added state to cli

mod.ts

@@ -1,13 +1,100 @@
 import { Command } from "https://deno.land/x/cliffy@v0.25.7/command/mod.ts";
+import { DB } from "https://deno.land/x/sqlite/mod.ts";
+import {join} from "https://deno.land/std@0.178.0/path/mod.ts";
+
+// for the demo, we will place the state in the /tmp instead of $HOME
+const HOME_DIRECTORY = '/tmp';
+const CLI_STATE_DIRECTORY = join(HOME_DIRECTORY, 'deno-cli-example');
+
+// the CLI will need read and write access to /tmp/deno-cli-example directory
+await Deno.mkdir(CLI_STATE_DIRECTORY, {recursive: true});
+const MAIN_DB_FILE = join(CLI_STATE_DIRECTORY, 'state.sqlite');
 
 
-function helloWorld(options, ...args) {
-    console.log("hello world");
+/**
+ * Create tables in the database.  This function is a
+ * trivial data migration algorithm.
+ */
+function initDB(){
+  const db = new DB(MAIN_DB_FILE);
+  const init_db = `
+  CREATE TABLE IF NOT EXISTS usernames (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      username TEXT,
+      creation_ts DATETIME DEFAULT CURRENT_TIMESTAMP
+  )
+  `;
+  try {
+    db.execute(init_db);
+  } finally {
+    db.close();
+  }
 }
 
+/**
+ * Returns the latest username saved in the state.
+ */
+function getUsernameFromDB(){
+  const db = new DB(MAIN_DB_FILE);
+  try {
+    return db.query(`SELECT username 
+                     FROM usernames 
+                     ORDER BY creation_ts 
+                     DESC LIMIT 1`)[0]
+  } finally {
+    db.close();
+  }
+}
+
+/**
+ * Set the passed username in the database.
+ */
+function setUsernameInDB(username: string){
+  const db = new DB(MAIN_DB_FILE);
+  try {
+    return db.query("INSERT INTO usernames (username) VALUES (?)", [username])
+  } finally {
+    db.close();
+  }
+}
+
+function getUsernameOrDefault(name?: string): string{
+  return name || getUsernameFromDB() || 'no username set yet.';
+}
+
+/**
+ * Calls httpbin.org/get with the username as argument.
+ */
+async function getFromService(options){
+  const username = getUsernameOrDefault(options.usermame);
+  const encodedUsername = encodeURIComponent(username);
+  const url = `https://httpbin.org/get?username=${encodedUsername}`;
+  const response = await fetch();
+  console.log(await response.json());
+}
+
+async function setProperties(options){
+  if(options.username){
+    setUsernameInDB(options.username);
+  }
+}
+
+initDB();
 await new Command()
   .name("deno-cli-example")
   .version("0.1.0")
   .description("Example of a deno CLI.")
-  .action(helloWorld)
+  .command('call-service')
+  .description('Example of a real use case. call-service will called '
+                + 'https://httpbin.org/get with username passed as parameter.')
+  .option("--username <username>", 
+          'username to use in the service call. If no username specified, the '
+           + ' persisted username  will be used.')
+  .action(getFromService)
+  .command('set-properties')
+  .description('Persist properties to state. Persisted properties will then '
+                + 'be used as default in other commands')
+  .option("--username <username>", "Set the default username property.", 
+          {required: true})
+  .action(setProperties)
   .parse(Deno.args);