feat: KCL Go AST definition and parser API

Signed-off-by: peefy <[email protected]>

example_test.go

@@ -11,6 +11,7 @@ import (
 
 	kcl "kcl-lang.io/kcl-go"
 	"kcl-lang.io/kcl-go/pkg/native"
+	"kcl-lang.io/kcl-go/pkg/parser"
 	"kcl-lang.io/kcl-go/pkg/spec/gpyrpc"
 )
 
@@ -213,6 +214,14 @@ age = option("age")
 	// name: kcl
 }
 
+func ExampleParseFile() {
+	result, err := parser.ParseFile("testdata/main.k", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(result)
+}
+
 func ExampleParseProgram() {
 	result, err := kcl.ParseProgram(&kcl.ParseProgramArgs{
 		Paths: []string{"testdata/main.k"},

pkg/ast/ast.go

@@ -1,25 +1,43 @@
 package ast
 
-// TODO: add more nodes from https://github.com/kcl-lang/kcl/blob/main/kclvm/ast/src/ast.rs
+// Module is an abstract syntax tree for a single KCL file.
+type Module struct {
+	Filename string           `json:"filename"`
+	Pkg      string           `json:"pkg"`
+	Doc      *Node[string]    `json:"doc"`
+	Body     []*Node[Stmt]    `json:"body"`
+	Comments []*Node[Comment] `json:"comments"`
+}
 
-// Pos denotes the struct tuple (filename, line, column, end_line, end_column).
-type Pos struct {
-	Filename  string `json:"filename"`
-	Line      uint64 `json:"line"`
-	Column    uint64 `json:"column"`
-	EndLine   uint64 `json:"end_line"`
-	EndColumn uint64 `json:"end_column"`
+// NewModule creates a new Module instance
+func NewModule() *Module {
+	return &Module{
+		Body:     make([]*Node[Stmt], 0),
+		Comments: make([]*Node[Comment], 0),
+	}
 }
 
-// Node is the file, line, and column number information that all AST nodes need to contain.
-type Node interface {
-	Pos() Pos
-	Index() string
+// Node is the file, line and column number information that all AST nodes need to contain.
+// In fact, column and end_column are the counts of character. For example, `\t` is counted as 1 character,
+// so it is recorded as 1 here, but generally col is 4.
+type Node[T any] struct {
+	ID   AstIndex `json:"id,omitempty"`
+	Node T        `json:"node,omitempty"`
+	Pos
 }
 
 // AstIndex represents a unique identifier for AST nodes.
 type AstIndex string
 
+// Pos denotes the struct tuple (filename, line, column, end_line, end_column).
+type Pos struct {
+	Filename  string `json:"filename,omitempty"`
+	Line      int64  `json:"line,omitempty"`
+	Column    int64  `json:"column,omitempty"`
+	EndLine   int64  `json:"end_line,omitempty"`
+	EndColumn int64  `json:"end_column,omitempty"`
+}
+
 // Comment node.
 type Comment struct {
 	Text string