biggest part of query parser

internal/common/strings.go

@@ -1,6 +1,9 @@
 package common
 
-import "strings"
+import (
+	"errors"
+	"strings"
+)
 
 func Unify(s string) string {
 	s = strings.TrimSpace(s)
@@ -10,3 +13,99 @@ func Unify(s string) string {
 	}
 	return s
 }
+
+type Query struct {
+	Search string
+	Artist string
+	Album  string
+	Song   string
+}
+
+const emptyChar = ' '
+const songChar = 's'
+const albumChar = 'r'
+const artistChar = 'a'
+
+func NewQuery(search string) (Query, error) {
+	search = strings.TrimSpace(search)
+	query := Query{
+		Search: search,
+	}
+	if search == "" {
+		return query, errors.New("search should not be empty")
+	}
+
+	parsed := make(map[rune]string)
+	indexChar := emptyChar
+	nextIsIndex := false
+	ignoreNextIfSpace := false
+
+	for _, char := range search {
+		// figuring out when the next char is an index char
+		if char == '#' {
+			// escape # => asserts previous char was also #
+			if nextIsIndex {
+				nextIsIndex = false
+				parsed[indexChar] = parsed[indexChar] + "#"
+				continue
+			}
+
+			nextIsIndex = true
+			continue
+		}
+
+		// setting an index char
+		if nextIsIndex {
+			if char != songChar && char != albumChar && char != artistChar {
+				return query, errors.New("the char after # has to be " + string(songChar) + ", " + string(albumChar) + " or " + string(artistChar) + " if it isn't escaped with another #")
+			}
+
+			if _, ok := parsed[char]; ok {
+				return query, errors.New("you can use #" + string(char) + " only once")
+			}
+
+			indexChar = char
+			nextIsIndex = false
+			ignoreNextIfSpace = true
+			parsed[char] = ""
+			continue
+		}
+
+		if ignoreNextIfSpace {
+			ignoreNextIfSpace = false
+
+			if char == ' ' {
+				continue
+			}
+		}
+
+		parsed[indexChar] = parsed[indexChar] + string(char)
+	}
+
+	if nextIsIndex {
+		return query, errors.New("there cant be an unescaped # at the end, it has to be escaped with another #")
+	}
+
+	if _, ok := parsed[emptyChar]; ok {
+		// no other index char should be used
+
+		e := errors.New("if you use advanced search with # you cant put anything before the first #")
+		if _, ok := parsed[songChar]; ok {
+			return query, e
+		}
+		if _, ok := parsed[albumChar]; ok {
+			return query, e
+		}
+		if _, ok := parsed[artistChar]; ok {
+			return query, e
+		}
+
+		query.Search = parsed[emptyChar]
+	} else {
+		query.Song = strings.TrimSpace(parsed[songChar])
+		query.Album = strings.TrimSpace(parsed[albumChar])
+		query.Artist = strings.TrimSpace(parsed[artistChar])
+	}
+
+	return query, nil
+}

internal/plugin/interface.go

@@ -140,3 +140,7 @@ func Fetch(source data.Source) (data.MusicObject, error) {
 
 	return nil, nil
 }
+
+func Search(q string) {
+
+}