/// The tokenizer for the query interpreter
use crate::error::{Error, Result};

#[derive(Debug, PartialEq, Eq)]
pub enum Token {
    Identifier {
        ident: String,
        next: Option<Box<Token>>,
    },

    Index {
        idx: usize,
        next: Option<Box<Token>>,
    },
}

impl Token {
    pub fn next(&self) -> Option<&Token> {
        trace!("Matching token (self): {:?}", self);
        match self {
            Token::Identifier { ref next, .. } => next.as_ref().map(|t| &**t),
            Token::Index { ref next, .. } => next.as_ref().map(|t| &**t),
        }
    }

    /// Convenience function for `token.next().is_some()`
    pub fn has_next(&self) -> bool {
        trace!("self.has_next(): {:?}", self.next().is_some());
        self.next().is_some()
    }

    pub fn set_next(&mut self, token: Token) {
        trace!("self.set_next({:?})", token);
        match self {
            Token::Identifier { ref mut next, .. } => *next = Some(Box::new(token)),
            Token::Index { ref mut next, .. } => *next = Some(Box::new(token)),
        }
    }

    /// Pop the last token from the chain of tokens
    ///
    /// Returns None if the current Token has no next token
    pub fn pop_last(&mut self) -> Option<Box<Token>> {
        trace!("self.pop_last()");
        if !self.has_next() {
            trace!("self.pop_last(): No next");
            None
        } else {
            trace!("self.pop_last(): Having next");
            match self {
                Token::Identifier { ref mut next, .. } => {
                    trace!("self.pop_last(): self is Identifier");
                    if next.is_some() {
                        trace!("self.pop_last(): next is Some(_)");
                        let mut n = next.take().unwrap();
                        if n.has_next() {
                            trace!("self.pop_last(): next also has a next");

                            trace!("self.pop_last(): Recursing now");
                            let result = n.pop_last();

                            *next = Some(n);

                            trace!("self.pop_last(): Returning Result");
                            result
                        } else {
                            trace!("self.pop_last(): next itself has no next, returning Some");
                            Some(n)
                        }
                    } else {
                        trace!("self.pop_last(): next is none, returning None");
                        None
                    }
                }

                Token::Index { ref mut next, .. } => {
                    trace!("self.pop_last(): self is Index");
                    if next.is_some() {
                        trace!("self.pop_last(): next is Some(_)");

                        let mut n = next.take().unwrap();
                        if n.has_next() {
                            trace!("self.pop_last(): next also has a next");

                            trace!("self.pop_last(): Recursing now");
                            let result = n.pop_last();

                            *next = Some(n);

                            trace!("self.pop_last(): Returning Result");
                            result
                        } else {
                            trace!("self.pop_last(): next itself has no next, returning Some");
                            Some(n)
                        }
                    } else {
                        trace!("self.pop_last(): next is none, returning None");
                        None
                    }
                }
            }
        }
    }

    #[cfg(test)]
    pub fn identifier(&self) -> &String {
        trace!("self.identifier()");
        match self {
            Token::Identifier { ref ident, .. } => &ident,
            _ => unreachable!(),
        }
    }

    #[cfg(test)]
    pub fn idx(&self) -> usize {
        trace!("self.idx()");
        match self {
            Token::Index { idx: i, .. } => *i,
            _ => unreachable!(),
        }
    }
}

pub fn tokenize_with_seperator(query: &str, seperator: char) -> Result<Token> {
    use std::str::Split;
    trace!(
        "tokenize_with_seperator(query: {:?}, seperator: {:?})",
        query,
        seperator
    );

    /// Creates a Token object from a string
    ///
    /// # Panics
    ///
    /// * If the internal regex does not compile (should never happen)
    /// * If the token is non-valid (that is, a array index with a non-i64)
    /// * If the regex does not find anything
    /// * If the integer in the brackets (`[]`) cannot be parsed to a valid i64
    ///
    /// # Incorrect behaviour
    ///
    /// * If the regex finds multiple captures
    ///
    /// # Returns
    ///
    /// The `Token` object with the correct identifier/index for this token and no next token.
    ///
    fn mk_token_object(s: &str) -> Result<Token> {
        use regex::Regex;
        use std::str::FromStr;

        trace!("mk_token_object(s: {:?})", s);

        lazy_static! {
            static ref RE: Regex = Regex::new(r"^\[\d+\]$").unwrap();
        }

        if !has_array_brackets(s) {
            trace!("returning Ok(Identifier(ident: {:?}, next: None))", s);
            return Ok(Token::Identifier {
                ident: String::from(s),
                next: None,
            });
        }

        match RE.captures(s) {
            None => Err(Error::ArrayAccessWithoutIndex),
            Some(captures) => {
                trace!("Captured: {:?}", captures);
                match captures.get(0) {
                    None => Ok(Token::Identifier {
                        ident: String::from(s),
                        next: None,
                    }),
                    Some(mtch) => {
                        trace!("First capture: {:?}", mtch);

                        let mtch = without_array_brackets(mtch.as_str());
                        trace!(".. without array brackets: {:?}", mtch);

                        let i: usize = FromStr::from_str(&mtch).unwrap(); // save because regex

                        trace!("returning Ok(Index(idx: {}, next: None)", i);
                        Ok(Token::Index { idx: i, next: None })
                    }
                }
            }
        }
    }

    /// Check whether a str begins with '[' and ends with ']'
    fn has_array_brackets(s: &str) -> bool {
        trace!("has_array_brackets({:?})", s);
        s.as_bytes()[0] == b'[' && s.as_bytes()[s.len() - 1] == b']'
    }

    /// Remove '[' and ']' from a str
    fn without_array_brackets(s: &str) -> String {
        trace!("without_array_brackets({:?})", s);
        s.replace("[", "").replace("]", "")
    }

    fn build_token_tree(split: &mut Split<'_, char>, last: &mut Token) -> Result<()> {
        trace!("build_token_tree(split: {:?}, last: {:?})", split, last);
        match split.next() {
            None => { /* No more tokens */ }
            Some(token) => {
                trace!("build_token_tree(...): next from split: {:?}", token);

                if token.is_empty() {
                    trace!("build_token_tree(...): Empty identifier... returning Error");
                    return Err(Error::EmptyIdentifier);
                }

                let mut token = mk_token_object(token)?;
                build_token_tree(split, &mut token)?;
                last.set_next(token);
            }
        }

        trace!("build_token_tree(...): returning Ok(())");
        Ok(())
    }

    if query.is_empty() {
        trace!("Query is empty. Returning error");
        return Err(Error::EmptyQueryError);
    }

    let mut tokens = query.split(seperator);
    trace!("Tokens splitted: {:?}", tokens);

    match tokens.next() {
        None => Err(Error::EmptyQueryError),
        Some(token) => {
            trace!("next Token: {:?}", token);

            if token.is_empty() {
                trace!("Empty token. Returning Error");
                return Err(Error::EmptyIdentifier);
            }

            let mut tok = mk_token_object(token)?;
            build_token_tree(&mut tokens, &mut tok)?;

            trace!("Returning Ok({:?})", tok);
            Ok(tok)
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::error::Error;

    use std::ops::Deref;

    #[test]
    fn test_tokenize_empty_query_to_error() {
        let tokens = tokenize_with_seperator(&String::from(""), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::EmptyQueryError { .. }));
    }

    #[test]
    fn test_tokenize_seperator_only() {
        let tokens = tokenize_with_seperator(&String::from("."), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::EmptyIdentifier { .. }));
    }

    #[test]
    fn test_tokenize_array_brackets_only() {
        let tokens = tokenize_with_seperator(&String::from("[]"), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::ArrayAccessWithoutIndex { .. }));
    }

    #[test]
    fn test_tokenize_identifiers_with_array_brackets_only() {
        let tokens = tokenize_with_seperator(&String::from("a.b.c.[]"), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::ArrayAccessWithoutIndex { .. }));
    }

    #[test]
    fn test_tokenize_identifiers_in_array_brackets() {
        let tokens = tokenize_with_seperator(&String::from("[a]"), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::ArrayAccessWithoutIndex { .. }));
    }

    #[test]
    fn test_tokenize_single_token_query() {
        let tokens = tokenize_with_seperator(&String::from("example"), '.');
        assert!(tokens.is_ok());
        let tokens = tokens.unwrap();

        assert!(match tokens {
            Token::Identifier {
                ref ident,
                next: None,
            } => {
                assert_eq!("example", ident);
                true
            }
            _ => false,
        });
    }

    #[test]
    fn test_tokenize_double_token_query() {
        let tokens = tokenize_with_seperator(&String::from("a.b"), '.');
        assert!(tokens.is_ok());
        let tokens = tokens.unwrap();

        assert!(match tokens {
            Token::Identifier {
                next: Some(ref next),
                ..
            } => {
                assert_eq!("b", next.deref().identifier());
                match next.deref() {
                    Token::Identifier { next: None, .. } => true,
                    _ => false,
                }
            }
            _ => false,
        });
        assert_eq!("a", tokens.identifier());
    }

    #[test]
    fn test_tokenize_ident_then_array_query() {
        let tokens = tokenize_with_seperator(&String::from("a.[0]"), '.');
        assert!(tokens.is_ok());
        let tokens = tokens.unwrap();

        assert_eq!("a", tokens.identifier());
        assert!(match tokens {
            Token::Identifier {
                next: Some(ref next),
                ..
            } => match next.deref() {
                Token::Index { idx: 0, next: None } => true,
                _ => false,
            },
            _ => false,
        });
    }

    #[test]
    fn test_tokenize_many_idents_then_array_query() {
        let tokens = tokenize_with_seperator(&String::from("a.b.c.[1000]"), '.');
        assert!(tokens.is_ok());
        let tokens = tokens.unwrap();

        assert_eq!("a", tokens.identifier());

        let expected = Token::Identifier {
            ident: String::from("a"),
            next: Some(Box::new(Token::Identifier {
                ident: String::from("b"),
                next: Some(Box::new(Token::Identifier {
                    ident: String::from("c"),
                    next: Some(Box::new(Token::Index {
                        idx: 1000,
                        next: None,
                    })),
                })),
            })),
        };

        assert_eq!(expected, tokens);
    }

    #[test]
    fn test_tokenize_empty_token_after_good_token() {
        let tokens = tokenize_with_seperator(&String::from("a..b"), '.');
        assert!(tokens.is_err());
        let tokens = tokens.unwrap_err();

        assert!(is_match!(tokens, Error::EmptyIdentifier { .. }));
    }

    quickcheck! {
        fn test_array_index(i: usize) -> bool {
            match tokenize_with_seperator(&format!("[{}]", i), '.') {
                Ok(Token::Index { next: None, ..  }) => true,
                _                                    => false,
            }
        }
    }

    #[test]
    fn test_pop_last_token_from_single_identifier_token_is_none() {
        let mut token = Token::Identifier {
            ident: String::from("something"),
            next: None,
        };

        let last = token.pop_last();
        assert!(last.is_none());
    }

    #[test]
    fn test_pop_last_token_from_single_index_token_is_none() {
        let mut token = Token::Index { idx: 0, next: None };

        let last = token.pop_last();
        assert!(last.is_none());
    }

    #[test]
    fn test_pop_last_token_from_single_identifier_token_is_one() {
        let mut token = Token::Identifier {
            ident: String::from("some"),
            next: Some(Box::new(Token::Identifier {
                ident: String::from("thing"),
                next: None,
            })),
        };

        let last = token.pop_last();

        assert!(last.is_some());
        let last = last.unwrap();

        assert!(is_match!(*last, Token::Identifier { .. }));
        match *last {
            Token::Identifier { ident, .. } => {
                assert_eq!("thing", ident);
            }
            _ => panic!("What just happened?"),
        }
    }

    #[test]
    fn test_pop_last_token_from_single_index_token_is_one() {
        let mut token = Token::Index {
            idx: 0,
            next: Some(Box::new(Token::Index { idx: 1, next: None })),
        };

        let last = token.pop_last();

        assert!(last.is_some());
        let last = last.unwrap();

        assert!(is_match!(*last, Token::Index { idx: 1, .. }));
    }

    #[test]
    fn test_pop_last_token_from_identifier_chain() {
        let tokens = tokenize_with_seperator(&String::from("a.b.c.d.e.f"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!("f", last.unwrap().identifier());
    }

    #[test]
    fn test_pop_last_token_from_mixed_chain() {
        let tokens = tokenize_with_seperator(&String::from("a.[100].c.[3].e.f"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!("f", last.unwrap().identifier());
    }

    #[test]
    fn test_pop_last_token_from_identifier_chain_is_array() {
        let tokens = tokenize_with_seperator(&String::from("a.b.c.d.e.f.[1000]"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!(1000, last.unwrap().idx());
    }

    #[test]
    fn test_pop_last_token_from_mixed_chain_is_array() {
        let tokens = tokenize_with_seperator(&String::from("a.[100].c.[3].e.f.[1000]"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!(1000, last.unwrap().idx());
    }

    #[test]
    fn test_pop_last_token_from_one_token() {
        let tokens = tokenize_with_seperator(&String::from("a"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_none());
    }

    #[test]
    fn test_pop_last_chain() {
        let tokens = tokenize_with_seperator(&String::from("a.[100].c.[3].e.f.[1000]"), '.');
        assert!(tokens.is_ok());
        let mut tokens = tokens.unwrap();

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!(1000, last.unwrap().idx());

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!("f", last.unwrap().identifier());

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!("e", last.unwrap().identifier());

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!(3, last.unwrap().idx());

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!("c", last.unwrap().identifier());

        let last = tokens.pop_last();
        assert!(last.is_some());
        assert_eq!(100, last.unwrap().idx());

        let last = tokens.pop_last();
        assert!(last.is_none());
    }
}