// Copyright 2018 The OPA Authors.  All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.

// Package status implements status reporting.
package status

import (
	"context"
	"fmt"
	"net/http"
	"reflect"

	"github.com/open-policy-agent/opa/metrics"
	"github.com/open-policy-agent/opa/plugins"
	"github.com/open-policy-agent/opa/plugins/bundle"
	"github.com/open-policy-agent/opa/util"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// UpdateRequestV1 represents the status update message that OPA sends to
// remote HTTP endpoints.
type UpdateRequestV1 struct {
	Labels    map[string]string         `json:"labels"`
	Bundle    *bundle.Status            `json:"bundle,omitempty"` // Deprecated: Use bulk `bundles` status updates instead
	Bundles   map[string]*bundle.Status `json:"bundles,omitempty"`
	Discovery *bundle.Status            `json:"discovery,omitempty"`
	Metrics   map[string]interface{}    `json:"metrics,omitempty"`
}

// Plugin implements status reporting. Updates can be triggered by the caller.
type Plugin struct {
	manager            *plugins.Manager
	config             Config
	bundleCh           chan bundle.Status // Deprecated: Use bulk bundle status updates instead
	lastBundleStatus   *bundle.Status     // Deprecated: Use bulk bundle status updates instead
	bulkBundleCh       chan map[string]*bundle.Status
	lastBundleStatuses map[string]*bundle.Status
	discoCh            chan bundle.Status
	lastDiscoStatus    *bundle.Status
	stop               chan chan struct{}
	reconfig           chan interface{}
	metrics            metrics.Metrics
}

// Config contains configuration for the plugin.
type Config struct {
	Service       string `json:"service"`
	PartitionName string `json:"partition_name,omitempty"`
}

func (c *Config) validateAndInjectDefaults(services []string) error {

	if c.Service == "" && len(services) != 0 {
		c.Service = services[0]
	} else {
		found := false

		for _, svc := range services {
			if svc == c.Service {
				found = true
				break
			}
		}

		if !found {
			return fmt.Errorf("invalid service name %q in status", c.Service)
		}
	}

	return nil
}

// ParseConfig validates the config and injects default values.
func ParseConfig(config []byte, services []string) (*Config, error) {

	if config == nil {
		return nil, nil
	}

	var parsedConfig Config

	if err := util.Unmarshal(config, &parsedConfig); err != nil {
		return nil, err
	}

	if err := parsedConfig.validateAndInjectDefaults(services); err != nil {
		return nil, err
	}

	return &parsedConfig, nil
}

// New returns a new Plugin with the given config.
func New(parsedConfig *Config, manager *plugins.Manager) *Plugin {
	return &Plugin{
		manager:      manager,
		config:       *parsedConfig,
		bundleCh:     make(chan bundle.Status),
		bulkBundleCh: make(chan map[string]*bundle.Status),
		discoCh:      make(chan bundle.Status),
		stop:         make(chan chan struct{}),
		reconfig:     make(chan interface{}),
	}
}

// WithMetrics sets the global metrics provider to be used by the plugin.
func (p *Plugin) WithMetrics(m metrics.Metrics) *Plugin {
	p.metrics = m
	return p
}

// Name identifies the plugin on manager.
const Name = "status"

// Lookup returns the status plugin registered with the manager.
func Lookup(manager *plugins.Manager) *Plugin {
	if p := manager.Plugin(Name); p != nil {
		return p.(*Plugin)
	}
	return nil
}

// Start starts the plugin.
func (p *Plugin) Start(ctx context.Context) error {
	p.logInfo("Starting status reporter.")
	go p.loop()
	return nil
}

// Stop stops the plugin.
func (p *Plugin) Stop(ctx context.Context) {
	p.logInfo("Stopping status reporter.")
	done := make(chan struct{})
	p.stop <- done
	_ = <-done
}

// UpdateBundleStatus notifies the plugin that the policy bundle was updated.
// Deprecated: Use BulkUpdateBundleStatus instead.
func (p *Plugin) UpdateBundleStatus(status bundle.Status) {
	p.bundleCh <- status
}

// BulkUpdateBundleStatus notifies the plugin that the policy bundle was updated.
func (p *Plugin) BulkUpdateBundleStatus(status map[string]*bundle.Status) {
	p.bulkBundleCh <- status
}

// UpdateDiscoveryStatus notifies the plugin that the discovery bundle was updated.
func (p *Plugin) UpdateDiscoveryStatus(status bundle.Status) {
	p.discoCh <- status
}

// Reconfigure notifies the plugin with a new configuration.
func (p *Plugin) Reconfigure(_ context.Context, config interface{}) {
	p.reconfig <- config
}

func (p *Plugin) loop() {

	ctx, cancel := context.WithCancel(context.Background())

	for {
		select {
		case statuses := <-p.bulkBundleCh:
			p.lastBundleStatuses = statuses
			err := p.oneShot(ctx)
			if err != nil {
				p.logError("%v.", err)
			} else {
				p.logInfo("Status update sent successfully in response to bundle update.")
			}
		case status := <-p.bundleCh:
			p.lastBundleStatus = &status
			err := p.oneShot(ctx)
			if err != nil {
				p.logError("%v.", err)
			} else {
				p.logInfo("Status update sent successfully in response to bundle update.")
			}
		case status := <-p.discoCh:
			p.lastDiscoStatus = &status
			err := p.oneShot(ctx)
			if err != nil {
				p.logError("%v.", err)
			} else {
				p.logInfo("Status update sent successfully in response to discovery update.")
			}

		case newConfig := <-p.reconfig:
			p.reconfigure(newConfig)

		case done := <-p.stop:
			cancel()
			done <- struct{}{}
			return
		}
	}
}

func (p *Plugin) oneShot(ctx context.Context) error {

	req := &UpdateRequestV1{
		Labels:    p.manager.Labels(),
		Discovery: p.lastDiscoStatus,
		Bundle:    p.lastBundleStatus,
		Bundles:   p.lastBundleStatuses,
	}

	if p.metrics != nil {
		req.Metrics = map[string]interface{}{p.metrics.Info().Name: p.metrics.All()}
	}

	resp, err := p.manager.Client(p.config.Service).
		WithJSON(req).
		Do(ctx, "POST", fmt.Sprintf("/status/%v", p.config.PartitionName))

	if err != nil {
		return errors.Wrap(err, "Status update failed")
	}

	defer util.Close(resp)

	switch resp.StatusCode {
	case http.StatusOK:
		return nil
	case http.StatusNotFound:
		return fmt.Errorf("Status update failed, server replied with not found")
	case http.StatusUnauthorized:
		return fmt.Errorf("Status update failed, server replied with not authorized")
	default:
		return fmt.Errorf("Status update failed, server replied with HTTP %v", resp.StatusCode)
	}
}

func (p *Plugin) reconfigure(config interface{}) {
	newConfig := config.(*Config)

	if reflect.DeepEqual(p.config, *newConfig) {
		p.logDebug("Status reporter configuration unchanged.")
		return
	}

	p.logInfo("Status reporter configuration changed.")
	p.config = *newConfig
}

func (p *Plugin) logError(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Errorf(fmt, a...)
}

func (p *Plugin) logInfo(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Infof(fmt, a...)
}

func (p *Plugin) logDebug(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Debugf(fmt, a...)
}

func (p *Plugin) logrusFields() logrus.Fields {
	return logrus.Fields{
		"plugin": Name,
	}
}