feat(attach): add OrgAttach:expand_links()

This corresponds to the Emacs function `org-attach-expand-links`.

Author: broken-pen

lua/orgmode/attach/core.lua

@@ -575,4 +575,40 @@ function AttachCore:sync(node, delete_empty_dir)
   end)
 end
 
+---Call `callback` with every attachment link in the file.
+---
+---@param file OrgFile
+---@param callback fun(attach_dir: string|false, basename: string): string|nil
+---@return OrgPromise<nil>
+function AttachCore:on_every_attachment_link(file, callback)
+  -- TODO: In a better world, this would use treesitter for parsing ...
+  return file:update(function()
+    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, true)
+    local prev_node = nil ---@type OrgAttachNode | nil
+    local attach_dir = nil ---@type string | false | nil
+    for i, line in ipairs(lines) do
+      -- Check if node has changed; if yes, invalidate cached attach_dir.
+      local node = AttachNode.at_cursor(file, { i + 1, 0 })
+      if node ~= prev_node then
+        attach_dir = nil
+      end
+      ---@param basename string
+      ---@param bracket '[' | ']'
+      ---@return string
+      local replaced = line:gsub('%[%[attachment:([^%]]+)%]([%[%]])', function(basename, bracket)
+        -- Only compute attach_dir when we know that we need it!
+        if attach_dir == nil then
+          attach_dir = self:get_dir_or_nil(node, true) or false
+        end
+        local res = callback(attach_dir, basename)
+        return res and ('[[%s]%s'):format(res, bracket) or ('[[attachment:%s]%s'):format(basename, bracket)
+      end)
+      if replaced ~= line then
+        vim.api.nvim_buf_set_lines(0, i - 1, i, true, { replaced })
+      end
+      prev_node = node
+    end
+  end)
+end
+
 return AttachCore

lua/orgmode/attach/init.lua

@@ -648,4 +648,36 @@ function Attach:sync(node)
   return self.core:sync(node, delete_empty_dir):wait(MAX_TIMEOUT)
 end
 
+---Expand links in current buffer.
+---
+---It is meant to be added to `org_export_before_parsing_hook`."
+---TODO: Add this hook. Will require refactoring `orgmode.export`.
+---
+---@param bufnr? integer
+---@return nil
+function Attach:expand_links(bufnr)
+  bufnr = bufnr or 0
+  local file = self.core.files:get(vim.api.nvim_buf_get_name(bufnr))
+  local total = 0
+  local miss = 0
+  self.core
+    :on_every_attachment_link(file, function(attach_dir, basename)
+      total = total + 1
+      if not attach_dir then
+        miss = miss + 1
+        return
+      end
+      return 'file:' .. vim.fs.joinpath(attach_dir, basename)
+    end)
+    :next(function()
+      if miss > 0 then
+        utils.echo_warning(('failed to expand %d/%d attachment links'):format(miss, total))
+      else
+        utils.echo_info(('expanded %d attachment links'):format(total))
+      end
+      return nil
+    end)
+    :wait(MAX_TIMEOUT)
+end
+
 return Attach