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// Copyright (C) 2023 Benjamin Stürz
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
use std::fmt::Write;
use crate::*;

fn escape(s: &str) -> String {
    s.chars().fold(String::new(), |mut s, ch| match ch {
        '<'     => s + "&lt;",
        '>'     => s + "&gt;",
        '&'     => s + "&amp;",
        '\''    => s + "&apos;",
        '"'     => s + "&quot;",
        _       => { write!(&mut s, "{ch}").unwrap(); s },
    })
}

impl ToXml for Xml {
    fn to_xml(&self) -> Xml {
        self.clone()
    }
}

impl ToXml for Tag {
    fn to_xml(&self) -> Xml {
        Xml(vec![Content::Tag(self.clone())])
    }
}

impl ToXml for &str {
    fn to_xml(&self) -> Xml {
        Xml(vec![Content::Word(escape(self))])
    }
}

impl ToXml for String {
    fn to_xml(&self) -> Xml {
        self.as_str().to_xml()
    }
}

impl ToXml for char {
    fn to_xml(&self) -> Xml {
        Xml(vec![Content::Word(escape(&self.to_string()))])
    }
}

impl<T: ToXml> ToXml for Vec<T> {
    fn to_xml(&self) -> Xml {
        let contents = self.iter()
            .map(|x| x.to_xml())
            .map(|mut x| {
                if x.0.len() == 1 {
                    x.0.drain(0..1).next().unwrap()
                } else {
                    Content::Nested(x)
                }
            })
            .collect();
        Xml(contents)
    }
}

impl<T: ToXml> ToXml for Option<T> {
    fn to_xml(&self) -> Xml {
        match self {
            Some(x) => x.to_xml(),
            None    => Xml::default(),
        }
    }
}

impl<T: ToXml, E: ToXml> ToXml for Result<T, E> {
    fn to_xml(&self) -> Xml {
        match self {
            Ok(x)   => x.to_xml(),
            Err(x)  => x.to_xml(),
        }
    }
}

impl<T: ToXml> ToXml for &T {
    fn to_xml(&self) -> Xml {
        (*self).to_xml()
    }
}

macro_rules! simple_impl {
    ($t:ty) => {
        impl ToXml for $t {
            fn to_xml(&self) -> Xml {
                Xml(vec![Content::Word(self.to_string())])
            }
        }
    };
}

// Implement ToXml for types that produce a single word, for which escaping is not needed.
simple_impl!(u8);
simple_impl!(u16);
simple_impl!(u32);
simple_impl!(u64);
simple_impl!(u128);
simple_impl!(usize);
simple_impl!(i8);
simple_impl!(i16);
simple_impl!(i32);
simple_impl!(i64);
simple_impl!(i128);
simple_impl!(isize);
simple_impl!(bool);


impl<T, I> CollectXml for I
where
    T: ToXml,
    I: Iterator<Item = T>,
{
    fn collect_xml(self) -> Xml {
        let inner = self.map(|x| x.to_xml().0).flatten().collect();
        Xml(inner)
    }
}