# Copyright 2026 Hugging Face
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Self-contained "Metrics" explainer page for the Space.

Builds one static, dependency-free HTML document explaining how a
candidate STEP is scored: the validity gate, the three orthogonal
axes (shape / topology / interface), and the editing renormalization.

It is curated (a Space-tailored summary, deliberately a little
duplicated from the canonical ``docs/metrics*`` in the code repo)
rather than rendered from those markdown files, because the docs use
repo-relative links + local illustration images that don't resolve
when hosted. The page links out to the GitHub deep-dives for the full
derivations, so the canonical source of truth stays there.

The page is served two ways from the same builder
(:func:`build_metrics_page`):

- as a standalone route ``/metrics`` (so the per-submission report's
  headline metric pills can deep-link to ``/metrics#<anchor>``), and
- embedded in the "Metrics" Gradio tab via an iframe.

Formulas are plain monospace blocks (no MathJax / KaTeX), so the page
renders identically online and offline with no network dependency. The
anchor ids are a published contract the report links against; see
:data:`METRIC_ANCHORS`.
"""
from __future__ import annotations

# Section anchor ids. The per-submission report's headline pills link to
# ``/metrics#<anchor>``; keep these stable (and in sync with the
# report's pill links in cadgenbench's single_run.py).
METRIC_ANCHORS = {
    "cad_score": "cad-score",
    "shape": "shape-similarity",
    "interface": "interface-match",
    "topology": "topology-match",
    "validity": "validity",
    "editing": "editing",
}

# Canonical deep-dive docs live in the code repo; linked from each
# section so the Space page stays a summary and the full derivations
# have one source of truth.
_DOCS_BASE = "https://github.com/huggingface/cadgenbench/blob/main/docs"

# Bundled illustration served by the Space (see app.py's /metrics-assets
# route). Relative so it resolves same-origin whether the page is the
# standalone /metrics route or the iframe in the Metrics tab.
_MATING_GROUP_IMG = "/metrics-assets/mating_group.webp"

_CSS = """\
* { box-sizing: border-box; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
       max-width: 960px; margin: 0 auto; padding: 24px 20px 80px;
       background: #f8f9fa; color: #1f2430; line-height: 1.55; }
a { color: #1565c0; }
h1 { font-size: 1.7em; margin: 0 0 4px; }
.lede { color: #5b6170; margin: 0 0 20px; }
.card { background: #fff; border: 1px solid #e3e5ea; border-radius: 12px;
        padding: 20px 24px; margin: 16px 0; box-shadow: 0 1px 3px rgba(0,0,0,0.05);
        scroll-margin-top: 16px; }
.card h2 { margin: 0 0 10px; font-size: 1.2em; display: flex; align-items: baseline;
           gap: 10px; }
.card h3 { font-size: 0.98em; margin: 16px 0 4px; color: #37474f; }
.axis-tag { font-family: monospace; font-size: 0.62em; font-weight: 700;
            text-transform: uppercase; letter-spacing: 0.04em; padding: 3px 8px;
            border-radius: 6px; }
.t-cad { border-left: 5px solid #37474f; }
.t-cad .axis-tag { background: #eceff1; color: #37474f; }
.t-shape { border-left: 5px solid #1565c0; }
.t-shape .axis-tag { background: #e3f2fd; color: #1565c0; }
.t-iface { border-left: 5px solid #4527a0; }
.t-iface .axis-tag { background: #ede7f6; color: #4527a0; }
.t-topo { border-left: 5px solid #006d77; }
.t-topo .axis-tag { background: #d8f3f4; color: #006d77; }
.t-gate { border-left: 5px solid #c62828; }
.t-gate .axis-tag { background: #ffebee; color: #c62828; }
.t-edit { border-left: 5px solid #9e7700; }
.t-edit .axis-tag { background: #fff9c4; color: #9e7700; }
pre.formula { background: #0f1525; color: #e7ecf5; border-radius: 8px;
              padding: 14px 16px; overflow-x: auto; font-size: 0.86em;
              line-height: 1.5; margin: 10px 0; }
code { background: #eef0f4; padding: 1px 5px; border-radius: 4px;
       font-size: 0.88em; }
table { border-collapse: collapse; width: 100%; margin: 12px 0; font-size: 0.92em; }
th, td { border: 1px solid #e3e5ea; padding: 7px 10px; text-align: left; }
th { background: #f5f7fa; }
.deep { font-size: 0.9em; color: #5b6170; margin: 20px 0 0; }
.endspace { height: 60vh; }
.toc { background: #fff; border: 1px solid #e3e5ea; border-radius: 12px;
       padding: 14px 20px; margin: 16px 0; }
.toc ul { margin: 6px 0 0; padding-left: 18px; }
.note { color: #5b6170; font-size: 0.92em; }
figure.fig { margin: 14px 0; }
figure.fig img { display: block; width: 100%; max-width: 520px; height: auto;
                 border: 1px solid #e3e5ea; border-radius: 10px; background: #fff; }
figure.fig figcaption { font-size: 0.84em; color: #5b6170; margin-top: 6px;
                        max-width: 560px; }
.weight-pill { font-family: monospace; font-size: 0.8em; padding: 1px 7px;
               border-radius: 6px; background: #eceff1; color: #37474f; }
@media (max-width: 760px) {
  /* Tighten the reading frame for phones. The end-spacer stays (vh of the
     bounded mobile iframe) so the last "On this page" target can scroll to the
     top of the box. */
  body { padding: 16px 14px 28px; }
  h1 { font-size: 1.5em; }
  .card { padding: 16px 16px; }
  .card h2 { font-size: 1.12em; }
  pre.formula { font-size: 0.78em; padding: 12px 13px; }
  table { font-size: 0.86em; }
  th, td { padding: 6px 8px; }
}
"""


def _section(
    *, anchor: str, css_class: str, tag: str, title: str, body: str,
) -> str:
    return (
        f'<section class="card {css_class}" id="{anchor}">'
        f'<h2><span class="axis-tag">{tag}</span>{title}</h2>'
        f"{body}"
        "</section>"
    )


def build_metrics_page() -> str:
    """Return the full self-contained Metrics explainer HTML document."""
    a = METRIC_ANCHORS

    overview = _section(
        anchor=a["cad_score"],
        css_class="t-cad",
        tag="CAD Score",
        title="How one part is scored",
        body=(
            "<p>CADGenBench scores a generated part (a STEP file) against one "
            "ground-truth STEP. First a hard <b>validity gate</b>; if it "
            "passes, the <b>CAD Score</b> is a weighted mean of three "
            "independent metrics, each in [0, 1].</p>"
            '<pre class="formula">'
            "cad_score = 0                                                if not valid\n"
            "          = 0.4*shape + 0.4*interface + 0.2*topology          otherwise"
            "</pre>"
            "<p class='note'>(This is the <b>generation</b> composition. "
            "<b>Editing</b> tasks renormalize the shape axis and reweight; "
            f'see <a href="#{a["editing"]}">Editing tasks</a> below.)</p>'
            "<table><thead><tr><th>Component</th><th>Range</th>"
            "<th>What it asks</th></tr></thead><tbody>"
            f'<tr><td><a href="#{a["validity"]}">CAD Validity</a> (gate)</td>'
            "<td>{0, 1}</td><td>Is the geometry valid?</td></tr>"
            f'<tr><td><a href="#{a["shape"]}">Shape Similarity</a></td>'
            "<td>[0, 1]</td><td>Does the bulk geometry match?</td></tr>"
            f'<tr><td><a href="#{a["topology"]}">Topology Match</a></td>'
            "<td>[0, 1]</td><td>Same pieces / holes / voids?</td></tr>"
            f'<tr><td><a href="#{a["interface"]}">Interface Match</a></td>'
            "<td>[0, 1]</td><td>Does it bolt up to the same fixture?</td></tr>"
            "</tbody></table>"
            "<h3>Why three axes</h3>"
            "<p>They are orthogonal by construction: each catches errors the "
            "others are blind to:</p>"
            "<ul>"
            "<li><b>Shape</b> catches wrong bulk geometry; blind to topology.</li>"
            "<li><b>Topology</b> catches wrong hole / piece / void counts; blind "
            "to feature position.</li>"
            "<li><b>Interface</b> catches a misplaced / mis-sized mating feature; "
            "blind to overall shape.</li>"
            "</ul>"
            "<p class='note'>Outputs are rigidly aligned to the ground truth "
            "(rotation + translation only, never scale) before scoring.</p>"
        ),
    )

    validity = _section(
        anchor=a["validity"],
        css_class="t-gate",
        tag="Gate",
        title="CAD Validity",
        body=(
            "<p>Runs before every other metric on the raw candidate STEP. Any "
            "failure sets <code>is_valid = False</code> and forces "
            "<code>cad_score = 0</code>, so an invalid solid never beats a worse "
            "but valid one. Passing requires all of:</p>"
            "<ol>"
            "<li><b>Well-formed BREP</b>: no per-face / edge / vertex errors "
            "(self-intersecting wires, edges off their surface, etc.).</li>"
            "<li><b>Watertight</b>: every shell is closed; no naked or free "
            "edges.</li>"
            "<li><b>Meshable as a closed orientable manifold</b>: tessellates "
            "to a manifold, closed (3F = 2E), orientation-consistent triangle "
            "mesh.</li>"
            "</ol>"
        ),
    )

    shape = _section(
        anchor=a["shape"],
        css_class="t-shape",
        tag="Shape",
        title="Shape Similarity",
        body=(
            "<p>Does the bulk geometry match? The mean of two complementary "
            "sub-metrics, each in [0, 1]:</p>"
            '<pre class="formula">'
            "shape_similarity = 0.5 * (surface_distance_F1 + volume_IoU)"
            "</pre>"
            "<h3>Surface Distance F1</h3>"
            "<p>Checks the candidate's surface sits where the GT's does and "
            "faces the same way. Points are sampled across both surfaces with "
            "their outward normals; a point matches when the closest point on "
            "the other mesh's surface is within 0.5% of the GT bounding-box "
            "diagonal <b>and</b> the normals agree to within 20°. Precision and "
            "recall combine into F1.</p>"
            "<h3>Volume IoU</h3>"
            "<p>Shared volume of the two solids over their combined volume "
            "(intersection over union).</p>"
            "<p class='note'>Both use a tolerance proportional to part size, so "
            "small features can move without shifting the score; those are "
            f'covered by <a href="#{a["interface"]}">interface match</a>.</p>'
        ),
    )

    topology = _section(
        anchor=a["topology"],
        css_class="t-topo",
        tag="Topo",
        title="Topology Match",
        body=(
            "<p>Does the candidate have the same number of pieces, "
            "through-holes, and internal voids? It compares the three "
            "<b>Betti numbers</b> of the solid:</p>"
            "<ul>"
            "<li><b>b&#8320;</b>: connected solid components.</li>"
            "<li><b>b&#8321;</b>: independent through-handles.</li>"
            "<li><b>b&#8322;</b>: enclosed internal voids (cavities).</li>"
            "</ul>"
            "<p>Each axis gets a fuzzy log-ratio against GT, sharpened by "
            "&#945; = 2, and the three are <b>multiplied</b>:</p>"
            '<pre class="formula">'
            "s_i = ((min(cand,gt) + 1) / (max(cand,gt) + 1)) ^ 2\n"
            "topology_match = s_0 * s_1 * s_2"
            "</pre>"
            "<p>The product means one wrong count collapses the "
            "score: topology is discrete, so two of three right is not a partial "
            "match. Example: GT (1,2,0) vs candidate (1,4,0) scores "
            "(3/5)&#178; = 0.36. Blind features (blind pockets, fillets, "
            "chamfers) are topologically trivial and covered by the other "
            "axes.</p>"
        ),
    )

    interface = _section(
        anchor=a["interface"],
        css_class="t-iface",
        tag="Interface",
        title="Interface Match",
        body=(
            "<p>Would it bolt up to the same fixture? Each mating feature is a "
            "region of space the candidate must match in shape, size, and "
            "position:</p>"
            "<ul>"
            "<li><b>Keep-out (KOR)</b>: must be empty (a bolt hole, a slot).</li>"
            "<li><b>Keep-in (KIR)</b>: must be solid (a locating boss, a "
            "pin).</li>"
            "</ul>"
            "<h3>Mating groups</h3>"
            "<p>The features that must seat together against a single fixture "
            "form one <b>mating group</b>: here, two bolt holes and a slot that "
            "one jig drops into. A part can have several independent groups (say "
            "a bolt pattern on one face and a boss on another), and each group "
            "is scored on its own.</p>"
            '<figure class="fig">'
            f'<img src="{_MATING_GROUP_IMG}" loading="lazy" '
            'alt="A jig with two pins and a slot key seating into a part\'s two '
            'bolt holes and slot">'
            "<figcaption>A mating group: a jig with two pins and a slot key "
            "seats into the part's two bolt holes and slot. The candidate has "
            "to fit the same fixture.</figcaption>"
            "</figure>"
            "<h3>Scoring</h3>"
            "<p>Per group:</p>"
            "<ol>"
            "<li><b>Per-feature fit</b>: volumetric IoU against the region "
            "(with a thin shell of opposite material, so both oversize and "
            "undersize lose points).</li>"
            "<li><b>Bounded pose search</b>: &#177;1&#176; and &#177;1% of part "
            "size per axis, so a feature isn't penalized for the residual of "
            "whole-part alignment.</li>"
            "<li><b>Pass/fail ramp</b>: IoU &#8805; 0.95 &#8594; 1, &#8804; 0.80 "
            "&#8594; 0, linear between; a sloppy fit scores 0.</li>"
            "</ol>"
            "<p>A group scores as its <b>worst</b> feature (the minimum); the "
            "fixture scores as the <b>mean</b> over its groups, so nailing one "
            "interface and missing another still earns partial credit.</p>"
        ),
    )

    editing = _section(
        anchor=a["editing"],
        css_class="t-edit",
        tag="Editing",
        title="Editing tasks: no-op renormalization",
        body=(
            "<p>Editing fixtures ship an <code>input.step</code> plus an edit "
            "request; the GT is a small change to that input. Since all three "
            "axes measure global similarity, submitting the input unchanged "
            "(the <b>no-op</b>) already scores high, so the raw composition "
            "would reward doing nothing.</p>"
            "<p>The fix renormalizes the <b>shape</b> axis against the no-op "
            "baseline <code>b = shape_similarity(input, GT)</code>:</p>"
            '<pre class="formula">'
            "s_renorm  = max(0, (shape_similarity - b) / (1 - b))\n"
            "cad_score = 0.6*s_renorm + 0.3*interface + 0.1*topology   (0 if not valid)"
            "</pre>"
            "<p>This maps the no-op to 0 and a perfect candidate to 1. Topology "
            "and interface stay raw (most edits leave them unchanged). A no-op "
            "therefore caps at 0.3 + 0.1 = 0.4, and any real shape improvement "
            "clears it.</p>"
        ),
    )

    toc = (
        '<nav class="toc"><b>On this page</b><ul>'
        f'<li><a href="#{a["cad_score"]}">CAD Score: how one part is scored</a></li>'
        f'<li><a href="#{a["validity"]}">CAD Validity (gate)</a></li>'
        f'<li><a href="#{a["shape"]}">Shape Similarity</a></li>'
        f'<li><a href="#{a["topology"]}">Topology Match</a></li>'
        f'<li><a href="#{a["interface"]}">Interface Match</a></li>'
        f'<li><a href="#{a["editing"]}">Editing tasks</a></li>'
        "</ul></nav>"
    )

    footer = (
        '<p class="deep">For the full definitions and derivations, see the '
        f'metrics reference in the code: '
        f'<a href="{_DOCS_BASE}/metrics.md" target="_blank" rel="noopener">'
        "docs/metrics.md</a>.</p>"
        # Trailing space so the last section can scroll to the top of the
        # viewport when reached via an in-page anchor (e.g. the "Editing
        # tasks" link); without it a near-bottom target lands mid-screen.
        '<div class="endspace" aria-hidden="true"></div>'
    )

    return (
        "<!DOCTYPE html><html lang='en'><head>"
        "<meta charset='utf-8'>"
        "<meta name='viewport' content='width=device-width, initial-scale=1'>"
        "<title>CADGenBench Metrics</title>"
        f"<style>{_CSS}</style>"
        "</head><body>"
        "<h1>Metrics</h1>"
        "<p class='lede'>How CADGenBench scores one generated CAD part against "
        "the ground truth. These metrics are new, so this page explains each "
        "one.</p>"
        f"{toc}{overview}{validity}{shape}{topology}{interface}{editing}"
        f"{footer}"
        f"<script>{_JS}</script>"
        "</body></html>"
    )


# Mobile sizing for the embedding iframe.
#
# We deliberately give the phone iframe its OWN bounded height (an internal
# scroll) rather than auto-sizing it to the full content. Reason: when embedded
# on huggingface.co the Space sits in a cross-origin outer frame that owns the
# real scroll, so a content-sized iframe can't be scrolled from inside -- which
# silently breaks the "On this page" anchor links (scrollIntoView has nothing it
# is allowed to move). A bounded iframe scrolls its own document, so the anchors
# work again. Desktop keeps its fixed CSS height (reads well there).
#
# Anchor clicks use scrollIntoView (smooth, scrolls whichever ancestor actually
# scrolls -- the bounded iframe when embedded, the window on the standalone
# /metrics route). All wrapped in try/catch: frameElement access is fine for
# this same-origin iframe but must never throw if that ever changes.
_JS = """
(function () {
  var narrow = (window.innerWidth || 1000) < 760;
  function fit() {
    if (!narrow) return;
    try {
      var fe = window.frameElement;
      if (!fe) return;                       // standalone /metrics: window scrolls
      var avail = (window.screen && window.screen.availHeight) || 740;
      var h = Math.max(340, Math.min(640, Math.round(avail - 360)));
      fe.style.height = h + 'px';            // bounded -> the iframe scrolls itself
    } catch (e) { /* keep the CSS fallback height */ }
  }
  document.addEventListener('click', function (e) {
    var a = e.target && e.target.closest ? e.target.closest('a[href^="#"]') : null;
    if (!a) return;
    var el = document.getElementById(a.getAttribute('href').slice(1));
    if (el) { e.preventDefault(); el.scrollIntoView({ behavior: 'smooth', block: 'start' }); }
  });
  window.addEventListener('load', fit);
  window.addEventListener('resize', function () { narrow = (window.innerWidth || 1000) < 760; fit(); });
  fit();
})();
"""