"""Tests for the QMP collector against an in-process fake QMP server.

The fake speaks just enough QMP to exercise:
  - the greeting + qmp_capabilities handshake
  - query-status
  - query-blockstats
  - query-stats target=vm
  - error responses
  - async events interleaved with command responses
"""

from __future__ import annotations

import json
import socket
import tempfile
import threading
import time
from pathlib import Path
from typing import Any

import pytest

from collectors import qmp


# ---------------------------------------------------------------------------
# Fake QMP server
# ---------------------------------------------------------------------------


class FakeQMPServer(threading.Thread):
    """Single-connection fake. Each line received from the client is
    parsed as JSON; we look up ``execute`` in ``responses`` and emit
    the configured reply. Optionally interleaves an async event before
    the response."""

    def __init__(
        self,
        socket_path: Path,
        *,
        responses: dict[str, Any] | None = None,
        emit_event_before: set[str] | None = None,
    ) -> None:
        super().__init__(daemon=True)
        self.socket_path = socket_path
        self.responses = responses or {}
        self.emit_event_before = emit_event_before or set()
        self.received: list[dict] = []
        self._stop = threading.Event()
        self._sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        self._sock.bind(str(socket_path))
        self._sock.listen(1)
        self._sock.settimeout(5.0)

    def run(self) -> None:
        try:
            conn, _ = self._sock.accept()
        except socket.timeout:
            return
        conn.settimeout(5.0)
        try:
            # Greeting
            conn.sendall(b'{"QMP": {"version": {"qemu": {"major":9,"minor":0,"micro":0}}, "capabilities": []}}\n')
            buf = b""
            while not self._stop.is_set():
                try:
                    chunk = conn.recv(4096)
                except socket.timeout:
                    if self._stop.is_set():
                        return
                    continue
                if not chunk:
                    return
                buf += chunk
                while b"\n" in buf:
                    line, _, buf = buf.partition(b"\n")
                    if not line.strip():
                        continue
                    msg = json.loads(line)
                    self.received.append(msg)
                    cmd = msg.get("execute")
                    if cmd == "qmp_capabilities":
                        conn.sendall(b'{"return": {}}\n')
                        continue
                    if cmd in self.emit_event_before:
                        conn.sendall(b'{"event": "STOP", "timestamp": {"seconds": 1, "microseconds": 0}}\n')
                    if cmd in self.responses:
                        resp = self.responses[cmd]
                        conn.sendall((json.dumps(resp) + "\n").encode())
                    else:
                        conn.sendall(b'{"error": {"class": "CommandNotFound", "desc": "unknown"}}\n')
        finally:
            conn.close()

    def shutdown(self) -> None:
        self._stop.set()
        try:
            self._sock.close()
        except OSError:
            pass


@pytest.fixture
def qmp_server(tmp_path: Path):
    sock_path = tmp_path / "qmp.sock"
    return sock_path


# ---------------------------------------------------------------------------
# Client tests
# ---------------------------------------------------------------------------


def test_connect_negotiates_capabilities(qmp_server: Path) -> None:
    server = FakeQMPServer(qmp_server)
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        greeting = client.connect()
        assert "version" in greeting
    finally:
        client.close()
        server.shutdown()
    # Server saw exactly the qmp_capabilities call.
    assert any(m.get("execute") == "qmp_capabilities" for m in server.received)


def test_execute_returns_payload(qmp_server: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "query-status": {"return": {"status": "running", "running": True}},
        },
    )
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        out = client.execute("query-status")
        assert out == {"status": "running", "running": True}
    finally:
        client.close()
        server.shutdown()


def test_execute_skips_async_events_before_response(qmp_server: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "query-status": {"return": {"status": "running", "running": True}},
        },
        emit_event_before={"query-status"},
    )
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        out = client.execute("query-status")
        assert out["running"] is True
    finally:
        client.close()
        server.shutdown()


def test_execute_raises_on_qmp_error(qmp_server: Path) -> None:
    server = FakeQMPServer(qmp_server)  # no responses → server sends error
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        with pytest.raises(qmp.QMPError):
            client.execute("totally-fake-command")
    finally:
        client.close()
        server.shutdown()


# ---------------------------------------------------------------------------
# Row builder tests
# ---------------------------------------------------------------------------


def test_collect_once_assembles_full_row(qmp_server: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "query-status": {"return": {"status": "running", "running": True}},
            "query-blockstats": {"return": [{
                "device": "virtio0",
                "stats": {
                    "rd_operations": 12, "wr_operations": 4,
                    "rd_bytes": 49152, "wr_bytes": 16384,
                    "flush_operations": 1,
                },
            }]},
            "query-stats": {"return": [{"stats": [
                {"name": "halt_exits", "value": 17000},
                {"name": "io_exits",   "value": 942},
                {"name": "string-skipped", "value": "not-an-int"},
            ]}]},
        },
    )
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        row = qmp.collect_once(client, t_mono_origin_ns=time.monotonic_ns())
    finally:
        client.close()
        server.shutdown()

    assert row["source"] == "host_qmp"
    assert row["available_in_deployment"] is False
    assert row["vm_running"] is True
    assert row["blockstats"]["virtio0"]["rd_bytes"] == 49152
    assert row["blockstats"]["virtio0"]["flush_ops"] == 1
    assert row["kvm_stats"]["halt_exits"] == 17000
    assert "string-skipped" not in row["kvm_stats"]


def test_collect_once_tolerates_missing_query_stats(qmp_server: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "query-status": {"return": {"status": "running", "running": True}},
            "query-blockstats": {"return": []},
            # query-stats deliberately absent → server returns CommandNotFound
        },
    )
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        row = qmp.collect_once(client, t_mono_origin_ns=time.monotonic_ns())
    finally:
        client.close()
        server.shutdown()

    # Older qemu without query-stats: row still exists, kvm_stats absent.
    assert "kvm_stats" not in row
    assert row["vm_running"] is True
    assert row["blockstats"] == {}


# ---------------------------------------------------------------------------
# run_loop tests
# ---------------------------------------------------------------------------


def test_run_loop_writes_rows_and_stops_cleanly(qmp_server: Path, tmp_path: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "query-status": {"return": {"status": "running", "running": True}},
            "query-blockstats": {"return": []},
            "query-stats": {"error": {"class": "CommandNotFound", "desc": "n/a"}},
        },
    )
    server.start()
    out_path = tmp_path / "telemetry-qmp.jsonl"
    stop = threading.Event()

    def stop_after(ms: int) -> None:
        time.sleep(ms / 1000.0)
        stop.set()

    threading.Thread(target=stop_after, args=(350,), daemon=True).start()
    rows = qmp.run_loop(
        socket_path=qmp_server,
        output_path=out_path,
        t_mono_origin_ns=time.monotonic_ns(),
        interval_ms=100,
        stop_event=stop,
    )
    server.shutdown()

    assert rows >= 2, f"expected >=2 rows, got {rows}"
    lines = [json.loads(l) for l in out_path.read_text().splitlines()]
    assert len(lines) == rows
    for r in lines:
        assert r["source"] == "host_qmp"
        assert r["vm_running"] is True


def test_savevm_and_loadvm_via_human_monitor(qmp_server: Path) -> None:
    server = FakeQMPServer(
        qmp_server,
        responses={
            "human-monitor-command": {"return": ""},
        },
    )
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        out_save = client.savevm("baseline")
        out_load = client.loadvm("baseline")
        assert out_save == ""
        assert out_load == ""
    finally:
        client.close()
        server.shutdown()
    # Both calls go out as human-monitor-command with the right cmdline.
    hmcs = [m for m in server.received if m.get("execute") == "human-monitor-command"]
    cmds = [m["arguments"]["command-line"] for m in hmcs]
    assert "savevm baseline" in cmds
    assert "loadvm baseline" in cmds


def test_loadvm_surface_error(qmp_server: Path) -> None:
    server = FakeQMPServer(qmp_server)  # no responses → error reply
    server.start()
    try:
        client = qmp.QMPClient(qmp_server)
        client.connect()
        with pytest.raises(qmp.QMPError):
            client.loadvm("does-not-exist")
    finally:
        client.close()
        server.shutdown()


def test_run_loop_returns_zero_when_socket_missing(tmp_path: Path) -> None:
    # No server bound to the socket path.
    rows = qmp.run_loop(
        socket_path=tmp_path / "nonexistent.sock",
        output_path=tmp_path / "telemetry-qmp.jsonl",
        t_mono_origin_ns=time.monotonic_ns(),
        interval_ms=100,
        stop_event=threading.Event(),
    )
    assert rows == 0