super-graph/qcode/parse.go

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package qcode
import (
"errors"
"fmt"
"github.com/dosco/super-graph/util"
)
var (
errEOT = errors.New("end of tokens")
)
type parserType int16
const (
parserError parserType = iota
parserEOF
opQuery
opMutate
opSub
nodeStr
nodeInt
nodeFloat
nodeBool
nodeObj
nodeList
nodeVar
)
func (t parserType) String() string {
var v string
switch t {
case parserEOF:
v = "EOF"
case parserError:
v = "error"
case opQuery:
v = "query"
case opMutate:
v = "mutation"
case opSub:
v = "subscription"
case nodeStr:
v = "node-string"
case nodeInt:
v = "node-int"
case nodeFloat:
v = "node-float"
case nodeBool:
v = "node-bool"
case nodeObj:
v = "node-obj"
case nodeList:
v = "node-list"
}
return fmt.Sprintf("<%s>", v)
}
type Operation struct {
Type parserType
Name string
Args []*Arg
Fields []*Field
}
type Field struct {
Name string
Alias string
Args []*Arg
Parent *Field
Children []*Field
}
type Arg struct {
Name string
Val *Node
}
type Node struct {
Type parserType
Name string
Val string
Parent *Node
Children []*Node
}
type Parser struct {
pos int
items []item
depth int
err error
}
func Parse(gql string) (*Operation, error) {
if len(gql) == 0 {
return nil, errors.New("blank query")
}
l, err := lex(gql)
if err != nil {
return nil, err
}
p := &Parser{
pos: -1,
items: l.items,
}
return p.parseOp()
}
func ParseQuery(gql string) (*Operation, error) {
return parseByType(gql, opQuery)
}
func ParseArgValue(argVal string) (*Node, error) {
l, err := lex(argVal)
if err != nil {
return nil, err
}
p := &Parser{
pos: -1,
items: l.items,
}
return p.parseValue()
}
func parseByType(gql string, ty parserType) (*Operation, error) {
l, err := lex(gql)
if err != nil {
return nil, err
}
p := &Parser{
pos: -1,
items: l.items,
}
return p.parseOpByType(ty)
}
func (p *Parser) next() item {
n := p.pos + 1
if n >= len(p.items) {
p.err = errEOT
return item{typ: itemEOF}
}
p.pos = n
return p.items[p.pos]
}
func (p *Parser) ignore() {
n := p.pos + 1
if n >= len(p.items) {
p.err = errEOT
return
}
p.pos = n
}
func (p *Parser) current() item {
return p.items[p.pos]
}
func (p *Parser) eof() bool {
n := p.pos + 1
return p.items[n].typ == itemEOF
}
func (p *Parser) peek(types ...itemType) bool {
n := p.pos + 1
if p.items[n].typ == itemEOF {
return false
}
if n >= len(p.items) {
return false
}
for i := 0; i < len(types); i++ {
if p.items[n].typ == types[i] {
return true
}
}
return false
}
func (p *Parser) parseOpByType(ty parserType) (*Operation, error) {
op := &Operation{Type: ty}
var err error
if p.peek(itemName) {
op.Name = p.next().val
}
if p.peek(itemArgsOpen) {
p.ignore()
op.Args, err = p.parseArgs()
if err != nil {
return nil, err
}
}
if p.peek(itemObjOpen) {
p.ignore()
op.Fields, err = p.parseFields()
if err != nil {
return nil, err
}
}
if p.peek(itemObjClose) {
p.ignore()
}
return op, nil
}
func (p *Parser) parseOp() (*Operation, error) {
if p.peek(itemQuery, itemMutation, itemSub) == false {
err := fmt.Errorf("expecting a query, mutation or subscription (not '%s')", p.next().val)
return nil, err
}
item := p.next()
switch item.typ {
case itemQuery:
return p.parseOpByType(opQuery)
case itemMutation:
return p.parseOpByType(opMutate)
case itemSub:
return p.parseOpByType(opSub)
}
return nil, errors.New("unknown operation type")
}
func (p *Parser) parseFields() ([]*Field, error) {
var roots []*Field
st := util.NewStack()
for {
if p.peek(itemObjClose) {
p.ignore()
st.Pop()
if st.Len() == 0 {
break
}
continue
}
if p.peek(itemName) == false {
return nil, errors.New("expecting an alias or field name")
}
field, err := p.parseField()
if err != nil {
return nil, err
}
if st.Len() == 0 {
roots = append(roots, field)
} else {
intf := st.Peek()
parent, ok := intf.(*Field)
if !ok || parent == nil {
return nil, fmt.Errorf("unexpected value encountered %v", intf)
}
field.Parent = parent
parent.Children = append(parent.Children, field)
}
if p.peek(itemObjOpen) {
p.ignore()
st.Push(field)
}
}
return roots, nil
}
func (p *Parser) parseField() (*Field, error) {
var err error
field := &Field{Name: p.next().val}
if p.peek(itemColon) {
p.ignore()
if p.peek(itemName) {
field.Alias = field.Name
field.Name = p.next().val
} else {
return nil, errors.New("expecting an aliased field name")
}
}
if p.peek(itemArgsOpen) {
p.ignore()
if field.Args, err = p.parseArgs(); err != nil {
return nil, err
}
}
return field, nil
}
func (p *Parser) parseArgs() ([]*Arg, error) {
var args []*Arg
var err error
for {
if p.peek(itemArgsClose) {
p.ignore()
break
}
if p.peek(itemName) == false {
return nil, errors.New("expecting an argument name")
}
arg := &Arg{Name: p.next().val}
if p.peek(itemColon) == false {
return nil, errors.New("missing ':' after argument name")
}
p.ignore()
arg.Val, err = p.parseValue()
if err != nil {
return nil, err
}
args = append(args, arg)
}
return args, nil
}
func (p *Parser) parseList() (*Node, error) {
parent := &Node{}
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var nodes []*Node
var ty parserType
for {
if p.peek(itemListClose) {
p.ignore()
break
}
node, err := p.parseValue()
if err != nil {
return nil, err
}
if ty == 0 {
ty = node.Type
} else {
if ty != node.Type {
return nil, errors.New("All values in a list must be of the same type")
}
}
node.Parent = parent
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nodes = append(nodes, node)
}
if len(nodes) == 0 {
return nil, errors.New("List cannot be empty")
}
parent.Type = nodeList
parent.Children = nodes
return parent, nil
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}
func (p *Parser) parseObj() (*Node, error) {
parent := &Node{}
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var nodes []*Node
for {
if p.peek(itemObjClose) {
p.ignore()
break
}
if p.peek(itemName) == false {
return nil, errors.New("expecting an argument name")
}
nodeName := p.next().val
if p.peek(itemColon) == false {
return nil, errors.New("missing ':' after Field argument name")
}
p.ignore()
node, err := p.parseValue()
if err != nil {
return nil, err
}
node.Name = nodeName
node.Parent = parent
nodes = append(nodes, node)
}
parent.Type = nodeObj
parent.Children = nodes
return parent, nil
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}
func (p *Parser) parseValue() (*Node, error) {
if p.peek(itemListOpen) {
p.ignore()
return p.parseList()
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}
if p.peek(itemObjOpen) {
p.ignore()
return p.parseObj()
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}
item := p.next()
node := &Node{}
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switch item.typ {
case itemIntVal:
node.Type = nodeInt
case itemFloatVal:
node.Type = nodeFloat
case itemStringVal:
node.Type = nodeStr
case itemBoolVal:
node.Type = nodeBool
case itemName:
node.Type = nodeStr
case itemVariable:
node.Type = nodeVar
default:
return nil, fmt.Errorf("expecting a number, string, object, list or variable as an argument value (not %s)", p.next().val)
}
node.Val = item.val
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return node, nil
}