moved scanner sources to package 'scan'

scan/ast.go

@@ -0,0 +1,147 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// ast.go
+package scan
+
+import (
+	"errors"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- ast
+
+type Ast struct {
+	forest []*Term
+	root   *Term
+}
+
+func NewAst() *Ast {
+	return &Ast{}
+}
+
+func (ast *Ast) TypeName() string {
+	return "Expression"
+}
+
+func (ast *Ast) Root() *Term {
+	return ast.root
+}
+
+func (ast *Ast) ToForest() {
+	if ast.root != nil {
+		if ast.forest == nil {
+			ast.forest = make([]*Term, 0)
+		}
+		ast.forest = append(ast.forest, ast.root)
+		ast.root = nil
+	}
+}
+
+func (ast *Ast) String() string {
+	var sb strings.Builder
+	if ast.root == nil {
+		sb.WriteString("(nil)")
+	} else {
+		ast.root.ToString(&sb)
+	}
+	return sb.String()
+}
+
+func (ast *Ast) AddTokens(tokens ...*Token) (err error) {
+	for _, tk := range tokens {
+		if _, err = ast.AddToken(tk); err != nil {
+			break
+		}
+	}
+	return
+}
+
+// func (expr *ast) addToken(tk *Token) (err error) {
+// 	_, err = expr.addToken2(tk)
+// 	return
+// }
+
+func (ast *Ast) AddToken(tk *Token) (t *Term, err error) {
+	if t = NewTerm(tk); t != nil {
+		err = ast.AddTerm(t)
+	} else {
+		err = tk.Errorf("unexpected token %q", tk.String())
+	}
+	return
+}
+
+func (ast *Ast) AddTerm(node *Term) (err error) {
+	if ast.root == nil {
+		ast.root = node
+	} else {
+		ast.root, err = ast.insert(ast.root, node)
+	}
+	return
+}
+
+func (ast *Ast) insert(tree, node *Term) (root *Term, err error) {
+	if tree.getPriority() < node.getPriority() {
+		root = tree
+		if tree.isComplete() {
+			var subRoot *Term
+			last := tree.removeLastChild()
+			if subRoot, err = ast.insert(last, node); err == nil {
+				subRoot.SetParent(tree)
+			}
+		} else {
+			node.SetParent(tree)
+		}
+	} else if !node.isLeaf() {
+		root = node
+		tree.SetParent(node)
+	} else {
+		err = node.Errorf("two adjacent operators: %q and %q", tree, node)
+	}
+	return
+}
+
+func (ast *Ast) Finish() {
+	if ast.root == nil && ast.forest != nil && len(ast.forest) >= 1 {
+		ast.root = ast.forest[len(ast.forest)-1]
+		ast.forest = ast.forest[0 : len(ast.forest)-1]
+	}
+}
+
+func (ast *Ast) Eval(ctx kern.ExprContext) (result any, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if errVal, ok := r.(error); ok {
+				err = errVal
+			} else {
+				err = errors.New("unexpected error while evaluating the expression")
+			}
+		}
+	}()
+
+	ast.Finish()
+
+	if ast.root != nil {
+		// initDefaultVars(ctx)
+		if ast.forest != nil {
+			for _, tree := range ast.forest {
+				if result, err = tree.Compute(ctx); err == nil {
+					ctx.UnsafeSetVar(kern.ControlLastResult, result)
+				} else {
+					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
+					break
+				}
+			}
+		}
+		if err == nil {
+			if result, err = ast.root.Compute(ctx); err == nil {
+				ctx.UnsafeSetVar(kern.ControlLastResult, result)
+			}
+		}
+		// } else {
+		// 	err = errors.New("empty expression")
+	}
+	return
+}