Lua Plugin Implementation

[SirZenith]

As mentioned in #2609, I am implementing a Lua plugin system in lf, code can be checked here. In LUA_DEV.md I wrote about how the plugin system is implemented.

Now I think it's time to finally make a pull request. Just before that, I want to known if anybody has any opinion or advice on the code I've written.

I think I will be dealing with following problems next:

• app object is now a global variable in Lua runtime used to access ui and nav, but it's exposed with no concurrency protection. Some inspection is needed on this, but I haven't thought about it yet, any advice is welcome.
• Splitting UI element drawing functions in to smaller parts that can be overridden in Lua script, so that user can customize program appearance even more.

[SirZenith]

A simple Lua script to give a taste of how it works:

Click to expand

local lf = require "lf"

local Style = lf_types.TcellStyle

local KeyMapType = lf.KeyMapType

local function select_nontagged()
    local nav = app:nav()
    nav:unselect()

    local dir = nav:curr_dir()
    if not dir then return end

    dir:files_for_each(function(_, file)
        local path = file:path()
        if not nav:get_tag(path) then
            nav:select(path)
        end
    end)
end

local function glob_select_nontagged(target_ext)
    local nav = app:nav()
    nav:unselect()

    local dir = nav:curr_dir()
    if not dir then return end

    dir:files_for_each(function(_, file)
        if target_ext == "" or file:ext():sub(2) == target_ext then
            local path = file:path()
            if not nav:get_tag(path) then
                nav:select(path)
            end
        end
    end)
end

---@type lf.PluginRet
return {
    command = {
        ["select-nontagged"] = select_nontagged,
        ["glob-select-nontagged"] = {
            completion = function(args, last_arg)
                if #args ~= 2 then return end

                local ext_list = {}
                local dir = app:nav():curr_dir()
                if dir == nil then return end

                dir:files_for_each(function(_, file)
                    local ext = file:ext()
                    ext = ext:sub(1, 1) == "." and ext:sub(2) or ext
                    if ext ~= "" then
                        table.insert(ext_list, ext)
                    end
                end)

                return lf.match_word(last_arg, ext_list)
            end,
            action = glob_select_nontagged,
        },
        ["get-opt"] = function(name)
            local ui = app:ui()
            local value, err = lf.get_opt(name)
            if err then
                ui:echoerr(err)
            else
                ui:echo(value)
            end
        end,
        ["get-pwd-opt"] = function(name)
            local ui = app:ui()
            local pwd = app:nav():curr_dir():path()

            local value, err = lf.get_local_opt(pwd, name)
            if err then
                ui:echoerr(err)
            else
                ui:echo(value)
            end
        end,
    },
    -- event_hook = require "user.event_hook",
    key_map = {
        [KeyMapType.Normal] = {
            ["T"] = function()
                local err = app:nav():tag_toggle("󰈈")
                if err then
                    app:ui():echoerr(err)
                    return
                end

                err = app:nav():write_tags()
                if err then
                    app:ui():echoerr(err)
                end
            end,
            ["R"] = function()
                lf.call("plugin-reload")
            end,
        }
    },
    -- previewer = require "user.previewer",
    -- sorting_method = require "user.sorting_method",
    ui_formatter = {
        dupfile = function(basename, ext, duplicate_cnt)
            return string.format("%s (%d)%s", basename, duplicate_cnt, ext)
        end,
        tag = function(tag)
            if tag == "󰈈" then
                return Style.new():foreground_name("gray"):wrap(tag)
            end
            return Style:new():foreground_name("red"):wrap(tag)
        end,
    },
    -- ui_style = require "user.ui_style",
}