use text::{TextUnit, TextRange};
use syntax_kinds::syntax_info;

use std::fmt;

#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SyntaxKind(pub(crate) u32);

impl SyntaxKind {
    fn info(self) -> &'static SyntaxInfo {
        syntax_info(self)
    }
}

impl fmt::Debug for SyntaxKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let name = self.info().name;
        f.write_str(name)
    }
}


pub(crate) struct SyntaxInfo {
    pub name: &'static str,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Token {
    pub kind: SyntaxKind,
    pub len: TextUnit,
}

pub struct File {
	text: String,
	nodes: Vec<NodeData>,
}

impl File {
	pub fn root<'f>(&'f self) -> Node<'f> {
		assert!(!self.nodes.is_empty());
		Node { file: self, idx: NodeIdx(0) }
	}
}

#[derive(Clone, Copy)]
pub struct Node<'f> {
	file: &'f File,
	idx: NodeIdx,
}

impl<'f> Node<'f> {
	pub fn kind(&self) -> SyntaxKind {
		self.data().kind
	}

	pub fn text(&self) -> &'f str {
		let range = self.data().range;
		&self.file.text.as_str()[range]
	}

	pub fn parent(&self) -> Option<Node<'f>> {
		self.as_node(self.data().parent)
	}

	pub fn children(&self) -> Children<'f> {
		Children { next: self.as_node(self.data().first_child) }
	}

	fn data(&self) -> &'f NodeData {
		&self.file.nodes[self.idx.0 as usize]
	}

	fn as_node(&self, idx: Option<NodeIdx>) -> Option<Node<'f>> {
		idx.map(|idx| Node { file: self.file, idx })
	}
}

pub struct Children<'f> {
	next: Option<Node<'f>>,
}

impl<'f> Iterator for Children<'f> {
	type Item = Node<'f>;

	fn next(&mut self) -> Option<Node<'f>> {
		let next = self.next;
		self.next = next.and_then(|node| node.as_node(node.data().next_sibling));
		next
	}
}

#[derive(Clone, Copy)]
struct NodeIdx(u32);

struct NodeData {
	kind: SyntaxKind,
	range: TextRange,
	parent: Option<NodeIdx>,
	first_child: Option<NodeIdx>,
	next_sibling: Option<NodeIdx>,
}