import { OFFLINE_DATA_ICON } from "/js/icons.js";
import { notifySidePanelOpen, onlyOneSidePanelOpen } from "/js/panels.js";
import { isLoggedIn } from "/js/auth.js";

const POLL_INTERVAL_MS = 3000;

function formatBytes(bytes) {
  const mb = bytes / (1024 * 1024);
  return mb >= 1024 ? `${(mb / 1024).toFixed(1)} GB` : `${mb.toFixed(1)} MB`;
}

// One row of the Offline data panel — status text plus a "Regenerate for
// current view" button, for either offline.pmtiles or terrain.pmtiles.
// Both files behave identically from here (same status/build/build-status
// endpoint shape, see lib/maptool/pmtiles_builder.rb), just against
// different URLs/labels, so one class covers both rather than writing the
// same fetch/poll logic twice.
class DataFileRow {
  constructor(map, { label, statusUrl, buildUrl, buildStatusUrl }) {
    this._map = map;
    this._label = label;
    this._statusUrl = statusUrl;
    this._buildUrl = buildUrl;
    this._buildStatusUrl = buildStatusUrl;
    this._exists = false;
  }

  mount(container) {
    const row = document.createElement("div");
    row.className = "offline-data-panel__row";
    row.innerHTML = `
      <div class="offline-data-panel__row-header">
        <strong>${this._label}</strong>
        <button type="button" class="offline-data-panel__build">Regenerate for current view</button>
      </div>
      <p class="offline-data-panel__status">Checking…</p>
    `;
    this._buildButton = row.querySelector(".offline-data-panel__build");
    this._statusEl = row.querySelector(".offline-data-panel__status");
    // Viewing status works for anyone; only triggering a build needs a
    // login — same finer-grained gating measure.js/gpx.js use for their
    // own write-only affordances, rather than hiding this whole control.
    this._buildButton.hidden = !isLoggedIn();
    this._buildButton.addEventListener("click", () => this._build());

    container.appendChild(row);
    this._refreshStatus();
  }

  async _refreshStatus() {
    let data;
    try {
      data = await (await fetch(this._statusUrl)).json();
    } catch {
      this._statusEl.textContent = "Could not check status.";
      return;
    }
    this._exists = data.available;
    this._statusEl.textContent = data.available
      ? `${formatBytes(data.size)} · updated ${new Date(data.mtime).toLocaleString([], { dateStyle: "short", timeStyle: "short" })}`
      : "Not generated yet.";
  }

  async _build() {
    if (this._exists && !window.confirm(`Replace the existing ${this._label.toLowerCase()} with a fresh build for the current view?`)) {
      return;
    }

    const bounds = this._map.getBounds();
    const body = new URLSearchParams({
      south: bounds.getSouth(),
      west: bounds.getWest(),
      north: bounds.getNorth(),
      east: bounds.getEast(),
    });

    this._buildButton.disabled = true;
    this._statusEl.textContent = "Starting…";
    try {
      const response = await fetch(this._buildUrl, { method: "POST", body });
      const data = await response.json().catch(() => ({}));
      if (!response.ok) throw new Error(data.error || `build failed: ${response.status}`);
    } catch (err) {
      this._statusEl.textContent = err.message;
      this._buildButton.disabled = false;
      return;
    }

    this._statusEl.textContent = "Building…";
    this._poll();
  }

  // Self-rescheduling setTimeout loop, same shape as livetrack.js's
  // _scheduleRefresh — check status, only reschedule while still running.
  _poll() {
    setTimeout(async () => {
      let status;
      try {
        status = await (await fetch(this._buildStatusUrl)).json();
      } catch {
        this._poll(); // transient failure — try again next tick
        return;
      }

      if (status.state === "running") {
        this._poll();
        return;
      }

      this._buildButton.disabled = false;
      if (status.state === "error") {
        this._statusEl.textContent = `Build failed: ${status.message}`;
      } else {
        this._refreshStatus();
      }
    }, POLL_INTERVAL_MS);
  }
}

// A sidebar panel wrapping the manual go-pmtiles workflow
// docs/development.adoc documents — "Regenerate for current view" on
// either file shells out to it server-side instead of an admin running it
// by hand (see lib/maptool/pmtiles_builder.rb). No area-picker: the
// current map viewport is the region, same convention the Overpass POI
// plugin already uses for "give me a bbox."
export class OfflineDataControl {
  constructor(map) {
    this._rows = [
      new DataFileRow(map, {
        label: "Offline map data",
        statusUrl: "/api/offline-tiles",
        buildUrl: "/api/offline-tiles/build",
        buildStatusUrl: "/api/offline-tiles/build-status",
      }),
      new DataFileRow(map, {
        label: "Offline terrain data",
        statusUrl: "/api/terrain-tiles",
        buildUrl: "/api/terrain-tiles/build",
        buildStatusUrl: "/api/terrain-tiles/build-status",
      }),
    ];
  }

  mount(sidebar) {
    this._container = document.createElement("div");
    this._container.className = "sidebar-item";
    this._container.innerHTML = `<button type="button" class="sidebar-icon" title="Offline data" aria-label="Offline data">${OFFLINE_DATA_ICON}</button>`;
    this._icon = this._container.querySelector(".sidebar-icon");
    this._icon.addEventListener("click", () => this._togglePanel());

    this._panel = document.getElementById("offline-data-panel");
    this._panel.querySelector(".basemap-panel__close").addEventListener("click", () => this._togglePanel(false));

    const body = this._panel.querySelector(".offline-data-panel__body");
    this._rows.forEach((row) => row.mount(body));

    onlyOneSidePanelOpen(this._panel, () => this._icon.classList.remove("active"));

    sidebar.appendChild(this._container);
  }

  _togglePanel(force) {
    const open = force === undefined ? this._panel.hidden : force;
    this._panel.hidden = !open;
    this._icon.classList.toggle("active", open);
    if (open) notifySidePanelOpen(this._panel);
  }
}