package db

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

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

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

func init() {
	sql.Register("custom_sqlite3", &sqlite3.SQLiteDriver{
		// TODO: add helper that convert between unix milliseconds and sqlite times?
	})
}

type TelemDb struct {
	db *sqlx.DB
}

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

func OpenTelemDb(path string, options ...TelemDbOption) (tdb *TelemDb, err error) {
	tdb = &TelemDb{}
	tdb.db, err = sqlx.Connect("sqlite3", path)
	if err != nil {
		return
	}
	// TODO: add options support.

	for _, fn := range options {
		err = fn(tdb)
		if err != nil {
			return
		}
	}

	var version int
	err = tdb.db.Get(&version, "PRAGMA user_version")
	if err != nil {
		return
	}

	// get latest version of migrations - then run the SQL in order to perform them
	fmt.Printf("starting version %d\n", version)

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

	return tdb, err
}

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) {
	//
	n = 0
	tx, err := tdb.db.BeginTx(ctx, nil)
	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)
	if err != nil {
		tx.Rollback()
		return
	}
	res, err := stmt.ExecContext(ctx, vals...)
	if err != nil {
		tx.Rollback()
		return
	}
	n, err = res.RowsAffected()

	tx.Commit()
	return
}

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

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

// Streaming logger.
func (tdb *TelemDb) AddEventStreamCtx(ctx context.Context, events <-chan skylab.BusEvent, done chan<- bool) error {
	const BatchSize = 500

	tx, err := tdb.db.BeginTx(ctx, nil)
	defer tx.Commit()
	if err != nil {
		return err
	}

	makePreparedStmt := func(ctx context.Context, tx *sql.Tx, n int) (*sql.Stmt, error) {
		sqlStmt := sqlInsertEvent
		const rowSql = "(?, ?, json(?))"
		inserts := make([]string, n)
		for i := 0; i < n; i++ {
			inserts[n] = rowSql
		}
		sqlStmt = sqlStmt + strings.Join(inserts, ",")
		return tx.PrepareContext(ctx, sqlStmt)
	}

	bulkStmt, err := makePreparedStmt(ctx, tx, BatchSize)

	// this is the list of values that we use.
	valBatch := make([]interface{}, 0, BatchSize*3)
	batchIdx := 0
	for {
		e, more := <-events
		if more {
			j, err := json.Marshal(e.Data)
			if err != nil {
				continue // skip things that couldn't be marshalled
			}
			valBatch = append(valBatch, e.Timestamp.UnixMilli(), e.Data.String(), j)
			batchIdx++
			if batchIdx >= BatchSize {
				_, err := bulkStmt.ExecContext(ctx, valBatch...)
				if err != nil {
					continue
				}
			}
		} else {
			break
		}

	}
	// create a statement for the remaining items.
	lastStmt, err := makePreparedStmt(ctx, tx, batchIdx)
	if err != nil {
		return nil
	}
	_, err = lastStmt.ExecContext(ctx, valBatch...)
	done <- true

	return nil
}

/// Query fragment guide:
/// We need to be able to easily construct safe(!) and meaningful queries programatically
/// so we make some new types that can be turned into SQL fragments that go inside the where clause.
/// These all implement the QueryFrag interface, meaning the actual query function (that acts on the DB)
/// can deal with them agnostically. The Query function joins all the fragments it is given with AND.
/// to get OR,

// QueryFrag is anything that can be turned into a Query WHERE clause
type QueryFrag interface {
	Query() string
}

// QueryTimeRange represents a query of a specific time range. For "before" or "after" queries,
// use time.Unix(0,0) or time.Now() in start and end respectively.
type QueryTimeRange struct {
	Start time.Time
	End   time.Time
}

func (q *QueryTimeRange) Query() string {
	startUnix := q.Start.UnixMilli()
	endUnix := q.End.UnixMilli()

	return fmt.Sprintf("ts BETWEEN %d AND %d", startUnix, endUnix)
}

type QueryNames []string

func (q QueryNames) Query() string {
	return fmt.Sprintf("name IN (%s)", strings.Join(q, ", "))
}

type QueryOr []QueryFrag

func (q QueryOr) Query() string {
	var qStrings []string
	for _, frag := range q {
		qStrings = append(qStrings, frag.Query())
	}
	return fmt.Sprintf("(%s)", strings.Join(qStrings, " OR "))
}

// GetEvents is the mechanism to request underlying event data.
// it takes functions (which are defined in db.go) that modify the query,
// and then return the results.
func (tdb *TelemDb) GetEvents(limit int, where ...QueryFrag) (events []skylab.BusEvent, err error) {
	// Simple mechanism for combining query frags:
	// join with " AND ". To join expressions with or, use QueryOr
	var fragStr []string
	for _, f := range where {
		fragStr = append(fragStr, f.Query())
	}
	qString := fmt.Sprintf(`SELECT * FROM "bus_events" WHERE %s LIMIT %d`, strings.Join(fragStr, " AND "), limit)
	rows, err := tdb.db.Queryx(qString)
	if err != nil {
		return
	}
	defer rows.Close()

	if limit < 0 { //  special case: limit negative means unrestricted.
		events = make([]skylab.BusEvent, 0, 20)
	} else {
		events = make([]skylab.BusEvent, 0, limit)
	}
	// scan rows into busevent list...
	for rows.Next() {
		var ev skylab.RawJsonEvent
		err = rows.StructScan(&ev)
		if err != nil {
			return
		}

		BusEv := skylab.BusEvent{
			Timestamp: time.UnixMilli(int64(ev.Timestamp)),
			Name:      ev.Name,
		}
		BusEv.Data, err = skylab.FromJson(ev.Name, ev.Data)

		// FIXME: this is slow!
		events = append(events, BusEv)

	}

	err = rows.Err()

	return
}

// 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) {

}