package consul

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/kvtools/consul"
	"github.com/traefik/traefik/v2/pkg/provider"
	"github.com/traefik/traefik/v2/pkg/provider/kv"
	"github.com/traefik/traefik/v2/pkg/types"
)

// providerName is the Consul provider name.
const providerName = "consul"

var _ provider.Provider = (*Provider)(nil)

// ProviderBuilder is responsible for constructing namespaced instances of the Consul provider.
type ProviderBuilder struct {
	kv.Provider `yaml:",inline" export:"true"`

	Token string           `description:"Per-request ACL token." json:"token,omitempty" toml:"token,omitempty" yaml:"token,omitempty" loggable:"false"`
	TLS   *types.ClientTLS `description:"Enable TLS support." json:"tls,omitempty" toml:"tls,omitempty" yaml:"tls,omitempty" export:"true"`

	Namespaces []string `description:"Sets the namespaces used to discover the configuration (Consul Enterprise only)." json:"namespaces,omitempty" toml:"namespaces,omitempty" yaml:"namespaces,omitempty"`
}

// SetDefaults sets the default values.
func (p *ProviderBuilder) SetDefaults() {
	p.Provider.SetDefaults()
	p.Endpoints = []string{"127.0.0.1:8500"}
}

// BuildProviders builds Consul provider instances for the given namespaces configuration.
func (p *ProviderBuilder) BuildProviders() []*Provider {
	if len(p.Namespaces) == 0 {
		return []*Provider{{
			Provider: p.Provider,
			name:     providerName,
			token:    p.Token,
			tls:      p.TLS,
		}}
	}

	var providers []*Provider
	for _, namespace := range p.Namespaces {
		providers = append(providers, &Provider{
			Provider:  p.Provider,
			name:      providerName + "-" + namespace,
			namespace: namespace,
			token:     p.Token,
			tls:       p.TLS,
		})
	}

	return providers
}

// Provider holds configurations of the provider.
type Provider struct {
	kv.Provider

	name      string
	namespace string
	token     string
	tls       *types.ClientTLS
}

// Init the provider.
func (p *Provider) Init() error {
	// Wildcard namespace allows fetching KV values from any namespace for recursive requests (see https://www.consul.io/api/kv#ns).
	// As we are not supporting multiple namespaces at the same time, wildcard namespace is not allowed.
	if p.namespace == "*" {
		return errors.New("wildcard namespace is not supported")
	}

	// In case they didn't initialize with BuildProviders.
	if p.name == "" {
		p.name = providerName
	}

	config := &consul.Config{
		ConnectionTimeout: 3 * time.Second,
		Token:             p.token,
		Namespace:         p.namespace,
	}

	if p.tls != nil {
		var err error
		config.TLS, err = p.tls.CreateTLSConfig(context.Background())
		if err != nil {
			return fmt.Errorf("unable to create client TLS configuration: %w", err)
		}
	}

	return p.Provider.Init(consul.StoreName, p.name, config)
}