#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "maplec.h"
#include "duktape.h"

/* --- EXPORT_DECL macro from official example --- */

#if !defined(EXPORT_DECL)
#ifdef _MSC_VER
#define EXPORT_DECL __declspec(dllexport)
#else
#define EXPORT_DECL
#endif
#endif

/* --- the SheetJS + Duktape demo cover these machinations --- */

#define FAIL_LOAD { \
  duk_push_undefined(ctx); \
  perror("Error in load_file"); \
  return 1; \
}

static char *read_file(const char *filename, size_t *sz) {
  FILE *f = fopen(filename, "rb");
  if(!f) return NULL;
  long fsize; { fseek(f, 0, SEEK_END); fsize = ftell(f); fseek(f, 0, SEEK_SET); }
  char *buf = (char *)malloc(fsize * sizeof(char));
  *sz = fread((void *) buf, 1, fsize, f);
  fclose(f);
  return buf;
}

static duk_int_t eval_file(duk_context *ctx, const char *filename) {
  size_t len; char *buf = read_file(filename, &len);
  if(!buf) FAIL_LOAD

  duk_push_lstring(ctx, (const char *)buf, (duk_size_t)len);
  duk_int_t retval = duk_peval(ctx);
  duk_pop(ctx);
  return retval;
}

static duk_int_t load_file(duk_context *ctx, const char *filename, const char *var) {
  size_t len; char *buf = read_file(filename, &len);
  if(!buf) FAIL_LOAD

  duk_push_external_buffer(ctx);
  duk_config_buffer(ctx, -1, buf, len);
  duk_put_global_string(ctx, var);
  return 0;
}

static duk_int_t save_file(duk_context *ctx, const char *filename, const char *var) {
  duk_get_global_string(ctx, var);
  duk_size_t sz;
  char *buf = (char *)duk_get_buffer_data(ctx, -1, &sz);

  if(!buf) return 1;
  FILE *f = fopen(filename, "wb"); fwrite(buf, 1, sz, f); fclose(f);
  return 0;
}

#define FAIL_DUK(cmd) { \
  const char *errmsg = duk_safe_to_string(ctx, -1); \
  duk_destroy_heap(ctx); \
  MapleRaiseError2(kv, "error in %1 : %2", ToMapleString(kv, cmd), ToMapleString(kv, errmsg)); \
  return NULL; \
}

#define DOIT(cmd) duk_eval_string_noresult(ctx, cmd);

/* SheetToXLSX function */
EXPORT_DECL ALGEB M_DECL SheetToXLSX( MKernelVector kv, ALGEB *args ) {
  duk_int_t res = 0;

  /* get filename */
  if(MapleNumArgs(kv, (ALGEB)args) != 1) {
    MapleRaiseError(kv, "must specify a filename");
    return NULL;
  }
  if(!IsMapleString(kv, args[1])) {
    MapleRaiseError(kv, "filename must be a string");
    return NULL;
  }
  const char *filename = MapleToString(kv, args[1]);

  /* initialize duktape */
  duk_context *ctx = duk_create_heap_default();
  /* duktape does not expose a standard "global" by default */
  DOIT("var global = (function(){ return this; }).call(null);");

  /* load SheetJS library */
  res = eval_file(ctx, "shim.min.js");
  if(res != 0) FAIL_DUK("shim load")
  res = eval_file(ctx, "xlsx.full.min.js");
  if(res != 0) FAIL_DUK("library load")

  /* read file */
  res = load_file(ctx, filename, "buf");
  if(res != 0) FAIL_DUK("file load")
  printf("Loaded file %s\n", filename);

  /* parse workbook and write to XLSX */
  DOIT("wb = XLSX.read(buf.slice(0, buf.length), {type:'buffer'});");
  DOIT("newbuf = (XLSX.write(wb, {type:'array', bookType:'xlsx'}));");\

  /* write file */
  res = save_file(ctx, "sheetjsw.xlsx", "newbuf");\
  if(res != 0) FAIL_DUK("save sheetjsw.xlsx")

  /* return filename */
  return ToMapleString(kv, "sheetjsw.xlsx");
}