Feat/Add post processors + refactor project (#37)

* chg: feat: clean known patterns from title

* chg: refactor: remove duplicated code, and improve maintainability

* chg: feat: add audio tagging post-processor

* chg: refactor: add generic parallelMap function

* chg: refactor: move more function to common locations

* chg: docs: add func docs

utils/util.go

@@ -1,10 +1,13 @@
 package utils
 
 import (
+	"fmt"
 	"strings"
+
 	"golang.org/x/net/html"
 )
 
+// Filter filters a slice based on a predicate function.
 func Filter[A any](arr []A, f func(A) bool) []A {
 	var res []A
 	res = make([]A, 0)
@@ -16,6 +19,71 @@ func Filter[A any](arr []A, f func(A) bool) []A {
 	return res
 }
 
+// ParallelMap applies a function to each item in the iterable concurrently
+// and returns a slice of results. It can handle errors by passing an error handler function.
+func ParallelMap[T any, R any](iterable []T, mapper func(item T) ([]R, error), errHandler ...func(error)) []R {
+	var itChan = make(chan []R)
+	var errChan = make(chan error)
+	mappedItems := []R{}
+	for _, link := range iterable {
+		go func(link T) {
+			items, err := mapper(link)
+			if err != nil {
+				errChan <- err
+			}
+			itChan <- items
+		}(link)
+	}
+
+	for range iterable {
+		select {
+		case items := <-itChan:
+			mappedItems = append(mappedItems, items...)
+		case err := <-errChan:
+			for _, handler := range errHandler {
+				handler(err)
+			}
+			if len(errHandler) == 0 {
+				fmt.Println(err)
+			}
+		}
+	}
+	return mappedItems
+}
+
+// StableUniq removes duplicates from a slice while maintaining the order of elements.
+func StableUniq(s []string) []string {
+	var uniq []map[string]interface{}
+	m := make(map[string]map[string]interface{})
+	for i, v := range s {
+		m[v] = map[string]interface{}{
+			"v": v,
+			"i": i,
+		}
+	}
+	// to order by index
+	for _, v := range m {
+		uniq = append(uniq, v)
+	}
+
+	// sort by index
+	for i := 0; i < len(uniq); i++ {
+		for j := i + 1; j < len(uniq); j++ {
+			if uniq[i]["i"].(int) > uniq[j]["i"].(int) {
+				uniq[i], uniq[j] = uniq[j], uniq[i]
+			}
+		}
+	}
+
+	// get only values
+	var uniqValues []string
+	for _, v := range uniq {
+		uniqValues = append(uniqValues, v["v"].(string))
+	}
+
+	return uniqValues
+}
+
 func IsValidHTML(input string) bool {
 	r := strings.NewReader(input)
 	_, err := html.Parse(r)