// Package handler provides HTTP handlers for various endpoints.
package handler

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strconv"
	"strings"

	"modelRT/common"
	"modelRT/common/errcode"
	"modelRT/constants"
	"modelRT/diagram"
	"modelRT/logger"
	"modelRT/model"
	"modelRT/orm"

	"github.com/gin-gonic/gin"
	"github.com/redis/go-redis/v9"
)

// DataObjectAttributeQueryHandler define data object attribute value query process API
func DataObjectAttributeQueryHandler(c *gin.Context) {
	ctx := c.Request.Context()

	token, field, err := parseDataObjectAttributeQuery(c)
	if err != nil {
		logger.Error(ctx, "query token from query parameters failed", "error", err, "url", c.Request.RequestURI)
		renderRespFailure(c, constants.RespCodeInvalidParams, err.Error(), nil)
		return
	}

	dataObjectType, err := model.ClassifyDataObjectToken(token)
	if err != nil {
		logger.Error(ctx, "classify data object token failed", "error", err, "url", c.Request.RequestURI)
		renderRespFailure(c, constants.RespCodeInvalidParams, err.Error(), nil)
		return
	}

	if err := validateDataObjectField(dataObjectType, field); err != nil {
		logger.Warn(ctx, "validate data object field failed", "token", token, "field", field, "error", err)
		renderRespFailure(c, constants.RespCodeInvalidParams, err.Error(), nil)
		return
	}

	value, err := queryDataObjectAttributeValue(
		ctx,
		dataObjectType,
		token,
		field,
		loadDataObjectHashField,
		loadMeasurementValueMetadata,
		queryMeasurementRealtimeValue,
	)
	if err != nil {
		if isDataObjectTokenNotFound(err) {
			logger.Warn(ctx, "query data-object token from redis failed", "token", token, "field", field, "error", err)
			renderRespFailure(c, constants.RespCodeInvalidParams, err.Error(), nil)
			return
		}

		logger.Error(ctx, "query data-object attribute from redis failed", "token", token, "field", field, "error", err)
		renderRespFailure(c, constants.RespCodeServerError, dataObjectAttributeFailureMessage(dataObjectType), nil)
		return
	}

	result := dataObjectAttributeQueryResult{
		Token: token,
		Field: field,
		Code:  errcode.ErrProcessSuccess.Code(),
		Msg:   errcode.ErrProcessSuccess.Msg(),
		Value: value,
	}
	renderRespSuccess(c, constants.RespCodeSuccess, dataObjectAttributeSuccessMessage(dataObjectType), map[string]any{
		"attributes": []dataObjectAttributeQueryResult{result},
	})
}

func parseDataObjectAttributeQuery(c *gin.Context) (string, string, error) {
	token := c.Query("token")
	if token == "" {
		return "", "", fmt.Errorf("token is missing from query parameters")
	}

	field := strings.ToLower(c.Query("field"))
	if field == "" {
		field = "value"
	}
	return token, field, nil
}

type dataObjectHashFieldLoader func(context.Context, constants.DataObjectType, string, string) (string, error)

type measurementValueMetadataLoader func(context.Context, string) (orm.JSONMap, int, error)

type measurementValueLoader func(context.Context, orm.JSONMap, int) (any, error)

var measurementDataObjectFields = map[string]struct{}{
	"value":       {},
	"mode":        {},
	"meta":        {},
	"type":        {},
	"name":        {},
	"description": {},
	"id":          {},
	"size":        {},
	"data_source": {},
	"event_plan":  {},
	"binding":     {},
}

var parameterDataObjectFields = map[string]struct{}{
	"value":       {},
	"name":        {},
	"meta":        {},
	"type":        {},
	"description": {},
	"id":          {},
}

type dataObjectAttributeQueryResult struct {
	Token string `json:"token"`
	Field string `json:"field"`
	Code  int    `json:"code"`
	Msg   string `json:"msg"`
	Value any    `json:"value"`
}

func validateDataObjectField(dataObjectType constants.DataObjectType, field string) error {
	field = strings.ToLower(field)
	switch dataObjectType {
	case constants.DataObjectTypeMeasurement:
		if _, ok := measurementDataObjectFields[field]; ok {
			return nil
		}
		return fmt.Errorf("%w: %s", common.ErrUnsupportedMeasurementField, field)
	case constants.DataObjectTypeParameter:
		if _, ok := parameterDataObjectFields[field]; ok {
			return nil
		}
		return fmt.Errorf("%w: %s", common.ErrUnsupportedParameterField, field)
	default:
		return fmt.Errorf("invalid data object type %q", dataObjectType)
	}
}

func queryDataObjectAttributeValue(
	ctx context.Context,
	dataObjectType constants.DataObjectType,
	token string,
	field string,
	loadHashField dataObjectHashFieldLoader,
	loadMeasurementMetadata measurementValueMetadataLoader,
	loadMeasurementValue measurementValueLoader,
) (any, error) {
	if dataObjectType == constants.DataObjectTypeMeasurement && field == "value" {
		if loadMeasurementMetadata == nil {
			return nil, fmt.Errorf("measurement value metadata loader is nil")
		}
		if loadMeasurementValue == nil {
			return nil, fmt.Errorf("measurement value loader is nil")
		}
		dataSource, size, err := loadMeasurementMetadata(ctx, token)
		if err != nil {
			return nil, err
		}
		return loadMeasurementValue(ctx, dataSource, size)
	}

	if loadHashField == nil {
		return nil, fmt.Errorf("data-object hash field loader is nil")
	}
	rawValue, err := loadHashField(ctx, dataObjectType, token, field)
	if err != nil {
		return nil, err
	}
	if dataObjectType == constants.DataObjectTypeParameter && field == "value" {
		attributeType, err := loadHashField(ctx, dataObjectType, token, "type")
		if err != nil {
			return nil, err
		}
		return decodeParameterHashValue(rawValue, attributeType)
	}
	return decodeDataObjectHashField(dataObjectType, field, rawValue)
}

func loadDataObjectHashField(
	ctx context.Context,
	dataObjectType constants.DataObjectType,
	token string,
	field string,
) (string, error) {
	rdb := diagram.GetRedisClientInstance()
	if rdb == nil {
		return "", fmt.Errorf("redis client is not initialized")
	}
	canonicalKey, err := model.ResolveDataObjectRedisKey(ctx, rdb, dataObjectType, token)
	if err != nil {
		return "", err
	}
	value, err := rdb.HGet(ctx, canonicalKey, field).Result()
	if errors.Is(err, redis.Nil) {
		return "", fmt.Errorf("canonical redis data-object hash %q does not contain field %q", canonicalKey, field)
	}
	if err != nil {
		return "", fmt.Errorf("query canonical redis hash %q field %q: %w", canonicalKey, field, err)
	}
	return value, nil
}

func loadMeasurementValueMetadata(ctx context.Context, token string) (orm.JSONMap, int, error) {
	rdb := diagram.GetRedisClientInstance()
	if rdb == nil {
		return nil, 0, fmt.Errorf("redis client is not initialized")
	}
	canonicalKey, err := model.ResolveDataObjectRedisKey(ctx, rdb, constants.DataObjectTypeMeasurement, token)
	if err != nil {
		return nil, 0, err
	}
	values, err := rdb.HMGet(ctx, canonicalKey, "data_source", "size").Result()
	if err != nil {
		return nil, 0, fmt.Errorf("query canonical redis hash %q measurement value metadata: %w", canonicalKey, err)
	}
	if len(values) != 2 {
		return nil, 0, fmt.Errorf("canonical redis hash %q returned %d measurement metadata fields", canonicalKey, len(values))
	}
	if values[0] == nil || values[1] == nil {
		missingFields := make([]string, 0, 2)
		if values[0] == nil {
			missingFields = append(missingFields, "data_source")
		}
		if values[1] == nil {
			missingFields = append(missingFields, "size")
		}
		return nil, 0, fmt.Errorf(
			"canonical redis measurement hash %q does not contain field(s) %s",
			canonicalKey,
			strings.Join(missingFields, ", "),
		)
	}

	rawDataSource, ok := values[0].(string)
	if !ok {
		return nil, 0, fmt.Errorf("canonical redis measurement hash %q data_source has type %T", canonicalKey, values[0])
	}
	var dataSource orm.JSONMap
	if err := json.Unmarshal([]byte(rawDataSource), &dataSource); err != nil {
		return nil, 0, fmt.Errorf("decode measurement data_source from canonical redis hash %q: %w", canonicalKey, err)
	}

	rawSize, ok := values[1].(string)
	if !ok {
		return nil, 0, fmt.Errorf("canonical redis measurement hash %q size has type %T", canonicalKey, values[1])
	}
	size, err := strconv.Atoi(rawSize)
	if err != nil {
		return nil, 0, fmt.Errorf("decode measurement size %q: %w", rawSize, err)
	}
	if size <= 0 {
		return nil, 0, fmt.Errorf("measurement window size must be greater than 0, got %d", size)
	}
	return dataSource, size, nil
}

func decodeDataObjectHashField(
	dataObjectType constants.DataObjectType,
	field string,
	rawValue string,
) (any, error) {
	if dataObjectType != constants.DataObjectTypeMeasurement {
		return rawValue, nil
	}

	switch field {
	case "mode":
		value, err := strconv.ParseInt(rawValue, 10, 16)
		if err != nil {
			return nil, fmt.Errorf("decode measurement mode %q: %w", rawValue, err)
		}
		return int16(value), nil
	case "size":
		value, err := strconv.Atoi(rawValue)
		if err != nil {
			return nil, fmt.Errorf("decode measurement size %q: %w", rawValue, err)
		}
		return value, nil
	case "data_source", "event_plan", "binding":
		return decodeRedisJSON(rawValue)
	default:
		return rawValue, nil
	}
}

func decodeParameterHashValue(rawValue, attributeType string) (any, error) {
	normalizedType := strings.ToUpper(strings.TrimSpace(attributeType))
	if rawValue == "null" {
		return nil, nil
	}

	switch {
	case normalizedType == "BOOLEAN":
		value, err := strconv.ParseBool(rawValue)
		if err != nil {
			return nil, fmt.Errorf("decode parameter boolean value %q: %w", rawValue, err)
		}
		return value, nil
	case normalizedType == "SMALLINT",
		normalizedType == "INTEGER",
		normalizedType == "BIGINT":
		value, err := strconv.ParseInt(rawValue, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("decode parameter integer value %q: %w", rawValue, err)
		}
		return value, nil
	case normalizedType == "REAL",
		normalizedType == "DOUBLE PRECISION",
		strings.HasPrefix(normalizedType, "NUMERIC"),
		strings.HasPrefix(normalizedType, "DECIMAL"):
		if _, err := strconv.ParseFloat(rawValue, 64); err != nil {
			return nil, fmt.Errorf("decode parameter numeric value %q: %w", rawValue, err)
		}
		return json.Number(rawValue), nil
	case normalizedType == "JSON",
		normalizedType == "JSONB",
		strings.HasSuffix(normalizedType, "[]"):
		return decodeRedisJSON(rawValue)
	default:
		return rawValue, nil
	}
}

func decodeRedisJSON(rawValue string) (any, error) {
	var value any
	decoder := json.NewDecoder(strings.NewReader(rawValue))
	decoder.UseNumber()
	if err := decoder.Decode(&value); err != nil {
		return nil, fmt.Errorf("decode redis JSON value: %w", err)
	}
	return value, nil
}

func isDataObjectTokenNotFound(err error) bool {
	return errors.Is(err, common.ErrParameterTokenNotFound) ||
		errors.Is(err, common.ErrMeasurementTokenNotFound)
}

func dataObjectAttributeSuccessMessage(dataObjectType constants.DataObjectType) string {
	if dataObjectType == constants.DataObjectTypeParameter {
		return "query parameter attribute success"
	}
	return "query measurement attribute success"
}

func dataObjectAttributeFailureMessage(dataObjectType constants.DataObjectType) string {
	if dataObjectType == constants.DataObjectTypeParameter {
		return "query parameter attribute failed"
	}
	return "query measurement attribute failed"
}

func queryMeasurementRealtimeValue(ctx context.Context, dataSource orm.JSONMap, size int) (any, error) {
	queryKey, err := model.GenerateMeasureIdentifier(dataSource)
	if err != nil {
		return nil, fmt.Errorf("generate measurement redis key: %w", err)
	}

	value, err := diagram.NewRedisClient().QueryLatestMeasurementValues(ctx, queryKey, size)
	if err != nil {
		return nil, fmt.Errorf("query real-time measurement value by key %q: %w", queryKey, err)
	}
	return value, nil
}