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feat(reload): add SSE live-reload server module

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Problem: HTML output from pandoc has no live-reload; the browser must
be refreshed manually after each compile.

Solution: add lua/preview/reload.lua — a minimal SSE-only TCP server.
start() binds 127.0.0.1:5554 and keeps EventSource connections alive;
broadcast() pushes a reload event to all clients; inject() appends an
EventSource script before </body> (or at EOF) on every compile so
pandoc overwrites do not lose the tag.
This commit is contained in:
Barrett Ruth 2026-03-03 16:23:35 -05:00
parent bce3cec0e6
commit 6c1609cba8
Signed by: barrett
GPG key ID: A6C96C9349D2FC81
2 changed files with 166 additions and 0 deletions
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108
lua/preview/reload.lua Normal file
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local M = {}
local PORT = 5554
local server_handle = nil
local clients = {}
local function make_script(port)
return '<script>(function(){'
.. 'var es=new EventSource("http://localhost:'
.. tostring(port)
.. '/__live/events");'
.. 'es.addEventListener("reload",function(){location.reload();});'
.. '})()</script>'
end
function M.start(port)
port = port or PORT
if server_handle then
return
end
local server = vim.uv.new_tcp()
server:bind('127.0.0.1', port)
server:listen(128, function(err)
if err then
return
end
local client = vim.uv.new_tcp()
server:accept(client)
local buf = ''
client:read_start(function(read_err, data)
if read_err or not data then
if not client:is_closing() then
client:close()
end
return
end
buf = buf .. data
if buf:find('\r\n\r\n') or buf:find('\n\n') then
client:read_stop()
local first_line = buf:match('^([^\r\n]+)')
if first_line and first_line:find('/__live/events', 1, true) then
local response = 'HTTP/1.1 200 OK\r\n'
.. 'Content-Type: text/event-stream\r\n'
.. 'Cache-Control: no-cache\r\n'
.. 'Access-Control-Allow-Origin: *\r\n'
.. '\r\n'
client:write(response)
table.insert(clients, client)
else
client:close()
end
end
end)
end)
server_handle = server
end
function M.stop()
for _, c in ipairs(clients) do
if not c:is_closing() then
c:close()
end
end
clients = {}
if server_handle then
server_handle:close()
server_handle = nil
end
end
function M.broadcast()
local event = 'event: reload\ndata: {}\n\n'
local alive = {}
for _, c in ipairs(clients) do
if not c:is_closing() then
local ok = pcall(function()
c:write(event)
end)
if ok then
table.insert(alive, c)
end
end
end
clients = alive
end
function M.inject(path, port)
port = port or PORT
local f = io.open(path, 'r')
if not f then
return
end
local content = f:read('*a')
f:close()
local script = make_script(port)
local new_content, n = content:gsub('</body>', script .. '\n</body>', 1)
if n == 0 then
new_content = content .. '\n' .. script
end
local fw = io.open(path, 'w')
if not fw then
return
end
fw:write(new_content)
fw:close()
end
return M

58
spec/reload_spec.lua Normal file
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describe('reload', function()
local reload
before_each(function()
package.loaded['preview.reload'] = nil
reload = require('preview.reload')
end)
after_each(function()
reload.stop()
end)
describe('inject', function()
it('injects script before </body>', function()
local path = os.tmpname()
local f = io.open(path, 'w')
f:write('<html><body><p>hello</p></body></html>')
f:close()
reload.inject(path)
local fr = io.open(path, 'r')
local content = fr:read('*a')
fr:close()
os.remove(path)
assert.is_truthy(content:find('EventSource', 1, true))
local script_pos = content:find('EventSource', 1, true)
local body_pos = content:find('</body>', 1, true)
assert.is_truthy(body_pos)
assert.is_true(script_pos < body_pos)
end)
it('appends script when no </body>', function()
local path = os.tmpname()
local f = io.open(path, 'w')
f:write('<html><p>hello</p></html>')
f:close()
reload.inject(path)
local fr = io.open(path, 'r')
local content = fr:read('*a')
fr:close()
os.remove(path)
assert.is_truthy(content:find('EventSource', 1, true))
end)
end)
describe('broadcast', function()
it('does not error with no clients', function()
assert.has_no.errors(function()
reload.broadcast()
end)
end)
end)
end)