Polish the routing source code

[mathetake]

I added the very naive implementation in #50

ai-gateway/internal/extproc/router/router.go

Lines 30 to 69 in a77bfc2

	// Calculate implements [Router.Calculate].
	func (r *router) Calculate(headers map[string]string) (backendName string, outputSchema extprocconfig.VersionedAPISchema, err error) {
	var rule *extprocconfig.RouteRule
	for i := range r.rules {
	_rule := &r.rules[i]
	for _, hdr := range _rule.Headers {
	v, ok := headers[string(hdr.Name)]
	// Currently, we only do the exact matching.
	if ok && v == hdr.Value {
	rule = _rule
	break
	}
	}
	}
	if rule == nil {
	return "", extprocconfig.VersionedAPISchema{}, errors.New("no matching rule found")
	}
	backendName, outputSchema = r.selectBackendFromRule(rule)
	return
	}
	func (r *router) selectBackendFromRule(rule *extprocconfig.RouteRule) (backendName string, outputSchema extprocconfig.VersionedAPISchema) {
	// Each backend has a weight, so we randomly select depending on the weight.
	// This is a pretty naive implementation and can be buggy, so fix it later.
	totalWeight := 0
	for _, b := range rule.Backends {
	totalWeight += b.Weight
	}
	if totalWeight == 0 {
	return rule.Backends[0].Name, rule.Backends[0].OutputSchema
	}
	selected := r.rng.Intn(totalWeight)
	for _, b := range rule.Backends {
	if selected < b.Weight {
	return b.Name, b.OutputSchema
	}
	selected -= b.Weight
	}
	return rule.Backends[0].Name, rule.Backends[0].OutputSchema
	}

which I think we should refactor before v0.1.0

[theBeginner86]

Hi @mathetake,
May I help in improving this?

[mathetake]

nah i am sorry but i would rather one of maintainers to take care of this, but thanks for the offer anyways