From 9a08a42fb5f28cafc4fc73688f8a54a02ae1a5b6 Mon Sep 17 00:00:00 2001
From: robin <comfysagedev@gmail.com>
Date: Tue, 5 May 2026 10:10:20 +0200
Subject: [PATCH] refactor: separate smoothing fn and scroll fn

---
 plugin/smoothie.lua | 111 ++++++++++++++++++++++++--------------------
 1 file changed, 61 insertions(+), 50 deletions(-)

diff --git a/plugin/smoothie.lua b/plugin/smoothie.lua
index 6e44e89..304a9c6 100644
--- a/plugin/smoothie.lua
+++ b/plugin/smoothie.lua
@@ -17,54 +17,15 @@ local opts = vim.defaulttable(function(key)
   return opt(defaults[key], key)
 end)
 
-local active = false
+local M, H = {}, {}
 
----@param min number
----@param n number
----@param max number
----@return number
-local function clamp(min, n, max)
-  return math.max(min, math.min(n, max))
-end
-
----@param n number
----@param t number
----@return number
-local function coillerp(n, t)
-  t = clamp(0, t, 1)
-  return (math.log(1 + t) * 1 + math.log(1 + t)) * n
-end
-
-local function scroll(vcount)
-  local win = vim.api.nvim_get_current_win()
-  -- distance to scroll
-  local d = vim.api.nvim_get_option_value("scroll", { scope = "local", win = win })
-
-  local m = vcount / math.abs(vcount)
-
-  local function step(start, dst, t)
-    local diff = dst.row - start.row
-
-    -- reached dst or overshot
-    -- - diff == 0: no more distance to travel
-    -- - diff * m: both need to be oriented in the same direction (positive product)
-    if diff == 0 or diff * m < 0 then
-      return true
-    end
-
-    -- travel t of the current diff (ceiled), at least 1
-    local s = m * math.max(1, math.ceil(coillerp(math.abs(diff), t)))
-    start.row = start.row + s
-
-    vim._with({ win = win }, function()
-      vim.fn.setpos(".", { start.buf, start.row + 1, start.col, 0 })
-    end)
-  end
+local active = false
 
+function M.smooth(win, step, init)
   -- on resume, returns whether still active
-  local repeater = coroutine.wrap(function(...)
+  local repeater = coroutine.wrap(function(delta, ...)
     while true do
-      if step(...) then
+      if step(delta, ...) then
         break
       end
       coroutine.yield(true)
@@ -80,9 +41,7 @@ local function scroll(vcount)
     end
 
     active = true
-    local buf, lnum, col = unpack(vim.fn.getpos("."))
-    local start = vim.pos.cursor(buf, { lnum, col })
-    local dst = vim.pos.cursor(buf, { math.max(0, lnum + (vcount * d)), col })
+    local args = init()
 
     local now = vim.uv.now()
 
@@ -90,7 +49,7 @@ local function scroll(vcount)
       local rel = vim.uv.now() - now
       local done = -1
       vim.defer_fn(function()
-        done = repeater(start, dst, rel / opts.maxtime)
+        done = repeater(rel / opts.maxtime, unpack(args))
       end, opts.interval)
       if not vim.wait(1000, function()
         return done ~= -1
@@ -103,13 +62,65 @@ local function scroll(vcount)
   end)()
 end
 
+function M.scroll(vcount)
+  local win = vim.api.nvim_get_current_win()
+  -- distance to scroll
+  local d = vim.api.nvim_get_option_value("scroll", { scope = "local", win = win })
+
+  local m = vcount / math.abs(vcount)
+
+  local function step(delta, start, dst)
+    local diff = dst.row - start.row
+
+    -- reached dst or overshot
+    -- - diff == 0: no more distance to travel
+    -- - diff * m: both need to be oriented in the same direction (positive product)
+    if diff == 0 or diff * m < 0 then
+      return true
+    end
+
+    -- travel t of the current diff (ceiled), at least 1
+    local s = m * math.max(1, math.ceil(H.coillerp(math.abs(diff), delta)))
+    start.row = start.row + s
+
+    vim._with({ win = win }, function()
+      vim.fn.setpos(".", { start.buf, start.row + 1, start.col, 0 })
+    end)
+  end
+
+  M.smooth(win, step, function()
+    local buf, lnum, col = unpack(vim.fn.getpos("."))
+    local start = vim.pos.cursor(buf, { lnum, col })
+    local dst = vim.pos.cursor(buf, { math.max(0, math.ceil(lnum + (vcount * d))), col })
+    return { start, dst }
+  end)
+end
+
 vim.keymap.set("n", "<plug>(smoothie-ctrl-d)", function()
   vim._with({ win = 0 }, function()
-    scroll(vim.v.count1)
+    M.scroll(vim.v.count1)
   end)
 end)
 vim.keymap.set("n", "<plug>(smoothie-ctrl-u)", function()
   vim._with({ win = 0 }, function()
-    scroll(-vim.v.count1)
+    M.scroll(-vim.v.count1)
   end)
 end)
+
+-- helpers ====================================================================
+
+---@param min number
+---@param n number
+---@param max number
+---@return number
+function H.clamp(min, n, max)
+  return math.max(min, math.min(n, max))
+end
+
+---@param n number
+---@param t number
+---@return number
+function H.coillerp(n, t)
+  t = H.clamp(0, t, 1)
+  return (math.log(1 + t) * 1 + math.log(1 + t)) * n
+end
-- 
2.51.2