From 3764afbf1e86a5d041b9307b56223576b190f9f3 Mon Sep 17 00:00:00 2001
From: Sergio Benitez <sbenitez@mit.edu>
Date: Fri, 18 Mar 2016 19:05:29 -0700
Subject: [PATCH] Cleaned up routing code. It's nearing completion!

* Should be able to write a simple O(n) router using the collision functions.
* Still need to split things up into multiple files.
---
 lib/src/lib.rs    |   8 +-
 lib/src/router.rs | 253 ++++++++++++++++++++++++++++++++++++----------
 2 files changed, 208 insertions(+), 53 deletions(-)

diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index d11135df..5eb7de4d 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -1,3 +1,5 @@
+#![feature(str_char)]
+
 extern crate hyper;
 
 pub mod method;
@@ -59,7 +61,8 @@ impl Rocket {
         }
     }
 
-    pub fn mount(&mut self, base: &str, routes: &[&Route<'static>]) -> &mut Self {
+    pub fn mount(&mut self, base: &'static str, routes: &[&Route<'static>])
+            -> &mut Self {
         println!("🛰 Mounting '{}':", base);
         for route in routes {
             if self.handler.is_none() {
@@ -74,7 +77,8 @@ impl Rocket {
         self
     }
 
-    pub fn mount_and_launch(mut self, base: &str, routes: &[&Route<'static>]) {
+    pub fn mount_and_launch(mut self, base: &'static str,
+                            routes: &[&Route<'static>]) {
         self.mount(base, routes);
         self.launch();
     }
diff --git a/lib/src/router.rs b/lib/src/router.rs
index f017eb70..b49fd186 100644
--- a/lib/src/router.rs
+++ b/lib/src/router.rs
@@ -1,51 +1,85 @@
 use method::Method;
-use std::path::{Path, PathBuf, Component};
+use std::path::{PathBuf, Component};
 use std::collections::hash_map::HashMap;
 
+// FIXME: Split this up into multiple files: Collider, Route, Router, etc.
+
+// FIXME: Implement the following:
+// Collider<Route> for &str;
+trait Collider<T = Self> {
+    fn collides_with(&self, other: &T) -> bool;
+}
+
+macro_rules! comp_to_str {
+    ($component:expr) => (
+        match $component {
+            &Component::Normal(ref comp) => {
+                if let Some(string) = comp.to_str() { string }
+                else { return true }
+            },
+            _ => return true
+        };
+    )
+}
+
+fn check_match_until(c: char, a: &str, b: &str, dir: bool) -> bool {
+    let (a_len, b_len) = (a.len() as isize, b.len() as isize);
+    let (mut i, mut j, delta) = if dir {
+        (0, 0, 1)
+    } else {
+        (a_len - 1, b_len - 1, -1)
+    };
+
+    while i >= 0 && j >= 0 && i < a_len && j < b_len {
+        let (c1, c2) = (a.char_at(i as usize), b.char_at(j as usize));
+        if c1 == c || c2 == c {
+            break;
+        } else if c1 != c2 {
+            return false;
+        } else {
+            i += delta;
+            j += delta;
+        }
+    }
+
+    return true;
+}
+
+impl<'a> Collider for Component<'a> {
+    fn collides_with(&self, other: &Component<'a>) -> bool {
+        let (a, b) = (comp_to_str!(self), comp_to_str!(other));
+        check_match_until('<', a, b, true) && check_match_until('>', a, b, false)
+    }
+}
+
+#[derive(Debug)]
+struct Route {
+    method: Method,
+    mount: &'static str,
+    route: &'static str,
+    n_components: usize,
+    path: PathBuf
+}
+
 pub struct Router {
-    paths: Vec<PathBuf> // for now, to check for collisions
+    routes: Vec<Route> // for now, to check for collisions
 }
 
-fn is_variadic(c: &Component) -> bool {
-    match c {
-        &Component::Normal(ref comp) => comp.to_str().unwrap().starts_with("<"),
-        _ => false
-    }
-}
+impl Route {
+    fn new(m: Method, mount: &'static str, route: &'static str) -> Route {
+        let deduped_path = Route::dedup(mount, route);
+        let path = PathBuf::from(deduped_path);
 
-#[inline]
-fn routes_collide(n: usize, a: &Path, b: &Path) -> bool {
-    let mut matches = 0;
-
-    let mut a_components = a.components();
-    let mut b_components = b.components();
-
-    while let Some(ref c1) = a_components.next() {
-        if let Some(ref c2) = b_components.next() {
-            if c1 == c2 {
-                matches += 1;
-            } else if is_variadic(c1) || is_variadic(c2) {
-                matches += 1;
-            }
+        Route {
+            method: m,
+            mount: mount,
+            route: route,
+            n_components: path.components().count(),
+            path: path
         }
     }
 
-    // println!("Checked {:?} against {:?}: {}/{}", a, b, matches, n);
-    matches == n
-}
-
-// TODO: Are /hello and /hello/ the same? Or not? Currently, they're treated as
-// such by Path, which is passed on to the collisions stuff.
-impl Router {
-    pub fn new() -> Router {
-        Router {
-            paths: Vec::new()
-        }
-    }
-
-    // TODO: Use `method` argument
-    pub fn add_route(&mut self, _method: Method, base: &str, route: &str) {
-        // Allocate enough space for the worst case.
+    fn dedup(base: &'static str, route: &'static str) -> String {
         let mut deduped = String::with_capacity(base.len() + route.len() + 1);
 
         let mut last = '\0';
@@ -57,18 +91,54 @@ impl Router {
             last = c;
         }
 
-        let path = PathBuf::from(deduped);
-        println!("Mounted: {:?}", path);
-        self.paths.push(path);
+        deduped
+    }
+}
+
+impl Collider for Route {
+    fn collides_with(&self, b: &Route) -> bool {
+        if self.n_components != b.n_components || self.method != b.method {
+            return false;
+        }
+
+        let mut matches = 0;
+        let mut a_components = self.path.components();
+        let mut b_components = b.path.components();
+        while let Some(ref c1) = a_components.next() {
+            if let Some(ref c2) = b_components.next() {
+                if c1.collides_with(c2) {
+                    matches += 1;
+                }
+            }
+        }
+
+        // println!("Checked {:?} against {:?}: {}/{}", a, b, matches, n);
+        matches == self.n_components
+    }
+}
+
+// TODO: Are /hello and /hello/ the same? Or not? Currently, they're treated as
+// such by Path, which is passed on to the collisions stuff.
+impl Router {
+    pub fn new() -> Router {
+        Router {
+            routes: Vec::new()
+        }
+    }
+
+    // TODO: Use `method` argument
+    pub fn add_route(&mut self, method: Method, base: &'static str,
+                     route: &'static str) {
+        let route = Route::new(method, base, route);
+        println!("Mounted: {:?}", route);
+        self.routes.push(route);
     }
 
     pub fn has_collisions(&self) -> bool {
-        let mut map: HashMap<usize, Vec<&Path>> = HashMap::new();
-
-        for route in &self.paths {
-            let num_components = route.components().count();
-            println!("Found {} for {:?}", num_components, route);
+        let mut map: HashMap<usize, Vec<&Route>> = HashMap::new();
 
+        for route in &self.routes {
+            let num_components = route.path.components().count();
             let mut list = if map.contains_key(&num_components) {
                 map.get_mut(&num_components).unwrap()
             } else {
@@ -76,18 +146,17 @@ impl Router {
                 map.get_mut(&num_components).unwrap()
             };
 
-            list.push(route.as_path());
+            list.push(&route);
         }
 
         let mut result = false;
-        for (num_components, routes) in map.iter() {
+        for (_, routes) in map {
             for i in 0..routes.len() {
                 for j in 0..routes.len() {
                     if i == j { continue }
 
-                    let a_route = &routes[i];
-                    let b_route = &routes[j];
-                    if routes_collide(*num_components, a_route, b_route) {
+                    let (a_route, b_route) = (&routes[i], &routes[j]);
+                    if a_route.collides_with(b_route) {
                         result = true;
                         println!("{:?} and {:?} collide!", a_route, b_route);
                     }
@@ -98,3 +167,85 @@ impl Router {
         result
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{Route, Collider};
+    use Method;
+    use Method::*;
+
+    fn m_collide(a: (Method, &'static str), b: (Method, &'static str)) -> bool {
+        let route_a = Route::new(a.0, "/", a.1);
+        route_a.collides_with(&Route::new(b.0, "/", b.1))
+    }
+
+    fn collide(a: &'static str, b: &'static str) -> bool {
+        let route_a = Route::new(Get, "/", a);
+        route_a.collides_with(&Route::new(Get, "/", b))
+    }
+
+    #[test]
+    fn simple_collisions() {
+        assert!(collide("a", "a"));
+        assert!(collide("/a", "/a"));
+        assert!(collide("/hello", "/hello"));
+        assert!(collide("/hello", "/hello/"));
+        assert!(collide("/hello/there/how/ar", "/hello/there/how/ar"));
+        assert!(collide("/hello/there", "/hello/there/"));
+    }
+
+    #[test]
+    fn simple_param_collisions() {
+        assert!(collide("/hello/<name>", "/hello/<person>"));
+        assert!(collide("/hello/<name>/hi", "/hello/<person>/hi"));
+        assert!(collide("/hello/<name>/hi/there", "/hello/<person>/hi/there"));
+        assert!(collide("/<name>/hi/there", "/<person>/hi/there"));
+        assert!(collide("/<name>/hi/there", "/dude/<name>/there"));
+        assert!(collide("/<name>/<a>/<b>", "/<a>/<b>/<c>"));
+        assert!(collide("/<name>/<a>/<b>/", "/<a>/<b>/<c>/"));
+    }
+
+    #[test]
+    fn medium_param_collisions() {
+        assert!(collide("/hello/<name>", "/hello/bob"));
+        assert!(collide("/<name>", "//bob"));
+    }
+
+    #[test]
+    fn hard_param_collisions() {
+        assert!(collide("/<name>bob", "/<name>b"));
+        assert!(collide("/a<b>c", "/abc"));
+        assert!(collide("/a<b>c", "/azooc"));
+        assert!(collide("/a<b>", "/a"));
+        assert!(collide("/<b>", "/a"));
+        assert!(collide("/<a>/<b>", "/a/b<c>"));
+        assert!(collide("/<a>/bc<b>", "/a/b<c>"));
+        assert!(collide("/<a>/bc<b>d", "/a/b<c>"));
+    }
+
+    #[test]
+    fn non_collisions() {
+        assert!(!collide("/a", "/b"));
+        assert!(!collide("/a/b", "/a"));
+        assert!(!collide("/a/b", "/a/c"));
+        assert!(!collide("/a/hello", "/a/c"));
+        assert!(!collide("/hello", "/a/c"));
+        assert!(!collide("/hello/there", "/hello/there/guy"));
+        assert!(!collide("/b<a>/there", "/hi/there"));
+        assert!(!collide("/<a>/<b>c", "/hi/person"));
+        assert!(!collide("/<a>/<b>cd", "/hi/<a>e"));
+        assert!(!collide("/a<a>/<b>", "/b<b>/<a>"));
+        assert!(!collide("/a/<b>", "/b/<b>"));
+        assert!(!collide("/a<a>/<b>", "/b/<b>"));
+    }
+
+    #[test]
+    fn method_dependent_non_collisions() {
+        assert!(!m_collide((Get, "/"), (Post, "/")));
+        assert!(!m_collide((Post, "/"), (Put, "/")));
+        assert!(!m_collide((Put, "/a"), (Put, "/")));
+        assert!(!m_collide((Post, "/a"), (Put, "/")));
+        assert!(!m_collide((Get, "/a"), (Put, "/")));
+        assert!(!m_collide((Get, "/hello"), (Put, "/hello")));
+    }
+}