// Package nifcloud implements a DNS provider for solving the DNS-01 challenge using NIFCLOUD DNS.
package nifcloud

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"time"

	"github.com/cenkalti/backoff/v5"
	"github.com/go-acme/lego/v4/challenge"
	"github.com/go-acme/lego/v4/challenge/dns01"
	"github.com/go-acme/lego/v4/platform/config/env"
	"github.com/go-acme/lego/v4/platform/wait"
	"github.com/go-acme/lego/v4/providers/dns/internal/clientdebug"
	"github.com/go-acme/lego/v4/providers/dns/nifcloud/internal"
)

// Environment variables names.
const (
	envNamespace = "NIFCLOUD_"

	EnvAccessKeyID     = envNamespace + "ACCESS_KEY_ID"
	EnvSecretAccessKey = envNamespace + "SECRET_ACCESS_KEY"
	EnvDNSEndpoint     = envNamespace + "DNS_ENDPOINT"

	EnvTTL                = envNamespace + "TTL"
	EnvPropagationTimeout = envNamespace + "PROPAGATION_TIMEOUT"
	EnvPollingInterval    = envNamespace + "POLLING_INTERVAL"
	EnvHTTPTimeout        = envNamespace + "HTTP_TIMEOUT"
)

var _ challenge.ProviderTimeout = (*DNSProvider)(nil)

// Config is used to configure the creation of the DNSProvider.
type Config struct {
	BaseURL            string
	AccessKey          string
	SecretKey          string
	PropagationTimeout time.Duration
	PollingInterval    time.Duration
	TTL                int
	HTTPClient         *http.Client
}

// NewDefaultConfig returns a default configuration for the DNSProvider.
func NewDefaultConfig() *Config {
	return &Config{
		TTL:                env.GetOrDefaultInt(EnvTTL, dns01.DefaultTTL),
		PropagationTimeout: env.GetOrDefaultSecond(EnvPropagationTimeout, dns01.DefaultPropagationTimeout),
		PollingInterval:    env.GetOrDefaultSecond(EnvPollingInterval, dns01.DefaultPollingInterval),
		HTTPClient: &http.Client{
			Timeout: env.GetOrDefaultSecond(EnvHTTPTimeout, 30*time.Second),
		},
	}
}

// DNSProvider implements the challenge.Provider interface.
type DNSProvider struct {
	client *internal.Client
	config *Config
}

// NewDNSProvider returns a DNSProvider instance configured for the NIFCLOUD DNS service.
// Credentials must be passed in the environment variables:
// NIFCLOUD_ACCESS_KEY_ID and NIFCLOUD_SECRET_ACCESS_KEY.
func NewDNSProvider() (*DNSProvider, error) {
	values, err := env.Get(EnvAccessKeyID, EnvSecretAccessKey)
	if err != nil {
		return nil, fmt.Errorf("nifcloud: %w", err)
	}

	config := NewDefaultConfig()
	config.BaseURL = env.GetOrFile(EnvDNSEndpoint)
	config.AccessKey = values[EnvAccessKeyID]
	config.SecretKey = values[EnvSecretAccessKey]

	return NewDNSProviderConfig(config)
}

// NewDNSProviderConfig return a DNSProvider instance configured for NIFCLOUD.
func NewDNSProviderConfig(config *Config) (*DNSProvider, error) {
	if config == nil {
		return nil, errors.New("nifcloud: the configuration of the DNS provider is nil")
	}

	client, err := internal.NewClient(config.AccessKey, config.SecretKey)
	if err != nil {
		return nil, fmt.Errorf("nifcloud: %w", err)
	}

	if config.HTTPClient != nil {
		client.HTTPClient = config.HTTPClient
	}

	client.HTTPClient = clientdebug.Wrap(client.HTTPClient)

	if config.BaseURL != "" {
		baseURL, err := url.Parse(config.BaseURL)
		if err != nil {
			return nil, fmt.Errorf("nifcloud: %w", err)
		}

		client.BaseURL = baseURL
	}

	return &DNSProvider{client: client, config: config}, nil
}

// Present creates a TXT record using the specified parameters.
func (d *DNSProvider) Present(domain, token, keyAuth string) error {
	ctx := context.Background()

	info := dns01.GetChallengeInfo(domain, keyAuth)

	err := d.changeRecord(ctx, "CREATE", info.EffectiveFQDN, info.Value, d.config.TTL)
	if err != nil {
		return fmt.Errorf("nifcloud: %w", err)
	}

	return err
}

// CleanUp removes the TXT record matching the specified parameters.
func (d *DNSProvider) CleanUp(domain, token, keyAuth string) error {
	ctx := context.Background()

	info := dns01.GetChallengeInfo(domain, keyAuth)

	err := d.changeRecord(ctx, "DELETE", info.EffectiveFQDN, info.Value, d.config.TTL)
	if err != nil {
		return fmt.Errorf("nifcloud: %w", err)
	}

	return err
}

// Timeout returns the timeout and interval to use when checking for DNS propagation.
// Adjusting here to cope with spikes in propagation times.
func (d *DNSProvider) Timeout() (timeout, interval time.Duration) {
	return d.config.PropagationTimeout, d.config.PollingInterval
}

func (d *DNSProvider) changeRecord(ctx context.Context, action, fqdn, value string, ttl int) error {
	authZone, err := dns01.FindZoneByFqdn(fqdn)
	if err != nil {
		return fmt.Errorf("could not find zone: %w", err)
	}

	name := dns01.UnFqdn(fqdn)
	if authZone == fqdn {
		name = "@"
	}

	reqParams := internal.ChangeResourceRecordSetsRequest{
		XMLNs: internal.XMLNs,
		ChangeBatch: internal.ChangeBatch{
			Comment: "Managed by Lego",
			Changes: internal.Changes{
				Change: []internal.Change{
					{
						Action: action,
						ResourceRecordSet: internal.ResourceRecordSet{
							Name: name,
							Type: "TXT",
							TTL:  ttl,
							ResourceRecords: internal.ResourceRecords{
								ResourceRecord: []internal.ResourceRecord{
									{
										Value: value,
									},
								},
							},
						},
					},
				},
			},
		},
	}

	resp, err := d.client.ChangeResourceRecordSets(ctx, dns01.UnFqdn(authZone), reqParams)
	if err != nil {
		return fmt.Errorf("failed to change record set: %w", err)
	}

	statusID := resp.ChangeInfo.ID

	return wait.Retry(ctx,
		func() error {
			resp, err := d.client.GetChange(ctx, statusID)
			if err != nil {
				return fmt.Errorf("get change: %w", err)
			}

			if resp.ChangeInfo.Status != "INSYNC" {
				return fmt.Errorf("change status: %s", resp.ChangeInfo.Status)
			}

			return nil
		},
		backoff.WithBackOff(backoff.NewConstantBackOff(4*time.Second)),
		backoff.WithMaxElapsedTime(120*time.Second),
	)
}
