'use strict';

var fs = require('fs');
var _ = require('lodash');
var acorn = require('acorn');
var walk = require('acorn/dist/walk');

module.exports = {
  parseBundle
};

function parseBundle(bundlePath) {
  var content = fs.readFileSync(bundlePath, 'utf8');
  var ast = acorn.parse(content, {
    sourceType: 'script',
    // I believe in a bright future of ECMAScript!
    // Actually, it's set to `2050` to support the latest ECMAScript version that currently exists.
    // Seems like `acorn` supports such weird option value.
    ecmaVersion: 2050
  });

  var walkState = {
    locations: null
  };

  walk.recursive(ast, walkState, {
    CallExpression(node, state, c) {
      if (state.locations) return;

      var args = node.arguments;

      // Main chunk with webpack loader.
      // Modules are stored in first argument:
      // (function (...) {...})(<modules>)
      if (node.callee.type === 'FunctionExpression' && !node.callee.id && args.length === 1 && isSimpleModulesList(args[0])) {
        state.locations = getModulesLocations(args[0]);
        return;
      }

      // Async Webpack < v4 chunk without webpack loader.
      // webpackJsonp([<chunks>], <modules>, ...)
      // As function name may be changed with `output.jsonpFunction` option we can't rely on it's default name.
      if (node.callee.type === 'Identifier' && mayBeAsyncChunkArguments(args) && isModulesList(args[1])) {
        state.locations = getModulesLocations(args[1]);
        return;
      }

      // Async Webpack v4 chunk without webpack loader.
      // (window.webpackJsonp=window.webpackJsonp||[]).push([[<chunks>], <modules>, ...]);
      // As function name may be changed with `output.jsonpFunction` option we can't rely on it's default name.
      if (isAsyncChunkPushExpression(node)) {
        state.locations = getModulesLocations(args[0].elements[1]);
        return;
      }

      // Walking into arguments because some of plugins (e.g. `DedupePlugin`) or some Webpack
      // features (e.g. `umd` library output) can wrap modules list into additional IIFE.
      _.each(args, function (arg) {
        return c(arg, state);
      });
    }
  });

  var modules = void 0;

  if (walkState.locations) {
    modules = _.mapValues(walkState.locations, function (loc) {
      return content.slice(loc.start, loc.end);
    });
  } else {
    modules = {};
  }

  return {
    src: content,
    modules
  };
}

function isModulesList(node) {
  return isSimpleModulesList(node) ||
  // Modules are contained in expression `Array([minimum ID]).concat([<module>, <module>, ...])`
  isOptimizedModulesArray(node);
}

function isSimpleModulesList(node) {
  return (
    // Modules are contained in hash. Keys are module ids.
    isModulesHash(node) ||
    // Modules are contained in array. Indexes are module ids.
    isModulesArray(node)
  );
}

function isModulesHash(node) {
  return node.type === 'ObjectExpression' && _(node.properties).map('value').every(isModuleWrapper);
}

function isModulesArray(node) {
  return node.type === 'ArrayExpression' && _.every(node.elements, function (elem) {
    return (
      // Some of array items may be skipped because there is no module with such id
      !elem || isModuleWrapper(elem)
    );
  });
}

function isOptimizedModulesArray(node) {
  // Checking whether modules are contained in `Array(<minimum ID>).concat(...modules)` array:
  // https://github.com/webpack/webpack/blob/v1.14.0/lib/Template.js#L91
  // The `<minimum ID>` + array indexes are module ids
  return node.type === 'CallExpression' && node.callee.type === 'MemberExpression' &&
  // Make sure the object called is `Array(<some number>)`
  node.callee.object.type === 'CallExpression' && node.callee.object.callee.type === 'Identifier' && node.callee.object.callee.name === 'Array' && node.callee.object.arguments.length === 1 && isNumericId(node.callee.object.arguments[0]) &&
  // Make sure the property X called for `Array(<some number>).X` is `concat`
  node.callee.property.type === 'Identifier' && node.callee.property.name === 'concat' &&
  // Make sure exactly one array is passed in to `concat`
  node.arguments.length === 1 && isModulesArray(node.arguments[0]);
}

function isModuleWrapper(node) {
  return (
    // It's an anonymous function expression that wraps module
    (node.type === 'FunctionExpression' || node.type === 'ArrowFunctionExpression') && !node.id ||
    // If `DedupePlugin` is used it can be an ID of duplicated module...
    isModuleId(node) ||
    // or an array of shape [<module_id>, ...args]
    node.type === 'ArrayExpression' && node.elements.length > 1 && isModuleId(node.elements[0])
  );
}

function isModuleId(node) {
  return node.type === 'Literal' && (isNumericId(node) || typeof node.value === 'string');
}

function isNumericId(node) {
  return node.type === 'Literal' && Number.isInteger(node.value) && node.value >= 0;
}

function isChunkIds(node) {
  // Array of numeric or string ids. Chunk IDs are strings when NamedChunksPlugin is used
  return node.type === 'ArrayExpression' && _.every(node.elements, isModuleId);
}

function isAsyncChunkPushExpression(node) {
  var callee = node.callee,
      args = node.arguments;


  return callee.type === 'MemberExpression' && callee.property.name === 'push' && callee.object.type === 'AssignmentExpression' && callee.object.left.object && (callee.object.left.object.name === 'window' ||
  // Webpack 4 uses `this` instead of `window`
  callee.object.left.object.type === 'ThisExpression') && args.length === 1 && args[0].type === 'ArrayExpression' && mayBeAsyncChunkArguments(args[0].elements) && isModulesList(args[0].elements[1]);
}

function mayBeAsyncChunkArguments(args) {
  return args.length >= 2 && isChunkIds(args[0]);
}

function getModulesLocations(node) {
  if (node.type === 'ObjectExpression') {
    // Modules hash
    var modulesNodes = node.properties;

    return _.transform(modulesNodes, function (result, moduleNode) {
      var moduleId = moduleNode.key.name || moduleNode.key.value;

      result[moduleId] = getModuleLocation(moduleNode.value);
    }, {});
  }

  var isOptimizedArray = node.type === 'CallExpression';

  if (node.type === 'ArrayExpression' || isOptimizedArray) {
    // Modules array or optimized array
    var minId = isOptimizedArray ?
    // Get the [minId] value from the Array() call first argument literal value
    node.callee.object.arguments[0].value :
    // `0` for simple array
    0;
    var _modulesNodes = isOptimizedArray ?
    // The modules reside in the `concat()` function call arguments
    node.arguments[0].elements : node.elements;

    return _.transform(_modulesNodes, function (result, moduleNode, i) {
      if (!moduleNode) return;
      result[i + minId] = getModuleLocation(moduleNode);
    }, {});
  }

  return {};
}

function getModuleLocation(node) {
  return {
    start: node.start,
    end: node.end
  };
}