initial commit

1 files changed, 121 insertions, 0 deletions

diff --git a/init.lua b/init.lua
new file mode 100644
index 0000000..02fee0d
--- /dev/null
+++ b/init.lua
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+-- Copyright (c) 2024 Florian Fischer. All rights reserved.
+--
+-- vis-lockfiles is free software: you can redistribute it and/or modify it under
+-- the terms of the GNU General Public License as published by the Free Software
+-- Foundation, either version 3 of the License, or (at your option) any later
+-- version.
+--
+-- vis-lockfiles is distributed in the hope that it will be useful, but WITHOUT
+-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+-- FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License along with
+-- vis-lockfiles found in the LICENSE file.
+-- If not, see <https://www.gnu.org/licenses/>.
+local M = {}
+M.directory = '${XDG_CACHE_HOME:-${HOME}/.local/share}/vis/locks'
+
+-- Helper to execute a command and capture its output
+local function capture_cmd(cmd)
+  local p = assert(io.popen(cmd, 'r'))
+  local s = assert(p:read('*a'))
+  local success, _, status = p:close()
+  if not success then
+    local err = cmd .. ' failed with exit code: ' .. status
+    vis:info('vis-lockfiles: ' .. err)
+  end
+  return s
+end
+
+local function lock_file_path(path)
+  local filename = path:gsub('/', '%%')
+  assert(os.execute('mkdir -p "' .. M.directory .. '"'))
+  local lfile_path = capture_cmd('echo "' .. M.directory .. '/' .. filename .. '.lock"')
+  return lfile_path:sub(1, #lfile_path - 1) -- trim newline from path
+end
+
+-- determine vis' pid
+local vis_pid
+do
+  local vis_proc_file = io.open('/proc/self/stat', 'r')
+  if vis_proc_file then
+    vis_pid = vis_proc_file:read('*n')
+    vis_proc_file:close()
+
+  else -- fallback if /proc/self/stat is not available
+    local out = capture_cmd('sh -c "echo $PPID"')
+    vis_pid = tonumber(out)
+  end
+end
+assert(vis_pid)
+
+-- get a user confirmation
+-- return true if user selected yes, false otherwise
+local function confirm(path)
+  local choices = 'no\nyes'
+  local prompt = path .. ' exists. Edit anyway:'
+  local cmd = 'printf "' .. choices .. '" | vis-menu -b -p \'' .. prompt .. '\''
+
+  local choice = nil
+  -- local status, output = vis:pipe(nil, {start = 0, finish = 0}, cmd)
+  local menu = assert(io.popen(cmd))
+  local output = menu:read('*a')
+  local _, _, status = menu:close()
+  if status == 0 then
+    -- trim newline from selection
+    if output:sub(-1) == '\n' then
+      choice = output:sub(1, -2)
+    else
+      choice = output
+    end
+  end
+  vis:redraw()
+  return choice == 'yes'
+end
+
+local created_locks = {}
+local function create_lock_file(lfile_path)
+  local already_locked = os.execute('test -e ' .. '"' .. lfile_path .. '"')
+  if already_locked then
+    return false
+  end
+
+  -- create the lock file with our pid
+  local cmd = 'echo ' .. vis_pid .. ' > "' .. lfile_path .. '"'
+  assert(os.execute(cmd))
+
+  -- detect a possible race
+  local lock_file = io.open(lfile_path)
+  assert(lock_file)
+  local lock_pid = lock_file:read('*n')
+  lock_file:close()
+  local locked = tonumber(lock_pid) == vis_pid
+
+  -- remember we created the lock file
+  if locked then
+    created_locks[lfile_path] = true
+  end
+
+  return locked
+end
+
+local function delete_lock_file(lfile_path)
+  os.execute('rm ' .. '"' .. lfile_path .. '"')
+  created_locks[lfile_path] = nil
+end
+
+vis.events.subscribe(vis.events.FILE_OPEN, function(file)
+  local lfile_path = lock_file_path(file.path)
+  if not create_lock_file(lfile_path) and not confirm(lfile_path) then
+    os.exit(1)
+  end
+end)
+
+vis.events.subscribe(vis.events.FILE_CLOSE, function(file)
+  local lfile_path = lock_file_path(file.path)
+  if created_locks[lfile_path] then
+    delete_lock_file(lfile_path)
+  end
+end)
+
+return M