//! Defines zero-copy XML events used throughout this library.

pub mod attributes;

#[cfg(feature = "encoding_rs")]
use encoding_rs::Encoding;
use std::borrow::Cow;
use std::io::BufRead;
use std::ops::Deref;
use std::str::from_utf8;

use self::attributes::{Attribute, Attributes};
use errors::{Error, Result};
use escape::{escape, unescape};
use reader::Reader;

use memchr;

/// Opening tag data (`Event::Start`), with optional attributes.
///
/// `<name attr="value">`.
///
/// The name can be accessed using the [`name`], [`local_name`] or [`unescaped`] methods. An
/// iterator over the attributes is returned by the [`attributes`] method.
///
/// [`name`]: #method.name
/// [`local_name`]: #method.local_name
/// [`unescaped`]: #method.unescaped
/// [`attributes`]: #method.attributes
#[derive(Clone)]
pub struct BytesStart<'a> {
    /// content of the element, before any utf8 conversion
    buf: Cow<'a, [u8]>,
    /// end of the element name, the name starts at that the start of `buf`
    name_len: usize,
}

impl<'a> BytesStart<'a> {
    /// Creates a new `BytesStart` from the given content (name + attributes).
    ///
    /// # Warning
    ///
    /// `&content[..name_len]` is not checked to be a valid name
    #[inline]
    pub fn borrowed(content: &'a [u8], name_len: usize) -> Self {
        BytesStart {
            buf: Cow::Borrowed(content),
            name_len: name_len,
        }
    }

    /// Creates a new `BytesStart` from the given name.
    ///
    /// # Warning
    ///
    /// `&content` is not checked to be a valid name
    #[inline]
    pub fn borrowed_name(name: &'a [u8]) -> BytesStart<'a> {
        Self::borrowed(name, name.len())
    }

    /// Creates a new `BytesStart` from the given content (name + attributes)
    ///
    /// Owns its contents.
    #[inline]
    pub fn owned<C: Into<Vec<u8>>>(content: C, name_len: usize) -> BytesStart<'static> {
        BytesStart {
            buf: Cow::Owned(content.into()),
            name_len: name_len,
        }
    }

    /// Creates a new `BytesStart` from the given name
    ///
    /// Owns its contents.
    #[inline]
    pub fn owned_name<C: Into<Vec<u8>>>(name: C) -> BytesStart<'static> {
        let content = name.into();
        BytesStart {
            name_len: content.len(),
            buf: Cow::Owned(content),
        }
    }

    /// Converts the event into an owned event.
    pub fn into_owned(self) -> BytesStart<'static> {
        Self::owned(self.buf.into_owned(), self.name_len)
    }

    /// Converts the event into an owned event without taking ownership of Event
    pub fn to_owned(&self) -> BytesStart<'static> {
        Self::owned(self.buf.to_owned(), self.name_len)
    }

    /// Consumes `self` and yield a new `BytesStart` with additional attributes from an iterator.
    ///
    /// The yielded items must be convertible to [`Attribute`] using `Into`.
    ///
    /// [`Attribute`]: attributes/struct.Attributes.html
    pub fn with_attributes<'b, I>(mut self, attributes: I) -> Self
    where
        I: IntoIterator,
        I::Item: Into<Attribute<'b>>,
    {
        self.extend_attributes(attributes);
        self
    }

    /// Gets the undecoded raw tag name as a `&[u8]`.
    #[inline]
    pub fn name(&self) -> &[u8] {
        &self.buf[..self.name_len]
    }

    /// Gets the undecoded raw local tag name (excluding namespace) as a `&[u8]`.
    ///
    /// All content up to and including the first `:` character is removed from the tag name.
    #[inline]
    pub fn local_name(&self) -> &[u8] {
        let name = self.name();
        memchr::memchr(b':', name).map_or(name, |i| &name[i + 1..])
    }

    /// Gets the unescaped tag name.
    ///
    /// XML escape sequences like "`&lt;`" will be replaced by their unescaped characters like
    /// "`<`".
    #[inline]
    pub fn unescaped(&self) -> Result<Cow<[u8]>> {
        unescape(&*self.buf).map_err(Error::EscapeError)
    }

    /// Returns an iterator over the attributes of this tag.
    pub fn attributes(&self) -> Attributes {
        Attributes::new(self, self.name_len)
    }

    /// Returns an iterator over the HTML-like attributes of this tag (no mandatory quotes or `=`).
    pub fn html_attributes(&self) -> Attributes {
        Attributes::html(self, self.name_len)
    }

    /// Gets the undecoded raw string with the attributes of this tag as a `&[u8]`,
    /// including the whitespace after the tag name if there is any.
    #[inline]
    pub fn attributes_raw(&self) -> &[u8] {
        &self.buf[self.name_len..]
    }

    /// Add additional attributes to this tag using an iterator.
    ///
    /// The yielded items must be convertible to [`Attribute`] using `Into`.
    ///
    /// [`Attribute`]: attributes/struct.Attributes.html
    pub fn extend_attributes<'b, I>(&mut self, attributes: I) -> &mut BytesStart<'a>
    where
        I: IntoIterator,
        I::Item: Into<Attribute<'b>>,
    {
        for attr in attributes {
            self.push_attribute(attr);
        }
        self
    }

    /// Returns the unescaped and decoded string value.
    ///
    /// This allocates a `String` in all cases. For performance reasons it might be a better idea to
    /// instead use one of:
    ///
    /// * [`unescaped()`], as it doesn't allocate when no escape sequences are used.
    /// * [`Reader::decode()`], as it only allocates when the decoding can't be performed otherwise.
    ///
    /// [`unescaped()`]: #method.unescaped
    /// [`Reader::decode()`]: ../reader/struct.Reader.html#method.decode
    #[cfg(feature = "encoding")]
    #[inline]
    pub fn unescape_and_decode<B: BufRead>(&self, reader: &Reader<B>) -> Result<String> {
        let decoded = reader.decode(&*self);
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// Returns the unescaped and decoded string value.
    ///
    /// This allocates a `String` in all cases. For performance reasons it might be a better idea to
    /// instead use one of:
    ///
    /// * [`unescaped()`], as it doesn't allocate when no escape sequences are used.
    /// * [`Reader::decode()`], as it only allocates when the decoding can't be performed otherwise.
    ///
    /// [`unescaped()`]: #method.unescaped
    /// [`Reader::decode()`]: ../reader/struct.Reader.html#method.decode
    #[cfg(not(feature = "encoding"))]
    #[inline]
    pub fn unescape_and_decode<B: BufRead>(&self, reader: &Reader<B>) -> Result<String> {
        let decoded = reader.decode(&*self)?;
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// Adds an attribute to this element.
    pub fn push_attribute<'b, A: Into<Attribute<'b>>>(&mut self, attr: A) {
        let a = attr.into();
        let bytes = self.buf.to_mut();
        bytes.push(b' ');
        bytes.extend_from_slice(a.key);
        bytes.extend_from_slice(b"=\"");
        bytes.extend_from_slice(&*a.value);
        bytes.push(b'"');
    }

    /// Edit the name of the BytesStart in-place
    ///
    /// # Warning
    ///
    /// `name` is not checked to be a valid name
    pub fn set_name(&mut self, name: &[u8]) -> &mut BytesStart<'a> {
        let bytes = self.buf.to_mut();
        bytes.splice(..self.name_len, name.iter().cloned());
        self.name_len = name.len();
        self
    }

    /// Remove all attributes from the ByteStart
    pub fn clear_attributes(&mut self) -> &mut BytesStart<'a> {
        self.buf.to_mut().truncate(self.name_len);
        self
    }
}

impl<'a> std::fmt::Debug for BytesStart<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        use crate::utils::write_byte_string;

        write!(f, "BytesStart {{ buf: ")?;
        write_byte_string(f, &self.buf)?;
        write!(f, ", name_len: {} }}", self.name_len)
    }
}

/// An XML declaration (`Event::Decl`).
///
/// [W3C XML 1.1 Prolog and Document Type Declaration](http://w3.org/TR/xml11/#sec-prolog-dtd)
#[derive(Clone, Debug)]
pub struct BytesDecl<'a> {
    element: BytesStart<'a>,
}

impl<'a> BytesDecl<'a> {
    /// Creates a `BytesDecl` from a `BytesStart`
    pub fn from_start(start: BytesStart<'a>) -> BytesDecl<'a> {
        BytesDecl { element: start }
    }

    /// Gets xml version, including quotes (' or ")
    pub fn version(&self) -> Result<Cow<[u8]>> {
        // The version *must* be the first thing in the declaration.
        match self.element.attributes().next() {
            Some(Err(e)) => Err(e),
            Some(Ok(Attribute {
                key: b"version",
                value: v,
            })) => Ok(v),
            Some(Ok(a)) => {
                let found = from_utf8(a.key).map_err(Error::Utf8)?.to_string();
                Err(Error::XmlDeclWithoutVersion(Some(found)))
            }
            None => Err(Error::XmlDeclWithoutVersion(None)),
        }
    }

    /// Gets xml encoding, including quotes (' or ")
    pub fn encoding(&self) -> Option<Result<Cow<[u8]>>> {
        for a in self.element.attributes() {
            match a {
                Err(e) => return Some(Err(e)),
                Ok(Attribute {
                    key: b"encoding",
                    value: v,
                }) => return Some(Ok(v)),
                _ => (),
            }
        }
        None
    }

    /// Gets xml standalone, including quotes (' or ")
    pub fn standalone(&self) -> Option<Result<Cow<[u8]>>> {
        for a in self.element.attributes() {
            match a {
                Err(e) => return Some(Err(e)),
                Ok(Attribute {
                    key: b"standalone",
                    value: v,
                }) => return Some(Ok(v)),
                _ => (),
            }
        }
        None
    }

    /// Constructs a new `XmlDecl` from the (mandatory) _version_ (should be `1.0` or `1.1`),
    /// the optional _encoding_ (e.g., `UTF-8`) and the optional _standalone_ (`yes` or `no`)
    /// attribute.
    ///
    /// Does not escape any of its inputs. Always uses double quotes to wrap the attribute values.
    /// The caller is responsible for escaping attribute values. Shouldn't usually be relevant since
    /// the double quote character is not allowed in any of the attribute values.
    pub fn new(
        version: &[u8],
        encoding: Option<&[u8]>,
        standalone: Option<&[u8]>,
    ) -> BytesDecl<'static> {
        // Compute length of the buffer based on supplied attributes
        // ' encoding=""'   => 12
        let encoding_attr_len = if let Some(xs) = encoding {
            12 + xs.len()
        } else {
            0
        };
        // ' standalone=""' => 14
        let standalone_attr_len = if let Some(xs) = standalone {
            14 + xs.len()
        } else {
            0
        };
        // 'xml version=""' => 14
        let mut buf = Vec::with_capacity(14 + encoding_attr_len + standalone_attr_len);

        buf.extend_from_slice(b"xml version=\"");
        buf.extend_from_slice(version);

        if let Some(encoding_val) = encoding {
            buf.extend_from_slice(b"\" encoding=\"");
            buf.extend_from_slice(encoding_val);
        }

        if let Some(standalone_val) = standalone {
            buf.extend_from_slice(b"\" standalone=\"");
            buf.extend_from_slice(standalone_val);
        }
        buf.push(b'"');

        BytesDecl {
            element: BytesStart::owned(buf, 3),
        }
    }

    /// Gets the decoder struct
    #[cfg(feature = "encoding_rs")]
    pub fn encoder(&self) -> Option<&'static Encoding> {
        self.encoding()
            .and_then(|e| e.ok())
            .and_then(|e| Encoding::for_label(&*e))
    }

    /// Converts the event into an owned event.
    pub fn into_owned(self) -> BytesDecl<'static> {
        BytesDecl {
            element: self.element.into_owned(),
        }
    }
}

/// A struct to manage `Event::End` events
#[derive(Clone)]
pub struct BytesEnd<'a> {
    name: Cow<'a, [u8]>,
}

impl<'a> BytesEnd<'a> {
    /// Creates a new `BytesEnd` borrowing a slice
    #[inline]
    pub fn borrowed(name: &'a [u8]) -> BytesEnd<'a> {
        BytesEnd {
            name: Cow::Borrowed(name),
        }
    }

    /// Creates a new `BytesEnd` owning its name
    #[inline]
    pub fn owned(name: Vec<u8>) -> BytesEnd<'static> {
        BytesEnd {
            name: Cow::Owned(name),
        }
    }

    /// Converts the event into an owned event.
    pub fn into_owned(self) -> BytesEnd<'static> {
        BytesEnd {
            name: Cow::Owned(self.name.into_owned()),
        }
    }

    /// Gets `BytesEnd` event name
    #[inline]
    pub fn name(&self) -> &[u8] {
        &*self.name
    }

    /// local name (excluding namespace) as &[u8] (without eventual attributes)
    /// returns the name() with any leading namespace removed (all content up to
    /// and including the first ':' character)
    #[inline]
    pub fn local_name(&self) -> &[u8] {
        if let Some(i) = self.name().iter().position(|b| *b == b':') {
            &self.name()[i + 1..]
        } else {
            self.name()
        }
    }
}

impl<'a> std::fmt::Debug for BytesEnd<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        use crate::utils::write_byte_string;

        write!(f, "BytesEnd {{ name: ")?;
        write_byte_string(f, &self.name)?;
        write!(f, " }}")
    }
}

/// Data from various events (most notably, `Event::Text`).
#[derive(Clone)]
pub struct BytesText<'a> {
    // Invariant: The content is always escaped.
    content: Cow<'a, [u8]>,
}

impl<'a> BytesText<'a> {
    /// Creates a new `BytesText` from an escaped byte sequence.
    #[inline]
    pub fn from_escaped<C: Into<Cow<'a, [u8]>>>(content: C) -> BytesText<'a> {
        BytesText {
            content: content.into(),
        }
    }

    /// Creates a new `BytesText` from a byte sequence. The byte sequence is
    /// expected not to be escaped.
    #[inline]
    pub fn from_plain(content: &'a [u8]) -> BytesText<'a> {
        BytesText {
            content: escape(content),
        }
    }

    /// Creates a new `BytesText` from an escaped string.
    #[inline]
    pub fn from_escaped_str<C: Into<Cow<'a, str>>>(content: C) -> BytesText<'a> {
        Self::from_escaped(match content.into() {
            Cow::Owned(o) => Cow::Owned(o.into_bytes()),
            Cow::Borrowed(b) => Cow::Borrowed(b.as_bytes()),
        })
    }

    /// Creates a new `BytesText` from a string. The string is expected not to
    /// be escaped.
    #[inline]
    pub fn from_plain_str(content: &'a str) -> BytesText<'a> {
        Self::from_plain(content.as_bytes())
    }

    /// Ensures that all data is owned to extend the object's lifetime if
    /// necessary.
    #[inline]
    pub fn into_owned(self) -> BytesText<'static> {
        BytesText {
            content: self.content.into_owned().into(),
        }
    }

    /// gets escaped content
    ///
    /// Searches for '&' into content and try to escape the coded character if possible
    /// returns Malformed error with index within element if '&' is not followed by ';'
    pub fn unescaped(&self) -> Result<Cow<[u8]>> {
        unescape(self).map_err(Error::EscapeError)
    }

    /// helper method to unescape then decode self using the reader encoding
    /// but without BOM (Byte order mark)
    ///
    /// for performance reasons (could avoid allocating a `String`),
    /// it might be wiser to manually use
    /// 1. BytesText::unescaped()
    /// 2. Reader::decode(...)
    #[cfg(feature = "encoding")]
    pub fn unescape_and_decode_without_bom<B: BufRead>(
        &self,
        reader: &mut Reader<B>,
    ) -> Result<String> {
        let decoded = reader.decode_without_bom(&*self);
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// helper method to unescape then decode self using the reader encoding
    /// but without BOM (Byte order mark)
    ///
    /// for performance reasons (could avoid allocating a `String`),
    /// it might be wiser to manually use
    /// 1. BytesText::unescaped()
    /// 2. Reader::decode(...)
    #[cfg(not(feature = "encoding"))]
    pub fn unescape_and_decode_without_bom<B: BufRead>(
        &self,
        reader: &Reader<B>,
    ) -> Result<String> {
        let decoded = reader.decode_without_bom(&*self)?;
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// helper method to unescape then decode self using the reader encoding
    ///
    /// for performance reasons (could avoid allocating a `String`),
    /// it might be wiser to manually use
    /// 1. BytesText::unescaped()
    /// 2. Reader::decode(...)
    #[cfg(feature = "encoding")]
    pub fn unescape_and_decode<B: BufRead>(&self, reader: &Reader<B>) -> Result<String> {
        let decoded = reader.decode(&*self);
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// helper method to unescape then decode self using the reader encoding
    ///
    /// for performance reasons (could avoid allocating a `String`),
    /// it might be wiser to manually use
    /// 1. BytesText::unescaped()
    /// 2. Reader::decode(...)
    #[cfg(not(feature = "encoding"))]
    pub fn unescape_and_decode<B: BufRead>(&self, reader: &Reader<B>) -> Result<String> {
        let decoded = reader.decode(&*self)?;
        let unescaped = unescape(decoded.as_bytes()).map_err(Error::EscapeError)?;
        String::from_utf8(unescaped.into_owned()).map_err(|e| Error::Utf8(e.utf8_error()))
    }

    /// Gets escaped content.
    pub fn escaped(&self) -> &[u8] {
        self.content.as_ref()
    }
}

impl<'a> std::fmt::Debug for BytesText<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        use crate::utils::write_byte_string;

        write!(f, "BytesText {{ content: ")?;
        write_byte_string(f, &self.content)?;
        write!(f, " }}")
    }
}

/// Event emitted by [`Reader::read_event`].
///
/// [`Reader::read_event`]: ../reader/struct.Reader.html#method.read_event
#[derive(Clone, Debug)]
pub enum Event<'a> {
    /// Start tag (with attributes) `<tag attr="value">`.
    Start(BytesStart<'a>),
    /// End tag `</tag>`.
    End(BytesEnd<'a>),
    /// Empty element tag (with attributes) `<tag attr="value" />`.
    Empty(BytesStart<'a>),
    /// Character data between `Start` and `End` element.
    Text(BytesText<'a>),
    /// Comment `<!-- ... -->`.
    Comment(BytesText<'a>),
    /// CData `<![CDATA[...]]>`.
    CData(BytesText<'a>),
    /// XML declaration `<?xml ...?>`.
    Decl(BytesDecl<'a>),
    /// Processing instruction `<?...?>`.
    PI(BytesText<'a>),
    /// Doctype `<!DOCTYPE...>`.
    DocType(BytesText<'a>),
    /// End of XML document.
    Eof,
}

impl<'a> Event<'a> {
    /// Converts the event to an owned version, untied to the lifetime of
    /// buffer used when reading but incurring a new, seperate allocation.
    pub fn into_owned(self) -> Event<'static> {
        match self {
            Event::Start(e) => Event::Start(e.into_owned()),
            Event::End(e) => Event::End(e.into_owned()),
            Event::Empty(e) => Event::Empty(e.into_owned()),
            Event::Text(e) => Event::Text(e.into_owned()),
            Event::Comment(e) => Event::Comment(e.into_owned()),
            Event::CData(e) => Event::CData(e.into_owned()),
            Event::Decl(e) => Event::Decl(e.into_owned()),
            Event::PI(e) => Event::PI(e.into_owned()),
            Event::DocType(e) => Event::DocType(e.into_owned()),
            Event::Eof => Event::Eof,
        }
    }
}

impl<'a> Deref for BytesStart<'a> {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        &*self.buf
    }
}

impl<'a> Deref for BytesDecl<'a> {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        &*self.element
    }
}

impl<'a> Deref for BytesEnd<'a> {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        &*self.name
    }
}

impl<'a> Deref for BytesText<'a> {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        &*self.content
    }
}

impl<'a> Deref for Event<'a> {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        match *self {
            Event::Start(ref e) | Event::Empty(ref e) => &*e,
            Event::End(ref e) => &*e,
            Event::Text(ref e) => &*e,
            Event::Decl(ref e) => &*e,
            Event::PI(ref e) => &*e,
            Event::CData(ref e) => &*e,
            Event::Comment(ref e) => &*e,
            Event::DocType(ref e) => &*e,
            Event::Eof => &[],
        }
    }
}

impl<'a> AsRef<Event<'a>> for Event<'a> {
    fn as_ref(&self) -> &Event<'a> {
        self
    }
}

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

    #[test]
    fn local_name() {
        use std::str::from_utf8;
        let xml = r#"
            <foo:bus attr='bar'>foobusbar</foo:bus>
            <foo: attr='bar'>foobusbar</foo:>
            <:foo attr='bar'>foobusbar</:foo>
            <foo:bus:baz attr='bar'>foobusbar</foo:bus:baz>
            "#;
        let mut rdr = Reader::from_str(xml);
        let mut buf = Vec::new();
        let mut parsed_local_names = Vec::new();
        loop {
            match rdr.read_event(&mut buf).expect("unable to read xml event") {
                Event::Start(ref e) => parsed_local_names.push(
                    from_utf8(e.local_name())
                        .expect("unable to build str from local_name")
                        .to_string(),
                ),
                Event::End(ref e) => parsed_local_names.push(
                    from_utf8(e.local_name())
                        .expect("unable to build str from local_name")
                        .to_string(),
                ),
                Event::Eof => break,
                _ => {}
            }
        }
        assert_eq!(parsed_local_names[0], "bus".to_string());
        assert_eq!(parsed_local_names[1], "bus".to_string());
        assert_eq!(parsed_local_names[2], "".to_string());
        assert_eq!(parsed_local_names[3], "".to_string());
        assert_eq!(parsed_local_names[4], "foo".to_string());
        assert_eq!(parsed_local_names[5], "foo".to_string());
        assert_eq!(parsed_local_names[6], "bus:baz".to_string());
        assert_eq!(parsed_local_names[7], "bus:baz".to_string());
    }

    #[test]
    fn bytestart_create() {
        let b = BytesStart::owned_name("test");
        assert_eq!(b.len(), 4);
        assert_eq!(b.name(), b"test");
    }

    #[test]
    fn bytestart_set_name() {
        let mut b = BytesStart::owned_name("test");
        assert_eq!(b.len(), 4);
        assert_eq!(b.name(), b"test");
        assert_eq!(b.attributes_raw(), b"");
        b.push_attribute(("x", "a"));
        assert_eq!(b.len(), 10);
        assert_eq!(b.attributes_raw(), b" x=\"a\"");
        b.set_name(b"g");
        assert_eq!(b.len(), 7);
        assert_eq!(b.name(), b"g");
    }

    #[test]
    fn bytestart_clear_attributes() {
        let mut b = BytesStart::owned_name("test");
        b.push_attribute(("x", "y\"z"));
        b.push_attribute(("x", "y\"z"));
        b.clear_attributes();
        assert!(b.attributes().next().is_none());
        assert_eq!(b.len(), 4);
        assert_eq!(b.name(), b"test");
    }
}