From 106290fcbdb78d08af4437eed3548ad59e3cc306 Mon Sep 17 00:00:00 2001
From: Johannes Wolf <mail@johannes-wolf.com>
Date: Sun, 7 Apr 2024 17:37:58 +0200
Subject: [PATCH] WOP

---
 apps/find_plane.lua | 52 +++++++++++++++++++++++++++++++++++++++++++++
 apps/init.lua       |  2 ++
 2 files changed, 54 insertions(+)
 create mode 100644 apps/find_plane.lua

diff --git a/apps/find_plane.lua b/apps/find_plane.lua
new file mode 100644
index 0000000..52725f7
--- /dev/null
+++ b/apps/find_plane.lua
@@ -0,0 +1,52 @@
+local apps       = require 'apps.apps'
+local ask        = require('dialog.input').display_sync
+local choice     = require('dialog.choice').display_sync
+local expr       = require 'expressiontree'
+
+local function table_to_vec(t)
+   local r = ""
+   for _, v in ipairs(t) do
+      r = r .. "[" .. v .. "]"
+   end
+   return "[" .. r .. "]"
+end
+
+local function ask_vector(title, dim)
+   dim = dim or 3
+   while true do
+      local r = ask({title = title or 'Vector'})
+      if not r then
+         return nil
+      end
+
+      local v = {}
+      for c in r:gmatch("([^,]+)") do
+         table.insert(v, c)
+      end
+
+      if #v == dim then
+         return v
+      end
+   end
+end
+
+local function run_plane_3pt(stack)
+   local pts = {}
+   for i = 1, 3 do
+      local pt = ask_vector("Point " .. tostring(i))
+      if not pt then
+         return
+      end
+      table.insert(pts, pt)
+   end
+
+   local a, b, c = pts[1], pts[2], pts[3]
+   local ab = math.evalStr(table_to_vec(a) .. "-" .. table_to_vec(b))
+   local ac = math.evalStr(table_to_vec(a) .. "-" .. table_to_vec(c))
+   local n = math.evalStr("crossp(" .. ab .. "," .. ac .. ")")
+   local eq = math.evalStr("dotp(" ..n .. "," .. table_to_vec({"x", "y", "z"}) .. ")")
+   local d = math.evalStr(string.format(eq .."|(x=%s and y=%s and z=%s)", a[1], a[2], a[3]))
+   stack:push_infix(eq .. "=" .. d)
+end
+
+apps.add('plane - 3pt', 'Plane - 3 Points', run_plane_3pt)
diff --git a/apps/init.lua b/apps/init.lua
index 896004c..e1626e5 100644
--- a/apps/init.lua
+++ b/apps/init.lua
@@ -4,3 +4,5 @@ require 'apps.app_punktsteigung'
 require 'apps.app_triangle'
 require 'apps.app_constants'
 require 'apps.app_analyze_fn'
+
+require 'apps.find_plane'