Documentation added

docs/getting-started.md

@@ -0,0 +1,103 @@
+# Getting started
+
+## Project structure
+
+```
+my_project/
+├── main.py
+├── config.ini
+└── modules/
+    ├── cmds_foo.py
+    └── cmds_bar.py
+```
+
+## Configuration file
+
+```ini
+[general]
+default = foo          # default module (used when no module is specified)
+# methods_prefix = cmd_   # optional: override command method prefix
+# modules_prefix = cmds_  # optional: override module file prefix
+
+[foo]
+alias = f              # optional: short name for the module
+my_setting = value     # any key accessible via self.config.get("my_setting")
+
+[bar]
+# ...
+```
+
+## Writing a module
+
+```python
+from appengine import Commands, AppEngineException, AEErrs
+
+class Foo(Commands):
+    # Set to True to run this module in a background thread
+    threaded = False
+
+    # Declare dependencies on other modules
+    # dependencies = ["bar"]          # list form  → self.bar = cmods["bar"]
+    # dependencies = {"b": "bar"}     # dict form  → self.b   = cmods["bar"]
+
+    def cmd_add(self, a: float, b: float):
+        """Add two numbers.
+
+        Args:
+            a: First operand.
+            b: Second operand.
+
+        Returns:
+            float: The sum of *a* and *b*.
+        """
+        return float(a) + float(b)
+
+    def cmd_fail(self):
+        """Demonstrate structured error reporting."""
+        raise AppEngineException(AEErrs.INVALID_PARAMS, "Nothing to do here")
+
+    def free(self):
+        # Close connections, files, etc.
+        pass
+```
+
+## Threaded module
+
+```python
+import time
+from appengine import Commands
+
+class Worker(Commands):
+    threaded = True   # will be started as a Thread
+
+    def run(self):
+        while not self.stopped:
+            self.info("tick")
+            time.sleep(1)
+
+    def free(self):
+        self.info("worker cleaned up")
+```
+
+## Dispatching commands
+
+Commands are dispatched via `execute_command(module, method, *args)`:
+
+```python
+success, result = my_commands_instance.execute_command("foo", "add", 1, 2)
+```
+
+### Built-in help
+
+| Call | Result |
+|------|--------|
+| `execute_command("", "help")` | List of all modules |
+| `execute_command("", "help", "foo")` | List of commands in `foo` |
+| `execute_command("", "help", "foo.add")` | Docstring of `foo.add` |
+
+## Error handling
+
+Commands return `(success: bool, result)`.  
+On error, `result` is a tuple `(error_code: int, message: str)`.
+
+Error codes follow the JSON-RPC convention (see `AEErrs`).