"""AX COMPUTATION tests — DB Browser for SQLite (Qt6).

Four computation engines, all driven purely through the AX API + System Events
keystrokes, every expected value taken verbatim from what was OBSERVED on the
reference app (recon.md ## COMPUTATION):

  1. Execute SQL          type SQL -> press `Execute SQL` -> results grid + message pane
  2. DDL preview          `Edit table definition` / `Edit Index Schema` live CREATE preview
  3. Browse Data          record counter `N - M of T` + "Filter in any column"
  4. Database Structure   tree object counts `Tables (N) / Indices (N) / ...`

A fresh app has NO database open, so every engine test first opens the in-memory
database (`File > New In-Memory Database`) and dismisses the auto-opened
`Edit table definition` modal with that window's OWN scoped `Cancel`.

Deliberate omissions (recon says these reads are unreliable / non-deterministic):
  * the SQL editor's own AXValue is truncated by QScintilla -> never asserted
  * the `in Nms` / `Took 0ms` timing digits in the message pane -> never asserted
Never pressed: Write/Revert Changes, New/Open Database, any Save…, dock Close,
Delete Table…, or any native file-dialog button.
"""

import json
import os
import re
import subprocess
import time

import pytest
import rb_testgen_kit as kit

RESULTS_DIR = os.environ.get("RESULTS_DIR", os.path.dirname(os.path.abspath(__file__)))
COUNTER_RE = re.compile(r"^\s*\d+\s*-\s*\d+\s+of\s+\d+\s*$")


def screenshot_assert(test_name, description, results_dir):
    ss_dir = os.path.join(results_dir, "screenshots")
    os.makedirs(ss_dir, exist_ok=True)
    ss_path = os.path.join(ss_dir, f"{test_name}.png")
    try:
        subprocess.run(["screencapture", "-x", ss_path], timeout=5)
    except Exception:
        pass
    assertions_file = os.path.join(ss_dir, "assertions.json")
    assertions = {}
    if os.path.exists(assertions_file):
        try:
            with open(assertions_file) as f:
                assertions = json.load(f)
        except Exception:
            assertions = {}
    assertions[f"{test_name}.png"] = description
    with open(assertions_file, "w") as f:
        json.dump(assertions, f, indent=2)


def _esc(times=1):
    for _ in range(times):
        subprocess.run(["osascript", "-e",
                        'tell application "System Events" to key code 53'],
                       capture_output=True)
        time.sleep(0.3)


def _keystroke(text):
    subprocess.run(["osascript", "-e",
                    'tell application "System Events" to keystroke ' + json.dumps(text)],
                   capture_output=True)


def open_menu(ax, top):
    mb = ax.find(role="menu_bar_item", name=top, max_results=1)
    if not mb:
        return None
    ax.action(mb[0].id, "AXPress")
    time.sleep(0.6)
    m = ax.find(role="menu", root_id=mb[0].id, max_results=1, max_depth=1)
    return m[0] if m else None


def rb_reach_menu_item(ax, top, item_name):
    m = open_menu(ax, top)
    if m is None:
        return False
    for it in ax.find(role="menu_item", root_id=m.id, max_results=80, max_depth=1):
        if (it.name or "") == item_name:
            ok = ax.action(it.id, "AXPress")
            time.sleep(1.4)
            return bool(ok)
    _esc(2)
    return False


def find_window(ax, title_substr):
    for w in ax.find(role="window", max_results=10, max_depth=1):
        if title_substr.lower() in (w.name or "").lower():
            return w
    return None


def rb_enter_inmemory_db(ax):
    """File > New In-Memory Database, then dismiss the auto-opened table dialog."""
    rb_reach_menu_item(ax, "File", "New In-Memory Database")
    w = find_window(ax, "Edit table definition")
    if w is not None:
        c = ax.find(role="button", name="Cancel", root_id=w.id, max_results=2)
        if c:
            ax.action(c[0].id, "AXPress")
            time.sleep(1.0)
    return find_window(ax, "Edit table definition") is None


def switch_tab(ax, name):
    r = ax.find(role="radio", name=name, max_results=1)
    if not r:
        return False
    ok = ax.action(r[0].id, "AXPress")
    time.sleep(1.0)
    return bool(ok)


def find_button(ax, name, root_id=None):
    for b in ax.find(role="button", max_results=90, root_id=root_id):
        if (b.name or "") == name:
            return b
    return None


def enabled(ax, el):
    return bool(ax.get(el.id, ["AXEnabled"]).get("AXEnabled"))


def sql_editor(ax):
    """The QScintilla SQL editor: the only settable text_area that is not the SQL log."""
    for t in ax.find(role="text_area", max_results=15):
        if not ax.is_attribute_settable(t.id, "AXValue"):
            continue
        v = str(ax.get(t.id, ["AXValue"]).get("AXValue") or "")
        if "PRAGMA" in v or "EXECUTING" in v:
            continue
        return t
    return None


def run_sql(ax, sql):
    """Type + execute SQL. set_value is IGNORED by QScintilla -> click + keystroke."""
    switch_tab(ax, "Execute SQL")
    e = sql_editor(ax)
    assert e is not None, "SQL editor not found"
    ax.click_element_cg(e.id)
    time.sleep(0.35)
    subprocess.run(["osascript", "-e",
                    'tell application "System Events" to keystroke "a" using command down'],
                   capture_output=True)
    time.sleep(0.25)
    _keystroke(sql)
    time.sleep(0.5)
    b = find_button(ax, "Execute SQL")
    assert b is not None and enabled(ax, b), "Execute SQL button not enabled"
    ax.action(b.id, "AXPress")
    time.sleep(1.9)


def result_cells(ax):
    """(column headers, cell values) of the SQL results grid. Skips the 'search result' decoy."""
    cols, cells = [], []
    for t in ax.find(role="table", max_results=10):
        if (t.name or "") == "search result":
            continue
        ch = (ax.tree(max_depth=3, root_id=t.id).get("children") or [])
        c = [x.get("name") for x in ch if x.get("role") == "column"]
        v = [x.get("name") for x in ch if x.get("role") == "label"]
        if c or v:
            cols, cells = c, v
    return cols, cells


def exec_msg(ax):
    for t in ax.find(role="text_area", max_results=15):
        v = str(ax.get(t.id, ["AXValue"]).get("AXValue") or "")
        if v.startswith("Execution finished"):
            return v
    return ""


def record_counter(ax):
    """Browse Data counter, e.g. '1 - 3 of 3'. MUST use the regex — a plain ' of ' test
    also matches 'Identification of the cell currently in the editor'."""
    for l in ax.find(role="label", max_results=350):
        v = str(ax.get(l.id, ["AXValue"]).get("AXValue") or "")
        if COUNTER_RE.match(v):
            return v.strip()
    return None


def dialog_preview(ax, window):
    """The read-only DDL preview text_area inside a dialog (its AXValue contains CREATE)."""
    for t in ax.find(role="text_area", root_id=window.id, max_results=8):
        v = str(ax.get(t.id, ["AXValue"]).get("AXValue") or "")
        if "CREATE" in v:
            return v
    return None


def structure_group_names(ax):
    out = []
    for g in ax.find(role="group", max_results=250):
        n = g.name or ""
        if n.startswith(("Tables (", "Indices (", "Views (", "Triggers (")):
            out.append(n)
    return sorted(set(out))


# ── extra locators / navigation (semantic: role + visible AXTitle only) ─────────

def wait_ready(ax, timeout=6.0):
    """Settle after the per-test relaunch: wait until the app exposes a window."""
    deadline = time.time() + timeout
    while time.time() < deadline:
        if ax.find(role="window", max_results=1, max_depth=1):
            return True
        time.sleep(0.4)
    return False


def dialog_button(ax, window, name):
    """A button scoped INSIDE a dialog window (never a global 'Cancel'/'Add' match)."""
    if window is None:
        return None
    for b in ax.find(role="button", root_id=window.id, max_results=40):
        if (b.name or "") == name:
            return b
    return None


def dialog_field(ax, window, name):
    if window is None:
        return None
    for t in ax.find(role="text_field", root_id=window.id, max_results=25):
        if (t.name or "") == name:
            return t
    return None


def dialog_checkbox(ax, window, name):
    if window is None:
        return None
    for c in ax.find(role="checkbox", root_id=window.id, max_results=25):
        n = c.name or ""
        if n == name or name in n:
            return c
    return None


def rb_enter_create_table_dialog(ax):
    """SURFACE: Database Structure tab -> AXPress `Create Table` -> window
    'Edit table definition' (the second time this modal is crossed in a test)."""
    switch_tab(ax, "Database Structure")
    b = find_button(ax, "Create Table")
    assert b is not None, "toolbar button 'Create Table' not found"
    assert enabled(ax, b), "'Create Table' is disabled — no database open"
    ax.action(b.id, "AXPress")
    time.sleep(1.3)
    return find_window(ax, "Edit table definition")


def rb_enter_create_index_dialog(ax):
    """SURFACE: Database Structure tab -> AXPress `Create Index` -> window
    'Edit Index Schema' (needs a database AND at least one table)."""
    switch_tab(ax, "Database Structure")
    b = find_button(ax, "Create Index")
    assert b is not None, "toolbar button 'Create Index' not found"
    assert enabled(ax, b), "'Create Index' is disabled — no database open"
    ax.action(b.id, "AXPress")
    time.sleep(1.3)
    return find_window(ax, "Edit Index Schema")


def rb_back_cancel(ax, window):
    """Close a dialog with its OWN scoped Cancel button."""
    b = dialog_button(ax, window, "Cancel")
    if b is None:
        return False
    ok = ax.action(b.id, "AXPress")
    time.sleep(0.8)
    return bool(ok)


def group_named(ax, name):
    for g in ax.find(role="group", max_results=250):
        if (g.name or "") == name:
            return g
    return None


# ── Engine 1 — Execute SQL ─────────────────────────────────────────────────────

class TestExecuteSQLComputation:
    """SQL evaluated by the app: results grid columns/cells + message pane."""

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="results column 'answer' with cell '42' for SELECT 7*6")
    def test_sql_multiplication(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT 7*6 AS answer;")
        cols, cells = result_cells(ax)
        screenshot_assert(
            "computation_test_sql_multiplication",
            "DB Browser for SQLite with the Execute SQL tab active. The SQL editor holds "
            "'SELECT 7*6 AS answer;' and the results grid below it shows one column headed "
            "'answer' containing the value 42 (7*6). The message pane under the grid reads "
            "'Execution finished without errors. Result: 1 rows returned ...'.",
            RESULTS_DIR)
        assert cols == ["answer"], f"columns={cols!r} cells={cells!r}"
        assert kit.rb_value(cells, "42"), f"expected cell '42', got cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="results column 'total' with cell '5' for SELECT 2+3")
    def test_sql_addition(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT 2+3 AS total;")
        cols, cells = result_cells(ax)
        assert cols == ["total"], f"columns={cols!r} cells={cells!r}"
        assert kit.rb_value(cells, "5"), f"expected cell '5', got cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="columns ['d','m'] and cells ['2','2'] for 10/4 and 10%4")
    def test_sql_integer_division_and_modulo(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT 10/4 AS d, 10%4 AS m;")
        cols, cells = result_cells(ax)
        assert cols == ["d", "m"], f"columns={cols!r} cells={cells!r}"
        assert cells == ["2", "2"], f"cells={cells!r}"
        assert kit.rb_value(cells, ["2", "2"]), f"cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="results column 'u' with cell 'DB4S' for upper('db4s')")
    def test_sql_string_upper(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT upper('db4s') AS u;")
        cols, cells = result_cells(ax)
        assert cols == ["u"], f"columns={cols!r} cells={cells!r}"
        assert kit.rb_value(cells, "DB4S"), f"expected cell 'DB4S', got cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="results column 'n' with cell '5' for length('hello')")
    def test_sql_string_length(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT length('hello') AS n;")
        cols, cells = result_cells(ax)
        assert cols == ["n"], f"columns={cols!r} cells={cells!r}"
        assert kit.rb_value(cells, "5"), f"expected cell '5', got cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="count(*)=3 and sum(a)=6 over 3 inserted rows -> cells ['3','6']")
    def test_sql_aggregate_count_and_sum(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "CREATE TABLE t1(a INTEGER, b TEXT); "
                    "INSERT INTO t1 VALUES(1,'x'),(2,'y'),(3,'z'); "
                    "SELECT count(*) AS c, sum(a) AS s FROM t1;")
        cols, cells = result_cells(ax)
        assert cols == ["c", "s"], f"columns={cols!r} cells={cells!r}"
        assert cells == ["3", "6"], f"cells={cells!r}"
        assert kit.rb_value(cells, ["3", "6"]), f"cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="message pane: 'Execution finished without errors.' and "
                           "'query executed successfully' with '3 rows affected'")
    def test_sql_dml_reports_rows_affected(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "CREATE TABLE nums(n INTEGER, label TEXT); "
                    "INSERT INTO nums VALUES(10,'ten'),(20,'twenty'),(30,'thirty');")
        msg = exec_msg(ax)
        assert msg.startswith("Execution finished without errors."), f"message={msg!r}"
        assert kit.rb_value(msg, "query executed successfully"), f"message={msg!r}"
        assert kit.rb_value(msg, "3 rows affected"), f"message={msg!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="message pane 'Execution finished with errors.' + "
                           "'no such table: no_such_table_xyz' and an EMPTY results grid")
    def test_sql_error_reports_no_such_table(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "SELECT * FROM no_such_table_xyz;")
        msg = exec_msg(ax)
        cols, cells = result_cells(ax)
        screenshot_assert(
            "computation_test_sql_error_no_such_table",
            "DB Browser for SQLite, Execute SQL tab active. The editor holds "
            "'SELECT * FROM no_such_table_xyz;'. The results grid is EMPTY (no columns, no "
            "rows) and the message pane reports the SQLite error: 'Execution finished with "
            "errors. Result: no such table: no_such_table_xyz'.",
            RESULTS_DIR)
        assert msg.startswith("Execution finished with errors."), f"message={msg!r}"
        assert kit.rb_value(msg, "no such table: no_such_table_xyz"), f"message={msg!r}"
        assert cols == [], f"results grid should be empty, got columns={cols!r} cells={cells!r}"

    @pytest.mark.rb(depth=1, jump_kind="transition",
                    expect="button 'Execute SQL' AXEnabled False->True once the in-memory "
                           "database exists")
    def test_sql_execute_button_disabled_until_database_open(self, ax):
        wait_ready(ax)
        assert switch_tab(ax, "Execute SQL"), "could not activate the Execute SQL tab"
        b = find_button(ax, "Execute SQL")
        assert b is not None, "button 'Execute SQL' not found on the Execute SQL tab"
        before = enabled(ax, b)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        b2 = find_button(ax, "Execute SQL")
        assert b2 is not None, "button 'Execute SQL' vanished after opening the database"
        after = enabled(ax, b2)
        assert before is False, f"with no database open the button should be disabled, got {before!r}"
        assert after is True, f"with the in-memory database open it should be enabled, got {after!r}"
        assert kit.rb_flip(before, after), f"no enabled flip: {before!r} -> {after!r}"


# ── Engine 2 — DDL preview generators (dialog surfaces) ───────────────────────

class TestDDLPreviewComputation:
    """The dialogs generate a live CREATE statement from the form contents."""

    @pytest.mark.rb(depth=2, jump_kind="value",
                    expect='preview CREATE TABLE "" ( ); -> CREATE TABLE "people" ( );')
    def test_create_table_preview_reflects_table_name(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        w = rb_enter_create_table_dialog(ax)
        assert w is not None, "window 'Edit table definition' did not open"
        before = dialog_preview(ax, w)
        assert before == 'CREATE TABLE "" (\n\n);', f"initial preview={before!r}"
        field = dialog_field(ax, w, "Table")
        assert field is not None, "text_field 'Table' not found in the dialog"
        ax.set_value(field.id, "people")
        time.sleep(0.7)
        after = dialog_preview(ax, w)
        screenshot_assert(
            "computation_test_create_table_preview",
            "The modal window 'Edit table definition' is open in front of the DB Browser for "
            "SQLite main window. Its 'Table' name box contains 'people', the field grid "
            "(headers Name, Type, NN, PK, AI, U, Default, Check, Collation, Foreign Key) is "
            "still empty, and the read-only SQL preview box below shows "
            'CREATE TABLE "people" ( );  Fields / Index Constraints / Foreign Keys / Check '
            "Constraints tabs and OK / Cancel buttons are visible.",
            RESULTS_DIR)
        rb_back_cancel(ax, w)
        assert after == 'CREATE TABLE "people" (\n\n);', f"preview after naming={after!r}"
        assert kit.rb_value(after, 'CREATE TABLE "people" (\n\n);'), f"preview={after!r}"

    @pytest.mark.rb(depth=2, jump_kind="value",
                    expect='two Add presses give CREATE TABLE "people" ( "Field1" INTEGER, '
                           '"Field2" INTEGER );')
    def test_create_table_preview_grows_with_add_field(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        w = rb_enter_create_table_dialog(ax)
        assert w is not None, "window 'Edit table definition' did not open"
        field = dialog_field(ax, w, "Table")
        assert field is not None, "text_field 'Table' not found in the dialog"
        ax.set_value(field.id, "people")
        time.sleep(0.7)
        add = dialog_button(ax, w, "Add")
        assert add is not None, "button 'Add' not found in the dialog"
        ax.action(add.id, "AXPress")
        time.sleep(0.8)
        one = dialog_preview(ax, w)
        ax.action(add.id, "AXPress")
        time.sleep(0.8)
        two = dialog_preview(ax, w)
        rb_back_cancel(ax, w)
        assert one == 'CREATE TABLE "people" (\n\t"Field1"\tINTEGER\n);', \
            f"preview after 1 Add={one!r}"
        assert two == 'CREATE TABLE "people" (\n\t"Field1"\tINTEGER,\n\t"Field2"\tINTEGER\n);', \
            f"preview after 2 Adds={two!r}"
        assert kit.rb_value(two, '"Field2"\tINTEGER'), f"preview={two!r}"

    @pytest.mark.rb(depth=2, jump_kind="value",
                    expect='CREATE INDEX "" ON "t1" ( ); -> named idx_a -> '
                           'CREATE UNIQUE INDEX "idx_a" ON "t1" ( );')
    def test_create_index_preview_name_and_unique(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "CREATE TABLE t1(a INTEGER, b TEXT);")
        w = rb_enter_create_index_dialog(ax)
        assert w is not None, "window 'Edit Index Schema' did not open"
        opened = dialog_preview(ax, w)
        assert opened is not None, "no CREATE preview text_area in 'Edit Index Schema'"
        assert 'ON "t1"' in opened, f"initial index preview={opened!r}"
        name = dialog_field(ax, w, "Name")
        assert name is not None, "text_field 'Name' not found in 'Edit Index Schema'"
        ax.set_value(name.id, "idx_a")
        time.sleep(0.7)
        named = dialog_preview(ax, w)
        uniq = dialog_checkbox(ax, w, "Unique")
        assert uniq is not None, "checkbox 'Unique' not found in 'Edit Index Schema'"
        ax.action(uniq.id, "AXPress")
        time.sleep(0.7)
        unique = dialog_preview(ax, w)
        rb_back_cancel(ax, w)
        assert named == 'CREATE INDEX "idx_a" ON "t1" (\n\n);', f"preview after naming={named!r}"
        assert unique == 'CREATE UNIQUE INDEX "idx_a" ON "t1" (\n\n);', \
            f"preview after Unique={unique!r}"
        assert kit.rb_value(unique, 'CREATE UNIQUE INDEX "idx_a" ON "t1" (\n\n);'), \
            f"preview={unique!r}"


# ── Engine 3 — Browse Data record counter + filter ────────────────────────────

class TestBrowseDataCounterComputation:
    """The Browse Data tab computes 'first - last of total' and re-computes it
    from the filter expression."""

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="Browse Data record counter reads '0 - 0 of 0' with no database open")
    def test_record_counter_zero_without_database(self, ax):
        wait_ready(ax)
        assert switch_tab(ax, "Browse Data"), "could not activate the Browse Data tab"
        counter = record_counter(ax)
        assert counter is not None, "no 'N - M of T' record counter label on the Browse Data tab"
        assert kit.rb_value(counter, "0 - 0 of 0"), f"counter={counter!r}"
        assert counter == "0 - 0 of 0", f"counter={counter!r}"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="counter '1 - 3 of 3' and Table: combobox 'nums' after inserting 3 rows")
    def test_record_counter_matches_inserted_rows(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "CREATE TABLE nums(n INTEGER, label TEXT); "
                    "INSERT INTO nums VALUES(10,'ten'),(20,'twenty'),(30,'thirty');")
        assert switch_tab(ax, "Browse Data"), "could not activate the Browse Data tab"
        counter = record_counter(ax)
        combo = ax.find(role="combobox", name="nums", max_results=1)
        screenshot_assert(
            "computation_test_record_counter_three_rows",
            "DB Browser for SQLite with the Browse Data tab active. The 'Table:' dropdown "
            "shows 'nums', the data grid has the columns _rowid_, n, label with the three "
            "rows 10/ten, 20/twenty, 30/thirty, a 'Filter in any column' box sits under the "
            "headers, and the record counter reads '1 - 3 of 3'.",
            RESULTS_DIR)
        assert counter is not None, "no 'N - M of T' record counter label found"
        assert kit.rb_value(counter, "1 - 3 of 3"), f"counter={counter!r}"
        assert counter == "1 - 3 of 3", f"counter={counter!r}"
        assert combo, "no combobox titled 'nums' (the browsed table) found"

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="filter 'twenty' -> counter '1 - 1 of 1' and grid cells "
                           "['20','twenty'] with columns ['_rowid_','n','label']")
    def test_filter_narrows_grid_and_counter(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        run_sql(ax, "CREATE TABLE nums(n INTEGER, label TEXT); "
                    "INSERT INTO nums VALUES(10,'ten'),(20,'twenty'),(30,'thirty');")
        assert switch_tab(ax, "Browse Data"), "could not activate the Browse Data tab"
        flt = ax.find(role="text_field", name="Filter in any column", max_results=1)
        assert flt, "text_field 'Filter in any column' not found on the Browse Data tab"
        ax.set_value(flt[0].id, "twenty")
        time.sleep(1.7)
        counter = record_counter(ax)
        cols, cells = result_cells(ax)
        screenshot_assert(
            "computation_test_filter_narrows_grid",
            "DB Browser for SQLite, Browse Data tab active on table 'nums'. The filter box "
            "under the column headers contains 'twenty', so the grid shows only ONE row "
            "(20 / twenty) out of three, the record counter reads '1 - 1 of 1', and the "
            "'Clear Filters' toolbar button is now enabled.",
            RESULTS_DIR)
        assert counter == "1 - 1 of 1", f"counter={counter!r}"
        assert cols == ["_rowid_", "n", "label"], f"columns={cols!r}"
        assert cells == ["20", "twenty"], f"cells={cells!r}"
        assert kit.rb_value(cells, ["20", "twenty"]), f"cells={cells!r}"


# ── Engine 4 — Database Structure object counts ───────────────────────────────

class TestStructureCountComputation:
    """The structure tree counts schema objects: Tables (N) / Indices (N) / ..."""

    @pytest.mark.rb(depth=1, jump_kind="value",
                    expect="Tables (0)->Tables (1) with a tree node named 'nums' after "
                           "CREATE TABLE")
    def test_structure_tree_object_counts_reflect_created_table(self, ax):
        wait_ready(ax)
        assert rb_enter_inmemory_db(ax), "in-memory database did not open"
        assert switch_tab(ax, "Database Structure"), "could not activate Database Structure"
        before_names = structure_group_names(ax)
        assert "Tables (0)" in before_names, f"before={before_names!r}"
        assert "Indices (0)" in before_names, f"before={before_names!r}"
        assert "Views (0)" in before_names, f"before={before_names!r}"
        assert "Triggers (0)" in before_names, f"before={before_names!r}"
        run_sql(ax, "CREATE TABLE nums(n INTEGER, label TEXT);")
        # re-activating the tab is what refreshes the structure tree
        assert switch_tab(ax, "Database Structure"), "could not re-activate Database Structure"
        after_names = structure_group_names(ax)
        nums_node = group_named(ax, "nums")
        screenshot_assert(
            "computation_test_structure_counts",
            "DB Browser for SQLite with the Database Structure tab active. The schema tree "
            "now lists 'Tables (1)' expanded/containing an entry named 'nums', alongside "
            "'Indices (0)', 'Views (0)' and 'Triggers (0)'; the Create Table / Create Index / "
            "Modify Table buttons sit above the tree.",
            RESULTS_DIR)
        assert kit.rb_value(after_names, "Tables (1)"), f"after={after_names!r}"
        assert "Tables (1)" in after_names, f"after={after_names!r}"
        assert "Tables (0)" not in after_names, f"after={after_names!r}"
        assert nums_node is not None, "no tree node named 'nums' after CREATE TABLE nums"
        assert kit.rb_flip(before_names, after_names), \
            f"object counts did not change: {before_names!r} -> {after_names!r}"