loco-operator/pkg/templates/templates.go

/*
Copyright 2026 LocoStack.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package templates

import (
	"fmt"
	"maps"
	"slices"

	"github.com/LocoStack/loco-operator/api/v1alpha1"
	corev1 "k8s.io/api/core/v1"
)

type TemplateManager struct {
	templates map[string]v1alpha1.Template
	runtimes  map[string]v1alpha1.RuntimeSpec
}

func NewTemplateManager() *TemplateManager {
	return &TemplateManager{
		templates: make(map[string]v1alpha1.Template),
		runtimes:  make(map[string]v1alpha1.RuntimeSpec),
	}
}

func (m *TemplateManager) GetTemplate(name string) (v1alpha1.Template, bool) {
	tmpl, ok := m.templates[name]
	return tmpl, ok
}

func (m *TemplateManager) GetRuntime(name string) (v1alpha1.RuntimeSpec, bool) {
	rt, ok := m.runtimes[name]
	return rt, ok
}

func (m *TemplateManager) RegisterTemplate(tmpl v1alpha1.Template) {
	m.templates[tmpl.Name] = tmpl
}

func (m *TemplateManager) RegisterRuntime(rt v1alpha1.RuntimeSpec) {
	m.runtimes[rt.Name] = rt
}

func (m *TemplateManager) ResolveTemplate(tmpl *v1alpha1.Template, defaultKey string) (v1alpha1.Template, error) {
	var templateName string
	if tmpl == nil {
		templateName = defaultKey
	} else {
		templateName = tmpl.Name
		if templateName == "" {
			templateName = defaultKey
		}
	}
	base, ok := m.GetTemplate(templateName)
	if !ok {
		return v1alpha1.Template{}, fmt.Errorf("template %q not found", templateName)
	}
	// resolve runtime if specified in the template or inherited from the base
	if tmpl != nil && tmpl.Spec.Runtime.Name != "" && tmpl.Spec.Runtime.Name != base.Spec.Runtime.Name {
		rtBase, ok := m.GetRuntime(tmpl.Spec.Runtime.Name)
		if !ok {
			return v1alpha1.Template{}, fmt.Errorf("runtime %q not found", tmpl.Spec.Runtime.Name)
		}
		mergeRuntimeSpec(&rtBase, &tmpl.Spec.Runtime)
		tmpl.Spec.Runtime = rtBase
	}
	return mergeTemplates(base, tmpl), nil
}

func mergeTemplates(base v1alpha1.Template, override *v1alpha1.Template) v1alpha1.Template {
	merged := base.DeepCopy()
	if override == nil {
		return *merged
	}
	if override.Name != "" && base.Name != override.Name {
		return *override.DeepCopy()
	}
	mergeStringMap(&merged.Metadata.Labels, override.Metadata.Labels)
	mergeStringMap(&merged.Metadata.Annotations, override.Metadata.Annotations)
	mergeTemplateSpec(&merged.Spec, &override.Spec)
	return *merged
}

func mergeTemplateSpec(dst, src *v1alpha1.TemplateSpec) {
	mergeRuntimeSpec(&dst.Runtime, &src.Runtime)

	if src.Volumes != nil {
		dst.Volumes = deepCopyVolumes(src.Volumes)
	}

	mergeResourceRequirements(&dst.Resources, &src.Resources)
	mergeStringMap(&dst.NodeSelector, src.NodeSelector)

	if src.Affinity != nil {
		dst.Affinity = src.Affinity.DeepCopy()
	}

	if src.Tolerations != nil {
		dst.Tolerations = deepCopyTolerations(src.Tolerations)
	}

	if src.TopologySpreadConstraints != nil {
		dst.TopologySpreadConstraints = deepCopyTopologySpreadConstraints(src.TopologySpreadConstraints)
	}

	if src.SecurityContext != nil {
		dst.SecurityContext = src.SecurityContext.DeepCopy()
	}
}

func mergeRuntimeSpec(dst, src *v1alpha1.RuntimeSpec) {
	if src.Name != "" && dst.Name != "" && src.Name != dst.Name {
		*dst = *src.DeepCopy()
		return
	}

	if src.Name != "" {
		dst.Name = src.Name
	}
	if src.Image != "" {
		dst.Image = src.Image
	}
	if src.Command != nil {
		dst.Command = slices.Clone(src.Command)
	}
	if src.Args != nil {
		dst.Args = slices.Clone(src.Args)
	}
	if src.ExtraArgs != nil {
		dst.ExtraArgs = slices.Clone(src.ExtraArgs)
	}
	if src.Env != nil {
		mergeEnvVars(&dst.Env, src.Env)
	}
	if src.VolumeMounts != nil {
		dst.VolumeMounts = deepCopyVolumeMounts(src.VolumeMounts)
	}
	if src.Port != 0 {
		dst.Port = src.Port
	}
}

func mergeResourceRequirements(dst, src *corev1.ResourceRequirements) {
	if src.Limits != nil {
		if dst.Limits == nil {
			dst.Limits = make(corev1.ResourceList)
		}
		maps.Copy(dst.Limits, src.Limits)
	}
	if src.Requests != nil {
		if dst.Requests == nil {
			dst.Requests = make(corev1.ResourceList)
		}
		maps.Copy(dst.Requests, src.Requests)
	}
	if src.Claims != nil {
		dst.Claims = slices.Clone(src.Claims)
	}
}

func mergeStringMap(dst *map[string]string, src map[string]string) {
	if src == nil {
		return
	}
	if *dst == nil {
		*dst = make(map[string]string)
	}
	maps.Copy(*dst, src)
}

func mergeEnvVars(dst *[]corev1.EnvVar, src []corev1.EnvVar) {
	if src == nil {
		return
	}
	if *dst == nil {
		*dst = make([]corev1.EnvVar, 0, len(src))
	}
	existing := make(map[string]int)
	for i, env := range *dst {
		existing[env.Name] = i
	}
	for _, env := range src {
		if idx, ok := existing[env.Name]; ok {
			env.DeepCopyInto(&(*dst)[idx])
		} else {
			*dst = append(*dst, *env.DeepCopy())
		}
	}
}

func deepCopyVolumeMounts(in []corev1.VolumeMount) []corev1.VolumeMount {
	out := make([]corev1.VolumeMount, len(in))
	for i := range in {
		in[i].DeepCopyInto(&out[i])
	}
	return out
}

func deepCopyVolumes(in []corev1.Volume) []corev1.Volume {
	out := make([]corev1.Volume, len(in))
	for i := range in {
		in[i].DeepCopyInto(&out[i])
	}
	return out
}

func deepCopyTolerations(in []corev1.Toleration) []corev1.Toleration {
	out := make([]corev1.Toleration, len(in))
	for i := range in {
		in[i].DeepCopyInto(&out[i])
	}
	return out
}

func deepCopyTopologySpreadConstraints(in []corev1.TopologySpreadConstraint) []corev1.TopologySpreadConstraint {
	out := make([]corev1.TopologySpreadConstraint, len(in))
	for i := range in {
		in[i].DeepCopyInto(&out[i])
	}
	return out
}

var Manager = NewTemplateManager()