clink (https://chrisant996.github.io/clink/) plugin for fnm (https://github.com/Schniz/fnm)

fnm.lua

if (clink.version_encoded or 0) < 10020030 then
	error("fnm requires a newer version of Clink; please upgrade to Clink v1.2.30 or later.")
end

-- ANSI escape codes for colors and styles
local RED   = "\27[31m"
local YELLOW = "\27[33m"
local CYAN = "\27[36m"
local RESET = "\27[0m"
local BOLD  = "\27[1m"
local ITAL  = "\27[3m"

local function prompt_install()
    local handle = io.popen("fnm use --silent-if-unchanged 2>&1")
    local t = handle:read("*a")
    handle:close()

    if not t or t == "" then return end

    -- Check for missing version error
    local version = t:match("error: Requested version ([^%s]+) is not currently installed")
    if version then
        version = tostring(version)
        io.write(
            RED, "Can't find an installed Node version matching ", ITAL, version, RESET, ".\n"
        )
        io.write(
            YELLOW, "Do you want to install it? ", BOLD, "answer", RESET, YELLOW, " [y/N]: ", RESET
        )
        local answer = io.read()
        if answer and answer:lower() == "y" then
            os.execute("fnm use --silent-if-unchanged --install-if-missing")
        end
        return
    end

    -- Success: output contains "Using Node v..."
    local node_version = t:match("Using Node (v%d+%.%d+%.%d+)")
    if node_version then
        io.write("Using Node ", CYAN, node_version, RESET, "\n")
        return
    end

    -- All other cases are errors
    error("fnm use --silent-if-unchanged failed: " .. t)
end

local function parse_fnm_env()
    local handle = io.popen('fnm env --use-on-cd 2>nul')
    if not handle then return nil end
    local out = handle:read("*a")
    handle:close()

    local env = {}
    for line in out:gmatch("[^\r\n]+") do
        -- Matches: set VAR=VALUE  (quotes rarely used, but handle if present)
        local var, value = line:match("^[Ss][Ee][Tt]%s+([^=]+)=(.*)$")
        if var and value then
            value = value:gsub('^"(.*)"$', '%1') -- remove surrounding quotes if present
            env[var:match("^%s*(.-)%s*$")] = value -- trim spaces from var
        end
    end
    return env, out
end

local function check_and_use_fnm()
    -- Check FNM_VERSION_FILE_STRATEGY environment variable
    local fnm_strategy = os.getenv("FNM_VERSION_FILE_STRATEGY")
    
    -- -- Check if we should use recursive strategy
    if fnm_strategy == "recursive" then
        prompt_install()
    else
        -- Check for .nvmrc file
        local nvmrc = io.open(".nvmrc", "r")
        if nvmrc ~= nil then
            io.close(nvmrc)
            prompt_install()
        else
            -- Check for .node-version file
            local node_version = io.open(".node-version", "r")
            if node_version ~= nil then
                io.close(node_version)
                prompt_install()
            end
        end
    end
end

local function setup_fnm()
    local env, raw = parse_fnm_env()
    if not env or not raw then return end

    for var, value in pairs(env) do
        os.setenv(var, value)
    end

    -- doskey replacement
    clink.onbeginedit(check_and_use_fnm)

    -- remove fnm symlinks on exit
    clink.onendedit(function(line)
        if line:match("^exit") then
            local path = os.getenv("FNM_MULTISHELL_PATH")
            if path then
                os.rmdir(path)
            end
        end
    end)
end

setup_fnm()