gp4/Sources/Common/Error.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 struct Error: Errorable, Equatable, CustomStringConvertible {
  public func format(_ formatter: any Formattable) -> String {
    return self._msg
  }

  public func msg() -> String {
    return self._msg
  }

  public func append(error: any Errorable) -> any Errorable {
    return Errors(self, error)
  }

  let _msg: String

  public init(withMessage msg: String) {
    self._msg = msg
  }

  public var description: String {
    return self._msg
  }
}

extension String {
  public func trimmingPostfix(_ in_: String.Element) -> String {
    return String(self.reversed().drop { $0 == in_ }.reversed())
  }
}

public struct ErrorWithLocation: Errorable, Equatable, CustomStringConvertible {

  public func format(_ formatter: any Formattable, _ sc: SourceCode) -> String {
    guard let (fp, source, prior, after) = sc.getSourceSnippet(location: self.location, context: 5)
    else {
      return self.format(formatter)
    }

    let prior_snipped = prior.trimmingPrefix(["\n"])
    let after_snipped = after.prefix { $0 != "\n" }
    let include_list = fp.reversed().map {
      let at =
        if let whence = $0.whence {
          " included at position \(whence) in"
        } else {
          ""
        }
      return $0.path.string + at
    }.joined(separator: " ")
    return formatter.formatWithStyle("Error: ", Style(StyleColor.Red))
      + "In \(include_list), there was an error: \n..." + prior_snipped
      + formatter.formatWithStyle(source, Style(.none, [StyleFormat.Underline])) + after_snipped
      + "...\n"
      + self._msg
  }

  public func format(_ formatter: any Formattable) -> String {
    let bold_red = Style(StyleColor.Red, [StyleFormat.Bold])
    let formatted_location = formatter.formatWithStyle(self.location.description, bold_red)
    return formatted_location + ": " + self._msg
  }

  public func msg() -> String {
    return self.description
  }

  public func append(error: any Errorable) -> any Errorable {
    return Errors(self, error)
  }

  let _msg: String

  let location: SourceLocation

  public init(sourceLocation location: SourceLocation, withError msg: String) {
    self._msg = msg
    self.location = location
  }

  public var description: String {
    return "\(self.location): \(self._msg)"
  }
}

public struct Errors: Errorable, CustomStringConvertible {
  public func format(_ formatter: any Formattable) -> String {
    self.errors.map { error in
      error.format(formatter)
    }.joined(separator: "\n")
  }

  public func msg() -> String {
    return self.description
  }

  public func append(error: any Errorable) -> any Errorable {
    return Errors(self.errors + [error])
  }

  public var description: String {
    return self.errors.map { error in
      return error.msg()
    }.joined(separator: ";")
  }

  public let errors: [any Errorable]

  init(_ errors: [any Errorable]) {
    self.errors = errors
  }

  public init(_ e1: any Errorable, _ e2: any Errorable) {
    self.errors = [e1, e2]
  }
}

public struct ErrorWithLabel: Errorable {
  let label: String
  let error: any Errorable

  public func format(_ formatter: any Formattable) -> String {
    let green = Style(StyleColor.Green)
    let formatted_label = formatter.formatWithStyle(self.label, green)
    return formatted_label + ": " + self.error.format(formatter)
  }

  public init(_ label: String, _ error: any Errorable) {
    self.label = label
    self.error = error
  }

  public func format() -> String {
    return self.description
  }

  public func msg() -> String {
    return self.description
  }

  public func append(error: any Errorable) -> any Errorable {
    return Errors(self, error)
  }

  public var description: String {
    return "\(self.label): \(self.error.msg())"
  }
}