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use log::{error, warn};
use bgp_models::mrt::MrtRecord;
use std::io::Read;
use crate::{BgpElem, Elementor};
use crate::error::ParserError;
use crate::parser::BgpkitParser;

/// Use [BgpElemIterator] as the default iterator to return [BgpElem]s instead of [MrtRecord]s.
impl<T: Read> IntoIterator for BgpkitParser<T> {
    type Item = BgpElem;
    type IntoIter = ElemIterator<T>;

    fn into_iter(self) -> Self::IntoIter {
        ElemIterator::new(self)
    }
}

impl<T: Read> BgpkitParser<T> {
    pub fn into_record_iter(self) -> RecordIterator<T> {
        RecordIterator::new(self)
    }
    pub fn into_elem_iter(self) -> ElemIterator<T> {
        ElemIterator::new(self)
    }
}

/*********
MrtRecord Iterator
**********/

pub struct RecordIterator<T: Read> {
    parser: BgpkitParser<T>,
    count: u64,
}

impl<T: Read> RecordIterator<T> {
    fn new(parser: BgpkitParser<T>) -> RecordIterator<T> {
        RecordIterator { parser , count: 0 }
    }
}

impl<T: Read> Iterator for RecordIterator<T> {
    type Item = MrtRecord;

    fn next(&mut self) -> Option<MrtRecord> {
        self.count += 1;
        match self.parser.next() {
            Ok(v) => {
                // if None, the reaches EoF.
                Some(v)
            },
            Err(e) => {
                match e {
                    ParserError::TruncatedMsg(_)| ParserError::Unsupported(_)
                    |ParserError::UnknownAttr(_) | ParserError::Deprecated(_) => {
                        self.next()
                    }
                    ParserError::ParseError(e) => {
                        warn!("Parsing error: {}", e);
                        self.next()
                    }
                    ParserError::EofExpected =>{
                        // normal end of file
                        None
                    }
                    ParserError::IoError(e, _bytes)| ParserError::EofError(e, _bytes) => {
                        // when reaching IO error, stop iterating
                        error!("{}", e.to_string());
                        None
                    }
                }
            },
        }
    }
}

/*********
BgpElem Iterator
**********/

pub struct ElemIterator<T: Read> {
    cache_elems: Vec<BgpElem>,
    record_iter: RecordIterator<T>,
    elementor: Elementor,
    count: u64,
}

impl<T: Read> ElemIterator<T> {
    fn new(parser: BgpkitParser<T>) -> ElemIterator<T> {
        ElemIterator { record_iter: RecordIterator::new(parser) , count: 0 , cache_elems: vec![], elementor: Elementor::new()}
    }
}

impl<T: Read> Iterator for ElemIterator<T> {
    type Item = BgpElem;

    fn next(&mut self) -> Option<BgpElem> {
        self.count += 1;

        if self.cache_elems.is_empty() {
            // refill cache elems
            loop {
                match self.record_iter.next() {
                    None => {
                        // no more records
                        return None
                    }
                    Some(r) => {
                        let mut elems =  self.elementor.record_to_elems(r);
                        if elems.len()>0 {
                            elems.reverse();
                            self.cache_elems = elems;
                            break
                        } else {
                            // somehow this record does not contain any elems, continue to parse next record
                            continue
                        }
                    }
                }
            }
            // when reaching here, the `self.cache_elems` has been refilled with some more elems
        }

        // poping cached elems. note that the original elems order is preseved by reversing the
        // vector before putting it on to cache_elems.
        match self.cache_elems.pop() {
            None => {None}
            Some(i) => {Some(i) }
        }
    }
}