From 198dd0ab12bc421723fd152e5fe92f1fccb0e550 Mon Sep 17 00:00:00 2001
From: Will Hopkins <willothyh@gmail.com>
Date: Thu, 29 Jun 2023 02:01:16 -0700
Subject: [PATCH] feat: rearrange buffers with mouse drag (#113)

---
 lua/cokeline/hover.lua | 151 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 138 insertions(+), 13 deletions(-)

diff --git a/lua/cokeline/hover.lua b/lua/cokeline/hover.lua
index a252ac4..fca1421 100644
--- a/lua/cokeline/hover.lua
+++ b/lua/cokeline/hover.lua
@@ -10,6 +10,26 @@ function M.hovered()
   return _G.cokeline.__hovered
 end
 
+function M.set_hovered(val)
+  _G.cokeline.__hovered = val
+end
+
+function M.clear_hovered()
+  _G.cokeline.__hovered = nil
+end
+
+function M.dragging()
+  return _G.cokeline.__dragging
+end
+
+function M.set_dragging(val)
+  _G.cokeline.__dragging = val
+end
+
+function M.clear_dragging()
+  _G.cokeline.__dragging = nil
+end
+
 function M.get_current(col)
   local bufs = buffers.get_visible()
   if not bufs then
@@ -21,13 +41,13 @@ function M.get_current(col)
   for _, component in ipairs(cx.sidebar) do
     current_width = current_width + component.width
     if current_width >= col then
-      return component
+      return component, cx.sidebar
     end
   end
   for _, component in ipairs(cx.buffers) do
     current_width = current_width + component.width
     if current_width >= col then
-      return component
+      return component, cx.buffers
     end
   end
   current_width = current_width + cx.gap
@@ -37,13 +57,13 @@ function M.get_current(col)
   for _, component in ipairs(cx.rhs) do
     current_width = current_width + component.width
     if current_width >= col then
-      return component
+      return component, cx.rhs
     end
   end
 end
 
 local function on_hover(current)
-  local hovered = _G.cokeline.__hovered
+  local hovered = M.hovered()
   if vim.o.showtabline == 0 then
     return
   end
@@ -80,7 +100,7 @@ local function on_hover(current)
           hovered.on_mouse_leave(buf)
         end
       end
-      _G.cokeline.__hovered = nil
+      M.clear_hovered()
     end
     if not component then
       vim.cmd.redrawtabline()
@@ -100,12 +120,12 @@ local function on_hover(current)
         component.on_mouse_enter(buf, current.screencol)
       end
     end
-    _G.cokeline.__hovered = {
+    M.set_hovered({
       index = component.index,
       bufnr = buf and buf.number or nil,
       on_mouse_leave = component.on_mouse_leave,
       kind = component.kind,
-    }
+    })
     vim.cmd.redrawtabline()
   elseif hovered ~= nil then
     local buf = buffers.get_buffer(hovered.bufnr)
@@ -121,25 +141,130 @@ local function on_hover(current)
         hovered.on_mouse_leave(buf)
       end
     end
-    _G.cokeline.__hovered = nil
+    M.clear_hovered()
     vim.cmd.redrawtabline()
   end
   last_position = current
 end
 
+local function width(bufs, buf)
+  return vim
+    .iter(bufs)
+    :filter(function(v)
+      return v.bufnr == buf
+    end)
+    :map(function(v)
+      return v.width
+    end)
+    :fold(0, function(acc, v)
+      return acc + v
+    end)
+end
+
+local function start_pos(bufs, buf)
+  local pos = 0
+  for _, v in ipairs(bufs) do
+    if v.bufnr == buf then
+      return pos
+    end
+    pos = pos + v.width
+  end
+  return pos
+end
+
+local function on_drag(pos)
+  if pos.dragging == "l" then
+    local current, bufs = M.get_current(pos.screencol)
+    if current == nil or bufs == nil or current.kind ~= "buffer" then
+      return
+    end
+
+    -- if we're not dragging yet or we're dragging the same buffer, start dragging
+    if M.dragging() == current.bufnr or not M.dragging() then
+      M.set_dragging(current.bufnr)
+      return
+    end
+
+    -- dragged buffer
+    local dragged_buf = buffers.get_buffer(M.dragging())
+    if not dragged_buf then
+      return
+    end
+
+    -- current (hovered) buffer
+    local cur_buf = buffers.get_buffer(current.bufnr)
+    if not cur_buf then
+      return
+    end
+
+    -- start position of dragged buffer
+    local dragging_start = start_pos(bufs, M.dragging())
+    -- width of the current (hovered) buffer
+    local cur_buf_width = width(bufs, current.bufnr)
+
+    if
+      -- buffer is being dragged to the left
+      (
+        dragging_start > pos.screencol
+        and pos.screencol + cur_buf_width > dragging_start
+      )
+      -- buffer is being dragged to the right
+      or dragging_start + cur_buf_width <= pos.screencol
+    then
+      buffers.move_buffer(dragged_buf, cur_buf._valid_index)
+    end
+  end
+end
+
 function M.setup()
-  if version.minor < 8 then
+  if version.minor < 8 or not vim.on_key then
     return
   end
 
-  vim.keymap.set({ "", "i" }, "<MouseMove>", function()
+  local mouse_move = vim.keycode("<MouseMove>")
+  local drag = {
+    [vim.keycode("<LeftDrag>")] = "l",
+    [vim.keycode("<RightDrag>")] = "r",
+    [vim.keycode("<MiddleDrag>")] = "m",
+  }
+  vim.on_key(function(key)
     local ok, pos = pcall(vim.fn.getmousepos)
     if not ok then
       return
     end
-    on_hover(pos)
-    return "<MouseMove>"
-  end, { expr = true })
+
+    local data = {
+      dragging = drag[key],
+      screencol = pos.screencol,
+      screenrow = pos.screenrow,
+      line = pos.line,
+      column = pos.column,
+      winid = pos.winid,
+      winrow = pos.winrow,
+      wincol = pos.wincol,
+    }
+    if key == mouse_move then
+      M.clear_dragging()
+      on_hover(data)
+    elseif drag[key] then
+      local hov = M.hovered()
+      if hov then
+        local buf = buffers.get_buffer(hov.bufnr)
+        if buf then
+          buf.is_hovered = false
+        end
+        if hov.kind == "buffer" then
+          if buf and hov.on_mouse_leave then
+            hov.on_mouse_leave(buf)
+          end
+        elseif hov.on_mouse_leave then
+          hov.on_mouse_leave()
+        end
+        M.clear_hovered()
+      end
+      on_drag(data)
+    end
+  end)
 end
 
 return M