db.go

package main

import (
	"context"
	"database/sql"
	_ "embed"
	"errors"
	"fmt"
	"time"

	_ "github.com/jackc/pgx/v5/stdlib"
)

var (
	//go:embed sql/schema.sql
	schemaSQL string

	//go:embed sql/add.sql
	addSQL string

	//go:embed sql/last.sql
	lastSQL string
)

type Entry struct {
	Time    time.Time
	Login   string
	Content string
}

var zeroTime time.Time

func (e Entry) Validate() error {
	if e.Time.Equal(zeroTime) {
		return fmt.Errorf("missing time")
	}

	if e.Login == "" {
		return fmt.Errorf("missing login")
	}

	if e.Content == "" {
		return fmt.Errorf("missing content")
	}

	return nil
}

type DB struct {
	conn *sql.DB
}

func NewDB(ctx context.Context, dsn string) (*DB, error) {
	conn, err := sql.Open("pgx", dsn)
	if err != nil {
		return nil, err
	}

	if _, err := conn.Exec(schemaSQL); err != nil {
		conn.Close()
		return nil, err
	}

	return &DB{conn}, nil
}

func (d *DB) Add(ctx context.Context, e Entry) error {
	_, err := d.conn.Exec(addSQL, e.Time, e.Login, e.Content)
	if err != nil {
		return err
	}

	return nil
}

var ErrNotFound = errors.New("not found")

func (d *DB) Last(ctx context.Context) (Entry, error) {
	row := d.conn.QueryRow(lastSQL)
	var e Entry
	if err := row.Scan(&e.Time, &e.Login, &e.Content); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			err = ErrNotFound
		}
		return Entry{}, err
	}

	return e, nil
}

func (d *DB) Health(ctx context.Context) error {
	return d.conn.Ping()
}

func (d *DB) Close() error {
	return d.conn.Close()
}