use std::collections::BTreeMap;

use component::Component;
use property::Property;
use error::*;

pub struct Parser<'s> {
    pub input: &'s str,
    pub pos: usize,
}

impl<'s> Parser<'s> {
    pub fn new(input: &'s str) -> Self {
        Parser {
            input: input,
            pos: 0,
        }
    }

    /// look-ahead for next char at given offset from current position
    /// (self.pos), taking [line unfolding]
    /// (https://tools.ietf.org/html/rfc5545#section-3.1) into account,
    /// without actually
    /// consuming it (immutable self).
    ///
    /// Return an option for next char, and needed increment to consume it
    /// from current position.
    /// CR characters get always skipped, resulting in CRLF to be simplified as
    /// LF, which seems to be acceptable because
    /// - the remainders of the lib do accept a lone LF as a line termination
    ///   (a bit laxer than RFC 5545)
    /// - CR alone [is not acceptable content]
    ///   (https://tools.ietf.org/html/rfc5545#section-3.1)
    fn peek_at(&self, at: usize) -> Option<(char, usize)> {
        match self.input[self.pos+at..].chars().next() {
            None => None,
            Some('\r') => self.peek_at(at + 1),
            Some('\n') => {
                match self.peek_at(at + 1) {
                    Some((' ', offset)) |
                    Some(('\t', offset)) => self.peek_at(offset),
                    _ => Some(('\n', at + 1)),
                }
            }
            Some(x) => Some((x, at + x.len_utf8()))
        }
    }

    #[inline]
    fn peek(&self) -> Option<(char, usize)> {
        self.peek_at(0)
    }

    pub fn eof(&self) -> bool {
        self.pos >= self.input.len()
    }

    fn assert_char(&self, c: char) -> Result<()> {
        let real_c = match self.peek() {
            Some((x, _)) => x,
            None => {
                return Err(VObjectErrorKind::ParserError(format!("Expected {}, found EOL", c)))
           }
        };

        if real_c != c {
            return Err(VObjectErrorKind::ParserError(format!("Expected {}, found {}", c, real_c)))
        };

        Ok(())
    }

    pub fn consume_char(&mut self) -> Option<char> {
        match self.peek() {
            Some((c, offset)) => { self.pos += offset; Some(c) },
            None => None
        }
    }

    /// If next peeked char is the given `c`, consume it and return `true`,
    /// otherwise return `false`.
    pub fn consume_only_char(&mut self, c: char) -> bool {
        match self.peek() {
            Some((d, offset)) if d == c => { self.pos += offset; true },
            _ => false
        }
    }

    fn consume_eol(&mut self) -> Result<()> {
        let start_pos = self.pos;

        let consumed = match self.consume_char() {
            Some('\n') => true,
            Some('\r') => match self.consume_char() {
                Some('\n') => true,
                _ => false,
            },
            _ => false,
        };

        if consumed {
            Ok(())
        } else {
            self.pos = start_pos;
            return Err(VObjectErrorKind::ParserError("Expected EOL.".to_owned()))
        }
    }

    fn sloppy_terminate_line(&mut self) -> Result<()> {
        if !self.eof() {
            try!(self.consume_eol());
            while let Ok(_) = self.consume_eol() {}
        };

        Ok(())
    }

    // GR this used to return just a slice from input, but line unfolding
    // makes it contradictory, unless one'd want to rescan everything.
    // Since actually useful calls used to_owned() on the result, which
    // does copy into a String's buffer, let's create a String right away
    // implementation detail : instead of pushing char after char, we
    // do it by the biggest contiguous slices possible, because I believe it
    // to be more efficient (less checks for reallocation etc).
    pub fn consume_while<F: Fn(char) -> bool>(&mut self, test: F) -> String {
        let mut sl_start_pos = self.pos;
        let mut res = String::new();
        while !self.eof() {
            match self.peek() {
                Some((c, offset)) => {
                    if !test(c) {
                        break
                    } else {
                        if offset > c.len_utf8() {
                            // we have some skipping and therefore need to flush
                            res.push_str(&self.input[sl_start_pos..self.pos]);
                            res.push(c);
                            sl_start_pos = self.pos + offset;
                        }
                        self.pos += offset;
                    }
                },
                _ => break
            }
        }
        // Final flush
        if sl_start_pos < self.pos {
            res.push_str(&self.input[sl_start_pos..self.pos])
        }
        res
    }

    pub fn consume_property(&mut self) -> Result<Property> {
        let group = self.consume_property_group().ok();
        let name = try!(self.consume_property_name());
        let params = self.consume_params();

        try!(self.assert_char(':'));
        self.consume_char();

        let value = try!(self.consume_property_value());

        Ok(Property {
            name: name,
            params: params,
            raw_value: value,
            prop_group: group,
        })
    }

    fn consume_property_name(&mut self) -> Result<String> {
        let rv = self.consume_while(|x| x == '-' || x.is_alphanumeric());
        if rv.is_empty() {
            Err(VObjectErrorKind::ParserError("No property name found.".to_owned()))
        } else {
            Ok(rv)
        }
    }

    fn consume_property_group(&mut self) -> Result<String> {
        let start_pos = self.pos;
        let name = self.consume_property_name();

        let e = match name {
            Ok(name) => match self.assert_char('.') {
                Ok(_) => {
                    self.consume_char();
                    return Ok(name);
                },
                Err(e) => Err(e),
            },
            Err(e) => Err(e),
        };

        self.pos = start_pos;
        e
    }

    fn consume_property_value(&mut self) -> Result<String> {
        let rv = self.consume_while(|x| x != '\r' && x != '\n');
        try!(self.sloppy_terminate_line());
        Ok(rv)
    }

    fn consume_param_name(&mut self) -> Result<String> {
        self.consume_property_name()
            .map_err(|e| VObjectErrorKind::ParserError(format!("No param name found: {}", e)))
    }

    fn consume_param_value(&mut self) -> Result<String> {
        let qsafe = |x| {
            x != '"' &&
            x != '\r' &&
            x != '\n' &&
            x != '\u{7F}' &&
            x > '\u{1F}'
        };

        if self.consume_only_char('"') {
            let rv = self.consume_while(qsafe);
            try!(self.assert_char('"'));
            self.consume_char();
            Ok(rv)
        } else {
            Ok(self.consume_while(|x| qsafe(x) && x != ';' && x != ':'))
        }
    }

    fn consume_param(&mut self) -> Result<(String, String)> {
        let name = try!(self.consume_param_name());
        let start_pos = self.pos;
        let value = if self.consume_only_char('=') {
            match self.consume_param_value() {
                Ok(x) => x,
                Err(e) => { self.pos = start_pos; return Err(e); }
            }
        } else {
            String::new()
        };

        Ok((name, value))
    }

    fn consume_params(&mut self) -> BTreeMap<String, String> {
        let mut rv: BTreeMap<String, String> = BTreeMap::new();
        while self.consume_only_char(';') {
            match self.consume_param() {
                Ok((name, value)) => { rv.insert(name.to_owned(), value.to_owned()); },
                Err(_) => break,
            }
        }
        rv
    }

    pub fn consume_component(&mut self) -> Result<Component> {
        let start_pos = self.pos;
        let mut property = try!(self.consume_property());
        if property.name != "BEGIN" {
            self.pos = start_pos;
            return Err(VObjectErrorKind::ParserError("Expected BEGIN tag.".to_owned()));
        };

        // Create a component with the name of the BEGIN tag's value
        let mut component = Component::new(property.raw_value);

        loop {
            let previous_pos = self.pos;
            property = try!(self.consume_property());
            if property.name == "BEGIN" {
                self.pos = previous_pos;
                component.subcomponents.push(try!(self.consume_component()));
            } else if property.name == "END" {
                if property.raw_value != component.name {
                    self.pos = start_pos;
                    let s = format!("Mismatched tags: BEGIN:{} vs END:{}",
                                    component.name,
                                    property.raw_value);
                    return Err(VObjectErrorKind::ParserError(s));
                }

                break;
            } else {
                component.push(property);
            }
        }

        Ok(component)
    }
}

#[cfg(test)]
mod tests {
    use error::*;
    use super::Parser;

    #[test]
    fn test_unfold1() {
        let mut p = Parser{input: "ab\r\n c", pos: 2};
        assert_eq!(p.consume_char(), Some('c'));
        assert_eq!(p.pos, 6);
    }

    #[test]
    fn test_unfold2() {
        let mut p = Parser{input: "ab\n\tc\nx", pos: 2};
        assert_eq!(p.consume_char(), Some('c'));
        assert_eq!(p.consume_char(), Some('\n'));
        assert_eq!(p.consume_char(), Some('x'));
    }

    #[test]
    fn test_consume_while() {
        let mut p = Parser{input:"af\n oo:bar", pos: 1};
        assert_eq!(p.consume_while(|x| x != ':'), "foo");
        assert_eq!(p.consume_char(), Some(':'));
        assert_eq!(p.consume_while(|x| x != '\n'), "bar");
    }

    #[test]
    fn test_consume_while2() {
        let mut p = Parser{input:"af\n oo\n\t:bar", pos: 1};
        assert_eq!(p.consume_while(|x| x != ':'), "foo");
        assert_eq!(p.consume_char(), Some(':'));
        assert_eq!(p.consume_while(|x| x != '\n'), "bar");
    }

    #[test]
    fn test_consume_while3() {
        let mut p = Parser{input:"af\n oo:\n bar", pos: 1};
        assert_eq!(p.consume_while(|x| x != ':'), "foo");
        assert_eq!(p.consume_char(), Some(':'));
        assert_eq!(p.consume_while(|x| x != '\n'), "bar");
    }

    #[test]
    fn test_consume_only_char() {
        let mut p = Parser{input:"\n \"bar", pos: 0};
        assert!(p.consume_only_char('"'));
        assert_eq!(p.pos, 3);
        assert!(!p.consume_only_char('"'));
        assert_eq!(p.pos, 3);
        assert!(p.consume_only_char('b'));
        assert_eq!(p.pos, 4);
    }

    #[test]
    fn mismatched_begin_end_tags_returns_error() {
        // Test for infinite loops as well
        use std::sync::mpsc::{channel, RecvTimeoutError};
        use std::time::Duration;
        use error::VObjectErrorKind;
        let mut p = Parser {input: "BEGIN:a\nBEGIN:b\nEND:a", pos: 0};

        let (tx, rx) = channel();
        ::std::thread::spawn(move|| { tx.send(p.consume_component()) });

        match rx.recv_timeout(Duration::from_millis(50)) {
            Err(RecvTimeoutError::Timeout) => assert!(false),
            Ok(Err(e)) => {
                match e {
                    VObjectErrorKind::ParserError { .. } => assert!(true),
                    _ => assert!(false),
                }
            },
            _ => assert!(false),
        }
    }

}