"""Regression tests for _rewrite_compound_background.

Context: bash parses ``A && B &`` as ``(A && B) &`` — it forks a subshell
for the compound and backgrounds the subshell. Inside the subshell, B
runs foreground, so the subshell waits for B. When B never exits on its
own (HTTP servers, ``yes > /dev/null``, etc.), the subshell is stuck in
``wait4`` forever and leaks as an orphan process. Pre-fix, we saw this
pattern leak processes across the fleet (vela, sal, combiagent).

The rewriter fixes this by wrapping the tail in a brace group —
``A && { B & }`` — so B runs as a simple backgrounded command inside
the current shell. No subshell fork, no wait.
"""


from tools.terminal_tool import _rewrite_compound_background as rewrite


class TestRewrites:
    """Commands that trigger the subshell-wait bug MUST be rewritten."""

    def test_simple_and_background(self):
        assert rewrite("A && B &") == "A && { B & }"

    def test_or_background(self):
        assert rewrite("A || B &") == "A || { B & }"


    def test_multiple_rewrites_in_one_script(self):
        cmd = "A && B &\nfalse || C &"
        assert rewrite(cmd) == "A && { B & }\nfalse || { C & }"


class TestPreserved:
    """Commands that DON'T have the bug MUST pass through unchanged."""

    def test_simple_background(self):
        # No compound — just background a single command. Works fine as-is.
        assert rewrite("sleep 5 &") == "sleep 5 &"

    def test_plain_server_background(self):
        assert rewrite("python3 -m http.server 0 &") == "python3 -m http.server 0 &"


    def test_whitespace_only(self):
        assert rewrite("   \n\t") == "   \n\t"


class TestRedirectsNotConfused:
    """``&>``, ``2>&1``, ``>&2`` must not be mistaken for background ``&``."""

    def test_amp_gt_redirect_alone(self):
        assert rewrite("echo hi &>/dev/null") == "echo hi &>/dev/null"


    def test_gt_amp_inside_compound(self):
        cmd = "A && B 2>&1 &"
        assert rewrite(cmd) == "A && { B 2>&1 & }"


class TestQuotingAndParens:
    """Shell metacharacters inside quotes/parens must not be parsed as operators."""

    def test_and_and_inside_single_quotes(self):
        cmd = "echo 'A && B &'"
        assert rewrite(cmd) == "echo 'A && B &'"


    def test_backslash_escaped_ampersand(self):
        # Escaped & is not a background operator.
        cmd = r"echo A \&\& B"
        assert rewrite(cmd) == cmd

    def test_comment_line_not_rewritten(self):
        cmd = "# A && B &\nC"
        assert rewrite(cmd) == "# A && B &\nC"


class TestIdempotence:
    """Running the rewriter twice should be a no-op on its own output."""

    def test_already_rewritten(self):
        once = rewrite("A && B &")
        twice = rewrite(once)
        assert once == twice
        assert twice == "A && { B & }"

    def test_multiline_idempotent(self):
        once = rewrite("cd /tmp && server &\nsleep 1")
        assert rewrite(once) == once


class TestEdgeCases:
    def test_only_chain_op_no_second_command(self):
        # Malformed input: bash would error, we shouldn't crash or rewrite.
        cmd = "A && &"
        # Don't assert a specific output; just don't raise.
        rewrite(cmd)


    def test_tabs_between_tokens(self):
        assert rewrite("A\t&&\tB\t&") == "A\t&&\t{ B\t& }"