//! calculation + conversion
//! 
//! cpc parses and evaluates strings of math, with support for units and conversion. 128-bit decimal floating points are used for high accuracy.
//! 
//! cpc lets you mix units, so for example 1 km - 1m results in Number { value: 999, unit: Meter }.
//! 
//! Check out the [list of supported units](units/enum.Unit.html)
//! 
//! # Example usage
//! ```rust
//! use cpc::{eval, Unit::*}
//! 
//! match eval("3m + 1cm", true, Celcius) {
//!     Ok(answer) => {
//!         // answer: Number { value: 301, unit: Unit::cm }
//!         println!("Evaluated value: {} {:?}", answer.value, answer.unit)
//!     },
//!     Err(e) => {
//!         println!(e)
//!     }
//! }
//! ```

use std::time::{Instant};
use decimal::d128;
use crate::units::Unit;

/// Units, and functions you can use with them
pub mod units;
/// Turns a string into a [`TokenVector`](type.TokenVector.html)
pub mod lexer;
/// Turns a [`TokenVector`](type.TokenVector.html) into an [`AstNode`](struct.AstNode.html)
pub mod parser;
/// Turns an [`AstNode`](struct.AstNode.html) into a [`Number`](struct.Number.html)
pub mod evaluator;
mod lookup;

#[derive(Clone, Debug)]
/// A number with a `Unit`.
/// 
/// Example:
/// ```rust
/// use cpc::{eval,Number};
/// use cpc::units::Unit;
/// use decimal::d128;
/// 
/// let x = Number {
///   value: d128!(100),
///   unit: Unit::Meter,
/// };
/// ```
pub struct Number {
  /// The number part of a `Number` struct
  pub value: d128,
  /// The unit of a `Number` struct. This can be `NoType`
  pub unit: Unit,
}

impl Number {
  pub fn new(value: d128, unit: Unit) -> Number {
    Number {
      value: value,
      unit: unit,
    }
  }
}

#[derive(Clone, Debug)]
/// Math operators like [`Multiply`](enum.Operator.html#variant.Multiply), parentheses, etc.
pub enum Operator {
  Plus,
  Minus,
  Multiply,
  Divide,
  Modulo,
  Caret,
  LeftParen, // lexer only
  RightParen, // lexer only
}

#[derive(Clone, Debug)]
/// Unary operators like [`Percent`](enum.UnaryOperator.html#variant.Percent) and [`Factorial`](enum.UnaryOperator.html#variant.Factorial).
pub enum UnaryOperator {
  Percent,
  Factorial,
}

#[derive(Clone, Debug)]
/// A Text operator like [`To`](enum.TextOperator.html#variant.To) or [`From`](enum.TextOperator.html#variant.From).
pub enum TextOperator {
  To,
  Of,
}

#[derive(Clone, Debug)]
/// A constants like [`Pi`](enum.Constant.html#variant.Pi) or [`E`](enum.Constant.html#variant.E).
pub enum Constant {
  Pi,
  E,
}

#[derive(Clone, Debug)]
/// Functions identifiers like [`Sqrt`](enum.FunctionIdentifier.html#variant.Sqrt), [`Sin`](enum.FunctionIdentifier.html#variant.Sin), [`Round`](enum.FunctionIdentifier.html#variant.Round), etc.
pub enum FunctionIdentifier {
  Sqrt,
  Cbrt,

  Log,
  Ln,
  Exp,
  
  Round,
  Ceil,
  Floor,
  Abs,

  Sin,
  Cos,
  Tan,
}

#[derive(Clone, Debug)]
/// A temporary enum used by the [`lexer`](lexer/index.html) to later determine what [`Token`](enum.Token.html) it is.
/// 
/// For example, when a symbol like `%` is found, the lexer turns it into a
/// the [`PercentChar`](enum.LexerKeyword.html#variant.PercentChar) variant
/// and then later it checks the surrounding [`Token`](enum.Token.html)s and,
/// dependingon them, turns it into a [`Percent`](enum.UnaryOperator.html) or
/// [`Modulo`](enum.Operator.html) [`Token`](enum.Token.html).
pub enum LexerKeyword {
  Per,
  PercentChar,
  In,
  DoubleQuotes,
  Mercury,
  Hg,
  PoundForce,
  PoundWord,
  Force,
}

#[derive(Clone, Debug)]
/// A token like a [`Number`](enum.Token.html#variant.Number), [`Operator`](enum.Token.html#variant.Operator), [`Unit`](enum.Token.html#variant.Unit) etc.
/// 
/// Strings can be divided up into these tokens by the [`lexer`](lexer/index.html), and then put into the [`parser`](parser/index.html).
pub enum Token {
  Operator(Operator),
  UnaryOperator(UnaryOperator),
  Number(d128),
  FunctionIdentifier(FunctionIdentifier),
  Constant(Constant),
  /// Used by the parser only
  Paren,
  /// Used by the lexer only
  Per,
  /// Used by the parser only
  LexerKeyword(LexerKeyword),
  TextOperator(TextOperator),
  /// The `-` symbol, specifically when used as `-5` and not `5-5`. Used by the parser only
  Negative,
  Unit(units::Unit),
}

/// A vector of [`Token`](enum.Token.html)
pub type TokenVector = Vec<Token>;

/// Evaluates a string into a resulting [`Number`]().
/// 
/// Example:
/// ```rust
/// use cpc::{eval};
/// use cpc::units::Unit;
/// 
/// match eval("3m + 1cm", true, Unit::Celcius, false) {
///     Ok(answer) => {
///         // answer: Number { value: 301, unit: Unit::Centimeter }
///         println!("Evaluated value: {} {:?}", answer.value, answer.unit)
///     },
///     Err(e) => {
///         println!("{}", e)
///     }
/// }
/// ```
pub fn eval(input: &str, allow_trailing_operators: bool, default_degree: Unit, debug: bool) -> Result<Number, String> {

  let lex_start = Instant::now();

  match lexer::lex(input, allow_trailing_operators, default_degree) {
    Ok(tokens) => {
      let lex_time = Instant::now().duration_since(lex_start).as_nanos() as f32;

      let parse_start = Instant::now();
      match parser::parse(&tokens) {
        Ok(ast) => {
          let parse_time = Instant::now().duration_since(parse_start).as_nanos() as f32;

          let eval_start = Instant::now();
          match evaluator::evaluate(&ast) {
            Ok(answer) => {
              let eval_time = Instant::now().duration_since(eval_start).as_nanos() as f32;

              if debug == true {
                println!("Lexed TokenVector: {:?}", tokens);
                println!("Parsed AstNode: {:#?}", ast);
                println!("Evaluated value: {} {:?}", answer.value, answer.unit);
                println!("\u{23f1}  {:.3}ms lexing", lex_time/1000.0/1000.0);
                println!("\u{23f1}  {:.3}ms parsing", parse_time/1000.0/1000.0);
                println!("\u{23f1}  {:.3}ms evaluation", eval_time/1000.0/1000.0);
              }

              return Ok(answer)
            },
            Err(e) => Err(format!("Eval error: {}", e)),
          }
          
        },
        Err(e) => Err(format!("Parsing error: {}", e)),
      }

    },
    Err(e) => Err(format!("Lexing error: {}", e)),
  }
  
}