Update api to use chain and call

Much sexier than __call__

commands.py

@@ -1,52 +1,46 @@
-from formatters import Printer
 from io import StringIO
 
 
 class BaseCommand(object):
-    def __init__(self, args):
+    """Commands can be used to chain the execution of multiple programs
+    together. You can chain multiple commands together using commands
+
+    For example:
+    ls = RawCommand(["ls"])
+    grep = RawCommand(["grep", "potato"])
+    printer = Printer()
+    ls.chain(grep).chain(printer).call()
+    """
+
+    def __init__(self, args=None):
         self.cmd_args = args
-    def __call__(self, *args, **kwargs):
-        raise NotImplementedError(
-            "BaseCommands must be callable and return a generator")
+        self.prev_cmd = None
 
+    def call(self, *args, **kwargs):
+        """Implicitly calls any chained commands, returning a function
+        to make an input generator."""
+        raise NotImplementedError("Must implement call")
 
-class NoneCommand(BaseCommand):
+    def get_input_generator(self):
+        """Gets the input generator from the previous command, if it
+        exists. If it doesn't exist, we just return an empy list so that
+        when you iterate over it, it does nothing."""
+        if self.prev_cmd is not None:
+            make_input_generator = self.prev_cmd.call()
+            input_generator = make_input_generator()
+        else:
+            input_generator = []
+        return input_generator
 
-    def __call__(self, *args, **kwargs):
-        return []
-
-
-
-class RawCommand(BaseCommand):
-    """Fallback raw command that just invokes an existing Unix utility program
-    with the builtin subprocess module. Each output object is just a tree node
-    whose data is a simple string."""
-
-    def __init__(self, cmd, input_generator=[]):
-        self.input_generator = input_generator
-        self.cmd = cmd
-
-    def __call__(self, input_generator=[], *args, **kwargs):
-        import subprocess
-        try:
-            p = subprocess.Popen(self.cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
-            def output_generator():
-                input_str = b""
-                for line in input_generator:
-                    input_str += line + b'\n'
-                outs, errs = p.communicate(input_str)
-                if outs:
-                    yield outs
-
-            return output_generator()
-        except:
-            import traceback
-            traceback.print_exc()
-        return []
+    def chain(self, cmd):
+        """Chains a command to another command, returning the other command"""
+        cmd.prev_cmd = self
+        return cmd
 
 
 registered_cmds = []
 
 def register_cmd(cls):
+    """Decorator for putting all of the commands in one nice place."""
     registered_cmds.append(cls.__name__)
     return cls

example_cmd.py

@@ -1,19 +1,33 @@
 from commands import BaseCommand, register_cmd
 
+
 @register_cmd
 class example_cmd(BaseCommand):
-    def __call__(self, *args, **kwargs):
+    """Simple command that just returns 'example' and 'command'. Does
+    nothing at all with the input."""
+
+    def call(self, *args, **kwargs):
         def output_generator():
             yield b'example'
             yield b'command'
-        return output_generator()
+        return output_generator
 
 
 @register_cmd
 class echo(BaseCommand):
-    def __call__(self,*args,**kwargs):
-        def output_generator():
-            for line in self.cmd_args:
-                yield line.encode('utf-8')
-        return output_generator()
+    """Echoes anything from the command line arguments as well as input
+    from the previous command."""
+
+    def __init__(self, args):
+        super(echo, self).__init__()
+        self.args = args
+
+    def call(self,*args,**kwargs):
+        input_generator = self.get_input_generator()
+        def output_generator():
+            for args in self.args:
+                yield args.encode("utf-8")
+            for line in input_generator:
+                yield line
+        return output_generator
 

formatters.py

@@ -1,23 +1,12 @@
-class Formatter(object):
-    """Formatters are callable objects who always accept a generator.
-    The generator represents the output stream of an executing program.
-    Formatters are special commands which produce no output themselves.
-    Instead, they always write to the standard out of the program. """
-
-    def __init__(self, *args, **kwargs):
-        # Always require no arguments
-        pass
-
-    def __call__(self, input_generator):
-        raise NotImplementedError(
-            "You must extend a Formatter and implement the __call__ method")
+from commands import BaseCommand
 
 
-class Printer(Formatter):
+class Printer(BaseCommand):
     """Simple formatter which accepts any object from the input
     generator and simply prints it as if it were a string."""
 
-    def __call__(self, input_generator):
+    def call(self):
+        input_generator = self.get_input_generator()
         for line in input_generator:
             print(str(line.decode('utf-8')))
         return None

main.py

@@ -1,4 +1,5 @@
-from commands import RawCommand, registered_cmds
+from commands import registered_cmds
+from raw_commands import RawCommand
 from formatters import Printer
 from example_cmd import example_cmd, echo
 
@@ -46,10 +47,10 @@ def handle_input(prompt=""):
     else:
         cmds = parse_cmds(raw)
         cmds.append("Printer()")
-        mangled_input = ""
-        for cmd in reversed(cmds):
-            mangled_input += cmd + "("
-        mangled_input += ")" * len(cmds)
+        mangled_input = cmds[0]
+        for cmd in cmds[1:]:
+            mangled_input += ".chain(" + cmd + ")"
+        mangled_input += ".call()"
         print("[DEBUG]: evaluating Python: ", mangled_input)
         return mangled_input
 

raw_commands.py

@@ -0,0 +1,31 @@
+from formatters import Printer
+from commands import BaseCommand
+
+
+class RawCommand(BaseCommand):
+    """Fallback raw command that just invokes an existing Unix utility program
+    with the builtin subprocess module. Each output object is just a tree node
+    whose data is a simple string."""
+
+    def __init__(self, cmd):
+        super(RawCommand, self).__init__()
+        self.cmd = cmd
+
+    def call(self, *args, **kwargs):
+        input_generator = self.get_input_generator()
+        import subprocess
+        try:
+            p = subprocess.Popen(self.cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+            def make_output_generator():
+                input_str = b""
+                for line in input_generator:
+                    input_str += line + b'\n'
+                outs, errs = p.communicate(input_str)
+                if outs:
+                    yield outs
+
+            return make_output_generator
+        except:
+            import traceback
+            traceback.print_exc()
+        return []