// Copyright (c) 2022 Alibaba Group Holding Ltd.
//
// 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 config

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"

	"github.com/alibaba/higress/pkg/cmd/hgctl/kubernetes"
	"github.com/alibaba/higress/pkg/cmd/options"
	"k8s.io/apimachinery/pkg/types"
	"sigs.k8s.io/yaml"
)

var (
	BootstrapEnvoyConfigType EnvoyConfigType = "bootstrap"
	ClusterEnvoyConfigType   EnvoyConfigType = "cluster"
	EndpointEnvoyConfigType  EnvoyConfigType = "endpoint"
	ListenerEnvoyConfigType  EnvoyConfigType = "listener"
	RouteEnvoyConfigType     EnvoyConfigType = "route"
	AllEnvoyConfigType       EnvoyConfigType = "all"
)

const (
	defaultProxyAdminPort = 15000
)

type EnvoyConfigType string

type GetEnvoyConfigOptions struct {
	IncludeEds      bool
	PodName         string
	PodNamespace    string
	BindAddress     string
	Output          string
	EnvoyConfigType EnvoyConfigType
}

func NewDefaultGetEnvoyConfigOptions() *GetEnvoyConfigOptions {
	return &GetEnvoyConfigOptions{
		IncludeEds:      true,
		PodName:         "",
		PodNamespace:    "higress-system",
		BindAddress:     "localhost",
		Output:          "json",
		EnvoyConfigType: AllEnvoyConfigType,
	}
}

func GetEnvoyConfig(config *GetEnvoyConfigOptions) ([]byte, error) {
	configDump, err := retrieveConfigDump(config.PodName, config.PodNamespace, config.BindAddress, config.IncludeEds)
	if err != nil {
		return nil, err
	}
	if config.EnvoyConfigType == AllEnvoyConfigType {
		return configDump, nil
	}
	resource, err := getXDSResource(config.EnvoyConfigType, configDump)
	if err != nil {
		return nil, err
	}
	return formatGatewayConfig(resource, config.Output)
}

func retrieveConfigDump(podName, podNamespace, bindAddress string, includeEds bool) ([]byte, error) {
	if podNamespace == "" {
		return nil, fmt.Errorf("pod namespace is required")
	}

	if podName == "" {
		c, err := kubernetes.NewCLIClient(options.DefaultConfigFlags.ToRawKubeConfigLoader())
		if err != nil {
			return nil, fmt.Errorf("failed to build kubernetes client: %w", err)
		}
		podList, err := c.PodsForSelector(podNamespace, "app=higress-gateway")
		if err != nil {
			return nil, err
		}
		if len(podList.Items) == 0 {
			return nil, fmt.Errorf("higress gateway pod is not existed in namespace %s", podNamespace)
		}

		podName = podList.Items[0].GetName()
	}

	fw, err := portForwarder(types.NamespacedName{
		Namespace: podNamespace,
		Name:      podName,
	}, bindAddress)
	if err != nil {
		return nil, err
	}
	if err := fw.Start(); err != nil {
		return nil, err
	}
	defer fw.Stop()

	configDump, err := fetchGatewayConfig(fw, includeEds)
	if err != nil {
		return nil, err
	}

	return configDump, nil
}

func portForwarder(nn types.NamespacedName, bindAddress string) (kubernetes.PortForwarder, error) {
	c, err := kubernetes.NewCLIClient(options.DefaultConfigFlags.ToRawKubeConfigLoader())
	if err != nil {
		return nil, fmt.Errorf("build CLI client fail: %w", err)
	}

	pod, err := c.Pod(nn)
	if err != nil {
		return nil, fmt.Errorf("get pod %s fail: %w", nn, err)
	}
	if pod.Status.Phase != "Running" {
		return nil, fmt.Errorf("pod %s is not running", nn)
	}

	fw, err := kubernetes.NewLocalPortForwarder(c, nn, 0, defaultProxyAdminPort, bindAddress)
	if err != nil {
		return nil, err
	}

	return fw, nil
}

func formatGatewayConfig(configDump any, output string) ([]byte, error) {
	out, err := json.MarshalIndent(configDump, "", "  ")
	if err != nil {
		return nil, err
	}

	if output == "yaml" {
		out, err = yaml.JSONToYAML(out)
		if err != nil {
			return nil, err
		}
	}

	return out, nil
}

func fetchGatewayConfig(fw kubernetes.PortForwarder, includeEds bool) ([]byte, error) {
	out, err := configDumpRequest(fw.Address(), includeEds)
	if err != nil {
		return nil, err
	}

	return out, nil
}

func configDumpRequest(address string, includeEds bool) ([]byte, error) {
	url := fmt.Sprintf("http://%s/config_dump", address)
	if includeEds {
		url = fmt.Sprintf("%s?include_eds", url)
	}
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, err
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer func() {
		_ = resp.Body.Close()
	}()

	return io.ReadAll(resp.Body)
}

func getXDSResource(resourceType EnvoyConfigType, configDump []byte) (any, error) {
	cd := map[string]any{}
	if err := json.Unmarshal(configDump, &cd); err != nil {
		return nil, err
	}
	if resourceType == AllEnvoyConfigType {
		return cd, nil
	}
	configs := cd["configs"]
	globalConfigs := configs.([]any)

	switch resourceType {
	case BootstrapEnvoyConfigType:
		for _, config := range globalConfigs {
			if config.(map[string]interface{})["@type"] == "type.googleapis.com/envoy.admin.v3.BootstrapConfigDump" {
				return config, nil
			}
		}
	case EndpointEnvoyConfigType:
		for _, config := range globalConfigs {
			if config.(map[string]interface{})["@type"] == "type.googleapis.com/envoy.admin.v3.EndpointsConfigDump" {
				return config, nil
			}
		}

	case ClusterEnvoyConfigType:
		for _, config := range globalConfigs {
			if config.(map[string]interface{})["@type"] == "type.googleapis.com/envoy.admin.v3.ClustersConfigDump" {
				return config, nil
			}
		}
	case ListenerEnvoyConfigType:
		for _, config := range globalConfigs {
			if config.(map[string]interface{})["@type"] == "type.googleapis.com/envoy.admin.v3.ListenersConfigDump" {
				return config, nil
			}
		}
	case RouteEnvoyConfigType:
		for _, config := range globalConfigs {
			if config.(map[string]interface{})["@type"] == "type.googleapis.com/envoy.admin.v3.RoutesConfigDump" {
				return config, nil
			}
		}
	default:
		return nil, fmt.Errorf("unknown resourceType %s", resourceType)
	}

	return nil, fmt.Errorf("unknown resourceType %s", resourceType)
}