main.go

package main

import (
	"net/http"
	"strconv"

	"github.com/gin-gonic/gin"
)

// album represents data about a record album.
type album struct {
	ID     string  `json:"id"`
	Title  string  `json:"title"`
	Artist string  `json:"artist"`
	Price  float64 `json:"price"`
}

// albums slice to seed record album data.
var albums = []album{
	{ID: "1", Title: "Blue Train", Artist: "John Coltrane", Price: 56.99},
	{ID: "2", Title: "Jeru", Artist: "Gerry Mulligan", Price: 17.99},
	{ID: "3", Title: "Sarah Vaughan and Clifford Brown", Artist: "Sarah Vaughan", Price: 39.99},
}

func main() {
	router := gin.Default()
	router.GET("/", func(context *gin.Context) {
		context.IndentedJSON(http.StatusOK, "Hello")
	})
	router.GET("/albums", func(c *gin.Context) {
		if c.Query("maxPrice") != "" {
			getAlbumsMaxPrice(c)
		} else {
			getAlbums(c)
		}
	})
	router.GET("/albums/:id", getAlbumByID)
	router.POST("/albums", postAlbums)

	err := router.Run(":8080")
	if err != nil {
		println("Unable to start router.")
		return
	}
}

// getAlbums responds with the list of all albums as JSON.
func getAlbums(c *gin.Context) {
	c.IndentedJSON(http.StatusOK, albums)
}

// postAlbums adds an album from JSON received in the request body.
func postAlbums(c *gin.Context) {
	var newAlbum album

	// Call BindJSON to bind the received JSON to newAlbum.
	if err := c.BindJSON(&newAlbum); err != nil {
		return
	}

	albums = append(albums, newAlbum)
	c.IndentedJSON(http.StatusCreated, newAlbum)
}

// getAlbumByID locates the album whose ID value matches the id
// parameter sent by the client, then returns that album as a response.
func getAlbumByID(c *gin.Context) {
	id := c.Param("id")

	// Loop over the list of albums, looking for
	// an album whose ID value matches the parameter.
	for _, a := range albums {
		if a.ID == id {
			c.IndentedJSON(http.StatusOK, a)
			return
		}
	}
	c.IndentedJSON(http.StatusNotFound, gin.H{"message": "album not found"})
}

// getAlbumsMaxPrice responds with the list of all albums with a price less than or equal to than the given param as JSON.
func getAlbumsMaxPrice(c *gin.Context) {
	maxPrice, err := strconv.ParseFloat(c.Query("maxPrice"), 64)
	if err != nil {
		c.IndentedJSON(http.StatusBadRequest, gin.H{"message": "query must be a number"})
	}

	var matches []album

	// Loop over the list of albums, looking for
	// albums whose price value is less than the parameter.
	for _, a := range albums {
		if a.Price <= maxPrice {
			matches = append(matches, a)
		}
	}

	if len(matches) > 0 {
		c.IndentedJSON(http.StatusOK, matches)
	} else {
		c.IndentedJSON(http.StatusNotFound, gin.H{"message": "no matches found"})
	}
}