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parser.go
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parser.go
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// Package fiqlparser provides a simple fiql parser.
//
// The parser does not adhere 100% to the fiql spec
// which can be found https://datatracker.ietf.org/doc/html/draft-nottingham-atompub-fiql-00.
//
// The parser produces a walkable AST which can be walked by using a visitor.
package fiqlparser
import (
"encoding/json"
"fmt"
"regexp"
"strconv"
"strings"
"time"
)
// NodeType defines the type of node in the ast
type NodeType string
// NodeTypeExpression is the root element of any expression
const NodeTypeExpression NodeType = "Expr"
// NodeTypeBinary is a binary expression
const NodeTypeBinary NodeType = "Binary"
// NodeTypeConstant is a constant value expression
const NodeTypeConstant NodeType = "Const"
// OperatorDefintion defines the two operators fiql has
type OperatorDefintion string
// OperatorOR defines the OR operation
// Associativity: Left to right
const OperatorOR OperatorDefintion = "OR"
// OperatorAND defines the AND operation
// Associativity: Left to right
const OperatorAND OperatorDefintion = "AND"
// ComparisonDefintion defines the fiql + custom comparisons
type ComparisonDefintion string
// ComparisonEq equal comparison
const ComparisonEq ComparisonDefintion = "=="
// ComparisonNeq not equal comparison
const ComparisonNeq ComparisonDefintion = "<>"
// ComparisonGt greater comparison
const ComparisonGt ComparisonDefintion = ">"
// ComparisonLt less comparison
const ComparisonLt ComparisonDefintion = "<"
// ComparisonGte greater or equal comparison
const ComparisonGte ComparisonDefintion = ">="
// ComparisonLte less or equal comparison
const ComparisonLte ComparisonDefintion = "<="
// ValueRecommendation suggests a detected datatype for a attribute
type ValueRecommendation string
// ValueRecommendationString suggests a string attribute
const ValueRecommendationString ValueRecommendation = "string"
// ValueRecommendationDateTime suggests a date attribute
const ValueRecommendationDateTime ValueRecommendation = "datetime"
// ValueRecommendationDuration suggests a duration attribute
const ValueRecommendationDuration ValueRecommendation = "duration"
// ValueRecommendationNumber suggests a number attribute
const ValueRecommendationNumber ValueRecommendation = "number"
// ArgumentContext habours the value and
// supplies the recommended type + conversion helpers
type ArgumentContext struct {
pre bool
post bool
r ValueRecommendation
val string
}
// ValueRecommendation returns the value recommendation
func (c ArgumentContext) ValueRecommendation() ValueRecommendation {
return c.r
}
// StartsWithWildcard indicates whether or not the given argument starts with a wildcard
func (c ArgumentContext) StartsWithWildcard() bool {
return c.pre
}
// EndsWithWildcard indicates whether or not the given argument ends with a wildcard
func (c ArgumentContext) EndsWithWildcard() bool {
return c.post
}
// AsString returns the argument as string
func (c ArgumentContext) AsString() string {
return c.val
}
// AsDuration is a helper method for converting duration values
func (c ArgumentContext) AsDuration() (ISO8601Duration, error) {
return durationConverter.tryParseISO8601Duration(c.val)
}
// AsTime is a helper method for converting duration values
func (c ArgumentContext) AsTime() (time.Time, error) {
return time.Parse(time.RFC3339, c.val)
}
// AsInt returns the underlying value as int
func (c ArgumentContext) AsInt() (int, error) {
return strconv.Atoi(c.val)
}
// AsFloat64 returns the underlying value as float64
func (c ArgumentContext) AsFloat64() (float64, error) {
return strconv.ParseFloat(c.val, 64)
}
// SelectorContext contains the selector details
type SelectorContext struct {
unary bool
selector string
}
// Selector returns the selector as string
func (s SelectorContext) Selector() string {
return s.selector
}
// IsUnary returns true if the selector has no constraint
func (s SelectorContext) IsUnary() bool {
return s.unary
}
// OperatorContext contains the operator details
type OperatorContext struct {
op OperatorDefintion
}
// Operator returns the operator
func (c OperatorContext) Operator() OperatorDefintion {
return c.op
}
// ComparisonContext contains the comerator details
type ComparisonContext struct {
comparison ComparisonDefintion
}
// Comparison returns the used comparison
func (c ComparisonContext) Comparison() ComparisonDefintion {
return c.comparison
}
//Basically follow naming of https://datatracker.ietf.org/doc/html/draft-nottingham-atompub-fiql-00#section-3.2
// NodeVisitor is used to visit the tree
type NodeVisitor interface {
// VisitExpressionEntered is called when a expression is entered
VisitExpressionEntered()
// VisitExpressionLeft is called when a expression is left
VisitExpressionLeft()
// VisitOperator is called when a operator is visited
VisitOperator(operatorCtx OperatorContext)
// VisitSelector is called when a selector is visited
VisitSelector(selectorCtx SelectorContext)
// VisitComparison is called when a comparison is visited
VisitComparison(comparisonCtx ComparisonContext)
// VisitArgument is called when a argument is visited
VisitArgument(argumentCtx ArgumentContext)
}
// Node represents a AST node
type Node interface {
// NodeType - node type in the AST - the root node will always be expression
NodeType() NodeType
// String prints the node
String() string
// Returns the children of this node
Children() []Node
// Accepts a Visitor
Accept(visitor NodeVisitor)
// Add adds a child node to this node
Add(Node)
// isRoot indicates the root node
isRoot() bool
}
// Expression is the root node
type Expression struct {
node Node
root bool
}
func (e *Expression) isRoot() bool {
return e.root
}
// NodeType NodeTypeExpression
func (e *Expression) NodeType() NodeType {
return NodeTypeExpression
}
// Accept accepts a vistor to visit the tree
func (e *Expression) Accept(visitor NodeVisitor) {
visitor.VisitExpressionEntered()
if e.node != nil {
e.node.Accept(visitor)
}
visitor.VisitExpressionLeft()
}
// Add adds a child to the node, it will panic if more than one child exists on a expression node
func (e *Expression) Add(node Node) {
if e.node != nil {
panic("node may not have more than one child")
}
e.node = node
}
// MarshalJSON overloading for json marshalling
func (e *Expression) MarshalJSON() ([]byte, error) {
j, err := json.Marshal(struct {
Type string
Operator string
Nodes []Node
}{
Type: string(e.NodeType()),
Nodes: []Node{e.node},
})
if err != nil {
return nil, err
}
return j, nil
}
func (e *Expression) String() string {
var b strings.Builder
b.WriteRune('(')
for _, v := range e.Children() {
b.WriteString(v.String())
}
b.WriteRune(')')
return b.String()
}
// Children returns the children of this expression
func (e *Expression) Children() []Node {
return []Node{e.node}
}
type binaryExpression struct {
operator string
nodes [2]Node
}
func (e *binaryExpression) NodeType() NodeType {
return NodeTypeBinary
}
func (e *binaryExpression) Add(node Node) {
if e.nodes[0] == nil {
e.nodes[0] = node
return
}
if e.nodes[1] == nil {
e.nodes[1] = node
return
}
panic("binary node cant hold more than two values")
}
// Accept accepts a vistor to visit the tree
func (e *binaryExpression) Accept(visitor NodeVisitor) {
if e.nodes[0] != nil {
e.nodes[0].Accept(visitor)
}
//conjs
if e.operator == "AND" || e.operator == "OR" {
visitor.VisitOperator(OperatorContext{op: OperatorDefintion(e.operator)})
} else {
visitor.VisitComparison(ComparisonContext{comparison: ComparisonDefintion(e.operator)})
}
if e.nodes[1] != nil {
e.nodes[1].Accept(visitor)
}
}
func (e *binaryExpression) Children() []Node {
nodes := make([]Node, 0)
if e.nodes[0] != nil {
nodes = append(nodes, e.nodes[0])
}
if e.nodes[1] != nil {
nodes = append(nodes, e.nodes[1])
}
return nodes
}
func (e *binaryExpression) isRoot() bool {
return false
}
func (e *binaryExpression) MarshalJSON() ([]byte, error) {
j, err := json.Marshal(struct {
Type string
Operator string
Nodes [2]Node
}{
Type: string(e.NodeType()),
Operator: e.operator,
Nodes: e.nodes,
})
if err != nil {
return nil, err
}
return j, nil
}
func (e *binaryExpression) String() string {
var b strings.Builder
if e.nodes[0] != nil {
b.WriteString(e.nodes[0].String())
}
b.WriteRune(' ')
b.WriteString(e.operator)
b.WriteRune(' ')
if e.nodes[1] != nil {
b.WriteString(e.nodes[1].String())
}
return b.String()
}
type constantExpression struct {
prefixWildcard bool
suffixWildcard bool
selector bool
value string
recommended ValueRecommendation
unary bool
}
func (e *constantExpression) isRoot() bool {
return false
}
func (e *constantExpression) NodeType() NodeType {
return NodeTypeConstant
}
func (e *constantExpression) Add(node Node) {
panic("constant should not have a child")
}
func (e *constantExpression) Accept(visitor NodeVisitor) {
if e.selector {
visitor.VisitSelector(SelectorContext{unary: e.unary, selector: e.value})
} else {
visitor.VisitArgument(ArgumentContext{
pre: e.prefixWildcard,
post: e.suffixWildcard,
r: e.recommended,
val: e.value,
})
}
}
func (e *constantExpression) MarshalJSON() ([]byte, error) {
j, err := json.Marshal(struct {
Type string
Value string
}{
Type: string(e.NodeType()),
Value: e.String(),
})
if err != nil {
return nil, err
}
return j, nil
}
func (e *constantExpression) String() string {
var b strings.Builder
if e.prefixWildcard {
b.WriteRune('*')
}
b.WriteString(e.value)
if e.suffixWildcard {
b.WriteRune('*')
}
return b.String()
}
func (e *constantExpression) Children() []Node {
return []Node{}
}
// Parser is the fiql parser
type Parser struct {
lex *lexer
}
func (p *Parser) handleSubExpression(parent Node) (Node, error) {
expr := &Expression{node: nil}
n, err := p.build(expr)
if err != nil {
return expr, err
}
expr.node = n
return expr, nil
}
var numericRegex = regexp.MustCompile(`^(\+|-|)[0-9\.]+$`)
var durationRegex = regexp.MustCompile(`^(\+|-|)P(?:\d+(?:\.\d+)?Y)?(?:\d+(?:\.\d+)?M)?(?:\d+(?:\.\d+)?W)?(?:\d+(?:\.\d+)?D)?(?:T(?:\d+(?:\.\d+)?H)?(?:\d+(?:\.\d+)?M)?(?:\d+(?:\.\d+)?S)?)?$`)
func isDateValue(stringDate string) bool {
_, err := time.Parse(time.RFC3339, stringDate)
return err == nil
}
type argumentValidator func(string) (bool, ValueRecommendation, string)
func numberOrDateExpressionValidator(i string) (bool, ValueRecommendation, string) {
if numericRegex.MatchString(i) {
return true, ValueRecommendationNumber, ""
}
//time or duration e.g. 2003-12-13T18:30:02Z or -P1D12
if isDateValue(i) {
return true, ValueRecommendationDateTime, ""
}
if durationRegex.MatchString(i) {
return true, ValueRecommendationDuration, ""
}
return false, ValueRecommendationString, "number or date or duration"
}
func defaultValidator(i string) (bool, ValueRecommendation, string) {
if isDateValue(i) {
return true, ValueRecommendationDateTime, ""
}
if durationRegex.MatchString(i) {
return true, ValueRecommendationDuration, ""
}
if numericRegex.MatchString(i) {
return true, ValueRecommendationNumber, ""
}
return true, ValueRecommendationString, ""
}
func (p *Parser) handleArgumentConstant(validator argumentValidator) (Node, error) {
t, err := p.lex.ConsumeToken()
if err != nil {
return nil, err
}
prefixWildcard := false
if t == tokenWildcard {
t, err = p.lex.ConsumeToken()
if err != nil {
return nil, err
}
prefixWildcard = true
}
if t == tokenValue {
ok, rec, msg := validator(p.lex.lastValue())
if !ok {
return nil, fmt.Errorf("ln:%d:%d syntax error (got `%s` but expected %s)", p.lex.ln, p.lex.posInLine, p.lex.lastValue(), msg)
}
con := &constantExpression{prefixWildcard: prefixWildcard, value: p.lex.lastValue(), recommended: rec}
n, _, err := p.lex.PeekNextToken()
if err != nil {
return nil, err
}
if n == tokenWildcard {
_, err = p.lex.ConsumeToken()
if err != nil {
return nil, err
}
con.suffixWildcard = true
}
return con, nil
}
return nil, fmt.Errorf("ln:%d:%d syntax error (got `%s` but expected a value)", p.lex.ln, p.lex.posInLine, t.String())
}
func (p Parser) handleUnaryExpression(parent Node) (Node, error) {
unary := &constantExpression{value: p.lex.lastValue(), selector: true, recommended: ValueRecommendationString, unary: true}
next, _, err := p.lex.PeekNextToken()
if err != nil {
return unary, err
}
if isLogicToken(next) {
t, err := p.lex.ConsumeToken()
if err != nil {
return unary, err
}
conj := &binaryExpression{nodes: [2]Node{nil, nil}}
conj.operator = t.String()
conj.Add(unary)
rhs, err := p.build(conj)
if err != nil {
return conj, err
}
conj.Add(rhs)
return conj, nil
}
if isCompareToken(next) {
return unary, fmt.Errorf("ln:%d:%d dangling comparator", p.lex.ln, p.lex.posInLine)
}
if next == tokenBraceClose && parent.isRoot() {
return unary, fmt.Errorf("ln:%d:%d syntax error (invalid closing brace `)` )", p.lex.ln, p.lex.posInLine)
}
return unary, nil
}
func (p *Parser) handleBinaryExpression(t tokenType, parent Node) (Node, error) {
bin := &binaryExpression{nodes: [2]Node{nil, nil}}
bin.operator = t.String()
bin.Add(&constantExpression{value: p.lex.lastValue(), selector: true, recommended: ValueRecommendationString})
t, err := p.lex.ConsumeToken()
if err != nil {
return bin, err
}
if isCompareToken(t) {
bin.operator = t.String()
} else {
return bin, fmt.Errorf("ln:%d:%d syntax error (got `%s` but expected a value)", p.lex.ln, p.lex.posInLine, t.String())
}
validator := defaultValidator
if isNumberOrDateComparision(t) {
validator = numberOrDateExpressionValidator
}
con, err := p.handleArgumentConstant(validator)
if err != nil {
return bin, err
}
bin.Add(con)
next, _, err := p.lex.PeekNextToken()
if err != nil {
return bin, err
}
if isLogicToken(next) {
t, err = p.lex.ConsumeToken()
if err != nil {
return bin, err
}
conj := &binaryExpression{nodes: [2]Node{nil, nil}}
conj.operator = t.String()
conj.Add(bin)
rhs, err := p.build(conj)
if err != nil {
return conj, err
}
conj.Add(rhs)
return conj, nil
}
if isCompareToken(next) {
return bin, fmt.Errorf("ln:%d:%d dangling comparator", p.lex.ln, p.lex.posInLine)
}
if next == tokenBraceClose && parent.isRoot() {
return bin, fmt.Errorf("ln:%d:%d syntax error (invalid closing brace `)` )", p.lex.ln, p.lex.posInLine)
}
return bin, nil
}
func (p *Parser) checkDanglingChild(n Node) bool {
if n.NodeType() == NodeTypeBinary {
if len(n.Children()) != 2 {
return true
}
}
return false
}
// checkImpossibleTokensOnEnter checks for tokens that should not appear on enter `build`
func (p *Parser) checkImpossibleTokensOnEnter(t tokenType) error {
if t == tokenBraceClose {
return fmt.Errorf("ln:%d:%d syntax error (invalid closing brace `)` )", p.lex.ln, p.lex.posInLine)
}
if isLogicToken(t) {
return fmt.Errorf("ln:%d:%d dangling operator", p.lex.ln, p.lex.posInLine)
}
if isCompareToken(t) {
return fmt.Errorf("ln:%d:%d dangling comparator", p.lex.ln, p.lex.posInLine)
}
return nil
}
// checkForEOF checks for correct end of file
func (p *Parser) checkForEOF(t tokenType, node Node) (bool, error) {
if t == tokenEOF {
if p.checkDanglingChild(node) {
return true, fmt.Errorf("ln:%d:%d dangling operator", p.lex.ln, p.lex.posInLine)
}
return true, nil
}
return false, nil
}
func (p *Parser) checkEndOrError(t tokenType, parent Node) (bool, error) {
if ok, err := p.checkForEOF(t, parent); ok {
return ok, err
}
if err := p.checkImpossibleTokensOnEnter(t); err != nil {
return true, err
}
return false, nil
}
func (p *Parser) mergeSubExpression(sub, parent Node) (Node, error) {
t, err := p.lex.ConsumeToken()
if err != nil {
return parent, err
}
conj := &binaryExpression{nodes: [2]Node{nil, nil}}
conj.operator = t.String()
conj.Add(sub)
rhs, err := p.build(conj)
if err != nil {
return conj, err
}
conj.Add(rhs)
parent.Add(conj)
return parent, nil
}
func (p *Parser) build(parent Node) (Node, error) {
t, err := p.lex.ConsumeToken()
if err != nil {
return parent, err
}
if ok, err := p.checkEndOrError(t, parent); ok {
return parent, err
}
if t == tokenBraceOpen {
sub, err := p.handleSubExpression(parent)
if err != nil {
return parent, err
}
t, err := p.lex.ConsumeToken()
if err != nil {
return parent, err
}
if t != tokenBraceClose {
return parent, fmt.Errorf("ln:%d:%d syntax error (unclosed brace `)` )", p.lex.ln, p.lex.posInLine)
}
next, _, err := p.lex.PeekNextToken()
if err != nil {
return parent, err
}
if isLogicToken(next) {
return p.mergeSubExpression(sub, parent)
}
if parent.NodeType() == NodeTypeExpression {
parent.Add(sub)
return parent, nil
}
return sub, nil
}
if t == tokenValue {
next, _, err := p.lex.PeekNextToken()
if err != nil {
return parent, err
}
var nextExpr Node
if isSeperatorUnary(next) {
nextExpr, err = p.handleUnaryExpression(parent)
} else {
nextExpr, err = p.handleBinaryExpression(t, parent)
}
if parent.isRoot() {
parent.Add(nextExpr)
return parent, err
}
return nextExpr, err
}
return parent, err
}
// Parse parses the supplied fiql and returns either a Expression or an error
func (p *Parser) Parse(input string) (Expression, error) {
p.lex = &lexer{[]rune(input), 0, 1, 0, ""}
exp := Expression{root: true}
_, err := p.build(&exp)
return exp, err
}
// NewParser returns a new fiql parser
func NewParser() *Parser {
return &Parser{}
}
// Parse instant parses the supplied fiql and returns either a Expression or an error
func Parse(input string) (Expression, error) {
p := &Parser{}
return p.Parse(input)
}