package render

import (
	"context"

	"github.com/weaveworks/scope/report"
)

// PropagateSingleMetrics creates a renderer which propagates metrics
// from a node's child to the node. The child is selected based on the
// specified topology. No metrics are propagated when there is more
// than one such child.
func PropagateSingleMetrics(topology string, r Renderer) Renderer {
	return propagateSingleMetrics{topology: topology, r: r}
}

type propagateSingleMetrics struct {
	topology string
	r        Renderer
}

func (p propagateSingleMetrics) Render(ctx context.Context, rpt report.Report) Nodes {
	nodes := p.r.Render(ctx, rpt)
	outputs := make(report.Nodes, len(nodes.Nodes))
	for id, n := range nodes.Nodes {
		var first report.Node
		found := 0
		n.Children.ForEach(func(child report.Node) {
			if child.Topology == p.topology {
				if _, ok := child.Latest.Lookup(report.DoesNotMakeConnections); !ok {
					if found == 0 {
						first = child
					}
					found++
				}
			}
		})
		if found == 1 {
			n = n.WithMetrics(first.Metrics)
		}
		outputs[id] = n
	}
	return Nodes{Nodes: outputs, Filtered: nodes.Filtered}
}