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// The MIT License (MIT)
//
// Copyright (c) 2017 Doublify Technologies
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

use std::cell::RefCell;
use std::iter::Peekable;

/// Kind of token
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Kind {
  /// String
  String,
  /// Integer
  Integer,
  /// Boolean
  Boolean,
  /// Identifier
  Identifier,
  /// Curly brace
  Curly,
  /// Parentheses
  Parentheses,
  /// Colon
  Colon,
}

/// Token
#[derive(Clone, Debug, PartialEq)]
pub struct Token {
  /// Kind
  pub kind: Kind,
  /// Value
  pub binding: String,
}

impl Token {
  /// Creates token from static string slice
  pub fn new(kind: Kind, binding: &'static str) -> Token {
    Token {
      kind,
      binding: String::from(binding),
    }
  }

  /// Changes token kind and returns new token
  pub fn change_kind(&self, kind: Kind) -> Token {
    Token {
      kind,
      binding: self.binding.to_owned(),
    }
  }
}

/// Handles string
fn tokenize_string<'a, It>(it: &mut Peekable<It>,
                           buffer: &RefCell<String>,
                           ch: char)
                           -> Result<String, &'a str>
  where It: Iterator<Item = char>
{
  let mut escaped = false;
  let quote = ch.clone();
  let quote_str = quote;

  while let Some(ch) = it.peek().map(|c| *c) {
    if escaped {
      buffer.borrow_mut().push(ch);
      escaped = false;
    } else if ch == '\\' {
      escaped = true;
    } else if ch == quote {
      it.next();
      let mut result = String::new();
      result.push(quote_str);
      result.push_str(buffer.borrow().as_str());
      result.push(quote_str);

      return Ok(result);
    } else {
      buffer.borrow_mut().push(ch);
    }

    it.next();
  }

  Err("Can't parse string")
}

/// Scans query
pub fn scan(raw_query: &str) -> Vec<Token> {
  let query = raw_query.to_owned() + " ";
  let mut it = query.chars().peekable();
  let tokens = RefCell::new(vec![]);
  let buffer = RefCell::new(String::new());

  let bind_identifier = |binding: String| if !binding.is_empty() {
    tokens
      .borrow_mut()
      .push(
        Token {
          kind: Kind::Identifier,
          binding,
        },
      );

    buffer.borrow_mut().clear()
  };

  let consume_token = |token: Token| {
    bind_identifier(buffer.clone().into_inner());

    tokens.borrow_mut().push(token)
  };

  while let Some(ch) = it.next() {
    match ch {
      '"' | '\'' => {
        let str = tokenize_string(&mut it, &buffer, ch).unwrap();
        bind_identifier(str);
      }
      ' ' => bind_identifier(buffer.clone().into_inner()),
      ':' => consume_token(Token::new(Kind::Colon, ":")),
      '{' => consume_token(Token::new(Kind::Curly, "{")),
      '}' => consume_token(Token::new(Kind::Curly, "}")),
      '(' => consume_token(Token::new(Kind::Parentheses, "(")),
      ')' => consume_token(Token::new(Kind::Parentheses, ")")),
      _ => buffer.borrow_mut().push(ch),
    }

    if ch != '"' || ch != '\'' {
      continue;
    }
  }

  tokens.to_owned().into_inner()
}