package wacc

import wacc.ast.Position
import wacc.types._

/** Error types for semantic errors
  */
enum Error {
  case DuplicateDeclaration(ident: ast.Ident)
  case UndeclaredVariable(ident: ast.Ident)
  case UndefinedFunction(ident: ast.Ident)

  case FunctionParamsMismatch(ident: ast.Ident, expected: Int, got: Int, funcType: FuncType)
  case SemanticError(pos: Position, msg: String)
  case TypeMismatch(pos: Position, expected: SemType, got: SemType, msg: String)
  case InternalError(pos: Position, msg: String)
}

/** Function to handle printing the details of a given semantic error
  *
  * @param error
  *   Error object
  * @param errorContent
  *   Contents of the file to generate code snippets
  */
def printError(error: Error)(using errorContent: String): Unit = {
  println("Semantic error:")
  error match {
    case Error.DuplicateDeclaration(ident) =>
      printPosition(ident.pos)
      println(s"Duplicate declaration of identifier ${ident.v}")
      highlight(ident.pos, ident.v.length)
    case Error.UndeclaredVariable(ident) =>
      printPosition(ident.pos)
      println(s"Undeclared variable ${ident.v}")
      highlight(ident.pos, ident.v.length)
    case Error.UndefinedFunction(ident) =>
      printPosition(ident.pos)
      println(s"Undefined function ${ident.v}")
      highlight(ident.pos, ident.v.length)
    case Error.FunctionParamsMismatch(id, expected, got, funcType) =>
      printPosition(id.pos)
      println(s"Function expects $expected parameters, got $got")
      println(
        s"(function ${id.v} has type (${funcType.params.mkString(", ")}) -> ${funcType.returnType})"
      )
      highlight(id.pos, 1)
    case Error.TypeMismatch(pos, expected, got, msg) =>
      printPosition(pos)
      println(s"Type mismatch: $msg\nExpected: $expected\nGot: $got")
      highlight(pos, 1)
    case Error.SemanticError(pos, msg) =>
      printPosition(pos)
      println(msg)
      highlight(pos, 1)
    case wacc.Error.InternalError(pos, msg) =>
      printPosition(pos)
      println(s"Internal error: $msg")
      highlight(pos, 1)
  }

}

/** Function to highlight a section of code for an error message
  *
  * @param pos
  *   Position of the error
  * @param size
  *   Size(in chars) of section to highlight
  * @param errorContent
  *   Contents of the file to generate code snippets
  */
def highlight(pos: Position, size: Int)(using errorContent: String): Unit = {
  val lines = errorContent.split("\n")

  val preLine = if (pos.line > 1) lines(pos.line - 2) else ""
  val midLine = lines(pos.line - 1)
  val postLine = if (pos.line < lines.size) lines(pos.line) else ""
  val linePointer = " " * (pos.column + 2) + ("^" * (size)) + "\n"

  println(
    s"  >$preLine\n  >$midLine\n$linePointer  >$postLine"
  )
}

/** Function to print the position of an error
  *
  * @param pos
  *   Position of the error
  */
def printPosition(pos: Position): Unit = {
  println(s"(line ${pos.line}, column ${pos.column}):")
}