let text_decoder = new TextDecoder();
let text_encoder = new TextEncoder();
let log_buf = "";

let uindex = 0;
let indices = [];
let values = [];
let value_map = {};

class MemoryBlock {
  constructor(mem, offset = 0) {
    this.mem = mem;
    this.offset = offset;
  }

  slice(offset) {
    return new MemoryBlock(this.mem, offset);
  }

  getMemory() {
    return new DataView(this.mem, this.offset);
  }

  getU8(offset) {
    return this.getMemory().getUint8(offset, true);
  }

  getU32(offset) {
    return this.getMemory().getUint32(offset, true);
  }

  getU64(offset) {
    const ls = this.getU32(offset);
    const ms = this.getU32(offset + 4);

    return ls + ms * 4294967296;
  }

  getF64(offset) {
    return this.getMemory().getFloat64(offset, true);
  }

  getSlice(offset, len) {
    return new Uint8Array(this.mem, offset, len);
  }

  getString(offset, len) {
    return text_decoder.decode(new Uint8Array(this.mem, offset, len));
  }

  setU8(offset, data) {
    this.getMemory().setUint8(offset, data, true);
  }

  setU32(offset, data) {
    this.getMemory().setUint32(offset, data, true);
  }

  setU64(offset, data) {
    this.getMemory().setUint32(offset, data, true);
    this.getMemory().setUint32(offset + 4, Math.floor(data / 4294967296), true);
  }

  setF64(offset, data) {
    this.getMemory().setFloat64(offset, data, true);
  }

  setString(offset, str) {
    const string = text_encoder.encode(str);
    const buffer = new Uint8Array(this.mem, offset, string.length);
    for (let i = 0; i < string.length; i += 1) {
      buffer[i] = string[i];
    }
  }
}

const sysjs = {
  wasm: undefined,
  buffer: undefined,

  init(wasm) {
    this.wasm = wasm;

    values = [];
    value_map = {};
    this.addValue(globalThis);
  },

  addValue(value) {
    value.__proto__.__uindex = uindex;
    let idx = indices.pop();
    if (idx !== undefined) {
      values[idx] = value;
    } else {
      idx = values.push(value) - 1;
    }
    value_map[uindex] = idx;
    uindex += 1;
    return idx;
  },

  zigCreateMap() {
    return sysjs.addValue(new Map());
  },

  zigCreateArray() {
    return sysjs.addValue(new Array());
  },

  zigCreateString(str, len) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    return sysjs.addValue(memory.getString(str, len));
  },

  zigCreateFunction(id, captures, len) {
    return sysjs.addValue(function () {
      const args = sysjs.addValue(arguments);
      sysjs.wasm.exports.wasmCallFunction(id, args, arguments.length, captures, len);
      const return_value = values[args]["return_value"];
      sysjs.zigCleanupObject(args);
      return return_value;
    });
  },

  getType(value) {
    switch (typeof value) {
      case "object":
        switch (value) {
          case null:
            return 4;
          default:
            return 0;
        }
        break;
      case "number":
        return 1;
      case "boolean":
        return 2;
      case "string":
        return 3;
      case "undefined":
        return 5;
      case "function":
        return 6;
    }
  },

  writeObject(block, data, type) {
    switch (type) {
      case 0:
      case 6:
        block.setU8(0, type);
        block.setU64(8, data);
        break;
      case 1:
        block.setU8(0, 1);
        block.setF64(8, data);
        break;
      case 2:
        block.setU8(0, 2);
        block.setU8(8, data);
        break;
      case 3:
        block.setU8(0, 3);
        block.setU64(8, data);
        break;
      case 4:
        block.setU8(0, 4);
        break;
      case 5:
        block.setU8(0, 5);
        break;
    }
  },

  readObject(block, memory) {
    switch (block.getU8(0)) {
      case 0:
      case 6:
        return values[block.getU64(8)];
        break;
      case 1:
        return block.getF64(8);
        break;
      case 2:
        return Boolean(block.getU8(8));
        break;
      case 3:
        return values[block.getU64(8)];
        break;
      case 4:
        return null;
        break;
      case 5:
        return undefined;
        break;
    }
  },

  getPropertyEx(prop, ret_ptr, offset) {
    let len = undefined;
    const type = this.getType(prop);
    switch (type) {
      case 3:
        len = prop.length;
      case 0:
      case 6:
        if (prop in value_map) {
          prop = value_map[prop.__uindex];
        } else {
          prop = sysjs.addValue(prop);
        }
        break;
    }

    if (len !== undefined) prop.__proto__.length = len;

    let memory = new MemoryBlock(ret_ptr, offset);
    sysjs.writeObject(memory, prop, type);
  },

  getProperty(prop, ret_ptr) {
    return sysjs.getPropertyEx(prop, sysjs.wasm.exports.memory.buffer, ret_ptr);
  },

  zigGetProperty(id, name, len, ret_ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    let prop = values[id][memory.getString(name, len)];
    sysjs.getProperty(prop, ret_ptr);
  },

  zigSetProperty(id, name, len, set_ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    values[id][memory.getString(name, len)] = sysjs.readObject(
      memory.slice(set_ptr),
      memory
    );
  },

  zigDeleteProperty(id, name, len) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    delete values[id][memory.getString(name, len)];
  },

  zigGetIndex(id, index, ret_ptr) {
    let prop = values[id][index];
    sysjs.getProperty(prop, ret_ptr);
  },

  zigSetIndex(id, index, set_ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    values[id][index] = sysjs.readObject(memory.slice(set_ptr), memory);
  },

  zigDeleteIndex(id, index) {
    delete values[id][index];
  },

  zigCopyBytes(id, bytes, expected_length) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    const array = values[id];
    if (array.length != expected_length) {
      throw Error("copyBytes given array of length " + expected_length + " but destination has length " + array.length);
    }
    const slice = memory.getSlice(bytes, array.length);
    array.set(slice);
  },

  zigGetAttributeCount(id) {
    let obj = values[id];
    return Object.keys(obj).length;
  },

  zigCleanupObject(id) {
    const idx = Number(id);
    delete value_map[values[idx].__uindex];
    delete values[idx];
    indices.push(idx);
  },

  zigGetStringLength(val_id) {
    return values[value_map[val_id]].length;
  },

  zigGetString(val_id, ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    memory.setString(ptr, values[value_map[val_id]]);
  },

  zigValueEqual(val, other) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    const val_js = sysjs.readObject(memory.slice(val), memory);
    const other_js = sysjs.readObject(memory.slice(other), memory);
    return val_js === other_js;
  },

  zigValueInstanceOf(val, other) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    const val_js = sysjs.readObject(memory.slice(val), memory);
    const other_js = sysjs.readObject(memory.slice(other), memory);
    return val_js instanceof other_js;
  },

  functionCall(func, this_param, args, args_len, ret_ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    let argv = [];
    for (let i = 0; i < args_len; i += 1) {
      argv.push(sysjs.readObject(memory.slice(args + i * 16), memory));
    }

    let result = func.apply(this_param, argv);

    let length = undefined;
    const type = sysjs.getType(result);
    switch (type) {
      case 3:
        length = result.length;
      case 0:
      case 6:
        result = sysjs.addValue(result);
        break;
    }

    if (length !== undefined) result.__proto__.length = length;

    sysjs.writeObject(memory.slice(ret_ptr), result, type);
  },

  zigFunctionCall(id, name, len, args, args_len, ret_ptr) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    sysjs.functionCall(
      values[id][memory.getString(name, len)],
      values[id],
      args,
      args_len,
      ret_ptr
    );
  },

  zigFunctionInvoke(id, args, args_len, ret_ptr) {
    sysjs.functionCall(values[id], undefined, args, args_len, ret_ptr);
  },

  zigGetParamCount(id) {
    return values[id].length;
  },

  zigConstructType(id, args, args_len) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    let argv = [];
    for (let i = 0; i < args_len; i += 1) {
      argv.push(sysjs.readObject(memory.slice(args + i * 16), memory));
    }

    return sysjs.addValue(new values[id](...argv));
  },

  wzLogWrite(str, len) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    log_buf += memory.getString(str, len);
  },

  wzLogFlush() {
    console.log(log_buf);
    log_buf = "";
  },

  wzPanic(str, len) {
    let memory = new MemoryBlock(sysjs.wasm.exports.memory.buffer);
    throw Error(memory.getString(str, len));
  },
};

export { sysjs };