feat(cli): chat — read a group's last messages, post one

chat GROUP prints the last ten messages, oldest first (-N, as head -N, or
-n N for another count, paging back past the node's 200), and -m posts one
(- reads it from stdin). The application's construction: every epoch key
from chat_keys_req, a post sealed under the current epoch through the
device subkey and signed with this machine's key on the node, the sender's
name inside the envelope; nothing sent past the node's ciphertext bound.
A stored message is read signature first, then key, then content, and one
that fails is shown as unreadable, never dropped. Not done here: the Tier 2
roster check on the signing device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/packages/meshbay-cli/tests/test_cli_actions.py b/packages/meshbay-cli/tests/test_cli_actions.py
index e06fb9c..5443d9b 100644
--- a/packages/meshbay-cli/tests/test_cli_actions.py
+++ b/packages/meshbay-cli/tests/test_cli_actions.py
@@ -510,6 +510,51 @@ def test_search_finds_across_groups_once_per_file(hub, monkeypatch, capsys):
     assert main("search", "beach") == 0
 
 
+def test_chat_reads_the_last_messages_and_posts(node, monkeypatch, capsys):
+    from meshbay_cli.commands import chat
+
+    async def open_group(account, group):
+        return node.session()
+    monkeypatch.setattr(chat, "open_group", open_group)
+
+    for i in range(1, 231):                       # more than one page of the node's
+        node.say(f"message {i}")
+    node.say("forged", forge=True)
+    node.say("two lines\nand an \x1b[31m escape")
+    node.chat_epochs[2] = b"\x09" * 32
+    node.say("from an epoch this member was not given", epoch=2)
+    del node.chat_epochs[2]
+
+    assert main("chat", "Family") == 0
+    lines = capsys.readouterr().out.splitlines()
+    assert len(lines) == 11 and lines[0].endswith("bob-test: message 224")
+    assert lines[7].endswith("bob-test: [this message cannot be read: signature]")
+    assert lines[8].endswith("bob-test: two lines")
+    assert lines[9].strip() == "and an \\x1b[31m escape"            # shown, never run
+    assert "cannot be read: no key for its epoch" in lines[10]
+
+    assert main("chat", "-5", "Family") == 0
+    assert capsys.readouterr().out.splitlines()[0].endswith("message 229")
+    assert main("--json", "chat", "Family", "-n", "300") == 0     # paged back
+    got = json.loads(capsys.readouterr().out)
+    assert len(got) == 233 and got[0]["text"] == "message 1"
+    assert got[230]["unreadable"] == "signature"
+
+    assert main("chat", "Family", "-m", "hello from the terminal") == 0
+    assert "Posted to Family@alice-test" in capsys.readouterr().err
+    monkeypatch.setattr("sys.stdin", io.StringIO("piped\n"))
+    assert main("chat", "Family", "-m", "-") == 0
+    capsys.readouterr()
+    assert main("chat", "-2", "Family") == 0
+    out = capsys.readouterr().out.splitlines()
+    assert out[0].endswith(f"{USERNAME}: hello from the terminal")
+    assert out[1].endswith(f"{USERNAME}: piped")
+
+    assert main("chat", "Family", "-m", "   ") == 1
+    assert main("chat", "Family", "-m", "x" * 70_000) == 1          # over the node's bound
+    assert main("chat", "-0", "Family") == 1
+
+
 def test_every_action_is_run_here():
     """Runs last in this module: every action the parser knows was run above."""
     assert RUN == set(cli.ACTIONS), f"never run: {set(cli.ACTIONS) - RUN}"