Implement HTML writer (#33)

Reviewed-on: #33
Co-authored-by: Natercio Moniz <[email protected]>

internal/writing/html/fragment.go

@@ -0,0 +1,69 @@
+package html
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jedib0t/go-pretty/v6/table"
+	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/writing/internal/tabledef"
+)
+
+// htmlCSSClass is the CSS class list put on the rendered report table.
+const htmlCSSClass = "table table-striped table-hover table-bordered"
+
+// widthIndex is the weight of the auto-index (row number) column; the other
+// column weights come from tabledef's width budgets.
+const widthIndex = 6
+
+// htmlColumnWeights lists one weight per rendered column, starting with the
+// auto-index column, mirroring the column order of tabledef.Build so the
+// HTML table keeps columns in the same strict proportion to each other as
+// the terminal layout.
+var htmlColumnWeights = []int{
+	widthIndex,
+	tabledef.WidthCountry, tabledef.WidthOther, tabledef.WidthOther, tabledef.WidthOther, tabledef.WidthOther, tabledef.WidthEuros,
+	tabledef.WidthOther, tabledef.WidthOther, tabledef.WidthOther, tabledef.WidthEuros,
+	tabledef.WidthEuros, tabledef.WidthEuros, tabledef.WidthCountry,
+}
+
+// renderTableFragment renders aw as the Bootstrap-styled HTML <table>
+// fragment embedded in the document. The table gets a fixed layout with
+// strictly proportional column widths, so the browser — not this package —
+// decides when a header or cell wraps: on wide screens everything fits on
+// one line, on narrow ones it wraps automatically.
+func (hw *Writer) renderTableFragment(aw *internal.AggregatorWriter) string {
+	t := tabledef.Build(hw.translator, aw)
+	t.Style().HTML = table.HTMLOptions{
+		CSSClass:    htmlCSSClass,
+		EscapeText:  true,
+		Newline:     "<br/>",
+		EmptyColumn: "&nbsp;",
+	}
+	html := t.RenderHTML()
+
+	// go-pretty cannot emit table-level attributes or a <colgroup>, so splice
+	// them into its output: the fixed layout makes the colgroup's relative
+	// widths authoritative instead of content-driven column sizing.
+	openTag := `<table class="` + htmlCSSClass + `">`
+	fixedTag := `<table class="` + htmlCSSClass + `" style="table-layout: fixed">` + "\n" + colgroupHTML()
+	return strings.Replace(html, openTag, fixedTag, 1)
+}
+
+// colgroupHTML returns a <colgroup> with one <col> per rendered column, each
+// sized strictly in proportion to its weight. With the fixed table layout
+// applied in renderTableFragment these widths are authoritative: wide
+// viewports fit headers on a single line, narrow ones wrap automatically.
+func colgroupHTML() string {
+	var total int
+	for _, w := range htmlColumnWeights {
+		total += w
+	}
+	var sb strings.Builder
+	sb.WriteString("<colgroup>")
+	for _, w := range htmlColumnWeights {
+		fmt.Fprintf(&sb, `<col style="width: %.2f%%">`, float64(w)/float64(total)*100)
+	}
+	sb.WriteString("</colgroup>")
+	return sb.String()
+}