#include <Python.h>
#include <stringobject.h>
#include <dictobject.h>

PyObject *xlate(PyObject *s, PyObject *o) {
    unsigned char *inbuf;
    int i, length, pos=0;
    PyObject *map, *key, *value, *ret;
    Py_UNICODE *u, *ru;

    if(!PyArg_ParseTuple(o, "s#O", (char*)&inbuf, &length, &map)) return NULL;
    if(!PyDict_Check(map)) {
        PyErr_SetString(PyExc_TypeError, "Argument 2 must be a dictionary");
        return NULL;
    }

    u = PyMem_Malloc(sizeof(Py_UNICODE) * 256);
    if(!u) { return NULL; }
    for(i=0; i<256; i++) {
        u[i] = 0xfffd;
    }

    while(PyDict_Next(map, &pos, &key, &value)) {
        int ki, vi;
        if(!PyInt_Check(key)) { 
            PyErr_SetString(PyExc_TypeError, "Dictionary keys must be ints");
            return NULL;
        }
        ki = PyInt_AsLong(key);
        if(ki < 0 || ki > 255) { 
            PyErr_Format(PyExc_TypeError,
                "Dictionary keys must be in the range 0..255 (saw %d)", ki);
            return NULL;
        }
        if(value == Py_None) continue;
        if(!PyInt_Check(value)) { 
            PyErr_SetString(PyExc_TypeError, "Dictionary values must be ints or None");
            return NULL;
        }
        vi = PyInt_AsLong(value);
        u[ki] = vi;
    }

    ret = PyUnicode_FromUnicode(NULL, length);
    if(!ret) { free(u); return NULL; }
    ru = PyUnicode_AsUnicode(ret);
    for(i=0; i<length; i++) {
        ru[i] = u[inbuf[i]];
    }
    free(u);
    return ret;
}

PyMethodDef md[] = {
    {"xlate", (PyCFunction)xlate, METH_VARARGS, NULL},
    {NULL, NULL, 0, NULL}
};

void initxlate(void) {
    Py_InitModule("xlate", md);
}