feat: Add translated imap-codec Python examples

This adds Python examples `parse_command`, `parse_greeting` and
`parse_response`, which are translated from the Rust examples available
for `imap-codec`.

bindings/imap-codec-python/examples/common/__init__.py

@@ -0,0 +1,42 @@
+import sys
+from enum import Enum
+from typing import Optional
+
+COLOR_SERVER = "\x1b[34m"
+COLOR_CLIENT = "\x1b[31m"
+RESET = "\x1b[0m"
+
+
+class Role(Enum):
+    Client = 1
+    Server = 2
+
+
+def read_more(buffer: bytearray, role: Role):
+    if not buffer:
+        prompt = "C: " if role == Role.Client else "S: "
+    else:
+        prompt = ".. "
+
+    line = read_line(prompt, role)
+
+    # If `read_line` returns `None`, standard input has been closed.
+    if line is None or line.strip() == "exit":
+        print("Exiting.")
+        sys.exit(0)
+
+    buffer += line.encode()
+
+
+def read_line(prompt: str, role: Role) -> Optional[str]:
+    color = COLOR_CLIENT if role == Role.Client else COLOR_SERVER
+
+    try:
+        line = input(f"{prompt}{color}")
+    except EOFError:
+        # Standard input has been closed.
+        return None
+    finally:
+        print(RESET, end=None)
+
+    return line + "\r\n"

bindings/imap-codec-python/examples/parse_command.py

@@ -0,0 +1,53 @@
+from common import COLOR_SERVER, RESET, Role, read_more
+from imap_codec import CommandCodec, DecodeFailed, DecodeIncomplete, DecodeLiteralFound
+
+WELCOME = r"""# Parsing of IMAP commands
+
+"C:" denotes the client,
+"S:" denotes the server, and
+".." denotes the continuation of an (incomplete) command, e.g., due to the use of an IMAP literal.
+
+Note: "\n" will be automatically replaced by "\r\n".
+
+--------------------------------------------------------------------------------------------------
+
+Enter IMAP command (or "exit").
+"""
+
+
+def main():
+    print(WELCOME)
+
+    buffer = bytearray()
+
+    while True:
+        # Try to parse the first command in `buffer`.
+        try:
+            remaining, command = CommandCodec.decode(bytes(buffer))
+            # Parser succeeded.
+            # Do something with the command ...
+            print(command)
+            # ... and proceed with the remaining data.
+            buffer = bytearray(remaining)
+        except DecodeIncomplete:
+            # Parser needs more data.
+            # Read more data.
+            read_more(buffer, Role.Client)
+        except DecodeLiteralFound:
+            # Parser needs more data, and a command continuation request is expected.
+            # Simulate literal acknowledgement ...
+            print(f"S: {COLOR_SERVER}+ {RESET}")
+
+            # ... and read more data.
+            read_more(buffer, Role.Client)
+        except DecodeFailed:
+            # Parser failed.
+            print("Error parsing command.")
+            print("Clearing buffer.")
+
+            # Clear the buffer and proceed with loop.
+            buffer.clear()
+
+
+if __name__ == "__main__":
+    main()

bindings/imap-codec-python/examples/parse_greeting.py

@@ -0,0 +1,44 @@
+from common import Role, read_more
+from imap_codec import DecodeFailed, DecodeIncomplete, GreetingCodec
+
+WELCOME = r"""# Parsing of IMAP greetings
+
+"S:" denotes the server.
+
+Note: "\n" will be automatically replaced by "\r\n".
+
+--------------------------------------------------------------------------------------------------
+
+Enter IMAP greeting (or "exit").
+"""
+
+
+def main():
+    print(WELCOME)
+
+    buffer = bytearray()
+
+    while True:
+        # Try to parse the first greeting in `buffer`.
+        try:
+            remaining, greeting = GreetingCodec.decode(bytes(buffer))
+            # Parser succeeded.
+            # Do something with the greeting ...
+            print(greeting)
+            # ... and proceed with the remaining data.
+            buffer = bytearray(remaining)
+        except DecodeIncomplete:
+            # Parser needs more data.
+            # Read more data.
+            read_more(buffer, Role.Server)
+        except DecodeFailed:
+            # Parser failed.
+            print("Error parsing greeting.")
+            print("Clearing buffer.")
+
+            # Clear the buffer and proceed with loop.
+            buffer.clear()
+
+
+if __name__ == "__main__":
+    main()

bindings/imap-codec-python/examples/parse_response.py

@@ -0,0 +1,55 @@
+from common import Role, read_more
+from imap_codec import DecodeFailed, DecodeIncomplete, DecodeLiteralFound, ResponseCodec
+
+WELCOME = r"""# Parsing of IMAP responses
+
+"S:" denotes the server, and
+".." denotes the continuation of an (incomplete) response, e.g., due to the use of an IMAP literal.
+
+Note: "\n" will be automatically replaced by "\r\n".
+
+--------------------------------------------------------------------------------------------------
+
+Enter IMAP response (or "exit").
+"""
+
+
+def main():
+    print(WELCOME)
+
+    buffer = bytearray()
+
+    while True:
+        # Try to parse the first response in `buffer`.
+        try:
+            remaining, response = ResponseCodec.decode(bytes(buffer))
+            # Parser succeeded.
+            # Do something with the response ...
+            print(response)
+            # ... and proceed with the remaining data.
+            buffer = bytearray(remaining)
+        except DecodeIncomplete:
+            # Parser needs more data.
+            # Read more data.
+            read_more(buffer, Role.Server)
+        except DecodeLiteralFound:
+            # Parser needs more data.
+            #
+            # A client MUST receive any literal and can't reject it. However, if the literal is too
+            # large, the client would have the (semi-optimal) option to still *read it* but discard
+            # the data chunk by chunk. It could also close the connection. This is why we have this
+            # option.
+            #
+            # Read more data.
+            read_more(buffer, Role.Server)
+        except DecodeFailed:
+            # Parser failed.
+            print("Error parsing response.")
+            print("Clearing buffer.")
+
+            # Clear the buffer and proceed with loop.
+            buffer.clear()
+
+
+if __name__ == "__main__":
+    main()