add ussd build module

Author: ochom

ussd/builder.go

@@ -0,0 +1,116 @@
+package ussd
+
+import (
+	"strings"
+
+	"github.com/ochom/gutils/arrays"
+	"github.com/ochom/gutils/logs"
+)
+
+// GetMenuFunc returns the menu function
+type GetMenuFunc func(params map[string]string) string
+
+type Children []*Step
+
+// Step a ussd step
+type Step struct {
+	Key      string
+	Menu     GetMenuFunc
+	End      bool
+	Params   map[string]string
+	Children Children
+}
+
+// NewStep creates a new step
+func NewStep(menuFunc GetMenuFunc) Step {
+	return Step{
+		Menu:   menuFunc,
+		Params: make(map[string]string),
+	}
+}
+
+// AddStep adds a new step
+func (s *Step) AddStep(step Step) {
+	s.Children = append(s.Children, &step)
+}
+
+// GetResponse returns the response
+func (s *Step) GetResponse() string {
+	response := s.Menu(s.Params)
+	if strings.HasPrefix(response, "CON ") || strings.HasPrefix(response, "END ") {
+		return response
+	}
+
+	if s.End {
+		return "END " + response
+	}
+
+	return "CON " + response
+}
+
+// getMatchingChild returns the matching child
+func (s *Step) getMatchingChild(ussdPart string) *Step {
+	// first check exact matching children
+	child := arrays.Find(s.Children, func(c *Step) bool {
+		return strings.EqualFold(ussdPart, c.Key)
+	})
+
+	if child != nil {
+		return child
+	}
+
+	// then check if the key is a wildcard
+	child = arrays.Find(s.Children, func(c *Step) bool {
+		return c.Key == ""
+	})
+
+	return child
+}
+
+// walk goes through the menu and finds matching children
+func (s *Step) walk(ussdParts []string) *Step {
+	remainingPieces := len(ussdParts)
+
+	// break if no piece is left
+	if remainingPieces == 0 {
+		return s
+	}
+
+	// break if only once piece is left by finding the child that matches the remaining piece
+	if remainingPieces == 1 {
+		return s.getMatchingChild(ussdParts[0])
+	}
+
+	// first check kids that exactly match the first piece
+	for _, child := range s.Children {
+		if strings.EqualFold(ussdParts[0], child.Key) {
+			return child.walk(ussdParts[1:])
+		}
+	}
+
+	// then check if the first piece is a wildcard
+	for _, child := range s.Children {
+		if child.Key == "" {
+			return child.walk(ussdParts[1:])
+		}
+	}
+
+	return nil
+}
+
+// Parse takes a ussd string and returns the right child
+func (s *Step) Parse(sessionData map[string]string, ussdParts []string) *Step {
+	child := s.walk(ussdParts)
+	if child == nil {
+		logs.Error("Could not get the correct child for the ussd string")
+		return nil
+	}
+
+	remainingPieces := len(ussdParts)
+	if remainingPieces > 1 {
+		sessionData["input"] = ussdParts[remainingPieces-1]
+	}
+
+	child.Params = sessionData
+	return child
+}

ussd/session.go

@@ -0,0 +1,32 @@
+package ussd
+
+var session map[string]map[string]string
+
+func init() {
+	session = make(map[string]map[string]string)
+}
+
+func HasSession(sessionId string) bool {
+	_, ok := session[sessionId]
+	return ok
+}
+
+func GetSession(sessionId string) map[string]string {
+	if !HasSession(sessionId) {
+		SetSession(sessionId, make(map[string]string))
+	}
+
+	return session[sessionId]
+}
+
+func SetSession(sessionId string, params map[string]string) {
+	session[sessionId] = params
+}
+
+func RemoveSession(sessionId string) {
+	delete(session, sessionId)
+}
+
+func ClearSession() {
+	session = make(map[string]map[string]string)
+}

ussd/ussd.go

@@ -0,0 +1,54 @@
+package ussd
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/ochom/gutils/logs"
+)
+
+var mainMenu *Step
+
+func InitMenu(step *Step) {
+	if mainMenu == nil {
+		mainMenu = step
+	}
+}
+
+type Params struct {
+	Ussd        string
+	SessionId   string
+	PhoneNumber string
+}
+
+func Parse(data Params) (*Step, error) {
+	if mainMenu == nil {
+		return nil, fmt.Errorf("mainMenu has not been created")
+	}
+
+	data.Ussd = strings.TrimSuffix(data.Ussd, "#")
+	data.Ussd = strings.TrimPrefix(data.Ussd, "*")
+
+	parts := []string{}
+	if data.Ussd != "" {
+		parts = strings.Split(data.Ussd, "*")
+	}
+
+	// check if session exists
+	if !HasSession(data.SessionId) {
+		SetSession(data.SessionId, make(map[string]string))
+	}
+
+	mainMenu.Params = map[string]string{
+		"phone_number": data.PhoneNumber,
+		"session_id":   data.SessionId,
+		"ussd":         data.Ussd,
+	}
+	step := mainMenu.Parse(mainMenu.Params, parts)
+	if step == nil {
+		logs.Error("Could not get the correct child for the ussd string")
+		return nil, fmt.Errorf("could not get the correct child for the ussd string")
+	}
+
+	return step, nil
+}