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/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