ll1/ast/ast.go

// Abstract Syntax Tree
package ast

import (
	"fmt"
	"strings"
)

import . "src.eruta.nl/beoran/ll1/common"

// Species is the kind of Ast node it is. It also has some methods on it.
type Species interface {
	Self() Species
	String() string
}

// BasicSpecies is a basic implementation of a species.
type BasicSpecies struct {
	Name string
}

func (bs BasicSpecies) Self() Species {
	return bs
}

func (bs BasicSpecies) String() string {
	return bs.Name
}

func MakeSpecies(name string) Species {
	return BasicSpecies{Name: name}
}

// Astro is an abstract syntax tree that is read only
type Astro interface {
	Value
	Species
	Parent() Ast
	Children() []Ast
	Token() Token
}

// Ast is an abstract syntax tree with read/write capabilities
type Ast interface {
	Astro
	SetParent(Ast)
	AppendChild(child Ast) Ast
}

// BasicAst is a basic implementation of an AST.
type BasicAst struct {
	Species
	parent   Ast
	children []Ast
	token    Token
}

func (ast BasicAst) Value() Value {
	return ast.token.Value()
}

func AppendChild(parent Ast, child Ast) Ast {
	basicParent := parent.(*BasicAst)
	return basicParent.AppendChild(child)
}

func New(kind Species, parent Ast, children []Ast, token Token) *BasicAst {
	ast := &BasicAst{Species: kind, parent: parent, token: token}
	return ast.AppendChildren(children...)
}

func (ast *BasicAst) AppendChildren(children ...Ast) *BasicAst {
	for _, child := range children {
		ast.AppendChild(child)
	}
	return ast
}

func (ast *BasicAst) AppendChild(child Ast) Ast {
	child.SetParent(ast)
	ast.children = append(ast.children, child)
	return ast
}

func NewChild(ast Ast, spec Species, token Token) Ast {
	child := New(spec, ast, make([]Ast, 0), token)
	ast.AppendChild(child)
	return child
}

func (ast BasicAst) IsKind(Species Species) bool {
	return ast.Species == Species
}

func (ast BasicAst) IsError() bool {
	return ast.token.Kind() == ErrorKind
}

func (ast BasicAst) IsNone() bool {
	return ast.Species == nil
}

func (ast BasicAst) Token() Token {
	return ast.token
}

func (ast BasicAst) Parent() Ast {
	return ast.parent
}

func (ast BasicAst) Children() []Ast {
	return ast.children
}

func (ast BasicAst) Self() Species {
	return ast.Species
}

func (ast *BasicAst) SetParent(parent Ast) {
	ast.parent = parent
}

func (ast BasicAst) Child(index int) Ast {
	count := len(ast.children)
	if index < 0 || index > count {
		return nil
	}
	return ast.children[index]
}

func Walk(ast Astro, walker func(node Astro) Astro) Astro {
	if found := walker(ast); found != nil {
		return found
	}
	for _, child := range ast.Children() {
		if found := Walk(child, walker); found != nil {
			return found
		}
	}
	return nil
}

func (ast BasicAst) String() string {
	return fmt.Sprintf("Ast %s: %s", ast.Species.String(), ast.token.Value().String())
}

func Display(ast Astro) {
	Walk(ast, func(node Astro) Astro {
		depth := Depth(node)
		fmt.Printf("%s", strings.Repeat("--", depth))
		if node != nil {
			fmt.Printf("Ast: %s\n", node.String())
		} else {
			fmt.Printf("Ast: nil node\n")
		}
		return nil
	})
}

func Dump(ast Astro) string {
	result := ""
	Walk(ast, func(node Astro) Astro {
		depth := Depth(node)
		result += fmt.Sprintf("%s", strings.Repeat("--", depth))
		if node != nil {
			result += fmt.Sprintf("Ast: %s\n", node.String())
		} else {
			result += fmt.Sprintf("Ast: nil node\n")
		}
		return nil
	})
	return result
}

func Depth(ast Astro) int {
	var depth int = 0
	parent := ast.Parent()
	for parent != nil {
		depth++
		parent = parent.Parent()
	}
	return depth
}

func CountChildren(ast Astro) int {
	return len(ast.Children())
}

func IsError(ast Astro) bool {
	return ast.Token().Kind() == ErrorKind
}

func Errors(ast Astro) []Astro {
	res := make([]Astro, 0)
	Walk(ast, func(node Astro) Astro {
		if node != nil && IsError(ast) {
			res = append(res, node)
		}
		return nil
	})
	return res
}

func EmptyAstArray() []Ast {
	return make([]Ast, 0)
}

func NewEmptyAst(species Species) *BasicAst {
	return NewAstWithToken(species, nil)
}

func NewAstNone() *BasicAst {
	return NewEmptyAst(nil)
}

func NewAstWithToken(Species Species, token Token) *BasicAst {
	return New(Species, nil, EmptyAstArray(), token)
}

// If AST has errors, return it as a merged error, otherwise returns nil
func MergeErrors(ast Ast) error {
	errlist := Errors(ast)
	if len(errlist) < 1 {
		return nil
	}
	sep := ""
	res := ""
	for _, err := range errlist {
		res = fmt.Sprintf("%s%s%s", res, sep, err)
		sep = "\n"
	}
	return fmt.Errorf("%s", res)
}