Implement theme switcher

using telescope picker

ask if want to change default theme, change value in user_config.lua

load it as a telescope extension

live preview of themes

Co-authored-by: Galen Rowell <growell3@gmail.com>

lua/plugins/telescope.lua

@@ -67,6 +67,9 @@ telescope.setup(
     }
 )
 
+-- load the theme_switcher extension
+require("telescope").load_extension("themes")
+
 if
     not pcall(
         function()

lua/telescope/_extensions/themes.lua

@@ -0,0 +1,185 @@
+-- This file can be loaded as a telescope extension
+local M = {}
+
+-- reload themes without restarting vim
+-- if no theme name given then reload the current theme
+M.reload_theme = function(theme_name)
+    local reload_plugin = require("utils").reload_plugin
+
+    -- if theme name is empty or nil, then reload the current theme
+    if (theme_name == nil or theme_name == "") then
+        theme_name = vim.g.nvchad_theme
+    end
+
+    if not pcall(require, "themes/" .. theme_name) then
+        error("No such theme ( " .. theme_name .. " )")
+    end
+
+    vim.g.nvchad_theme = theme_name
+
+    -- reload the base16 theme
+    local ok, base16 = pcall(require, "base16")
+    if not ok then
+        error("Error: Cannot load base16 plugin!")
+    end
+    base16(base16.themes[theme_name], true)
+
+    reload_plugin {
+        "highlights",
+        "plugins.bufferline",
+        "galaxyline",
+        "plugins.statusline"
+    }
+
+    -- now send the provider info to actual refresh
+    require("galaxyline.provider").async_load_providers:send()
+
+    return true
+    -- open a buffer and close it to reload the statusline
+    -- vim.cmd("new|bwipeout")
+    -- commented out here as it will not work with telescope picker
+end
+
+-- Custom theme picker
+-- Most of the code is copied from telescope colorscheme plugin, mostly for preview creation
+M.theme_switcher = function(opts)
+    local pickers, finders, previewers, actions, action_state, utils, conf
+    if pcall(require, "telescope") then
+        pickers = require "telescope.pickers"
+        finders = require "telescope.finders"
+        previewers = require "telescope.previewers"
+
+        actions = require "telescope.actions"
+        action_state = require "telescope.actions.state"
+        utils = require "telescope.utils"
+        conf = require("telescope.config").values
+    else
+        error "Cannot find telescope!"
+    end
+
+    local local_utils = require "utils"
+    local reload_theme = M.reload_theme
+
+    -- get a table of available themes
+    local themes = local_utils.list_themes()
+    if next(themes) ~= nil then
+        -- save this to use it for later to restore if theme not changed
+        local current_theme = vim.g.nvchad_theme
+        local new_theme = ""
+        local change = false
+
+        -- buffer number and name
+        local bufnr = vim.api.nvim_get_current_buf()
+        local bufname = vim.api.nvim_buf_get_name(bufnr)
+
+        local previewer
+
+        -- in case its not a normal buffer
+        if vim.fn.buflisted(bufnr) ~= 1 then
+            local deleted = false
+            local function del_win(win_id)
+                if win_id and vim.api.nvim_win_is_valid(win_id) then
+                    utils.buf_delete(vim.api.nvim_win_get_buf(win_id))
+                    pcall(vim.api.nvim_win_close, win_id, true)
+                end
+            end
+
+            previewer =
+                previewers.new {
+                preview_fn = function(_, entry, status)
+                    if not deleted then
+                        deleted = true
+                        del_win(status.preview_win)
+                        del_win(status.preview_border_win)
+                    end
+                    reload_theme(entry.value)
+                end
+            }
+        else
+            -- show current buffer content in previewer
+            previewer =
+                previewers.new_buffer_previewer {
+                get_buffer_by_name = function()
+                    return bufname
+                end,
+                define_preview = function(self, entry)
+                    if vim.loop.fs_stat(bufname) then
+                        conf.buffer_previewer_maker(bufname, self.state.bufnr, {bufname = self.state.bufname})
+                    else
+                        local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+                        vim.api.nvim_buf_set_lines(self.state.bufnr, 0, -1, false, lines)
+                    end
+                    reload_theme(entry.value)
+                end
+            }
+        end
+
+        local picker =
+            pickers.new(
+            {
+                prompt_title = "Set NvChad color",
+                finder = finders.new_table(themes),
+                previewer = previewer,
+                sorter = conf.generic_sorter(opts),
+                attach_mappings = function()
+                    actions.select_default:replace(
+                        -- if a entry is selected, change current_theme to that
+                        function(prompt_bufnr)
+                            local selection = action_state.get_selected_entry()
+                            new_theme = selection.value
+                            change = true
+                            actions.close(prompt_bufnr)
+                        end
+                    )
+                    return true
+                end
+            }
+        )
+
+        -- rewrite picker.close_windows
+        local close_windows = picker.close_windows
+        picker.close_windows = function(status)
+            close_windows(status)
+            -- now apply the theme, if success, then ask for default theme change
+            local final_theme
+            if change then
+                final_theme = new_theme
+            else
+                final_theme = current_theme
+            end
+
+            if reload_theme(final_theme) then
+                if change then
+                    -- ask for confirmation to set as default theme
+                    local ans = string.lower(vim.fn.input("Set " .. new_theme .. " as default theme ? [y/N] ")) == "y"
+                    if ans then
+                        local_utils.change_theme(current_theme, final_theme)
+                    else
+                        -- will be used in restoring nvchad theme var
+                        final_theme = current_theme
+                    end
+                end
+                -- open a buffer and close it to reload the statusline
+                vim.cmd("new|bwipeout")
+            end
+            -- set nvchad_theme global var
+            vim.g.nvchad_theme = current_theme
+        end
+        -- launch the telescope picker
+        picker:find()
+    else
+        print("No themes found in " .. themes_folder)
+    end
+end
+
+-- register theme swticher as themes to telescope
+local present, telescope = pcall(require, "telescope")
+if present then
+    return telescope.register_extension {
+        exports = {
+            themes = M.theme_switcher
+        }
+    }
+else
+    error "Cannot find telescope!"
+end

lua/theme.lua

@@ -1,9 +1,9 @@
 local chad_theme = require("user_config").ui.theme
 
 vim.g.nvchad_theme = chad_theme
-local present2, base16 = pcall(require, "base16")
+local present, base16 = pcall(require, "base16")
 
-if present2 then
+if present then
     base16(base16.themes[chad_theme], true)
     require "highlights"
     return true

lua/utils.lua

@@ -0,0 +1,96 @@
+local M = {}
+
+-- reload a plugin ( will try to load even if not loaded)
+-- can take a string or list ( table )
+M.reload_plugin = function(plugins)
+    local function _reload_plugin(plugin)
+        local loaded = package.loaded[plugin]
+        if loaded then
+            package.loaded[plugin] = nil
+        end
+        if not pcall(require, plugin) then
+            error("Error: Cannot load " .. plugin .. " plugin!")
+        end
+    end
+
+    if type(plugins) == "string" then
+        _reload_plugin(plugins)
+    elseif type(plugins) == "table" then
+        for _, plugin in ipairs(plugins) do
+            _reload_plugin(plugin)
+        end
+    end
+end
+
+-- return a table of available themes
+M.list_themes = function(return_type)
+    local themes = {}
+    -- folder where theme files are stored
+    local themes_folder = vim.fn.stdpath("config") .. "/lua/themes"
+    -- list all the contents of the folder and filter out files with .lua extension, then append to themes table
+    local fd = vim.loop.fs_scandir(themes_folder)
+    if fd then
+        while true do
+            local name, typ = vim.loop.fs_scandir_next(fd)
+            if name == nil then
+                break
+            end
+            if typ ~= "directory" and string.find(name, ".lua") then
+                -- return the table values as keys if specified
+                if return_type == "keys_as_value" then
+                    themes[vim.fn.fnamemodify(name, ":r")] = true
+                else
+                    table.insert(themes, vim.fn.fnamemodify(name, ":r"))
+                end
+            end
+        end
+    end
+    return themes
+end
+
+-- 1st arg - r or w
+-- 2nd arg - file path
+-- 3rd arg - content if 1st arg is w
+-- return file data on read, nothing on write
+M.file = function(mode, filepath, content)
+    local data
+    local fd = assert(vim.loop.fs_open(filepath, mode, 438))
+    local stat = assert(vim.loop.fs_fstat(fd))
+    if stat.type ~= "file" then
+        data = false
+    else
+        if mode == "r" then
+            data = assert(vim.loop.fs_read(fd, stat.size, 0))
+        else
+            assert(vim.loop.fs_write(fd, content, 0))
+            data = true
+        end
+    end
+    assert(vim.loop.fs_close(fd))
+    return data
+end
+
+-- 1st arg as current theme, 2nd as new theme
+M.change_theme = function(current_theme, new_theme)
+    if current_theme == nil or new_theme == nil then
+        error "Provide current and new theme name"
+    end
+    if current_theme == new_theme then
+        return
+    end
+
+    local file = vim.fn.stdpath("config") .. "/lua/user_config.lua"
+    -- store in data variable
+    local data = assert(M.file("r", file))
+    local find = "theme = .?" .. current_theme .. ".?"
+    local replace = 'theme = "' .. new_theme .. '"'
+    local content = string.gsub(data, find, replace)
+    -- see if the find string exists in file
+    if content == data then
+        error("Cannot change default theme with " .. new_theme .. ", edit " .. file .. " manually")
+    else
+        assert(M.file("w", file, content))
+    end
+end
+
+return M