gp4/Sources/Common/Protocols.swift

// 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 P4Type: CustomStringConvertible {
  func eq(rhs: any P4Type) -> Bool
  func def() -> P4DataValue?
  func instantiable() -> Bool
}

extension P4Type {
  public func instantiable() -> Bool {
    return false
  }
}

public protocol P4DataValue: CustomStringConvertible {
  func type() -> any P4Type
  func eq(rhs: P4DataValue) -> Bool
  func lt(rhs: P4DataValue) -> Bool
  func lte(rhs: P4DataValue) -> Bool
  func gt(rhs: P4DataValue) -> Bool
  func gte(rhs: P4DataValue) -> Bool
}

public protocol Errorable: CustomStringConvertible {
  func format(_ formatter: Formattable) -> String
  func format(_ formatter: Formattable, _ sc: SourceCode) -> String
  func msg() -> String
  func append(error: any Errorable) -> any Errorable
  func eq(_ rhs: any Errorable) -> Bool
}

extension Errorable {
  public func eq(_ rhs: any Errorable) -> Bool {
    return self.msg() == rhs.msg()
  }
  public func format(_ formatter: Formattable, _ sc: SourceCode) -> String {
    return self.format(formatter)
  }
}

public protocol Formattable {
  func formatWithStyle(_ value: String, _ style: Style) -> String
}

public protocol P4Statement {
  /// Evaluate a statement for a given execution
  /// - Parameters
  ///  - execution: The execution context in which to evaluate the parser statement
  /// - Returns: A tuple of
  /// 1. Whether this statement affects control flow.
  /// 2. An updated execution after evaluating the parser statement
  func evaluate(execution: ProgramExecution) -> (ControlFlow, ProgramExecution)

  func effect(context: CompilerContext) -> CompilerContext
}

public protocol P4Expression {
  func effect(context: CompilerContext) -> CompilerContext
  func type() -> P4QualifiedType
  /// 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) -> (Result<P4Value>, ProgramExecution)
}

extension P4Expression {
  func effect(context: CompilerContext) -> CompilerContext {
    return context
  }
}

public protocol P4LValueExpression {
  func effect(context: CompilerContext) -> CompilerContext
  func type() -> P4QualifiedType
  func check(to: P4Expression, inScopes scopes: StaticVarValueScopes) -> Result<()>
  func set(
    to: P4Value, inScopes scopes: VarValueScopes, duringExecution execution: ProgramExecution
  ) -> Result<(VarValueScopes, P4Value)>

}

/// TODO: Only generate these after going through the codegen!
public typealias EvaluatableStatement = P4Statement
public typealias EvaluatableLValueExpression = P4LValueExpression
public typealias EvaluatableExpression = P4Expression

public protocol ProgramExecutionEvaluator {
  func ExecuteStatements(
    _ statements: [EvaluatableStatement], inExecution execution: ProgramExecution,
    _ handler: ExecuteStatementResultHandlerT?
  ) -> (ControlFlow, ProgramExecution)

  func ExecuteStatements(
    _ statements: [EvaluatableStatement], inExecution execution: ProgramExecution
  ) -> (ControlFlow, ProgramExecution)

  func EvaluateExpression(
    _ expression: EvaluatableExpression, inExecution execution: ProgramExecution,
  ) -> (Result<P4Value>, ProgramExecution)
}

extension ProgramExecutionEvaluator {
  public func ExecuteStatements(
    _ statements: [EvaluatableStatement], inExecution execution: ProgramExecution
  ) -> (ControlFlow, ProgramExecution) {
    return ExecuteStatements(statements, inExecution: execution, .none)
  }
}