// <handoff-bar> — the graceful project handoff control (AGENT.md §8.3).
//
// A self-contained control (§1.1): shadow DOM, self-fetching, live over SSE,
// cleans up on disconnect. It lets the user ask Claude to switch to the active
// project, shows the "waiting for a good stopping point" state while a request
// is pending, and announces the completion (with Claude's summary of where it
// left off) when Claude calls ack_switch.

class HandoffBar extends HTMLElement {
  #es = null;
  #controller = null;
  #active = '';
  #pending = null;
  #completed = null;

  constructor() {
    super();
    this.attachShadow({ mode: 'open' });
  }

  connectedCallback() {
    this.#renderShell();
    this.#loadInitial();
    this.#es = new EventSource('/events');
    this.#es.addEventListener('activity', (e) => {
      try { this.#onEvent(JSON.parse(e.data)); } catch { /* ignore */ }
    });
  }

  disconnectedCallback() {
    this.#es?.close();
    this.#controller?.abort();
  }

  async #loadInitial() {
    this.#controller?.abort();
    this.#controller = new AbortController();
    try {
      const [swRes, apRes] = await Promise.all([
        fetch('/api/switch', { signal: this.#controller.signal }),
        fetch('/api/active-project', { signal: this.#controller.signal }),
      ]);
      const sw = await swRes.json();
      const ap = await apRes.json();
      this.#pending = sw.pending ? sw : null;
      this.#active = ap.path || '';
      this.#render();
    } catch (err) {
      if (err.name !== 'AbortError') { /* keep default UI */ }
    }
  }

  #onEvent(ev) {
    switch (ev.kind) {
      case 'switch-requested':
        this.#pending = { target: ev.repo, note: ev.detail };
        this.#completed = null;
        break;
      case 'switch-completed':
        this.#pending = null;
        this.#active = ev.repo || this.#active;
        this.#completed = { target: ev.repo, summary: ev.detail };
        break;
      case 'switch-cancelled':
        this.#pending = null;
        break;
      case 'active-project-changed':
        this.#active = ev.repo || '';
        break;
      default:
        return;
    }
    this.#render();
  }

  async #request() {
    if (!this.#active) return;
    await fetch('/api/switch', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ target: this.#active }),
    }).catch(() => {});
    // The SSE switch-requested event updates the UI.
  }

  async #cancel() {
    await fetch('/api/switch', { method: 'DELETE' }).catch(() => {});
  }

  #render() {
    const body = this.shadowRoot.getElementById('body');
    if (this.#pending) {
      body.innerHTML = `
        <span class="spinner">⏳</span>
        <span>Waiting for Claude to reach a good stopping point to switch to
          <strong>${this.#esc(this.#base(this.#pending.target))}</strong>…</span>
        <button id="cancel" class="ghost">Cancel</button>`;
      this.shadowRoot.getElementById('cancel').onclick = () => this.#cancel();
      return;
    }

    const done = this.#completed
      ? `<span class="done">✅ Claude switched to
           <strong>${this.#esc(this.#base(this.#completed.target))}</strong>${
             this.#completed.summary ? ' — ' + this.#esc(this.#completed.summary) : ''
           }</span>`
      : '';

    if (!this.#active) {
      body.innerHTML = `${done}<span class="hint">Select a repository to make it the active project, then hand it off to Claude.</span>`;
      return;
    }

    body.innerHTML = `
      ${done}
      <button id="ask" class="primary">Ask Claude to switch to ${this.#esc(this.#base(this.#active))}</button>`;
    this.shadowRoot.getElementById('ask').onclick = () => this.#request();
  }

  #renderShell() {
    this.shadowRoot.innerHTML = `
      <style>
        :host { display: block; }
        #body {
          display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
          background: var(--surface-1);
          border: 1px solid var(--border);
          border-radius: var(--radius);
          padding: 10px 14px;
        }
        button { font: inherit; border-radius: var(--radius-sm); cursor: pointer;
                 padding: 5px 12px; border: 1px solid var(--border-strong);
                 background: var(--surface-2); color: var(--color-fg); }
        button.primary { border-color: var(--fill-accent); color: var(--fill-accent); }
        button.ghost { color: var(--color-fg-muted); }
        button:hover { border-color: var(--fill-accent); }
        .spinner { font-size: 15px; }
        .done { color: var(--color-success); }
        .hint { color: var(--color-fg-muted); }
        strong { color: var(--fill-accent); }
        #cancel { margin-left: auto; }
      </style>
      <div id="body"></div>`;
  }

  #base(p) { return String(p).split(/[/\\]/).filter(Boolean).pop() || p; }

  #esc(s) {
    return String(s ?? '').replace(/[&<>"']/g, (c) => (
      { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' }[c]
    ));
  }
}

customElements.define('handoff-bar', HandoffBar);