themis/absences.go

package themis

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

func (s *Store) AddAbsence(ctx context.Context, session time.Time, userId string) error {
	if session.Weekday() != time.Monday {
		return fmt.Errorf("not a monday")
	}

	tx, err := s.db.Begin()
	if err != nil {
		return fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer tx.Commit() //nolint:errcheck

	stmt, err := s.db.PrepareContext(ctx, "INSERT INTO absences (session_date, userid) VALUES (?, ?)")
	if err != nil {
		return fmt.Errorf("failed to prepare absence query: %w", err)
	}

	_, err = stmt.ExecContext(ctx, session.Format(time.DateOnly), userId)
	if err != nil {
		return fmt.Errorf("failed to insert absence: %w", err)
	}

	return nil
}

func (s *Store) GetAbsentees(ctx context.Context, session time.Time) ([]string, error) {
	tx, err := s.db.Begin()
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer tx.Commit() //nolint:errcheck

	stmt, err := s.db.PrepareContext(ctx, `SELECT userid FROM absences WHERE session_date = ?`)
	if err != nil {
		return nil, fmt.Errorf("failed to prepare query: %w", err)
	}

	rows, err := stmt.QueryContext(ctx, session.Format(time.DateOnly))
	if err != nil {
		return nil, fmt.Errorf("failed to execute query: %w", err)
	}

	absentees := make([]string, 0)
	for rows.Next() {
		var abs string
		err = rows.Scan(&abs)
		if err != nil {
			return nil, fmt.Errorf("failed to scan row: %w", err)
		}

		absentees = append(absentees, abs)
	}

	return absentees, nil
}

// map session_date -> list of absentees
type Schedule map[string][]string

func (s *Store) GetSchedule(ctx context.Context, from, to time.Time) (Schedule, error) {
	schedule := make(Schedule)
	initSchedule(schedule, from, to)

	tx, err := s.db.Begin()
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer tx.Commit() //nolint:errcheck

	stmt, err := s.db.PrepareContext(ctx, `SELECT session_date, userid FROM absences WHERE session_date BETWEEN ? AND ? ORDER BY session_date ASC`)
	if err != nil {
		return nil, fmt.Errorf("failed to prepare query: %w", err)
	}

	rows, err := stmt.QueryContext(ctx, from.Format(time.DateOnly), to.Format(time.DateOnly))
	if err != nil {
		return nil, fmt.Errorf("failed to execute query: %w", err)
	}

	for rows.Next() {
		var date string
		var user string
		err = rows.Scan(&date, &user)
		if err != nil {
			return nil, fmt.Errorf("failed to scan row: %w", err)
		}

		if _, ok := schedule[date]; ok {
			schedule[date] = append(schedule[date], user)
		} else {
			schedule[date] = []string{user}
		}
	}

	return schedule, nil
}

func initSchedule(schedule Schedule, from, to time.Time) {
	for from.Before(to) || from.Equal(to) {
		schedule[from.Format(time.DateOnly)] = []string{}
		from = from.AddDate(0, 0, 7)
	}
}