ast.go

// Package ast declares the types used to represent the syntax tree for Flux source code.
package ast

import (
	"encoding/json"
	"fmt"
	"regexp"
	"strconv"
	"time"
)

// Position represents a specific location in the source
type Position struct {
	Line   int `json:"line"`   // Line is the line in the source marked by this position
	Column int `json:"column"` // Column is the column in the source marked by this position
}

func (p Position) String() string {
	return fmt.Sprintf("%d:%d", p.Line, p.Column)
}

func (p Position) Less(o Position) bool {
	if p.Line == o.Line {
		return p.Column < o.Column
	}
	return p.Line < o.Line
}

func (p Position) IsValid() bool {
	return p.Line > 0 && p.Column > 0
}

// SourceLocation represents the location of a node in the AST
type SourceLocation struct {
	File   string   `json:"file,omitempty"`
	Start  Position `json:"start"`            // Start is the location in the source the node starts
	End    Position `json:"end"`              // End is the location in the source the node ends
	Source string   `json:"source,omitempty"` // Source is optional raw source
}

func (l SourceLocation) String() string {
	if l.File != "" {
		return fmt.Sprintf("%s|%v-%v", l.File, l.Start, l.End)
	}
	return fmt.Sprintf("%v-%v", l.Start, l.End)
}

func (l SourceLocation) Less(o SourceLocation) bool {
	if l.Start == o.Start {
		return l.End.Less(o.End)
	}
	return l.Start.Less(o.Start)
}

func (l SourceLocation) IsValid() bool {
	return l.Start.IsValid() && l.End.IsValid()
}

func (l *SourceLocation) Copy() *SourceLocation {
	if l == nil {
		return nil
	}
	nl := *l
	return &nl
}

// Node represents a node in the InfluxDB abstract syntax tree.
type Node interface {
	node()
	Type() string // Type property is a string that contains the variant type of the node
	Location() SourceLocation
	Errs() []Error
	CommentList() []Comment
	Copy() Node

	// All node must support json marshalling
	json.Marshaler
}

func (*Package) node()           {}
func (*File) node()              {}
func (*PackageClause) node()     {}
func (*ImportDeclaration) node() {}
func (*Block) node()             {}

func (*BadStatement) node()        {}
func (*ExpressionStatement) node() {}
func (*ReturnStatement) node()     {}
func (*OptionStatement) node()     {}
func (*BuiltinStatement) node()    {}
func (*TestStatement) node()       {}
func (*TestCaseStatement) node()   {}
func (*VariableAssignment) node()  {}
func (*MemberAssignment) node()    {}

func (*StringExpression) node()      {}
func (*ParenExpression) node()       {}
func (*ArrayExpression) node()       {}
func (*DictExpression) node()        {}
func (*FunctionExpression) node()    {}
func (*BinaryExpression) node()      {}
func (*CallExpression) node()        {}
func (*ConditionalExpression) node() {}
func (*LogicalExpression) node()     {}
func (*MemberExpression) node()      {}
func (*IndexExpression) node()       {}
func (*PipeExpression) node()        {}
func (*ObjectExpression) node()      {}
func (*UnaryExpression) node()       {}

func (*Property) node()   {}
func (*Identifier) node() {}

func (*TextPart) node()         {}
func (*InterpolatedPart) node() {}

func (*BooleanLiteral) node()         {}
func (*DateTimeLiteral) node()        {}
func (*DurationLiteral) node()        {}
func (*FloatLiteral) node()           {}
func (*IntegerLiteral) node()         {}
func (*PipeLiteral) node()            {}
func (*RegexpLiteral) node()          {}
func (*StringLiteral) node()          {}
func (*UnsignedIntegerLiteral) node() {}

func (*NamedType) node()      {}
func (*TvarType) node()       {}
func (*ArrayType) node()      {}
func (*DictType) node()       {}
func (*RecordType) node()     {}
func (*FunctionType) node()   {}
func (*PropertyType) node()   {}
func (*ParameterType) node()  {}
func (*TypeConstraint) node() {}
func (*TypeExpression) node() {}

// BaseNode holds the attributes every expression or statement should have
type BaseNode struct {
	Loc      *SourceLocation `json:"location,omitempty"`
	Errors   []Error         `json:"errors,omitempty"`
	Comments []Comment       `json:"comments,omitempty"`
}

// Location is the source location of the Node
func (b BaseNode) Location() SourceLocation {
	if b.Loc == nil {
		return SourceLocation{}
	}
	return *b.Loc
}

func (b BaseNode) Errs() []Error {
	return b.Errors
}

func (b BaseNode) CommentList() []Comment {
	return b.Comments
}

func (b BaseNode) Copy() BaseNode {
	// Note b is already shallow copy because of the non pointer receiver
	b.Loc = b.Loc.Copy()
	if len(b.Errors) > 0 {
		cpy := make([]Error, len(b.Errors))
		copy(cpy, b.Errors)
		b.Errors = cpy
	}
	return b
}

// Error represents an error in the AST construction.
// The node that this is attached to is not valid.
type Error struct {
	Msg string `json:"msg"`
}

func (e Error) Error() string {
	return e.Msg
}

type Comment struct {
	Text string `json:"text"`
}

type TypeExpression struct {
	BaseNode
	Ty          MonoType          `json:"monotype"`
	Constraints []*TypeConstraint `json:"constraints"`
}

type TypeConstraint struct {
	BaseNode
	Tvar  *Identifier   `json:"tvar"`
	Kinds []*Identifier `json:"kinds"`
}

func (TypeConstraint) Type() string {
	return "TypeConstraint"
}
func (c *TypeConstraint) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(TypeConstraint)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.Tvar = c.Tvar.Copy().(*Identifier)
	//nc.Kinds = c.Kinds.Copy().([]*Identifier)
	for k := range c.Kinds {
		nc.Kinds = append(nc.Kinds, c.Kinds[k])
	}
	return nc
}

func (TypeExpression) Type() string {
	return "TypeExpression"
}
func (c *TypeExpression) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(TypeExpression)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.Ty = c.Ty.Copy().(MonoType)
	for cnstr := range c.Constraints {
		nc.Constraints = append(nc.Constraints, c.Constraints[cnstr])
	}
	return nc
}

type MonoType interface {
	monotype()
	Node
}

func (NamedType) monotype()    {}
func (TvarType) monotype()     {}
func (ArrayType) monotype()    {}
func (DictType) monotype()     {}
func (RecordType) monotype()   {}
func (FunctionType) monotype() {}

type NamedType struct {
	BaseNode
	ID *Identifier `json:"name"`
}

func (NamedType) Type() string {
	return "NamedType"
}
func (nt *NamedType) Copy() Node {
	if nt == nil {
		return nt
	}
	nc := new(NamedType)
	*nc = *nt
	nc.BaseNode = nt.BaseNode.Copy()

	nc.ID = nt.ID.Copy().(*Identifier)
	return nc
}

type TvarType struct {
	BaseNode
	ID *Identifier `json:"name"`
}

func (c *TvarType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(TvarType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.ID = c.ID.Copy().(*Identifier)
	return nc
}
func (TvarType) Type() string {
	return "TvarType"
}

type ArrayType struct {
	BaseNode
	ElementType MonoType `json:"element"`
}

func (ArrayType) Type() string {
	return "ArrayType"
}
func (c *ArrayType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(ArrayType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.ElementType = c.ElementType.Copy().(*ArrayType)
	return nc
}

type DictType struct {
	BaseNode
	KeyType   MonoType `json:"key"`
	ValueType MonoType `json:"val"`
}

func (DictType) Type() string {
	return "DictType"
}
func (c *DictType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(DictType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.KeyType = c.KeyType.Copy().(MonoType)
	nc.ValueType = c.ValueType.Copy().(MonoType)
	return nc
}

type RecordType struct {
	BaseNode
	Properties []*PropertyType `json:"properties"`
	Tvar       *Identifier     `json:"tvar,omitempty"`
}

func (RecordType) Type() string {
	return "RecordType"
}
func (c *RecordType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(RecordType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	for p := range c.Properties {
		nc.Properties = append(nc.Properties, c.Properties[p])
	}
	nc.Tvar = c.Tvar.Copy().(*Identifier)
	return nc
}

type PropertyType struct {
	BaseNode
	Name *Identifier `json:"name"`
	Ty   MonoType    `json:"monotype"`
}

func (PropertyType) Type() string {
	return "PropertyType"
}
func (c *PropertyType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(PropertyType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.Name = c.Name.Copy().(*Identifier)
	nc.Ty = c.Ty.Copy().(MonoType)
	return nc
}

type FunctionType struct {
	BaseNode
	Parameters []*ParameterType `json:"parameters"`
	Return     MonoType         `json:"monotype"`
}

func (FunctionType) Type() string {
	return "FunctionType"
}
func (c *FunctionType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(FunctionType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	for param := range c.Parameters {
		_ = append(nc.Parameters, c.Parameters[param])
	}
	nc.Return = c.Return.Copy().(MonoType)

	return nc
}

type ParameterKind string

const (
	Required ParameterKind = "Required"
	Optional ParameterKind = "Optional"
	Pipe     ParameterKind = "Pipe"
)

type ParameterType struct {
	BaseNode
	Name *Identifier   `json:"name,omitempty"`
	Ty   MonoType      `json:"monotype"`
	Kind ParameterKind `json:"-"`
}

func (c *ParameterType) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(ParameterType)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.Name = c.Name.Copy().(*Identifier)
	nc.Ty = c.Ty.Copy().(MonoType)
	nc.Kind = c.Kind
	return nc
}
func (p *ParameterType) Type() string {
	return string(p.Kind)
}

// Package represents a complete package source tree
type Package struct {
	BaseNode
	Path    string  `json:"path,omitempty"`
	Package string  `json:"package"`
	Files   []*File `json:"files"`
}

// Type is the abstract type
func (*Package) Type() string { return "Package" }

func (p *Package) Copy() Node {
	if p == nil {
		return p
	}
	np := new(Package)
	*np = *p
	np.BaseNode = p.BaseNode.Copy()

	if len(p.Files) > 0 {
		np.Files = make([]*File, len(p.Files))
		for i, f := range p.Files {
			np.Files[i] = f.Copy().(*File)
		}
	}
	return np
}

// File represents a source from a single file
type File struct {
	BaseNode
	Name     string               `json:"name,omitempty"` // name of the file
	Metadata string               `json:"metadata,omitempty"`
	Package  *PackageClause       `json:"package"`
	Imports  []*ImportDeclaration `json:"imports"`
	Body     []Statement          `json:"body"`
	Eof      []Comment            `json:"eof,omitempty"`
}

// Type is the abstract type
func (*File) Type() string { return "File" }

func (f *File) Copy() Node {
	if f == nil {
		return f
	}
	nf := new(File)
	*nf = *f
	nf.BaseNode = f.BaseNode.Copy()

	nf.Package = f.Package.Copy().(*PackageClause)

	if len(f.Imports) > 0 {
		nf.Imports = make([]*ImportDeclaration, len(f.Imports))
		for i, s := range f.Imports {
			nf.Imports[i] = s.Copy().(*ImportDeclaration)
		}
	}

	if len(f.Body) > 0 {
		nf.Body = make([]Statement, len(f.Body))
		for i, s := range f.Body {
			nf.Body[i] = s.Copy().(Statement)
		}
	}
	return nf
}

// PackageClause defines the current package identifier.
type PackageClause struct {
	BaseNode
	Name *Identifier `json:"name"`
}

// Type is the abstract type
func (*PackageClause) Type() string { return "PackageClause" }

func (c *PackageClause) Copy() Node {
	if c == nil {
		return c
	}
	nc := new(PackageClause)
	*nc = *c
	nc.BaseNode = c.BaseNode.Copy()

	nc.Name = c.Name.Copy().(*Identifier)
	return nc
}

// ImportDeclaration declares a single import
type ImportDeclaration struct {
	BaseNode
	As   *Identifier    `json:"as"`
	Path *StringLiteral `json:"path"`
}

// Type is the abstract type
func (*ImportDeclaration) Type() string { return "ImportDeclaration" }

func (d *ImportDeclaration) Copy() Node {
	if d == nil {
		return d
	}
	nd := new(ImportDeclaration)
	*nd = *d
	nd.BaseNode = d.BaseNode.Copy()

	return nd
}

// Block is a set of statements
type Block struct {
	BaseNode
	Lbrace []Comment   `json:"lbrace,omitempty"`
	Body   []Statement `json:"body"`
	Rbrace []Comment   `json:"rbrace,omitempty"`
}

// Type is the abstract type
func (*Block) Type() string { return "Block" }

func (s *Block) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(Block)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	if len(s.Body) > 0 {
		ns.Body = make([]Statement, len(s.Body))
		for i, stmt := range s.Body {
			ns.Body[i] = stmt.Copy().(Statement)
		}
	}
	return ns
}

// Statement Perhaps we don't even want statements nor expression statements
type Statement interface {
	Node
	stmt()
}

func (*BadStatement) stmt()        {}
func (*VariableAssignment) stmt()  {}
func (*MemberAssignment) stmt()    {}
func (*ExpressionStatement) stmt() {}
func (*ReturnStatement) stmt()     {}
func (*OptionStatement) stmt()     {}
func (*BuiltinStatement) stmt()    {}
func (*TestStatement) stmt()       {}
func (*TestCaseStatement) stmt()   {}

type Assignment interface {
	Statement
	assignment()
}

func (*VariableAssignment) assignment() {}
func (*MemberAssignment) assignment()   {}

// BadStatement is a placeholder for statements for which no correct statement nodes
// can be created.
type BadStatement struct {
	BaseNode
	Text string `json:"text"`
}

// Type is the abstract type.
func (*BadStatement) Type() string { return "BadStatement" }

func (s *BadStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := *s
	ns.BaseNode = s.BaseNode.Copy()
	return &ns
}

// ExpressionStatement may consist of an expression that does not return a value and is executed solely for its side-effects.
type ExpressionStatement struct {
	BaseNode
	Expression Expression `json:"expression"`
}

// Type is the abstract type
func (*ExpressionStatement) Type() string { return "ExpressionStatement" }

func (s *ExpressionStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(ExpressionStatement)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	if s.Expression != nil {
		ns.Expression = s.Expression.Copy().(Expression)
	}

	return ns
}

// ReturnStatement defines an Expression to return
type ReturnStatement struct {
	BaseNode
	Argument Expression `json:"argument"`
}

// Type is the abstract type
func (*ReturnStatement) Type() string { return "ReturnStatement" }

func (s *ReturnStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(ReturnStatement)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	if s.Argument != nil {
		ns.Argument = s.Argument.Copy().(Expression)
	}

	return ns
}

// OptionStatement syntactically is a single variable declaration
type OptionStatement struct {
	BaseNode
	Assignment Assignment `json:"assignment"`
}

// Type is the abstract type
func (*OptionStatement) Type() string { return "OptionStatement" }

// Copy returns a deep copy of an OptionStatement Node
func (s *OptionStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(OptionStatement)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	if s.Assignment != nil {
		ns.Assignment = s.Assignment.Copy().(Assignment)
	}

	return ns
}

// BuiltinStatement declares a builtin identifier and its type
type BuiltinStatement struct {
	BaseNode
	Colon []Comment      `json:"colon,omitempty"`
	ID    *Identifier    `json:"id"`
	Ty    TypeExpression `json:"ty"`
}

// Type is the abstract type
func (*BuiltinStatement) Type() string { return "BuiltinStatement" }

// Copy returns a deep copy of an BuiltinStatement Node
func (s *BuiltinStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(BuiltinStatement)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	ns.ID = s.ID.Copy().(*Identifier)

	return ns
}

// TestStatement declares a Flux test case
type TestStatement struct {
	BaseNode
	Assignment *VariableAssignment `json:"assignment"`
}

// Type is the abstract type
func (*TestStatement) Type() string { return "TestStatement" }

// Copy returns a deep copy of a TestStatement Node
func (s *TestStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(TestStatement)
	*ns = *s
	ns.BaseNode = s.BaseNode.Copy()

	if s.Assignment != nil {
		ns.Assignment = s.Assignment.Copy().(*VariableAssignment)
	}

	return ns
}

// TestCaseStatement declares a Flux test case
type TestCaseStatement struct {
	BaseNode
	ID      *Identifier    `json:"id"`
	Extends *StringLiteral `json:"extends,omitempty"`
	Block   *Block         `json:"block"`
}

// Type is the abstract type
func (*TestCaseStatement) Type() string { return "TestCaseStatement" }

// Copy returns a deep copy of a TestCaseStatement Node
func (s *TestCaseStatement) Copy() Node {
	if s == nil {
		return s
	}
	ns := new(TestCaseStatement)
	ns.BaseNode = s.BaseNode.Copy()

	ns.ID = s.ID.Copy().(*Identifier)
	if s.Extends != nil {
		ns.Extends = s.Extends.Copy().(*StringLiteral)
	}
	ns.Block = s.Block.Copy().(*Block)
	return ns
}

// VariableAssignment represents the declaration of a variable
type VariableAssignment struct {
	BaseNode
	ID   *Identifier `json:"id"`
	Init Expression  `json:"init"`
}

// Type is the abstract type
func (*VariableAssignment) Type() string { return "VariableAssignment" }

func (d *VariableAssignment) Copy() Node {
	if d == nil {
		return d
	}
	nd := new(VariableAssignment)
	*nd = *d
	nd.BaseNode = d.BaseNode.Copy()

	if d.Init != nil {
		nd.Init = d.Init.Copy().(Expression)
	}

	return nd
}

type MemberAssignment struct {
	BaseNode
	Member *MemberExpression `json:"member"`
	Init   Expression        `json:"init"`
}

func (*MemberAssignment) Type() string { return "MemberAssignment" }

func (a *MemberAssignment) Copy() Node {
	if a == nil {
		return a
	}
	na := new(MemberAssignment)
	*na = *a
	na.BaseNode = a.BaseNode.Copy()

	if a.Member != nil {
		na.Member = a.Member.Copy().(*MemberExpression)
	}
	if a.Init != nil {
		na.Init = a.Init.Copy().(Expression)
	}

	return na
}

// Expression represents an action that can be performed by InfluxDB that can be evaluated to a value.
type Expression interface {
	Node
	expression()
}

func (*StringExpression) expression()       {}
func (*ParenExpression) expression()        {}
func (*ArrayExpression) expression()        {}
func (*DictExpression) expression()         {}
func (*FunctionExpression) expression()     {}
func (*BinaryExpression) expression()       {}
func (*BooleanLiteral) expression()         {}
func (*CallExpression) expression()         {}
func (*ConditionalExpression) expression()  {}
func (*DateTimeLiteral) expression()        {}
func (*DurationLiteral) expression()        {}
func (*FloatLiteral) expression()           {}
func (*Identifier) expression()             {}
func (*IntegerLiteral) expression()         {}
func (*LogicalExpression) expression()      {}
func (*MemberExpression) expression()       {}
func (*IndexExpression) expression()        {}
func (*ObjectExpression) expression()       {}
func (*PipeExpression) expression()         {}
func (*PipeLiteral) expression()            {}
func (*RegexpLiteral) expression()          {}
func (*StringLiteral) expression()          {}
func (*UnaryExpression) expression()        {}
func (*UnsignedIntegerLiteral) expression() {}

type StringExpression struct {
	BaseNode

	Parts []StringExpressionPart `json:"parts"`
}

func (*StringExpression) Type() string { return "StringExpression" }

func (e *StringExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(StringExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if len(e.Parts) > 0 {
		ne.Parts = make([]StringExpressionPart, len(e.Parts))
		for i, p := range e.Parts {
			ne.Parts[i] = p.Copy().(StringExpressionPart)
		}
	}

	return ne
}

type StringExpressionPart interface {
	Node
	stringPart()
}

func (*TextPart) stringPart()         {}
func (*InterpolatedPart) stringPart() {}

type TextPart struct {
	BaseNode
	Value string `json:"value"`
}

func (*TextPart) Type() string { return "TextPart" }

func (p *TextPart) Copy() Node {
	if p == nil {
		return p
	}
	np := new(TextPart)
	*np = *p
	np.BaseNode = p.BaseNode.Copy()
	return np
}

type InterpolatedPart struct {
	BaseNode
	Expression Expression `json:"expression"`
}

func (*InterpolatedPart) Type() string { return "InterpolatedPart" }

func (p *InterpolatedPart) Copy() Node {
	if p == nil {
		return p
	}
	np := new(InterpolatedPart)
	*np = *p
	np.BaseNode = p.BaseNode.Copy()

	if p.Expression != nil {
		np.Expression = p.Expression.Copy().(Expression)
	}
	return np
}

// ParenExpression represents an expressions that is wrapped in parentheses in the source code.
// It has no semantic meaning, rather it only communicates information about the syntax of the source code.
type ParenExpression struct {
	BaseNode
	Lparen     []Comment  `json:"lparen,omitempty"`
	Expression Expression `json:"expression"`
	Rparen     []Comment  `json:"rparen,omitempty"`
}

func (*ParenExpression) Type() string { return "ParenExpression" }

func (e *ParenExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(ParenExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Expression != nil {
		ne.Expression = e.Expression.Copy().(Expression)
	}
	return ne
}

// CallExpression represents a function call
type CallExpression struct {
	BaseNode
	Callee    Expression   `json:"callee"`
	Lparen    []Comment    `json:"lparen,omitempty"`
	Arguments []Expression `json:"arguments,omitempty"`
	Rparen    []Comment    `json:"rparen,omitempty"`
}

// Type is the abstract type
func (*CallExpression) Type() string { return "CallExpression" }

func (e *CallExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(CallExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Callee != nil {
		ne.Callee = e.Callee.Copy().(Expression)
	}

	if len(e.Arguments) > 0 {
		ne.Arguments = make([]Expression, len(e.Arguments))
		for i, arg := range e.Arguments {
			ne.Arguments[i] = arg.Copy().(Expression)
		}
	}

	return ne
}

type PipeExpression struct {
	BaseNode
	Argument Expression      `json:"argument"`
	Call     *CallExpression `json:"call"`
}

// Type is the abstract type
func (*PipeExpression) Type() string { return "PipeExpression" }

func (e *PipeExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(PipeExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Argument != nil {
		ne.Argument = e.Argument.Copy().(Expression)
	}
	ne.Call = e.Call.Copy().(*CallExpression)

	return ne
}

// MemberExpression represents calling a property of a CallExpression
type MemberExpression struct {
	BaseNode
	Object   Expression  `json:"object"`
	Lbrack   []Comment   `json:"lbrack,omitempty"`
	Property PropertyKey `json:"property"`
	Rbrack   []Comment   `json:"rbrack,omitempty"`
}

// Type is the abstract type
func (*MemberExpression) Type() string { return "MemberExpression" }

func (e *MemberExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(MemberExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Object != nil {
		ne.Object = e.Object.Copy().(Expression)
	}
	if e.Property != nil {
		ne.Property = e.Property.Copy().(PropertyKey)
	}

	return ne
}

// IndexExpression represents indexing into an array
type IndexExpression struct {
	BaseNode
	Array  Expression `json:"array"`
	Lbrack []Comment  `json:"lbrack,omitempty"`
	Index  Expression `json:"index"`
	Rbrack []Comment  `json:"rbrack,omitempty"`
}

func (*IndexExpression) Type() string { return "IndexExpression" }

func (e *IndexExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(IndexExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Array != nil {
		ne.Array = e.Array.Copy().(Expression)
	}
	if e.Index != nil {
		ne.Index = e.Index.Copy().(Expression)
	}
	return ne
}

type FunctionExpression struct {
	BaseNode
	Lparen []Comment   `json:"lparen,omitempty"`
	Params []*Property `json:"params"`
	Rparan []Comment   `json:"rparen,omitempty"`
	Arrow  []Comment   `json:"arrow,omitempty"`
	Body   Node        `json:"body"`
}

// Type is the abstract type
func (*FunctionExpression) Type() string { return "FunctionExpression" }

func (e *FunctionExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(FunctionExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if len(e.Params) > 0 {
		ne.Params = make([]*Property, len(e.Params))
		for i, param := range e.Params {
			ne.Params[i] = param.Copy().(*Property)
		}
	}

	if e.Body != nil {
		ne.Body = e.Body.Copy()
	}

	return ne
}

// OperatorKind are Equality and Arithmatic operators.
// Result of evaluating an equality operator is always of type Boolean based on whether the
// comparison is true
// Arithmetic operators take numerical values (either literals or variables) as their operands
//  and return a single numerical value.
type OperatorKind int

const (
	opBegin OperatorKind = iota
	MultiplicationOperator
	DivisionOperator
	ModuloOperator
	PowerOperator
	AdditionOperator
	SubtractionOperator
	LessThanEqualOperator
	LessThanOperator
	GreaterThanEqualOperator
	GreaterThanOperator
	StartsWithOperator
	InOperator
	NotOperator
	ExistsOperator
	NotEmptyOperator
	EmptyOperator
	EqualOperator
	NotEqualOperator
	RegexpMatchOperator
	NotRegexpMatchOperator
	opEnd
)

func (o OperatorKind) String() string {
	return OperatorTokens[o]
}

// OperatorLookup converts the operators to OperatorKind
func OperatorLookup(op string) OperatorKind {
	return operators[op]
}

func (o OperatorKind) MarshalText() ([]byte, error) {
	text, ok := OperatorTokens[o]
	if !ok {
		return nil, fmt.Errorf("unknown operator %d", int(o))
	}
	return []byte(text), nil
}
func (o *OperatorKind) UnmarshalText(data []byte) error {
	var ok bool
	*o, ok = operators[string(data)]
	if !ok {
		return fmt.Errorf("unknown operator %q", string(data))
	}
	return nil
}

// BinaryExpression use binary operators act on two operands in an expression.
// BinaryExpression includes relational and arithmetic operators
type BinaryExpression struct {
	BaseNode
	Operator OperatorKind `json:"operator"`
	Left     Expression   `json:"left"`
	Right    Expression   `json:"right"`
}

// Type is the abstract type
func (*BinaryExpression) Type() string { return "BinaryExpression" }

func (e *BinaryExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(BinaryExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Left != nil {
		ne.Left = e.Left.Copy().(Expression)
	}
	if e.Right != nil {
		ne.Right = e.Right.Copy().(Expression)
	}

	return ne
}

// UnaryExpression use operators act on a single operand in an expression.
type UnaryExpression struct {
	BaseNode
	Operator OperatorKind `json:"operator"`
	Argument Expression   `json:"argument"`
}

// Type is the abstract type
func (*UnaryExpression) Type() string { return "UnaryExpression" }

func (e *UnaryExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(UnaryExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Argument != nil {
		ne.Argument = e.Argument.Copy().(Expression)
	}

	return ne
}

// LogicalOperatorKind are used with boolean (logical) values
type LogicalOperatorKind int

const (
	logOpBegin LogicalOperatorKind = iota
	AndOperator
	OrOperator
	logOpEnd
)

func (o LogicalOperatorKind) String() string {
	return LogicalOperatorTokens[o]
}

// LogicalOperatorLookup converts the operators to LogicalOperatorKind
func LogicalOperatorLookup(op string) LogicalOperatorKind {
	return logOperators[op]
}

func (o LogicalOperatorKind) MarshalText() ([]byte, error) {
	text, ok := LogicalOperatorTokens[o]
	if !ok {
		return nil, fmt.Errorf("unknown logical operator %d", int(o))
	}
	return []byte(text), nil
}

func (o *LogicalOperatorKind) UnmarshalText(data []byte) error {
	var ok bool
	*o, ok = logOperators[string(data)]
	if !ok {
		return fmt.Errorf("unknown logical operator %q", string(data))
	}
	return nil
}

// LogicalExpression represent the rule conditions that collectively evaluate to either true or false.
// `or` expressions compute the disjunction of two boolean expressions and return boolean values.
// `and`` expressions compute the conjunction of two boolean expressions and return boolean values.
type LogicalExpression struct {
	BaseNode
	Operator LogicalOperatorKind `json:"operator"`
	Left     Expression          `json:"left"`
	Right    Expression          `json:"right"`
}

// Type is the abstract type
func (*LogicalExpression) Type() string { return "LogicalExpression" }

func (e *LogicalExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(LogicalExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Left != nil {
		ne.Left = e.Left.Copy().(Expression)
	}
	if e.Right != nil {
		ne.Right = e.Right.Copy().(Expression)
	}

	return ne
}

// ArrayExpr is used to create and directly specify the elements of an array object
type ArrayItem struct {
	Expression
	Comma []Comment `json:"comma,omitempty"`
}

// ArrayExpression is used to create and directly specify the elements of an array object
type ArrayExpression struct {
	BaseNode
	Lbrack   []Comment    `json:"lbrack,omitempty"`
	Elements []Expression `json:"elements"`
	Rbrack   []Comment    `json:"rbrack,omitempty"`
}

// Type is the abstract type
func (*ArrayExpression) Type() string { return "ArrayExpression" }

func (e *ArrayExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(ArrayExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if len(e.Elements) > 0 {
		ne.Elements = make([]Expression, len(e.Elements))
		for i, el := range e.Elements {
			ne.Elements[i] = el.Copy().(Expression)
		}
	}

	return ne
}

// DictExpression represents dictionary literals
type DictExpression struct {
	BaseNode
	Lbrack   []Comment   `json:"lbrack,omitempty"`
	Elements []*DictItem `json:"elements"`
	Rbrack   []Comment   `json:"rbrack,omitempty"`
}

// Type is the abstract type
func (*DictExpression) Type() string { return "DictExpression" }

func (e *DictExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(DictExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if len(e.Elements) > 0 {
		ne.Elements = make([]*DictItem, len(e.Elements))
		for i, item := range e.Elements {
			ne.Elements[i] = &DictItem{
				Key: item.Key.Copy().(Expression),
				Val: item.Val.Copy().(Expression),
			}
		}
	}

	return ne
}

// DictItem represents a key value pair of a dictionary literal
type DictItem struct {
	Key   Expression `json:"key"`
	Val   Expression `json:"val"`
	Comma []Comment  `json:"comma,omitempty"`
}

func (*DictItem) Type() string { return "DictItem" }

type WithSource struct {
	Source *Identifier `json:"source"`
	With   []Comment   `json:"with,omitempty"`
}

// ObjectExpression allows the declaration of an anonymous object within a declaration.
type ObjectExpression struct {
	BaseNode
	Lbrace     []Comment   `json:"lbrace,omitempty"`
	With       *Identifier `json:"with,omitempty"`
	Properties []*Property `json:"properties"`
	Rbrace     []Comment   `json:"rbrace,omitempty"`
}

// Type is the abstract type
func (*ObjectExpression) Type() string { return "ObjectExpression" }

func (e *ObjectExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(ObjectExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if len(e.Properties) > 0 {
		ne.Properties = make([]*Property, len(e.Properties))
		for i, p := range e.Properties {
			ne.Properties[i] = p.Copy().(*Property)
		}
	}

	return ne
}

// ConditionalExpression selects one of two expressions, `Alternate` or `Consequent`
// depending on a third, boolean, expression, `Test`.
type ConditionalExpression struct {
	BaseNode
	Tk_if      []Comment  `json:"tk_if,omitempty"`
	Test       Expression `json:"test"`
	Tk_then    []Comment  `json:"tk_then,omitempty"`
	Consequent Expression `json:"consequent"`
	Tk_else    []Comment  `json:"tk_else,omitempty"`
	Alternate  Expression `json:"alternate"`
}

// Type is the abstract type
func (*ConditionalExpression) Type() string { return "ConditionalExpression" }

func (e *ConditionalExpression) Copy() Node {
	if e == nil {
		return e
	}
	ne := new(ConditionalExpression)
	*ne = *e
	ne.BaseNode = e.BaseNode.Copy()

	if e.Test != nil {
		ne.Test = e.Test.Copy().(Expression)
	}
	if e.Alternate != nil {
		ne.Alternate = e.Alternate.Copy().(Expression)
	}
	if e.Consequent != nil {
		ne.Consequent = e.Consequent.Copy().(Expression)
	}
	return ne
}

// PropertyKey represents an object key
type PropertyKey interface {
	Node
	Key() string
}

// Property is the value associated with a key.
// A property's key can be either an identifier or string literal.
type Property struct {
	BaseNode
	Key       PropertyKey `json:"key"`
	Separator []Comment   `json:"separator,omitempty"`
	Value     Expression  `json:"value"`
	Comma     []Comment   `json:"comma,omitempty"`
}

func (p *Property) Copy() Node {
	if p == nil {
		return p
	}
	np := new(Property)
	*np = *p
	np.BaseNode = p.BaseNode.Copy()

	if p.Value != nil {
		np.Value = p.Value.Copy().(Expression)
	}

	return np
}

// Type is the abstract type
func (*Property) Type() string { return "Property" }

// Identifier represents a name that identifies a unique Node
type Identifier struct {
	BaseNode
	Name string `json:"name"`
}

// Identifiers are valid object keys
func (i *Identifier) Key() string {
	return i.Name
}

// Type is the abstract type
func (*Identifier) Type() string { return "Identifier" }

func (i *Identifier) Copy() Node {
	if i == nil {
		return i
	}
	ni := new(Identifier)
	*ni = *i
	ni.BaseNode = i.BaseNode.Copy()

	return ni
}

// Literal is the lexical form for a literal expression which defines
// boolean, string, integer, number, duration, datetime or field values.
// Literals must be coerced explicitly.
type Literal interface {
	Expression
	literal()
}

func (*BooleanLiteral) literal()         {}
func (*DateTimeLiteral) literal()        {}
func (*DurationLiteral) literal()        {}
func (*FloatLiteral) literal()           {}
func (*IntegerLiteral) literal()         {}
func (*PipeLiteral) literal()            {}
func (*RegexpLiteral) literal()          {}
func (*StringLiteral) literal()          {}
func (*UnsignedIntegerLiteral) literal() {}

// PipeLiteral represents an specialized literal value, indicating the left hand value of a pipe expression.
type PipeLiteral struct {
	BaseNode
}

// Type is the abstract type
func (*PipeLiteral) Type() string { return "PipeLiteral" }

func (p *PipeLiteral) Copy() Node {
	if p == nil {
		return p
	}
	np := new(PipeLiteral)
	*np = *p
	np.BaseNode = p.BaseNode.Copy()
	return np
}

// StringLiteral expressions begin and end with double quote marks.
type StringLiteral struct {
	BaseNode
	// Value is the unescaped value of the string literal
	Value string `json:"value"`
}

// StringLiterals are valid object keys
func (l *StringLiteral) Key() string {
	return l.Value
}

func (*StringLiteral) Type() string { return "StringLiteral" }

func (l *StringLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(StringLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// BooleanLiteral represent boolean values
type BooleanLiteral struct {
	BaseNode
	Value bool `json:"value"`
}

// Type is the abstract type
func (*BooleanLiteral) Type() string { return "BooleanLiteral" }

func (l *BooleanLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(BooleanLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// FloatLiteral  represent floating point numbers according to the double representations defined by the IEEE-754-1985
type FloatLiteral struct {
	BaseNode
	Value float64 `json:"value"`
}

// Type is the abstract type
func (*FloatLiteral) Type() string { return "FloatLiteral" }

func (l *FloatLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(FloatLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// IntegerLiteral represent integer numbers.
type IntegerLiteral struct {
	BaseNode
	Value int64 `json:"value"`
}

// Type is the abstract type
func (*IntegerLiteral) Type() string { return "IntegerLiteral" }

func (l *IntegerLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(IntegerLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// UnsignedIntegerLiteral represent integer numbers.
type UnsignedIntegerLiteral struct {
	BaseNode
	Value uint64 `json:"value"`
}

// Type is the abstract type
func (*UnsignedIntegerLiteral) Type() string { return "UnsignedIntegerLiteral" }

func (l *UnsignedIntegerLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(UnsignedIntegerLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// RegexpLiteral expressions begin and end with `/` and are regular expressions with syntax accepted by RE2
type RegexpLiteral struct {
	BaseNode
	Value *regexp.Regexp `json:"value"`
}

// Type is the abstract type
func (*RegexpLiteral) Type() string { return "RegexpLiteral" }

func (l *RegexpLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(RegexpLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()

	if l.Value != nil {
		nl.Value = l.Value
	}
	return nl
}

// Duration is a pair consisting of length of time and the unit of time measured.
// It is the atomic unit from which all duration literals are composed.
type Duration struct {
	Magnitude int64  `json:"magnitude"`
	Unit      string `json:"unit"`
}

// toDuration returns a time.Duration corresponding to Duration.  It is an approximation, as months, etc
// can't be properly figured out without knowing the time from when.
// This may have to be modified to also accept a time.Time to make this exact.
func toDuration(l Duration) (time.Duration, error) {
	// TODO: This is temporary code until we have proper duration type that takes different months, DST, etc into account
	var dur time.Duration
	var err error
	mag := l.Magnitude
	unit := l.Unit

	switch unit {
	case "y":
		mag *= 12
		unit = "mo"
		fallthrough
	case "mo":
		const weeksPerMonth = 365.25 / 12 / 7
		mag = int64(float64(mag) * weeksPerMonth)
		unit = "w"
		fallthrough
	case "w":
		mag *= 7
		unit = "d"
		fallthrough
	case "d":
		mag *= 24
		unit = "h"
		fallthrough
	default:
		// ParseDuration will handle h, m, s, ms, us, ns.
		dur, err = time.ParseDuration(strconv.FormatInt(mag, 10) + unit)
	}
	return dur, err
}

const (
	NanosecondUnit  = "ns"
	MicrosecondUnit = "us"
	MillisecondUnit = "ms"
	SecondUnit      = "s"
	MinuteUnit      = "m"
	HourUnit        = "h"
	DayUnit         = "d"
	WeekUnit        = "w"
	MonthUnit       = "mo"
	YearUnit        = "y"
)

// DurationLiteral represents the elapsed time between two instants as an
// int64 nanosecond count with syntax of golang's time.Duration
// TODO: this may be better as a class initialization
type DurationLiteral struct {
	BaseNode
	Values []Duration `json:"values"`
}

// Type is the abstract type
func (*DurationLiteral) Type() string { return "DurationLiteral" }

func (l *DurationLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(DurationLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()

	if len(l.Values) > 0 {
		nl.Values = make([]Duration, len(l.Values))
		copy(nl.Values, l.Values)
	}
	return nl
}

// Duration gives you a DurationLiteral from a time.Duration.
// Currently this is an approximation, but since we accept time, it can be made exact.
// TODO: makes this exact and not an approximation.
// currently the time.Time is ignored
func DurationFrom(l *DurationLiteral, _ time.Time) (time.Duration, error) {
	var d time.Duration
	for i := range l.Values {
		tempD, err := toDuration(l.Values[i])
		if err != nil {
			return 0, err
		}
		d += tempD
	}
	return d, nil
}

// TODO: we need a "duration from" that takes a time and a durationliteral, and gives an exact time.Duration instead of an approximation

// DateTimeLiteral represents an instant in time with nanosecond precision using
// the syntax of golang's RFC3339 Nanosecond variant
// TODO: this may be better as a class initialization
type DateTimeLiteral struct {
	BaseNode
	Value time.Time `json:"value"`
}

// Type is the abstract type
func (*DateTimeLiteral) Type() string { return "DateTimeLiteral" }

func (l *DateTimeLiteral) Copy() Node {
	if l == nil {
		return l
	}
	nl := new(DateTimeLiteral)
	*nl = *l
	nl.BaseNode = l.BaseNode.Copy()
	return nl
}

// OperatorTokens converts OperatorKind to string
var OperatorTokens = map[OperatorKind]string{
	MultiplicationOperator:   "*",
	DivisionOperator:         "/",
	ModuloOperator:           "%",
	PowerOperator:            "^",
	AdditionOperator:         "+",
	SubtractionOperator:      "-",
	LessThanEqualOperator:    "<=",
	LessThanOperator:         "<",
	GreaterThanOperator:      ">",
	GreaterThanEqualOperator: ">=",
	InOperator:               "in",
	NotOperator:              "not",
	ExistsOperator:           "exists",
	NotEmptyOperator:         "not empty",
	EmptyOperator:            "empty",
	StartsWithOperator:       "startswith",
	EqualOperator:            "==",
	NotEqualOperator:         "!=",
	RegexpMatchOperator:      "=~",
	NotRegexpMatchOperator:   "!~",
}

// LogicalOperatorTokens converts LogicalOperatorKind to string
var LogicalOperatorTokens = map[LogicalOperatorKind]string{
	AndOperator: "and",
	OrOperator:  "or",
}

var operators map[string]OperatorKind
var logOperators map[string]LogicalOperatorKind

func init() {
	operators = make(map[string]OperatorKind)
	for op := opBegin + 1; op < opEnd; op++ {
		operators[OperatorTokens[op]] = op
	}

	logOperators = make(map[string]LogicalOperatorKind)
	for op := logOpBegin + 1; op < logOpEnd; op++ {
		logOperators[LogicalOperatorTokens[op]] = op
	}
}