use std::fmt;

/// Is a rule a basic rule or an incremental alternative?
/// See https://tools.ietf.org/html/rfc5234#section-3.3
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub enum Definition {
    /// Basic Rule Definition
    Basic,
    /// Incremental Alternative
    Incremental,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Rule {
    name: String,
    node: Node,
    definition: Definition,
}

impl Rule {
    pub fn new(name: &str, node: Node) -> Rule {
        Rule {
            name: name.into(),
            node,
            definition: Definition::Basic,
        }
    }

    pub fn definition(mut self, definition: Definition) -> Self {
        self.definition = definition;
        self
    }

    pub fn get_name(&self) -> &str {
        &self.name
    }

    pub fn get_node(&self) -> &Node {
        &self.node
    }

    pub fn get_definition(&self) -> Definition {
        self.definition
    }
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Node {
    Alternation(Vec<Node>),
    Concatenation(Vec<Node>),
    Repetition(Repetition),
    Rulename(String),
    Group(Box<Node>),
    Optional(Box<Node>),
    CharVal(String),
    NumVal(Range),
    ProseVal(String),
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Repetition {
    repeat: Repeat,
    node: Box<Node>,
}

impl Repetition {
    pub fn new(repeat: Repeat, node: Node) -> Self {
        Self {
            repeat,
            node: Box::new(node),
        }
    }

    pub fn get_repeat(&self) -> &Repeat {
        &self.repeat
    }

    pub fn get_node(&self) -> &Node {
        &self.node
    }
}

#[derive(Debug, Clone, Eq, PartialEq, Default)]
pub struct Repeat {
    min: Option<usize>,
    max: Option<usize>,
}

impl Repeat {
    pub fn new() -> Self {
        Self {
            min: None,
            max: None,
        }
    }

    pub fn with(min: Option<usize>, max: Option<usize>) -> Self {
        Self { min, max }
    }

    pub fn get_min(&self) -> Option<usize> {
        self.min
    }

    pub fn get_max(&self) -> Option<usize> {
        self.max
    }

    pub fn get_min_max(&self) -> (Option<usize>, Option<usize>) {
        (self.min, self.max)
    }
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Range {
    OneOf(Vec<u32>), // FIXME: out of spec, but useful?
    Range(u32, u32),
}

impl fmt::Display for Rule {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.name)?;
        match self.definition {
            Definition::Basic => write!(f, " = ")?,
            Definition::Incremental => write!(f, " =/ ")?,
        }
        write!(f, "{}", self.node)
    }
}

impl fmt::Display for Node {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Node::Alternation(nodes) => {
                if let Some((last, elements)) = nodes.split_last() {
                    for item in elements {
                        write!(f, "{} / ", item)?;
                    }
                    write!(f, "{}", last)?;
                }
            }
            Node::Concatenation(nodes) => {
                if let Some((last, elements)) = nodes.split_last() {
                    for item in elements {
                        write!(f, "{} ", item)?;
                    }
                    write!(f, "{}", last)?;
                }
            }
            Node::Repetition(Repetition { repeat, node }) => {
                if let Some(min) = repeat.min {
                    write!(f, "{}", min)?;
                }

                write!(f, "*")?;

                if let Some(max) = repeat.max {
                    write!(f, "{}", max)?;
                }

                write!(f, "{}", node)?;
            }
            Node::Rulename(name) => {
                write!(f, "{}", name)?;
            }
            Node::Group(node) => {
                write!(f, "({})", node)?;
            }
            Node::Optional(node) => {
                write!(f, "[{}]", node)?;
            }
            Node::CharVal(str) => {
                write!(f, "\"{}\"", str)?;
            }
            Node::NumVal(range) => {
                write!(f, "%x")?;
                match range {
                    Range::OneOf(allowed) => {
                        if let Some((last, elements)) = allowed.split_last() {
                            for item in elements {
                                write!(f, "{:02X}.", item)?;
                            }
                            write!(f, "{:02X}", last)?;
                        }
                    }
                    Range::Range(from, to) => {
                        write!(f, "{:02X}-{:02X}", from, to)?;
                    }
                }
            }
            Node::ProseVal(str) => {
                write!(f, "<{}>", str)?;
            }
        }

        Ok(())
    }
}

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

    #[test]
    fn test_display_rule() {
        let test = Rule::new("rule", Node::Rulename("A".into()));
        let expected = "rule = A";
        let got = test.to_string();
        assert_eq!(expected, got);

        let test =
            Rule::new("rule", Node::Rulename("A".into())).definition(Definition::Incremental);
        let expected = "rule =/ A";
        let got = test.to_string();
        assert_eq!(expected, got);
    }

    #[test]
    fn test_display_prose() {
        let rule = Rule::new("rule", Node::ProseVal("test".into()));
        assert_eq!("rule = <test>", rule.to_string());
    }

    #[test]
    fn test_impl_trait() {
        // Make sure that others can implement their own traits for Rule.
        trait Foo {
            fn foo(&self);
        }

        impl Foo for Rule {
            fn foo(&self) {
                println!("{}", self.name);
            }
        }
    }
}