web: HTML render + embedded themes

1 files changed, 183 insertions, 0 deletions

diff --git a/internal/web/render.go b/internal/web/render.go
new file mode 100644
index 0000000..cf72d41
--- /dev/null
+++ b/internal/web/render.go
@@ -0,0 +1,183 @@
+// Package web renders lectio's daily readings as an HTML fragment and
+// serves a set of "colour only" theme stylesheets (see docs/THEMES.md) that
+// restyle a fixed set of role classes/variables; it never lays out or types
+// anything itself -- that lives in the embedded base.css. It consumes
+// liturgy.Section and render.GatherVersion, never the reverse.
+package web
+
+import (
+	"bytes"
+	"embed"
+	"fmt"
+	"html/template"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+
+	"github.com/lukaszkasprzak/lectio/internal/liturgy"
+	"github.com/lukaszkasprzak/lectio/internal/render"
+)
+
+//go:embed templates
+var templatesFS embed.FS
+
+//go:embed static
+var staticFS embed.FS
+
+// tmpl holds every parsed templates/*.html, keyed by base file name (so
+// "readings.html" is looked up as "readings.html").
+var tmpl = template.Must(template.ParseFS(templatesFS, "templates/*.html"))
+
+// verseNumRe matches a bible verse block's "chapter:verse  " prefix, as
+// produced by render.GatherVersion (e.g. "3:16  Tak bowiem..."). Mirrors
+// internal/tui's verseNumRe.
+var verseNumRe = regexp.MustCompile(`^(\d+:\d+)  (.*)$`)
+
+// sectionView, columnView and blockView are the data readings.html ranges
+// over: one sectionView per liturgy.Section, one columnView per requested
+// version, one blockView per render.GatherVersion block.
+type sectionView struct {
+	Heading, Subtitle, PartID string
+	Columns                   []columnView
+}
+
+type columnView struct {
+	Label  string
+	Blocks []blockView
+}
+
+// blockView is one paragraph or verse line. VNum is set (and Text holds
+// only the verse text) when the block was a bible verse line; otherwise
+// VNum is empty and Text holds the whole block, with Refrain set for a
+// responsorial psalm's deduped first ("pl") block.
+type blockView struct {
+	VNum, Text string
+	Refrain    bool
+}
+
+// RenderReadings builds the reading pane: for each section, a heading (and
+// subtitle if present) followed by one column per version, each built by
+// calling render.GatherVersion(v, sec, lectionary). Heading, citation
+// (subtitle), verse-number and refrain text are wrapped in
+// class="heading|citation|vnum|refrain" spans so theme CSS can restyle
+// them; verse/paragraph text is escaped by html/template.
+func RenderReadings(secs []liturgy.Section, versions []string, lectionary string) template.HTML {
+	views := make([]sectionView, 0, len(secs))
+	for _, sec := range secs {
+		isPsalm := sec.PartID == "psalm"
+
+		cols := make([]columnView, 0, len(versions))
+		for _, v := range versions {
+			label, blocks := render.GatherVersion(v, sec, lectionary)
+
+			bviews := make([]blockView, 0, len(blocks))
+			for bi, b := range blocks {
+				// A bible verse line always carries its "chapter:verse  "
+				// prefix; only text without one (i.e. the "pl" version's
+				// paragraphs) can be the deduped psalm refrain -- matches
+				// internal/tui's styleBlock precedence.
+				if m := verseNumRe.FindStringSubmatch(b); m != nil {
+					bviews = append(bviews, blockView{VNum: m[1], Text: m[2]})
+					continue
+				}
+				bviews = append(bviews, blockView{Text: b, Refrain: isPsalm && bi == 0})
+			}
+			cols = append(cols, columnView{Label: label, Blocks: bviews})
+		}
+
+		views = append(views, sectionView{
+			Heading:  sec.Heading,
+			Subtitle: sec.Subtitle,
+			PartID:   sec.PartID,
+			Columns:  cols,
+		})
+	}
+
+	var buf bytes.Buffer
+	if err := tmpl.ExecuteTemplate(&buf, "readings.html", views); err != nil {
+		// Should be unreachable (the template is embedded and fixed at
+		// build time); degrade to a visible, escaped error rather than
+		// panicking a request handler in the caller.
+		return template.HTML("<p class=\"error\">" + template.HTMLEscapeString(err.Error()) + "</p>")
+	}
+	return template.HTML(buf.String())
+}
+
+// Themes returns the sorted, deduplicated union of the embedded theme
+// stems (static/themes/*.css) and the *.css stems found in the user theme
+// directory (${XDG_CONFIG_HOME:-~/.config}/lectio/themes/); a user theme
+// overrides a built-in of the same name but does not add a second entry.
+func Themes() []string {
+	set := map[string]bool{}
+	for _, name := range themeStems(staticFS, "static/themes") {
+		set[name] = true
+	}
+	if dir, err := userThemesDir(); err == nil {
+		for _, name := range themeStems(os.DirFS(dir), ".") {
+			set[name] = true
+		}
+	}
+
+	names := make([]string, 0, len(set))
+	for name := range set {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
+// themeCSS returns one theme's CSS: the user file
+// ${XDG_CONFIG_HOME:-~/.config}/lectio/themes/<name>.css if it exists,
+// otherwise the embedded static/themes/<name>.css, otherwise an error.
+// name must be a bare file stem (no path separators or "..") -- callers
+// (B2's /theme.css?name= handler) pass this straight through from an HTTP
+// query parameter, so this rejects path traversal rather than trusting it.
+func themeCSS(name string) ([]byte, error) {
+	if name == "" || name != filepath.Base(name) || strings.ContainsAny(name, `/\`) {
+		return nil, fmt.Errorf("web: invalid theme name %q", name)
+	}
+
+	if dir, err := userThemesDir(); err == nil {
+		if b, err := os.ReadFile(filepath.Join(dir, name+".css")); err == nil {
+			return b, nil
+		}
+	}
+
+	b, err := staticFS.ReadFile(path.Join("static", "themes", name+".css"))
+	if err != nil {
+		return nil, fmt.Errorf("web: unknown theme %q", name)
+	}
+	return b, nil
+}
+
+// userThemesDir resolves ${XDG_CONFIG_HOME:-~/.config}/lectio/themes via
+// os.UserConfigDir(), which already honors XDG_CONFIG_HOME on Linux.
+func userThemesDir() (string, error) {
+	dir, err := os.UserConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(dir, "lectio", "themes"), nil
+}
+
+// themeStems lists the *.css stems (base name, no extension) directly in
+// dir of fsys, silently returning none if dir doesn't exist or isn't
+// readable -- a missing user theme directory is normal, not an error.
+func themeStems(fsys fs.FS, dir string) []string {
+	entries, err := fs.ReadDir(fsys, dir)
+	if err != nil {
+		return nil
+	}
+	var names []string
+	for _, e := range entries {
+		if e.IsDir() || !strings.HasSuffix(e.Name(), ".css") {
+			continue
+		}
+		names = append(names, strings.TrimSuffix(e.Name(), ".css"))
+	}
+	return names
+}