From d603a9140d0195659c795bc6c19634e370c84cd8 Mon Sep 17 00:00:00 2001
From: Georg Hopp <georg@steffers.org>
Date: Wed, 8 Jan 2020 00:17:57 +0100
Subject: [PATCH] more iterators

---
 fractional/src/easel.rs | 82 +++++++++++++++++++++++++++++------------
 1 file changed, 59 insertions(+), 23 deletions(-)

diff --git a/fractional/src/easel.rs b/fractional/src/easel.rs
index 85a8e34..504cf64 100644
--- a/fractional/src/easel.rs
+++ b/fractional/src/easel.rs
@@ -56,7 +56,7 @@ pub struct Coordinate<T>(pub i32, pub i32, pub T);
 #[derive(Debug, Clone)]
 pub struct Coordinates<T>(pub Vec<Coordinate<T>>);
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Copy)]
 pub struct LineIterator<T> where T: Debug {
                a :Option<Coordinate<T>>
     ,          b :Coordinate<T>
@@ -74,6 +74,7 @@ where T: Add<Output = T> + Debug + Copy + From<i32> {
     type Item = Coordinate<T>;
 
     fn next(&mut self) -> Option<Self::Item> {
+        println!("== LineIterator next: {:?}", self);
         match self.a {
             None    => None,
             Some(a) => {
@@ -263,37 +264,70 @@ pub struct VertexIterator<'a,T> where T: Debug {
     p         :&'a Polygon<T>,
     top       :usize,
     current   :Option<usize>,
-    inner     :Option<LineIterator<T>>,
+    edge      :Option<LineIterator<T>>,
     direction :Direction,
 }
 
+impl<'a,T> VertexIterator<'a,T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Copy + From<i32> {
+
+    fn new(p :&'a Polygon<T>, direction :Direction) -> Self {
+        let mut v = VertexIterator { p:         p
+                                   , top:       p.vert_min()
+                                   , current:   Some(p.vert_min())
+                                   , edge:      None
+                                   , direction: direction };
+        v.next_edge();
+        println!("== new: {:?}", v);
+        v
+    }
+
+    // if this yields "None" we are finished.
+    fn next_edge(&mut self) -> Option<LineIterator<T>> {
+        let current  = self.current?;
+        let next     = self.p.next_y(current, self.direction)?;
+        let mut edge = self.p.vertex(current).edge_iter(&self.p.vertex(next));
+
+        println!("== next: {:?} {:?} {:?}", current, next, edge);
+
+        match edge.next() {
+            // It should be impossible that a new edge iterator has no values
+            // at all… anyway, just in case I handle it here.
+            None    => self.next_edge(),
+            Some(_) => {
+                self.current = Some(next);
+                self.edge    = Some(edge);
+                self.edge
+            },
+        }
+    }
+}
+
 impl<'a,T> Iterator for VertexIterator<'a,T>
 where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
        + Debug + Copy + From<i32> {
     type Item = Coordinate<T>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let inner = match self.inner {
-            Some(i) => i,
-            None    => {
-                let current = self.current?;
-                let next    = self.p.next_y(current, self.direction)?;
-                self.p.vertex(current).edge_iter(&self.p.vertex(next))
-            },
-        }
+        // if for whatever reason edge is "None" finish this iterator.
+        let next = self.edge?.next();
 
-        match self.current {
-            None    => None,
-            Some(c) => {
-                let r        = self.p.vertex(c);
-                self.current = self.p.next_y(c, self.direction);
-                Some(r)
+        println!("== next: {:?}", next);
+
+        match next {
+            Some(_) => next,
+            None    => {
+                self.next_edge()?;
+                self.next()
             },
         }
     }
 }
 
-impl<T> Polygon<T> where T: Copy + Debug {
+impl<T> Polygon<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Copy + Debug + From<i32> {
     fn vert_min<'a>(&'a self) -> usize {
         let Polygon(Coordinates(cs)) = self;
 
@@ -313,11 +347,7 @@ impl<T> Polygon<T> where T: Copy + Debug {
     }
 
     fn left_vertices(&self) -> VertexIterator<T> {
-        VertexIterator { p:         &self
-                       , top:       self.vert_min()
-                       , current:   Some(self.vert_min())
-                       , inner:     None
-                       , direction: Direction::Left }
+        VertexIterator::new(self, Direction::Left)
     }
 
     fn left(&self, v :usize) -> usize {
@@ -353,7 +383,8 @@ impl<T> Polygon<T> where T: Copy + Debug {
                    , c :usize
                    , n :usize
                    , d :Direction) -> Option<usize>
-        where T: Copy + Debug {
+        where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+               + Copy + Debug + From<i32> {
             if c == n {
                 None
             } else {
@@ -362,6 +393,8 @@ impl<T> Polygon<T> where T: Copy + Debug {
 
                 match ny.cmp(&cy) {
                     cmp::Ordering::Less    => None,
+                    // TODO On equal we need to find out which one of both to
+                    //      keep in the list… (the outermost)
                     cmp::Ordering::Equal   => inner(p, c, p.step(n, d), d),
                     cmp::Ordering::Greater => Some(n),
                 }
@@ -446,7 +479,10 @@ where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
             r = append_edge(&mut r_edge, r, Direction::Right);
         }
 
+        let l_edge2 :Vec<Coordinate<T>> = self.left_vertices().collect();
+
         println!("== [{}] {:?}", l_edge.len(), l_edge);
+        println!("== [{}] {:?}", l_edge2.len(), l_edge2);
         println!("== [{}] {:?}", r_edge.len(), r_edge);
 
         // TODO we always miss the last scanline…