package tasks

import (
	"context"
	"fmt"
	"time"

	"atlas9.dev/c/core/dbi"
)

// SqliteScheduleStore implements ScheduleStore over a SQLite table. Every
// schedule table shares the same coordination columns: an id primary key, plus
// schedule, next_run_at, and last_run_at.
type SqliteScheduleStore struct {
	db    dbi.DBI
	table string
}

func NewSqliteScheduleStore(db dbi.DBI, table string) *SqliteScheduleStore {
	return &SqliteScheduleStore{db: db, table: table}
}

func (s *SqliteScheduleStore) Due(ctx context.Context) ([]Due, error) {

	rows, err := s.db.Query(ctx,
		"SELECT id, schedule FROM "+s.table+" WHERE next_run_at <= datetime('now')")
	if err != nil {
		return nil, fmt.Errorf("querying due schedules: %w", err)
	}
	defer rows.Close()

	var dues []Due
	for rows.Next() {
		var d Due
		if err := rows.Scan(&d.ID, &d.Schedule); err != nil {
			return nil, fmt.Errorf("scanning due schedule: %w", err)
		}
		dues = append(dues, d)
	}
	return dues, rows.Err()
}

func (s *SqliteScheduleStore) Claim(ctx context.Context, id string, next time.Time) (bool, error) {

	res, err := s.db.Exec(ctx,
		"UPDATE "+s.table+" SET last_run_at = datetime('now'), next_run_at = $1"+
			" WHERE id = $2 AND next_run_at <= datetime('now')",
		next.UTC().Format(sqliteTimeFormat), id)
	if err != nil {
		return false, fmt.Errorf("claiming schedule: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return false, fmt.Errorf("checking rows affected: %w", err)
	}
	return n > 0, nil
}