local-server/cmd/dkl-dir2config/render-context.go

package main

import (
	"bytes"
	"fmt"
	"log"

	yaml "gopkg.in/yaml.v2"

	"novit.nc/direktil/local-server/pkg/clustersconfig"
)

type renderContext struct {
	Host               *clustersconfig.Host
	Group              *clustersconfig.Group
	Cluster            *clustersconfig.Cluster
	Vars               map[string]interface{}
	ConfigTemplate     *clustersconfig.Template
	StaticPodsTemplate *clustersconfig.Template

	clusterConfig *clustersconfig.Config
}

func newRenderContext(host *clustersconfig.Host, cfg *clustersconfig.Config) (ctx *renderContext, err error) {
	cluster := cfg.Cluster(host.Cluster)
	if cluster == nil {
		err = fmt.Errorf("no cluster named %q", host.Cluster)
		return
	}

	group := cfg.Group(host.Group)
	if group == nil {
		err = fmt.Errorf("no group named %q", host.Group)
		return
	}

	vars := make(map[string]interface{})

	for _, oVars := range []map[string]interface{}{
		cluster.Vars,
		group.Vars,
		host.Vars,
	} {
		for k, v := range oVars {
			vars[k] = v
		}
	}

	return &renderContext{
		Host:               host,
		Group:              group,
		Cluster:            cluster,
		Vars:               vars,
		ConfigTemplate:     cfg.ConfigTemplate(group.Config),
		StaticPodsTemplate: cfg.StaticPodsTemplate(group.StaticPods),

		clusterConfig: cfg,
	}, nil
}

func (ctx *renderContext) Config() string {
	if ctx.ConfigTemplate == nil {
		log.Fatalf("no such config: %q", ctx.Group.Config)
	}

	ctxMap := ctx.asMap()

	templateFuncs := ctx.templateFuncs(ctxMap)

	render := func(what string, t *clustersconfig.Template) (s string, err error) {
		buf := &bytes.Buffer{}
		err = t.Execute(buf, ctxMap, templateFuncs)
		if err != nil {
			log.Printf("host %s: failed to render %s [%q]: %v", ctx.Host.Name, what, t.Name, err)
			return
		}

		s = buf.String()
		return
	}

	extraFuncs := ctx.templateFuncs(ctxMap)

	extraFuncs["static_pods"] = func(name string) (string, error) {
		t := ctx.clusterConfig.StaticPodsTemplate(name)
		if t == nil {
			return "", fmt.Errorf("no static pods template named %q", name)
		}

		return render("static pods", t)
	}

	buf := bytes.NewBuffer(make([]byte, 0, 4096))
	if err := ctx.ConfigTemplate.Execute(buf, ctxMap, extraFuncs); err != nil {
		log.Fatalf("failed to render config %q for host %q: %v", ctx.Group.Config, ctx.Host.Name, err)
	}

	return buf.String()
}

func (ctx *renderContext) StaticPods() (ba []byte, err error) {
	if ctx.StaticPodsTemplate == nil {
		log.Fatalf("no such static-pods: %q", ctx.Group.StaticPods)
	}

	ctxMap := ctx.asMap()

	buf := bytes.NewBuffer(make([]byte, 0, 4096))
	if err = ctx.StaticPodsTemplate.Execute(buf, ctxMap, ctx.templateFuncs(ctxMap)); err != nil {
		return
	}

	ba = buf.Bytes()
	return
}

func (ctx *renderContext) templateFuncs(ctxMap map[string]interface{}) map[string]interface{} {
	cluster := ctx.Cluster.Name

	getKeyCert := func(name, funcName string) (s string, err error) {
		req := ctx.clusterConfig.CSR(name)
		if req == nil {
			err = fmt.Errorf("no certificate request named %q", name)
			return
		}

		if req.CA == "" {
			err = fmt.Errorf("CA not defined in req %q", name)
			return
		}

		buf := &bytes.Buffer{}
		err = req.Execute(buf, ctxMap, nil)
		if err != nil {
			return
		}

		key := name
		if req.PerHost {
			key += "/" + ctx.Host.Name
		}

		if funcName == "tls_dir" {
			// needs the dir name
			dir := "/etc/tls/" + name

			s = fmt.Sprintf("{{ %s %q %q %q %q %q %q %q }}", funcName,
				dir, cluster, req.CA, key, req.Profile, req.Label, buf.String())

		} else {
			s = fmt.Sprintf("{{ %s %q %q %q %q %q %q }}", funcName,
				cluster, req.CA, key, req.Profile, req.Label, buf.String())
		}
		return
	}

	return map[string]interface{}{
		"token": func(name string) (s string) {
			return fmt.Sprintf("{{ token %q %q }}", cluster, name)
		},

		"ca_key": func(name string) (s string, err error) {
			// TODO check CA exists
			// ?ctx.clusterConfig.CA(name)
			return fmt.Sprintf("{{ ca_key %q %q }}", cluster, name), nil
		},

		"ca_crt": func(name string) (s string, err error) {
			// TODO check CA exists
			return fmt.Sprintf("{{ ca_crt %q %q }}", cluster, name), nil
		},

		"ca_dir": func(name string) (s string, err error) {
			return fmt.Sprintf("{{ ca_dir %q %q }}", cluster, name), nil
		},

		"tls_key": func(name string) (string, error) {
			return getKeyCert(name, "tls_key")
		},

		"tls_crt": func(name string) (s string, err error) {
			return getKeyCert(name, "tls_crt")
		},

		"tls_dir": func(name string) (s string, err error) {
			return getKeyCert(name, "tls_dir")
		},

		"hosts_of_group": func() (hosts []interface{}) {
			hosts = make([]interface{}, 0)

			for _, host := range ctx.clusterConfig.Hosts {
				if host.Group != ctx.Host.Group {
					continue
				}

				hosts = append(hosts, asMap(host))
			}

			return hosts
		},

		"hosts_of_group_count": func() (count int) {
			for _, host := range ctx.clusterConfig.Hosts {
				if host.Group == ctx.Host.Group {
					count++
				}
			}
			return
		},
	}
}

func (ctx *renderContext) asMap() map[string]interface{} {
	result := asMap(ctx)

	// also expand cluster:
	cluster := result["cluster"].(map[interface{}]interface{})
	cluster["kubernetes_svc_ip"] = ctx.Cluster.KubernetesSvcIP().String()
	cluster["dns_svc_ip"] = ctx.Cluster.DNSSvcIP().String()

	return result
}

func asMap(v interface{}) map[string]interface{} {
	ba, err := yaml.Marshal(v)
	if err != nil {
		panic(err) // shouldn't happen
	}

	result := make(map[string]interface{})

	if err := yaml.Unmarshal(ba, result); err != nil {
		panic(err) // shouldn't happen
	}

	return result
}