greenlight/internal/data/movies.go

package data

import (
	"database/sql"
	"errors"
	"github.com/lib/pq"
	"time"

	"greenlight.craftr.fr/internal/validator"
)

// Movie
/*
	Annotate the Movie struct with struct tags to control how the keys
	appear in the JSON-encoded output.
*/
type Movie struct {
	ID        int64     `json:"id"`
	CreatedAt time.Time `json:"-"`
	Title     string    `json:"title"`
	Year      int32     `json:"year,omitempty"`
	/*
		Use the Runtime type instead of int32. Note that the omitempty directive will still work on this: if the Runtime field has the underlying value 0, then it will be considered empty and omitted -- and the MarshalJSON() method we just made won't be called at all.
	*/
	Runtime Runtime  `json:"runtime,omitempty"`
	Genres  []string `json:"genres,omitempty"`
	Version int32    `json:"version"`
}

func ValidateMovie(v *validator.Validator, movie *Movie) {
	// Use the Check() method to execute our validation checks. This will add the provided key and error message to the errors maps if the check does not evaluate to true. For example, in the first line we "check that the title is not equal to an empty string".
	v.Check(movie.Title != "", "title", "must be provided")
	v.Check(len(movie.Title) <= 500, "title", "must not be more than 500 bytes long")

	v.Check(movie.Year != 0, "year", "must be provided")
	v.Check(movie.Year >= 1888, "year", "must be greater than 1888")
	v.Check(movie.Year <= int32(time.Now().Year()), "year", "must not be in the future")

	v.Check(movie.Runtime != 0, "runtime", "must be provided")
	v.Check(movie.Runtime > 0, "runtime", "must be a positive integer")

	v.Check(movie.Genres != nil, "genres", "must be provided")
	v.Check(len(movie.Genres) >= 1, "genres", "must contain at least 1 genre")
	v.Check(len(movie.Genres) <= 5, "genres", "must not contain more than 5 genres")
	// Not that we're using the Unique helper in the line below to check that all values in the input.Genres slice are unique
	v.Check(validator.Unique(movie.Genres), "genres", "must not contain duplicate values")
}

// MovieModel struct type wraps a sql.DB connection pool
type MovieModel struct {
	DB *sql.DB
}

// Insert : Inserting a new record in the movies table
func (m MovieModel) Insert(movie *Movie) error {
	// Define the SQL query for inserting a new record in the movies table and returning the system-generated data.
	query := `
		INSERT INTO movies (title, year, runtime, genres)
		VALUES ($1, $2, $3, $4)
		RETURNING id, created_at, version`

	// Create an args slice containing the values for the placeholder parameters from the movie struct. Declaring this slice immediately next to our SQL query helps to make it nice and clear *what values are being used where* in the query
	args := []any{movie.Title, movie.Year, movie.Runtime, pq.Array(movie.Genres)}

	// Use the QueryRow() method to execute the SQL query on our connection pool, passing in the args slice as a variadic parameter and scanning the system-generated id, created_at and version values into the movie struct.
	return m.DB.QueryRow(query, args...).Scan(&movie.ID, &movie.CreatedAt, &movie.Version)
}

// Get : Fetching a specific record from the movies table
func (m MovieModel) Get(id int64) (*Movie, error) {
	// The PostgreSQL bigserial type that we're using for the movie ID starts auto-incrementing at 1 by default, so we know that no movies will have ID values less than that. To avoid making an unnecessary database call, we take a shortcut and return an ErrRecordNotFound error straight away.
	if id < 1 {
		return nil, ErrRecordNotFound
	}

	// Define the SQL query for retrieving the movie data.
	query := `
		SELECT id, created_at, title, year, runtime, genres, version
		FROM movies
		WHERE id = $1`

	// Declare a Movie struct to hold the data returned by the query
	var movie Movie

	// Execute the query using the QueryRow() method, passing in the provided id value as a placeholder parameter, and scan the response data into the fields of the Movie struct. Importantly, notice that we need to convert the scan target for the genres column using the pq.Array() adapter function again.
	err := m.DB.QueryRow(query, id).Scan(
		&movie.ID,
		&movie.CreatedAt,
		&movie.Title,
		&movie.Year,
		&movie.Runtime,
		pq.Array(&movie.Genres),
		&movie.Version,
	)

	// Handle any errors. If there was no matching movie found. Scan() will return a sql.ErrNoRows error. We check for this and return our custom ErrRecordNotFound error instead.
	if err != nil {
		switch {
		case errors.Is(err, sql.ErrNoRows):
			return nil, ErrRecordNotFound
		default:
			return nil, err
		}
	}

	// Otherwise, return a pointer to the Movie struct.
	return &movie, nil
}

// Update : Updating a specific record in the movies table
func (m MovieModel) Update(movie *Movie) error {
	// Declare the SQL query for updating the record and returning the new version number.
	query := `
		UPDATE movies
		SET title = $1, year = $2, runtime = $3, genres = $4, version = version +1
		WHERE id = $5
		RETURNING version`

	// Create an args slice containing the values for the placeholder parameters.
	args := []any{
		movie.Title,
		movie.Year,
		movie.Runtime,
		pq.Array(movie.Genres),
		movie.ID,
	}

	// Use the QueryRow() method to execute the query, passing in the args slice as a variadic parameter and scanning the new version value into the movie struct.
	return m.DB.QueryRow(query, args...).Scan(&movie.Version)
}

// Delete : Deleting a specific record from the movies table
func (m MovieModel) Delete(id int64) error {
	return nil
}