main.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/pennz/DataViz/viz"
)

func setupRouter() *gin.Engine {
	r := gin.Default()
	r.Use(gin.Logger())
	r.GET("/ping", func(c *gin.Context) {
		c.String(200, "pong")
	})
	r.Static("/Viz", "GraphVizOnline")
	r.POST("/compile", compileHandler)
	r.POST("/compile_debug", compileHandler_debug)

	//r.LoadHTMLGlob("GraphVizOnline/*.html")
	//r.GET("/", func(c *gin.Context) {
	//	c.HTML(http.StatusOK, "index.html", nil)
	//})
	return r
}

func main() {
	r := setupRouter()
	port := os.Getenv("PORT")

	if port == "" {
		log.Fatal("$PORT must be set")
	}
	r.Run(":" + port)
}

func readCloser2String(rc io.ReadCloser) string {
	buf := new(bytes.Buffer)
	buf.ReadFrom(rc)
	newStr := buf.String()
	return newStr
}

// runGoAsync(goSRCcode).then((d) => {
//     if (d.Events == null) {
//         show_status("compiling failed: " + d.Errors, 5500);
//     }
//     for (let i = d.Events.length - 1; i >= 1; i--) { // reverse
//         setGraphSteps(d.Events[i].Message, goSRCcode);
//     }
//     let ss0 = splitGraph(d.Events[0].Message)
//     graphSRC.setValue(ss0[0]);
//     for (let i = ss0.length; i >= 0; i--) { // reverse
//         let s = ss0[i];
//         updateStateHistory(
//             encodeURIComponent(s),
//             encodeURIComponent(goSRCcode));
//     }
// });
// {"Errors":"","Events":[{"Message":"digraph graphname
// {\n\tbgcolor=white\n\tsubgraph cluster_0 {style=filled color=lightgrey
// node [style=filled color=white shape=\"Msquare\"] -1 0 1 -2
// 3}\n}\ndigraph graphname {\n\tbgcolor=white\n\tsubgraph cluster_0
// {style=filled color=lightgrey node [style=filled color=white
// shape=\"Msquare\"] -1 0 1 -2 3 4}\n}\ndigraph graphname
// {\n\tbgcolor=white\n\tsubgraph cluster_0 {style=filled color=lightgrey
// node [style=filled color=white shape=\"Msquare\"] -1 0 1 -2
// 3 4 5}\n}\ndigraph graphname {\n\tbgcolor=white\n\tsubgraph cluster_0
// {style=filled color=lightgrey node [style=filled color=white
// shape=\"Msquare\"] -1 [color=red style=filled fillcolor=red]
// 0 [color=blue style=filled fillcolor=blue] 1 -2 3 4 5}\n}\ndigraph
// graphname {\n\tbgcolor=white\n\tsubgraph cluster_0 {style=filled
// color=lightgrey node [style=filled color=white shape=\"Msquare\"]
// 0 [color=red style=filled fillcolor=red] -1 [color=blue style=filled
// fillcolor=blue] 1 -2
// 3 4 5}\n}\n","Kind":"stdout","Delay":0}],"Status":0,"IsTest":false,"TestsFailed":0,"VetOK":true}]}}]}}]}}
type RunResult struct {
	Errors      string
	Events      []Event
	Status      int
	IsTest      bool
	TestsFailed int
	VetOK       bool
}
type Event struct {
	Message string
	Kind    string
	Delay   int
}

func splitDotGraph(multiGraph string) []string {

	//var splitGraph = function (s) {
	//  let ss = s.split("digraph");
	//  for (let i = 0; i < ss.length; i++) {
	//    if (ss[i].trim() == "") {
	//      ss.splice(i, 1);
	//    }
	//  }
	//  for (let i = 0; i < ss.length; i++) {
	//    ss[i] = "digraph" + ss[i];
	//  }
	//  return ss;
	//};
	ss := strings.Split(multiGraph, "digraph")
	gs := make([]string, 0)
	for _, s := range ss {
		//log.Println(s)
		if len(strings.TrimSpace(s)) != 0 {
			gs = append(gs, "digraph"+s)
		}
	}
	//log.Println(gs)
	return gs
}

func readCloser2SVG(rc io.ReadCloser) string {
	buf := new(bytes.Buffer)
	buf.ReadFrom(rc)
	log.Println("Converting dot to SVG...")
	//log.Println("json: ", buf.String())
	var result RunResult
	json.Unmarshal(buf.Bytes(), &result)
	//log.Println("json parsed:", result)
	if result.Errors == "" {
		newStr := new(bytes.Buffer)
		// log.Println("Events parsed:", result)
		//newStr.WriteString(viz.Dot2SVG(result["Events"][0]["Message"][0]))
		message := result.Events[0].Message
		// need to parse dia subgraph
		for _, oneDot := range splitDotGraph(message) {
			//log.Println("dot: ", oneDot)
			svg := viz.Dot2SVG(oneDot)
			//log.Println("svg: ", svg)
			newStr.WriteString(svg)
		}
		//log.Println("SVG parsed:")
		return newStr.String()
	}
	log.Printf("Error when parsing result from playground:\n%s\n", result.Errors)
	return ""
}

func read2buf(rc io.ReadCloser) *bytes.Buffer {
	buf := new(bytes.Buffer)
	buf.ReadFrom(rc)
	return buf
}

func compileHandler_debug(c *gin.Context) {
	version := c.PostForm("version")
	body := c.PostForm("body")
	withVet := c.PostForm("withVet")
	log.Println(version, body, withVet)
}

// compileHandler will relay the request to play.golang.org
func compileHandler(c *gin.Context) {
	//log.Printf("%v\n", readCloser2String(c.Request.Body))
	// https://github.com/gin-gonic/gin#try-to-bind-body-into-different-structs
	// The normal methods for binding request body consumes c.Request.Body and
	// they cannot be called multiple times.
	//buf := read2buf(c.Request.Body)
	// we can change the body in the go
	body := c.PostForm("body")
	s := fmt.Sprintf("version=%d&body=%s&withVet=%s", 2, url.QueryEscape(body), "true")
	//log.Println(s)
	buf := bytes.NewBufferString(s)
	var relay io.Reader = bytes.NewReader(buf.Bytes())
	response, err := http.Post("https://play.golang.org/compile", "application/x-www-form-urlencoded; charset=UTF-8", relay)
	if err == nil {
		if response.StatusCode == 200 && response.Body != nil {
			c.String(response.StatusCode, readCloser2SVG(response.Body))
		} else {
			c.String(response.StatusCode, "Error or cannot get response from play.golang.org.")
		}
	} else {
		c.String(404, "Cannot access play.golang.org.")
	}
}