use {SyntaxKind, TextRange, TextUnit};
use super::{File, NodeData, NodeIdx, SyntaxErrorData};

pub trait Sink {
    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit);
    fn start_internal(&mut self, kind: SyntaxKind);
    fn finish_internal(&mut self);
    fn error(&mut self) -> ErrorBuilder;
}

pub struct FileBuilder {
    text: String,
    nodes: Vec<NodeData>,
    errors: Vec<SyntaxErrorData>,
    in_progress: Vec<(NodeIdx, Option<NodeIdx>)>, // (parent, last_child)
    pos: TextUnit,
}

impl Sink for FileBuilder {
    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit) {
        let leaf = NodeData {
            kind,
            range: TextRange::from_len(self.pos, len),
            parent: None,
            first_child: None,
            next_sibling: None,
        };
        self.pos += len;
        let id = self.push_child(leaf);
        self.add_len(id);
    }

    fn start_internal(&mut self, kind: SyntaxKind) {
        let node = NodeData {
            kind,
            range: TextRange::from_len(self.pos, 0.into()),
            parent: None,
            first_child: None,
            next_sibling: None,
        };
        let id = if self.in_progress.is_empty() {
            self.new_node(node)
        } else {
            self.push_child(node)
        };
        self.in_progress.push((id, None))
    }

    fn finish_internal(&mut self) {
        let (id, _) = self.in_progress
            .pop()
            .expect("trying to complete a node, but there are no in-progress nodes");
        if !self.in_progress.is_empty() {
            self.add_len(id);
        }
    }

    fn error(&mut self) -> ErrorBuilder {
        ErrorBuilder::new(self)
    }
}

impl FileBuilder {
    pub fn new(text: String) -> FileBuilder {
        FileBuilder {
            text,
            nodes: Vec::new(),
            errors: Vec::new(),
            in_progress: Vec::new(),
            pos: TextUnit::new(0),
        }
    }

    pub fn finish(self) -> File {
        assert!(
            self.in_progress.is_empty(),
            "some nodes in FileBuilder are unfinished: {:?}",
            self.in_progress
                .iter()
                .map(|&(idx, _)| self.nodes[idx].kind)
                .collect::<Vec<_>>()
        );
        assert_eq!(
            self.pos,
            (self.text.len() as u32).into(),
            "nodes in FileBuilder do not cover the whole file"
        );
        File {
            text: self.text,
            nodes: self.nodes,
            errors: self.errors,
        }
    }

    fn new_node(&mut self, data: NodeData) -> NodeIdx {
        let id = NodeIdx(self.nodes.len() as u32);
        self.nodes.push(data);
        id
    }

    fn push_child(&mut self, mut child: NodeData) -> NodeIdx {
        child.parent = Some(self.current_id());
        let id = self.new_node(child);
        {
            let (parent, sibling) = *self.in_progress.last().unwrap();
            let slot = if let Some(idx) = sibling {
                &mut self.nodes[idx].next_sibling
            } else {
                &mut self.nodes[parent].first_child
            };
            fill(slot, id);
        }
        self.in_progress.last_mut().unwrap().1 = Some(id);
        id
    }

    fn add_len(&mut self, child: NodeIdx) {
        let range = self.nodes[child].range;
        grow(&mut self.current_parent().range, range);
    }

    fn current_id(&self) -> NodeIdx {
        self.in_progress.last().unwrap().0
    }

    fn current_parent(&mut self) -> &mut NodeData {
        let idx = self.current_id();
        &mut self.nodes[idx]
    }
}

fn fill<T>(slot: &mut Option<T>, value: T) {
    assert!(slot.is_none());
    *slot = Some(value);
}

fn grow(left: &mut TextRange, right: TextRange) {
    assert_eq!(left.end(), right.start());
    *left = TextRange::from_to(left.start(), right.end())
}

pub struct ErrorBuilder<'f> {
    message: Option<String>,
    builder: &'f mut FileBuilder,
}

impl<'f> ErrorBuilder<'f> {
    fn new(builder: &'f mut FileBuilder) -> Self {
        ErrorBuilder {
            message: None,
            builder,
        }
    }

    pub fn message<M: Into<String>>(mut self, m: M) -> Self {
        self.message = Some(m.into());
        self
    }

    pub fn emit(self) {
        let message = self.message.expect("Error message not set");
        let &(node, after_child) = self.builder.in_progress.last().unwrap();
        self.builder.errors.push(SyntaxErrorData {
            node,
            message,
            after_child,
        })
    }
}