go__sqs_demo/back/web/home.go

package web

import (
	"context"
	"log"
	"net/http"
	"time"

	"github.com/gin-contrib/sessions"
	"github.com/gin-gonic/gin"

	"code.osinet.fr/fgm/sqs_demo/back/services/redriver"
)

// classifyPolicies distributes queue policies across five bins:
//   - wild: policies describing a DLQ with an allowAll policy
//   - closed: policies describing a DLQ with an denyAll policy
//   - byQueue: policies describing a DLQ with an byQueue policy
//   - sources: policies describing a queue with a DLQ
//   - notSources: policies describing a queue without a DLQ
//
// Note that dead-letter queues may also by source queues, for multi-level processing, and vice-versa.
//
// For easier reading, DLQs are not listed as part of the non-source list.
func classifyPolicies(policies map[string]*redriver.QueueRedrivePolicies) (byQueue, wild, closed, sources map[string]redriver.QueueRedrivePolicies, notSources []string) {
	DLQs := make(map[string]redriver.QueueRedrivePolicies)
	sources = make(map[string]redriver.QueueRedrivePolicies)
	wild = make(map[string]redriver.QueueRedrivePolicies)
	closed = make(map[string]redriver.QueueRedrivePolicies)
	byQueue = make(map[string]redriver.QueueRedrivePolicies)
	nsTemp := make([]string, 0, len(notSources))

	for qURL, qrp := range policies {
		if qrp.QueueInfoAttributesRedriveAllowPolicy != nil {
			DLQs[qURL] = *qrp
		}
		if qrp.QueueInfoAttributesRedrivePolicy != nil {
			sources[qURL] = *qrp
		} else {
			nsTemp = append(nsTemp, qURL)
		}
	}
	for _, qURL := range nsTemp {
		if _, ok := DLQs[qURL]; !ok {
			notSources = append(notSources, qURL)
		}
	}
	for qURL, qrp := range DLQs {
		rap := qrp.QueueInfoAttributesRedriveAllowPolicy
		switch rap.RedrivePermission {
		case "allowAll":
			wild[qURL] = qrp
		case "denyAll":
			closed[qURL] = qrp
		case "byQueue":
			byQueue[qURL] = qrp
		}
	}

	return
}

func policiesByURL(c *gin.Context, qURLs []string, rd redriver.Redriver, ctx context.Context) map[string]*redriver.QueueRedrivePolicies {
	qMap := make(map[string]*redriver.QueueRedrivePolicies, len(qURLs))
	for _, qURL := range qURLs {
		name, err := redriver.NameFromURL(qURL)
		if err != nil {
			log.Println(http.StatusInternalServerError)
			c.HTML(http.StatusInternalServerError, "500", nil)
		}
		qrp, err := rd.GetRedrivePolicies(ctx, name)
		if err != nil || qrp == nil {
			log.Println(err)
			c.HTML(http.StatusInternalServerError, "500", nil)
		}
		qMap[qURL] = qrp
	}
	return qMap
}

type link struct{ URL, Text string }

// queueRow provides templates with a representation for all kinds of table cells
type queueCell struct {
	Message string
	Link    *link
	Links   []link
}

type QueueRow [2]queueCell

func makeHomeHandler(rd redriver.Redriver) gin.HandlerFunc {
	return func(c *gin.Context) {
		ctx := c.Request.Context()
		sess := sessions.Default(c)
		flashes := sess.Flashes()
		defer func() { _ = sess.Save() }()

		t0 := time.Now()
		qURLs, err := rd.ListQueues(ctx, "")
		latency := time.Since(t0)
		if err != nil {
			log.Printf("failed listing queues: %v", err)
			c.HTML(http.StatusInternalServerError, "500", nil)
			return
		}
		policies := policiesByURL(c, qURLs, rd, ctx)
		byqueue, wild, closed, sources, notSources := classifyPolicies(policies)
		// log.Printf("DLQs: %#v\nSRCs: %#v\nNoSRCs: %#v\n", maps.Keys(DLQs), maps.Keys(SRCs), NoSRCs)
		l := len(byqueue)
		if len(wild) > 0 {
			l++
		}
		if len(closed) > 0 {
			l++
		}
		if len(notSources) > 0 {
			l++
		}
		rows := make([]QueueRow, 0, l) // Sources appears within a byQueue row

		rows, err = prepareSingleLeft(wild, rows, "All source queues allowed")
		if err != nil {
			log.Printf("failed converting queue URL %q: %v", qURLs, err)
			c.HTML(http.StatusInternalServerError, "500", nil)
			return
		}
		rows, err = prepareSingleLeft(closed, rows, "No source queue allowed")
		if err != nil {
			log.Printf("failed converting queue URL %q: %v", qURLs, err)
			c.HTML(http.StatusInternalServerError, "500", nil)
			return
		}
		rows, err = prepareSingleRight(notSources, rows, "No associated DLQ")
		if err != nil {
			log.Printf("failed converting queue URL %q: %v", qURLs, err)
			c.HTML(http.StatusInternalServerError, "500", nil)
			return
		}

		// for qURLs := range closed {
		//
		// }
		log.Println(sources)
		c.HTML(http.StatusOK, "home", gin.H{
			"flashes": flashes,
			"latency": latency,
			"rows":    rows,
		})

	}
}

func prepareSingleLeft(list map[string]redriver.QueueRedrivePolicies, rows []QueueRow, msg string) ([]QueueRow, error) {
	if len(list) > 0 {
		row := QueueRow{
			{Message: msg},
			{Links: make([]link, 0, len(list))},
		}
		for qURL := range list {
			name, err := redriver.NameFromURL(qURL)
			if err != nil {
				return nil, err
			}
			row[1].Links = append(row[1].Links, link{URL: "/queue/" + name, Text: name})
		}
		rows = append(rows, row)
	}
	return rows, nil
}

func prepareSingleRight(list []string, rows []QueueRow, msg string) ([]QueueRow, error) {
	if len(list) > 0 {
		row := QueueRow{
			{Links: make([]link, 0, len(list))},
			{Message: msg},
		}
		for _, qURL := range list {
			name, err := redriver.NameFromURL(qURL)
			if err != nil {
				return nil, err
			}
			row[0].Links = append(row[0].Links, link{URL: "/queue/" + name, Text: name})
		}
		rows = append(rows, row)
	}
	return rows, nil
}