From 3c9e154162f97466696ab6cbfa20d87d7bc66613 Mon Sep 17 00:00:00 2001
From: xdrm-brackets <xdrm.brackets.dev@gmail.com>
Date: Tue, 22 May 2018 19:56:55 +0200
Subject: [PATCH] created 'type checker' using 'plugins'

---
 checker/public.go | 96 +++++++++++++++++++++++++++++++++++++++++++++++
 checker/types.go  | 22 +++++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 checker/public.go
 create mode 100644 checker/types.go

diff --git a/checker/public.go b/checker/public.go
new file mode 100644
index 0000000..2d2a3fb
--- /dev/null
+++ b/checker/public.go
@@ -0,0 +1,96 @@
+package checker
+
+import (
+	"fmt"
+	"plugin"
+	"strings"
+)
+
+// CreateRegistry creates an empty type registry
+// if TRUE is given, it will use default Types
+// see ./default_types.go
+func CreateRegistry(useDefaultTypes bool) *TypeRegistry {
+	return &TypeRegistry{
+		Types: make([]Type, 0),
+	}
+}
+
+// Add adds a type to the registry; it must be a
+// valid and existing plugin name without the .so extension
+func (tr *TypeRegistry) Add(pluginName string) error {
+
+	/* (1) Check plugin name */
+	if len(pluginName) < 1 {
+		return fmt.Errorf("Plugin name must not be empty")
+	}
+
+	/* (2) Check plugin extension */
+	if strings.HasSuffix(pluginName, ".so") {
+		return fmt.Errorf("Plugin name must be provided without extension: '%s'", pluginName[0:len(pluginName)-3])
+	}
+
+	/* (3) Try to load the plugin */
+	p, err := plugin.Open(fmt.Sprintf("%s.so", pluginName))
+	if err != nil {
+		return err
+	}
+
+	/* (4) Export wanted properties */
+	matcher, err := p.Lookup("Match")
+	if err != nil {
+		return fmt.Errorf("Missing method 'Match()'; %s", err)
+	}
+
+	checker, err := p.Lookup("Check")
+	if err != nil {
+		return fmt.Errorf("Missing method 'Check()'; %s", err)
+	}
+
+	/* (5) Cast Match+Check */
+	matcherCast, ok := matcher.(func(string) bool)
+	if !ok {
+		return fmt.Errorf("Match() is malformed")
+	}
+
+	checkerCast, ok := checker.(func(interface{}) bool)
+	if !ok {
+		return fmt.Errorf("Check() is malformed")
+	}
+
+	/* (6) Add type to registry */
+	tr.Types = append(tr.Types, Type{
+		Match: matcherCast,
+		Check: checkerCast,
+	})
+
+	return nil
+}
+
+// Checks the 'value' which must be of type 'name'
+func (tr TypeRegistry) Run(name string, value interface{}) bool {
+
+	var T *Type = nil
+
+	/* (1) Iterate to find matching type (take first) */
+	for _, t := range tr.Types {
+
+		// stop if found
+		if t.Match(name) {
+			T = &t
+			break
+		}
+
+		// else log
+		fmt.Printf("does not match\n")
+	}
+
+	/* (2) Abort if no matching type */
+	if T == nil {
+		return false
+	}
+
+	/* (3) Check */
+	fmt.Printf("Check is %t\n", T.Check(value))
+	return T.Check(value)
+
+}
diff --git a/checker/types.go b/checker/types.go
new file mode 100644
index 0000000..1969b08
--- /dev/null
+++ b/checker/types.go
@@ -0,0 +1,22 @@
+package checker
+
+// Matcher returns whether a type 'name' matches a type
+type Matcher func(name string) bool
+
+// Checker returns whether 'value' is valid to this Type
+// note: it is a pointer because it can be formatted by the checker if matches
+// to provide indulgent type check if needed
+type Checker func(value interface{}) bool
+
+// Type contains all necessary methods
+// for a type provided by user/developer
+type Type struct {
+	Match func(string) bool
+	Check func(interface{}) bool
+}
+
+// TypeRegistry represents a registry containing all available
+// Type-s to be used by the framework according to the configuration
+type TypeRegistry struct {
+	Types []Type // registered Type-s
+}