add theming

internal/report/report.go

@@ -62,6 +62,10 @@ type ReportData struct {
 	// Set when this is a per-day report in split-by-day mode.
 	IndexFile string // non-empty → render "← Back to Index" nav link
 	DayTitle  string // e.g. "2024-02-20", shown in the header
+
+	// Theme selects the visual theme (see themes.go). Empty or unrecognized
+	// falls back to DefaultTheme.
+	Theme string
 }
 
 // DaySummary is one row in the index page's daily breakdown table.
@@ -82,6 +86,10 @@ type IndexData struct {
 	TotalUniqueIPs   int
 	TotalBytes       int64
 	OverallErrorRate float64
+
+	// Theme selects the visual theme (see themes.go). Empty or unrecognized
+	// falls back to DefaultTheme.
+	Theme string
 }
 
 // DayReport bundles one calendar day's fully-computed ReportData with
@@ -110,6 +118,7 @@ func GroupByDay(
 	accessEntries []parser.AccessEntry,
 	errorEntries []parser.ErrorEntry,
 	geoPoints map[string]GeoPoint,
+	themeName string,
 ) []DayReport {
 	accessByDay := make(map[string][]parser.AccessEntry)
 	for _, e := range accessEntries {
@@ -145,6 +154,7 @@ func GroupByDay(
 			GeneratedAt:   time.Now(),
 			AccessEntries: dayAccess,
 			ErrorEntries:  dayErrors,
+			Theme:         themeName,
 		}
 		ComputeStats(&rd)
 
@@ -173,8 +183,21 @@ func GroupByDay(
 	return days
 }
 
+// indexRenderData wraps IndexData with the resolved theme's stylesheet for
+// template execution.
+type indexRenderData struct {
+	IndexData
+	ThemeCSS template.CSS
+}
+
 // GenerateIndexHTML renders the index page from IndexData.
 func GenerateIndexHTML(idx IndexData) (string, error) {
+	th := themeFor(idx.Theme)
+	view := indexRenderData{
+		IndexData: idx,
+		ThemeCSS:  template.CSS(th.CSS),
+	}
+
 	funcMap := template.FuncMap{
 		"formatBytes": func(b int64) string {
 			switch {
@@ -206,7 +229,7 @@ func GenerateIndexHTML(idx IndexData) (string, error) {
 		return "", err
 	}
 	var buf bytes.Buffer
-	if err := tmpl.Execute(&buf, idx); err != nil {
+	if err := tmpl.Execute(&buf, view); err != nil {
 		return "", err
 	}
 	return buf.String(), nil
@@ -295,8 +318,47 @@ func ComputeStats(data *ReportData) {
 	data.TimeSeriesData = ts
 }
 
+// reportRenderData wraps ReportData with the resolved theme's stylesheet and
+// chart/map color values for template execution.
+type reportRenderData struct {
+	ReportData
+	ThemeCSS       template.CSS
+	ThemeExtraCSS  template.CSS
+	ChartFont      string
+	ChartText      string
+	ChartGrid      string
+	Chart1         string
+	Chart2         string
+	Chart2Fill     string
+	Chart3         string
+	ChartWarn      string
+	ChartErr       string
+	MapTileURL     string
+	MapAttribution string
+	MarkerColor    string
+}
+
 // GenerateHTML renders the full HTML report from data.
 func GenerateHTML(data ReportData) (string, error) {
+	th := themeFor(data.Theme)
+	view := reportRenderData{
+		ReportData:     data,
+		ThemeCSS:       template.CSS(th.CSS),
+		ThemeExtraCSS:  template.CSS(th.ExtraCSS),
+		ChartFont:      th.ChartFont,
+		ChartText:      th.ChartText,
+		ChartGrid:      th.ChartGrid,
+		Chart1:         th.Chart1,
+		Chart2:         th.Chart2,
+		Chart2Fill:     th.Chart2Fill,
+		Chart3:         th.Chart3,
+		ChartWarn:      th.ChartWarn,
+		ChartErr:       th.ChartErr,
+		MapTileURL:     th.MapTileURL,
+		MapAttribution: th.MapAttribution,
+		MarkerColor:    th.MarkerColor,
+	}
+
 	funcMap := template.FuncMap{
 		"add": func(a, b int) int { return a + b },
 		"formatBytes": func(b int64) string {
@@ -428,7 +490,7 @@ func GenerateHTML(data ReportData) (string, error) {
 		return "", err
 	}
 	var buf bytes.Buffer
-	if err := tmpl.Execute(&buf, data); err != nil {
+	if err := tmpl.Execute(&buf, view); err != nil {
 		return "", err
 	}
 	return buf.String(), nil