package ph7

/*
#include "cgo.h"
#include "ph7.h"
*/
import "C"
import (
	"fmt"
	"io"
	"unsafe"

	pointer "github.com/mattn/go-pointer"
)

type ResultCode int

const (
	ResultCodeOK         = ResultCode(C.PH7_OK)
	ResultCodeNoMem      = ResultCode(C.PH7_NOMEM)
	ResultCodeAbort      = ResultCode(C.PH7_ABORT)
	ResultCodeIOErr      = ResultCode(C.PH7_IO_ERR)
	ResultCodeLooked     = ResultCode(C.PH7_LOOKED)
	ResultCodeCorrupt    = ResultCode(C.PH7_CORRUPT)
	ResultCodeCompileErr = ResultCode(C.PH7_COMPILE_ERR)
	ResultCodeVMErr      = ResultCode(C.PH7_VM_ERR)
)

func (r ResultCode) String() string {
	switch r {
	case ResultCodeOK:
		return "PH7_OK"
	case ResultCodeNoMem:
		return "PH7_NOMEM"
	case ResultCodeAbort:
		return "PH7_ABORT"
	case ResultCodeIOErr:
		return "PH7_IO_ERR"
	case ResultCodeLooked:
		return "PH7_LOOKED"
	case ResultCodeCorrupt:
		return "PH7_CORRUPT"
	case ResultCodeCompileErr:
		return "PH7_COMPILE_ERR"
	case ResultCodeVMErr:
		return "PH7_VM_ERR"
	default:
		return "UNKNOWN"
	}
}

type Error struct {
	Code ResultCode
}

// TODO create a CompileError that contains the error log text

func newError(code C.int) error {
	if code != C.PH7_OK {
		return Error{
			Code: ResultCode(code),
		}
	}
	return nil
}

func (e Error) Error() string {
	return fmt.Sprintf("ph7: %s", e.Code)
}

type Engine C.ph7

// TODO strip off the enclosing struct if possible after wrapping all engine methods.

func NewEngine() (*Engine, error) {
	var cengine *C.ph7
	result := C.ph7_init(&cengine)
	if result != C.PH7_OK {
		return nil, newError(result)
	}

	return (*Engine)(cengine), nil
}

func (e *Engine) ErrLog() (string, error) {
	var s *C.char
	var n C.int

	err := newError(C.engine_config_err_log((*C.ph7)(e), &s, &n))
	if err != nil {
		return "", err
	}

	return C.GoStringN(s, n), nil
}

func (e *Engine) Compile(source []byte, phpOnly bool) (*VM, error) {
	csource := C.CBytes(source)
	defer C.free(csource)
	var flags C.int
	if phpOnly {
		flags |= C.PH7_PHP_ONLY
	}
	var cvm *C.ph7_vm
	err := newError(C.ph7_compile_v2((*C.ph7)(e), (*C.char)(csource), C.int(len(source)), &cvm, flags))
	if err != nil {
		return nil, err
	}

	return newVM(cvm), nil
}

func (e *Engine) Close() error {
	return newError(C.ph7_release((*C.ph7)(e)))
}

type Value C.ph7_value

type Context C.ph7_context

type VM struct {
	ptr          *C.ph7_vm
	pointerKey   unsafe.Pointer
	outputWriter io.Writer
	// TODO clear outputWriteError when resetting VM
	outputWriteErr   error
	userFunctionKeys []unsafe.Pointer
}

func newVM(cvm *C.ph7_vm) *VM {
	vm := new(VM)
	vm.ptr = cvm
	vm.pointerKey = pointer.Save(vm)
	return vm
}

//export write_vm_output
func write_vm_output(buf unsafe.Pointer, bufLen C.uint, userData unsafe.Pointer) C.int {
	vm := pointer.Restore(userData).(*VM)
	gobuf := C.GoBytes(buf, C.int(bufLen))
	_, vm.outputWriteErr = vm.outputWriter.Write(gobuf)
	if vm.outputWriteErr != nil {
		return C.int(ResultCodeAbort)
	}
	return C.int(ResultCodeOK)
}

func (vm *VM) SetOutputWriter(w io.Writer) error {
	vm.outputWriter = w
	return newError(C.vm_set_output_callback(vm.ptr, vm.pointerKey))
}

func (vm *VM) OutputWriteError() error {
	return vm.outputWriteErr
}

func (vm *VM) ExtractOutput() (string, error) {
	var s *C.char
	var n C.int

	err := newError(C.vm_extract_output(vm.ptr, &s, &n))
	if err != nil {
		return "", err
	}

	return C.GoStringN(s, n), nil
}

func (vm *VM) Exec() error {
	// TODO return exit status
	return newError(C.ph7_vm_exec(vm.ptr, (*C.int)(nil)))
}

func (vm *VM) Reset() error {
	return newError(C.ph7_vm_reset(vm.ptr))
}

func (vm *VM) Close() error {
	pointer.Unref(vm.pointerKey)
	for _, key := range vm.userFunctionKeys {
		pointer.Unref(key)
	}
	return newError(C.ph7_vm_release(vm.ptr))
}

type ForeignFunction interface {
	Call(ctx *Context, args []*Value) ResultCode
}

//export call_foreign_function
func call_foreign_function(ctx *C.ph7_context, argc C.int, argv **C.ph7_value) C.int {
	fkey := C.ph7_context_user_data(ctx)
	f := pointer.Restore(fkey).(ForeignFunction)
	args := make([]*Value, 0, argc)
	argvSlice := unsafe.Slice(argv, argc)
	for i := range argvSlice {
		args = append(args, (*Value)(argvSlice[i]))
	}
	return C.int(f.Call((*Context)(ctx), args))
}

func (vm *VM) CreateFunction(name string, f ForeignFunction) error {
	cname := C.CString(name)
	defer C.free(unsafe.Pointer(cname))

	fkey := pointer.Save(f)
	vm.userFunctionKeys = append(vm.userFunctionKeys, fkey)

	return newError(C.vm_create_function(vm.ptr, cname, fkey))
}