package onboarding

import (
	"context"
	"errors"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common"
	"github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common/profile"
	sms "github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/sms/v20210111"
)

// Tencent SMS accepts a request before the carrier delivers it. A failed or
// ambiguous call is never retried here: the challenge remains subject to the
// existing resend limits and cannot cause an accidental duplicate charge.
type tencentSMSSender interface {
	SendSmsWithContext(context.Context, *sms.SendSmsRequest) (*sms.SendSmsResponse, error)
}

type TencentSMSProvider struct {
	parameters      map[string][]string
	client          tencentSMSSender
	appID, signName string
	templates       map[string]string
}

var mainlandPhonePattern = regexp.MustCompile(`^\+86[1][3-9][0-9]{9}$`)
var smsTemplateIDPattern = regexp.MustCompile(`^[0-9]+$`)

const (
	SMSPurposeLogin          = "LOGIN"
	SMSPurposeRegister       = "REGISTER"
	SMSPurposeChangePassword = "CHANGE_PASSWORD"
	SMSPurposeChangePhone    = "CHANGE_PHONE"
)

var smsTemplateKeys = map[string]string{
	SMSPurposeLogin: "login", SMSPurposeRegister: "register",
	SMSPurposeChangePassword: "change_password", SMSPurposeChangePhone: "change_phone",
}

func NewTencentSMSProvider(secretID, secretKey, appID, signName, templateID string) (SMSProvider, error) {
	// Keep the original single-template environment configuration compatible.
	return NewTencentSMSProviderWithTemplates(secretID, secretKey, appID, signName, map[string]string{
		"login": templateID, "register": templateID, "change_password": templateID, "change_phone": templateID,
	})
}

func NewTencentSMSProviderWithTemplates(secretID, secretKey, appID, signName string, templates map[string]string, parameterOptions ...map[string][]string) (SMSProvider, error) {
	if strings.TrimSpace(secretID) == "" || strings.TrimSpace(secretKey) == "" ||
		!smsTemplateIDPattern.MatchString(appID) || strings.TrimSpace(signName) == "" {
		return nil, errors.New("Tencent SMS requires SecretId, SecretKey, numeric SDK AppID and approved sign name")
	}
	copyTemplates := make(map[string]string, len(smsTemplateKeys))
	parameters := make(map[string][]string, len(smsTemplateKeys))
	for _, key := range smsTemplateKeys {
		if !smsTemplateIDPattern.MatchString(templates[key]) {
			return nil, errors.New("Tencent SMS requires numeric login, register, change_password and change_phone template IDs")
		}
		copyTemplates[key] = templates[key]
		parameters[key] = []string{"code"}
	}
	if len(parameterOptions) > 1 {
		return nil, errors.New("Tencent SMS accepts one template parameter configuration")
	}
	if len(parameterOptions) == 1 {
		for key, values := range parameterOptions[0] {
			if _, ok := copyTemplates[key]; !ok {
				return nil, errors.New("Tencent SMS template parameters have an unknown purpose")
			}
			seen := map[string]bool{}
			for _, value := range values {
				if (value != "code" && value != "expires_minutes") || seen[value] {
					return nil, errors.New("Tencent SMS template parameters must be code and optionally expires_minutes")
				}
				seen[value] = true
			}
			if !seen["code"] {
				return nil, errors.New("Tencent SMS template parameters must include code")
			}
			parameters[key] = append([]string(nil), values...)
		}
	}
	clientProfile := profile.NewClientProfile()
	clientProfile.HttpProfile.Endpoint = "sms.tencentcloudapi.com"
	clientProfile.HttpProfile.ReqTimeout = 10
	clientProfile.NetworkFailureMaxRetries = 0
	clientProfile.RateLimitExceededMaxRetries = 0
	clientProfile.UnsafeRetryOnConnectionFailure = false
	client, err := sms.NewClient(common.NewCredential(secretID, secretKey), "ap-guangzhou", clientProfile)
	if err != nil {
		return nil, err
	}
	return &TencentSMSProvider{client: client, appID: appID, signName: signName, templates: copyTemplates, parameters: parameters}, nil
}

func (p *TencentSMSProvider) Send(ctx context.Context, phone, code, id string) error {
	return p.SendForPurpose(ctx, phone, code, id, SMSPurposeLogin)
}

func (p *TencentSMSProvider) SendForPurpose(ctx context.Context, phone, code, id, purpose string) error {
	templateID := p.templates[smsTemplateKeys[purpose]]
	if templateID == "" || !mainlandPhonePattern.MatchString(phone) || !smsCodePattern.MatchString(code) || !uuidV4(id) {
		return errors.New("SMS_GATEWAY_REJECTED")
	}
	req := sms.NewSendSmsRequest()
	req.PhoneNumberSet = common.StringPtrs([]string{phone})
	req.SmsSdkAppId = common.StringPtr(p.appID)
	req.SignName = common.StringPtr(p.signName)
	req.TemplateId = common.StringPtr(templateID)
	values := make([]string, 0, len(p.parameters[smsTemplateKeys[purpose]]))
	for _, name := range p.parameters[smsTemplateKeys[purpose]] {
		if name == "code" {
			values = append(values, code)
		} else {
			values = append(values, strconv.Itoa(int(smsCodeLifetime/time.Minute)))
		}
	}
	req.TemplateParamSet = common.StringPtrs(values)
	req.SessionContext = common.StringPtr(id)
	result, err := p.client.SendSmsWithContext(ctx, req)
	if err != nil {
		return errors.New("SMS_GATEWAY_UNCERTAIN")
	}
	if result == nil || result.Response == nil || len(result.Response.SendStatusSet) != 1 ||
		result.Response.SendStatusSet[0] == nil || result.Response.SendStatusSet[0].Code == nil ||
		*result.Response.SendStatusSet[0].Code != "Ok" {
		return errors.New("SMS_GATEWAY_REJECTED")
	}
	return nil
}