gotelem/internal/db/getters.go

package db

import (
	"context"
	"fmt"
	"strings"
	"time"
)

// Modifier augments SQL strings.
type Modifier interface {
	ModifyStatement(string) string
}


type LimitOffsetModifier struct {
	Limit int
	Offset int
}

// BusEventFilter is a filter for bus events.
type BusEventFilter struct {
	Names []string
	TimerangeStart time.Time
	TimerangeEnd time.Time
}

func (bef *BusEventFilter) String() string {
	var sb []string = make([]string, 0, 2)
	if len(bef.Names) > 0 {
		names := strings.Join(bef.Names, ",")
		sb = append(sb, fmt.Sprintf("name IN (%s)", names))
	}
	if !bef.TimerangeStart.IsZero() && !bef.TimerangeEnd.IsZero() {
		sb = append(sb, fmt.Sprintf(""))
	}
	return ""
}

type BusEventElement interface {
	Element() string
}

type NormalExtract struct {
	Key string
}

type JSONExtract struct {
	Key string
}

type BusEventQuery struct {
	Elements []BusEventElement
	Filter BusEventFilter
	Limits LimitOffsetModifier
}

func (beq *BusEventQuery) String() string {
	// select
	return ""
}


// now we can optionally add a limit.

// Datum is a single measurement - it is more granular than a packet.
// the classic example is bms_measurement.current
type Datum struct {
	Timestamp time.Time `db:"timestamp"`
	Value     any       `db:"val"`
}

// GetValues queries the database for values in a given time range.
// A value is a specific data point. For example, bms_measurement.current
// would be a value.
func (tdb *TelemDb) GetValues(ctx context.Context, packetName, field string, start time.Time,
	end time.Time) ([]Datum, error) {
	// this fragment uses json_extract from sqlite to get a single
	// nested value.
	SqlFrag := `
	SELECT 
	ts as timestamp,
	json_extract(data, '$.' || ?) as val
	FROM bus_events WHERE name IS ? 
	`
	rows, err := tdb.db.QueryxContext(ctx, SqlFrag, field, packetName)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	data := make([]Datum, 0, 10)
	for rows.Next() {
		var d Datum = Datum{}
		err = rows.StructScan(&d)
		if err != nil {
			fmt.Print(err)
			return data, err
		}
		data = append(data, d)
	}
	fmt.Print(rows.Err())

	return data, nil
}