Add pretty display for struct array

cmd/list.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"fmt"
 	"log"
+	"reflect"
 	"io/ioutil"
 	"gocage/jail"
 	"encoding/json"
@@ -13,19 +14,147 @@ import (
 
 var gJails []Jail
 
+/* Pretty display of jails field
+   Fields to show are given in a string array parameter
+   Ex. : displayJails(["Name", "JID", "RootPath"])
+*/
+func displayStructFields(jails []Jail, valsToDisplay []string) {
+	/* A line is defined by :
+		Nr of fields
+		For each field :
+			Its name
+			Its max length
+			Its value
+	*/
+	type Field struct {
+		Name	string
+		MaxLen	int
+		Value	string
+	}
+
+	type Line []Field
+
+	type Output []Line
+	var out Output
+
+	//fmt.Printf("%d fields in a %d items structure\n", len(valsToDisplay), len(jails))
+
+	// Browse structure to get max length and values
+	for _, j := range jails {
+		// Have to use a pointer, else reflect.Value.Elem() will panic : https://pkg.go.dev/reflect#Value.Elem
+		tj := &j
+		
+		line := make([]Field, len(valsToDisplay))
+		for i, f := range valsToDisplay {
+			a := reflect.ValueOf(&tj).Elem()
+			//fmt.Printf("Struct : %s, Champ : %s\n", a.String(), f)
+			//fmt.Printf("%v", a.Elem().FieldByName(f).Interface())
+			field := Field {
+				Name: f,
+				// For now this just contains this item length, will adjust later
+				MaxLen: len(fmt.Sprintf("%v", a.Elem().FieldByName(f).Interface())),
+				Value: fmt.Sprintf("%v", a.Elem().FieldByName(f).Interface()),
+			}
+			line[i] = field
+			
+		}
+		out = append(out, line)
+	}
+
+	// Get real maximum length
+	maxlen := make([]int, len(valsToDisplay))
+	for i := 0; i< len(valsToDisplay); i++ {
+		maxlen[i] = 0
+	}
+	for _, l := range out {
+		for i, f := range l {
+			if f.MaxLen > maxlen[i] {
+				maxlen[i] = f.MaxLen
+			}
+		}
+	}
+
+	// Align maxlen to the real maximum length
+	for io, l := range out {
+		for ii, _ := range l {
+			// We need to access slice by index if we want to modify content
+			out[io][ii].MaxLen = maxlen[ii]
+		}
+	}
+
+	totalLen := 0
+	// Add separator and 2 blank spaces 
+	for _, f := range out[0] {
+		totalLen += f.MaxLen + 3
+	}
+	// Then add starting delimiter 
+	totalLen += 1
+
+	Debug := false
+	if Debug == true {
+		for _, f := range out[0] {
+			fmt.Printf("%s max length : %d\n", f.Name, f.MaxLen)
+		}
+	}
+
+	// Lets draw things on the screen!
+	// First, headers
+	for i := 0; i < totalLen ; i++ {
+		fmt.Printf("-")
+	}
+	fmt.Printf("\n")
+
+	for i, f := range out[0] {
+		if i == 0 {
+			fmt.Printf("|")
+		}
+		fmt.Printf(" %s", f.Name)
+		for i := len(f.Name)+1 ; i < f.MaxLen+1 ; i++ {
+			fmt.Printf(" ")
+		}
+		fmt.Printf(" |")
+	}
+	fmt.Printf("\n")
+	for i := 0; i < totalLen ; i++ {
+		fmt.Printf("-")
+	}
+	fmt.Printf("\n")
+
+	// Then display data
+	for _, l := range out {
+		for i, f := range l {
+			if i == 0 {
+				fmt.Printf("|")
+			}
+			fmt.Printf(" %s", f.Value)
+			for i := len(f.Value)+1 ; i < f.MaxLen+1 ; i++ {
+				fmt.Printf(" ")
+			}
+			fmt.Printf(" |")
+		}
+		fmt.Printf("\n")
+	}
+	for i := 0; i < totalLen ; i++ {
+		fmt.Printf("-")
+	}
+	fmt.Printf("\n")
+}
 
 func listJails(args []string) {
 	for _, d := range viper.GetStringSlice("datastore") {
 		listJailsFromDatastore(d)
 	}
 
-	for _, j := range (gJails) {
+	displayStructFields(gJails, []string{"JID", "Name", "RootPath"})
+
+/*	for _, j := range (gJails) {
 		if j.Running {
 			fmt.Printf("%d ; %s ; %s ; %s\n", j.JID, j.Name, j.Config.Ip4_addr, j.Config.Release)
 		} else {
 			fmt.Printf("   ; %s ; %s ; %s\n", j.Name, j.Config.Ip4_addr, j.Config.Release)
 		}
 	}
+*/
 }