// 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.LocalElements: Parsable {
  public typealias C = CST.Statement
  public static func Parse(
    node: Node, withContext context: CSTCompilerContext
  ) -> Result<CST.Statement> {
    let localElementsParsers: [String: ParsableStatement.Type] = [
      "variableDeclaration": CST.VariableDeclarationStatement.self
    ]

    guard let parser = localElementsParsers[node.nodeType ?? ""] else {
      return Result.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Unparseable statement type (\(node.nodeType ?? "Unknown Statement Type"))"))
    }

    switch parser.ParseStatement(node: node, withContext: context) {
    case Result.Ok(let parsed):
      return Result.Ok(parsed)
    case Result.Error(let e):
      return Result.Error(Error(withMessage: "Failed to parse local element: \(e)"))
    }
  }
}

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

    var current_node: Node? = .none

    guard let node_type = node.nodeType,
      node_type == "parserState"
    else {
      return Result.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Did not find a parser state declaration"))
    }

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.AnState>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing elements in parser state declaration")))

    if current_node!.nodeType == "annotations" {
      return Result.Error(
        ErrorWithLocation(
          sourceLocation: current_node!.toSourceLocation(),
          withError: "Annotations in parser state are not yet handled."))

      // Would increment here.
    }

    // Skip the keyword state
    walker.next()
    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.AnState>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing elements in parser state declaration")))

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

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

    var errors: (any Errorable)? = .none
    var parsed_s: CST.Statements? = .none

    if current_node!.nodeType == "parserStatements" {
      switch CST.Statements.Parse(
        node: current_node!, withContext: context)
      {
      case .Ok(let state_statements):
        parsed_s = state_statements
      case .Error(let error):
        errors =
          if let errors = errors {
            errors.append(error: error)
          } else {
            error
          }
      }
      walker.next()
    }

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

    #MustOr(
      result: current_node, thing: walker.getNext(),
      or: Result<CST.AnState>.Error(
        ErrorWithLocation(
          sourceLocation: node.toSourceLocation(),
          withError: "Missing transition statement of state declaration")))

    let updated_context = context.update(withContextName: (state_identifier as! CST.Identifier))
      .update(withContextStatements: parsed_s)

    return CST.TransitionStatement.Parse(node: current_node!, withContext: updated_context)
  }
}