package model

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

	"modelRT/constants"
	"modelRT/diagram"
	"modelRT/logger"
	"modelRT/orm"

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

const measurementDataObjectPipelineSize = 500

type measurementDataObjectHash struct {
	Key    string
	Fields map[string]any
}

// MeasurementInitializationRecord contains a measurement and the hierarchy
// needed to create all supported Redis data-object token aliases.
type MeasurementInitializationRecord struct {
	GridTag               string      `gorm:"column:grid_tag"`
	ZoneTag               string      `gorm:"column:zone_tag"`
	StationTag            string      `gorm:"column:station_tag"`
	ComponentUUID         string      `gorm:"column:component_uuid"`
	ComponentNSPath       string      `gorm:"column:component_nspath"`
	ComponentTag          string      `gorm:"column:component_tag"`
	MeasurementID         int64       `gorm:"column:measurement_id"`
	MeasurementTag        string      `gorm:"column:measurement_tag"`
	MeasurementName       string      `gorm:"column:measurement_name"`
	MeasurementType       int16       `gorm:"column:measurement_type"`
	MeasurementMode       int16       `gorm:"column:measurement_mode"`
	MeasurementSize       int         `gorm:"column:measurement_size"`
	MeasurementDataSource orm.JSONMap `gorm:"column:measurement_data_source"`
	MeasurementEventPlan  orm.JSONMap `gorm:"column:measurement_event_plan"`
	MeasurementBinding    orm.JSONMap `gorm:"column:measurement_binding"`
}

// InitializeMeasurementDataObjects creates the seven-part, four-part, and
// token4.token7 Redis hashes for measurements loaded from PostgreSQL.
func InitializeMeasurementDataObjects(ctx context.Context, records []MeasurementInitializationRecord) error {
	hashes, err := buildMeasurementDataObjectHashes(records)
	if err != nil {
		return fmt.Errorf("build measurement data-object hashes: %w", err)
	}
	if err := storeMeasurementDataObjectHashes(ctx, diagram.GetRedisClientInstance(), hashes); err != nil {
		return fmt.Errorf("store measurement data-object hashes in redis: %w", err)
	}

	logger.Info(ctx, "initialize measurement data objects completed",
		"postgres_record_count", len(records),
		"redis_hash_count", len(hashes),
	)
	return nil
}

func buildMeasurementDataObjectHashes(records []MeasurementInitializationRecord) ([]measurementDataObjectHash, error) {
	hashes := make([]measurementDataObjectHash, 0, len(records)*3)
	seenKeys := make(map[string]string, len(records)*3)
	for _, record := range records {
		if record.MeasurementMode != constants.MeasurementModeManual &&
			record.MeasurementMode != constants.MeasurementModeAutomatic {
			return nil, fmt.Errorf(
				"measurement %q mode must be %d or %d, got %d",
				record.MeasurementTag,
				constants.MeasurementModeManual,
				constants.MeasurementModeAutomatic,
				record.MeasurementMode,
			)
		}
		if record.MeasurementSize <= 0 {
			return nil, fmt.Errorf(
				"measurement %q window size must be greater than 0, got %d",
				record.MeasurementTag,
				record.MeasurementSize,
			)
		}
		if record.MeasurementDataSource == nil ||
			record.MeasurementEventPlan == nil ||
			record.MeasurementBinding == nil {
			return nil, fmt.Errorf("measurement %q contains a null JSONB field", record.MeasurementTag)
		}

		fullToken := strings.Join([]string{
			record.GridTag,
			record.ZoneTag,
			record.StationTag,
			record.ComponentNSPath,
			record.ComponentTag,
			"bay",
			record.MeasurementTag,
		}, ".")
		fourPartToken := strings.Join([]string{
			record.ComponentNSPath,
			record.ComponentTag,
			"bay",
			record.MeasurementTag,
		}, ".")
		twoPartToken := record.ComponentNSPath + "." + record.MeasurementTag

		for _, token := range []string{fullToken, fourPartToken, twoPartToken} {
			if err := validateInitializedMeasurementToken(token); err != nil {
				return nil, err
			}
		}

		measurementType, err := MeasurementTypeString(record.MeasurementType)
		if err != nil {
			return nil, fmt.Errorf("derive type for measurement %q: %w", fullToken, err)
		}
		dataSource, err := measurementInitializationJSON(record.MeasurementDataSource)
		if err != nil {
			return nil, fmt.Errorf("encode data_source for measurement %q: %w", fullToken, err)
		}
		eventPlan, err := measurementInitializationJSON(record.MeasurementEventPlan)
		if err != nil {
			return nil, fmt.Errorf("encode event_plan for measurement %q: %w", fullToken, err)
		}
		binding, err := measurementInitializationJSON(record.MeasurementBinding)
		if err != nil {
			return nil, fmt.Errorf("encode binding for measurement %q: %w", fullToken, err)
		}

		fields := map[string]any{
			"mode":        record.MeasurementMode,
			"meta":        "MEASUREMENT",
			"type":        measurementType,
			"name":        twoPartToken,
			"description": record.MeasurementName,
			"id":          fullToken,
			"size":        record.MeasurementSize,
			"data_source": dataSource,
			"event_plan":  eventPlan,
			"binding":     binding,
		}
		owner := fmt.Sprintf("%d/%s", record.MeasurementID, record.ComponentUUID)
		for _, token := range []string{fullToken, fourPartToken, twoPartToken} {
			if err := appendMeasurementDataObjectHash(&hashes, seenKeys, token, owner, fields); err != nil {
				return nil, err
			}
		}
	}
	return hashes, nil
}

func validateInitializedMeasurementToken(token string) error {
	dataObjectType, err := ClassifyDataObjectToken(token)
	if err != nil {
		return fmt.Errorf("generated invalid measurement token %q: %w", token, err)
	}
	if dataObjectType != constants.DataObjectTypeMeasurement {
		return fmt.Errorf("generated token %q is not a measurement", token)
	}
	return nil
}

func appendMeasurementDataObjectHash(
	hashes *[]measurementDataObjectHash,
	seenKeys map[string]string,
	key string,
	owner string,
	fields map[string]any,
) error {
	if existingOwner, exists := seenKeys[key]; exists {
		return fmt.Errorf(
			"ambiguous measurement token %q is produced by %q and %q",
			key,
			existingOwner,
			owner,
		)
	}
	seenKeys[key] = owner
	*hashes = append(*hashes, measurementDataObjectHash{Key: key, Fields: fields})
	return nil
}

func measurementInitializationJSON(value orm.JSONMap) (string, error) {
	encoded, err := json.Marshal(value)
	if err != nil {
		return "", err
	}
	return string(encoded), nil
}

func storeMeasurementDataObjectHashes(
	ctx context.Context,
	rdb *redis.Client,
	hashes []measurementDataObjectHash,
) error {
	if rdb == nil {
		return fmt.Errorf("redis client is nil")
	}

	oldKeys, err := rdb.SMembers(ctx, constants.RedisMeasurementDataObjectKeySet).Result()
	if err != nil {
		return fmt.Errorf("query previously initialized measurement keys: %w", err)
	}
	currentKeys := make(map[string]struct{}, len(hashes))
	for start := 0; start < len(hashes); start += measurementDataObjectPipelineSize {
		end := min(start+measurementDataObjectPipelineSize, len(hashes))
		pipeline := rdb.TxPipeline()
		keyMembers := make([]any, 0, end-start)
		for _, hash := range hashes[start:end] {
			pipeline.Del(ctx, hash.Key)
			pipeline.HSet(ctx, hash.Key, hash.Fields)
			keyMembers = append(keyMembers, hash.Key)
			currentKeys[hash.Key] = struct{}{}
		}
		if len(keyMembers) > 0 {
			pipeline.SAdd(ctx, constants.RedisMeasurementDataObjectKeySet, keyMembers...)
		}
		if _, err := pipeline.Exec(ctx); err != nil {
			return fmt.Errorf("write measurement data-object hash batch starting at %d: %w", start, err)
		}
	}

	staleKeys := make([]string, 0)
	for _, key := range oldKeys {
		if _, exists := currentKeys[key]; !exists {
			staleKeys = append(staleKeys, key)
		}
	}
	cleanupPipeline := rdb.TxPipeline()
	for start := 0; start < len(staleKeys); start += measurementDataObjectPipelineSize {
		end := min(start+measurementDataObjectPipelineSize, len(staleKeys))
		cleanupPipeline.Del(ctx, staleKeys[start:end]...)
		members := make([]any, 0, end-start)
		for _, key := range staleKeys[start:end] {
			members = append(members, key)
		}
		cleanupPipeline.SRem(ctx, constants.RedisMeasurementDataObjectKeySet, members...)
	}
	if len(hashes) == 0 {
		cleanupPipeline.Del(ctx, constants.RedisMeasurementDataObjectKeySet)
	}
	if _, err := cleanupPipeline.Exec(ctx); err != nil {
		return fmt.Errorf("remove stale measurement data-object hashes: %w", err)
	}
	return nil
}