From c5a0ba7d29da7effa0ae18bffa10fc0be359b8e7 Mon Sep 17 00:00:00 2001
From: Paul Buetow <pbuetow@mimecast.com>
Date: Fri, 3 Jul 2020 14:13:13 +0100
Subject: bump up version to 3.0.0. can run continuous background mapreduce
 queries, useful for log file monitorig for example. breaking protocol change
 which allows to mapreduce aggreate messages containing the default field
 separator |. add of more unit tests. add logformat mapreduce query keyword.
 add set mapreduce clause support and support to evaluate built-in functions
 such as md5sum() and maskdigits().

---
 internal/mapr/funcs/function.go | 66 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 internal/mapr/funcs/function.go

(limited to 'internal/mapr/funcs/function.go')

diff --git a/internal/mapr/funcs/function.go b/internal/mapr/funcs/function.go
new file mode 100644
index 0000000..52aaa98
--- /dev/null
+++ b/internal/mapr/funcs/function.go
@@ -0,0 +1,66 @@
+package funcs
+
+import (
+	"fmt"
+	"strings"
+)
+
+// CallbackFunc is a function which can be executed by the mapreduce engine
+type CallbackFunc func(text string) string
+
+// Function embeddes the function name to the callback function
+type Function struct {
+	// Name of the callback function
+	Name string
+	call CallbackFunc
+}
+
+// FunctionStack is a list of functions stacked each other
+type FunctionStack []Function
+
+// NewFunctionStack parses the input string, e.g. foo(bar("arg")) and returns a corresponding function stack.
+func NewFunctionStack(in string) (FunctionStack, string, error) {
+	var fs FunctionStack
+
+	getCallback := func(name string) (CallbackFunc, error) {
+		var cb CallbackFunc
+
+		switch name {
+		case "md5sum":
+			return Md5Sum, nil
+		case "maskdigits":
+			return MaskDigits, nil
+		default:
+			return cb, fmt.Errorf("unknown function '%s'", name)
+		}
+	}
+
+	aux := in
+	for strings.HasSuffix(aux, ")") {
+		index := strings.Index(aux, "(")
+		if index <= 0 {
+			return fs, "", fmt.Errorf("unable to parse function '%s' at '%s'", in, aux)
+		}
+		name := aux[0:index]
+
+		call, err := getCallback(name)
+		if err != nil {
+			return fs, "", err
+		}
+		fs = append(fs, Function{name, call})
+		aux = aux[index+1 : len(aux)-1]
+	}
+
+	return fs, aux, nil
+}
+
+// Call the function stack.
+func (fs FunctionStack) Call(str string) string {
+	for i := len(fs) - 1; i >= 0; i-- {
+		//logger.Debug("Call", fs[i].Name, str)
+		str = fs[i].call(str)
+		//logger.Debug("Call.result", fs[i].Name, str)
+	}
+
+	return str
+}
-- 
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