import sqlite3
import threading

import pytest
from sqlalchemy import create_engine

import sqlmem.engine as eng_mod
from sqlmem import CachingEngine, DeltaConfig
from sqlmem.cache import CacheManager
from sqlmem.stats import StatsCollector


@pytest.fixture
def source_engine(tmp_path):
    db_path = tmp_path / "source.db"
    conn = sqlite3.connect(db_path)
    conn.executescript(
        """
        CREATE TABLE products (id TEXT PRIMARY KEY, name TEXT, changed TEXT);
        INSERT INTO products VALUES ('1', 'Widget', '2026-06-01 10:00:00');
        """
    )
    conn.commit()
    conn.close()
    engine = create_engine(f"sqlite:///{db_path}")
    yield engine
    engine.dispose()


@pytest.fixture
def patched_cache(tmp_path, monkeypatch):
    monkeypatch.setattr(eng_mod, "CACHE_DB_PATH", tmp_path / "cache.db")
    monkeypatch.setattr(eng_mod, "BACKUP_INTERVAL_SECONDS", 9999)


def test_static_table_state_and_tracking(source_engine, patched_cache):
    engine = CachingEngine(source_engine)
    engine.execute("SELECT id, name FROM products")
    s = engine.stats.tables["products"]
    assert s.state == "ready"
    assert s.tracking == "static"
    assert s.rows == 1
    engine.close()


def test_delta_table_tracking(source_engine, patched_cache):
    engine = CachingEngine(
        source_engine, delta={"products": DeltaConfig("changed", ["id"])}
    )
    engine.execute("SELECT id, name FROM products")
    s = engine.stats.tables["products"]
    assert s.tracking == "delta"
    assert s.state == "ready"
    engine.close()


def test_ttl_table_reports_stale(source_engine, patched_cache):
    engine = CachingEngine(source_engine, ttl={"products": 0})
    engine.execute("SELECT id, name FROM products")
    s = engine.stats.tables["products"]
    assert s.tracking == "ttl"
    assert s.state == "stale"  # ttl=0 → already past its max age
    engine.close()


def test_counters_still_reported(source_engine, patched_cache):
    engine = CachingEngine(source_engine)
    engine.execute("SELECT id, name FROM products")
    engine.execute("SELECT id, name FROM products")
    stats = engine.stats
    assert stats.misses == 1
    assert stats.hits == 1
    engine.close()


def test_stats_exposes_table_error(source_engine, patched_cache):
    engine = CachingEngine(source_engine)
    engine.execute("SELECT id, name FROM products")
    engine._cache.record_error("products", "ValueError: boom")

    s = engine.stats
    assert s.errors == 1
    assert s.tables["products"].consecutive_failures == 1
    assert s.tables["products"].last_error == "ValueError: boom"
    assert s.tables["products"].last_error_at is not None
    engine.close()


def test_stats_no_error_by_default(source_engine, patched_cache):
    engine = CachingEngine(source_engine)
    engine.execute("SELECT id, name FROM products")
    s = engine.stats
    assert s.errors == 0
    assert s.tables["products"].consecutive_failures == 0
    assert s.tables["products"].last_error is None
    engine.close()


# --- a table being loaded for the first time shows up as "loading" ----------


def test_snapshot_surfaces_a_loading_table(tmp_path):
    cache = CacheManager(db_path=tmp_path / "cache.db", backup_interval=9999)
    snap = StatsCollector().snapshot(cache.connection, {"pending": "loading"})
    assert "pending" in snap.tables
    assert snap.tables["pending"].state == "loading"
    assert snap.tables["pending"].rows == 0
    cache.close()


def test_loading_state_visible_from_another_thread_during_load(tmp_path):
    """A first load in progress is observable as 'loading' from another thread."""
    cache = CacheManager(db_path=tmp_path / "cache.db", backup_interval=9999)
    started = threading.Event()
    release = threading.Event()

    class BlockingCursor:
        def __init__(self, rows):
            self._rows = list(rows)
            self._done = False

        def fetchmany(self, size):
            if self._done:
                return []
            started.set()
            release.wait(5)  # hold the load open until the test releases it
            self._done = True
            return self._rows

    class BlockingSource:
        def execute(self, sql):
            return BlockingCursor([("1", "alice")])

    loader = threading.Thread(
        target=cache.load_table, args=("users", ["id", "name"], BlockingSource())
    )
    loader.start()
    try:
        assert started.wait(5), "load did not start"
        # mid-load: not yet in _sqlmem_tables, but surfaced as loading
        assert cache.get_states()["users"] == "loading"
        snap = StatsCollector().snapshot(cache.connection, cache.get_states())
        assert snap.tables["users"].state == "loading"
    finally:
        release.set()
    loader.join(5)
    assert not loader.is_alive()
    assert cache.get_states()["users"] == "ready"
    cache.close()