From ed3f218dfb69501c5db951fcdca5e61aa1eb58ed Mon Sep 17 00:00:00 2001
From: Folkert Kevelam <contact@pyllr.nl>
Date: Fri, 12 Sep 2025 17:21:05 +0200
Subject: [PATCH] add buffer change event callback

---
 lua/MarkdownPreviewer/init.lua | 64 ++++++++++++++++++++++++++--------
 1 file changed, 49 insertions(+), 15 deletions(-)

diff --git a/lua/MarkdownPreviewer/init.lua b/lua/MarkdownPreviewer/init.lua
index b932c39..5c78a83 100644
--- a/lua/MarkdownPreviewer/init.lua
+++ b/lua/MarkdownPreviewer/init.lua
@@ -20,23 +20,12 @@ function module.setup()
     server_connection = client.setup()
 end
 
-function module.open()
-    augroup = nvim_create_augroup("MarkdownPreviewActiveAugroup", {clear = true})
-
-    server_connection:init(function()
-        augroup = nvim_del_augroup_by_id(augroup)
-    end)
-
-    local bufnr = vim.api.nvim_get_current_buf()
-    server_connection:base(vim.fn.fnamemodify(vim.uri_to_fname(vim.uri_from_bufnr(bufnr)), 'p:h'))
-    server_connection:show(get_buf_content(bufnr))
-    server_connection:scroll(vim.fn.line('.'))
-
+local function SetAutoCmd(augroup, server, bufnr)
     nvim_create_autocmd("BufWritePost", {
         group = augroup,
         buffer = bufnr,
         callback = function()
-            server_connection:show(get_buf_content(bufnr))
+            server:show(get_buf_content(bufnr))
         end,
     })
 
@@ -44,12 +33,12 @@ function module.open()
         group = augroup,
         buffer = bufnr,
         callback = function()
-            server_connection:scroll({vim.fn.line('.'), vim.fn.line('$')})
+            server:scroll({vim.fn.line('.'), vim.fn.line('$')})
         end,
     })
 
     local function show()
-        server_connection:show(get_buf_content(bufnr))
+        server:show(get_buf_content(bufnr))
     end
 
     nvim_create_autocmd({"TextChanged", "TextChangedI", "TextChangedP" }, {
@@ -59,7 +48,52 @@ function module.open()
             throttle.run_fn(show)
         end,
     })
+end
 
+local function FirstSend(server, bufnr)
+    print("Sending data to server from buffer " .. bufnr)
+    server:base(vim.fn.fnamemodify(vim.uri_to_fname(vim.uri_from_bufnr(bufnr)), 'p:h'))
+    server:show(get_buf_content(bufnr))
+    server:scroll(vim.fn.line('.'))
+end
+
+function module.open()
+    augroup = nvim_create_augroup("MarkdownPreviewActiveAugroup", {clear = true})
+    chgbuffergroup = nvim_create_augroup("MarkdownChangeBufferActiveAugroup", {clear = true})
+
+    server_connection:init(function()
+        if augroup then
+            augroup = nvim_del_augroup_by_id(augroup)
+        end
+
+        if chgbuffergroup then
+            chgbuffergroup = nvim_del_augroup_by_id(chgbuffergroup)
+        end
+    end)
+
+    local bufnr = vim.api.nvim_get_current_buf()
+    FirstSend(server_connection, bufnr)
+    SetAutoCmd(augroup, server_connection, bufnr)
+
+    nvim_create_autocmd("BufEnter", {
+        group = chgbuffergroup,
+        callback = function()
+            local new_buf_nr = vim.api.nvim_get_current_buf()
+            local ft = vim.api.nvim_buf_get_option(new_buf_nr, "filetype")
+            if ft == "markdown" then
+                print("filetype new buffer: " .. ft)
+                FirstSend(server_connection, new_buf_nr)
+                if augroup then
+                    augroup = nvim_del_augroup_by_id(augroup)
+                end
+                augroup = nvim_create_augroup("MarkdownPreviewActiveAugroup", {clear = True})
+                SetAutoCmd(augroup, server_connection, new_buf_nr)
+            else
+                print("Not a markdown buffer")
+                augroup = nvim_del_augroup_by_id(augroup)
+            end
+        end,
+    })
 end
 
 function module.close()