/*
|--------------------------------------------------------------------------
| Manifest
|--------------------------------------------------------------------------
|
| Name:
|   - datetime
|
| Purpose:
|   - Retrieve and format the current date and time from either the host
|     system clock or a trusted framework-managed NTP source.
|
| Guideline:
|   - Use local for host system clock retrieval.
|   - Use trusted for framework-managed NTP retrieval.
|   - Only use supported framework date/time format patterns.
|   - All responses must be returned as standardized JSON objects.
|
| Example:
|   - ObrimDatetime("local", map[string]any{"format":"yyyy-MM-dd"})
|   - ObrimDatetime("trusted", map[string]any{"format":"timestampsec"})
|
|--------------------------------------------------------------------------
*/

/*
|--------------------------------------------------------------------------
| Credit
|--------------------------------------------------------------------------
|
| Contributor:
|   - Rajon Ahmed
|   - Scionite
|
|--------------------------------------------------------------------------
*/

package datetime

import (
	"encoding/json"
	"errors"
	"net"
	"time"

	"go/module/essential/visible/service/helper/log"
	"go/module/essential/visible/service/helper/status"
)

// ObrimDatetimePayload represents datetime payload data.
type ObrimDatetimePayload struct {
	Value string `json:"value"`
}

// ObrimDatetimeOutput represents utility output structure.
type ObrimDatetimeOutput struct {
	Status  bool                  `json:"status"`
	Code    string                `json:"code"`
	Payload *ObrimDatetimePayload `json:"payload"`
}

// obrimDatetimePatternMap stores framework-supported format mappings.
var obrimDatetimePatternMap = map[string]string{
	"yyyy-MM-dd":               "2006-01-02",
	"MMM dd, yyyy":             "Jan 02, 2006",
	"MMMM dd, yyyy":            "January 02, 2006",
	"EEE, MMM dd, yyyy":        "Mon, Jan 02, 2006",
	"EEE, MMMM dd, yyyy":       "Mon, January 02, 2006",
	"EEEE, MMM dd, yyyy":       "Monday, Jan 02, 2006",
	"EEEE, MMMM dd, yyyy":      "Monday, January 02, 2006",
	"HH:mm:ss":                 "15:04:05",
	"hh:mm:ss a":               "03:04:05 PM",
	"yyyy-MM-dd HH:mm:ss":      "2006-01-02 15:04:05",
	"yyyy-MM-dd HH:mm:ss z":    "2006-01-02 15:04:05 MST",
	"yyyy-MM-dd'T'HH:mm:ssXXX": "2006-01-02T15:04:05Z07:00",
}

// ObrimDatetime retrieves and formats current date and time.
func ObrimDatetime(datetimeType string, config map[string]any) string {
	status.ObrimStatus("INFO", "Initializing datetime utility.")
	log.ObrimLog("INIT", "Datetime utility initialized.")

	if err := obrimDatetimeValidate(datetimeType, config); err != nil {
		status.ObrimStatus("ERROR", err.Error())
		log.ObrimLog("ERROR", err.Error())

		response := obrimDatetimeResponse(false, "FAILED_"+err.Error(), nil)
		return response
	}

	format := config["format"].(string)

	var currentTime time.Time
	var err error

	switch datetimeType {
	case "local":
		currentTime, err = obrimDatetimeLocal()

	case "trusted":
		currentTime, err = obrimDatetimeTrusted()

	default:
		err = errors.New("INVALID_TYPE")
	}

	if err != nil {
		status.ObrimStatus("ERROR", err.Error())
		log.ObrimLog("ERROR", err.Error())

		response := obrimDatetimeResponse(false, "FAILED_"+err.Error(), nil)
		return response
	}

	value, err := obrimDatetimeFormatApply(currentTime, format)
	if err != nil {
		status.ObrimStatus("ERROR", err.Error())
		log.ObrimLog("ERROR", err.Error())

		response := obrimDatetimeResponse(false, "FAILED_"+err.Error(), nil)
		return response
	}

	payload := &ObrimDatetimePayload{
		Value: value,
	}

	status.ObrimStatus("SUCCESS", "Datetime retrieved successfully.")
	log.ObrimLog("SUCCESS", "Datetime retrieved successfully.")

	return obrimDatetimeResponse(
		true,
		"SUCCESS_DATETIME_RETRIEVED",
		payload,
	)
}

// obrimDatetimeValidate validates utility inputs.
func obrimDatetimeValidate(datetimeType string, config map[string]any) error {
	if datetimeType != "local" && datetimeType != "trusted" {
		return errors.New("INVALID_TYPE")
	}

	formatValue, exists := config["format"]
	if !exists {
		return errors.New("INVALID_FORMAT")
	}

	format, ok := formatValue.(string)
	if !ok {
		return errors.New("INVALID_FORMAT")
	}

	if !obrimDatetimePatternValidate(format) {
		return errors.New("INVALID_FORMAT")
	}

	return nil
}

// obrimDatetimePatternValidate validates supported patterns.
func obrimDatetimePatternValidate(pattern string) bool {
	_, exists := obrimDatetimePatternMap[pattern]
	return exists || pattern == "timestampsec" || pattern == "timestampmil"
}

// obrimDatetimePatternResolve resolves framework patterns.
func obrimDatetimePatternResolve(pattern string) (string, error) {
	if pattern == "timestampsec" || pattern == "timestampmil" {
		return pattern, nil
	}

	layout, exists := obrimDatetimePatternMap[pattern]
	if !exists {
		return "", errors.New("INVALID_FORMAT")
	}

	return layout, nil
}

// obrimDatetimeFormatApply applies formatting.
func obrimDatetimeFormatApply(value time.Time, pattern string) (string, error) {
	layout, err := obrimDatetimePatternResolve(pattern)
	if err != nil {
		return "", err
	}

	switch pattern {
	case "timestampsec":
		return time.Unix(value.Unix(), 0).Format("1136239445"), nil

	case "timestampmil":
		return time.UnixMilli(value.UnixMilli()).Format("1136239445000"), nil

	default:
		return value.Format(layout), nil
	}
}

// obrimDatetimeLocal retrieves local system time.
func obrimDatetimeLocal() (time.Time, error) {
	return time.Now(), nil
}

// obrimDatetimeTrusted retrieves trusted time.
func obrimDatetimeTrusted() (time.Time, error) {
	return obrimDatetimeTrustedSync()
}

// obrimDatetimeTrustedSync synchronizes trusted NTP time.
func obrimDatetimeTrustedSync() (time.Time, error) {
	connection, err := net.DialTimeout(
		"udp",
		"time.google.com:123",
		5*time.Second,
	)
	if err != nil {
		return time.Time{}, errors.New("TRUSTED_TIME_RETRIEVAL")
	}

	defer connection.Close()

	request := make([]byte, 48)
	request[0] = 0x1B

	if _, err = connection.Write(request); err != nil {
		return time.Time{}, errors.New("TRUSTED_TIME_RETRIEVAL")
	}

	if err = connection.SetDeadline(time.Now().Add(5 * time.Second)); err != nil {
		return time.Time{}, errors.New("TRUSTED_TIME_RETRIEVAL")
	}

	response := make([]byte, 48)

	if _, err = connection.Read(response); err != nil {
		return time.Time{}, errors.New("TRUSTED_TIME_RETRIEVAL")
	}

	seconds := uint64(response[40])<<24 |
		uint64(response[41])<<16 |
		uint64(response[42])<<8 |
		uint64(response[43])

	const ntpEpochOffset = 2208988800

	unixSeconds := int64(seconds) - ntpEpochOffset

	return time.Unix(unixSeconds, 0).UTC(), nil
}

// obrimDatetimeResponse builds standardized responses.
func obrimDatetimeResponse(
	statusValue bool,
	code string,
	payload *ObrimDatetimePayload,
) string {
	response := ObrimDatetimeOutput{
		Status:  statusValue,
		Code:    code,
		Payload: payload,
	}

	data, err := json.Marshal(response)
	if err != nil {
		fallback := ObrimDatetimeOutput{
			Status:  false,
			Code:    "FAILED_RESPONSE_BUILD",
			Payload: nil,
		}

		data, _ = json.Marshal(fallback)
	}

	return string(data)
}