package db

// this file implements the database functions to load/store/read from a sql database.

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

	"github.com/jmoiron/sqlx"
	"github.com/kschamplin/gotelem/skylab"
	_ "github.com/mattn/go-sqlite3"
)


type TelemDb struct {
	db *sqlx.DB
}

// TelemDbOption lets you customize the behavior of the sqlite database
type TelemDbOption func(*TelemDb) error


// this function is internal use. It actually opens the database, but uses
// a raw path string instead of formatting one like the exported functions.
func OpenRawDb(rawpath string, options ...TelemDbOption) (tdb *TelemDb, err error) {
	tdb = &TelemDb{}
	tdb.db, err = sqlx.Connect("sqlite3", rawpath)
	if err != nil {
		return
	}
	for _, fn := range options {
		err = fn(tdb)
		if err != nil {
			return
		}
	}

	// perform any database migrations
	version, err := tdb.GetVersion()
	if err != nil {
		return
	}
	// TODO: use logging instead of printf
	fmt.Printf("starting version %d\n", version)

	version, err = RunMigrations(tdb)
	fmt.Printf("ending version %d\n", version)

	return tdb, err
}


// this string is used to open the read-write db.
// the extra options improve performance significantly.
const ProductionDbURI = "file:%s?_journal_mode=wal&mode=rwc&_txlock=immediate&_timeout=10000"

// OpenTelemDb opens a new telemetry database at the given path.
func OpenTelemDb(path string, options ...TelemDbOption) (*TelemDb, error) {
	dbStr := fmt.Sprintf(ProductionDbURI, path)
	return OpenRawDb(dbStr, options...)
}

func (tdb *TelemDb) GetVersion() (int, error) {
	var version int
	err := tdb.db.Get(&version, "PRAGMA user_version")
	return version, err
}

func (tdb *TelemDb) SetVersion(version int) error {
	stmt := fmt.Sprintf("PRAGMA user_version = %d", version)
	_, err := tdb.db.Exec(stmt)
	return err
}

// sql expression to insert a bus event into the packets database.1
const sqlInsertEvent =`INSERT INTO "bus_events" (ts, name, data) VALUES `

// AddEvent adds the bus event to the database.
func (tdb *TelemDb) AddEventsCtx(ctx context.Context, events ...skylab.BusEvent) (n int64, err error) {
	// edge case - zero events.
	if len(events) == 0 {
		return 0, nil
	}
	n = 0
	tx, err := tdb.db.BeginTx(ctx, nil)
	defer tx.Rollback()
	if err != nil {
		return
	}

	sqlStmt := sqlInsertEvent
	const rowSql = "(?, ?, json(?))"
	inserts := make([]string, len(events))
	vals := []interface{}{}
	idx := 0 // we have to manually increment, because sometimes we don't insert.
	for _, b := range events {
		inserts[idx] = rowSql
		var j []byte
		j, err = json.Marshal(b.Data)

		if err != nil {
			// we had some error turning the packet into json.
			continue // we silently skip.
		}

		vals = append(vals, b.Timestamp.UnixMilli(), b.Data.String(), j)
		idx++
	}

	// construct the full statement now
	sqlStmt = sqlStmt + strings.Join(inserts[:idx], ",")
	stmt, err := tx.PrepareContext(ctx, sqlStmt)
	// defer stmt.Close()
	if err != nil {
		return
	}
	res, err := stmt.ExecContext(ctx, vals...)
	if err != nil {
		return
	}
	n, err = res.RowsAffected()

	tx.Commit()
	return
}

func (tdb *TelemDb) AddEvents(events ...skylab.BusEvent) (int64, error) {

	return tdb.AddEventsCtx(context.Background(), events...)
}


// GetActiveDrive finds the non-null drive and returns it, if any.
func (tdb *TelemDb) GetActiveDrive() (res int, err error) {
	err = tdb.db.Get(&res, "SELECT id FROM drive_records WHERE end_time IS NULL LIMIT 1")
	return
}

func (tdb *TelemDb) NewDrive(start time.Time, note string) {

}

func (tdb *TelemDb) EndDrive() {

}

func (tdb *TelemDb) UpdateDrive(id int, note string) {

}