telescope-frecency.nvim/README.md

# telescope-frecency.nvim

A [telescope.nvim][] extension that offers intelligent prioritization when
selecting files from your editing history.

[telescope.nvim]: https://github.com/nvim-telescope/telescope.nvim

Using an implementation of Mozilla's [Frecency algorithm][] (used in [Firefox's
address bar][]), files edited _frecently_ are given higher precedence in the
list index.

[Frecency algorithm]: https://web.archive.org/web/20210421120120/https://developer.mozilla.org/en-US/docs/Mozilla/Tech/Places/Frecency_algorithm
[Firefox's address bar]: https://support.mozilla.org/en-US/kb/address-bar-autocomplete-firefox

As the extension learns your editing habits over time, the sorting of the list
is dynamically altered to prioritize the files you're likely to need.

<img src="https://raw.githubusercontent.com/sunjon/images/master/gh_readme_telescope_frecency.png" alt="screenshot" width="800"/>

* _Scores shown in finder for demonstration purposes - disabled by default_

## Frecency: Sorting by 'frequency' _and_ 'recency'

'Frecency' is a score given to each unique file indexed in a file history
database.

A timestamp is recorded once per session when a file is first loaded into a
buffer.

The score is calculated using the age of the 10 (customizable) most recent
timestamps and the total amount of times that the file has been loaded:

### Recency values (per timestamp)

| Timestamp age | Value |
| -------- | ---------- |
| 4 hours  | 100        |
| 1 day    | 80         |
| 3 days   | 60         |
| 1 week   | 40         |
| 1 month  | 20         |
| 90 days  | 10         |

### Score calculation

```lua
score = frequency * recency_score / max_number_of_timestamps
```
## What about files that are neither 'frequent' _or_ 'recent' ?

Frecency naturally works best for indexed files that have been given a
reasonably high score.

New projects or rarely used files with generic names either don't get listed at
all or can be buried under results with a higher score.

Frecency tackles this with *Workspace Filters*:

<img src="https://raw.githubusercontent.com/sunjon/images/master/frecency_workspace_folders.gif" alt="screenshot" width="800"/>

The workspace filter feature enables you to select from user defined _filter
tags_ that map to a directory or collection of directories. Filters are applied
by entering `:workspace_tag:` anywhere in the query. Filter name completion is
available by pressing `<Tab>` after the first `:` character.

When a filter is applied, results are reduced to entries whose path is a
descendant of the workspace directory. The indexed results are optionally
augmented with a listing of _all_ files found in a recurssive search of the
workspace directory. Non-indexed files are given a score of zero and appear
below the 'frecent' entries. When a non-indexed file is opened, it gains a
score value and is available in future 'frecent' search results.

If the active buffer (prior to the finder being launched) is attached to an LSP
server, an automatic `LSP` tag is available, which maps to the workspace
directories provided by the language server.


## Requirements

- [telescope.nvim](https://github.com/nvim-telescope/telescope.nvim) (required)
- [nvim-web-devicons](https://github.com/kyazdani42/nvim-web-devicons) (optional)

**NOTE:** The former version of this plugin has used [SQLite3][] database to
store timestamps and file records. But the current build uses Lua native code
to store them, so you can now remove [sqlite.lua][] from dependencies. See
[*Remove dependency for sqlite.lua*][remove-sqlite] for the detail.

[SQLite3]: https://www.sqlite.org/index.html
[sqlite.lua]: https://github.com/kkharji/sqlite.lua
[remove-sqlite]: #user-content-remove-dependency-for-sqlitelua

## Installation

### [Packer.nvim](https://github.com/wbthomason/packer.nvim)

```lua
use {
  "nvim-telescope/telescope-frecency.nvim",
  config = function()
    require("telescope").load_extension "frecency"
  end,
}
```

### [Lazy.nvim](https://github.com/folke/lazy.nvim)

```lua
{
  "nvim-telescope/telescope-frecency.nvim",
  config = function()
    require("telescope").load_extension "frecency"
  end,
}
```

If no database is found when running Neovim with the plugin installed, a new
one is created and entries from `shada` `v:oldfiles` are automatically
imported.

## Usage

```vim
:Telescope frecency
```

or to map to a key:

```lua
vim.keymap.set("n", "<leader><leader>", "<Cmd>Telescope frecency<CR>")
```

Use a specific workspace tag:

```vim
:Telescope frecency workspace=CWD
```

or

```lua
vim.keymap.set("n", "<leader><leader>", "<Cmd>Telescope frecency workspace=CWD<CR>")
```

Filter tags are applied by typing the `:tag:` name (adding surrounding colons)
in the finder query. Entering `:<Tab>` will trigger omnicompletion for
available tags.

## Configuration

See [default configuration](https://github.com/nvim-telescope/telescope.nvim#telescope-defaults) for full details on configuring Telescope.

- `db_root` (default: `vim.fn.stdpath "data"`)

  Path to parent directory of custom database location. Defaults to
  `$XDG_DATA_HOME/nvim` if unset.

- `default_workspace` (default: `nil`)

  Default workspace tag to filter by e.g. `'CWD'` to filter by default to the
  current directory. Can be overridden at query time by specifying another
  filter like `':*:'`.

- `disable_devicons` (default: `false`)

  Disable devicons (if available)

- `ignore_patterns` (default: `{ "*.git/*", "*/tmp/*", "term://*" }`)

  Patterns in this table control which files are indexed (and subsequently
  which you'll see in the finder results).

- `max_timestamps` (default: `10`)

  Set the max count of timestamps DB keeps when you open files. It ignores the
  value and use `10` if you set less than or equal to `0`.

  **CAUTION** When you reduce the value of this option, it removes old
  timestamps when you open the file. It is reasonable to set this value more
  than or equal to the default value: `10`.

- `show_filter_column` (default: `true`)

  Show the path of the active filter before file paths. In default, it uses the
  tail of paths for `'LSP'` and `'CWD'` tags. You can configure this by setting
  a table for this option.

   ```lua
   -- show the tail for "LSP", "CWD" and "FOO"
   show_filter_column = { "LSP", "CWD", "FOO" }
   ```

- `show_scores` (default : `false`)

  To see the scores generated by the algorithm in the results, set this to
  `true`.

- `show_unindexed` (default: `true`)

  Determines if non-indexed files are included in workspace filter results.

- `use_sqlite` (default: `false`)

  Use [sqlite.lua][] with `true` or native code with `false`. See [*Remove
  dependency for sqlite.lua*][remove-sqlite] for the detail.

- `workspaces` (default: `{}`)

  This table contains mappings of `workspace_tag` -> `workspace_directory`. The
  key corresponds to the `:tag_name` used to select the filter in queries. The
  value corresponds to the top level directory by which results will be
  filtered.

### Example Configuration:

```lua
telescope.setup {
  extensions = {
    frecency = {
      db_root = "/home/my_username/path/to/db_root",
      show_scores = false,
      show_unindexed = true,
      ignore_patterns = { "*.git/*", "*/tmp/*" },
      disable_devicons = false,
      workspaces = {
        ["conf"]    = "/home/my_username/.config",
        ["data"]    = "/home/my_username/.local/share",
        ["project"] = "/home/my_username/projects",
        ["wiki"]    = "/home/my_username/wiki"
      }
    }
  },
}
```

## Note for Database

### Location

The default location for the database is `$XDG_DATA_HOME/nvim` (eg
`~/.local/share/nvim/` on linux). This can be configured with the `db_root`
config option.

### Maintainance

By default, frecency will prune files that no longer exist from the database.
In certain workflows, switching branches in a repository, that behaviour might
not be desired. The following configuration control this behaviour:

<dl>
<dt><code>db_safe_mode</code></dt>
<dd>When this is enabled, the user will be prompted before any entries are removed from the database.</dd>
<dt><code>auto_validate</code></dt>
<dd>When this to false, stale entries will never be automatically removed.</dd>
</dl>

The command `FrecencyValidate` can be used to clean the database when
`auto_validate` is disabled.

```vim
" clean DB
:FrecencyValidate
" clean DB without prompts to confirm
:FrecencyValidate!
```

### Remove dependency for [sqlite.lua][]

The former version of this plugin has used SQLite3 library to store data. When
you upgrade from such version, Neovim will silently migrate DB and inform that
you can remove `sqlite.lua` from dependencies.

| made by default | made by `sqlite.lua` |
|--|--|
| `~/.local/share/nvim/file_frecency.bin` | `~/.local/share/nvim/file_frecency.sqlite3` |

The DB file will be migrated into a filename above, and old file (SQLite3
version) will still remain. If you still want to use SQLite3 version, set
`use_sqlite = true`.

Also you can explicitly migrate DB by calling `:FrecencyMigrateDB` command.

## Highlight Groups

```vim
TelescopeBufferLoaded
TelescopePathSeparator
TelescopeFrecencyScores
TelescopeQueryFilter
```

TODO: describe highlight groups

## References

- [Mozilla: Frecency algorithm](https://developer.mozilla.org/en-US/docs/Mozilla/Tech/Places/Frecency_algorithm)