use std::str::FromStr;
use std::convert::TryFrom;

use crate::typechecking::{TypeConst, Type};
use crate::ast::{BinOp, PrefixOp};

/// "Builtin" computational operations with some kind of semantics, mostly mathematical operations.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Builtin {
  Add,
  Increment,
  Subtract,
  Negate,
  Multiply,
  Divide,
  Quotient,
  Modulo,
  Exponentiation,
  BitwiseAnd,
  BitwiseOr,
  BooleanAnd,
  BooleanOr,
  BooleanNot,
  Equality,
  LessThan,
  LessThanOrEqual,
  GreaterThan,
  GreaterThanOrEqual,
  Comparison,
  FieldAccess,
  IOPrint,
  IOPrintLn,
  IOGetLine,
  Assignment,
  Concatenate,
}

impl Builtin {
  pub fn get_type(&self) -> Type {
    use Builtin::*;
    match self {
      Add => ty!(Nat -> Nat -> Nat),
      Subtract => ty!(Nat -> Nat -> Nat),
      Multiply => ty!(Nat -> Nat -> Nat),
      Divide => ty!(Nat -> Nat -> Float),
      Quotient => ty!(Nat -> Nat -> Nat),
      Modulo => ty!(Nat -> Nat -> Nat),
      Exponentiation => ty!(Nat -> Nat -> Nat),
      BitwiseAnd => ty!(Nat -> Nat -> Nat),
      BitwiseOr => ty!(Nat -> Nat -> Nat),
      BooleanAnd => ty!(Bool -> Bool -> Bool),
      BooleanOr => ty!(Bool -> Bool -> Bool),
      BooleanNot => ty!(Bool -> Bool),
      Equality => ty!(Nat -> Nat -> Bool),
      LessThan => ty!(Nat -> Nat -> Bool),
      LessThanOrEqual => ty!(Nat -> Nat -> Bool),
      GreaterThan => ty!(Nat -> Nat -> Bool),
      GreaterThanOrEqual => ty!(Nat -> Nat -> Bool),
      Comparison => ty!(Nat -> Nat -> Ordering),
      FieldAccess => ty!(Unit),
      IOPrint => ty!(Unit),
      IOPrintLn => ty!(Unit) ,
      IOGetLine => ty!(StringT),
      Assignment => ty!(Unit),
      Concatenate => ty!(StringT -> StringT -> StringT),
      Increment => ty!(Nat -> Int),
      Negate => ty!(Nat -> Int)
    }
  }
}

impl TryFrom<&BinOp> for Builtin {
  type Error = ();

  fn try_from(binop: &BinOp) -> Result<Self, Self::Error> {
    FromStr::from_str(binop.sigil())
  }
}

impl TryFrom<&PrefixOp> for Builtin {
  type Error = ();

  fn try_from(prefix_op: &PrefixOp) -> Result<Self, Self::Error> {
    use Builtin::*;

    match prefix_op.sigil() {
      "+" => Ok(Increment),
      "-" => Ok(Negate),
      "!" => Ok(BooleanNot),
      _ => Err(())
    }
  }
}

impl FromStr for Builtin {
  type Err = ();

  fn from_str(s: &str) -> Result<Self, Self::Err> {
    use Builtin::*;
    Ok(match s {
      "+" => Add,
      "-" => Subtract,
      "*" => Multiply,
      "/" => Divide,
      "quot" => Quotient,
      "%" => Modulo,
      "++" => Concatenate,
      "^" =>  Exponentiation,
      "&" => BitwiseAnd,
      "&&" => BooleanAnd,
      "|" => BitwiseOr,
      "||" => BooleanOr,
      "!" => BooleanNot,
      ">" => GreaterThan,
      ">=" => GreaterThanOrEqual,
      "<" => LessThan,
      "<=" => LessThanOrEqual,
      "==" => Equality,
      "=" => Assignment,
      "<=>" => Comparison,
      "." => FieldAccess,
      "print" => IOPrint,
      "println" => IOPrintLn,
      "getline" => IOGetLine,
      _ => return Err(())
    })
  }
}