github.com/mssola/todo@v0.0.0-20181029153210-d25348dc3f48/app/topics_api.go

// Copyright (C) 2014-2017 Miquel Sabaté Solà <mikisabate@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package app

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"

	"github.com/gorilla/mux"
	"github.com/mssola/todo/lib"
)

// The parameters that be given through a request body.
type params struct {
	Name     string
	Contents string
}

// Get the possible parameters from the given request. Note that it will only
// check for the "name" and "contents" parameters.
func getFromBody(req *http.Request) *params {
	var p params

	if req.Body == nil {
		return nil
	}

	decoder := json.NewDecoder(req.Body)
	if err := decoder.Decode(&p); err != nil {
		return nil
	}
	return &p
}

// Safely render and send a JSON response with the given topic. This function
// should be called after performing some operation that might return an error.
// This error from the previous operation is the third parameter. The fourth
// parameter tells this function to generate the Markdown code for this topic.
func renderJSON(res http.ResponseWriter, topic *Topic, err error, md bool) {
	// Try to render the given Topic.
	if err == nil {
		if md {
			topic.RenderMarkdown()
		}
		if b, err := json.Marshal(topic); err == nil {
			fmt.Fprint(res, string(b))
			res.Header().Set("Content-Type", "application/json")
			return
		}
	}

	// Render a generic error.
	lib.JSONError(res)
}

// TopicsIndexJSON responds to: GET /topics. This will only be called when the
// user requested a JSON response.
func TopicsIndexJSON(res http.ResponseWriter, req *http.Request) {
	var topics []Topic
	if _, err := Db.Select(&topics, "select * from topics"); err != nil {
		log.Printf("Could not fetch topics: %v", err)
	}
	b, _ := json.Marshal(topics)
	res.Header().Set("Content-Type", "application/json")
	fmt.Fprint(res, string(b))
}

// TopicsCreateJSON responds to: POST /topics. This will only be called when
// the user requested a JSON response.
func TopicsCreateJSON(res http.ResponseWriter, req *http.Request) {
	if p := getFromBody(req); p == nil {
		lib.JSONError(res)
	} else {
		t, err := createTopic(p.Name)
		renderJSON(res, t, err, false)
	}
}

// TopicsShowJSON responds to: GET /topics/:id. This will only be called when
// the user requested a JSON response.
func TopicsShowJSON(res http.ResponseWriter, req *http.Request) {
	var t Topic
	p := mux.Vars(req)
	err := Db.SelectOne(&t, "select * from topics where id=$1", p["id"])
	renderJSON(res, &t, err, true)
}

// TopicsUpdateJSON responds to: PUT/PATCH /topics/:id. This will only be
// called when the user requested a JSON response.
func TopicsUpdateJSON(res http.ResponseWriter, req *http.Request) {
	var str, value string
	var p *params

	if p = getFromBody(req); p == nil {
		lib.JSONError(res)
		return
	}

	// Execute the update query. Depending on the given parameters this will be
	// just a plain rename, or a full update.
	if value = p.Name; value == "" {
		str = "contents"
		if value = p.Contents; value == "" {
			lib.JSONError(res)
			return
		}
	} else {
		str = "name"
	}

	// And finally send the JSON response.
	var t Topic
	str = fmt.Sprintf("update topics set %v=$1 where id=$2 returning *", str)
	err := Db.SelectOne(&t, str, value, mux.Vars(req)["id"])
	renderJSON(res, &t, err, true)
}

// TopicsDestroyJSON responds to: PUT/PATCH /topics/:id. This will only be
// called when the user requested a JSON response.
func TopicsDestroyJSON(res http.ResponseWriter, req *http.Request) {
	p := mux.Vars(req)
	results, err := Db.Exec("delete from topics where id=$1", p["id"])

	res.Header().Set("Content-Type", "application/json")
	if err != nil {
		fmt.Fprint(res, lib.Response{Error: "Could not remove topic"})
	} else if count, _ := results.RowsAffected(); count == 0 {
		fmt.Fprint(res, lib.Response{Error: "Could not remove topic"})
	} else {
		fmt.Fprint(res, lib.Response{Message: "Ok"})
	}
}