// Package alwaysdata implements a DNS provider for solving the DNS-01 challenge using Alwaysdata.
package alwaysdata

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

	"github.com/go-acme/lego/v4/challenge/dns01"
	"github.com/go-acme/lego/v4/platform/config/env"
	"github.com/go-acme/lego/v4/providers/dns/alwaysdata/internal"
	"github.com/go-acme/lego/v4/providers/dns/internal/clientdebug"
)

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

	EnvAPIKey  = envNamespace + "API_KEY"
	EnvAccount = envNamespace + "ACCOUNT"

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

// Config is used to configure the creation of the DNSProvider.
type Config struct {
	APIKey  string
	Account 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 {
	config *Config
	client *internal.Client
}

// NewDNSProvider returns a DNSProvider instance configured for Alwaysdata.
func NewDNSProvider() (*DNSProvider, error) {
	values, err := env.Get(EnvAPIKey)
	if err != nil {
		return nil, fmt.Errorf("alwaysdata: %w", err)
	}

	config := NewDefaultConfig()
	config.APIKey = values[EnvAPIKey]
	config.Account = env.GetOrFile(EnvAccount)

	return NewDNSProviderConfig(config)
}

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

	client, err := internal.NewClient(config.APIKey, config.Account)
	if err != nil {
		return nil, fmt.Errorf("alwaysdata: %w", err)
	}

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

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

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

	zone, err := d.findZone(ctx, info.EffectiveFQDN)
	if err != nil {
		return fmt.Errorf("alwaysdata: %w", err)
	}

	subDomain, err := dns01.ExtractSubDomain(info.EffectiveFQDN, zone.Name)
	if err != nil {
		return fmt.Errorf("alwaysdata: %w", err)
	}

	record := internal.RecordRequest{
		DomainID:   zone.ID,
		Name:       subDomain,
		Type:       "TXT",
		Value:      info.Value,
		TTL:        d.config.TTL,
		Annotation: "lego",
	}

	err = d.client.AddRecord(ctx, record)
	if err != nil {
		return fmt.Errorf("alwaysdata: add TXT record: %w", err)
	}

	return nil
}

// 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)

	zone, err := d.findZone(ctx, info.EffectiveFQDN)
	if err != nil {
		return fmt.Errorf("alwaysdata: %w", err)
	}

	subDomain, err := dns01.ExtractSubDomain(info.EffectiveFQDN, zone.Name)
	if err != nil {
		return fmt.Errorf("alwaysdata: %w", err)
	}

	records, err := d.client.ListRecords(ctx, zone.ID, subDomain)
	if err != nil {
		return fmt.Errorf("alwaysdata: list records: %w", err)
	}

	for _, record := range records {
		if record.Type != "TXT" || record.Value != info.Value {
			continue
		}

		err = d.client.DeleteRecord(ctx, record.ID)
		if err != nil {
			return fmt.Errorf("alwaysdata: delete TXT record: %w", err)
		}
	}

	return nil
}

// 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) findZone(ctx context.Context, fqdn string) (*internal.Domain, error) {
	domains, err := d.client.ListDomains(ctx)
	if err != nil {
		return nil, fmt.Errorf("list domains: %w", err)
	}

	for a := range dns01.UnFqdnDomainsSeq(fqdn) {
		for _, domain := range domains {
			if a == domain.Name {
				return &domain, nil
			}
		}
	}

	return nil, errors.New("domain not found")
}