.StructDeclaration>.Error(
        ErrorWithLocation(
          sourceLocation: struct_declaration_node.toSourceLocation(),
          withError: "Missing function declaration component")))

    // The name of the struct type.
    let maybe_struct_identifier = CST.Identifier.ParseExpression(
      node: currentNode!, withContext: context)
    guard case Result.Ok(let struct_identifier) = maybe_struct_identifier else {
      return Result.Error(maybe_struct_identifier.error()!)
    }
    walker.next()

    // Skip the '{'
    walker.next()
    #MustOr(
      result: currentNode, thing: walker.getNext(),
      or: Result<CST.StructDeclaration>.Error(
        ErrorWithLocation(
          sourceLocation: struct_declaration_node.toSourceLocation(),
          withError: "Missing function declaration component")))

    // If there are no fields, it will be a "}"
    if currentNode!.nodeType == "}" {
      let struc = CST.StructDeclaration(struct_identifier as! CST.Identifier, [])
      return Result.Ok(struc)
    }

    var parse_errs: (any Errorable)? = .none
    var parsed_fields: [CST.VariableDeclarationStatement] = Array()

    if currentNode!.nodeType == "struct_declaration_fields" {
      currentNode!.enumerateNamedChildren { declaration_field in
        switch CST.VariableDeclarationStatement.Parse(
          node: declaration_field, withContext: context)
        {
        case .Ok(let variable_declaration):
          parsed_fields.append(variable_declaration)
        case .Error(let e):
          parse_errs =
            if let e = parse_errs {
              parse_errs?.append(error: e)
            } else {
              e
            }
        }
      }
    }

    if let parse_errs = parse_errs {
      return .Error(ErrorWithLabel("Error(s) parsing select cases", parse_errs))
    }

    let declared_struct = CST.StructDeclaration(struct_identifier as! CST.Identifier, parsed_fields)
    return .Ok(declared_struct)
  }
}

extension CST.Parser: Parsable {
  public typealias C = CST.Categories.Declaration
  public static func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Categories.Declaration> {
    let parser_node = node
    #RequireNodeType<Node, Result<CST.Categories.Declaration>>(
      node: parser_node, type: "parserDeclaration", nice_type_name: "parser declaration")
    var walker = Walker(node: parser_node)
    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: parser_node.toSourceLocation(),
          withError: "Missing elements of parser declaration")))

    if current_node!.nodeType != "parserType" {
      return .Error(
        ErrorWithLocation(
          sourceLocation: current_node!.toSourceLocation(),
          withError: "Missing type for parser declaration"))
    }

    let type_node = current_node
    var parser_name: CST.Identifier? = .none

    /// TODO: Handle parser parameter lists.
    var parameter_list = CST.ParameterList()

    do {
      var type_node_walker = Walker(node: type_node!)
      var type_node_child: Node? = .none

      #MustOr(
        result: type_node_child, thing: type_node_walker.getNext(),
        or: Result<CST.Categories.Declaration>.Error(
          ErrorWithLocation(
            sourceLocation: parser_node.toSourceLocation(),
            withError: "Missing elements of parser type in parser declaration")))

      if type_node_child!.nodeType == "annotations" {
        return .Error(
          ErrorWithLocation(
            sourceLocation: type_node_child!.toSourceLocation(),
            withError: "Annotations in parser type are not yet handled."))
        // Will increment indexes here.
      }

      type_node_walker.next()
      #MustOr(
        result: type_node_child, thing: type_node_walker.getNext(),
        or: Result<CST.Categories.Declaration>.Error(
          ErrorWithLocation(
            sourceLocation: type_node_child!.toSourceLocation(),
            withError: "Missing name in parser type declaration")))

      switch CST.Identifier.ParseExpression(node: type_node_child!, withContext: context) {
      case .Ok(let id): parser_name = (id as! CST.Identifier)
      case .Error(let e):
        return .Error(e)
      }

      type_node_walker.next()
      #MustOr(
        result: type_node_child, thing: type_node_walker.getNext(),
        or: Result<CST.Categories.Declaration>.Error(
          ErrorWithLocation(
            sourceLocation: type_node_child!.toSourceLocation(),
            withError: "Missing parser parameters")))

      switch CST.ParameterList.Parse(node: type_node_child!, withContext: context) {
      case .Ok(let parsed_parameter_list):
        parameter_list = parsed_parameter_list
      case .Error(let e):
        return .Error(e)
      }
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: parser_node.toSourceLocation(),
          withError: "Missing parser declaration component")))

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: parser_node.toSourceLocation(),
          withError: "Missing elements of parser declaration")))

    if current_node!.nodeType == "parserLocalElements" {
      return .Error(
        ErrorWithLocation(
          sourceLocation: current_node!.toSourceLocation(),
          withError: "Parser Local Elements are not yet handled."))
      // Will increment indexes here.
    }

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: parser_node.toSourceLocation(),
          withError: "Missing body of parser declaration")))

    if current_node!.nodeType != "parserStates" {
      return .Error(Error(withMessage: "Missing parser states in parser declaration"))
    }

    var parser = CST.Parser(withName: parser_name!, withParameters: parameter_list)

    // Build a state from each one listed.
    var errors: (any Errorable)? = .none

    /// TODO: Assert that there is only one.
    current_node!.enumerateNamedChildren { parser_state in
      if parser_state.nodeType != "parserState" {
        return
      }

      // Parse a state in a nested scope.
      switch CST.ParserState.Parse(
        node: parser_state,
        withContext: context)
      {
      case Result.Ok(let state):
        // All states are instances inside the parser.
        parser.states = parser.states.append(state: state)
      case Result.Error(let e):
        errors =
          if let errors = errors {
            errors.append(error: e)
          } else {
            e
          }
      }
    }

    if let errors = errors {
      return .Error(errors)
    }

    return .Ok(parser)
  }
}

extension CST.Control: Parsable {
  public typealias C = CST.Categories.Declaration
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Common.Result<CST.Categories.Declaration> {

    #RequireNodeType<Node, Result<CST.Categories.Declaration>>(
      node: node, type: "control_declaration", nice_type_name: "control declaration")

    var walker = Walker(node: node)
    var current_node: Node? = .none

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing control declaration component")))

    guard
      case .Ok(let control_name) = CST.Identifier.ParseExpression(
        node: current_node!, withContext: context)
    else {
      return Result.Error(
        Error(withMessage: "Could not parse a parameter name from \(current_node!.text!)"))
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing control declaration component")))

    let maybe_control_parameters = CST.ParameterList.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let control_parameters) = maybe_control_parameters
    else {
      return .Error(maybe_control_parameters.error()!)
    }

    walker.next()
    // Skip the '{'
    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Categories.Declaration>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing control declaration component")))

    var actions: [CST.Action] = Array()
    var tables: [CST.Table] = Array()
    var apply: CST.ApplyStatement? = .none

    //                                                         Because the final child
    //                                                         is the '}'.
    //                                                          \/\/
    let body_parse_results = walker.overUntil(n: node.childCount - 1) { current_node in
      if current_node.nodeType == "action_declaration" {
        let maybe_action_declaration = CST.Action.Parse(
          node: current_node, withContext: context)
        guard
          case .Ok(let action_declaration) = maybe_action_declaration
        else {
          return .Error(maybe_action_declaration.error()!)
        }
        actions.append(action_declaration)
      } else if current_node.nodeType == "table_declaration" {
        let maybe_table_declaration = CST.Table.Parse(
          node: current_node, withContext: context)
        guard
          case .Ok(let table_declaration) = maybe_table_declaration
        else {
          return .Error(maybe_table_declaration.error()!)
        }
        tables.append(table_declaration)
      } else if current_node.nodeType == "apply_statement" {
        // When we see an apply, that is it for the actions and the tables.
        let maybe_apply_statement = CST.ApplyStatement.Parse(
          node: current_node, withContext: context)
        guard
          case .Ok(let apply_statement) = maybe_apply_statement
        else {
          return .Error(maybe_apply_statement.error()!)
        }
        apply = apply_statement

        // The apply is the last thing in a control declaration.
        // But, that is handled by the compiler.
      } else {
        return .Error(
          ErrorWithLocation(
            sourceLocation: current_node.toSourceLocation(),
            withError: "Uknown node type in control declaration"))
      }
      return .Ok(())
    }

    if case .Error(let e) = body_parse_results {
      return .Error(e)
    }

    // There should only be a single table!
    /// TODO: Check the semantics here.
    if tables.count > 1 {
      /// TODO: Make this error message better.
      /// IDEA: Add a "compilation context" for the error message into the `CompilationContext`
      // that can be retrieved to make the error messages nicer.
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "More than one table in control declaration"))
    }

    // Check to make sure that there is an apply.
    guard let apply = apply else {
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing apply in control declaration"
        ))
    }

    return .Ok(
      CST.Control(
        named: control_name as! CST.Identifier, withParameters: control_parameters,
        withTable: tables[0],
        withActions: CST.Actions(withActions: actions), withApply: apply))
  }
}

extension CST.Action: Parsable {
  public typealias C = CST.Action
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Action> {
    #RequireNodeType<Node, P4Type>(
      node: node, type: "action_declaration", nice_type_name: "Action Declaration")

    var walker = Walker(node: node)
    var current_node: Node? = .none

    // Skip action keyword
    walker.next()

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Action>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing action declaration component"
        ))
    )

    guard
      case .Ok(let action_name) = CST.Identifier.ParseExpression(
        node: current_node!, withContext: context)
    else {
      return Result.Error(
        Error(withMessage: "Could not parse an action name from \(current_node!.text!)"))
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Action>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing action declaration component"
        ))
    )

    let maybe_action_parameters = CST.ParameterList.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let action_parameters) = maybe_action_parameters
    else {
      return .Error(maybe_action_parameters.error()!)
    }

    // Check whether the parameters are in the proper order.
    let remaining_parameters = action_parameters.parameters.drop(while: {
      $0.type.tipe.direction() != .none
    })
    if remaining_parameters.contains(where: { $0.type.tipe.direction() != .none }) {
      return .Error(
        ErrorWithLocation(
          sourceLocation: current_node!.toSourceLocation(),
          withError: "All parameters with direction must precede directionless parameters"))
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Action>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing action declaration component"
        ))
    )

    let maybe_action_body = CST.BlockStatement.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let action_body) = maybe_action_body else {
      return .Error(maybe_action_body.error()!)
    }

    /// TODO: Actions cannot contain switches!

    return .Ok(
      CST.Action(
        named: action_name as! CST.Identifier, withParameters: action_parameters,
        withBody: action_body))
  }
}

extension CST.TableKeyEntry: Parsable {
  public typealias C = CST.TableKeyEntry
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.TableKeyEntry> {

    #RequireNodeType<Node, CST.TableKeyEntry>(
      node: node, type: "table_key_entry", nice_type_name: "Table Key Entry")

    var walker = Walker(node: node)

    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.TableKeyEntry>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing table key entry declaration component")))

    let maybe_keyset_expression = CST.KeysetExpression.ParseExpression(
      node: current_node!, withContext: context)
    guard case .Ok(let keyset_expression) = maybe_keyset_expression else {
      return Result.Error(maybe_keyset_expression.error()!)
    }

    walker.next()
    // Skip the ':'
    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.TableKeyEntry>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing table key entry declaration component")))

    let maybe_match_type = CST.TableKeyMatchType.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let match_type) = maybe_match_type else {
      return .Error(maybe_match_type.error()!)
    }

    return .Ok(CST.TableKeyEntry(keyset_expression as! CST.KeysetExpression, match_type))
  }
}

extension CST.TableKeyMatchType: Parsable {
  public typealias C = CST.TableKeyMatchType
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.TableKeyMatchType> {
    #RequireNodeType<Node, CST.TableKeyMatchType>(
      node: node, type: "table_key_match_type", nice_type_name: "Table Key Match Type")

    if node.text! == "exact" {
      return .Ok(CST.TableKeyMatchType.Exact)
    }
    return .Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(),
        withError: "\(node.text!) is not a valid match type)"))
  }
}

extension CST.TableKeys: Parsable {
  public typealias C = CST.TableKeys
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.TableKeys> {
    #RequireNodeType<Node, CST.TableKeyMatchType>(
      node: node, type: "table_keys", nice_type_name: "Table Keys")

    var walker = Walker(node: node)
    // Skip the
    // keys = {
    // 1    2 3
    walker.next()  // 1
    walker.next()  // 2
    walker.next()  // 3

    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.TableKeys>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing table keys declaration component in control declaration"))
    )

    let (keys, errors) = walker.try_map(n: node.childCount - 1, onlyNamed: true) { current_node in
      return switch CST.TableKeyEntry.Parse(node: current_node, withContext: context) {
      case .Ok(let keyset_expression): .Ok(keyset_expression)
      case .Error(let e): .Error(e)
      }
    }

    if !errors.isEmpty {
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Error(s) parsing table key: "
            + (errors.map { error in
              return "\(error.msg())"
            }.joined(separator: ";"))))
    }

    return .Ok(CST.TableKeys(withEntries: keys))
  }
}

extension CST.TableActionsProperty: Parsable {
  public typealias C = CST.TableActionsProperty
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.TableActionsProperty> {
    #RequireNodeType<Node, CST.TableActionsProperty>(
      node: node, type: "table_actions", nice_type_name: "Table Actions")

    var walker = Walker(node: node)
    // Skip the
    // actions = {
    // 1    2 3
    walker.next()  // 1
    walker.next()  // 2
    walker.next()  // 3

    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.TableActionsProperty>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing table actions declaration component in control declaration"))
    )

    let (actions, errors) = walker.try_map(n: node.childCount - 1, onlyNamed: true) {
      current_node in
      switch CST.Identifier.ParseExpression(node: current_node, withContext: context) {
      case .Ok(let listed_action):
        return .Ok(listed_action as! CST.Identifier)
      case .Error(let e): return .Error(e)
      }
    }

    if !errors.isEmpty {
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Error(s) parsing table actions: "
            + (errors.map { error in
              return "\(error.msg())"
            }.joined(separator: ";"))))
    }

    return .Ok(CST.TableActionsProperty(actions))
  }
}
extension CST.TablePropertyList: Parsable {
  public typealias C = CST.TablePropertyList
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.TablePropertyList> {

    #RequireNodeType<Node, CST.TablePropertyList>(
      node: node, type: "table_property_list", nice_type_name: "Table Property List")

    var keys: [CST.TableKeys] = Array()
    var actions: [CST.TableActionsProperty] = Array()
    var errors: [any Errorable] = Array()

    node.enumerateNamedChildren { child in
      if child.nodeType == "table_keys" {
        switch CST.TableKeys.Parse(node: child, withContext: context) {
        case .Ok(let table_key):
          keys.append(table_key)
        case .Error(let e): errors.append(e)
        }
      } else if child.nodeType == "table_actions" {
        switch CST.TableActionsProperty.Parse(node: child, withContext: context) {
        case .Ok(let table_action_property):
          actions.append(table_action_property)
        case .Error(let e): errors.append(e)
        }
      } else {
        errors.append(
          ErrorWithLocation(
            sourceLocation: child.toSourceLocation(),
            withError: "Uknown node type in control declaration"))
      }
    }

    if !errors.isEmpty {
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Error(s) parsing property list: "
            + (errors.map { error in
              return "\(error.msg())"
            }.joined(separator: ";"))))
    }

    // There should be only one table keys!
    if keys.count > 1 {
      // Todo: Make this error message better.
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "More than one key set in table property list"))
    }

    // There should be only one table actions!
    if actions.count > 1 {
      // Todo: Make this error message better.
      return .Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "More than one actions in table property list"))
    }
    if actions.isEmpty {
      actions.append(CST.TableActionsProperty())
    }

    return .Ok(CST.TablePropertyList(withActions: actions[0], withKeys: keys[0]))

  }
}

extension CST.Table: Parsable {
  public typealias C = CST.Table
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Table> {

    let table_declaration_node = node
    #RequireNodeType<Node, CST.Table>(
      node: table_declaration_node, type: "table_declaration", nice_type_name: "Table Declaration")

    var walker = Walker(node: table_declaration_node)

    var current_node: Node? = .none

    walker.next()  // Skip the XXX?
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Table>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing table declaration component")
      ))

    guard
      case .Ok(let table_name) = CST.Identifier.ParseExpression(
        node: current_node!, withContext: context)
    else {
      return Result.Error(
        Error(withMessage: "Could not parse a table name from \(current_node!.text!)"))
    }

    walker.next()
    // Skip the '{'
    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Table>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing table declaration component")
      ))

    let maybe_table_property_list = CST.TablePropertyList.Parse(
      node: current_node!, withContext: context)
    guard case .Ok(let table_property_list) = maybe_table_property_list else {
      return Result.Error(maybe_table_property_list.error()!)
    }

    return .Ok(
      CST.Table(withName: table_name as! CST.Identifier, withPropertyList: table_property_list))
  }
}

extension CST.ExternDeclaration: Parsable {
  public typealias C = CST.Categories.Declaration
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Categories.Declaration> {
    let extern_declaration_node = node
    #RequireNodeType<Node, CST.ExternDeclaration>(
      node: extern_declaration_node, type: "extern_declaration",
      nice_type_name: "Extern Declaration")

    let declaration_node = extern_declaration_node.child(at: 1)!
    #RequireNodeType<Node, CST.ExternDeclaration>(
      node: declaration_node, type: "declaration", nice_type_name: "Declaration")
    let declarationed_node = declaration_node.child(at: 0)!

    let maybe_declared = CST.Declaration.Parse(
      node: declarationed_node, withContext: context.update(withExtern: true))

    guard case .Ok(let declared) = maybe_declared else {
      return .Error(maybe_declared.error()!)
    }
    let extern_declaration = CST.ExternDeclaration(declared)

    return .Ok(
      extern_declaration,
    )
  }
}

func parameter_list_compiler(
  node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
) -> Common.Result<CST.ParameterList> {

  var walker = Walker(node: node)
  var current_node: Node? = .none

  if node.text == ")" {
    // There are no parameters!
    return Result.Ok(CST.ParameterList([]))
  }

  #RequireNodeType<Node, CST.ParameterList>(
    node: node, type: "parameter_list", nice_type_name: "Parameter List")

  var parameters: CST.ParameterList = CST.ParameterList([])

  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ParameterList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing parameter list component")))

  if current_node?.nodeType == "parameter_list" {
    switch parameter_list_compiler(node: current_node!, withContext: context) {
    case .Ok(let ps):
      parameters = ps
    case .Error(let e): return Result.Error(e)
    }
    walker.next()
  }

  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ParameterList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing parameter list component")))

  // If this is a ')', we are done.
  if current_node?.text == ")" {
    return Result.Ok(parameters)
  }

  // If this is a comma, we skip it!
  if current_node?.text == "," {
    walker.next()
  }

  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ParameterList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing parameter list component")))

  // Otherwise, there should be one parameter left!
  switch CST.Parameter.Parse(node: current_node!, withContext: context) {
  case .Ok(let parsed_parameter):
    return Result.Ok(parameters.addParameter(parsed_parameter))
  case .Error(let e): return Result.Error(e)
  }
}

extension CST.ParameterList: Parsable {
  public typealias C = CST.ParameterList
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Result<CST.ParameterList> {

    let parameter_node = node
    #RequireNodeType<Node, CST.ParameterList>(
      node: parameter_node, type: "parameters", nice_type_name: "Parameters")

    var walker = Walker(node: parameter_node)

    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.ParameterList>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing '(' in parameter list component")))

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.ParameterList>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing parameter list component")))

    return parameter_list_compiler(node: current_node!, withContext: context)
  }
}

extension Direction: Parsable {
  public typealias C = Direction
  public static func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<Direction> {
    let direction_node = node
    #RequireNodeType<Node, Direction>(
      node: direction_node, type: "direction", nice_type_name: "direction")
    let directions = [
      "in": Direction.In,
      "out": Direction.Out,
      "inout": Direction.InOut,
    ]

    guard let parsed_direction = directions[direction_node.text!] else {
      return .Error(
        ErrorWithLocation(
          sourceLocation: direction_node.toSourceLocation(),
          withError: "\(direction_node.text!) is not a valid direction"))
    }

    return .Ok(parsed_direction)
  }
}

extension CST.Parameter: Parsable {
  public typealias C = CST.Parameter
  public static func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Parameter> {

    #RequireNodeType<Node, CST.Parameter>(
      node: node, type: "parameter", nice_type_name: "parameter")

    var walker = Walker(node: node)
    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Parameter>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing parameter declaration component")))

    // Annotation?
    if current_node!.nodeType == "annotations" {
      return .Error(
        ErrorWithLocation(
          sourceLocation: current_node!.toSourceLocation(),
          withError: "Annotations in parameter declarations are not yet handled"))
      // Will increment indexes here.
    }

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Parameter>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing parameter declaration component")))

    var direction: Direction? = .none
    // Direction?
    if current_node!.nodeType == "direction" {

      let maybe_parsed_direction = Direction.Parse(node: current_node!, withContext: context)
      guard case .Ok(let parsed_direction) = maybe_parsed_direction else {
        return .Error(maybe_parsed_direction.error()!)
      }
      direction = parsed_direction

      walker.next()
    }

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Parameter>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing parameter declaration component")))

    if current_node!.nodeType != "typeRef" {
      return Result.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Did not find type name for parameter declaration"))
    }

    guard
      case .Ok(let parameter_type) = CST.Types.ParseType(
        type: current_node!, withContext: context)
    else {
      return Result.Error(
        Error(withMessage: "Could not parse a P4 type from \(current_node!.text!)"))
    }

    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.Parameter>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing parameter declaration component")))

    if current_node!.nodeType != "identifier" {
      return Result.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Did not find identifier for parameter statement"))
    }

    guard
      case .Ok(let parameter_name) = CST.Identifier.ParseExpression(
        node: current_node!, withContext: context)
    else {
      return Result.Error(
        Error(withMessage: "Could not parse a parameter name from \(current_node!.text!)"))
    }

    let qualified_parameter_type =
      direction != nil
      ? parameter_type.tipe.update(addAttribute: P4TypeQualifier.Direction(direction!))
      : parameter_type.tipe

    return Result.Ok(
      CST.Parameter(
        identifier: parameter_name as! CST.Identifier,
        withType: CST.Tipe(qualified_parameter_type)))
  }
}

func argument_list_compiler(
  node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
) -> Common.Result<CST.ArgumentList> {

  var walker = Walker(node: node)
  var current_node: Node? = .none

  if node.text == ")" {
    // There are no arguments!
    return Result.Ok(CST.ArgumentList([]))
  }

  #RequireNodeType<Node, CST.ArgumentList>(
    node: node, type: "argument_list", nice_type_name: "argument List")

  var arguments: CST.ArgumentList = CST.ArgumentList([])

  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ArgumentList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing argument list component")))

  if current_node?.nodeType == "argument_list" {
    switch argument_list_compiler(node: current_node!, withContext: context) {
    case .Ok(let ps):
      arguments = ps
    case .Error(let e): return Result.Error(e)
    }

    walker.next()
  }

  // We may have moved nodes, check/reset current_node.
  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ArgumentList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing argument list component")))

  // If this is a ')', we are done.
  if current_node?.text == ")" {
    return Result.Ok(arguments)
  }

  // If this is a comma, we skip it!
  if current_node?.text == "," {
    walker.next()
  }

  #MustOr(
    result: current_node, thing: walker.getNext(),
    or: Result<CST.ArgumentList>.Error(
      ErrorWithLocation(
        sourceLocation: node.toSourceLocation(), withError: "Missing argument list component")))

  // Otherwise, there should be one argument left!
  switch CST.Argument.Parse(node: current_node!, withContext: context) {
  case .Ok(let ce):
    return Result.Ok(
      arguments.addArgument(CST.Argument(ce, atIndex: arguments.arguments.count + 1)))
  case .Error(let e): return Result.Error(e)
  }
}

extension CST.ArgumentList: Parsable {
  public typealias C = CST.ArgumentList
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Common.Result<CST.ArgumentList> {

    let argument_node = node
    #RequireNodeType<Node, CST.ArgumentList>(
      node: argument_node, type: "arguments", nice_type_name: "arguments")

    var walker = Walker(node: argument_node)
    var current_node: Node? = .none

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.ArgumentList>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing '(' in argument list component")))

    walker.next()

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.ArgumentList>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(), withError: "Missing argument list component")))

    return argument_list_compiler(node: current_node!, withContext: context)
  }
}

extension CST.Argument: Parsable {
  public typealias C = CST.Categories.Expression
  public static func Parse(
    node: SwiftTreeSitter.Node, withContext context: CSTCompilerContext
  ) -> Common.Result<CST.Categories.Expression> {
    let argument_node = node
    #RequireNodeType<Node, CST.Categories.Expression>(
      node: argument_node, type: "argument", nice_type_name: "argument")

    let expression_node = node.child(at: 0)!

    return switch CST.Expression.Parse(node: expression_node, withContext: context) {
    case .Ok(let compiled_expression): .Ok(compiled_expression)
    case .Error(let e): .Error(e)
    }
  }
}