// Package gandi implements a DNS provider for solving the DNS-01 challenge using Gandi DNS.
package gandi

import (
	"errors"
	"fmt"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/go-acme/lego/v4/challenge/dns01"
	"github.com/go-acme/lego/v4/platform/config/env"
)

// Gandi API reference:       http://doc.rpc.gandi.net/index.html
// Gandi API domain examples: http://doc.rpc.gandi.net/domain/faq.html

const (
	// defaultBaseURL Gandi XML-RPC endpoint used by Present and CleanUp.
	defaultBaseURL = "https://rpc.gandi.net/xmlrpc/"
	minTTL         = 300
)

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

	EnvAPIKey = envNamespace + "API_KEY"

	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 {
	BaseURL            string
	APIKey             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, minTTL),
		PropagationTimeout: env.GetOrDefaultSecond(EnvPropagationTimeout, 40*time.Minute),
		PollingInterval:    env.GetOrDefaultSecond(EnvPollingInterval, 60*time.Second),
		HTTPClient: &http.Client{
			Timeout: env.GetOrDefaultSecond(EnvHTTPTimeout, 60*time.Second),
		},
	}
}

// inProgressInfo contains information about an in-progress challenge.
type inProgressInfo struct {
	zoneID    int    // zoneID of gandi zone to restore in CleanUp
	newZoneID int    // zoneID of temporary gandi zone containing TXT record
	authZone  string // the domain name registered at gandi with trailing "."
}

// DNSProvider implements the challenge.Provider interface.
type DNSProvider struct {
	inProgressFQDNs     map[string]inProgressInfo
	inProgressAuthZones map[string]struct{}
	inProgressMu        sync.Mutex
	config              *Config
	// findZoneByFqdn determines the DNS zone of an fqdn. It is overridden during tests.
	findZoneByFqdn func(fqdn string) (string, error)
}

// NewDNSProvider returns a DNSProvider instance configured for Gandi.
// Credentials must be passed in the environment variable: GANDI_API_KEY.
func NewDNSProvider() (*DNSProvider, error) {
	values, err := env.Get(EnvAPIKey)
	if err != nil {
		return nil, fmt.Errorf("gandi: %w", err)
	}

	config := NewDefaultConfig()
	config.APIKey = values[EnvAPIKey]

	return NewDNSProviderConfig(config)
}

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

	if config.APIKey == "" {
		return nil, errors.New("gandi: no API Key given")
	}

	if config.BaseURL == "" {
		config.BaseURL = defaultBaseURL
	}

	return &DNSProvider{
		config:              config,
		inProgressFQDNs:     make(map[string]inProgressInfo),
		inProgressAuthZones: make(map[string]struct{}),
		findZoneByFqdn:      dns01.FindZoneByFqdn,
	}, nil
}

// Present creates a TXT record using the specified parameters. It
// does this by creating and activating a new temporary Gandi DNS
// zone. This new zone contains the TXT record.
func (d *DNSProvider) Present(domain, token, keyAuth string) error {
	fqdn, value := dns01.GetRecord(domain, keyAuth)

	if d.config.TTL < minTTL {
		d.config.TTL = minTTL // 300 is gandi minimum value for ttl
	}

	// find authZone and Gandi zone_id for fqdn
	authZone, err := d.findZoneByFqdn(fqdn)
	if err != nil {
		return fmt.Errorf("gandi: findZoneByFqdn failure: %w", err)
	}

	zoneID, err := d.getZoneID(authZone)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	// determine name of TXT record
	if !strings.HasSuffix(
		strings.ToLower(fqdn), strings.ToLower("."+authZone)) {
		return fmt.Errorf("gandi: unexpected authZone %s for fqdn %s", authZone, fqdn)
	}
	name := fqdn[:len(fqdn)-len("."+authZone)]

	// acquire lock and check there is not a challenge already in
	// progress for this value of authZone
	d.inProgressMu.Lock()
	defer d.inProgressMu.Unlock()

	if _, ok := d.inProgressAuthZones[authZone]; ok {
		return fmt.Errorf("gandi: challenge already in progress for authZone %s", authZone)
	}

	// perform API actions to create and activate new gandi zone
	// containing the required TXT record
	newZoneName := fmt.Sprintf("%s [ACME Challenge %s]", dns01.UnFqdn(authZone), time.Now().Format(time.RFC822Z))

	newZoneID, err := d.cloneZone(zoneID, newZoneName)
	if err != nil {
		return err
	}

	newZoneVersion, err := d.newZoneVersion(newZoneID)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	err = d.addTXTRecord(newZoneID, newZoneVersion, name, value, d.config.TTL)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	err = d.setZoneVersion(newZoneID, newZoneVersion)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	err = d.setZone(authZone, newZoneID)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	// save data necessary for CleanUp
	d.inProgressFQDNs[fqdn] = inProgressInfo{
		zoneID:    zoneID,
		newZoneID: newZoneID,
		authZone:  authZone,
	}
	d.inProgressAuthZones[authZone] = struct{}{}

	return nil
}

// CleanUp removes the TXT record matching the specified
// parameters. It does this by restoring the old Gandi DNS zone and
// removing the temporary one created by Present.
func (d *DNSProvider) CleanUp(domain, token, keyAuth string) error {
	fqdn, _ := dns01.GetRecord(domain, keyAuth)

	// acquire lock and retrieve zoneID, newZoneID and authZone
	d.inProgressMu.Lock()
	defer d.inProgressMu.Unlock()

	if _, ok := d.inProgressFQDNs[fqdn]; !ok {
		// if there is no cleanup information then just return
		return nil
	}

	zoneID := d.inProgressFQDNs[fqdn].zoneID
	newZoneID := d.inProgressFQDNs[fqdn].newZoneID
	authZone := d.inProgressFQDNs[fqdn].authZone
	delete(d.inProgressFQDNs, fqdn)
	delete(d.inProgressAuthZones, authZone)

	// perform API actions to restore old gandi zone for authZone
	err := d.setZone(authZone, zoneID)
	if err != nil {
		return fmt.Errorf("gandi: %w", err)
	}

	return d.deleteZone(newZoneID)
}

// Timeout returns the values (40*time.Minute, 60*time.Second) which
// are used by the acme package as timeout and check interval values
// when checking for DNS record propagation with Gandi.
func (d *DNSProvider) Timeout() (timeout, interval time.Duration) {
	return d.config.PropagationTimeout, d.config.PollingInterval
}