//! A [N3](https://w3c.github.io/N3/spec/) streaming parser implemented by [`N3Parser`].

use crate::lexer::{resolve_local_name, N3Lexer, N3LexerMode, N3LexerOptions, N3Token};
#[cfg(feature = "async-tokio")]
use crate::toolkit::FromTokioAsyncReadIterator;
use crate::toolkit::{
    FromReadIterator, Lexer, Parser, RuleRecognizer, RuleRecognizerError, TurtleSyntaxError,
};
use crate::{TurtleParseError, MAX_BUFFER_SIZE, MIN_BUFFER_SIZE};
use oxiri::{Iri, IriParseError};
use oxrdf::vocab::{rdf, xsd};
#[cfg(feature = "rdf-star")]
use oxrdf::Triple;
use oxrdf::{
    BlankNode, GraphName, Literal, NamedNode, NamedNodeRef, NamedOrBlankNode, Quad, Subject, Term,
    Variable,
};
use std::collections::hash_map::Iter;
use std::collections::HashMap;
use std::fmt;
use std::io::Read;
#[cfg(feature = "async-tokio")]
use tokio::io::AsyncRead;

/// A N3 term i.e. a RDF `Term` or a `Variable`.
#[derive(Eq, PartialEq, Debug, Clone, Hash)]
pub enum N3Term {
    NamedNode(NamedNode),
    BlankNode(BlankNode),
    Literal(Literal),
    #[cfg(feature = "rdf-star")]
    Triple(Box<Triple>),
    Variable(Variable),
}

impl fmt::Display for N3Term {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::NamedNode(term) => term.fmt(f),
            Self::BlankNode(term) => term.fmt(f),
            Self::Literal(term) => term.fmt(f),
            #[cfg(feature = "rdf-star")]
            Self::Triple(term) => term.fmt(f),
            Self::Variable(term) => term.fmt(f),
        }
    }
}

impl From<NamedNode> for N3Term {
    #[inline]
    fn from(node: NamedNode) -> Self {
        Self::NamedNode(node)
    }
}

impl From<NamedNodeRef<'_>> for N3Term {
    #[inline]
    fn from(node: NamedNodeRef<'_>) -> Self {
        Self::NamedNode(node.into_owned())
    }
}

impl From<BlankNode> for N3Term {
    #[inline]
    fn from(node: BlankNode) -> Self {
        Self::BlankNode(node)
    }
}

impl From<Literal> for N3Term {
    #[inline]
    fn from(literal: Literal) -> Self {
        Self::Literal(literal)
    }
}

#[cfg(feature = "rdf-star")]
impl From<Triple> for N3Term {
    #[inline]
    fn from(triple: Triple) -> Self {
        Self::Triple(Box::new(triple))
    }
}

#[cfg(feature = "rdf-star")]
impl From<Box<Triple>> for N3Term {
    #[inline]
    fn from(node: Box<Triple>) -> Self {
        Self::Triple(node)
    }
}

impl From<NamedOrBlankNode> for N3Term {
    #[inline]
    fn from(node: NamedOrBlankNode) -> Self {
        match node {
            NamedOrBlankNode::NamedNode(node) => node.into(),
            NamedOrBlankNode::BlankNode(node) => node.into(),
        }
    }
}

impl From<Subject> for N3Term {
    #[inline]
    fn from(node: Subject) -> Self {
        match node {
            Subject::NamedNode(node) => node.into(),
            Subject::BlankNode(node) => node.into(),
            #[cfg(feature = "rdf-star")]
            Subject::Triple(triple) => Self::Triple(triple),
        }
    }
}

impl From<Term> for N3Term {
    #[inline]
    fn from(node: Term) -> Self {
        match node {
            Term::NamedNode(node) => node.into(),
            Term::BlankNode(node) => node.into(),
            Term::Literal(node) => node.into(),
            #[cfg(feature = "rdf-star")]
            Term::Triple(triple) => Self::Triple(triple),
        }
    }
}

impl From<Variable> for N3Term {
    #[inline]
    fn from(variable: Variable) -> Self {
        Self::Variable(variable)
    }
}

/// A N3 quad i.e. a quad composed of [`N3Term`].
///
/// The `graph_name` is used to encode the formula where the triple is in.
/// In this case the formula is encoded by a blank node.
#[derive(Eq, PartialEq, Debug, Clone, Hash)]
pub struct N3Quad {
    /// The [subject](https://www.w3.org/TR/rdf11-concepts/#dfn-subject) of this triple.
    pub subject: N3Term,

    /// The [predicate](https://www.w3.org/TR/rdf11-concepts/#dfn-predicate) of this triple.
    pub predicate: N3Term,

    /// The [object](https://www.w3.org/TR/rdf11-concepts/#dfn-object) of this triple.
    pub object: N3Term,

    /// The name of the RDF [graph](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-graph) in which the triple is.
    pub graph_name: GraphName,
}

impl fmt::Display for N3Quad {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.graph_name == GraphName::DefaultGraph {
            write!(f, "{} {} {}", self.subject, self.predicate, self.object)
        } else {
            write!(
                f,
                "{} {} {} {}",
                self.subject, self.predicate, self.object, self.graph_name
            )
        }
    }
}

impl From<Quad> for N3Quad {
    fn from(quad: Quad) -> Self {
        Self {
            subject: quad.subject.into(),
            predicate: quad.predicate.into(),
            object: quad.object.into(),
            graph_name: quad.graph_name,
        }
    }
}

/// A [N3](https://w3c.github.io/N3/spec/) streaming parser.
///
/// Count the number of people:
/// ```
/// use oxrdf::vocab::rdf;
/// use oxrdf::NamedNode;
/// use oxttl::n3::{N3Parser, N3Term};
///
/// let file = br#"@base <http://example.com/> .
/// @prefix schema: <http://schema.org/> .
/// <foo> a schema:Person ;
///     schema:name "Foo" .
/// <bar> a schema:Person ;
///     schema:name "Bar" ."#;
///
/// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
/// let schema_person = N3Term::NamedNode(NamedNode::new("http://schema.org/Person")?);
/// let mut count = 0;
/// for triple in N3Parser::new().parse_read(file.as_ref()) {
///     let triple = triple?;
///     if triple.predicate == rdf_type && triple.object == schema_person {
///         count += 1;
///     }
/// }
/// assert_eq!(2, count);
/// # Result::<_,Box<dyn std::error::Error>>::Ok(())
/// ```
#[derive(Default)]
#[must_use]
pub struct N3Parser {
    unchecked: bool,
    base: Option<Iri<String>>,
    prefixes: HashMap<String, Iri<String>>,
}

impl N3Parser {
    /// Builds a new [`N3Parser`].
    #[inline]
    pub fn new() -> Self {
        Self::default()
    }

    /// Assumes the file is valid to make parsing faster.
    ///
    /// It will skip some validations.
    ///
    /// Note that if the file is actually not valid, then broken RDF might be emitted by the parser.
    #[inline]
    pub fn unchecked(mut self) -> Self {
        self.unchecked = true;
        self
    }

    #[inline]
    pub fn with_base_iri(mut self, base_iri: impl Into<String>) -> Result<Self, IriParseError> {
        self.base = Some(Iri::parse(base_iri.into())?);
        Ok(self)
    }

    #[inline]
    pub fn with_prefix(
        mut self,
        prefix_name: impl Into<String>,
        prefix_iri: impl Into<String>,
    ) -> Result<Self, IriParseError> {
        self.prefixes
            .insert(prefix_name.into(), Iri::parse(prefix_iri.into())?);
        Ok(self)
    }

    /// Parses a N3 file from a [`Read`] implementation.
    ///
    /// Count the number of people:
    /// ```
    /// use oxrdf::NamedNode;
    /// use oxttl::n3::{N3Parser, N3Term};
    ///
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" .
    /// <bar> a schema:Person ;
    ///     schema:name "Bar" ."#;
    ///
    /// let rdf_type = N3Term::NamedNode(NamedNode::new(
    ///     "http://www.w3.org/1999/02/22-rdf-syntax-ns#type",
    /// )?);
    /// let schema_person = N3Term::NamedNode(NamedNode::new("http://schema.org/Person")?);
    /// let mut count = 0;
    /// for triple in N3Parser::new().parse_read(file.as_ref()) {
    ///     let triple = triple?;
    ///     if triple.predicate == rdf_type && triple.object == schema_person {
    ///         count += 1;
    ///     }
    /// }
    /// assert_eq!(2, count);
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn parse_read<R: Read>(self, read: R) -> FromReadN3Reader<R> {
        FromReadN3Reader {
            inner: self.parse().parser.parse_read(read),
        }
    }

    /// Parses a N3 file from a [`AsyncRead`] implementation.
    ///
    /// Count the number of people:
    /// ```
    /// use oxrdf::vocab::rdf;
    /// use oxrdf::NamedNode;
    /// use oxttl::n3::{N3Parser, N3Term};
    ///
    /// # #[tokio::main(flavor = "current_thread")]
    /// # async fn main() -> Result<(), oxttl::TurtleParseError> {
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" .
    /// <bar> a schema:Person ;
    ///     schema:name "Bar" ."#;
    ///
    /// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
    /// let schema_person = N3Term::NamedNode(NamedNode::new_unchecked("http://schema.org/Person"));
    /// let mut count = 0;
    /// let mut parser = N3Parser::new().parse_tokio_async_read(file.as_ref());
    /// while let Some(triple) = parser.next().await {
    ///     let triple = triple?;
    ///     if triple.predicate == rdf_type && triple.object == schema_person {
    ///         count += 1;
    ///     }
    /// }
    /// assert_eq!(2, count);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(feature = "async-tokio")]
    pub fn parse_tokio_async_read<R: AsyncRead + Unpin>(
        self,
        read: R,
    ) -> FromTokioAsyncReadN3Reader<R> {
        FromTokioAsyncReadN3Reader {
            inner: self.parse().parser.parse_tokio_async_read(read),
        }
    }

    /// Allows to parse a N3 file by using a low-level API.
    ///
    /// Count the number of people:
    /// ```
    /// use oxrdf::vocab::rdf;
    /// use oxrdf::NamedNode;
    /// use oxttl::n3::{N3Parser, N3Term};
    ///
    /// let file: [&[u8]; 5] = [
    ///     b"@base <http://example.com/>",
    ///     b". @prefix schema: <http://schema.org/> .",
    ///     b"<foo> a schema:Person",
    ///     b" ; schema:name \"Foo\" . <bar>",
    ///     b" a schema:Person ; schema:name \"Bar\" .",
    /// ];
    ///
    /// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
    /// let schema_person = N3Term::NamedNode(NamedNode::new("http://schema.org/Person")?);
    /// let mut count = 0;
    /// let mut parser = N3Parser::new().parse();
    /// let mut file_chunks = file.iter();
    /// while !parser.is_end() {
    ///     // We feed more data to the parser
    ///     if let Some(chunk) = file_chunks.next() {
    ///         parser.extend_from_slice(chunk);
    ///     } else {
    ///         parser.end(); // It's finished
    ///     }
    ///     // We read as many triples from the parser as possible
    ///     while let Some(triple) = parser.read_next() {
    ///         let triple = triple?;
    ///         if triple.predicate == rdf_type && triple.object == schema_person {
    ///             count += 1;
    ///         }
    ///     }
    /// }
    /// assert_eq!(2, count);
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn parse(self) -> LowLevelN3Reader {
        LowLevelN3Reader {
            parser: N3Recognizer::new_parser(self.unchecked, self.base, self.prefixes),
        }
    }
}

/// Parses a N3 file from a [`Read`] implementation. Can be built using [`N3Parser::parse_read`].
///
/// Count the number of people:
/// ```
/// use oxrdf::vocab::rdf;
/// use oxrdf::NamedNode;
/// use oxttl::n3::{N3Parser, N3Term};
///
/// let file = br#"@base <http://example.com/> .
/// @prefix schema: <http://schema.org/> .
/// <foo> a schema:Person ;
///     schema:name "Foo" .
/// <bar> a schema:Person ;
///     schema:name "Bar" ."#;
///
/// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
/// let schema_person = N3Term::NamedNode(NamedNode::new("http://schema.org/Person")?);
/// let mut count = 0;
/// for triple in N3Parser::new().parse_read(file.as_ref()) {
///     let triple = triple?;
///     if triple.predicate == rdf_type && triple.object == schema_person {
///         count += 1;
///     }
/// }
/// assert_eq!(2, count);
/// # Result::<_,Box<dyn std::error::Error>>::Ok(())
/// ```
#[must_use]
pub struct FromReadN3Reader<R: Read> {
    inner: FromReadIterator<R, N3Recognizer>,
}

impl<R: Read> FromReadN3Reader<R> {
    /// The list of IRI prefixes considered at the current step of the parsing.
    ///
    /// This method returns (prefix name, prefix value) tuples.
    /// It is empty at the beginning of the parsing and gets updated when prefixes are encountered.
    /// It should be full at the end of the parsing (but if a prefix is overridden, only the latest version will be returned).
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse_read(file.as_ref());
    /// assert_eq!(reader.prefixes().collect::<Vec<_>>(), []); // No prefix at the beginning
    ///
    /// reader.next().unwrap()?; // We read the first triple
    /// assert_eq!(
    ///     reader.prefixes().collect::<Vec<_>>(),
    ///     [("schema", "http://schema.org/")]
    /// ); // There are now prefixes
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn prefixes(&self) -> N3PrefixesIter<'_> {
        N3PrefixesIter {
            inner: self.inner.parser.context.prefixes.iter(),
        }
    }

    /// The base IRI considered at the current step of the parsing.
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse_read(file.as_ref());
    /// assert!(reader.base_iri().is_none()); // No base at the beginning because none has been given to the parser.
    ///
    /// reader.next().unwrap()?; // We read the first triple
    /// assert_eq!(reader.base_iri(), Some("http://example.com/")); // There is now a base IRI.
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn base_iri(&self) -> Option<&str> {
        self.inner
            .parser
            .context
            .lexer_options
            .base_iri
            .as_ref()
            .map(Iri::as_str)
    }
}

impl<R: Read> Iterator for FromReadN3Reader<R> {
    type Item = Result<N3Quad, TurtleParseError>;

    fn next(&mut self) -> Option<Self::Item> {
        self.inner.next()
    }
}

/// Parses a N3 file from a [`AsyncRead`] implementation. Can be built using [`N3Parser::parse_tokio_async_read`].
///
/// Count the number of people:
/// ```
/// use oxrdf::vocab::rdf;
/// use oxrdf::NamedNode;
/// use oxttl::n3::{N3Parser, N3Term};
///
/// # #[tokio::main(flavor = "current_thread")]
/// # async fn main() -> Result<(), oxttl::TurtleParseError> {
/// let file = br#"@base <http://example.com/> .
/// @prefix schema: <http://schema.org/> .
/// <foo> a schema:Person ;
///     schema:name "Foo" .
/// <bar> a schema:Person ;
///     schema:name "Bar" ."#;
///
/// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
/// let schema_person = N3Term::NamedNode(NamedNode::new_unchecked("http://schema.org/Person"));
/// let mut count = 0;
/// let mut parser = N3Parser::new().parse_tokio_async_read(file.as_ref());
/// while let Some(triple) = parser.next().await {
///     let triple = triple?;
///     if triple.predicate == rdf_type && triple.object == schema_person {
///         count += 1;
///     }
/// }
/// assert_eq!(2, count);
/// # Ok(())
/// # }
/// ```
#[cfg(feature = "async-tokio")]
#[must_use]
pub struct FromTokioAsyncReadN3Reader<R: AsyncRead + Unpin> {
    inner: FromTokioAsyncReadIterator<R, N3Recognizer>,
}

#[cfg(feature = "async-tokio")]
impl<R: AsyncRead + Unpin> FromTokioAsyncReadN3Reader<R> {
    /// Reads the next triple or returns `None` if the file is finished.
    pub async fn next(&mut self) -> Option<Result<N3Quad, TurtleParseError>> {
        Some(self.inner.next().await?.map(Into::into))
    }

    /// The list of IRI prefixes considered at the current step of the parsing.
    ///
    /// This method returns (prefix name, prefix value) tuples.
    /// It is empty at the beginning of the parsing and gets updated when prefixes are encountered.
    /// It should be full at the end of the parsing (but if a prefix is overridden, only the latest version will be returned).
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// # #[tokio::main(flavor = "current_thread")]
    /// # async fn main() -> Result<(), oxttl::TurtleParseError> {
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse_tokio_async_read(file.as_ref());
    /// assert_eq!(reader.prefixes().collect::<Vec<_>>(), []); // No prefix at the beginning
    ///
    /// reader.next().await.unwrap()?; // We read the first triple
    /// assert_eq!(
    ///     reader.prefixes().collect::<Vec<_>>(),
    ///     [("schema", "http://schema.org/")]
    /// ); // There are now prefixes
    /// # Ok(())
    /// # }
    /// ```
    pub fn prefixes(&self) -> N3PrefixesIter<'_> {
        N3PrefixesIter {
            inner: self.inner.parser.context.prefixes.iter(),
        }
    }

    /// The base IRI considered at the current step of the parsing.
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// # #[tokio::main(flavor = "current_thread")]
    /// # async fn main() -> Result<(), oxttl::TurtleParseError> {
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse_tokio_async_read(file.as_ref());
    /// assert!(reader.base_iri().is_none()); // No base IRI at the beginning
    ///
    /// reader.next().await.unwrap()?; // We read the first triple
    /// assert_eq!(reader.base_iri(), Some("http://example.com/")); // There is now a base IRI
    /// # Ok(())
    /// # }
    /// ```
    pub fn base_iri(&self) -> Option<&str> {
        self.inner
            .parser
            .context
            .lexer_options
            .base_iri
            .as_ref()
            .map(Iri::as_str)
    }
}

/// Parses a N3 file by using a low-level API. Can be built using [`N3Parser::parse`].
///
/// Count the number of people:
/// ```
/// use oxrdf::vocab::rdf;
/// use oxrdf::NamedNode;
/// use oxttl::n3::{N3Parser, N3Term};
///
/// let file: [&[u8]; 5] = [
///     b"@base <http://example.com/>",
///     b". @prefix schema: <http://schema.org/> .",
///     b"<foo> a schema:Person",
///     b" ; schema:name \"Foo\" . <bar>",
///     b" a schema:Person ; schema:name \"Bar\" .",
/// ];
///
/// let rdf_type = N3Term::NamedNode(rdf::TYPE.into_owned());
/// let schema_person = N3Term::NamedNode(NamedNode::new("http://schema.org/Person")?);
/// let mut count = 0;
/// let mut parser = N3Parser::new().parse();
/// let mut file_chunks = file.iter();
/// while !parser.is_end() {
///     // We feed more data to the parser
///     if let Some(chunk) = file_chunks.next() {
///         parser.extend_from_slice(chunk);
///     } else {
///         parser.end(); // It's finished
///     }
///     // We read as many triples from the parser as possible
///     while let Some(triple) = parser.read_next() {
///         let triple = triple?;
///         if triple.predicate == rdf_type && triple.object == schema_person {
///             count += 1;
///         }
///     }
/// }
/// assert_eq!(2, count);
/// # Result::<_,Box<dyn std::error::Error>>::Ok(())
/// ```
pub struct LowLevelN3Reader {
    parser: Parser<N3Recognizer>,
}

impl LowLevelN3Reader {
    /// Adds some extra bytes to the parser. Should be called when [`read_next`](Self::read_next) returns [`None`] and there is still unread data.
    pub fn extend_from_slice(&mut self, other: &[u8]) {
        self.parser.extend_from_slice(other)
    }

    /// Tell the parser that the file is finished.
    ///
    /// This triggers the parsing of the final bytes and might lead [`read_next`](Self::read_next) to return some extra values.
    pub fn end(&mut self) {
        self.parser.end()
    }

    /// Returns if the parsing is finished i.e. [`end`](Self::end) has been called and [`read_next`](Self::read_next) is always going to return `None`.
    pub fn is_end(&self) -> bool {
        self.parser.is_end()
    }

    /// Attempt to parse a new quad from the already provided data.
    ///
    /// Returns [`None`] if the parsing is finished or more data is required.
    /// If it is the case more data should be fed using [`extend_from_slice`](Self::extend_from_slice).
    pub fn read_next(&mut self) -> Option<Result<N3Quad, TurtleSyntaxError>> {
        self.parser.read_next()
    }

    /// The list of IRI prefixes considered at the current step of the parsing.
    ///
    /// This method returns (prefix name, prefix value) tuples.
    /// It is empty at the beginning of the parsing and gets updated when prefixes are encountered.
    /// It should be full at the end of the parsing (but if a prefix is overridden, only the latest version will be returned).
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse();
    /// reader.extend_from_slice(file);
    /// assert_eq!(reader.prefixes().collect::<Vec<_>>(), []); // No prefix at the beginning
    ///
    /// reader.read_next().unwrap()?; // We read the first triple
    /// assert_eq!(
    ///     reader.prefixes().collect::<Vec<_>>(),
    ///     [("schema", "http://schema.org/")]
    /// ); // There are now prefixes
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn prefixes(&self) -> N3PrefixesIter<'_> {
        N3PrefixesIter {
            inner: self.parser.context.prefixes.iter(),
        }
    }

    /// The base IRI considered at the current step of the parsing.
    ///
    /// ```
    /// use oxttl::N3Parser;
    ///
    /// let file = br#"@base <http://example.com/> .
    /// @prefix schema: <http://schema.org/> .
    /// <foo> a schema:Person ;
    ///     schema:name "Foo" ."#;
    ///
    /// let mut reader = N3Parser::new().parse();
    /// reader.extend_from_slice(file);
    /// assert!(reader.base_iri().is_none()); // No base IRI at the beginning
    ///
    /// reader.read_next().unwrap()?; // We read the first triple
    /// assert_eq!(reader.base_iri(), Some("http://example.com/")); // There is now a base IRI
    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
    /// ```
    pub fn base_iri(&self) -> Option<&str> {
        self.parser
            .context
            .lexer_options
            .base_iri
            .as_ref()
            .map(Iri::as_str)
    }
}

#[derive(Clone)]
enum Predicate {
    Regular(N3Term),
    Inverted(N3Term),
}

struct N3Recognizer {
    stack: Vec<N3State>,
    terms: Vec<N3Term>,
    predicates: Vec<Predicate>,
    contexts: Vec<BlankNode>,
}

struct N3RecognizerContext {
    lexer_options: N3LexerOptions,
    prefixes: HashMap<String, Iri<String>>,
}

impl RuleRecognizer for N3Recognizer {
    type TokenRecognizer = N3Lexer;
    type Output = N3Quad;
    type Context = N3RecognizerContext;

    fn error_recovery_state(mut self) -> Self {
        self.stack.clear();
        self.terms.clear();
        self.predicates.clear();
        self.contexts.clear();
        self
    }

    fn recognize_next(
        mut self,
        token: N3Token<'_>,
        context: &mut N3RecognizerContext,
        results: &mut Vec<N3Quad>,
        errors: &mut Vec<RuleRecognizerError>,
    ) -> Self {
        while let Some(rule) = self.stack.pop() {
            match rule {
                // [1]  n3Doc            ::=  ( ( n3Statement ".") | sparqlDirective) *
                // [2]  n3Statement      ::=  n3Directive | triples
                // [3]  n3Directive      ::=  prefixID | base
                // [4]  sparqlDirective  ::=  sparqlBase | sparqlPrefix
                // [5]  sparqlBase       ::=  BASE IRIREF
                // [6]  sparqlPrefix     ::=  PREFIX PNAME_NS IRIREF
                // [7]  prefixID         ::=  "@prefix" PNAME_NS IRIREF
                // [8]  base             ::=  "@base" IRIREF
                N3State::N3Doc => {
                    self.stack.push(N3State::N3Doc);
                    match token {
                        N3Token::PlainKeyword(k) if k.eq_ignore_ascii_case("base") => {
                            self.stack.push(N3State::BaseExpectIri);
                            return self;
                        }
                        N3Token::PlainKeyword(k) if k.eq_ignore_ascii_case("prefix") => {
                            self.stack.push(N3State::PrefixExpectPrefix);
                            return self;
                        }
                        N3Token::LangTag("prefix") => {
                            self.stack.push(N3State::N3DocExpectDot);
                            self.stack.push(N3State::PrefixExpectPrefix);
                            return self;
                        }
                        N3Token::LangTag("base") => {
                            self.stack.push(N3State::N3DocExpectDot);
                            self.stack.push(N3State::BaseExpectIri);
                            return self;
                        }
                        _ => {
                            self.stack.push(N3State::N3DocExpectDot);
                            self.stack.push(N3State::Triples);
                        }
                    }
                }
                N3State::N3DocExpectDot => {
                    if token == N3Token::Punctuation(".") {
                        return self;
                    }
                    errors.push("A dot is expected at the end of N3 statements".into());
                }
                N3State::BaseExpectIri => return match token {
                    N3Token::IriRef(iri) => {
                        match Iri::parse_unchecked(iri) {
                            Ok(iri) => {
                                context.lexer_options.base_iri = Some(iri);
                                self
                            }
                            Err(e) => self.error(errors, format!("Invalid base IRI: {e}"))
                        }
                    }
                    _ => self.error(errors, "The BASE keyword should be followed by an IRI"),
                },
                N3State::PrefixExpectPrefix => return match token {
                    N3Token::PrefixedName { prefix, local, .. } if local.is_empty() => {
                        self.stack.push(N3State::PrefixExpectIri { name: prefix.to_owned() });
                        self
                    }
                    _ => {
                        self.error(errors, "The PREFIX keyword should be followed by a prefix like 'ex:'")
                    }
                },
                N3State::PrefixExpectIri { name } => return match token {
                    N3Token::IriRef(iri) => {
                        match Iri::parse_unchecked(iri) {
                            Ok(iri) => {
                                context.prefixes.insert(name, iri);
                                self
                            }
                            Err(e) => self.error(errors, format!("Invalid prefix IRI: {e}"))
                        }
                    }
                    _ => self.error(errors, "The PREFIX declaration should be followed by a prefix and its value as an IRI"),
                },
                // [9]  triples  ::=  subject predicateObjectList?
                N3State::Triples => {
                    self.stack.push(N3State::TriplesMiddle);
                    self.stack.push(N3State::Path);
                }
                N3State::TriplesMiddle => if matches!(token, N3Token::Punctuation("." | "]" | "}" | ")")) {} else {
                    self.stack.push(N3State::TriplesEnd);
                    self.stack.push(N3State::PredicateObjectList);
                },
                N3State::TriplesEnd => {
                    self.terms.pop();
                }
                // [10]  predicateObjectList  ::=  verb objectList ( ";" ( verb objectList) ? ) *
                N3State::PredicateObjectList => {
                    self.stack.push(N3State::PredicateObjectListEnd);
                    self.stack.push(N3State::ObjectsList);
                    self.stack.push(N3State::Verb);
                }
                N3State::PredicateObjectListEnd => {
                    self.predicates.pop();
                    if token == N3Token::Punctuation(";") {
                        self.stack.push(N3State::PredicateObjectListPossibleContinuation);
                        return self;
                    }
                }
                N3State::PredicateObjectListPossibleContinuation => if token == N3Token::Punctuation(";") {
                    self.stack.push(N3State::PredicateObjectListPossibleContinuation);
                    return self;
                } else if matches!(token, N3Token::Punctuation(";" | "." | "}" | "]" | ")")) {} else {
                    self.stack.push(N3State::PredicateObjectListEnd);
                    self.stack.push(N3State::ObjectsList);
                    self.stack.push(N3State::Verb);
                },
                // [11]  objectList  ::=  object ( "," object) *
                N3State::ObjectsList => {
                    self.stack.push(N3State::ObjectsListEnd);
                    self.stack.push(N3State::Path);
                }
                N3State::ObjectsListEnd => {
                    let object = self.terms.pop().unwrap();
                    let subject = self.terms.last().unwrap().clone();
                    results.push(match self.predicates.last().unwrap().clone() {
                        Predicate::Regular(predicate) => self.quad(
                            subject,
                            predicate,
                            object,
                        ),
                        Predicate::Inverted(predicate) => self.quad(
                            object,
                            predicate,
                            subject,
                        )
                    });
                    if token == N3Token::Punctuation(",") {
                        self.stack.push(N3State::ObjectsListEnd);
                        self.stack.push(N3State::Path);
                        return self;
                    }
                }
                // [12]  verb       ::=  predicate | "a" | ( "has" expression) | ( "is" expression "of") | "=" | "<=" | "=>"
                // [14]  predicate  ::=  expression | ( "<-" expression)
                N3State::Verb => match token {
                    N3Token::PlainKeyword("a") => {
                        self.predicates.push(Predicate::Regular(rdf::TYPE.into()));
                        return self;
                    }
                    N3Token::PlainKeyword("has") => {
                        self.stack.push(N3State::AfterRegularVerb);
                        self.stack.push(N3State::Path);
                        return self;
                    }
                    N3Token::PlainKeyword("is") => {
                        self.stack.push(N3State::AfterVerbIs);
                        self.stack.push(N3State::Path);
                        return self;
                    }
                    N3Token::Punctuation("=") => {
                        self.predicates.push(Predicate::Regular(NamedNode::new_unchecked("http://www.w3.org/2002/07/owl#sameAs").into()));
                        return self;
                    }
                    N3Token::Punctuation("=>") => {
                        self.predicates.push(Predicate::Regular(NamedNode::new_unchecked("http://www.w3.org/2000/10/swap/log#implies").into()));
                        return self;
                    }
                    N3Token::Punctuation("<=") => {
                        self.predicates.push(Predicate::Inverted(NamedNode::new_unchecked("http://www.w3.org/2000/10/swap/log#implies").into()));
                        return self;
                    }
                    N3Token::Punctuation("<-") => {
                        self.stack.push(N3State::AfterInvertedVerb);
                        self.stack.push(N3State::Path);
                        return self;
                    }
                    _ => {
                        self.stack.push(N3State::AfterRegularVerb);
                        self.stack.push(N3State::Path);
                    }
                }
                N3State::AfterRegularVerb => {
                    self.predicates.push(Predicate::Regular(self.terms.pop().unwrap()));
                }
                N3State::AfterInvertedVerb => {
                    self.predicates.push(Predicate::Inverted(self.terms.pop().unwrap()));
                }
                N3State::AfterVerbIs => return match token {
                    N3Token::PlainKeyword("of") => {
                        self.predicates.push(Predicate::Inverted(self.terms.pop().unwrap()));
                        self
                    }
                    _ => {
                        self.error(errors, "The keyword 'is' should be followed by a predicate then by the keyword 'of'")
                    }
                },
                // [13]  subject     ::=  expression
                // [15]  object      ::=  expression
                // [16]  expression  ::=  path
                // [17]  path        ::=  pathItem ( ( "!" path) | ( "^" path) ) ?
                N3State::Path => {
                    self.stack.push(N3State::PathFollowUp);
                    self.stack.push(N3State::PathItem);
                }
                N3State::PathFollowUp => match token {
                    N3Token::Punctuation("!") => {
                        self.stack.push(N3State::PathAfterIndicator { is_inverse: false });
                        self.stack.push(N3State::PathItem);
                        return self;
                    }
                    N3Token::Punctuation("^") => {
                        self.stack.push(N3State::PathAfterIndicator { is_inverse: true });
                        self.stack.push(N3State::PathItem);
                        return self;
                    }
                    _ => ()
                },
                N3State::PathAfterIndicator { is_inverse } => {
                    let predicate = self.terms.pop().unwrap();
                    let previous = self.terms.pop().unwrap();
                    let current = BlankNode::default();
                    results.push(if is_inverse { self.quad(current.clone(), predicate, previous) } else { self.quad(previous, predicate, current.clone()) });
                    self.terms.push(current.into());
                    self.stack.push(N3State::PathFollowUp);
                }
                // [18]  pathItem               ::=  iri | blankNode | quickVar | collection | blankNodePropertyList | iriPropertyList | literal | formula
                // [19]  literal                ::=  rdfLiteral | numericLiteral | BOOLEAN_LITERAL
                // [20]  blankNodePropertyList  ::=  "[" predicateObjectList "]"
                // [21]  iriPropertyList        ::=  IPLSTART iri predicateObjectList "]"
                // [22]  collection             ::=  "(" object* ")"
                // [23]  formula                ::=  "{" formulaContent? "}"
                // [25]  numericLiteral         ::=  DOUBLE | DECIMAL | INTEGER
                // [26]  rdfLiteral             ::=  STRING ( LANGTAG | ( "^^" iri) ) ?
                // [27]  iri                    ::=  IRIREF | prefixedName
                // [28]  prefixedName           ::=  PNAME_LN | PNAME_NS
                // [29]  blankNode              ::=  BLANK_NODE_LABEL | ANON
                // [30]  quickVar               ::=  QUICK_VAR_NAME
                N3State::PathItem => {
                    return match token {
                        N3Token::IriRef(iri) => {
                            self.terms.push(NamedNode::new_unchecked(iri).into());
                            self
                        }
                        N3Token::PrefixedName { prefix, local, might_be_invalid_iri } => match resolve_local_name(prefix, &local, might_be_invalid_iri, &context.prefixes) {
                            Ok(t) => {
                                self.terms.push(t.into());
                                self
                            }
                            Err(e) =>  self.error(errors, e)
                        }
                        N3Token::BlankNodeLabel(bnode) => {
                            self.terms.push(BlankNode::new_unchecked(bnode).into());
                            self
                        }
                        N3Token::Variable(name) => {
                            self.terms.push(Variable::new_unchecked(name).into());
                            self
                        }
                        N3Token::Punctuation("[") => {
                            self.stack.push(N3State::PropertyListMiddle);
                            self
                        }
                        N3Token::Punctuation("(") => {
                            self.stack.push(N3State::CollectionBeginning);
                            self
                        }
                        N3Token::String(value) => {
                            self.stack.push(N3State::LiteralPossibleSuffix { value });
                            self
                        }
                        N3Token::Integer(v) => {
                            self.terms.push(Literal::new_typed_literal(v, xsd::INTEGER).into());
                            self
                        }
                        N3Token::Decimal(v) => {
                            self.terms.push(Literal::new_typed_literal(v, xsd::DECIMAL).into());
                            self
                        }
                        N3Token::Double(v) => {
                            self.terms.push(Literal::new_typed_literal(v, xsd::DOUBLE).into());
                            self
                        }
                        N3Token::PlainKeyword("true") => {
                            self.terms.push(Literal::new_typed_literal("true", xsd::BOOLEAN).into());
                            self
                        }
                        N3Token::PlainKeyword("false") => {
                            self.terms.push(Literal::new_typed_literal("false", xsd::BOOLEAN).into());
                            self
                        }
                        N3Token::Punctuation("{") => {
                            self.contexts.push(BlankNode::default());
                            self.stack.push(N3State::FormulaContent);
                            self
                        }
                        _ =>
                            self.error(errors, "TOKEN is not a valid RDF value")

                    }
                }
                N3State::PropertyListMiddle => match token {
                    N3Token::Punctuation("]") => {
                        self.terms.push(BlankNode::default().into());
                        return self;
                    }
                    N3Token::PlainKeyword("id") => {
                        self.stack.push(N3State::IriPropertyList);
                        return self;
                    }
                    _ => {
                        self.terms.push(BlankNode::default().into());
                        self.stack.push(N3State::PropertyListEnd);
                        self.stack.push(N3State::PredicateObjectList);
                    }
                }
                N3State::PropertyListEnd => if token == N3Token::Punctuation("]") {
                    return self;
                } else {
                    errors.push("blank node property lists should end with a ']'".into());
                }
                N3State::IriPropertyList => return match token {
                    N3Token::IriRef(id) => {
                        self.terms.push(NamedNode::new_unchecked(id).into());
                        self.stack.push(N3State::PropertyListEnd);
                        self.stack.push(N3State::PredicateObjectList);
                        self
                    }
                    N3Token::PrefixedName { prefix, local, might_be_invalid_iri } => match resolve_local_name(prefix, &local, might_be_invalid_iri, &context.prefixes) {
                        Ok(t) => {
                            self.terms.push(t.into());
                            self.stack.push(N3State::PropertyListEnd);
                            self.stack.push(N3State::PredicateObjectList);
                            self
                        }
                        Err(e) => {
                            self.error(errors, e)
                        }
                    }
                    _ => {
                        self.error(errors, "The '[ id' construction should be followed by an IRI")
                    }
                },
                N3State::CollectionBeginning => if let N3Token::Punctuation(")") = token {
                    self.terms.push(rdf::NIL.into());
                    return self;
                } else {
                    let root = BlankNode::default();
                    self.terms.push(root.clone().into());
                    self.terms.push(root.into());
                    self.stack.push(N3State::CollectionPossibleEnd);
                    self.stack.push(N3State::Path);
                },
                N3State::CollectionPossibleEnd => {
                    let value = self.terms.pop().unwrap();
                    let old = self.terms.pop().unwrap();
                    results.push(self.quad(
                        old.clone(),
                        rdf::FIRST,
                        value,
                    ));
                    if let N3Token::Punctuation(")") = token {
                        results.push(self.quad(
                            old,
                            rdf::REST,
                            rdf::NIL,
                        ));
                        return self;
                    }
                    let new = BlankNode::default();
                    results.push(self.quad(
                        old,
                        rdf::REST,
                        new.clone(),
                    ));
                    self.terms.push(new.into());
                    self.stack.push(N3State::CollectionPossibleEnd);
                    self.stack.push(N3State::Path);
                }
                N3State::LiteralPossibleSuffix { value } => {
                    match token {
                        N3Token::LangTag(lang) => {
                            self.terms.push(Literal::new_language_tagged_literal_unchecked(value, lang.to_ascii_lowercase()).into());
                            return self;
                        }
                        N3Token::Punctuation("^^") => {
                            self.stack.push(N3State::LiteralExpectDatatype { value });
                            return self;
                        }
                        _ => {
                            self.terms.push(Literal::new_simple_literal(value).into());
                        }
                    }
                }
                N3State::LiteralExpectDatatype { value } => {
                    match token {
                        N3Token::IriRef(datatype) => {
                            self.terms.push(Literal::new_typed_literal(value, NamedNode::new_unchecked(datatype)).into());
                            return self;
                        }
                        N3Token::PrefixedName { prefix, local, might_be_invalid_iri } => match resolve_local_name(prefix, &local, might_be_invalid_iri, &context.prefixes) {
                            Ok(datatype) => {
                                self.terms.push(Literal::new_typed_literal(value, datatype).into());
                                return self;
                            }
                            Err(e) => {
                                return self.error(errors, e);
                            }
                        }
                        _ => {
                            errors.push("Expecting a datatype IRI after '^^, found TOKEN".into());
                            self.stack.clear();
                        }
                    }
                }
                // [24]  formulaContent  ::=  ( n3Statement ( "." formulaContent? ) ? ) | ( sparqlDirective formulaContent? )
                N3State::FormulaContent => {
                    match token {
                        N3Token::Punctuation("}") => {
                            self.terms.push(self.contexts.pop().unwrap().into());
                            return self;
                        }
                        N3Token::PlainKeyword(k)if k.eq_ignore_ascii_case("base") => {
                            self.stack.push(N3State::FormulaContent);
                            self.stack.push(N3State::BaseExpectIri);
                            return self;
                        }
                        N3Token::PlainKeyword(k)if k.eq_ignore_ascii_case("prefix") => {
                            self.stack.push(N3State::FormulaContent);
                            self.stack.push(N3State::PrefixExpectPrefix);
                            return self;
                        }
                        N3Token::LangTag("prefix") => {
                            self.stack.push(N3State::FormulaContentExpectDot);
                            self.stack.push(N3State::PrefixExpectPrefix);
                            return self;
                        }
                        N3Token::LangTag("base") => {
                            self.stack.push(N3State::FormulaContentExpectDot);
                            self.stack.push(N3State::BaseExpectIri);
                            return self;
                        }
                        _ => {
                            self.stack.push(N3State::FormulaContentExpectDot);
                            self.stack.push(N3State::Triples);
                        }
                    }
                }
                N3State::FormulaContentExpectDot => {
                    match token {
                        N3Token::Punctuation("}") => {
                            self.terms.push(self.contexts.pop().unwrap().into());
                            return self;
                        }
                        N3Token::Punctuation(".") => {
                            self.stack.push(N3State::FormulaContent);
                            return self;
                        }
                        _ => {
                            errors.push("A dot is expected at the end of N3 statements".into());
                            self.stack.push(N3State::FormulaContent);
                        }
                    }
                }
            }
        }
        // Empty stack
        if token == N3Token::Punctuation(".") {
            self.stack.push(N3State::N3Doc);
            self
        } else {
            self
        }
    }

    fn recognize_end(
        self,
        _state: &mut N3RecognizerContext,
        _results: &mut Vec<Self::Output>,
        errors: &mut Vec<RuleRecognizerError>,
    ) {
        match &*self.stack {
            [] | [N3State::N3Doc] => (),
            _ => errors.push("Unexpected end".into()), // TODO
        }
    }

    fn lexer_options(context: &N3RecognizerContext) -> &N3LexerOptions {
        &context.lexer_options
    }
}

impl N3Recognizer {
    pub fn new_parser(
        unchecked: bool,
        base_iri: Option<Iri<String>>,
        prefixes: HashMap<String, Iri<String>>,
    ) -> Parser<Self> {
        Parser::new(
            Lexer::new(
                N3Lexer::new(N3LexerMode::N3, unchecked),
                MIN_BUFFER_SIZE,
                MAX_BUFFER_SIZE,
                true,
                Some(b"#"),
            ),
            Self {
                stack: vec![N3State::N3Doc],
                terms: Vec::new(),
                predicates: Vec::new(),
                contexts: Vec::new(),
            },
            N3RecognizerContext {
                lexer_options: N3LexerOptions { base_iri },
                prefixes,
            },
        )
    }

    #[must_use]
    fn error(
        mut self,
        errors: &mut Vec<RuleRecognizerError>,
        msg: impl Into<RuleRecognizerError>,
    ) -> Self {
        errors.push(msg.into());
        self.stack.clear();
        self
    }

    fn quad(
        &self,
        subject: impl Into<N3Term>,
        predicate: impl Into<N3Term>,
        object: impl Into<N3Term>,
    ) -> N3Quad {
        N3Quad {
            subject: subject.into(),
            predicate: predicate.into(),
            object: object.into(),
            graph_name: self
                .contexts
                .last()
                .map_or(GraphName::DefaultGraph, |g| g.clone().into()),
        }
    }
}

#[derive(Debug)]
enum N3State {
    N3Doc,
    N3DocExpectDot,
    BaseExpectIri,
    PrefixExpectPrefix,
    PrefixExpectIri { name: String },
    Triples,
    TriplesMiddle,
    TriplesEnd,
    PredicateObjectList,
    PredicateObjectListEnd,
    PredicateObjectListPossibleContinuation,
    ObjectsList,
    ObjectsListEnd,
    Verb,
    AfterRegularVerb,
    AfterInvertedVerb,
    AfterVerbIs,
    Path,
    PathFollowUp,
    PathAfterIndicator { is_inverse: bool },
    PathItem,
    PropertyListMiddle,
    PropertyListEnd,
    IriPropertyList,
    CollectionBeginning,
    CollectionPossibleEnd,
    LiteralPossibleSuffix { value: String },
    LiteralExpectDatatype { value: String },
    FormulaContent,
    FormulaContentExpectDot,
}

/// Iterator on the file prefixes.
///
/// See [`LowLevelN3Reader::prefixes`].
pub struct N3PrefixesIter<'a> {
    inner: Iter<'a, String, Iri<String>>,
}

impl<'a> Iterator for N3PrefixesIter<'a> {
    type Item = (&'a str, &'a str);

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        let (key, value) = self.inner.next()?;
        Some((key.as_str(), value.as_str()))
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}