nixos/hosts/nb/modules/development/nvim/config/sops.lua

-- SOPS integration for automatic encryption/decryption of secrets files
-- This module sets up autocmds to handle .secrets.yaml files transparently

local sops_group = vim.api.nvim_create_augroup("SopsEncryption", { clear = true })

-- Pattern matching for secrets files
local secrets_patterns = {
  "*/secrets.yaml",
}

-- Size limits to prevent memory issues and UI freezes
-- 5MB encrypted file limit (typical secrets files are <100KB)
local MAX_SOPS_FILE_SIZE = 5 * 1024 * 1024 -- 5MB
-- 10MB decrypted content limit (allows for expansion during decryption)
local MAX_DECRYPTED_SIZE = 10 * 1024 * 1024 -- 10MB
-- Timeout for SOPS operations to prevent infinite hangs
local SOPS_TIMEOUT = 30 -- seconds

-- Guard against double-execution (patterns overlap, causing callback to fire twice)
local currently_saving = {}

-- Helper function to check if file matches secrets pattern
local function is_secrets_file(filepath)
  for _, pattern in ipairs(secrets_patterns) do
    if vim.fn.match(filepath, vim.fn.glob2regpat(pattern)) ~= -1 then
      return true
    end
  end
  return false
end

-- Set filetype before reading to enable syntax highlighting
vim.api.nvim_create_autocmd("BufReadPre", {
  group = sops_group,
  pattern = secrets_patterns,
  callback = function(args)
    -- Set filetype to yaml before the file is read so syntax highlighting works
    vim.bo.filetype = "yaml"
  end,
})

-- Decrypt file after reading
vim.api.nvim_create_autocmd("BufReadPost", {
  group = sops_group,
  pattern = secrets_patterns,
  callback = function(args)
    local filepath = vim.fn.expand("%:p")

    -- Only decrypt if file exists and has content
    if vim.fn.filereadable(filepath) == 1 and vim.fn.getfsize(filepath) > 0 then
      -- Check file size before attempting to decrypt
      local filesize = vim.fn.getfsize(filepath)
      if filesize > MAX_SOPS_FILE_SIZE then
        local size_mb = string.format("%.1f", filesize / (1024 * 1024))
        local limit_mb = string.format("%.1f", MAX_SOPS_FILE_SIZE / (1024 * 1024))
        vim.notify(
          string.format("SOPS: File too large (%sMB > %sMB limit). Skipping decryption to prevent freeze.", size_mb, limit_mb),
          vim.log.levels.WARN
        )
        return
      end

      -- Save cursor position
      local cursor_pos = vim.api.nvim_win_get_cursor(0)

      -- Decrypt file content with timeout to prevent hanging
      local cmd = string.format("timeout %d sops --decrypt %s", SOPS_TIMEOUT, vim.fn.shellescape(filepath))
      local result = vim.fn.system(cmd)
      local exit_code = vim.v.shell_error

      -- Check for timeout (exit code 124 from timeout command)
      if exit_code == 124 then
        vim.notify(
          string.format("SOPS: Decryption timed out after %d seconds. Check your SOPS configuration and age keys.", SOPS_TIMEOUT),
          vim.log.levels.ERROR
        )
        return
      end

      if exit_code == 0 then
        -- Validate decrypted content size before loading into buffer
        if #result > MAX_DECRYPTED_SIZE then
          local size_mb = string.format("%.1f", #result / (1024 * 1024))
          local limit_mb = string.format("%.1f", MAX_DECRYPTED_SIZE / (1024 * 1024))
          vim.notify(
            string.format("SOPS: Decrypted content too large (%sMB > %sMB limit). Skipping to prevent freeze.", size_mb, limit_mb),
            vim.log.levels.WARN
          )
          return
        end

        -- Replace buffer content with decrypted content
        vim.api.nvim_buf_set_lines(0, 0, -1, false, vim.split(result, "\n"))

        -- Mark buffer as not modified (since we just loaded it)
        vim.bo.modified = false

        -- Restore cursor position
        pcall(vim.api.nvim_win_set_cursor, 0, cursor_pos)

        -- Disable swap, backup, and undo files for security
        vim.bo.swapfile = false
        vim.bo.backup = false
        vim.bo.writebackup = false
        vim.bo.undofile = false

        -- Ensure filetype is set to yaml for syntax highlighting
        vim.bo.filetype = "yaml"

        vim.notify("SOPS: File decrypted successfully", vim.log.levels.INFO)
      else
        vim.notify("SOPS: Failed to decrypt file: " .. result, vim.log.levels.ERROR)
      end
    end
  end,
})

-- Override write command for secrets files
vim.api.nvim_create_autocmd("BufWriteCmd", {
  group = sops_group,
  pattern = secrets_patterns,
  callback = function(args)
    local filepath = vim.fn.expand("%:p")

    if is_secrets_file(filepath) then
      -- Guard against double-execution
      if currently_saving[filepath] then
        return
      end
      currently_saving[filepath] = true

      -- Get current buffer content
      local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
      local content = table.concat(lines, "\n")

      -- Check buffer content size before encrypting
      if #content > MAX_DECRYPTED_SIZE then
        local size_mb = string.format("%.1f", #content / (1024 * 1024))
        local limit_mb = string.format("%.1f", MAX_DECRYPTED_SIZE / (1024 * 1024))
        vim.notify(
          string.format("SOPS: Buffer content too large (%sMB > %sMB limit). Cannot encrypt.", size_mb, limit_mb),
          vim.log.levels.ERROR
        )
        -- Don't write anything, leave buffer marked as modified
        currently_saving[filepath] = nil
        return
      end

      -- Encrypt content using SOPS via temporary file in same directory
      -- This avoids /dev/stdin issues while keeping secrets secure (not in /tmp)
      local dir = vim.fn.fnamemodify(filepath, ":h")
      local filename = vim.fn.fnamemodify(filepath, ":t")
      local temp_file = string.format("%s/.%s.sops_tmp_%d", dir, filename, os.time())

      -- Write plaintext content to temp file
      local temp_f, temp_err = io.open(temp_file, "w")
      if not temp_f then
        vim.notify("SOPS: Failed to create temp file: " .. (temp_err or "unknown error"), vim.log.levels.ERROR)
        -- Don't write anything, leave buffer marked as modified
        currently_saving[filepath] = nil
        return
      end
      temp_f:write(content)
      temp_f:close()

      -- Encrypt temp file with filename override so SOPS matches .sops.yaml rules
      -- Uses real filepath for rule matching, temp file for content
      local cmd = string.format("sops --encrypt --filename-override %s %s",
        vim.fn.shellescape(filepath),
        vim.fn.shellescape(temp_file))
      local encrypted = vim.fn.system(cmd)
      local sops_exit_code = vim.v.shell_error

      -- Always clean up temp file, even on error
      os.remove(temp_file)

      if sops_exit_code == 0 then
        -- Write encrypted content directly to file
        local file, err = io.open(filepath, "w")
        if file then
          local success, write_err = file:write(encrypted)
          file:close()

          if success then
            -- Mark buffer as saved
            vim.bo.modified = false
            vim.notify("SOPS: File encrypted and saved successfully", vim.log.levels.INFO)

            -- Re-decrypt to show plaintext in buffer
            local decrypt_cmd = string.format("timeout %d sops --decrypt %s", SOPS_TIMEOUT, vim.fn.shellescape(filepath))
            local decrypted = vim.fn.system(decrypt_cmd)
            local decrypt_exit = vim.v.shell_error

            if decrypt_exit == 0 then
              -- Save cursor position
              local cursor_pos = vim.api.nvim_win_get_cursor(0)

              -- Replace buffer with decrypted content
              vim.api.nvim_buf_set_lines(0, 0, -1, false, vim.split(decrypted, "\n"))

              -- Mark as not modified since we just saved
              vim.bo.modified = false

              -- Restore cursor position
              pcall(vim.api.nvim_win_set_cursor, 0, cursor_pos)
            else
              vim.notify("SOPS: Could not re-decrypt after save. Buffer may show encrypted content.", vim.log.levels.WARN)
            end
            -- Clear guard after successful save
            currently_saving[filepath] = nil
          else
            vim.notify("SOPS: Failed to write encrypted content: " .. (write_err or "unknown error"), vim.log.levels.ERROR)
            -- Don't mark as saved, keep buffer marked as modified
            currently_saving[filepath] = nil
          end
        else
          vim.notify("SOPS: Failed to open file for writing: " .. (err or "unknown error"), vim.log.levels.ERROR)
          -- Don't mark as saved, keep buffer marked as modified
          currently_saving[filepath] = nil
        end
      else
        vim.notify("SOPS: Failed to encrypt file - NOT SAVED! Error: " .. encrypted, vim.log.levels.ERROR)
        -- Don't write anything, leave buffer marked as modified
        currently_saving[filepath] = nil
      end
    end
  end,
})

-- Warn when leaving a secrets buffer with unsaved changes
vim.api.nvim_create_autocmd("BufLeave", {
  group = sops_group,
  pattern = secrets_patterns,
  callback = function(args)
    if vim.bo.modified then
      vim.notify("Warning: Unsaved changes in secrets file!", vim.log.levels.WARN)
    end
  end,
})