// 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 P4Parser

public struct CSTTextSerializer {
  public init() {}
}

public struct CSTTextSerializerContext {
  public let serialized: String
  public let indents: Int

  public init(_ serialized: String = "", _ indents: Int = 0) {
    self.serialized = serialized
    self.indents = indents
  }

  static func produceIndent(_ indent: Int, _ marker: String) -> String {
    return repeatElement(marker, count: indent).joined()
  }
  public func append(_ a: String) -> CSTTextSerializerContext {
    return CSTTextSerializerContext(
      self.serialized + Self.produceIndent(self.indents, "\t") + a + "\n", self.indents)
  }

  public func indent() -> CSTTextSerializerContext {
    return CSTTextSerializerContext(self.serialized, self.indents + 1)
  }

  public func unindent() -> CSTTextSerializerContext {
    return CSTTextSerializerContext(self.serialized, self.indents - 1)
  }
}

extension CSTTextSerializer: CSTVisitor<CSTTextSerializerContext> {
  public func visit(
    node: P4Parser.CST.KeysetExpression, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("Keyset Expression:").indent()
    return .Ok(context.unindent())
    if case CST.KeysetExpression.Value(let x) = node {
      switch driver.visit(x, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
    }
    return .Ok(context.unindent())
  }

  public func visit(
    node: P4Parser.CST.SelectCaseExpression, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("Case Expression:").indent()
    switch driver.visit(node.key, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e): return .Error(e)
    }
    context = context.append("Next State:").indent()
    switch driver.visit(node.next_state_identifier, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e): return .Error(e)
    }
    context = context.unindent()
    return .Ok(context.unindent())
  }

  public func visit(
    node: P4Parser.CST.SelectExpression, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("Select Expression:").indent()
    context = context.append("Selector:").indent()
    switch driver.visit(node.selector, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e): return .Error(e)
    }
    context = context.unindent()
    context = context.append("Case Expressions:").indent()
    for ce in node.case_expressions {
      switch driver.visit(ce, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
    }
    context = context.unindent()

    return .Ok(context.unindent())
  }

  public func visit(
    node: P4Parser.CST.Statements, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context
    for s in node.statements {
      switch driver.visit(s, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
    }

    return .Ok(context)
  }

  public func visit(
    node: P4Parser.CST.ExpressionStatement, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("Expression Statement:").indent()
    switch driver.visit(node.expression, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e):
      return .Error(e)
    }
    return .Ok(context.unindent())
  }

  public func visit(
    node: P4Parser.CST.Control, driver: P4Parser.CSTVisitorDriver, context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Control Declaration"))
  }

  public func visit(
    node: P4Parser.CST.ExternDeclaration, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Extern Declaration"))
  }

  public func visit(
    node: P4Parser.CST.FunctionDeclaration, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Function Declaration"))
  }

  public func visit(
    node: P4Parser.CST.StructDeclaration, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Struct Declaration"))
  }

  public func visit(
    node: P4Parser.CST.VariableDeclarationStatement, driver: P4Parser.CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Variable Declaration Statement"))
  }

  public func visit(
    node: CST.BinaryOperatorExpression, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Binary Operator Expression"))
  }

  public func visit(
    node: CST.Literal, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Literal Expression"))
  }

  public func visit(
    node: CST.Identifier, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("Identifier: \(node.id)"))
  }

  public func visit(
    node: CST.Parser, driver: CSTVisitorDriver, context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("Parser Expression")
    context = context.indent()
    for s in node.states.states {
      switch driver.visit(s, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
    }
    return .Ok(context.unindent())
  }

  public func visit(
    node: CST.ParserStateDirectTransition, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    var context = context.append("State: Direct Transition").indent()
    context = context.append("Statements:")
    context = context.indent()
    if let statements = node.statements {
      switch driver.visit(statements, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
    }
    context = context.unindent()
    context = context.append("Next State:").indent()
    switch driver.visit(node.next_state_identifier!, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e): return .Error(e)
    }
    context = context.unindent()
    return .Ok(context.unindent())
  }

  public func visit(
    node: CST.ParserStateNoTransition, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {
    return .Ok(context.append("State: No Transition"))
  }

  public func visit(
    node: CST.ParserStateSelectTransition, driver: CSTVisitorDriver,
    context: CSTTextSerializerContext
  ) -> Common.Result<CSTTextSerializerContext> {

    var context = context.append("State: Select Transition").indent()
    if let statements = node.statements {
      context = context.indent()
      switch driver.visit(statements, visitor: self, context: context) {
      case .Ok(let c): context = c
      case .Error(let e): return .Error(e)
      }
      context = context.unindent()
    }
    switch driver.visit(node.te, visitor: self, context: context) {
    case .Ok(let c): context = c
    case .Error(let e): return .Error(e)
    }

    return .Ok(context.unindent())
  }
}