From 86b7a5d1430db40fd110743bcd96bac7da0f31e6 Mon Sep 17 00:00:00 2001
From: pxi <mail@patxipierce.com>
Date: Sat, 30 Dec 2023 22:35:09 +0100
Subject: [PATCH] =?UTF-8?q?=C2=AF\=5F(=E3=83=84)=5F/=C2=AF?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .gitignore                                  |   2 +
 README.md                                   |  31 +++++-
 bash-fast-replace/Makefile                  |  10 ++
 bash-fast-replace/README.md                 |  43 ++++++++
 bash-fast-replace/bin/corpus.sh             |  36 +++++++
 bash-fast-replace/bin/pairs.sh              |  28 +++++
 bash-fast-replace/bin/replace.sh            |  27 +++++
 bash-fast-replace/bin/test.sh               |  19 ++++
 bash-fast-replace/csv/.gitkeep              |   0
 go-fast-replace/Makefile                    |  13 +++
 go-fast-replace/README.md                   |  54 ++++++++++
 go-fast-replace/cmd/corpus/main.go          |  25 +++++
 go-fast-replace/cmd/pairs/main.go           |  25 +++++
 go-fast-replace/cmd/replace/main.go         | 107 ++++++++++++++++++
 go-fast-replace/csv/.gitkeep                |   0
 go-fast-replace/go.mod                      |  10 ++
 go-fast-replace/internal/corpus/corpus.go   |  45 ++++++++
 go-fast-replace/internal/corpus/go.mod      |   3 +
 go-fast-replace/internal/pairs/go.mod       |   3 +
 go-fast-replace/internal/pairs/pairs.go     |  31 ++++++
 go-fast-replace/internal/replace/bm.go      |  11 ++
 go-fast-replace/internal/replace/bm_test.go |  18 ++++
 go-fast-replace/internal/replace/cw.go      | 113 ++++++++++++++++++++
 go-fast-replace/internal/replace/go.mod     |   3 +
 24 files changed, 655 insertions(+), 2 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 bash-fast-replace/Makefile
 create mode 100644 bash-fast-replace/README.md
 create mode 100755 bash-fast-replace/bin/corpus.sh
 create mode 100755 bash-fast-replace/bin/pairs.sh
 create mode 100755 bash-fast-replace/bin/replace.sh
 create mode 100755 bash-fast-replace/bin/test.sh
 create mode 100644 bash-fast-replace/csv/.gitkeep
 create mode 100644 go-fast-replace/Makefile
 create mode 100644 go-fast-replace/README.md
 create mode 100644 go-fast-replace/cmd/corpus/main.go
 create mode 100644 go-fast-replace/cmd/pairs/main.go
 create mode 100644 go-fast-replace/cmd/replace/main.go
 create mode 100644 go-fast-replace/csv/.gitkeep
 create mode 100644 go-fast-replace/go.mod
 create mode 100644 go-fast-replace/internal/corpus/corpus.go
 create mode 100644 go-fast-replace/internal/corpus/go.mod
 create mode 100644 go-fast-replace/internal/pairs/go.mod
 create mode 100644 go-fast-replace/internal/pairs/pairs.go
 create mode 100644 go-fast-replace/internal/replace/bm.go
 create mode 100644 go-fast-replace/internal/replace/bm_test.go
 create mode 100644 go-fast-replace/internal/replace/cw.go
 create mode 100644 go-fast-replace/internal/replace/go.mod

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1cb768d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.csv
+go-fast-replace/bin/*
diff --git a/README.md b/README.md
index 607025c..59d8c0f 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,30 @@
-# fast-replace
+# Fast Replace
 
-This is a testing repo to try and find out what is the fastest way to search and replace a test file.
+This is a testing repo to try and find out what is the fastest way to search and replace a test file.
+
+## The rules are simple
+
+All tests must contain 3 programs:
+
+### A key value generator (called pairs)
+
+Generate a key/value list where the key is the search value and the value is the replace value.
+
+Call the generated file `pairs.csv`.
+
+### A random file generator (called corpus)
+
+A program that can generate a file with random data mixed with the keys of your previous set.
+
+Call the random ordered file `corpus.csv`.
+
+### A random order replacer (called replace)
+
+- Load the `pairs.csv` file and `corpus.csv`.
+- Next start a benchmark.
+- Perform replacements and output to a file called `replaced.csv`.
+- Stop the benchamark.
+
+## Conclusions
+
+Add a `README.md` to the base of your test file to explain the usage of your programs and expose your conclusions.
diff --git a/bash-fast-replace/Makefile b/bash-fast-replace/Makefile
new file mode 100644
index 0000000..9fe4241
--- /dev/null
+++ b/bash-fast-replace/Makefile
@@ -0,0 +1,10 @@
+
+install:
+	./bin/pairs.sh
+	./bin/corpus.sh
+
+run:
+	./bin/replace.sh
+
+test:
+	./bin/test.sh
diff --git a/bash-fast-replace/README.md b/bash-fast-replace/README.md
new file mode 100644
index 0000000..59bef80
--- /dev/null
+++ b/bash-fast-replace/README.md
@@ -0,0 +1,43 @@
+# Bash Fast Replace
+
+An implementation in bash.
+
+## Usage
+
+To create the corpus.csv and pairs.csv files. And perform the replacements:
+
+```bash
+make install # create corpus and pairs
+make run # create file with the replaced values
+```
+
+Then to test:
+
+```bash
+make test # Checks that the replacement worked
+```
+
+
+## Conclusions
+
+`shuf` is amazing. Using /dev/urandom directly produces broken pipe errors on when using Make.
+
+Speed is not great... But no surprize there.
+````bash
+$ make install
+./bin/pairs.sh
+Generating csv/pairs.csv...
+The generation of 1000 pairs took 2s
+./bin/corpus.sh
+Generating csv/corpus.csv...
+ generated in 3s
+
+$ make run
+./bin/replace.sh
+Generating replaced.csv...
+Replacement took 3s
+
+$ make test
+./bin/test.sh
+test OK
+````
\ No newline at end of file
diff --git a/bash-fast-replace/bin/corpus.sh b/bash-fast-replace/bin/corpus.sh
new file mode 100755
index 0000000..6a9fbd5
--- /dev/null
+++ b/bash-fast-replace/bin/corpus.sh
@@ -0,0 +1,36 @@
+#! /bin/bash
+
+# Makes a file with a number of key values
+
+START=$(date +%s)
+
+BASE=$(dirname $(dirname $(realpath -s $0)));
+AMOUNT=1000
+FILE_NAME="corpus.csv"
+FULL_PATH="$BASE/csv/$FILE_NAME"
+
+if [ -f "$FULL_PATH" ]; then
+	rm "$FULL_PATH"
+fi
+
+echo "Generating csv/$FILE_NAME..."
+
+KEY_LEN=${#AMOUNT}
+LINE_LEN=`expr 100 - $KEY_LEN`
+for (( i = 0; i < "$AMOUNT"; i++ )); do
+	KEY=$(printf "%0${KEY_LEN}d\n" $i)
+
+	LEN1=$(shuf -i "0-$LINE_LEN" -n 1)
+	LEN2=`expr 100 - $LEN1`
+
+	PART1=$(shuf -er -n "$LEN1" {a..z} | paste -sd "")
+	PART2=$(shuf -er -n "$LEN2" {a..z} | paste -sd "")
+
+	echo "$PART1$KEY$PART2" >> $FULL_PATH
+done
+
+shuf "$FULL_PATH" > "$BASE/tmp.csv" && mv "$BASE/tmp.csv" "$FULL_PATH"
+
+END=$(date +%s)
+SECONDS=`expr $END - $START`
+echo "$FILE generated in ${SECONDS}s"
diff --git a/bash-fast-replace/bin/pairs.sh b/bash-fast-replace/bin/pairs.sh
new file mode 100755
index 0000000..6c45034
--- /dev/null
+++ b/bash-fast-replace/bin/pairs.sh
@@ -0,0 +1,28 @@
+#! /bin/bash
+
+# Makes a file with a number of key values
+
+START=$(date +%s)
+
+AMOUNT=1000
+BASE=$(dirname $(dirname $(realpath -s $0)));
+FILE_NAME="pairs.csv"
+FULL_PATH="$BASE/csv/$FILE_NAME"
+
+if [ -f "$FULL_PATH" ]; then
+	rm "$FULL_PATH"
+fi
+
+echo "Generating csv/$FILE_NAME..."
+
+KEY_LEN=${#AMOUNT}
+for (( i = 0; i < "$AMOUNT"; i++ )); do
+	KEY=$(printf "%0${KEY_LEN}d\n" $i)
+	VAL=$(shuf -er -n "$KEY_LEN" {A..Z} | paste -sd "")
+
+	echo "$KEY,$VAL" >> "$FULL_PATH"
+done
+
+END=$(date +%s)
+SECONDS=`expr $END - $START`
+echo "The generation of $AMOUNT pairs took ${SECONDS}s"
\ No newline at end of file
diff --git a/bash-fast-replace/bin/replace.sh b/bash-fast-replace/bin/replace.sh
new file mode 100755
index 0000000..5f2d727
--- /dev/null
+++ b/bash-fast-replace/bin/replace.sh
@@ -0,0 +1,27 @@
+#! /bin/bash
+
+# Do search and replace for large files
+
+START=$(date +%s)
+BASE=$(dirname $(dirname $(realpath -s $0)));
+
+CORPUS_FILE="$BASE/csv/corpus.csv"
+PAIRS_FILE="$BASE/csv/pairs.csv"
+REPLACED_FILE="$BASE/csv/replaced.csv"
+
+if [ -f "$REPLACED_FILE" ]; then
+	rm "$REPLACED_FILE"
+fi
+
+echo "Generating replaced.csv..."
+
+cp "$CORPUS_FILE" "$REPLACED_FILE"
+
+while IFS=, read -r KEY VAL
+do
+	sed -i -e "s/$KEY/$VAL/g" "$REPLACED_FILE"
+done < "$PAIRS_FILE"
+
+END=$(date +%s)
+SECONDS=`expr $END - $START`
+echo "Replacement took ${SECONDS}s"
diff --git a/bash-fast-replace/bin/test.sh b/bash-fast-replace/bin/test.sh
new file mode 100755
index 0000000..0ab6028
--- /dev/null
+++ b/bash-fast-replace/bin/test.sh
@@ -0,0 +1,19 @@
+#! /bin/bash
+
+# Tests a file called replaced.csv
+BASE=$(dirname $(dirname $(realpath -s $0)));
+REPLACED_FILE="$BASE/csv/replaced.csv"
+
+if [ ! -f "$REPLACED_FILE" ]; then
+	echo "File not found: $REPLACED_FILE"
+	echo "Generate replacements first."
+	exit 1;
+fi
+
+if [[ `cat "$REPLACED_FILE"` =~  [0-9] ]]; then
+	echo 'test NOK'
+	exit 1
+else
+	echo 'test OK'
+	exit 0
+fi
diff --git a/bash-fast-replace/csv/.gitkeep b/bash-fast-replace/csv/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/go-fast-replace/Makefile b/go-fast-replace/Makefile
new file mode 100644
index 0000000..240cccb
--- /dev/null
+++ b/go-fast-replace/Makefile
@@ -0,0 +1,13 @@
+
+build:
+	go build -o bin/pairs cmd/pairs/main.go
+	go build -o bin/corpus cmd/corpus/main.go
+	go build -o bin/replace cmd/replace/main.go
+
+run:
+	./bin/corpus
+	./bin/pairs
+	./bin/replace
+
+test:
+	./bin/test.sh
diff --git a/go-fast-replace/README.md b/go-fast-replace/README.md
new file mode 100644
index 0000000..ea71b10
--- /dev/null
+++ b/go-fast-replace/README.md
@@ -0,0 +1,54 @@
+# Go Fast Replace
+
+An implementation in Go.
+
+## To build
+
+````bash
+make build
+````
+
+## To run
+
+````bash
+make run
+````
+
+## To test
+
+````bash
+make test
+````
+
+## Conclusions
+
+### Replace
+
+Current implementations:
+
+- `bm` uses `strings.NewReplacer` which uses the [Boyer–Moore](https://go.dev/src/strings/search.go) algorithm.
+- `cw` uses [Commentz–Walter](https://en.wikipedia.org/wiki/Commentz-Walter_algorithm) algorithm.
+
+#### Results
+
+- `bm` varies a lot, but is never over _460µs_.
+- `cw` is a lot slower, at around _3.5ms_, but it can search for multiple patterns at once.
+
+````shell
+$ make run
+./bin/corpus
+Creating corpus...
+./bin/pairs
+Creating pairs...
+./bin/replace
+
+bm: 273.621µs
+
+cw: 2.939254ms
+````
+
+#### Todo:
+- Implement parallelism on the Commentz–Walter implementation.
+- [Boyer–Moore variants](https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string-search_algorithm#Variants)
+- [Rabin–Karp](https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm) algorithm.
+- [Aho–Corasick](https://en.wikipedia.org/wiki/Aho%E2%80%93Corasick_algorithm) algorithm.
\ No newline at end of file
diff --git a/go-fast-replace/cmd/corpus/main.go b/go-fast-replace/cmd/corpus/main.go
new file mode 100644
index 0000000..27d9f9e
--- /dev/null
+++ b/go-fast-replace/cmd/corpus/main.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"internal/corpus"
+)
+
+func main() {
+    fmt.Println("Creating corpus...")
+    f, err := os.OpenFile("./csv/corpus.csv", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer f.Close()
+
+	lines := corpus.MakeCorpus()
+
+	// Write to file
+	for _, line := range lines {
+       f.WriteString(line + "\n")
+    }
+}
\ No newline at end of file
diff --git a/go-fast-replace/cmd/pairs/main.go b/go-fast-replace/cmd/pairs/main.go
new file mode 100644
index 0000000..26667cc
--- /dev/null
+++ b/go-fast-replace/cmd/pairs/main.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"internal/pairs"
+)
+
+func main() {
+	fmt.Println("Creating pairs...")
+	f, err := os.OpenFile("./csv/pairs.csv", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer f.Close()
+
+	lines := pairs.MakePairs()
+
+	// Write to file
+	for _, line := range lines {
+       f.WriteString(line + "\n")
+    }
+}
\ No newline at end of file
diff --git a/go-fast-replace/cmd/replace/main.go b/go-fast-replace/cmd/replace/main.go
new file mode 100644
index 0000000..0aff1e7
--- /dev/null
+++ b/go-fast-replace/cmd/replace/main.go
@@ -0,0 +1,107 @@
+package main
+
+import (
+	"encoding/csv"
+	"errors"
+	"fmt"
+    "log"
+	"os"
+	"time"
+	"internal/replace"
+)
+
+func main() {
+	run, err := getArgs()
+	if err != nil {
+		log.Fatal(err)
+		return
+	}
+
+	corpusBytes, err := os.ReadFile("./csv/corpus.csv")
+    if err != nil {
+        log.Fatal(err)
+        return
+    }
+
+	// Read the CSV file containing replacement key-value pairs
+	pairsHandle, err := os.Open("./csv/pairs.csv")
+	if err != nil {
+		fmt.Println("Error opening pairs:", err)
+		return
+	}
+	defer pairsHandle.Close()
+
+	replacements, err := csv.NewReader(pairsHandle).ReadAll()
+	if err != nil {
+		fmt.Println("Error reading pairs:", err)
+		return
+	}
+
+	corpus := string(corpusBytes)
+
+	var pairs []string
+	var replaced string
+	var startTime time.Time
+	var elapsedTime time.Duration
+	for _, algo := range run {
+		switch algo {
+		case "cw":
+			// Prepare
+			cw := replace.NewCommentzWalter()
+			for _, record := range replacements {
+				cw.AddPattern(record[0], record[1])
+			}
+			cw.BuildMatchingMachine()
+
+			// Replace
+			startTime = time.Now()
+			replaced = cw.CommentzWalterReplace(corpus)
+			elapsedTime = time.Since(startTime)
+		case "bm":
+			// Prepare...
+			for _, record := range replacements {
+				pairs = append(pairs, record[0], record[1])
+			}
+
+			// Replace
+			startTime = time.Now()
+			replaced = replace.BoyerMooreReplace(corpus, pairs)
+			elapsedTime = time.Since(startTime)
+		}
+		fmt.Printf("\n%s: %s\n", algo, elapsedTime)
+	}
+
+	// Write replaced text to a file
+	outputHandle, err := os.OpenFile("./csv/replaced.csv", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		fmt.Println("Error creating output file:", err)
+		return
+	}
+	defer outputHandle.Close()
+
+	// Write replaced text to the file
+	_, err = outputHandle.WriteString(replaced)
+	if err != nil {
+		fmt.Println("Error writing to file:", err)
+		return
+	}
+}
+
+func getArgs() ([]string, error) {
+	var run = []string{"bm", "cw"}
+
+	if len(os.Args) > 1 {
+		switch os.Args[1] {
+		case "all":
+			run = []string{"bm", "cw"}
+		case "cw":
+			run = []string{"cw"}
+		case "bm":
+			run = []string{"bm"}
+		default:
+			return []string{}, errors.New("Invalid argument.")
+		}
+	}
+
+	return run, nil
+}
diff --git a/go-fast-replace/csv/.gitkeep b/go-fast-replace/csv/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/go-fast-replace/go.mod b/go-fast-replace/go.mod
new file mode 100644
index 0000000..b5ec0d3
--- /dev/null
+++ b/go-fast-replace/go.mod
@@ -0,0 +1,10 @@
+module fast-replace
+
+go 1.21.5
+
+require internal/corpus v1.0.0
+replace internal/corpus => ./internal/corpus
+require internal/pairs v1.0.0
+replace internal/pairs => ./internal/pairs
+require internal/replace v1.0.0
+replace internal/replace => ./internal/replace
diff --git a/go-fast-replace/internal/corpus/corpus.go b/go-fast-replace/internal/corpus/corpus.go
new file mode 100644
index 0000000..761f955
--- /dev/null
+++ b/go-fast-replace/internal/corpus/corpus.go
@@ -0,0 +1,45 @@
+package corpus
+
+import (
+	"fmt"
+	"math/rand"
+)
+
+func MakeCorpus() []string {
+	// Generate data
+	lineLength := 100
+	var lines []string
+	for i := 1; i <= 1000; i++ {
+		lines = append(lines, makeLine(i, lineLength))
+	}
+
+	// Randomize
+	for i := range lines {
+	    j := rand.Intn(i + 1)
+	    lines[i], lines[j] = lines[j], lines[i]
+	}
+
+	return lines
+}
+
+func makeLine(line int, lineLength int) string {
+	var key string = fmt.Sprintf("%06d", line)
+	lineLength = lineLength - len(key)
+
+	var firstLen int = rand.Intn(lineLength)
+	var secondLen int = lineLength - firstLen
+
+	return randomString(firstLen) + key + randomString(secondLen)
+}
+
+func randomString(n int) string {
+    var letters = []rune("abcdefghijklmnopqrstuvwxyz")
+	var length int = len(letters)
+
+    s := make([]rune, n)
+    for i := range s {
+        s[i] = letters[rand.Intn(length)]
+    }
+
+    return string(s)
+}
diff --git a/go-fast-replace/internal/corpus/go.mod b/go-fast-replace/internal/corpus/go.mod
new file mode 100644
index 0000000..a90e8b0
--- /dev/null
+++ b/go-fast-replace/internal/corpus/go.mod
@@ -0,0 +1,3 @@
+module corpus
+
+go 1.21.5
diff --git a/go-fast-replace/internal/pairs/go.mod b/go-fast-replace/internal/pairs/go.mod
new file mode 100644
index 0000000..b625a25
--- /dev/null
+++ b/go-fast-replace/internal/pairs/go.mod
@@ -0,0 +1,3 @@
+module pairs
+
+go 1.21.5
diff --git a/go-fast-replace/internal/pairs/pairs.go b/go-fast-replace/internal/pairs/pairs.go
new file mode 100644
index 0000000..be50c13
--- /dev/null
+++ b/go-fast-replace/internal/pairs/pairs.go
@@ -0,0 +1,31 @@
+package pairs
+
+import (
+	"fmt"
+	"math/rand"
+)
+
+func MakePairs() []string {
+	var pairs []string
+	for i := 1; i <= 1000; i++ {
+		pairs = append(pairs, makeKey(i) + "," + makeValue())
+	}
+
+	return pairs
+}
+
+func makeKey(i int) string {
+	return fmt.Sprintf("%06d", i)
+}
+
+func makeValue() string {
+	var letters = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	var length int = len(letters)
+
+	s := make([]rune, 6)
+	for i := range s {
+		s[i] = letters[rand.Intn(length)]
+	}
+
+	return string(s)
+}
\ No newline at end of file
diff --git a/go-fast-replace/internal/replace/bm.go b/go-fast-replace/internal/replace/bm.go
new file mode 100644
index 0000000..efa6a6d
--- /dev/null
+++ b/go-fast-replace/internal/replace/bm.go
@@ -0,0 +1,11 @@
+package replace
+
+import "strings"
+
+// Uses strings.NewReplacer (which implements Boyer-Moore search)
+// See https://go.dev/src/strings/search.go
+func BoyerMooreReplace(corpus string, pairs []string) string {
+	replacer := strings.NewReplacer(pairs...)
+
+	return replacer.Replace(corpus)
+}
diff --git a/go-fast-replace/internal/replace/bm_test.go b/go-fast-replace/internal/replace/bm_test.go
new file mode 100644
index 0000000..d14bf4d
--- /dev/null
+++ b/go-fast-replace/internal/replace/bm_test.go
@@ -0,0 +1,18 @@
+package replace
+
+import (
+	"testing"
+	"internal/replace"
+)
+
+func TestBoyerMooreReplace(t *testing.T) {
+	var corpus string = "abcdefghi012345jklmnopqrst"
+	var pairs = []string{"012345", "ABCDEF"}
+
+	var want string = "abcdefghiABCDEFjklmnopqrst"
+	got := replace.BoyerMooreReplace(corpus, pairs)
+
+	if want != got {
+		t.Error("Replacement was wrong.")
+	}
+}
\ No newline at end of file
diff --git a/go-fast-replace/internal/replace/cw.go b/go-fast-replace/internal/replace/cw.go
new file mode 100644
index 0000000..ed33d12
--- /dev/null
+++ b/go-fast-replace/internal/replace/cw.go
@@ -0,0 +1,113 @@
+package replace
+
+type Node struct {
+	children map[rune]*Node
+	output   int
+	fail     *Node
+}
+
+func NewNode() *Node {
+	return &Node{
+		children: make(map[rune]*Node),
+		output:   -1,
+		fail:     nil,
+	}
+}
+
+type CommentzWalter struct {
+	root         *Node
+	patterns     []string
+	replacements map[int]string
+}
+
+func NewCommentzWalter() *CommentzWalter {
+	return &CommentzWalter{
+		root:         NewNode(),
+		patterns:     make([]string, 0),
+		replacements: make(map[int]string),
+	}
+}
+
+func (cw *CommentzWalter) AddPattern(pattern string, replacement string) {
+	cw.patterns = append(cw.patterns, pattern)
+	idx := len(cw.patterns) - 1
+	cw.replacements[idx] = replacement
+}
+
+func (cw *CommentzWalter) BuildMatchingMachine() {
+	for idx, pattern := range cw.patterns {
+		current := cw.root
+		for _, char := range pattern {
+			if _, exists := current.children[char]; !exists {
+				current.children[char] = NewNode()
+			}
+			current = current.children[char]
+		}
+		current.output = idx
+	}
+
+	queue := make([]*Node, 0)
+	for _, node := range cw.root.children {
+		queue = append(queue, node)
+		node.fail = cw.root
+	}
+
+	for len(queue) > 0 {
+		r := queue[0]
+		queue = queue[1:]
+
+		for char, child := range r.children {
+			queue = append(queue, child)
+			failNode := r.fail
+			for failNode != nil && failNode.children[char] == nil {
+				failNode = failNode.fail
+			}
+
+			if failNode == nil {
+				child.fail = cw.root
+			} else {
+				child.fail = failNode.children[char]
+			}
+		}
+	}
+}
+
+func (cw *CommentzWalter) CommentzWalterReplace(text string) string {
+	matches := make([]string, 0)
+	current := cw.root
+	runes := []rune(text)
+	replaced := make([]rune, 0)
+
+	for i, char := range runes {
+		for current != nil && current.children[char] == nil {
+			current = current.fail
+		}
+
+		if current == nil {
+			current = cw.root
+			replaced = append(replaced, runes[i])
+			continue
+		}
+
+		current = current.children[char]
+		if current.output != -1 {
+			matchIdx := current.output
+			matches = append(matches, cw.replacements[matchIdx])
+			replRunes := []rune(cw.replacements[matchIdx])
+
+			for _, rn := range replRunes {
+				replaced = append(replaced, rn)
+			}
+
+			patternLen := len(cw.patterns[matchIdx])
+			replaceLen := len(cw.replacements[matchIdx])
+			if (patternLen > replaceLen) {
+				// Skip index to after the pattern
+				dif := patternLen - replaceLen
+				i = i + dif
+			}
+		}
+	}
+
+	return string(replaced)
+}
diff --git a/go-fast-replace/internal/replace/go.mod b/go-fast-replace/internal/replace/go.mod
new file mode 100644
index 0000000..609e3fd
--- /dev/null
+++ b/go-fast-replace/internal/replace/go.mod
@@ -0,0 +1,3 @@
+module replace
+
+go 1.21.5