// Mgmt
// Copyright (C) James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.

package resources

import (
	"context"
	"fmt"

	"github.com/purpleidea/mgmt/engine"
	"github.com/purpleidea/mgmt/engine/traits"
	"github.com/purpleidea/mgmt/util/errwrap"

	"github.com/cloudflare/cloudflare-go/v6"
	"github.com/cloudflare/cloudflare-go/v6/dns"
	"github.com/cloudflare/cloudflare-go/v6/option"
	"github.com/cloudflare/cloudflare-go/v6/zones"
)

func init() {
	engine.RegisterResource("cloudflare:dns", func() engine.Res { return &CloudflareDNSRes{} })
}

// CloudflareDNSRes is a resource for managing DNS records in Cloudflare zones.
// This resource uses the Cloudflare API to create, update, and delete DNS
// records in a specified zone. It supports various record types including A,
// AAAA, CNAME, MX, TXT, NS, SRV, and PTR records. The resource requires polling
// to detect changes, as the Cloudflare API does not provide an event stream.
// The Purge functionality allows enforcing that only managed DNS records exist
// in the zone, removing any unmanaged records.
type CloudflareDNSRes struct {
	traits.Base
	traits.GraphQueryable
	init *engine.Init

	// APIToken is the Cloudflare API token used for authentication. This is
	// required and must have the necessary permissions to manage DNS records
	// in the specified zone.
	APIToken string `lang:"apitoken"`

	// Comment is an optional comment to attach to the DNS record. This is
	// stored in Cloudflare and can be used for documentation purposes.
	Comment string `lang:"comment"`

	// Content is the value for the DNS record. This is required when State
	// is "exists" unless Purge is true. The format depends on the record
	// Type (e.g., IP address for A records, hostname for CNAME records).
	Content string `lang:"content"`

	// Priority is the priority value for records that support it (e.g., MX
	// records). This is a pointer to distinguish between an unset value and
	// a zero value.
	Priority *int64 `lang:"priority"`

	// Proxied specifies whether the record should be proxied through
	// Cloudflare's CDN. This is a pointer to distinguish between an unset
	// value and false. Only applicable to certain record types.
	Proxied *bool `lang:"proxied"`

	// Purge specifies whether to delete all DNS records in the zone that are
	// not defined in the mgmt graph. When true, this resource will query the
	// graph for other cloudflare:dns resources in the same zone and delete
	// any records not managed by those resources.
	Purge bool `lang:"purge"`

	// RecordName is the name of the DNS record (e.g., "www.example.com" or
	// "@" for the zone apex). This is required.
	RecordName string `lang:"record_name"`

	// State determines whether the DNS record should exist or be absent.
	// Valid values are "exists" (default) or "absent". When set to "absent",
	// the record will be deleted if it exists.
	State string `lang:"state"`

	// TTL is the time-to-live value for the DNS record in seconds. Must be
	// between 60 and 86400, or set to 1 for automatic TTL. Default is 1.
	TTL int64 `lang:"ttl"`

	// Type is the DNS record type (e.g., "A", "AAAA", "CNAME", "MX", "TXT",
	// "NS", "SRV", "PTR"). This is required.
	Type string `lang:"type"`

	// Zone is the name of the Cloudflare zone (domain) where the DNS record
	// should be managed (e.g., "example.com"). This is required.
	Zone string `lang:"zone"`

	client *cloudflare.Client
	zoneID string
}

// Default returns some sensible defaults for this resource.
func (obj *CloudflareDNSRes) Default() engine.Res {
	return &CloudflareDNSRes{
		State: "exists",
		TTL:   1, // this sets TTL to automatic
	}
}

// Validate checks if the resource data structure was populated correctly.
func (obj *CloudflareDNSRes) Validate() error {
	if obj.RecordName == "" {
		return fmt.Errorf("record name is required")
	}

	if obj.APIToken == "" {
		return fmt.Errorf("API token is required")
	}

	if obj.Type == "" {
		return fmt.Errorf("record type is required")
	}

	if (obj.TTL < 60 || obj.TTL > 86400) && obj.TTL != 1 { // API requirement
		return fmt.Errorf("TTL must be between 60s and 86400s, or set to 1")
	}

	if obj.Zone == "" {
		return fmt.Errorf("zone name is required")
	}

	if obj.State != "exists" && obj.State != "absent" && obj.State != "" {
		return fmt.Errorf("state must be either 'exists', 'absent', or empty")
	}

	if obj.State == "exists" && obj.Content == "" && !obj.Purge {
		return fmt.Errorf("content is required when state is 'exists'")
	}

	if obj.MetaParams().Poll == 0 || obj.MetaParams().Poll < 1 { // CF accepts ~4req/s so this is good enough
		return fmt.Errorf("cloudflare:dns requires polling, set Meta:poll param	(e.g., 60 seconds), min. 1s")
	}

	return nil
}

// Init runs some startup code for this resource. It initializes the Cloudflare
// API client and validates that the specified zone exists.
func (obj *CloudflareDNSRes) Init(init *engine.Init) error {
	obj.init = init

	obj.client = cloudflare.NewClient(
		option.WithAPIToken(obj.APIToken),
	)

	//TODO: does it make more sense to check it here or in CheckApply()?
	zoneListParams := zones.ZoneListParams{
		Name: cloudflare.F(obj.Zone),
	}

	zoneList, err := obj.client.Zones.List(context.Background(), zoneListParams)
	if err != nil {
		return errwrap.Wrapf(err, "failed to list zones")
	}

	if len(zoneList.Result) == 0 {
		return fmt.Errorf("zone %s not found", obj.Zone)
	}

	obj.zoneID = zoneList.Result[0].ID

	return nil
}

// Cleanup is run by the engine to clean up after the resource is done. It
// clears sensitive data and releases the API client connection.
func (obj *CloudflareDNSRes) Cleanup() error {
	obj.APIToken = ""
	obj.client = nil
	obj.zoneID = ""
	return nil
}

// Watch isn't implemented for this resource, since the Cloudflare API does not
// provide any event stream. Instead, always use polling.
func (obj *CloudflareDNSRes) Watch(context.Context) error {
	return fmt.Errorf("invalid Watch call: requires poll metaparam")
}

// CheckApply is the main convergence function for this resource. It checks the
// current state of the DNS record against the desired state and applies changes
// if necessary. If apply is false, it only checks if changes are needed. If
// Purge is enabled, it will first delete any unmanaged records in the zone.
func (obj *CloudflareDNSRes) CheckApply(ctx context.Context, apply bool) (bool, error) {
	zone, err := obj.client.Zones.List(ctx, zones.ZoneListParams{
		Name: cloudflare.F(obj.Zone),
	})
	if err != nil {
		return false, err
	}

	if len(zone.Result) == 0 {
		return false, fmt.Errorf("there's no zone registered with name %s", obj.Zone)
	}

	if len(zone.Result) > 1 {
		return false, fmt.Errorf("there's more than one zone with name %s", obj.Zone)
	}

	// We start by checking the need for purging
	if obj.Purge {
		checkOK, err := obj.purgeCheckApply(ctx, apply)
		if err != nil {
			return false, err
		}
		if !checkOK {
			return false, nil
		}
	}

	// List existing records
	listParams := dns.RecordListParams{
		ZoneID: cloudflare.F(obj.zoneID),
		Name: cloudflare.F(dns.RecordListParamsName{
			Contains: cloudflare.F(obj.RecordName),
		}),
		Type: cloudflare.F(dns.RecordListParamsType(obj.Type)),
	}

	recordList, err := obj.client.DNS.Records.List(ctx, listParams)
	if err != nil {
		return false, errwrap.Wrapf(err, "failed to list DNS records")
	}

	recordExists := len(recordList.Result) > 0
	var record dns.RecordResponse
	if recordExists {
		record = recordList.Result[0]
	}

	switch obj.State {
	case "exists", "":
		if !recordExists {
			if !apply {
				return false, nil
			}

			if err := obj.createRecord(ctx); err != nil {
				return false, err
			}

			return true, nil
		}

		if obj.needsUpdate(record) {
			if !apply {
				return false, nil
			}

			if err := obj.updateRecord(ctx, record.ID); err != nil {
				return false, err
			}
			return true, nil
		}

	case "absent":
		if recordExists {
			if !apply {
				return false, nil
			}

			deleteParams := dns.RecordDeleteParams{
				ZoneID: cloudflare.F(obj.zoneID),
			}

			_, err := obj.client.DNS.Records.Delete(ctx, record.ID, deleteParams)
			if err != nil {
				return false, errwrap.Wrapf(err, "failed to delete DNS record")
			}
			return true, nil
		}
	}

	return true, nil
}

// Cmp compares two resources and returns an error if they differ. This is used
// to determine if two resources are equivalent for graph operations.
func (obj *CloudflareDNSRes) Cmp(r engine.Res) error {
	if obj == nil && r == nil {
		return nil
	}

	if (obj == nil) != (r == nil) {
		return fmt.Errorf("one resource is empty")
	}

	res, ok := r.(*CloudflareDNSRes)
	if !ok {
		return fmt.Errorf("not a %s", obj.Kind())
	}

	if obj.APIToken != res.APIToken {
		return fmt.Errorf("apitoken differs")
	}

	if (obj.Proxied == nil) != (res.Proxied == nil) {
		return fmt.Errorf("proxied values differ")
	}

	if obj.Proxied != nil && *obj.Proxied != *res.Proxied {
		return fmt.Errorf("proxied values differ")
	}

	if obj.RecordName != res.RecordName {
		return fmt.Errorf("record name differs")
	}

	if obj.Purge != res.Purge {
		return fmt.Errorf("purge value differs")
	}

	if obj.State != res.State {
		return fmt.Errorf("state differs")
	}

	if obj.TTL != res.TTL {
		return fmt.Errorf("ttl differs")
	}

	if obj.Type != res.Type {
		return fmt.Errorf("record type differs")
	}

	if obj.Zone != res.Zone {
		return fmt.Errorf("zone differs")
	}

	if obj.zoneID != res.zoneID {
		return fmt.Errorf("zoneid differs")
	}

	if obj.Content != res.Content {
		return fmt.Errorf("content param differs")
	}

	if obj.Priority != res.Priority {
		return fmt.Errorf("the priority param differs")
	}

	return nil
}

// buildRecordParam creates the appropriate record parameter structure based on
// the record type. This is a helper function used by buildNewRecordParam and
// buildEditRecordParam.
// TODO: double check the fields for each record, might have missed some
func (obj *CloudflareDNSRes) buildRecordParam() (any, error) {
	ttl := dns.TTL(obj.TTL)

	switch obj.Type {
	case "A":
		param := dns.ARecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.ARecordTypeA),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "AAAA":
		param := dns.AAAARecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.AAAARecordTypeAAAA),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "CNAME":
		param := dns.CNAMERecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.CNAMERecordTypeCNAME),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "MX":
		param := dns.MXRecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.MXRecordTypeMX),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Priority != nil { // required for MX record
			param.Priority = cloudflare.F(float64(*obj.Priority))
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "TXT":
		param := dns.TXTRecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.TXTRecordTypeTXT),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "NS":
		param := dns.NSRecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.NSRecordTypeNS),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "SRV":
		param := dns.SRVRecordParam{
			Name: cloudflare.F(obj.RecordName),
			Type: cloudflare.F(dns.SRVRecordTypeSRV),
			TTL:  cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	case "PTR":
		param := dns.PTRRecordParam{
			Name:    cloudflare.F(obj.RecordName),
			Type:    cloudflare.F(dns.PTRRecordTypePTR),
			Content: cloudflare.F(obj.Content),
			TTL:     cloudflare.F(ttl),
		}
		if obj.Proxied != nil {
			param.Proxied = cloudflare.F(*obj.Proxied)
		}
		if obj.Comment != "" {
			param.Comment = cloudflare.F(obj.Comment)
		}
		return param, nil

	default:
		return nil, fmt.Errorf("record type %s is not supported", obj.Type)

	}
}

// buildNewRecordParam creates the appropriate record parameter for creating new
// records.
func (obj *CloudflareDNSRes) buildNewRecordParam() (dns.RecordNewParamsBodyUnion, error) {
	result, err := obj.buildRecordParam()
	if err != nil {
		return nil, err
	}
	return result.(dns.RecordNewParamsBodyUnion), nil
}

// buildEditRecordParam creates the appropriate record parameter for editing
// records.
func (obj *CloudflareDNSRes) buildEditRecordParam() (dns.RecordEditParamsBodyUnion, error) {
	result, err := obj.buildRecordParam()
	if err != nil {
		return nil, err
	}
	return result.(dns.RecordEditParamsBodyUnion), nil
}

// createRecord creates a new DNS record in Cloudflare using the resource's
// parameters.
func (obj *CloudflareDNSRes) createRecord(ctx context.Context) error {
	recordParams, err := obj.buildNewRecordParam()
	if err != nil {
		return err
	}

	createParams := dns.RecordNewParams{
		ZoneID: cloudflare.F(obj.zoneID),
		Body:   recordParams,
	}

	_, err = obj.client.DNS.Records.New(ctx, createParams)
	if err != nil {
		return errwrap.Wrapf(err, "failed to create dns record")
	}

	return nil
}

// updateRecord updates an existing DNS record in Cloudflare with the resource's
// parameters.
func (obj *CloudflareDNSRes) updateRecord(ctx context.Context, recordID string) error {
	recordParams, err := obj.buildEditRecordParam()
	if err != nil {
		return err
	}

	editParams := dns.RecordEditParams{
		ZoneID: cloudflare.F(obj.zoneID),
		Body:   recordParams,
	}

	_, err = obj.client.DNS.Records.Edit(ctx, recordID, editParams)
	if err != nil {
		return errwrap.Wrapf(err, "failed to update dns record")
	}

	return nil
}

// needsUpdate compares the current DNS record with the desired state and
// returns true if an update is needed.
func (obj *CloudflareDNSRes) needsUpdate(record dns.RecordResponse) bool {
	if obj.Content != record.Content {
		return true
	}

	if obj.TTL != int64(record.TTL) {
		return true
	}

	if obj.Proxied != nil {
		if *obj.Proxied != record.Proxied {
			return true
		}
	}

	if obj.Priority != nil {
		if float64(*obj.Priority) != record.Priority {
			return true
		}
	}

	if obj.Comment != record.Comment {
		return true
	}

	// TODO add more checks?

	return false

}

// purgeCheckApply deletes all DNS records in the zone that are not defined in
// the mgmt graph. It queries the graph for other cloudflare:dns resources in
// the same zone and builds an exclusion list. If apply is false, it only checks
// if purge is needed.
func (obj *CloudflareDNSRes) purgeCheckApply(ctx context.Context, apply bool) (bool, error) {
	listParams := dns.RecordListParams{
		ZoneID: cloudflare.F(obj.zoneID),
	}

	iter := obj.client.DNS.Records.ListAutoPaging(ctx, listParams)

	allRecords := []dns.RecordResponse{}
	for iter.Next() {
		allRecords = append(allRecords, iter.Current())
	}
	if err := iter.Err(); err != nil {
		return false, errwrap.Wrapf(err, "failed to list dns records for purge")
	}

	excludes := make(map[string]bool)

	graph, err := obj.init.FilteredGraph()
	if err != nil {
		return false, errwrap.Wrapf(err, "can't read the filtered graph")
	}

	for _, vertex := range graph.Vertices() {
		res, ok := vertex.(engine.Res)
		if !ok {
			return false, fmt.Errorf("not a resource")
		}
		if res.Kind() != "cloudflare:dns" {
			continue // we only want cloudflare dns resources
		}
		if res.Name() == obj.Name() {
			continue // skip self
		}

		cfRes, ok := res.(*CloudflareDNSRes)
		if !ok {
			return false, fmt.Errorf("wrong resource type")
		}

		if cfRes.Zone == obj.Zone {
			recordKey := fmt.Sprintf("%s:%s", cfRes.RecordName, cfRes.Type)
			excludes[recordKey] = true
		}
	}

	checkOK := true

	for _, record := range allRecords {
		recordKey := fmt.Sprintf("%s:%s", record.Name, record.Type)

		if excludes[recordKey] {
			continue
		}

		if apply {
			deleteParams := dns.RecordDeleteParams{
				ZoneID: cloudflare.F(obj.zoneID),
			}
			_, err := obj.client.DNS.Records.Delete(ctx, record.ID, deleteParams)
			if err != nil {
				return false, errwrap.Wrapf(err, "failed to purge %s", recordKey)
			}
		} else {
			checkOK = false
		}
	}

	return checkOK, nil
}

// GraphQueryAllowed returns nil if you're allowed to query the graph. This
// function accepts information about the requesting resource so we can
// determine the access with some form of fine-grained control.
func (obj *CloudflareDNSRes) GraphQueryAllowed(opts ...engine.GraphQueryableOption) error {
	options := &engine.GraphQueryableOptions{} // default options
	options.Apply(opts...)                     // apply the options
	if options.Kind != "cloudflare:dns" {
		return fmt.Errorf("only other cloudflare dns resources can access this info")
	}
	return nil
}