#include "quickjs.h"

#define WOTA_IMPLEMENTATION
#include "wota.h"

typedef struct WotaEncodeContext {
  JSContext *ctx;
  JSValue visited_stack;
  WotaBuffer wb;
  int cycle;
  JSValue replacer;
} WotaEncodeContext;

static void wota_stack_push(WotaEncodeContext *enc, JSValueConst val)
{
  JSContext *ctx = enc->ctx;
  int len = JS_ArrayLength(ctx, enc->visited_stack);
  JS_SetPropertyInt64(ctx, enc->visited_stack, len, JS_DupValue(ctx, val));
}

static void wota_stack_pop(WotaEncodeContext *enc)
{
  JSContext *ctx = enc->ctx;
  int len = JS_ArrayLength(ctx, enc->visited_stack);
  JS_SetPropertyStr(ctx, enc->visited_stack, "length", JS_NewUint32(ctx, len - 1));
}

static int wota_stack_has(WotaEncodeContext *enc, JSValueConst val)
{
  JSContext *ctx = enc->ctx;
  int len = JS_ArrayLength(ctx, enc->visited_stack);
  for (int i = 0; i < len; i++) {
    JSValue elem = JS_GetPropertyUint32(ctx, enc->visited_stack, i);
    if (JS_IsObject(elem) && JS_IsObject(val))
      if (JS_VALUE_GET_OBJ(elem) == JS_VALUE_GET_OBJ(val)) {
        JS_FreeValue(ctx, elem);
        return 1;
      }
    JS_FreeValue(ctx, elem);
  }
  return 0;
}

static JSValue apply_replacer(WotaEncodeContext *enc, JSValueConst holder, JSValueConst key, JSValueConst val)
{
  if (JS_IsUndefined(enc->replacer)) return JS_DupValue(enc->ctx, val);
  JSValue args[2] = { JS_DupValue(enc->ctx, key), JS_DupValue(enc->ctx, val) };
  JSValue result = JS_Call(enc->ctx, enc->replacer, holder, 2, args);
  JS_FreeValue(enc->ctx, args[0]);
  JS_FreeValue(enc->ctx, args[1]);
  if (JS_IsException(result)) return JS_DupValue(enc->ctx, val);
  return result;
}

static void wota_encode_value(WotaEncodeContext *enc, JSValueConst val, JSValueConst holder, JSValueConst key);

static void encode_object_properties(WotaEncodeContext *enc, JSValueConst val, JSValueConst holder)
{
  JSContext *ctx = enc->ctx;
  JSPropertyEnum *ptab;
  uint32_t plen;
  if (JS_GetOwnPropertyNames(ctx, &ptab, &plen, val, JS_GPN_ENUM_ONLY | JS_GPN_STRING_MASK) < 0) {
    wota_write_sym(&enc->wb, WOTA_NULL);
    return;
  }
  uint32_t non_function_count = 0;
  for (uint32_t i = 0; i < plen; i++) {
    JSValue prop_val = JS_GetProperty(ctx, val, ptab[i].atom);
    if (!JS_IsFunction(ctx, prop_val)) non_function_count++;
    JS_FreeValue(ctx, prop_val);
  }
  wota_write_record(&enc->wb, non_function_count);
  for (uint32_t i = 0; i < plen; i++) {
    JSValue prop_val = JS_GetProperty(ctx, val, ptab[i].atom);
    if (!JS_IsFunction(ctx, prop_val)) {
      const char *prop_name = JS_AtomToCString(ctx, ptab[i].atom);
      JSValue prop_key = JS_AtomToValue(ctx, ptab[i].atom);
      wota_write_text(&enc->wb, prop_name);
      wota_encode_value(enc, prop_val, val, prop_key);
      JS_FreeCString(ctx, prop_name);
      JS_FreeValue(ctx, prop_key);
    }
    JS_FreeValue(ctx, prop_val);
    JS_FreeAtom(ctx, ptab[i].atom);
  }
  js_free(ctx, ptab);
}

static void wota_encode_value(WotaEncodeContext *enc, JSValueConst val, JSValueConst holder, JSValueConst key)
{
  JSContext *ctx = enc->ctx;
  JSValue replaced = apply_replacer(enc, holder, key, val);
  int tag = JS_VALUE_GET_TAG(replaced);
  switch (tag) {
    case JS_TAG_INT: {
      double d;
      JS_ToFloat64(ctx, &d, replaced);
      wota_write_number(&enc->wb, d);
      break;
    }
    case JS_TAG_FLOAT64:
    case JS_TAG_BIG_INT:
    case JS_TAG_BIG_DECIMAL:
    case JS_TAG_BIG_FLOAT: {
      double d;
      if (JS_ToFloat64(ctx, &d, replaced) < 0) {
        wota_write_sym(&enc->wb, WOTA_NULL);
        break;
      }
      wota_write_number(&enc->wb, d);
      break;
    }
    case JS_TAG_STRING: {
      const char *str = JS_ToCString(ctx, replaced);
      wota_write_text(&enc->wb, str ? str : "");
      JS_FreeCString(ctx, str);
      break;
    }
    case JS_TAG_BOOL:
      wota_write_sym(&enc->wb, JS_VALUE_GET_BOOL(replaced) ? WOTA_TRUE : WOTA_FALSE);
      break;
    case JS_TAG_NULL:
    case JS_TAG_UNDEFINED:
      wota_write_sym(&enc->wb, WOTA_NULL);
      break;
    case JS_TAG_OBJECT: {
      if (JS_IsArrayBuffer(ctx, replaced)) {
        size_t buf_len;
        void *buf_data = JS_GetArrayBuffer(ctx, &buf_len, replaced);
        wota_write_blob(&enc->wb, (unsigned long long)buf_len * 8, (const char *)buf_data);
        break;
      }
      if (JS_IsArray(ctx, replaced)) {
        if (wota_stack_has(enc, replaced)) {
          enc->cycle = 1;
          break;
        }
        wota_stack_push(enc, replaced);
        int arr_len = JS_ArrayLength(ctx, replaced);
        wota_write_array(&enc->wb, arr_len);
        for (int i = 0; i < arr_len; i++) {
          JSValue elem_val = JS_GetPropertyUint32(ctx, replaced, i);
          JSValue elem_key = JS_NewInt32(ctx, i);
          wota_encode_value(enc, elem_val, replaced, elem_key);
          JS_FreeValue(ctx, elem_val);
          JS_FreeValue(ctx, elem_key);
        }
        wota_stack_pop(enc);
        break;
      }
      if (wota_stack_has(enc, replaced)) {
        enc->cycle = 1;
        break;
      }
      wota_stack_push(enc, replaced);
      JSValue to_json = JS_GetPropertyStr(ctx, replaced, "toJSON");
      if (JS_IsFunction(ctx, to_json)) {
        JSValue result = JS_Call(ctx, to_json, replaced, 0, NULL);
        JS_FreeValue(ctx, to_json);
        if (!JS_IsException(result)) {
          wota_encode_value(enc, result, holder, key);
          JS_FreeValue(ctx, result);
        } else
          wota_write_sym(&enc->wb, WOTA_NULL);
        wota_stack_pop(enc);
        break;
      }
      JS_FreeValue(ctx, to_json);
      encode_object_properties(enc, replaced, holder);
      wota_stack_pop(enc);
      break;
    }
    default:
      wota_write_sym(&enc->wb, WOTA_NULL);
      break;
  }
  JS_FreeValue(ctx, replaced);
}

static char *decode_wota_value(JSContext *ctx, char *data_ptr, char *end_ptr, JSValue *out_val, JSValue holder, JSValue key, JSValue reviver)
{
  if ((end_ptr - data_ptr) < 8) {
    *out_val = JS_UNDEFINED;
    return data_ptr;
  }
  uint64_t first_word = *(uint64_t *)data_ptr;
  int type = (int)(first_word & 0xffU);
  switch (type) {
    case WOTA_INT: {
      long long val;
      data_ptr = wota_read_int(&val, data_ptr);
      *out_val = JS_NewInt64(ctx, val);
      break;
    }
    case WOTA_FLOAT: {
      double d;
      data_ptr = wota_read_float(&d, data_ptr);
      *out_val = JS_NewFloat64(ctx, d);
      break;
    }
    case WOTA_SYM: {
      int scode;
      data_ptr = wota_read_sym(&scode, data_ptr);
      if (scode == WOTA_NULL) *out_val = JS_UNDEFINED;
      else if (scode == WOTA_FALSE) *out_val = JS_NewBool(ctx, 0);
      else if (scode == WOTA_TRUE) *out_val = JS_NewBool(ctx, 1);
      else *out_val = JS_UNDEFINED;
      break;
    }
    case WOTA_BLOB: {
      long long blen;
      char *bdata = NULL;
      data_ptr = wota_read_blob(&blen, &bdata, data_ptr);
      *out_val = bdata ? JS_NewArrayBufferCopy(ctx, (uint8_t *)bdata, (size_t)blen) : JS_NewArrayBufferCopy(ctx, NULL, 0);
      if (bdata) free(bdata);
      break;
    }
    case WOTA_TEXT: {
      char *utf8 = NULL;
      data_ptr = wota_read_text(&utf8, data_ptr);
      *out_val = JS_NewString(ctx, utf8 ? utf8 : "");
      if (utf8) free(utf8);
      break;
    }
    case WOTA_ARR: {
      long long c;
      data_ptr = wota_read_array(&c, data_ptr);
      JSValue arr = JS_NewArray(ctx);
      for (long long i = 0; i < c; i++) {
        JSValue elem_val = JS_UNDEFINED;
        data_ptr = decode_wota_value(ctx, data_ptr, end_ptr, &elem_val, arr, JS_NewInt32(ctx, i), reviver);
        JS_SetPropertyUint32(ctx, arr, i, elem_val);
      }
      *out_val = arr;
      break;
    }
    case WOTA_REC: {
      long long c;
      data_ptr = wota_read_record(&c, data_ptr);
      JSValue obj = JS_NewObject(ctx);
      for (long long i = 0; i < c; i++) {
        char *tkey = NULL;
        data_ptr = wota_read_text(&tkey, data_ptr);
        JSValue prop_key = tkey ? JS_NewString(ctx, tkey) : JS_UNDEFINED;
        JSValue sub_val = JS_UNDEFINED;
        data_ptr = decode_wota_value(ctx, data_ptr, end_ptr, &sub_val, obj, prop_key, reviver);
        if (tkey) JS_SetPropertyStr(ctx, obj, tkey, sub_val);
        else JS_FreeValue(ctx, sub_val);
        JS_FreeValue(ctx, prop_key);
        if (tkey) free(tkey);
      }
      *out_val = obj;
      break;
    }
    default:
      data_ptr += 8;
      *out_val = JS_UNDEFINED;
      break;
  }
  if (!JS_IsUndefined(reviver)) {
    JSValue args[2] = { JS_DupValue(ctx, key), JS_DupValue(ctx, *out_val) };
    JSValue revived = JS_Call(ctx, reviver, holder, 2, args);
    JS_FreeValue(ctx, args[0]);
    JS_FreeValue(ctx, args[1]);
    if (!JS_IsException(revived)) {
      JS_FreeValue(ctx, *out_val);
      *out_val = revived;
    } else
      JS_FreeValue(ctx, revived);
  }
  return data_ptr;
}

static JSValue js_wota_encode(JSContext *ctx, JSValueConst this_val, int argc, JSValueConst *argv)
{
  if (argc < 1) return JS_ThrowTypeError(ctx, "wota.encode requires at least 1 argument");
  WotaEncodeContext enc_s, *enc = &enc_s;
  enc->ctx = ctx;
  enc->visited_stack = JS_NewArray(ctx);
  enc->cycle = 0;
  enc->replacer = (argc > 1 && JS_IsFunction(ctx, argv[1])) ? argv[1] : JS_UNDEFINED;
  wota_buffer_init(&enc->wb, 16);
  wota_encode_value(enc, argv[0], JS_UNDEFINED, JS_NewString(ctx, ""));
  if (enc->cycle) {
    JS_FreeValue(ctx, enc->visited_stack);
    wota_buffer_free(&enc->wb);
    return JS_ThrowReferenceError(ctx, "Cannot encode cyclic object with wota");
  }
  JS_FreeValue(ctx, enc->visited_stack);
  size_t total_bytes = enc->wb.size * sizeof(uint64_t);
  JSValue ret = JS_NewArrayBufferCopy(ctx, (uint8_t *)enc->wb.data, total_bytes);
  wota_buffer_free(&enc->wb);
  return ret;
}

static JSValue js_wota_decode(JSContext *ctx, JSValueConst this_val, int argc, JSValueConst *argv)
{
  if (argc < 1) return JS_UNDEFINED;
  size_t len;
  uint8_t *buf = JS_GetArrayBuffer(ctx, &len, argv[0]);
  if (!buf) return JS_UNDEFINED;
  JSValue reviver = (argc > 1 && JS_IsFunction(ctx, argv[1])) ? argv[1] : JS_UNDEFINED;
  char *data_ptr = (char *)buf;
  char *end_ptr = data_ptr + len;
  JSValue result = JS_UNDEFINED;
  JSValue holder = JS_NewObject(ctx);
  decode_wota_value(ctx, data_ptr, end_ptr, &result, holder, JS_NewString(ctx, ""), reviver);
  JS_FreeValue(ctx, holder);
  return result;
}

static const JSCFunctionListEntry js_wota_funcs[] = {
  JS_CFUNC_DEF("encode", 2, js_wota_encode),
  JS_CFUNC_DEF("decode", 2, js_wota_decode),
};

static int js_wota_init(JSContext *ctx, JSModuleDef *m)
{
  JS_SetModuleExportList(ctx, m, js_wota_funcs, sizeof(js_wota_funcs)/sizeof(js_wota_funcs[0]));
  return 0;
}

#ifdef JS_SHARED_LIBRARY
#define JS_INIT_MODULE js_init_module
#else
#define JS_INIT_MODULE js_init_module_wota
#endif

JSModuleDef *JS_INIT_MODULE(JSContext *ctx, const char *module_name)
{
  JSModuleDef *m = JS_NewCModule(ctx, module_name, js_wota_init);
  if (!m) return NULL;
  JS_AddModuleExportList(ctx, m, js_wota_funcs, sizeof(js_wota_funcs)/sizeof(js_wota_funcs[0]));
  return m;
}

JSValue js_wota_use(JSContext *ctx)
{
  JSValue exports = JS_NewObject(ctx);
  JS_SetPropertyFunctionList(ctx, exports, js_wota_funcs, sizeof(js_wota_funcs)/sizeof(js_wota_funcs[0]));
  return exports;
}