// Sessions panel: server state (via `devdesk attach --list`), recently used
// sessions remembered in this browser, and session actions (new/rename/end).

import { fetchSessionList, sessionAction } from './connection.js';
import { slugify } from './protocol.js';

const RECENTS_KEY = 'devdesk.recents';
const MAX_RECENTS = 12;

function readRecents() {
  try {
    const value = JSON.parse(localStorage.getItem(RECENTS_KEY) || '[]');
    return Array.isArray(value) ? value : [];
  } catch {
    return [];
  }
}

function writeRecents(recents) {
  try {
    localStorage.setItem(RECENTS_KEY, JSON.stringify(recents.slice(0, MAX_RECENTS)));
  } catch {
    // Storage unavailable (private mode): recents are a convenience only.
  }
}

export function rememberSession(name) {
  if (name) writeRecents([{ name, at: Date.now() }, ...readRecents().filter((r) => r.name !== name)]);
}

function forgetRecent(name) {
  writeRecents(readRecents().filter((r) => r.name !== name));
}

function renameRecent(from, to) {
  writeRecents(readRecents().map((r) => (r.name === from ? { ...r, name: to } : r)));
}

export function ago(epochSeconds) {
  if (!epochSeconds) return '';
  const s = Math.max(0, Date.now() / 1000 - epochSeconds);
  if (s < 90) return 'now';
  if (s < 3600) return `${Math.floor(s / 60)}m`;
  if (s < 86400) return `${Math.floor(s / 3600)}h`;
  return `${Math.floor(s / 86400)}d`;
}

export function el(tag, attrs = {}, ...children) {
  const node = document.createElement(tag);
  for (const [key, value] of Object.entries(attrs)) {
    if (value === undefined || value === null || value === false) continue;
    if (key === 'class') node.className = value;
    else if (key.startsWith('on')) node.addEventListener(key.slice(2), value);
    else node.setAttribute(key, value === true ? '' : value);
  }
  node.append(...children.filter((c) => c !== null && c !== undefined));
  return node;
}

export class SessionsPanel {
  // hooks: onOpen(name), onPicker(), onEnded(name), onRenamed(from, to), onData(data)
  constructor({ list, form, nameInput, select, refreshButton, pickerButton, status, hooks }) {
    Object.assign(this, { list, nameInput, select, status, hooks });
    this.current = null;
    this.data = null;
    this.busy = false;
    refreshButton.addEventListener('click', () => this.refresh());
    pickerButton.addEventListener('click', () => hooks.onPicker());
    form.addEventListener('submit', (event) => {
      event.preventDefault();
      this.createFromForm();
    });
  }

  setCurrent(name) {
    this.current = name;
    if (this.data) this.render();
  }

  setStatus(text, isError = false) {
    this.status.textContent = text;
    this.status.classList.toggle('is-error', isError);
  }

  async refresh() {
    if (this.busy) return;
    this.busy = true;
    try {
      this.data = await fetchSessionList();
      if (!this.status.classList.contains('is-error')) this.setStatus('');
    } catch (err) {
      this.setStatus(`list unavailable: ${err.message}`, true);
    } finally {
      this.busy = false;
    }
    this.render();
    this.hooks.onData?.(this.data);
  }

  async act(label, action, ...args) {
    this.setStatus(`${label}…`);
    try {
      await sessionAction(action, ...args);
      this.setStatus('');
      return true;
    } catch (err) {
      this.setStatus(err.message, true);
      return false;
    }
  }

  async createFromForm() {
    const project = this.select.value;
    const name = slugify(this.nameInput.value) || project;
    if (!name) {
      this.setStatus('Type a session name or pick a project.', true);
      this.nameInput.focus();
      return;
    }
    // With a project the session starts in that folder; without one, in the default folder.
    if (project && !(await this.act('creating', 'new', name, project))) return;
    this.nameInput.value = '';
    this.select.value = '';
    this.hooks.onOpen(name);
  }

  async rename(name) {
    const answer = window.prompt(`Rename session "${name}" to:`, name);
    if (answer === null) return;
    const next = slugify(answer);
    if (!next || next === name) {
      if (!next) this.setStatus('Names use letters, numbers, - and _.', true);
      return;
    }
    if (await this.act('renaming', 'rename', name, next)) {
      renameRecent(name, next);
      this.hooks.onRenamed(name, next);
      await this.refresh();
    }
  }

  async end(session) {
    const question = session.running
      ? `End session "${session.name}"?\n\nClaude in this session stops. The conversation stays in Claude's history (claude --resume).`
      : `Forget dormant session "${session.name}"?`;
    if (!window.confirm(question)) return;
    if (session.name === this.current) this.hooks.onEnding?.(session.name);
    if (await this.act(session.running ? 'ending' : 'forgetting', 'end', session.name)) {
      forgetRecent(session.name);
      this.hooks.onEnded(session.name);
      await this.refresh();
    } else if (session.name === this.current) {
      this.hooks.onEndAborted?.();
    }
  }

  renderSession(s) {
    const isCurrent = s.name === this.current;
    const ctx = s.context?.used_pct != null ? ` · ctx ${Math.floor(s.context.used_pct)}%` : '';
    const meta = s.running
      ? `${s.attached} attached · ${ago(s.activity)}${ctx}`
      : 'dormant · resumes Claude';
    const iconButton = (label, glyph, onclick, extra = '') =>
      el('button', { class: `dd-icon-btn ${extra}`, type: 'button', title: label, 'aria-label': `${label} ${s.name}`, onclick }, glyph);
    return el('li', { class: `dd-session-item${isCurrent ? ' is-current' : ''}${s.running ? '' : ' is-dormant'}` },
      el('button', { class: 'dd-session-open', type: 'button', title: s.dir || '', onclick: () => this.hooks.onOpen(s.name) },
        el('span', { class: `lt-dot ${s.running ? 'lt-dot-up' : 'lt-dot-idle'}` }),
        el('span', { class: 'dd-session-name' }, s.name),
        el('span', { class: 'dd-session-meta' }, meta)),
      el('span', { class: 'dd-session-actions' },
        iconButton('Rename', '✎', () => this.rename(s.name)),
        el('a', {
          class: 'dd-icon-btn', href: `?arg=${encodeURIComponent(s.name)}`, target: '_blank', rel: 'noopener',
          title: 'Open in a new tab', 'aria-label': `Open ${s.name} in a new tab`,
        }, '↗'),
        iconButton(s.running ? 'End session' : 'Forget', '×', () => this.end(s), 'dd-danger')));
  }

  render() {
    const sessions = this.data?.sessions ?? [];
    const known = new Set(sessions.map((s) => s.name));
    const recentsOnly = readRecents().filter((r) => !known.has(r.name)).slice(0, 5);

    const ordered = [...sessions].sort((a, b) =>
      (b.running - a.running) || ((b.activity || 0) - (a.activity || 0)) || a.name.localeCompare(b.name));
    const items = ordered.map((s) => this.renderSession(s));
    for (const r of recentsOnly) {
      items.push(el('li', { class: 'dd-session-item is-recent' },
        el('button', { class: 'dd-session-open', type: 'button', onclick: () => this.hooks.onOpen(r.name) },
          el('span', { class: 'lt-dot lt-dot-idle' }),
          el('span', { class: 'dd-session-name' }, r.name),
          el('span', { class: 'dd-session-meta' }, 'recent in this browser')),
        el('span', { class: 'dd-session-actions' },
          el('button', {
            class: 'dd-icon-btn dd-danger', type: 'button', title: 'Remove from recents',
            onclick: () => { forgetRecent(r.name); this.render(); },
          }, '×'))));
    }
    if (!items.length) items.push(el('li', { class: 'dd-empty' }, 'No sessions yet.'));
    this.list.replaceChildren(...items);

    const projects = this.data?.projects ?? [];
    const chosen = this.select.value;
    this.select.replaceChildren(
      el('option', { value: '' }, `No project (${this.data?.root ?? 'default folder'})`),
      ...projects.filter((p) => p.name !== this.data?.default)
        .map((p) => el('option', { value: p.name, title: p.dir }, p.name)));
    this.select.value = chosen;
  }
}