basic: introduce basic one-shot INI-style decoder

Signed-off-by: Alejandro Mery <amery@jpi.io>

basic/decoder.go

@@ -0,0 +1,49 @@
+package basic
+
+import (
+	"bytes"
+	"io"
+	"io/fs"
+	"strings"
+
+	"asciigoat.org/ini/parser"
+)
+
+type decoder struct {
+	p   *parser.Parser
+	out *Document
+
+	queue   []*token
+	current *Section
+}
+
+// Decode attempts to decode an INI-style from an [io.Reader] array into a [Document]
+func Decode(r io.Reader) (*Document, error) {
+	var out Document
+
+	if r == nil {
+		return nil, fs.ErrNotExist
+	}
+
+	// parser
+	p := parser.NewParser(r)
+	// decoder
+	dec := decoder{p: p, out: &out}
+	// glue
+	p.OnToken = dec.OnToken
+	p.OnError = dec.OnError
+
+	// Go!
+	err := p.Run()
+	return &out, err
+}
+
+// DecodeBytes attempts to decode an INI-style bytes array into a [Document]
+func DecodeBytes(b []byte) (*Document, error) {
+	return Decode(bytes.NewReader(b))
+}
+
+// DecodeString attempts to decode an INI-style string into a [Document]
+func DecodeString(s string) (*Document, error) {
+	return Decode(strings.NewReader(s))
+}