nettext/src/enc/mod.rs

//! Functions to generate nettext representations of data structures

use std::collections::HashMap;

use crate::dec::decode;
use crate::{is_string_char, is_whitespace};

pub struct Term<'a>(T<'a>);

enum T<'a> {
    Str(&'a [u8]),
    OwnedStr(Vec<u8>),
    Dict(HashMap<&'a [u8], T<'a>>),
    List(Vec<T<'a>>),
}

#[derive(Debug)]
pub enum Error {
    InvalidCharacter(u8),
    InvalidRaw,
    NotADictionnary,
}

// ---- helpers to build terms ----

/// Encode a string (may contain whitespace)
///
/// ```
/// use nettext::enc::*;
///
/// assert_eq!(encode(&string("Hello world  .").unwrap()), b"Hello world  .");
/// ```
pub fn string(s: &str) -> Result<Term<'_>, Error> {
    for c in s.as_bytes().iter() {
        if !(is_string_char(*c) || is_whitespace(*c)) {
            return Err(Error::InvalidCharacter(*c));
        }
    }
    Ok(Term(T::Str(s.as_bytes())))
}

/// Include a raw nettext value
///
/// ```
/// use nettext::enc::*;
///
/// assert_eq!(encode(&raw(b"Hello { a = b, c = d}  .").unwrap()), b"Hello { a = b, c = d}  .");
/// ```
pub fn raw(bytes: &[u8]) -> Result<Term<'_>, Error> {
    if decode(bytes).is_err() {
        return Err(Error::InvalidRaw);
    }
    Ok(Term(T::Str(bytes)))
}

/// Encode a list of items
///
/// ```
/// use nettext::enc::*;
///
/// assert_eq!(encode(&list([
///		string("Hello").unwrap(),
///		string("world").unwrap()
///		])), b"Hello world");
/// ```
pub fn list<'a, I: IntoIterator<Item = Term<'a>>>(terms: I) -> Term<'a> {
    Term(T::List(terms.into_iter().map(|x| x.0).collect()))
}

/// Encode a list of items
///
/// ```
/// use nettext::enc::*;
///
/// assert_eq!(encode(&dict([
///		("a", string("Hello").unwrap()),
///		("b", string("world").unwrap())
///		])), b"{\n  a = Hello,\n  b = world,\n}");
/// ```
pub fn dict<'a, I: IntoIterator<Item = (&'a str, Term<'a>)>>(pairs: I) -> Term<'a> {
    Term(T::Dict(
        pairs
            .into_iter()
            .map(|(k, v)| (k.as_bytes(), v.0))
            .collect(),
    ))
}

impl<'a> Term<'a> {
    pub fn push(self, t: Term<'a>) -> Term<'a> {
        match self.0 {
            T::List(mut v) => {
                v.push(t.0);
                Term(T::List(v))
            }
            x => Term(T::List(vec![x, t.0])),
        }
    }

    pub fn insert(self, k: &'a str, v: Term<'a>) -> Result<Term<'a>, Error> {
        match self.0 {
            T::Dict(mut d) => {
                d.insert(k.as_bytes(), v.0);
                Ok(Term(T::Dict(d)))
            }
            _ => Err(Error::NotADictionnary),
        }
    }
}

// ---- encoding function ----

pub fn encode<'a>(t: &Term<'a>) -> Vec<u8> {
    let mut buf = Vec::with_capacity(128);
    encode_aux(&mut buf, &t.0, 0);
    buf
}

fn encode_aux<'a>(buf: &mut Vec<u8>, term: &T<'a>, indent: usize) {
    match term {
        T::Str(s) => buf.extend_from_slice(s),
        T::OwnedStr(s) => buf.extend_from_slice(&s),
        T::Dict(d) => {
            buf.extend_from_slice(b"{\n");
            let indent2 = indent + 2;
            let mut keys = d.keys().collect::<Vec<_>>();
            keys.sort();
            for k in keys {
                let v = d.get(k).unwrap();
                for _ in 0..indent2 {
                    buf.push(b' ');
                }
                buf.extend_from_slice(k);
                buf.extend_from_slice(b" = ");
                encode_aux(buf, v, indent2);
                buf.extend_from_slice(b",\n");
            }
            for _ in 0..indent {
                buf.push(b' ');
            }
            buf.push(b'}');
        }
        T::List(l) => {
            let indent2 = indent + 2;
            for (i, v) in l.iter().enumerate() {
                if buf.iter().rev().take_while(|c| **c != b'\n').count() > 80 {
                    buf.push(b'\n');
                    for _ in 0..indent2 {
                        buf.push(b' ');
                    }
                } else if i > 0 {
                    buf.push(b' ');
                }
                encode_aux(buf, v, indent2);
            }
        }
    }
}

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

    #[test]
    fn complex1() {
        let input = list([
            string("HELLO").unwrap(),
            string("alexhelloworld").unwrap(),
            dict([
                ("from", string("jxx").unwrap()),
                ("subject", string("hello").unwrap()),
                ("data", raw(b"{ f1 = plop, f2 = kuko }").unwrap()),
            ]),
        ]);
        let expected = b"HELLO alexhelloworld {
    data = { f1 = plop, f2 = kuko },
    from = jxx,
    subject = hello,
  }";
        let enc = encode(&input);
        eprintln!("{}", std::str::from_utf8(&enc).unwrap());
        eprintln!("{}", std::str::from_utf8(&expected[..]).unwrap());
        assert_eq!(encode(&input), expected);
    }
}