purr 0.9.0

Primitives for reading and writing the SMILES language in Rust.
Documentation 
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use crate::feature::{ AtomKind, BondKind, Rnum };
use crate::walk::Follower;

/// A `Follower` that builds a string SMILEs representation.
/// 
/// ```
/// use purr::walk::Follower;
/// use purr::write::Writer;
/// use purr::feature::{ AtomKind, BondKind };
/// 
/// fn main() {
///     let mut writer = Writer::new();
/// 
///     writer.root(AtomKind::Star);
///     writer.extend(BondKind::Double, AtomKind::Star);
/// 
///     assert_eq!(writer.write(), "*=*")
/// }
/// ```
#[derive(Debug,PartialEq)]
pub struct Writer {
    stack: Vec<String>
}

impl Writer {
    pub fn new() -> Self {
        Writer {
            stack: Vec::new()
        }
    }

    pub fn write(self) -> String {
        self.stack.join("")
    }
}

impl Follower for Writer {
    fn root(&mut self, root: AtomKind) {
        if self.stack.is_empty() {
            self.stack.push(root.to_string())
        } else {
            self.stack.push(".".to_string() + &root.to_string())
        }
    }

    fn extend(&mut self, bond_kind: BondKind, atom_kind: AtomKind) {
        self.stack.push(bond_kind.to_string() + &atom_kind.to_string())
    }

    fn join(&mut self, bond_kind: BondKind, rnum: Rnum) {
        let last = self.stack.last_mut().expect("last");

        last.push_str(&(bond_kind.to_string() + &rnum.to_string()))
    }

    fn pop(&mut self, depth: usize) {
        if depth >= self.stack.len() {
            panic!("overpop")
        }

        let chain = self.stack.split_off(self.stack.len() - depth);
        let last = self.stack.last_mut().expect("last");

        last.push_str(&("(".to_string() + &chain.join("") + ")"))
    }
}

#[cfg(test)]
mod write {
    use pretty_assertions::assert_eq;
    use crate::feature::Aliphatic;
    use super::*;

    #[test]
    fn p1() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);

        assert_eq!(writer.write(), "*")
    }

    #[test]
    fn p2() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.extend(BondKind::Single, AtomKind::Star);

        assert_eq!(writer.write(), "*-*")
    }

    #[test]
    fn p1_p1() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.root(AtomKind::Star);

        assert_eq!(writer.write(), "*.*")
    }

    #[test]
    fn p3() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.extend(BondKind::Single, AtomKind::Star);
        writer.extend(BondKind::Single, AtomKind::Star);

        assert_eq!(writer.write(), "*-*-*")
    }

    #[test]
    fn p3_branched() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.extend(BondKind::Elided, AtomKind::Aliphatic(Aliphatic::F));
        writer.pop(1);
        writer.extend(BondKind::Elided, AtomKind::Aliphatic(Aliphatic::Cl));

        assert_eq!(writer.write(), "*(F)Cl")
    }

    #[test]
    fn c3() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.join(BondKind::Single, Rnum::R1);
        writer.extend(BondKind::Single, AtomKind::Star);
        writer.extend(BondKind::Double, AtomKind::Star);
        writer.join(BondKind::Single, Rnum::R1);

        assert_eq!(writer.write(), "*-1-*=*-1")
    }

    #[test]
    fn c3_branched() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.extend(BondKind::Elided, AtomKind::Star);
        writer.extend(BondKind::Elided, AtomKind::Star);
        writer.join(BondKind::Elided, Rnum::R1);
        writer.pop(2);
        writer.join(BondKind::Elided, Rnum::R1);

        assert_eq!(writer.write(), "*(**1)1")
    }

    #[test]
    fn nested_branch() {
        let mut writer = Writer::new();

        writer.root(AtomKind::Star);
        writer.extend(BondKind::Elided, AtomKind::Star);
        writer.extend(BondKind::Single, AtomKind::Star);
        writer.pop(1);
        writer.extend(BondKind::Elided, AtomKind::Star);
        writer.pop(2);
        writer.extend(BondKind::Double, AtomKind::Star);

        assert_eq!(writer.write(), "*(*(-*)*)=*")
    }
}