/*
Copyright 2019 The Kruise Authors.

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 metrics

import (
	"context"
	"encoding/json"
	"net/http"

	"k8s.io/klog"
	"k8s.io/utils/pointer"
	"sigs.k8s.io/controller-runtime/pkg/client"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/runtime/inject"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"

	"github.com/oam-dev/kubevela/api/v1alpha1"
	util "github.com/oam-dev/kubevela/pkg/utils"
)

const (
	// SupportedFormat is the only metrics data format we support
	SupportedFormat = "prometheus"

	// SupportedScheme is the only scheme we support
	SupportedScheme = "http"

	// DefaultMetricsPath is the default metrics path we support
	DefaultMetricsPath = "/metrics"
)

// MutatingHandler handles MetricsTrait
type MutatingHandler struct {
	Client client.Client

	// Decoder decodes objects
	Decoder *admission.Decoder
}

// log is for logging in this package.
var mutatelog = logf.Log.WithName("metricstrait-mutate")

var _ admission.Handler = &MutatingHandler{}

// Handle handles admission requests.
func (h *MutatingHandler) Handle(ctx context.Context, req admission.Request) admission.Response {
	obj := &v1alpha1.MetricsTrait{}

	err := h.Decoder.Decode(req, obj)
	if err != nil {
		return admission.Errored(http.StatusBadRequest, err)
	}
	DefaultMetrics(obj)

	marshalled, err := json.Marshal(obj)
	if err != nil {
		return admission.Errored(http.StatusInternalServerError, err)
	}
	resp := admission.PatchResponseFromRaw(req.AdmissionRequest.Object.Raw, marshalled)
	if len(resp.Patches) > 0 {
		klog.V(5).Infof("Admit MetricsTrait %s/%s patches: %v", obj.Namespace, obj.Name, util.DumpJSON(resp.Patches))
	}
	return resp
}

// DefaultMetrics sets all the default value for the metricsTrait
func DefaultMetrics(obj *v1alpha1.MetricsTrait) {
	mutatelog.Info("default", "name", obj.Name)
	if len(obj.Spec.ScrapeService.Format) == 0 {
		mutatelog.Info("default format as prometheus")
		obj.Spec.ScrapeService.Format = SupportedFormat
	}
	if len(obj.Spec.ScrapeService.Path) == 0 {
		mutatelog.Info("default path as /metrics")
		obj.Spec.ScrapeService.Path = DefaultMetricsPath
	}
	if len(obj.Spec.ScrapeService.Scheme) == 0 {
		mutatelog.Info("default scheme as http")
		obj.Spec.ScrapeService.Scheme = SupportedScheme
	}
	if obj.Spec.ScrapeService.Enabled == nil {
		mutatelog.Info("default enabled as true")
		obj.Spec.ScrapeService.Enabled = pointer.BoolPtr(true)
	}
}

var _ inject.Client = &MutatingHandler{}

// InjectClient injects the client into the MutatingHandler
func (h *MutatingHandler) InjectClient(c client.Client) error {
	h.Client = c
	return nil
}

var _ admission.DecoderInjector = &MutatingHandler{}

// InjectDecoder injects the decoder into the MutatingHandler
func (h *MutatingHandler) InjectDecoder(d *admission.Decoder) error {
	h.Decoder = d
	return nil
}