package R

/*

#cgo LDFLAGS: -lm -lR


#define CSTACK_DEFNS 1

#include <stdlib.h>
#include <Rinterface.h>
#include <R.h>
#include <Rinternals.h>
#include <Rdefines.h>
#include <R_ext/Parse.h>
#include <Rembedded.h>

int initR() {
    char *argv[] = {"REmbeddedMy", "--gui=none", "--silent", "--slave"};
    int argc = sizeof(argv)/sizeof(argv[0]);
    int result = Rf_initEmbeddedR(argc, argv);
    R_CStackLimit = (uintptr_t)-1;
    R_Interactive = (Rboolean)0;

    return result;
}

*/
import "C"
import (
	"fmt"
	"unsafe"
)

var (
	isInitialized int
)

type RProtector interface {
	Protect(sexpr C.SEXP) RProtector
	Unprotect()
}

type protector struct {
	count int
}

func Protect(sexpr C.SEXP) RProtector {
	p := protector{}
	p.Protect(sexpr)
	return &p
}

func (this *protector) Protect(sexpr C.SEXP) RProtector {
	C.Rf_protect(sexpr)
	this.count++
	return this
}

func (this *protector) Unprotect() {
	C.Rf_unprotect(C.int(this.count))
	this.count = 0
}

func EvalOrDie(expression string) *Result {
	r, err := Eval(expression)
	if err != nil {
		panic(fmt.Sprintf("FAILED: %s", err))
	}
	return r
}

func Eval(expression string) (*Result, error) {

	var status C.ParseStatus

	cmd := C.CString(expression)
	defer C.free(unsafe.Pointer(cmd))

	cmdRChar := C.mkChar(cmd)
	protector := Protect(cmdRChar)
	defer protector.Unprotect()

	cmdSexp := C.allocVector(C.STRSXP, 1)
	protector.Protect(cmdSexp)

	C.SET_STRING_ELT(cmdSexp, 0, cmdRChar)

	parsedCmd := C.R_ParseVector(cmdSexp, -1, (*C.ParseStatus)(unsafe.Pointer(&status)), C.R_NilValue)
	if status != C.PARSE_OK {
		return nil, fmt.Errorf("Invalid command: %s", C.GoString(cmd))
	}

	protector.Protect(parsedCmd)

	var result C.SEXP
	errorOccured := 0
	/* Loop is needed here as EXPSEXP will be of length > 1 */
	for i := 0; i < int(C.Rf_length(parsedCmd)); i++ {
		result = C.R_tryEval(C.VECTOR_ELT(parsedCmd, C.R_xlen_t(i)), C.R_GlobalEnv, (*C.int)(unsafe.Pointer(&errorOccured))) //R 3.0
		if errorOccured != 0 {
			return nil, fmt.Errorf("R error occured executing: %s", C.GoString(cmd))
		}
	}
	return NewResult(result), nil
}

func SetSymbol(name string, val Expression) {
	nameC := C.CString(name)
	defer C.free(unsafe.Pointer(nameC))
	C.Rf_protect(val.ToSexp())
	defer C.Rf_unprotect(1)
	C.defineVar(C.install(nameC), val.ToSexp(), C.R_GlobalEnv)
}

func VariableExists(name string) bool {
	nameC := C.CString(name)
	defer C.free(unsafe.Pointer(nameC))
	return C.findVar(C.install(nameC), C.R_GlobalEnv) == C.R_UnboundValue
}

func Init() int {
	if isInitialized != 0 {
		return isInitialized
	}
	isInitialized = int(C.initR())
	return isInitialized
}