// <pr-list> — open pull requests for the selected repo, with "Merge & clean up".
//
// A self-contained control (AGENT.md §1.1): shadow DOM, self-fetching, cleans up
// on disconnect. It listens for `repo:select` and shows the repo's open PRs when
// a forge (Gitea) is configured; otherwise it stays hidden (graceful, §8.4).
// "Merge & clean up" is a DESTRUCTIVE action (§1.4): it confirms — naming the PR,
// base, and branch to be deleted — before calling the server.

class PRList extends HTMLElement {
  #controller = null;
  #onSelect = null;
  #path = '';

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

  connectedCallback() {
    this.#renderShell();
    this.#onSelect = (e) => this.#load(e.detail?.path);
    document.addEventListener('repo:select', this.#onSelect);
  }

  disconnectedCallback() {
    document.removeEventListener('repo:select', this.#onSelect);
    this.#controller?.abort();
  }

  async #load(path) {
    if (!path) return;
    this.#path = path;
    this.#controller?.abort();
    this.#controller = new AbortController();
    try {
      const res = await fetch(`/api/repo/prs?path=${encodeURIComponent(path)}`, { signal: this.#controller.signal });
      const data = await res.json();
      if (!data.supported) { this.hidden = true; return; }
      this.hidden = false;
      this.#render(data.prs || []);
    } catch (err) {
      if (err.name !== 'AbortError') { this.hidden = false; this.#error(err.message); }
    }
  }

  async #merge(pr) {
    const ok = window.confirm(
      `Merge & clean up PR #${pr.number}: "${pr.title}"?\n\n` +
      `This squash-merges it into ${pr.base} and DELETES the branch "${pr.head}".\n` +
      `This cannot be undone.`
    );
    if (!ok) return;
    try {
      const res = await fetch('/api/repo/pr/merge', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ path: this.#path, number: pr.number }),
      });
      const data = await res.json();
      if (!res.ok) throw new Error(data.error || `HTTP ${res.status}`);
      this.#load(this.#path); // refresh the list
    } catch (err) {
      this.#error(`Merge failed: ${err.message}`);
    }
  }

  #render(prs) {
    const body = this.shadowRoot.getElementById('body');
    if (prs.length === 0) {
      body.innerHTML = `<p class="muted">No open pull requests.</p>`;
      return;
    }
    body.replaceChildren(...prs.map((pr) => {
      const li = document.createElement('li');
      li.innerHTML = `
        <div class="row">
          <a class="num" href="${this.#esc(pr.url)}" target="_blank" rel="noopener">#${pr.number}</a>
          <span class="title">${this.#esc(pr.title)}</span>
          ${pr.draft ? `<span class="badge draft">draft</span>` : ''}
        </div>
        <div class="meta">
          ${this.#esc(pr.author)} · <code>${this.#esc(pr.head)}</code> → <code>${this.#esc(pr.base)}</code>
          ${pr.sameRepo ? '' : `<span class="badge fork">fork</span>`}
        </div>`;
      const btn = document.createElement('button');
      btn.textContent = 'Merge & clean up';
      btn.className = 'merge';
      btn.title = pr.draft ? 'This PR is a draft' : 'Squash-merge and delete the branch';
      btn.onclick = () => this.#merge(pr);
      li.querySelector('.row').appendChild(btn);
      return li;
    }));
  }

  #error(msg) {
    this.shadowRoot.getElementById('body').innerHTML = `<p class="error">${this.#esc(msg)}</p>`;
  }

  #renderShell() {
    this.shadowRoot.innerHTML = `
      <style>
        :host { display: block; }
        .box { background: var(--surface-1); border: 1px solid var(--border);
               border-radius: var(--radius); padding: 14px 16px; }
        h3 { font-size: 12px; text-transform: uppercase; letter-spacing: .04em;
             color: var(--color-fg-muted); margin: 0 0 8px; }
        ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
        li { border-top: 1px solid var(--border); padding-top: 8px; }
        li:first-child { border-top: none; padding-top: 0; }
        .row { display: flex; align-items: center; gap: 8px; }
        .num { color: var(--fill-accent); text-decoration: none; font-weight: 600; }
        .title { flex: 1; }
        .meta { color: var(--color-fg-muted); font-size: 12px; margin-top: 2px; }
        code { background: var(--surface-2); padding: 0 5px; border-radius: var(--radius-sm); }
        .badge { font-size: 11px; padding: 0 6px; border-radius: var(--radius-sm);
                 border: 1px solid var(--border-strong); }
        .draft { color: var(--color-warning); border-color: var(--color-warning); }
        .fork { color: var(--color-fg-muted); margin-left: 6px; }
        button.merge { font: inherit; cursor: pointer; padding: 4px 10px;
          border-radius: var(--radius-sm); border: 1px solid var(--color-danger);
          color: var(--color-danger); background: transparent; }
        button.merge:hover { background: var(--color-danger-bg); }
        .muted { color: var(--color-fg-muted); }
        .error { color: var(--color-danger); }
      </style>
      <div class="box">
        <h3>Pull requests</h3>
        <div id="body"><p class="muted">Select a repository.</p></div>
      </div>`;
  }

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

customElements.define('pr-list', PRList);