/*
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 reconciler

import (
	"context"
	"fmt"
	"strings"

	"github.com/LocoStack/loco-operator/api/v1alpha1"
	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
)

type ComponentReconciler interface {
	// create all resources for the component, and return the list of dependencies
	ReconcileComponent(ctx context.Context, tmpl *v1alpha1.Template, variables map[string]string) ([]client.Object, error)
	ComponentAvailable(ctx context.Context) bool
	ResourceName(name string) string
}

func ResourceLabels(stack, component, name, namespace string) map[string]string {
	labels := map[string]string{
		"app.kubernetes.io/managed-by": "loco-operator",
		"locostack.com/stack":          stack,
		"locostack.com/component":      component,
		"locostack.com/name":           name,
	}
	if namespace != "" {
		labels["locostack.com/namespace"] = namespace
	}
	return labels
}

// substituteVariables replaces placeholders in the input string with actual values from the variables map.
// Placeholders are in the format $(placeholder).
func substituteVariables(variables map[string]string, input string) (bool, string) {
	for placeholder, value := range variables {
		if !strings.Contains(input, "$(") {
			return true, input
		}
		if strings.Contains(input, fmt.Sprintf("$(%s)", placeholder)) {
			input = strings.ReplaceAll(input, fmt.Sprintf("$(%s)", placeholder), value)
		}
	}
	return false, input
}

func mustSubstituteVariables(variables map[string]string, input string) string {
	_, substituted := substituteVariables(variables, input)
	return substituted
}

func buildVolumes(variables map[string]string, tmpl *v1alpha1.Template) []corev1.Volume {
	volumes := make([]corev1.Volume, len(tmpl.Spec.Volumes))
	if len(volumes) == 0 {
		volumes = nil
	} else {
		for i, vol := range tmpl.Spec.Volumes {
			volumes[i] = vol
			if vol.VolumeSource.ConfigMap != nil {
				volumes[i].VolumeSource.ConfigMap.LocalObjectReference.Name = mustSubstituteVariables(variables, vol.VolumeSource.ConfigMap.LocalObjectReference.Name)
			}
			if vol.VolumeSource.Secret != nil {
				volumes[i].VolumeSource.Secret.SecretName = mustSubstituteVariables(variables, vol.VolumeSource.Secret.SecretName)
			}
			if vol.VolumeSource.PersistentVolumeClaim != nil {
				volumes[i].VolumeSource.PersistentVolumeClaim.ClaimName = mustSubstituteVariables(variables, vol.VolumeSource.PersistentVolumeClaim.ClaimName)
			}
		}
	}
	return volumes
}

func buildContainerSpec(variables map[string]string, tmpl *v1alpha1.Template) corev1.Container {
	command := make([]string, len(tmpl.Spec.Runtime.Command))
	if len(command) == 0 {
		command = nil
	} else {
		for i, cmd := range tmpl.Spec.Runtime.Command {
			command[i] = mustSubstituteVariables(variables, cmd)
		}
	}
	args := make([]string, len(tmpl.Spec.Runtime.Args))
	if len(args) == 0 {
		args = nil
	} else {
		for i, arg := range tmpl.Spec.Runtime.Args {
			args[i] = mustSubstituteVariables(variables, arg)
		}
		for _, arg := range tmpl.Spec.Runtime.ExtraArgs {
			args = append(args, mustSubstituteVariables(variables, arg))
		}
		for _, arg := range tmpl.Spec.Runtime.ConditionalArgs {
			complete, substituted := substituteVariables(variables, arg.When)
			if complete && substituted != "" {
				for _, a := range arg.Args {
					args = append(args, mustSubstituteVariables(variables, a))
				}
			}
		}
	}
	env := make([]corev1.EnvVar, len(tmpl.Spec.Runtime.Env))
	if len(env) == 0 {
		env = nil
	} else {
		for i, envVar := range tmpl.Spec.Runtime.Env {
			env[i] = envVar
			env[i].Value = mustSubstituteVariables(variables, envVar.Value)
			if envVar.ValueFrom != nil && envVar.ValueFrom.SecretKeyRef != nil {
				env[i].ValueFrom.SecretKeyRef.LocalObjectReference.Name = mustSubstituteVariables(variables, envVar.ValueFrom.SecretKeyRef.LocalObjectReference.Name)
				env[i].ValueFrom.SecretKeyRef.Key = mustSubstituteVariables(variables, envVar.ValueFrom.SecretKeyRef.Key)
			}
		}
	}
	envFrom := make([]corev1.EnvFromSource, len(tmpl.Spec.Runtime.EnvFrom))
	if len(envFrom) == 0 {
		envFrom = nil
	} else {
		for i, envFromSource := range tmpl.Spec.Runtime.EnvFrom {
			envFrom[i] = envFromSource
			if envFromSource.ConfigMapRef != nil {
				envFrom[i].ConfigMapRef.LocalObjectReference.Name = mustSubstituteVariables(variables, envFromSource.ConfigMapRef.LocalObjectReference.Name)
			}
			if envFromSource.SecretRef != nil {
				envFrom[i].SecretRef.LocalObjectReference.Name = mustSubstituteVariables(variables, envFromSource.SecretRef.LocalObjectReference.Name)
			}
		}
	}
	ports := make([]corev1.ContainerPort, 0)
	if tmpl.Spec.Runtime.Port != 0 {
		ports = append(ports, corev1.ContainerPort{
			ContainerPort: tmpl.Spec.Runtime.Port,
			Protocol:      corev1.ProtocolTCP,
		})
	}
	return corev1.Container{
		Name:            "main",
		Image:           tmpl.Spec.Runtime.Image,
		ImagePullPolicy: corev1.PullIfNotPresent,
		Command:         command,
		Args:            args,
		Env:             env,
		EnvFrom:         envFrom,
		VolumeMounts:    tmpl.Spec.Runtime.VolumeMounts,
		Ports:           ports,
		Resources:       tmpl.Spec.Resources,
	}
}

func buildPodSpec(variables map[string]string, tmpl *v1alpha1.Template) (corev1.PodSpec, error) {
	return corev1.PodSpec{
		NodeSelector:              tmpl.Spec.NodeSelector,
		Affinity:                  tmpl.Spec.Affinity,
		Tolerations:               tmpl.Spec.Tolerations,
		TopologySpreadConstraints: tmpl.Spec.TopologySpreadConstraints,
		Containers:                []corev1.Container{buildContainerSpec(variables, tmpl)},
		SecurityContext:           tmpl.Spec.SecurityContext,
		Volumes:                   buildVolumes(variables, tmpl),
	}, nil
}

type EndpointResolver struct {
	client    client.Client
	scheme    *runtime.Scheme
	namespace string
}

func NewEndpointResolver(client client.Client, scheme *runtime.Scheme, namespace string) *EndpointResolver {
	return &EndpointResolver{
		client:    client,
		scheme:    scheme,
		namespace: namespace,
	}
}

func (r *EndpointResolver) ResolveEndpoint(ctx context.Context, stack *v1alpha1.Stack, ref corev1.ObjectReference) (client.Object, string, error) {
	switch ref.Kind {
	case "ExternalModel":
		return r.resolveExternalModelEndpoint(ctx, stack, ref.Name)
	case "ManagedModel":
		return r.resolveManagedModelEndpoint(ctx, stack, ref.Name)
	case "ExternalTool":
		return r.resolveExternalToolEndpoint(ctx, stack, ref.Name)
	case "ManagedTool":
		return r.resolveManagedToolEndpoint(ctx, stack, ref.Name)
	case "ExternalKnowledgeBase":
		return r.resolveExternalKnowledgeBaseEndpoint(ctx, ref.Name)
	case "ManagedKnowledgeBase":
		return r.resolveManagedKnowledgeBaseEndpoint(ctx, ref.Name)
	case "Component":
		return r.resolveComponentEndpoint(ctx, ref.Name)
	default:
		return nil, "", fmt.Errorf("unsupported reference kind: %s", ref.Kind)
	}
}

func (r *EndpointResolver) resolveGatewayEndpoint(ctx context.Context, stack *v1alpha1.Stack) (*v1alpha1.Component, error) {
	gatewayEnabled := true
	if stack.Spec.Gateway != nil {
		gatewayEnabled = stack.Spec.Gateway.Enabled
	}
	if !gatewayEnabled {
		return nil, nil
	}
	gwList := &v1alpha1.ComponentList{}
	err := r.client.List(ctx, gwList, client.InNamespace(stack.Namespace), client.MatchingLabels{"locostack.com/component": "Gateway", "stack.locostack.com/default": "true"})
	if err != nil {
		return nil, fmt.Errorf("Failed to list gateway components: %v", err)
	}
	if len(gwList.Items) == 0 {
		return nil, fmt.Errorf("No gateway component found for stack %s", stack.Name)
	} else if len(gwList.Items) > 1 {
		return nil, fmt.Errorf("Multiple gateway components found for stack %s", stack.Name)
	}
	gatewayComp := &gwList.Items[0]
	if gatewayComp.Status.Endpoint == "" {
		return nil, fmt.Errorf("Gateway component for stack %s not ready", stack.Name)
	}
	return gatewayComp, nil
}

func (r *EndpointResolver) resolveExternalModelEndpoint(ctx context.Context, stack *v1alpha1.Stack, name string) (client.Object, string, error) {
	var model v1alpha1.ExternalModel
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &model); err != nil {
		return nil, "", fmt.Errorf("Failed to get ExternalModel %s: %w", name, err)
	}
	gatewayComp, err := r.resolveGatewayEndpoint(ctx, stack)
	if err != nil {
		return nil, "", fmt.Errorf("Failed to resolve gateway endpoint for ExternalModel %s: %w", name, err)
	}
	if gatewayComp != nil {
		return &model, gatewayComp.Status.Endpoint, nil
	}
	return &model, model.Spec.APIBase, nil
}

func (r *EndpointResolver) resolveManagedModelEndpoint(ctx context.Context, stack *v1alpha1.Stack, name string) (client.Object, string, error) {
	var model v1alpha1.ManagedModel
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &model); err != nil {
		return nil, "", fmt.Errorf("Failed to get ManagedModel %s: %w", name, err)
	}
	gatewayComp, err := r.resolveGatewayEndpoint(ctx, stack)
	if err != nil {
		return nil, "", fmt.Errorf("Failed to resolve gateway endpoint for ManagedModel %s: %w", name, err)
	}
	if gatewayComp != nil {
		return &model, gatewayComp.Status.Endpoint + "/v1", nil
	}
	return &model, model.Status.Endpoint, nil
}

func (r *EndpointResolver) resolveExternalToolEndpoint(ctx context.Context, stack *v1alpha1.Stack, name string) (client.Object, string, error) {
	var tool v1alpha1.ExternalTool
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &tool); err != nil {
		return nil, "", fmt.Errorf("Failed to get ExternalTool %s: %w", name, err)
	}
	gatewayComp, err := r.resolveGatewayEndpoint(ctx, stack)
	if err != nil {
		return nil, "", fmt.Errorf("Failed to resolve gateway endpoint for ExternalTool %s: %w", name, err)
	}
	if gatewayComp != nil {
		return &tool, gatewayComp.Status.Endpoint + "/mcp", nil
	}
	return &tool, tool.Spec.Endpoint, nil
}

func (r *EndpointResolver) resolveManagedToolEndpoint(ctx context.Context, stack *v1alpha1.Stack, name string) (client.Object, string, error) {
	var tool v1alpha1.ManagedTool
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &tool); err != nil {
		return nil, "", fmt.Errorf("Failed to get ManagedTool %s: %w", name, err)
	}
	gatewayComp, err := r.resolveGatewayEndpoint(ctx, stack)
	if err != nil {
		return nil, "", fmt.Errorf("Failed to resolve gateway endpoint for ManagedTool %s: %w", name, err)
	}
	if gatewayComp != nil {
		return &tool, gatewayComp.Status.Endpoint, nil
	}
	return &tool, tool.Status.Endpoint, nil
}

func (r *EndpointResolver) resolveExternalKnowledgeBaseEndpoint(ctx context.Context, name string) (client.Object, string, error) {
	var kb v1alpha1.ExternalKnowledgeBase
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &kb); err != nil {
		return nil, "", fmt.Errorf("Failed to get ExternalKnowledgeBase %s: %w", name, err)
	}
	// TODO: use gateway endpoint
	return &kb, "", nil
}

func (r *EndpointResolver) resolveManagedKnowledgeBaseEndpoint(ctx context.Context, name string) (client.Object, string, error) {
	var kb v1alpha1.ManagedKnowledgeBase
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, &kb); err != nil {
		return nil, "", fmt.Errorf("Failed to get ManagedKnowledgeBase %s: %w", name, err)
	}
	return &kb, kb.Status.Endpoint, nil
}

func (r *EndpointResolver) resolveComponentEndpoint(ctx context.Context, name string) (client.Object, string, error) {
	comp := &v1alpha1.Component{}
	if err := r.client.Get(ctx, client.ObjectKey{Namespace: r.namespace, Name: name}, comp); err != nil {
		return nil, "", fmt.Errorf("Failed to get Component %s: %w", name, err)
	}
	return comp, comp.Status.Endpoint, nil
}