/**
 * Native System (#249 System S2 Task 5): the concept's `renderSystem` shell (app.js 698–706) at `#/system/<section>`.
 * Under the page heading it renders the section nav (`.section-nav`, one button per section, the shown one
 * `aria-pressed`; a press navigates to its hash), then `.settings-layout` with the section's body and the Save row
 * (`span.small#settings-status` + "Save preferences"). D92: no "Sample configuration" chip, the status copy is
 * truthful and "Save preferences" is aria-disabled while nothing is unsaved. A section not delivered yet shows the
 * per-section hand-off to its legacy tool (D94), never mock placeholders. Overview (system-overview.mjs),
 * Appearance (system-appearance.mjs), Sources & scans (system-sources.mjs), Integrations (system-integrations.mjs),
 * Maintenance (system-maintenance.mjs) and Backup & export (system-backups.mjs) are native.
 *
 * Switching sections keeps the shell (and focus on the pressed button) and disposes the old section's scope, so its
 * listeners and timers never outlive it. The drafts are module-level (Q10): they live for the page session.
 */
import { createButton, createScope } from '../shared/toolkit/core.js';
import { SYSTEM_SECTIONS, navigateTo } from './state.mjs';
import { createSystemDrafts, DRAFT_DOMAINS } from './system-state.mjs';
import { sectionNav } from './system-controls.mjs';
import { mountOverview } from './system-overview.mjs';
import { mountAppearance } from './system-appearance.mjs';
import { mountSources } from './system-sources.mjs';
import { mountMaintenance } from './system-maintenance.mjs';
import { mountBackups } from './system-backups.mjs';
import { LORA_ENABLE_URL, LORA_STATUS_URL, loraValues, mountIntegrations, writeHostInParts } from './system-integrations.mjs';
import { busyToast } from './activity-scan.mjs';
import { showWorkspaceToast } from './toast.mjs';
import { displayPreferences, readPreferences, reconcilePreferences, subscribePreferences, writePreferences } from './preferences.mjs';

const SETTINGS_URL = '/prompt_manager/settings';
const ADMIN = Object.freeze({ href: '/prompt_manager/admin', label: 'Open existing administration' });
/**
 * D94: where each section's capabilities live until its PR (the plan's legacy capability coverage): the admin page's
 * dashboard, Settings, Maintenance, Backup, Restore, Scan, Logs, Diagnostics and Auto-tag tools, and the gallery's
 * settings, thumbnails, duplicates and cache tools.
 */
export const SECTION_HANDOFFS = Object.freeze({
    tagging: [ADMIN],
    diagnostics: [ADMIN],
});
export const NOT_DELIVERED = 'This setting is not available here yet.';

let drafts = null;
// The Activity store of the System page shown last: a refused host save that does not name its job reads the list.
let jobs = null;

/** The running job a 409 `busy` named, else the first running one from a fresh list read (the load never throws). */
async function runningJob(error) {
    if (error?.running) return error.running;
    await jobs.load();
    return jobs.running()[0];
}

function el(tag, text, className) {
    const node = document.createElement(tag);
    if (text !== undefined) node.textContent = text;
    if (className) node.className = className;
    return node;
}

/** A domain whose settings no delivered section edits yet: nothing can be drafted, and a write would say it failed. */
const undelivered = async () => { throw new Error(NOT_DELIVERED); };

/**
 * The page session's drafts (Q10). The browser domain is this browser's display defaults (preferences.mjs): a write
 * says whether storage kept it, so the status never claims "Saved in this browser." for a change only this tab holds.
 * The host domain reads and saves the server settings with their revision (#220).
 */
export function systemDrafts(api) {
    drafts ??= createSystemDrafts({
        readBrowser: () => readPreferences().values,
        readRuntime: () => ({}),
        writeBrowser: changes => {
            // Another page changed a drafted value since this tab read it, and no storage event told it yet: refuse,
            // so the store keeps the draft, flags it and reads the values again; the next Save is an explicit choice.
            const baseline = drafts.saved('browser');
            const { conflicts } = reconcilePreferences({ baseline, drafts: changes, next: readPreferences().values });
            if (conflicts.length) throw Object.assign(new Error('Settings changed elsewhere'), { code: 'settings-changed' });
            return { persisted: writePreferences(changes, undefined, { baseline }).persisted };
        },
        writeRuntime: undelivered,
        async readHost() {
            // S10: the LoRA state rides along; when it cannot be read its values stay missing (Integrations says so)
            // and every other host setting still loads.
            const [result, lora] = await Promise.all([api.get(SETTINGS_URL, { cache: 'no-store' }),
                api.get(LORA_STATUS_URL, { cache: 'no-store' }).catch(() => null)]);
            // The store reads a missing value as none and a missing revision as unreadable (no host save). #317: which
            // thumbnail formats the server can write rides along as a read-only value (never drafted or sent).
            return { values: { ...result.settings, thumbnail_encoders: result.thumbnail_encoders, ...(lora ? loraValues(lora) : {}) },
                revision: result.revision };
        },
        async writeHost(changes, { expected_revision }) {
            // S10: the LoRA keys save through /lora/enable, the rest through /settings, each with the current revision;
            // a save where only one part was written reports which (writeHostInParts, review I3).
            try {
                return await writeHostInParts({ changes, saved: drafts.saved('host'), expected_revision,
                    postLora: body => api.post(LORA_ENABLE_URL, body), postSettings: body => api.post(SETTINGS_URL, body) });
            } catch (error) {
                // A sources change waits for a running record-changing job (S4): name it, as a refused start does (D57).
                if (error?.code === 'busy') showWorkspaceToast(busyToast(await runningJob(error)));
                throw error;
            }
        },
    });
    return drafts;
}

/** D94: the shared hand-off panel, linking each legacy tool that still owns this section. */
function handoff(section) {
    const panel = el('section', undefined, 'surface handoff');
    panel.append(el('h2', 'Your current tools are ready'),
        el('p', 'This workspace is being introduced in stages. Continue in the existing tool with your saved data.'));
    for (const tool of SECTION_HANDOFFS[section]) {
        const link = el('a', tool.label, 'workspace-link');
        link.href = window.ApiClient.resolveUrl(tool.href);
        panel.append(link);
    }
    return [panel];
}

/** D92: highlight the controls of the settings the last save could not save. */
function markFailed(layout, store) {
    const failed = new Set(DRAFT_DOMAINS.flatMap(domain => [...store.failed(domain)]));
    for (const control of layout.querySelectorAll('[data-setting]')) {
        // A row's control names its stored key when that differs from the row id (Appearance's `data-key`).
        if (failed.has(control.dataset.key ?? control.dataset.setting)) control.setAttribute('aria-invalid', 'true');
        else control.removeAttribute('aria-invalid');
    }
}

/**
 * The sections delivered so far: Overview (S2 Task 6), Appearance (S3 Task 8), Sources & scans (S4 Task 11),
 * Integrations (S10 Task 27), Maintenance (S7 Task 19) and Backup & export (S9 Task 24).
 */
export const DELIVERED_SECTIONS = Object.freeze({
    overview: mountOverview,
    appearance: mountAppearance,
    sources: mountSources,
    integrations: mountIntegrations,
    maintenance: mountMaintenance,
    backups: mountBackups,
});

/**
 * Mount System under the heading `renderHeading` wrote in `main`. Returns `{show(section)}`, which shows another
 * section in place. `scope` is the page's view scope; `sections` maps a section id to a delivered section's mount
 * (`(container, {api, activity, scope, drafts}) => nodes`), and every other section hands off. `activity` is the page's
 * Activity store, which follows the jobs a section starts.
 *
 * The host values are read on mount (and by the store again after a conflict), so a save carries the current revision;
 * until a read returned one, a host save fails without a request (system-state.mjs). The browser values are read on
 * mount and again whenever another page changes them (a `storage` event). Either way a value another page changed
 * under one of this tab's drafts flags that draft (D92's conflict status), including a change made while System was
 * not mounted (the drafts outlive it, Q10).
 */
export function mountSystem(main, api, scope, { section, activity, sections = DELIVERED_SECTIONS, navigate = navigateTo }) {
    const store = systemDrafts(api);
    jobs = activity;
    store.reloadHost();
    // Another tab or the legacy gallery changed the display defaults: clean values follow it; a draft it overtook stays
    // and is flagged (D92's conflict status). `next` is null when the values cannot be read (no gallery-settings.js).
    const reconcile = next => {
        const baseline = store.saved('browser');
        // The first mount has read nothing yet, so nothing can have been overtaken.
        const conflicts = next && Object.keys(baseline).length
            ? reconcilePreferences({ baseline, drafts: store.changes('browser'), next }).conflicts : [];
        store.load('browser').then(() => store.conflict('browser', conflicts), () => {});
    };
    reconcile(displayPreferences());
    scope.cleanup(subscribePreferences(window, next => reconcile(next.values)));
    const nav = sectionNav({ label: 'System sections', sections: SYSTEM_SECTIONS, active: section, scope,
        onSelect: id => navigate(`#/system/${id}`) });
    const layout = el('div', undefined, 'settings-layout');
    const saveRow = el('div', undefined, 'save-row');
    const status = el('span', undefined, 'small');
    status.id = 'settings-status';
    const save = createButton('Save preferences', 'ca-primary');
    saveRow.append(status, save);
    layout.append(saveRow);
    main.append(nav, layout);

    const paintStatus = () => {
        status.textContent = store.statusText();
        if (store.dirty() && !store.saving()) save.removeAttribute('aria-disabled');
        else save.setAttribute('aria-disabled', 'true');
        markFailed(layout, store);
    };
    scope.cleanup(store.subscribe(paintStatus));
    scope.listen(save, 'click', () => {
        if (save.getAttribute('aria-disabled') === 'true') return;
        const saving = store.save();
        paintStatus();
        saving.then(() => { if (!scope.signal.aborted) paintStatus(); });
    });

    let sectionScope = null;
    scope.cleanup(() => sectionScope?.dispose());
    function show(next) {
        sectionScope?.dispose();
        sectionScope = createScope();
        for (const button of nav.children) button.setAttribute('aria-pressed', String(button.dataset.value === next));
        while (layout.firstChild !== saveRow) layout.firstChild.remove();
        const mount = sections[next];
        const nodes = mount ? mount(layout, { api, activity, scope: sectionScope, drafts: store }) : handoff(next);
        layout.prepend(...nodes);
        paintStatus();
    }
    show(section);
    return { show };
}