alert: Add optimizations (#939)

* alert: Add optimizations

* alert: add basic benchmarks

* alert: fix linter issue

* documentation: change to text/template as html/template escapes to protect against code injection. Add readme.md for alert.

* README: Add package name

* alert: link up with engine settings

* request: isVerbose refactor

* Update exchanges/alert/alert_test.go

Co-authored-by: Scott <gloriousCode@users.noreply.github.com>

* Update exchanges/alert/alert.go

Co-authored-by: Scott <gloriousCode@users.noreply.github.com>

* glorious: nits

* glorious: fun police

* documentation: regen

Co-authored-by: Ryan O'Hara-Reid <ryan.oharareid@thrasher.io>
Co-authored-by: Scott <gloriousCode@users.noreply.github.com>

cmd/documentation/documentation.go

@@ -6,12 +6,12 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"html/template"
 	"log"
 	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
+	"text/template"
 	"time"
 
 	"github.com/thrasher-corp/gocryptotrader/common"
@@ -430,14 +430,16 @@ func GetTemplateFiles() (*template.Template, error) {
 				return nil
 			}
 
-			var parseError error
-			tmpl, parseError = tmpl.ParseGlob(filepath.Join(path, "*.tmpl"))
-			if parseError != nil {
-				if strings.Contains(parseError.Error(), "pattern matches no files") {
+			var tmplExt *template.Template
+			tmplExt, err = tmpl.ParseGlob(filepath.Join(path, "*.tmpl"))
+			if err != nil {
+				fmt.Println(err)
+				if strings.Contains(err.Error(), "pattern matches no files") {
 					return nil
 				}
-				return parseError
+				return err
 			}
+			tmpl = tmplExt
 			return filepath.SkipDir
 		}
 		return nil

cmd/documentation/exchanges_templates/alert.tmpl

@@ -0,0 +1,92 @@
+{{define "exchanges alert" -}}
+{{template "header" .}}
+## Alert
+
++ This package allows for multiple routines to wait for a state change on any required data.
+
+### Examples:
+
++ Implementation:
+
+```go
+// SomeChangingType defines an example struct with an embedded alert.Notice
+// type for easy access to the notice methods.
+type SomeChangingType struct {
+	ValueThatChanges int64
+	alert.Notice
+	mu sync.Mutex // Protection for routine shenanigans
+}
+
+// Update will update in a separate routine
+func (s *SomeChangingType) Update(newValue int64) {
+	// This simulates a changing variable or state
+	s.mu.Lock()
+	s.ValueThatChanges = newValue
+	// This will alert any routines that are currently waiting for a change
+	s.Alert()
+	s.mu.Unlock()
+}
+
+// WhatsTheValue will retrieve the value that was changed and should be
+// different from the past value. Efficiency++
+func (s *SomeChangingType) WhatsTheValue() int64 {
+	s.mu.Lock()
+	value := s.ValueThatChanges
+	s.mu.Unlock()
+	return value
+}
+```
+
++ Routine waiting for change:
+
+```go
+// ExampleRoutineThatWaits defines an exchange potential routine that will wait
+// for an impending change.
+func ExampleRoutineThatWaits(potentialChange *SomeChangingType) {
+	// Every iteration requires a Wait() call.
+	for range potentialChange.Wait(nil) {
+		val := potentialChange.WhatsTheValue()
+		fmt.Println("Value:", val)
+	}
+}
+
+// AnotherExampleRoutineThatWaits defines an exchange potential routine that 
+// will wait for an impending change.
+func AnotherExampleRoutineThatWaits(potentialChange *SomeChangingType) {
+	// Every iteration requires a Wait() call.
+	for {
+		select {
+			case <-potentialChange.Wait(nil):
+				val := potentialChange.WhatsTheValue()
+				fmt.Println("Value:", val)
+			case <-shutdownChannel:
+				fmt.Println("Good-Bye!")
+			return 
+		}
+	}
+}
+
+
+// WARNING: PLEASE DON'T DO THIS.
+// This will stop alerting for this specific data type due to the shared nature 
+// of the underlying channels using a sync.Pool.
+func ABadExampleRoutineThatWaits(potentialChange *SomeChangingType) {
+	capturedChannel := potentialChange.Wait(nil)
+	for {
+		select {
+			case <-capturedChannel:
+				// This will produce incorrect results or no change. 
+				val := potentialChange.WhatsTheValue()
+				fmt.Println("Value:", val)
+			case <-shutdownChannel:
+				fmt.Println("Good-Bye!")
+			return 
+		}
+	}
+}
+```
+
+### Please click GoDocs chevron above to view current GoDoc information for this package
+{{template "contributions"}}
+{{template "donations" .}}
+{{end}}