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use std::collections::BTreeMap;
use std::ops::{Index, IndexMut};
use std::cmp::min;
use crate::graph::{Graph, Node, NodeId};
#[derive(Debug)]
pub struct Meta {
map: BTreeMap<NodeId, MetaItem>,
}
#[derive(Debug, Default)]
pub struct MetaItem {
pub refcount: usize,
pub min_read: usize,
pub is_loop_init: bool,
pub loop_entry_from: Vec<NodeId>,
}
impl Index<NodeId> for Meta {
type Output = MetaItem;
fn index(&self, id: NodeId) -> &MetaItem {
&self.map[&id]
}
}
impl IndexMut<NodeId> for Meta {
fn index_mut(&mut self, id: NodeId) -> &mut MetaItem {
self.map.entry(id).or_default()
}
}
impl MetaItem {
fn loop_entry(&mut self, id: NodeId) {
if let Err(idx) = self.loop_entry_from.binary_search(&id) {
self.loop_entry_from.insert(idx, id);
}
}
}
impl Meta {
pub fn analyze<T>(root: NodeId, graph: &Graph<T>) -> Self {
let mut meta = Meta {
map: Default::default(),
};
meta.first_pass(root, root, graph, &mut Vec::new());
meta
}
pub fn first_pass<T>(
&mut self,
this: NodeId,
parent: NodeId,
graph: &Graph<T>,
stack: &mut Vec<NodeId>,
) -> &MetaItem {
let meta = &mut self[this];
let is_done = meta.refcount > 0;
meta.refcount += 1;
if stack.contains(&this) {
meta.loop_entry(parent);
self[parent].is_loop_init = true;
}
if is_done {
return &self[this];
}
stack.push(this);
let mut min_read;
match &graph[this] {
Node::Fork(fork) => {
min_read = usize::max_value();
for (_, id) in fork.branches() {
let meta = self.first_pass(id, this, graph, stack);
if meta.is_loop_init {
min_read = 1;
} else {
min_read = min(min_read, meta.min_read + 1);
}
}
if let Some(id) = fork.miss {
let meta = self.first_pass(id, this, graph, stack);
if meta.is_loop_init {
min_read = 0;
} else {
min_read = min(min_read, meta.min_read);
}
}
if min_read == usize::max_value() {
min_read = 0;
}
},
Node::Rope(rope) => {
min_read = rope.pattern.len();
let meta = self.first_pass(rope.then, this, graph, stack);
if !meta.is_loop_init {
min_read += meta.min_read;
}
if let Some(id) = rope.miss.first() {
let meta = self.first_pass(id, this, graph, stack);
if meta.is_loop_init {
min_read = 0;
} else {
min_read = min(min_read, meta.min_read);
}
}
},
Node::Leaf(_) => min_read = 0,
}
stack.pop();
let meta = &mut self[this];
meta.min_read = min_read;
let second_pass = meta.loop_entry_from.clone();
for id in second_pass {
self.meta_second_pass(id, graph);
}
&self[this]
}
fn meta_second_pass<T>(&mut self, id: NodeId, graph: &Graph<T>) {
let mut min_read;
match &graph[id] {
Node::Fork(fork) => {
min_read = usize::max_value();
for (_, id) in fork.branches() {
let meta = &self[id];
if meta.is_loop_init {
min_read = 1;
} else {
min_read = min(min_read, meta.min_read + 1);
}
}
if min_read == usize::max_value() {
min_read = 0;
}
},
Node::Rope(rope) => {
min_read = rope.pattern.len();
let meta = &self[rope.then];
if !meta.is_loop_init {
min_read += meta.min_read;
}
},
Node::Leaf(_) => unreachable!(),
}
self[id].min_read = min_read;
}
}