From e3b90a78e7e85e186087487afc3b14c37bd4f302 Mon Sep 17 00:00:00 2001
From: Scott Richmond <kredati@users.noreply.github.com>
Date: Fri, 11 Jul 2025 15:07:38 -0400
Subject: [PATCH] allow squashing of lines

---
 pkg/p5.js              | 19 +++++++++++++++----
 pkg/turtle_geometry.js | 10 ++++++++--
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/pkg/p5.js b/pkg/p5.js
index e5eb4dd..8c92512 100644
--- a/pkg/p5.js
+++ b/pkg/p5.js
@@ -1,11 +1,22 @@
-import {eq_vect, eq_color, resolve_color, get_turtle_color, set_turtle_color, turtle_radius, turtle_angle, turn_to_rad, turtle_init, command_to_state, background_color, rotate, last} from "./turtle_geometry.js"
+import {eq_vect, eq_color, resolve_color, get_turtle_color, set_turtle_color, turtle_radius, turtle_angle, turn_to_rad, turtle_init, command_to_state, background_color, rotate, last, sub} from "./turtle_geometry.js"
 
-function states_to_call (prev, curr) {
+function states_to_call (prev, curr, call_stack) {
   // console.log(prev)
   // console.log(curr)
   let calls = []
   if (prev.pendown && !eq_vect(prev.position, curr.position)) {
-    calls.push(["line", prev.position[0], prev.position[1], curr.position[0], curr.position[1]])
+    console.log("headings", prev.heading, curr.heading)
+    console.log("forward?", curr.forward)
+    console.log("#calls", call_stack.length)
+    if (prev.heading == curr.heading && curr.forward && call_stack.length > 0) {
+      console.log("extending line!")
+      const [x, y] = sub(curr.position, prev.position)
+      const last_call = call_stack.pop();
+      const new_call = ["line", last_call[1], last_call[2], x + last_call[3], y + last_call[4]]   
+      calls.push(new_call)
+    } else {
+      calls.push(["line", prev.position[0], prev.position[1], curr.position[0], curr.position[1]])
+    }
   }
   if (!eq_color(curr.pencolor, prev.pencolor)) {
     calls.push(["stroke", ...resolve_color(curr.pencolor)])
@@ -80,7 +91,7 @@ export function p5 (commands) {
     for (let i = 1; i < states.length; ++i) {
       const prev = states[i - 1]
       const curr = states[i]
-      const calls = states_to_call(prev, curr)
+      const calls = states_to_call(prev, curr, my_calls)
       for (const call of calls) {
         // console.log(call)
         if (call === "clear") {
diff --git a/pkg/turtle_geometry.js b/pkg/turtle_geometry.js
index 0140f77..ec4461f 100644
--- a/pkg/turtle_geometry.js
+++ b/pkg/turtle_geometry.js
@@ -56,6 +56,12 @@ export function add (v1, v2) {
   return [x1 + x2, y1 + y2]
 }
 
+export function sub (v1, v2) {
+  const [x1, y1] = v1
+  const [x2, y2] = v2
+  return [x1 - x2, y1 - y2]
+}
+
 export function mult (vector, scalar) {
   const [x, y] = vector
   return [x * scalar, y * scalar]
@@ -92,14 +98,14 @@ export function command_to_state (prev_state, curr_command) {
       const {heading, position} = prev_state
       const unit = unit_of(heading)
       const move = mult(unit, steps)
-      return {...prev_state, position: add(position, move), clear: false}
+      return {...prev_state, position: add(position, move), clear: false, forward: true}
     }
     case "back": {
       const [_, steps] = curr_command
       const {heading, position} = prev_state
       const unit = unit_of(heading)
       const move = mult(unit, -steps)
-      return {...prev_state, position: add(position, move), clear: false}
+      return {...prev_state, position: add(position, move), clear: false, forward: false}
     }
     case "penup": {
       return {...prev_state, pendown: false, clear: false}