parser: add placeholder for ini Parser

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

parser/parser.go

@@ -0,0 +1,77 @@
+// Package parser parses dosini-style files
+package parser
+
+import (
+	"io"
+
+	"asciigoat.org/core/lexer"
+)
+
+// Parser parses a dosini-style document
+type Parser struct {
+	src *lexer.Reader
+
+	pos lexer.Position
+
+	// OnSection is called after a [section] is parsed.
+	// Returning an error will abort the process.
+	OnSection func(pos lexer.Position, name, subname string, hasSubname bool) error
+
+	// OnField is called after a `key = value` entry is parsed
+	// Returning an error will abort the process.
+	OnField func(pos lexer.Position, key, value string) error
+
+	// OnComment is called after a comment is parsed
+	// Returning an error will abort the process.
+	OnComment func(pos lexer.Position, comment string) error
+
+	// OnError is called after each parsing error, which you are allowed to
+	// override.
+	// OnError is called for EOF as well, but this error isn't returned as such by
+	// Parser.Run(). The caller will receive (nil, nil) instead indicating the
+	// processes terminated correctly.
+	OnError func(pos lexer.Position, content string, err error) error
+}
+
+func defaultOnSection(_ lexer.Position, _, _ string, _ bool) error { return nil }
+func defaultOnField(_ lexer.Position, _, _ string) error           { return nil }
+func defaultOnComment(_ lexer.Position, _ string) error            { return nil }
+
+func defaultOnError(pos lexer.Position, content string, err error) error {
+	return &lexer.Error{
+		Line:    pos.Line,
+		Column:  pos.Column,
+		Content: content,
+		Err:     err,
+	}
+}
+
+func (p *Parser) setDefaults() {
+	if p.OnSection == nil {
+		p.OnSection = defaultOnSection
+	}
+
+	if p.OnField == nil {
+		p.OnField = defaultOnField
+	}
+
+	if p.OnComment == nil {
+		p.OnComment = defaultOnComment
+	}
+
+	if p.OnError == nil {
+		p.OnError = defaultOnError
+	}
+}
+
+// NewParser creates a dosini-style parser using
+// an [io.Reader] as source
+func NewParser(r io.Reader) *Parser {
+	if r == nil {
+		return nil
+	}
+
+	return &Parser{
+		src: lexer.NewReader(r),
+	}
+}