"""Regression coverage for transcript virtualization preference (#4325 + #4343).

The stream-end freeze/jump fix (#4328, semantic viewport anchoring) is covered by
test_issue500_message_list_virtualization.py. This file covers the Preferences
toggle and its #4343 contract change:

- #4325 added an opt-OUT toggle (default ON).
- #4343 flipped it to EXPERIMENTAL / opt-IN (default OFF) because virtualization
  caused a scroll-up flicker on long sessions, with a force-off-for-everyone
  migration: a stored virtualize_transcript=True from the #4325 window is reset
  to off unless an explicit post-flip opt-in marker (virtualize_transcript_optin)
  is present.
"""
import json
from pathlib import Path

import pytest

REPO_ROOT = Path(__file__).resolve().parent.parent
INDEX = REPO_ROOT / "static" / "index.html"
PANELS = REPO_ROOT / "static" / "panels.js"
BOOT = REPO_ROOT / "static" / "boot.js"
UI = REPO_ROOT / "static" / "ui.js"
I18N = REPO_ROOT / "static" / "i18n.js"
CONFIG = REPO_ROOT / "api" / "config.py"


def test_virtualize_transcript_setting_is_default_off_and_allowed():
    """#4343 opt-IN model: default False (virtualization off), bool-allowlisted,
    plus the opt-in migration marker."""
    src = CONFIG.read_text(encoding="utf-8")
    assert '"virtualize_transcript": False' in src, "must default OFF (experimental/opt-in)"
    assert '"virtualize_transcript",' in src, "must be in _SETTINGS_BOOL_KEYS"
    assert '"virtualize_transcript_optin": False' in src, "opt-in migration marker must exist + default False"
    assert '"virtualize_transcript_optin",' in src, "opt-in marker must be in _SETTINGS_BOOL_KEYS"


def test_settings_preferences_expose_virtualize_toggle_experimental():
    html = INDEX.read_text(encoding="utf-8")
    assert 'id="settingsVirtualizeTranscript"' in html
    assert 'data-i18n="settings_label_virtualize_transcript"' in html
    assert 'data-i18n="settings_desc_virtualize_transcript"' in html
    # #4343: checkbox must NOT render checked by default (opt-in, default off).
    cb_line = next(l for l in html.splitlines() if 'id="settingsVirtualizeTranscript"' in l)
    assert "checked" not in cb_line, "opt-in toggle must not be pre-checked"


def test_boot_applies_saved_virtualize_preference_default_off():
    js = BOOT.read_text(encoding="utf-8")
    # #4343 default-off semantics: ===true (only an explicit true enables it).
    assert "window._virtualizeTranscript=s.virtualize_transcript===true" in js
    # Settings-load-failed fallback also defaults OFF.
    assert "window._virtualizeTranscript=false" in js


def test_ui_gate_forces_full_render_when_disabled():
    js = UI.read_text(encoding="utf-8")
    start = js.index("function _currentMessageVirtualWindow(")
    body = js[start:start + 900]
    assert "_virtualizeTranscript===false" in body
    assert "virtualized:false" in body


def test_panels_round_trip_and_hot_apply_virtualize_toggle():
    js = PANELS.read_text(encoding="utf-8")
    assert "const virtualizeTranscriptCb=$('settingsVirtualizeTranscript');" in js
    assert "payload.virtualize_transcript=virtualizeTranscriptCb.checked;" in js
    # #4343: enabling records the explicit post-flip opt-in marker.
    assert "payload.virtualize_transcript_optin=virtualizeTranscriptCb.checked;" in js
    # #4343: checkbox load honors only an explicit opt-in (===true), not !==false.
    assert "virtualizeTranscriptCb.checked=settings.virtualize_transcript===true;" in js
    assert "window._virtualizeTranscript=virtualizeTranscriptCb.checked;" in js
    # Hot-apply: toggling re-renders the open transcript immediately.
    assert "renderMessages({preserveScroll:true})" in js


def test_virtualize_toggle_i18n_all_locales():
    js = I18N.read_text(encoding="utf-8")
    assert js.count("settings_label_virtualize_transcript:") == 15
    assert js.count("settings_desc_virtualize_transcript:") == 15


# ── #4343 force-off-for-everyone migration (load_settings behavior) ──────────


@pytest.fixture
def _settings_env(tmp_path, monkeypatch):
    """Point load_settings at an isolated settings.json under tmp."""
    import api.config as config

    sf = tmp_path / "settings.json"
    monkeypatch.setattr(config, "SETTINGS_FILE", sf)
    return config, sf


def _write(sf, payload):
    sf.write_text(json.dumps(payload), encoding="utf-8")


def test_migration_unset_defaults_off(_settings_env):
    """No stored value (fresh / pre-#4325 install) → off."""
    config, sf = _settings_env
    _write(sf, {"onboarding_completed": True})
    assert config.load_settings()["virtualize_transcript"] is False


def test_migration_stale_pre_flip_true_is_reset_off(_settings_env):
    """A stored virtualize_transcript=True from the #4325 window WITHOUT the
    opt-in marker is stale → force-reset to off for everyone."""
    config, sf = _settings_env
    _write(sf, {"onboarding_completed": True, "virtualize_transcript": True})
    assert config.load_settings()["virtualize_transcript"] is False


def test_migration_explicit_post_flip_optin_is_honored(_settings_env):
    """An explicit post-flip opt-in (marker present) keeps virtualization on."""
    config, sf = _settings_env
    _write(sf, {
        "onboarding_completed": True,
        "virtualize_transcript": True,
        "virtualize_transcript_optin": True,
    })
    assert config.load_settings()["virtualize_transcript"] is True


def test_migration_optin_marker_without_true_stays_off(_settings_env):
    """Marker present but value false (user opted in then back out) → off."""
    config, sf = _settings_env
    _write(sf, {
        "onboarding_completed": True,
        "virtualize_transcript": False,
        "virtualize_transcript_optin": True,
    })
    assert config.load_settings()["virtualize_transcript"] is False