"""Plugin state transitions are counted, not stored.

`PluginStateManager` used to keep every transition in a per-plugin history on
the hot scheduling path (RUNNING on reserve, ENABLED on finish), but nothing
ever read the entries -- `get_state_info()` only reported how many there were.
It now keeps just that lifetime count, which `state_history_count` surfaces
through the web API.
"""

import os
import sys
import threading

import pytest

sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))

from src.plugin_system.plugin_state import (  # noqa: E402
    PluginState,
    PluginStateManager,
)


def _cycle_updates(manager, plugin_id, cycles):
    """Drive the real scheduling path: RUNNING on reserve, ENABLED on finish."""
    for _ in range(cycles):
        manager.set_state(plugin_id, PluginState.RUNNING)
        manager.set_state(plugin_id, PluginState.ENABLED)


def test_state_history_count_reports_lifetime_total():
    """`get_state_info()['state_history_count']` counts every transition."""
    manager = PluginStateManager()
    manager.set_state("clock", PluginState.ENABLED)

    cycles = 4000
    _cycle_updates(manager, "clock", cycles)

    info = manager.get_state_info("clock")
    assert info["state_history_count"] == 1 + cycles * 2


def test_error_transitions_are_counted():
    """set_state_with_error() is a transition too."""
    manager = PluginStateManager()
    manager.set_state("clock", PluginState.ENABLED)
    manager.set_state_with_error(
        "clock", PluginState.ENABLED, {"reason": "update timeout"}
    )

    info = manager.get_state_info("clock")
    assert info["state_history_count"] == 2
    assert info["error_info"] == {"reason": "update timeout"}


def test_count_is_isolated_per_plugin():
    manager = PluginStateManager()
    manager.set_state("clock", PluginState.ENABLED)
    _cycle_updates(manager, "clock", 50)
    manager.set_state("weather", PluginState.ENABLED)

    assert manager.get_state_info("clock")["state_history_count"] == 101
    assert manager.get_state_info("weather")["state_history_count"] == 1


def test_clear_state_drops_the_count():
    """Unloading a plugin still releases everything it accumulated."""
    manager = PluginStateManager()
    manager.set_state("clock", PluginState.ENABLED)
    _cycle_updates(manager, "clock", 10)

    manager.clear_state("clock")

    info = manager.get_state_info("clock")
    assert info["state"] == PluginState.UNLOADED.value
    assert info["state_history_count"] == 0


def test_get_state_info_is_a_consistent_snapshot():
    """An unload running concurrently must not be observed half-done.

    Each field used to be read under its own lock, so clear_state() could
    interleave: 'state' read before the removal, 'state_history_count' after,
    handing a caller a plugin that is ENABLED with zero transitions. The whole
    payload is now built in one critical section.
    """
    m = PluginStateManager()
    _cycle_updates(m, "clock", 50)

    inconsistent = []
    stop = threading.Event()

    def reader():
        while not stop.is_set():
            info = m.get_state_info("clock")
            # Either fully present or fully cleared -- never a live state with
            # a wiped count.
            if info["state"] != PluginState.UNLOADED.value and \
                    info["state_history_count"] == 0:
                inconsistent.append(info)
                return

    def clearer():
        for _ in range(200):
            for _ in range(20):
                m.set_state("clock", PluginState.ENABLED)
            m.clear_state("clock")

    t = threading.Thread(target=reader, daemon=True)
    t.start()
    clearer()
    stop.set()
    t.join(timeout=5)

    assert not inconsistent, f"observed a torn snapshot: {inconsistent[:1]}"


def test_state_info_reports_only_what_something_records():
    """No field that is always null.

    ``last_display`` was reported here, but nothing ever recorded a display()
    call, so it was null for every plugin. Its only reader is the web process,
    whose PluginManager never calls display(), so recording it in the display
    process could not have filled it either.
    """
    manager = PluginStateManager()
    manager.set_state("clock", PluginState.ENABLED)
    manager.record_update("clock")

    info = manager.get_state_info("clock")
    assert "last_display" not in info
    assert info["last_update"] is not None


if __name__ == "__main__":
    sys.exit(pytest.main([__file__, "-v"]))