writeonce/docs/examples/wo-html/html.wo

-- wo-html — server-rendered HTML as plain Text. Three layers, all pure:
--   esc()        HTML-escape untrusted text (the ONLY defense: use it on
--                everything that did not come from your own code)
--   el()/...     element builders — `el("h1", "text-3xl font-bold", t)`
--   tw_css()     a Tailwind-style utility stylesheet: the same class
--                names Tailwind popularized, hand-written as one static
--                sheet, inlined by page() so a page is one self-contained
--                response — no CDN, no build step, no JS
--
-- The language has no varargs and no closures (doctrine), so builders
-- take exactly (tag, classes, inner) and pages compose by `..` and by
-- functions returning Text. That constraint is the demo: an HTML layer
-- in writeonce is ordinary code, not a template dialect.

-- HTML-escape: & < > " (the four that matter in text and attributes).
pub fn esc(t: Text) -> Text {
  let out = "";
  let i = 0;
  let n = len(t);
  while i < n {
    let b = byte_at(t, i);
    if b == 38 { out = out .. "&amp;"; }
    else {
      if b == 60 { out = out .. "&lt;"; }
      else {
        if b == 62 { out = out .. "&gt;"; }
        else {
          if b == 34 { out = out .. "&quot;"; }
          else { out = out .. substr(t, i, 1); }
        }
      }
    }
    i = i + 1;
  }
  return out;
}

-- One element. Empty class list = no attribute. The inner text is the
-- CALLER's business: pass esc(user_text) for data, raw markup for
-- fragments you built yourself.
pub fn el(tag: Text, cls: Text, inner: Text) -> Text {
  if cls == "" { return "<${tag}>${inner}</${tag}>"; }
  return "<${tag} class=\"${cls}\">${inner}</${tag}>";
}

-- An anchor: href is attribute context, so it is escaped here.
pub fn link(href: Text, cls: Text, label: Text) -> Text {
  if cls == "" { return "<a href=\"${esc(href)}\">${label}</a>"; }
  return "<a href=\"${esc(href)}\" class=\"${cls}\">${label}</a>";
}

-- A code block: content is ALWAYS escaped — code samples are exactly the
-- text that breaks HTML otherwise.
pub fn code_block(src: Text) -> Text {
  return el("pre", "code-block", el("code", "", esc(src)));
}

pub fn text_input(name: Text, value: Text) -> Text {
  return "<input type=\"text\" name=\"${esc(name)}\" value=\"${esc(value)}\" class=\"field\">";
}

pub fn text_area(name: Text, value: Text, rows: Int) -> Text {
  return "<textarea name=\"${esc(name)}\" rows=\"${rows}\" class=\"field\">${esc(value)}</textarea>";
}

pub fn submit_btn(label: Text) -> Text {
  return "<button type=\"submit\" class=\"btn\">${esc(label)}</button>";
}

pub fn form_post(action: Text, inner: Text) -> Text {
  return "<form method=\"POST\" action=\"${esc(action)}\" class=\"flex flex-col gap-2\">${inner}</form>";
}

-- The utility sheet. Tailwind's names, one hand-written static sheet —
-- only the utilities this ecosystem's pages actually use; growing it is
-- adding a line, not adopting a toolchain. `.code-block`, `.field` and
-- `.btn` are the three composites the builders above rely on.
pub fn tw_css() -> Text {
  let c = "*{box-sizing:border-box;margin:0;padding:0}";
  c = c .. "body{font-family:system-ui,sans-serif;background:#f9fafb;color:#111827;line-height:1.6}";
  c = c .. ".mx-auto{margin-left:auto;margin-right:auto}";
  c = c .. ".max-w-3xl{max-width:48rem}";
  c = c .. ".p-4{padding:1rem}.p-6{padding:1.5rem}.px-4{padding-left:1rem;padding-right:1rem}";
  c = c .. ".py-2{padding-top:.5rem;padding-bottom:.5rem}.py-8{padding-top:2rem;padding-bottom:2rem}";
  c = c .. ".mb-2{margin-bottom:.5rem}.mb-4{margin-bottom:1rem}.mb-8{margin-bottom:2rem}";
  c = c .. ".mt-4{margin-top:1rem}.mt-8{margin-top:2rem}";
  c = c .. ".flex{display:flex}.flex-col{flex-direction:column}";
  c = c .. ".items-center{align-items:center}.justify-between{justify-content:space-between}";
  c = c .. ".gap-2{gap:.5rem}.gap-4{gap:1rem}";
  c = c .. ".text-sm{font-size:.875rem}.text-lg{font-size:1.125rem}";
  c = c .. ".text-xl{font-size:1.25rem}.text-2xl{font-size:1.5rem}.text-3xl{font-size:1.875rem}";
  c = c .. ".font-bold{font-weight:700}.font-mono{font-family:ui-monospace,monospace}";
  c = c .. ".text-gray-500{color:#6b7280}.text-gray-700{color:#374151}.text-gray-900{color:#111827}";
  c = c .. ".text-blue-600{color:#2563eb}.text-white{color:#fff}";
  c = c .. ".bg-white{background:#fff}.bg-gray-50{background:#f9fafb}";
  c = c .. ".bg-gray-900{background:#111827}.bg-blue-600{background:#2563eb}";
  c = c .. ".rounded{border-radius:.25rem}.rounded-lg{border-radius:.5rem}";
  c = c .. ".border{border:1px solid #e5e7eb}.shadow-sm{box-shadow:0 1px 2px rgba(0,0,0,.05)}";
  c = c .. ".block{display:block}.w-full{width:100%}.leading-relaxed{line-height:1.75}";
  c = c .. ".underline{text-decoration:underline}.no-underline{text-decoration:none}";
  c = c .. ".list-disc{list-style:disc}.pl-6{padding-left:1.5rem}";
  c = c .. "a{color:#2563eb;text-decoration:none}a:hover{text-decoration:underline}";
  c = c .. ".code-block{background:#111827;color:#e5e7eb;padding:1rem;border-radius:.5rem;";
  c = c .. "overflow-x:auto;font-size:.875rem;line-height:1.6;margin:1rem 0}";
  c = c .. ".code-block code{font-family:ui-monospace,monospace;white-space:pre}";
  c = c .. ".field{display:block;width:100%;border:1px solid #e5e7eb;border-radius:.25rem;";
  c = c .. "padding:.5rem;font-family:ui-monospace,monospace;font-size:.875rem}";
  c = c .. ".btn{background:#2563eb;color:#fff;border:0;border-radius:.25rem;";
  c = c .. "padding:.5rem 1rem;font-weight:700;cursor:pointer}";
  return c;
}

-- One full document: the sheet inlined, viewport set, body handed in.
-- Self-contained by construction — view-source shows everything.
pub fn page(title: Text, body: Text) -> Text {
  let d = "<!doctype html><html><head><meta charset=\"utf-8\">";
  d = d .. "<meta name=\"viewport\" content=\"width=device-width,initial-scale=1\">";
  d = d .. "<title>${esc(title)}</title>";
  d = d .. "<style>${tw_css()}</style></head><body>";
  d = d .. body;
  d = d .. "</body></html>";
  return d;
}