1 files changed, 157 insertions, 0 deletions
diff --git a/web/css.go b/web/css.go
new file mode 100644
index 0000000..e2637bc
--- /dev/null
+++ b/web/css.go
@@ -0,0 +1,157 @@
+// css.go — the stylesheet is generated per site: theme colors become custom
+// properties, one block per scheme, and the per-agent coverage colors are
+// blended from them in the browser so any theme can supply them.
+//
+// Everything switchable is a custom property on :root. That is what lets
+// themes.css hold nothing but one block per theme (writeThemesCSS) and the
+// picker repaint the page by setting a single attribute.
+package web
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+	texttemplate "text/template"
+)
+
+type cssVar struct{ K, V string }
+
+type synCSS struct{ Class string }
+
+type maskCSS struct {
+	Mask uint8
+	Mix  string
+}
+
+func renderCSS(w io.Writer, site *Site) error {
+	css, err := texttemplate.ParseFS(tfs, "assets/style.css.tmpl")
+	if err != nil {
+		return err
+	}
+	keys := syntaxKeys(site.Theme, site.Light)
+	var syn []synCSS
+	for _, k := range keys {
+		syn = append(syn, synCSS{Class: cssKey(k)})
+	}
+	var masks []maskCSS
+	for _, m := range site.masks() {
+		masks = append(masks, maskCSS{Mask: m, Mix: site.maskMix(m)})
+	}
+	return css.Execute(w, map[string]any{
+		"DarkName": site.Theme.Name, "LightName": site.Light.Name,
+		"DarkVars": themeVars(site.Theme, keys), "LightVars": themeVars(site.Light, keys),
+		"Syntax": syn, "Masks": masks,
+	})
+}
+
+// themeVars is one theme as custom properties: its own colors, the syntax
+// colors under the keys the site paints with (resolved along their dots, so a
+// theme that only names "punctuation" still colors brackets), and the agent
+// colors every coverage blend is mixed from.
+func themeVars(t *Theme, keys []string) []cssVar {
+	// bg and panel are what everything else is read against, so they are the
+	// two that may not carry a theme's alpha channel through
+	vars := []cssVar{
+		{"--bg", hex6(t.Bg)}, {"--fg", t.Fg}, {"--panel", hex6(t.Panel)}, {"--border", t.Border},
+		{"--ln", t.LineNo}, {"--muted", t.Muted}, {"--accent", t.Accent},
+		{"--note", t.Note}, {"--hover", t.Hover},
+	}
+	for _, k := range keys {
+		key := resolveKey(t, k)
+		if key == "" {
+			continue
+		}
+		s, c := t.Syntax[key], cssKey(k)
+		vars = append(vars, cssVar{"--s-" + c, s.Color})
+		if s.FontStyle != nil && *s.FontStyle != "" && *s.FontStyle != "normal" {
+			vars = append(vars, cssVar{"--s-" + c + "-fs", *s.FontStyle})
+		}
+		if s.FontWeight != nil && *s.FontWeight > 0 {
+			vars = append(vars, cssVar{"--s-" + c + "-fw", fmt.Sprintf("%.0f", *s.FontWeight)})
+		}
+	}
+	for i := 0; i < maxAgents; i++ {
+		vars = append(vars, cssVar{fmt.Sprintf("--ag%d", i), hex6(t.Player(i))})
+	}
+	return vars
+}
+
+// maskMix is the color of a coverage bitmask: the agent colors it stands for,
+// averaged. The average is written as nested color-mix rather than mixed here,
+// so the same rule holds for every theme the browser can switch to.
+func (s *Site) maskMix(mask uint8) string {
+	var idx []int
+	for i, a := range s.Agents {
+		if a.Bit != 0 && mask&a.Bit != 0 {
+			idx = append(idx, i)
+		}
+	}
+	return mixExpr(idx)
+}
+
+func mixExpr(idx []int) string {
+	switch len(idx) {
+	case 0:
+		return "var(--fg)"
+	case 1:
+		return fmt.Sprintf("var(--ag%d)", idx[0])
+	}
+	return fmt.Sprintf("color-mix(in srgb, var(--ag%d) %.3f%%, %s)",
+		idx[0], 100/float64(len(idx)), mixExpr(idx[1:]))
+}
+
+// ── the switchable themes ─────────────────────────────────────────────────
+
+// writeThemesCSS writes one block per theme found on this machine. It is only
+// fetched once a theme has been picked (or the picker opened), so the page
+// costs nothing for the reader who never switches.
+func writeThemesCSS(w io.Writer, themes []*Theme, keys []string) {
+	fmt.Fprintf(w, "/* %d themes, found on this machine — set data-theme on :root to wear one */\n", len(themes))
+	for _, t := range themes {
+		fmt.Fprintf(w, ":root[data-theme=%q] {\n", t.ID)
+		for _, v := range themeVars(t, keys) {
+			fmt.Fprintf(w, "  %s: %s;\n", v.K, v.V)
+		}
+		scheme := "dark"
+		if t.Appearance == "light" {
+			scheme = "light"
+		}
+		fmt.Fprintf(w, "  color-scheme: %s;\n}\n", scheme)
+	}
+}
+
+// themeCard is a theme as the picker shows it: a name, where it came from, and
+// the few colors that make it recognizable at a glance.
+type themeCard struct {
+	ID   string   `json:"id"`
+	Name string   `json:"name"`
+	Src  string   `json:"src"`
+	Dark bool     `json:"dark"`
+	Sw   []string `json:"sw"`
+}
+
+// writeThemesJS is the picker's menu. It is a script, not JSON, because the
+// static export is opened from the filesystem, where fetch() is not allowed
+// but a <script src> still loads.
+func writeThemesJS(w io.Writer, themes []*Theme) {
+	cards := make([]themeCard, 0, len(themes))
+	for _, t := range themes {
+		syn := func(key string) string {
+			if k := resolveKey(t, key); k != "" {
+				return hex6(t.Syntax[k].Color)
+			}
+			return hex6(t.Fg)
+		}
+		cards = append(cards, themeCard{ID: t.ID, Name: t.Name, Src: t.Source,
+			Dark: t.Appearance != "light",
+			Sw: []string{hex6(t.Bg), hex6(t.Fg), hex6(t.Accent),
+				syn("keyword"), syn("string"), syn("function")}})
+	}
+	b, err := json.Marshal(cards)
+	if err != nil {
+		b = []byte("[]")
+	}
+	fmt.Fprintf(w, "// %d themes, written by notevi from this machine's zed and helix installs\n", len(cards))
+	fmt.Fprintf(w, "window.VRSITE_THEMES=%s;\n", strings.ReplaceAll(string(b), "},{", "},\n{"))
+}