/*
 * Copyright 2015 WebAssembly Community Group participants
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

function integrateWasmJS(Module) {
  // wasm.js has several methods for creating the compiled code module here:
  //  * 'native-wasm' : use native WebAssembly support in the browser
  //  * 'interpret-s-expr': load s-expression code from a .wast and interpret
  //  * 'interpret-binary': load binary wasm and interpret
  //  * 'interpret-asm2wasm': load asm.js code, translate to wasm, and interpret
  //  * 'asmjs': no wasm, just load the asm.js code and use that (good for testing)
  // The method can be set at compile time (BINARYEN_METHOD), or runtime by setting Module['wasmJSMethod'].
  // The method can be a comma-separated list, in which case, we will try the
  // options one by one. Some of them can fail gracefully, and then we can try
  // the next.

  // inputs

  var method = Module['wasmJSMethod'] || {{{ wasmJSMethod }}} || 'native-wasm,interpret-s-expr'; // by default, try native and then .wast

  var wasmTextFile = Module['wasmTextFile'] || {{{ wasmTextFile }}};
  var wasmBinaryFile = Module['wasmBinaryFile'] || {{{ wasmBinaryFile }}};
  var asmjsCodeFile = Module['asmjsCodeFile'] || {{{ asmjsCodeFile }}};

  // utilities

  var wasmPageSize = 64*1024;

  var asm2wasmImports = { // special asm2wasm imports
    "f64-rem": function(x, y) {
      return x % y;
    },
    "f64-to-int": function(x) {
      return x | 0;
    },
    "debugger": function() {
      debugger;
    },
  };

  var info = {
    'global': null,
    'env': null,
    'asm2wasm': asm2wasmImports,
    'parent': Module // Module inside wasm-js.cpp refers to wasm-js.cpp; this allows access to the outside program.
  };

  var exports = null;

  function lookupImport(mod, base) {
    var lookup = info;
    if (mod.indexOf('.') < 0) {
      lookup = (lookup || {})[mod];
    } else {
      var parts = mod.split('.');
      lookup = (lookup || {})[parts[0]];
      lookup = (lookup || {})[parts[1]];
    }
    if (base) {
      lookup = (lookup || {})[base];
    }
    if (lookup === undefined) {
      abort('bad lookupImport to (' + mod + ').' + base);
    }
    return lookup;
  }

  function mergeMemory(newBuffer) {
    // The wasm instance creates its memory. But static init code might have written to
    // buffer already, including the mem init file, and we must copy it over in a proper merge.
    // TODO: avoid this copy, by avoiding such static init writes
    // TODO: in shorter term, just copy up to the last static init write
    var oldBuffer = Module['buffer'];
    if (newBuffer.byteLength < oldBuffer.byteLength) {
      Module['printErr']('the new buffer in mergeMemory is smaller than the previous one. in native wasm, we should grow memory here');
    }
    var oldView = new Int8Array(oldBuffer);
    var newView = new Int8Array(newBuffer);
    if ({{{ WASM_BACKEND }}}) {
      // memory segments arrived in the wast, do not trample them
      oldView.set(newView.subarray(STATIC_BASE, STATIC_BASE + STATIC_BUMP), STATIC_BASE);
    }
    newView.set(oldView);
    updateGlobalBuffer(newBuffer);
    updateGlobalBufferViews();
    Module['reallocBuffer'] = function(size) {
      size = Math.ceil(size / wasmPageSize) * wasmPageSize; // round up to wasm page size
      var old = Module['buffer'];
      exports['__growWasmMemory'](size / wasmPageSize); // tiny wasm method that just does grow_memory
      return Module['buffer'] !== old ? Module['buffer'] : null; // if it was reallocated, it changed
    };
  }

  var WasmTypes = {
    none: 0,
    i32: 1,
    i64: 2,
    f32: 3,
    f64: 4
  };

  // wasm lacks globals, so asm2wasm maps them into locations in memory. that information cannot
  // be present in the wasm output of asm2wasm, so we store it in a side file. If we load asm2wasm
  // output, either generated ahead of time or on the client, we need to apply those mapped
  // globals after loading the module.
  function applyMappedGlobals(globalsFileBase) {
    var mappedGlobals = JSON.parse(Module['read'](globalsFileBase + '.mappedGlobals'));
    for (var name in mappedGlobals) {
      var global = mappedGlobals[name];
      if (!global.import) continue; // non-imports are initialized to zero in the typed array anyhow, so nothing to do here
      var value = lookupImport(global.module, global.base);
      var address = global.address;
      switch (global.type) {
        case WasmTypes.i32: Module['HEAP32'][address >> 2] = value; break;
        case WasmTypes.f32: Module['HEAPF32'][address >> 2] = value; break;
        case WasmTypes.f64: Module['HEAPF64'][address >> 3] = value; break;
        default: abort();
      }
    }
  }

  function fixImports(imports) {
    if (!{{{ WASM_BACKEND }}}) return imports;
    var ret = {};
    for (var i in imports) {
      var fixed = i;
      if (fixed[0] == '_') fixed = fixed.substr(1);
      ret[fixed] = imports[i];
    }
    return ret;
  }

  function getBinary() {
    var binary;
    if (ENVIRONMENT_IS_WEB || ENVIRONMENT_IS_WORKER) {
      binary = Module['wasmBinary'];
      assert(binary, "on the web, we need the wasm binary to be preloaded and set on Module['wasmBinary']. emcc.py will do that for you when generating HTML (but not JS)");
      binary = new Uint8Array(binary);
    } else {
      binary = Module['readBinary'](wasmBinaryFile);
    }
    return binary;
  }

  // do-method functions

  function doJustAsm() {
    if (typeof Module['asm'] !== 'function') {
      // you can load the .asm.js file before this, to avoid this sync xhr and eval
      eval(Module['read'](asmjsCodeFile));
    }
    if (typeof Module['asm'] !== 'function') {
      // evalling the asm.js file should have set this
      Module['printErr']('asm evalling did not set the module properly');
      return false;
    }
    return true;
  }

  function doNativeWasm() {
    if (typeof Wasm !== 'object') {
      Module['printErr']('no native wasm support detected');
      return false;
    }

    // Provide an "asm.js function" for the application, called to "link" the asm.js module. We instantiate
    // the wasm module at that time, and it receives imports and provides exports and so forth, the app
    // doesn't need to care that it is wasm and not asm.
    Module['asm'] = function(global, env, providedBuffer) {
      global = fixImports(global);
      env = fixImports(env);

      // Load the wasm module and create an instance of using native support in the JS engine.
      info['global'] = {
        'NaN': NaN,
        'Infinity': Infinity
      };
      info['global.Math'] = global.Math;
      info['env'] = env;
      var instance;
      instance = Wasm.instantiateModule(getBinary(), info);
      exports = instance.exports;
      mergeMemory(exports.memory);

      applyMappedGlobals(wasmBinaryFile);

      return exports;
    };

    Module["usingWasm"] = true;

    return true;
  }

  function doWasmPolyfill(method) {
    if (typeof WasmJS !== 'function') {
      Module['printErr']('WasmJS not detected - polyfill not bundled?');
      return false;
    }

    // Use wasm.js to polyfill and execute code in a wasm interpreter.
    var wasmJS = WasmJS({});

    // XXX don't be confused. Module here is in the outside program. wasmJS is the inner wasm-js.cpp.
    wasmJS['outside'] = Module; // Inside wasm-js.cpp, Module['outside'] reaches the outside module.

    // Information for the instance of the module.
    wasmJS['info'] = info;

    wasmJS['lookupImport'] = lookupImport;

    // The asm.js function, called to "link" the asm.js module. At that time, we are provided imports
    // and respond with exports, and so forth.
    Module['asm'] = function(global, env, providedBuffer) {
      global = fixImports(global);
      env = fixImports(env);

      assert(providedBuffer === Module['buffer']); // we should not even need to pass it as a 3rd arg for wasm, but that's the asm.js way.

      info.global = global;
      info.env = env;

      wasmJS['providedTotalMemory'] = Module['buffer'].byteLength;

      // Prepare to generate wasm, using either asm2wasm or s-exprs
      var code;
      if (method === 'interpret-binary') {
        code = getBinary();
      } else {
        code = Module['read'](method == 'interpret-asm2wasm' ? asmjsCodeFile : wasmTextFile);
      }
      var temp;
      if (method == 'interpret-asm2wasm') {
        temp = wasmJS['_malloc'](code.length + 1);
        wasmJS['writeAsciiToMemory'](code, temp);
        wasmJS['_load_asm2wasm'](temp);
      } else if (method === 'interpret-s-expr') {
        temp = wasmJS['_malloc'](code.length + 1);
        wasmJS['writeAsciiToMemory'](code, temp);
        wasmJS['_load_s_expr2wasm'](temp);
      } else if (method === 'interpret-binary') {
        temp = wasmJS['_malloc'](code.length);
        wasmJS['HEAPU8'].set(code, temp);
        wasmJS['_load_binary2wasm'](temp, code.length);
      } else {
        throw 'what? ' + method;
      }
      wasmJS['_free'](temp);

      wasmJS['_instantiate'](temp);

      if (Module['newBuffer']) {
        mergeMemory(Module['newBuffer']);
        Module['newBuffer'] = null;
      }

      if (method == 'interpret-s-expr') {
        applyMappedGlobals(wasmTextFile);
      } else if (method == 'interpret-binary') {
        applyMappedGlobals(wasmBinaryFile);
      }

      exports = wasmJS['asmExports'];

      return exports;
    };

    return true;
  }

  // use the right method

  var methods = method.split(',');
  for (var i = 0; i < methods.length; i++) {
    var curr = methods[i];
    //Module['printErr']('using wasm/js method: ' + curr);
    if (curr === 'native-wasm') {
      if (doNativeWasm()) return;
    } else if (curr === 'asmjs') {
      if (doJustAsm()) return;
    } else if (curr === 'interpret-asm2wasm' || curr === 'interpret-s-expr' || curr === 'interpret-binary') {
      if (doWasmPolyfill(curr)) return;
    } else {
      throw 'bad method: ' + curr;
    }
  }
  throw 'no wasm method succeeded';
}