/
ast.go
154 lines (134 loc) · 2.24 KB
/
ast.go
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package pql
import (
"fmt"
"io"
"strings"
)
type Context struct {
Columns []string
Vars map[string]interface{}
}
type Node interface {
Exec(io.Writer, Context) error
Span() Span
}
type node struct {
span Span
}
func newNode(t string, o, l int) node {
return node{span: NewSpan(t, o, l)}
}
func (n node) Exec(w io.Writer, cxt Context) error {
return nil // noop
}
func (n node) Span() Span {
return n.span
}
type Program struct {
node
sub []Node
}
func (p Program) Text(cxt Context) (string, error) {
w := &strings.Builder{}
err := p.Exec(w, cxt)
if err != nil {
return "", err
}
return w.String(), nil
}
func (p Program) Exec(w io.Writer, cxt Context) error {
if len(p.sub) < 1 {
return nil
}
for _, e := range p.sub {
err := e.Exec(w, cxt)
if err != nil {
return err
}
}
return nil
}
type literalNode struct {
node
text string
}
func (n literalNode) Exec(w io.Writer, cxt Context) error {
_, err := w.Write([]byte(n.text))
return err
}
type exprListNode struct {
node
sub []Node
}
func (n exprListNode) Exec(w io.Writer, cxt Context) error {
if len(n.sub) < 1 {
return nil
}
for i, e := range n.sub {
if i > 0 {
_, err := w.Write([]byte(", "))
if err != nil {
return err
}
}
err := e.Exec(w, cxt)
if err != nil {
return err
}
}
return nil
}
type exprLiteralNode struct {
node
prefix string
name string
}
func (n exprLiteralNode) Exec(w io.Writer, cxt Context) error {
var t string
if n.prefix != "" {
t = fmt.Sprintf("%s.%s", n.prefix, n.name)
} else {
t = n.name
}
_, err := w.Write([]byte(t))
if err != nil {
return err
}
return nil
}
type exprMatchNode struct {
node
prefix string
}
func (n exprMatchNode) Exec(w io.Writer, cxt Context) error {
for i, e := range cxt.Columns {
if i > 0 {
_, err := w.Write([]byte(", "))
if err != nil {
return err
}
}
var t string
if n.prefix != "" {
t = fmt.Sprintf("%s.%s", n.prefix, e)
} else {
t = e
}
_, err := w.Write([]byte(t))
if err != nil {
return err
}
}
return nil
}
type variableNode struct {
node
name string
}
func (n variableNode) Exec(w io.Writer, cxt Context) error {
_, err := w.Write([]byte(stringer(cxt.Vars[n.name])))
if err != nil {
return err
}
return nil
}