jq.go

package jq

// #cgo LDFLAGS: -ljq
// #include <jq.h>
// #include <jv.h>
import "C"
import (
	"errors"
	"fmt"
	"reflect"
)

type JQ struct {
	program    string
	state      *C.jq_state
	lastValue  C.jv
	prevRefCnt int
}

func NewJQ(program string) (*JQ, error) {
	state := C.jq_init()
	jq := &JQ{program, state, C.jv_invalid(), 0}
	if err := jq.compile(program); err != nil {
		jq.Close()
		return nil, err
	}
	return jq, nil
}

func (jq *JQ) Handle(value interface{}) {
	jq.start(goToJv(value))
}

func (jq *JQ) HandleJson(text string) error {
	jv, err := parseJson(text)

	if err == nil {
		jq.start(jv)
		return nil
	} else {
		return err
	}
}

func (jq *JQ) Next() bool {
	// jq.ValueJson() is self execute internally (jv_dump_term in the jv_dump_string)
	if jq.prevRefCnt == jq.jv_get_refcnt() {
		freeJv(jq.lastValue)
	}
	jq.lastValue = jq.next()
	jq.prevRefCnt = jq.jv_get_refcnt()
	return isValid(jq.lastValue)
}

func (jq *JQ) Value() interface{} {
	return jvToGo(jq.lastValue)
}

func (jq *JQ) ValueJson() string {
	return dumpJson(jq.lastValue)
}

func (jq *JQ) Close() {
	jq.teardown()
	freeJv(jq.lastValue)
}

// JQ APIs

func (jq *JQ) compile(program string) error {
	if rc := C.jq_compile(jq.state, C.CString(program)); rc == 0 {
		return errors.New("Unable to compile jq filter")
	} else {
		return nil
	}
}

func (jq *JQ) start(jv C.jv) {
	C.jq_start(jq.state, jv, 0)
}

func (jq *JQ) next() C.jv {
	return C.jq_next(jq.state)
}

func (jq *JQ) teardown() {
	C.jq_teardown(&jq.state)
}

func (jq *JQ) jv_get_refcnt() int {
	return (int)(C.jv_get_refcnt(jq.lastValue))
}

// JSON values

func parseJson(value string) (C.jv, error) {
	v := C.jv_parse(C.CString(value))
	if C.jv_is_valid(v) == 0 {
		return C.jv_null(), errors.New("Invalid JSON")
	}
	return v, nil
}

func dumpJson(jv C.jv) string {
	jv = C.jv_copy(jv)
	strJv := C.jv_dump_string(jv, 0)
	result := C.jv_string_value(strJv)
	freeJv(strJv)
	return C.GoString(result)
}

func refcount(jv C.jv) int {
	return int(C.jv_get_refcnt(jv))
}

func goToJv(v interface{}) C.jv {
	if v == nil {
		return C.jv_null()
	}

	value := reflect.Indirect(reflect.ValueOf(v))

	switch value.Type().Kind() {
	case reflect.Bool:
		if value.Bool() {
			return C.jv_true()
		} else {
			return C.jv_false()
		}
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return C.jv_number(C.double(value.Int()))
	// TODO reflect.Uintptr?
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return C.jv_number(C.double(value.Uint()))
	case reflect.Float32, reflect.Float64:
		return C.jv_number(C.double(value.Float()))
	case reflect.String:
		return C.jv_string(C.CString(value.String()))
	case reflect.Array, reflect.Slice:
		n := value.Len()
		arr := C.jv_array_sized(C.int(n))
		for i := 0; i < n; i++ {
			item := goToJv(value.Index(i).Interface())
			arr = C.jv_array_set(C.jv_copy(arr), C.int(i), item)
		}
		return arr
	case reflect.Map:
		// TODO assert key is string?
		object := C.jv_object()
		for _, k := range value.MapKeys() {
			key := goToJv(k.Interface())
			mapValue := goToJv(value.MapIndex(k).Interface())
			object = C.jv_object_set(object, key, mapValue)
		}
		return object
	}

	msg := fmt.Sprintf("unknown type for: %v", value.Interface())

	return C.jv_invalid_with_msg(C.jv_string(C.CString(msg)))
}

func jvToGo(value C.jv) interface{} {
	switch C.jv_get_kind(value) {
	case C.JV_KIND_INVALID:
		return errors.New("invalid")
	case C.JV_KIND_NULL:
		return nil
	case C.JV_KIND_FALSE:
		return false
	case C.JV_KIND_TRUE:
		return true
	case C.JV_KIND_NUMBER:
		number := C.jv_number_value(value)
		if C.jv_is_integer(value) == 0 {
			return float64(number)
		} else {
			return int(number)
		}
	case C.JV_KIND_STRING:
		return C.GoString(C.jv_string_value(value))
	case C.JV_KIND_ARRAY:
		length := C.jv_array_length(C.jv_copy(value))
		arr := make([]interface{}, length)
		for i := range arr {
			arr[i] = jvToGo(C.jv_array_get(C.jv_copy(value), C.int(i)))
		}
		return arr
	case C.JV_KIND_OBJECT:
		result := make(map[string]interface{})
		var k, v C.jv
		for jv_i := C.jv_object_iter(value); C.jv_object_iter_valid(value, jv_i) != 0; jv_i = C.jv_object_iter_next(value, jv_i) {
			k = C.jv_object_iter_key(value, jv_i)
			v = C.jv_object_iter_value(value, jv_i)
			result[C.GoString(C.jv_string_value(k))] = jvToGo(v)
		}
		return result
	default:
		return errors.New("unknown type")
	}
}

func freeJv(jv C.jv) {
	C.jv_free(jv)
}

func isValid(jv C.jv) bool {
	return C.jv_is_valid(jv) != 0
}