Add view tags (#11)

README.md

@@ -94,6 +94,7 @@ View consists of:
 * title
 * component styles - styles are applied to the components by matching first of component tags with style ids
 * additional styling (i.e. line color)
+* tags - if specified, view will contain only components tagged with one of the view tags. When no tag is defined, all components will be included in the rendered view.
 
 In order to instantiate default view, use the view builder:
 ```go
@@ -110,6 +111,7 @@ v := view.NewView().
             WithFontColor(color.Black).
             Build(),
     ).
+    WithTag("TAG").
     Build()
 ```
 
@@ -124,6 +126,8 @@ view:
       background_color: ffffffff
       font_color: 000000ff
       border_color: 000000ff
+  tags:
+    - TAG
 ```
 
 ```go

pkg/view/render.go

@@ -18,12 +18,31 @@ func (v View) render(s model.Structure) string {
 		sb.WriteString(buildSkinParamRectangle(s.id, s.backgroundColor, s.fontColor, s.borderColor))
 	}
 
+	excludedComponentIds := map[string]struct{}{}
 	for _, c := range s.Components {
+		if !v.hasTag(c.Tags...) {
+			excludedComponentIds[c.ID] = struct{}{}
+		}
+	}
+
+	for _, c := range s.Components {
+		_, excluded := excludedComponentIds[c.ID]
+		if excluded {
+			continue
+		}
 		sb.WriteString(buildComponent(c))
 	}
 
 	for src, to := range s.Relations {
 		for trg, _ := range to {
+			_, srcExcluded := excludedComponentIds[src]
+			if srcExcluded {
+				continue
+			}
+			_, trgExcluded := excludedComponentIds[trg]
+			if trgExcluded {
+				continue
+			}
 			sb.WriteString(buildComponentConnection(src, trg, v.lineColor))
 		}
 	}
@@ -38,3 +57,19 @@ func (v View) RenderTo(s model.Structure, w io.Writer) error {
 	_, err := w.Write([]byte(out))
 	return err
 }
+
+func (v View) hasTag(tags ...string) bool {
+	if len(v.tags) == 0 {
+		return true
+	}
+
+	for _, vt := range v.tags {
+		for _, t := range tags {
+			if t == vt {
+				return true
+			}
+		}
+	}
+
+	return false
+}

pkg/view/view.go

@@ -9,17 +9,20 @@ import (
 
 type View struct {
 	title           string
+	tags            []string
 	componentStyles map[string]ComponentStyle
 	lineColor       color.Color
 }
 
 func newView(
 	title string,
+	tags []string,
 	componentStyles map[string]ComponentStyle,
 	lineColor color.Color,
 ) View {
 	return View{
 		title:           title,
+		tags:            tags,
 		componentStyles: componentStyles,
 		lineColor:       lineColor,
 	}
@@ -33,6 +36,7 @@ func NewView() *Builder {
 	return &Builder{
 		View: View{
 			title:           "",
+			tags:            make([]string, 0),
 			componentStyles: make(map[string]ComponentStyle),
 			lineColor:       color.Black,
 		},
@@ -60,6 +64,11 @@ func (b *Builder) WithTitle(t string) *Builder {
 	return b
 }
 
+func (b *Builder) WithTag(t string) *Builder {
+	b.tags = append(b.tags, t)
+	return b
+}
+
 func (b *Builder) WithComponentStyle(s ComponentStyle) *Builder {
 	b.componentStyles[s.id] = s
 	return b
@@ -75,6 +84,7 @@ func (b *Builder) WithLineColor(c color.Color) *Builder {
 func (b Builder) Build() View {
 	return newView(
 		b.title,
+		b.tags,
 		b.componentStyles,
 		b.lineColor,
 	)