"""
360° panorama viewer for equirectangular (2:1) skybox images.
Returns HTML for use with st.components.v1.html().
Resizes image to keep data URL small so it loads reliably in iframes.
Fetches Pannellum script server-side and inlines it so the client does not load from CDN (avoids CSP/network block).
"""

import base64
import io
import urllib.request
from pathlib import Path

# Max width for viewer image (keeps data URL under ~1MB for reliable loading)
MAX_VIEWER_WIDTH = 1024

# CDN URLs for Pannellum (fetched server-side and inlined)
PANNELLUM_JS_URL = "https://cdn.jsdelivr.net/npm/pannellum@2.5.6/build/pannellum.js"
PANNELLUM_CSS_URL = "https://cdn.jsdelivr.net/npm/pannellum@2.5.6/build/pannellum.css"

# Optional local fallback (if CDN is blocked on server)
_SCRIPT_DIR = Path(__file__).resolve().parent
_PANNELLUM_ASSETS = _SCRIPT_DIR / "panorama_assets"


def _resize_and_encode(image_path: Path) -> tuple[str, str]:
    """Load image, resize to max width (keep 2:1), return (data_url, mime)."""
    from PIL import Image

    img = Image.open(image_path).convert("RGB")
    w, h = img.size
    if w > MAX_VIEWER_WIDTH:
        new_w = MAX_VIEWER_WIDTH
        new_h = max(256, (new_w * h) // w)
        img = img.resize((new_w, new_h), Image.Resampling.LANCZOS)
    buf = io.BytesIO()
    img.save(buf, format="JPEG", quality=85)
    b64 = base64.b64encode(buf.getvalue()).decode("utf-8")
    return f"data:image/jpeg;base64,{b64}", "image/jpeg"


def _fetch_pannellum_assets() -> tuple[str | None, str | None]:
    """Fetch or read Pannellum JS and CSS. Returns (js_content, css_content) or (None, None) on failure."""
    js_content, css_content = None, None

    # Try local assets first (no network)
    js_file = _PANNELLUM_ASSETS / "pannellum.js"
    css_file = _PANNELLUM_ASSETS / "pannellum.css"
    if js_file.exists() and css_file.exists():
        js_content = js_file.read_text(encoding="utf-8", errors="replace")
        css_content = css_file.read_text(encoding="utf-8", errors="replace")
        return js_content, css_content

    # Fetch from CDN (server-side)
    try:
        req = urllib.request.Request(PANNELLUM_JS_URL, headers={"User-Agent": "Mozilla/5.0"})
        with urllib.request.urlopen(req, timeout=10) as r:
            js_content = r.read().decode("utf-8", errors="replace")
    except Exception:
        js_content = None
    try:
        req = urllib.request.Request(PANNELLUM_CSS_URL, headers={"User-Agent": "Mozilla/5.0"})
        with urllib.request.urlopen(req, timeout=10) as r:
            css_content = r.read().decode("utf-8", errors="replace")
    except Exception:
        css_content = None

    return js_content, css_content


def image_to_data_url(image_path: str | Path) -> str:
    """Read image file, resize if needed, return a data URL (base64)."""
    path = Path(image_path)
    if not path.exists():
        return ""
    data_url, _ = _resize_and_encode(path)
    return data_url


def panorama_html(
    image_path: str | Path,
    height_px: int = 480,
    full_page_background: bool = False,
) -> str:
    """
    Build HTML for an interactive 360° panorama viewer (Pannellum).
    image_path: path to equirectangular 2:1 image (e.g. skybox PNG).
    height_px: viewer height in pixels (ignored if full_page_background=True).
    full_page_background: if True, viewer fills 100% of container (use as page background).
    Pannellum JS/CSS are fetched server-side and inlined so the client does not load from CDN.
    """
    path = Path(image_path)
    if not path.exists():
        return f'<p style="padding:1em;color:#888;">Image not found: {path.name}</p>'
    if not path.is_file():
        return f'<p style="padding:1em;color:#888;">Not a file: {path.name}</p>'

    js_content, css_content = _fetch_pannellum_assets()
    if not js_content or not css_content:
        return (
            '<p style="padding:1em;color:#c66;">Viewer unavailable: could not load Pannellum. '
            "Check network or add scripts/panorama_assets/pannellum.js and pannellum.css.</p>"
        )

    try:
        data_url, _ = _resize_and_encode(path)
    except Exception:
        return '<p style="padding:1em;color:#c66;">Could not load image (corrupted or invalid format).</p>'
    data_url_escaped = data_url.replace("\\", "\\\\").replace('"', '\\"').replace("\n", "")

    # Inline script: escape </script> so it does not close our tag
    js_safe = js_content.replace("</script>", "<\\/script>")

    if full_page_background:
        size_style = "html, body { margin: 0; padding: 0; width: 100%; height: 100%; }\n    #panorama { width: 100%; height: 100%; min-height: 100vh; }"
    else:
        size_style = f"body {{ margin: 0; }}\n    #panorama {{ width: 100%; height: {height_px}px; }}"

    return f"""
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <style>
    {size_style}
    .pnlm-container {{ border-radius: 0; }}
    .pnlm-error {{ color: #ccc; padding: 1em; }}
  </style>
  <style>{css_content}</style>
</head>
<body>
  <div id="panorama"></div>
  <script>{js_safe}</script>
  <script>
    (function() {{
      var panoramaUrl = "{data_url_escaped}";
      try {{
        pannellum.viewer('panorama', {{
          type: 'equirectangular',
          panorama: panoramaUrl,
          autoLoad: true,
          showControls: true,
          compass: true,
          mouseZoom: true,
          draggable: true,
          showZoomCtrl: true,
          showFullscreenCtrl: true,
          hfov: 100,
          minHfov: 50,
          maxHfov: 120
        }});
      }} catch (e) {{
        document.getElementById('panorama').innerHTML = '<p class="pnlm-error">Viewer error: ' + e.message + '</p>';
      }}
    }})();
  </script>
</body>
</html>
"""