// 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/>.

/// A scope that resolves variable identifiers to their types.
public typealias VarTypeScope = Scope<P4QualifiedType>

/// Scopes that resolve variable identifiers to their types.
public typealias VarTypeScopes = Scopes<P4QualifiedType>

/// A scope that resolves type identifiers to their types.
public typealias TypeTypeScope = Scope<P4Type>

/// Scopes that resolve type identifiers to their types.
public typealias TypeTypeScopes = Scopes<P4Type>

/// Context for compilation
///
/// It contains (at least) three important pieces of information:
/// 1. Instances: A ``VarTypeScopes`` that contains information about instantiated objects
/// (and their types) in scope
/// 1. Types: A ``TypeTypeScopes`` that contains information about declared types in scope.
/// 1. Expected Type: In certain situations, to typecheck an element of a P4 program requires
/// knowledge of an expected type. For instance, when compiling a return statement, the
/// compiler must know the return type of the function to type check.
public struct CompilerContext {
  public let instances: StaticVarValueScopes
  public let types: TypeTypeScopes
  public let externs: TypeTypeScopes
  public let ffis: [P4FFI]
  public let expected_type: P4QualifiedType?
  public let extern_context: Bool

  public init() {
    instances = StaticVarValueScopes().enter()
    types = TypeTypeScopes().enter()
    externs = TypeTypeScopes().enter()
    expected_type = .none
    extern_context = false
    ffis = Array()
  }

  public init(withInstances _instances: StaticVarValueScopes, withTypes _types: TypeTypeScopes) {
    instances = _instances
    types = _types
    externs = TypeTypeScopes().enter()
    expected_type = .none
    extern_context = false
    ffis = Array()
  }

  public init(
    withInstances _instances: StaticVarValueScopes, withTypes _types: TypeTypeScopes,
    withExpectation expectation: P4QualifiedType?, withExtern extern: Bool,
    withExterns externs: TypeTypeScopes, withFFIs foreigns: [P4FFI]
  ) {
    instances = _instances
    types = _types
    expected_type = expectation
    extern_context = extern
    self.externs = externs
    ffis = foreigns
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new instances.
  ///
  /// - Parameter instances: a ``VarTypeScopes`` with the updated instances for the newly created compiler context.
  /// - Returns: A new compiler context based on the current but new instances.
  public func update(newInstances instances: StaticVarValueScopes) -> CompilerContext {
    return CompilerContext(
      withInstances: instances, withTypes: self.types, withExpectation: self.expected_type,
      withExtern: self.extern_context, withExterns: self.externs, withFFIs: self.ffis)
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new types.
  ///
  /// - Parameter types: a ``TypeTypeScopes`` with the updated types for the newly created compiler context.
  /// - Returns: A new compiler context based on the current but new types.
  public func update(newTypes types: TypeTypeScopes) -> CompilerContext {
    return CompilerContext(
      withInstances: self.instances, withTypes: types, withExpectation: self.expected_type,
      withExtern: self.extern_context, withExterns: self.externs, withFFIs: self.ffis)
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new expected type.
  ///
  /// - Parameter expectation: a ``P4Type?`` to (re)set the type the compiler is expecting.
  /// - Returns: A new compiler context based on the current but new expected type.
  public func update(newExpectation expectation: P4QualifiedType?) -> CompilerContext {
    return CompilerContext(
      withInstances: self.instances, withTypes: self.types, withExpectation: expectation,
      withExtern: self.extern_context, withExterns: self.externs, withFFIs: self.ffis)
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new extern context value.
  ///
  /// - Parameter extern: a ``Bool`` to (re)set whether the compiler is compiling in an extern context.
  /// - Returns: A new compiler context based on the current but new extern context value.
  public func update(newExtern extern: Bool) -> CompilerContext {
    return CompilerContext(
      withInstances: self.instances, withTypes: self.types, withExpectation: self.expected_type,
      withExtern: extern, withExterns: self.externs, withFFIs: self.ffis)
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new externs.
  ///
  /// - Parameter externs: a ``TypeTypeScopes`` to (re)set the list of extern-al declarations.
  /// - Returns: A new compiler context based on the current but new list of external-al declarations.
  public func update(newExterns externs: TypeTypeScopes) -> CompilerContext {
    return CompilerContext(
      withInstances: self.instances, withTypes: self.types, withExpectation: self.expected_type,
      withExtern: self.extern_context, withExterns: externs, withFFIs: self.ffis)
  }

  /// Update a compiler context
  ///
  /// Create a new compiler context based on the current but new FFIs.
  ///
  /// - Parameter foreigns: an array of ``P4FFI`` to (re)set the list of foreign functions.
  /// - Returns: A new compiler context based on the current but with a new list of foreign functions.
  public func update(newFFIs foreigns: [P4FFI]) -> CompilerContext {
    return CompilerContext(
      withInstances: self.instances, withTypes: self.types, withExpectation: self.expected_type,
      withExtern: self.extern_context, withExterns: externs, withFFIs: foreigns)
  }
}