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

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"time"

	"github.com/xenolf/lego/acme"
)

// rackspaceAPIURL represents the Identity API endpoint to call
var rackspaceAPIURL = "https://identity.api.rackspacecloud.com/v2.0/tokens"

// DNSProvider is an implementation of the acme.ChallengeProvider interface
// used to store the reusable token and DNS API endpoint
type DNSProvider struct {
	token            string
	cloudDNSEndpoint string
}

// NewDNSProvider returns a DNSProvider instance configured for Rackspace.
// Credentials must be passed in the environment variables: RACKSPACE_USER
// and RACKSPACE_API_KEY.
func NewDNSProvider() (*DNSProvider, error) {
	user := os.Getenv("RACKSPACE_USER")
	key := os.Getenv("RACKSPACE_API_KEY")
	return NewDNSProviderCredentials(user, key)
}

// NewDNSProviderCredentials uses the supplied credentials to return a
// DNSProvider instance configured for Rackspace. It authenticates against
// the API, also grabbing the DNS Endpoint.
func NewDNSProviderCredentials(user, key string) (*DNSProvider, error) {
	if user == "" || key == "" {
		return nil, fmt.Errorf("Rackspace credentials missing")
	}

	type APIKeyCredentials struct {
		Username string `json:"username"`
		APIKey   string `json:"apiKey"`
	}

	type Auth struct {
		APIKeyCredentials `json:"RAX-KSKEY:apiKeyCredentials"`
	}

	type RackspaceAuthData struct {
		Auth `json:"auth"`
	}

	type RackspaceIdentity struct {
		Access struct {
			ServiceCatalog []struct {
				Endpoints []struct {
					PublicURL string `json:"publicURL"`
					TenantID  string `json:"tenantId"`
				} `json:"endpoints"`
				Name string `json:"name"`
			} `json:"serviceCatalog"`
			Token struct {
				ID string `json:"id"`
			} `json:"token"`
		} `json:"access"`
	}

	authData := RackspaceAuthData{
		Auth: Auth{
			APIKeyCredentials: APIKeyCredentials{
				Username: user,
				APIKey:   key,
			},
		},
	}

	body, err := json.Marshal(authData)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequest("POST", rackspaceAPIURL, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")

	client := http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("Error querying Rackspace Identity API: %v", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("Rackspace Authentication failed. Response code: %d", resp.StatusCode)
	}

	var rackspaceIdentity RackspaceIdentity
	err = json.NewDecoder(resp.Body).Decode(&rackspaceIdentity)
	if err != nil {
		return nil, err
	}

	// Iterate through the Service Catalog to get the DNS Endpoint
	var dnsEndpoint string
	for _, service := range rackspaceIdentity.Access.ServiceCatalog {
		if service.Name == "cloudDNS" {
			dnsEndpoint = service.Endpoints[0].PublicURL
			break
		}
	}
	if dnsEndpoint == "" {
		return nil, fmt.Errorf("Failed to populate DNS endpoint, check Rackspace API for changes.")
	}

	return &DNSProvider{
		token:            rackspaceIdentity.Access.Token.ID,
		cloudDNSEndpoint: dnsEndpoint,
	}, nil
}

// Present creates a TXT record to fulfil the dns-01 challenge
func (c *DNSProvider) Present(domain, token, keyAuth string) error {
	fqdn, value, _ := acme.DNS01Record(domain, keyAuth)
	zoneID, err := c.getHostedZoneID(fqdn)
	if err != nil {
		return err
	}

	rec := RackspaceRecords{
		RackspaceRecord: []RackspaceRecord{{
			Name: acme.UnFqdn(fqdn),
			Type: "TXT",
			Data: value,
			TTL:  300,
		}},
	}

	body, err := json.Marshal(rec)
	if err != nil {
		return err
	}

	_, err = c.makeRequest("POST", fmt.Sprintf("/domains/%d/records", zoneID), bytes.NewReader(body))
	if err != nil {
		return err
	}

	return nil
}

// CleanUp removes the TXT record matching the specified parameters
func (c *DNSProvider) CleanUp(domain, token, keyAuth string) error {
	fqdn, _, _ := acme.DNS01Record(domain, keyAuth)
	zoneID, err := c.getHostedZoneID(fqdn)
	if err != nil {
		return err
	}

	record, err := c.findTxtRecord(fqdn, zoneID)
	if err != nil {
		return err
	}

	_, err = c.makeRequest("DELETE", fmt.Sprintf("/domains/%d/records?id=%s", zoneID, record.ID), nil)
	if err != nil {
		return err
	}

	return nil
}

// getHostedZoneID performs a lookup to get the DNS zone which needs
// modifying for a given FQDN
func (c *DNSProvider) getHostedZoneID(fqdn string) (int, error) {
	// HostedZones represents the response when querying Rackspace DNS zones
	type ZoneSearchResponse struct {
		TotalEntries int `json:"totalEntries"`
		HostedZones  []struct {
			ID   int    `json:"id"`
			Name string `json:"name"`
		} `json:"domains"`
	}

	authZone, err := acme.FindZoneByFqdn(fqdn, acme.RecursiveNameservers)
	if err != nil {
		return 0, err
	}

	result, err := c.makeRequest("GET", fmt.Sprintf("/domains?name=%s", acme.UnFqdn(authZone)), nil)
	if err != nil {
		return 0, err
	}

	var zoneSearchResponse ZoneSearchResponse
	err = json.Unmarshal(result, &zoneSearchResponse)
	if err != nil {
		return 0, err
	}

	// If nothing was returned, or for whatever reason more than 1 was returned (the search uses exact match, so should not occur)
	if zoneSearchResponse.TotalEntries != 1 {
		return 0, fmt.Errorf("Found %d zones for %s in Rackspace for domain %s", zoneSearchResponse.TotalEntries, authZone, fqdn)
	}

	return zoneSearchResponse.HostedZones[0].ID, nil
}

// findTxtRecord searches a DNS zone for a TXT record with a specific name
func (c *DNSProvider) findTxtRecord(fqdn string, zoneID int) (*RackspaceRecord, error) {
	result, err := c.makeRequest("GET", fmt.Sprintf("/domains/%d/records?type=TXT&name=%s", zoneID, acme.UnFqdn(fqdn)), nil)
	if err != nil {
		return nil, err
	}

	var records RackspaceRecords
	err = json.Unmarshal(result, &records)
	if err != nil {
		return nil, err
	}

	recordsLength := len(records.RackspaceRecord)
	switch recordsLength {
	case 1:
		break
	case 0:
		return nil, fmt.Errorf("No TXT record found for %s", fqdn)
	default:
		return nil, fmt.Errorf("More than 1 TXT record found for %s", fqdn)
	}

	return &records.RackspaceRecord[0], nil
}

// makeRequest is a wrapper function used for making DNS API requests
func (c *DNSProvider) makeRequest(method, uri string, body io.Reader) (json.RawMessage, error) {
	url := c.cloudDNSEndpoint + uri
	req, err := http.NewRequest(method, url, body)
	if err != nil {
		return nil, err
	}

	req.Header.Set("X-Auth-Token", c.token)
	req.Header.Set("Content-Type", "application/json")

	client := http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("Error querying DNS API: %v", err)
	}

	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusAccepted {
		return nil, fmt.Errorf("Request failed for %s %s. Response code: %d", method, url, resp.StatusCode)
	}

	var r json.RawMessage
	err = json.NewDecoder(resp.Body).Decode(&r)
	if err != nil {
		return nil, fmt.Errorf("JSON decode failed for %s %s. Response code: %d", method, url, resp.StatusCode)
	}

	return r, nil
}

// RackspaceRecords is the list of records sent/received from the DNS API
type RackspaceRecords struct {
	RackspaceRecord []RackspaceRecord `json:"records"`
}

// RackspaceRecord represents a Rackspace DNS record
type RackspaceRecord struct {
	Name string `json:"name"`
	Type string `json:"type"`
	Data string `json:"data"`
	TTL  int    `json:"ttl,omitempty"`
	ID   string `json:"id,omitempty"`
}