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// file: repositories/movie_repository.go
package repositories
import (
"errors"
"sync"
"github.com/kataras/iris/_examples/hero/overview/datamodels"
)
// Query represents the visitor and action queries.
type Query func(datamodels.Movie) bool
// MovieRepository handles the basic operations of a movie entity/model.
// It's an interface in order to be testable, i.e a memory movie repository or
// a connected to an sql database.
type MovieRepository interface {
Exec(query Query, action Query, limit int, mode int) (ok bool)
Select(query Query) (movie datamodels.Movie, found bool)
SelectMany(query Query, limit int) (results []datamodels.Movie)
InsertOrUpdate(movie datamodels.Movie) (updatedMovie datamodels.Movie, err error)
Delete(query Query, limit int) (deleted bool)
}
// NewMovieRepository returns a new movie memory-based repository,
// the one and only repository type in our example.
func NewMovieRepository(source map[int64]datamodels.Movie) MovieRepository {
return &movieMemoryRepository{source: source}
}
// movieMemoryRepository is a "MovieRepository"
// which manages the movies using the memory data source (map).
type movieMemoryRepository struct {
source map[int64]datamodels.Movie
mu sync.RWMutex
}
const (
// ReadOnlyMode will RLock(read) the data .
ReadOnlyMode = iota
// ReadWriteMode will Lock(read/write) the data.
ReadWriteMode
)
func (r *movieMemoryRepository) Exec(query Query, action Query, actionLimit int, mode int) (ok bool) {
loops := 0
if mode == ReadOnlyMode {
r.mu.RLock()
defer r.mu.RUnlock()
} else {
r.mu.Lock()
defer r.mu.Unlock()
}
for _, movie := range r.source {
ok = query(movie)
if ok {
if action(movie) {
loops++
if actionLimit >= loops {
break // break
}
}
}
}
return
}
// Select receives a query function
// which is fired for every single movie model inside
// our imaginary data source.
// When that function returns true then it stops the iteration.
//
// It returns the query's return last known "found" value
// and the last known movie model
// to help callers to reduce the LOC.
//
// It's actually a simple but very clever prototype function
// I'm using everywhere since I firstly think of it,
// hope you'll find it very useful as well.
func (r *movieMemoryRepository) Select(query Query) (movie datamodels.Movie, found bool) {
found = r.Exec(query, func(m datamodels.Movie) bool {
movie = m
return true
}, 1, ReadOnlyMode)
// set an empty datamodels.Movie if not found at all.
if !found {
movie = datamodels.Movie{}
}
return
}
// SelectMany same as Select but returns one or more datamodels.Movie as a slice.
// If limit <=0 then it returns everything.
func (r *movieMemoryRepository) SelectMany(query Query, limit int) (results []datamodels.Movie) {
r.Exec(query, func(m datamodels.Movie) bool {
results = append(results, m)
return true
}, limit, ReadOnlyMode)
return
}
// InsertOrUpdate adds or updates a movie to the (memory) storage.
//
// Returns the new movie and an error if any.
func (r *movieMemoryRepository) InsertOrUpdate(movie datamodels.Movie) (datamodels.Movie, error) {
id := movie.ID
if id == 0 { // Create new action
var lastID int64
// find the biggest ID in order to not have duplications
// in productions apps you can use a third-party
// library to generate a UUID as string.
r.mu.RLock()
for _, item := range r.source {
if item.ID > lastID {
lastID = item.ID
}
}
r.mu.RUnlock()
id = lastID + 1
movie.ID = id
// map-specific thing
r.mu.Lock()
r.source[id] = movie
r.mu.Unlock()
return movie, nil
}
// Update action based on the movie.ID,
// here we will allow updating the poster and genre if not empty.
// Alternatively we could do pure replace instead:
// r.source[id] = movie
// and comment the code below;
current, exists := r.Select(func(m datamodels.Movie) bool {
return m.ID == id
})
if !exists { // ID is not a real one, return an error.
return datamodels.Movie{}, errors.New("failed to update a nonexistent movie")
}
// or comment these and r.source[id] = m for pure replace
if movie.Poster != "" {
current.Poster = movie.Poster
}
if movie.Genre != "" {
current.Genre = movie.Genre
}
// map-specific thing
r.mu.Lock()
r.source[id] = current
r.mu.Unlock()
return movie, nil
}
func (r *movieMemoryRepository) Delete(query Query, limit int) bool {
return r.Exec(query, func(m datamodels.Movie) bool {
delete(r.source, m.ID)
return true
}, limit, ReadWriteMode)
}
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