javascript-compiler.js

import { COMPILER_REVISION, REVISION_CHANGES, log } from "../base";

function Literal(value) {
  this.value = value;
}

function JavaScriptCompiler() {}

JavaScriptCompiler.prototype = {
  // PUBLIC API: You can override these methods in a subclass to provide
  // alternative compiled forms for name lookup and buffering semantics
  nameLookup: function(parent, name /* , type*/) {
    var wrap,
        ret;
    if (parent.indexOf('depth') === 0) {
      wrap = true;
    }

    if (/^[0-9]+$/.test(name)) {
      ret = parent + "[" + name + "]";
    } else if (JavaScriptCompiler.isValidJavaScriptVariableName(name)) {
      ret = parent + "." + name;
    }
    else {
      ret = parent + "['" + name + "']";
    }

    if (wrap) {
      return '(' + parent + ' && ' + ret + ')';
    } else {
      return ret;
    }
  },

  appendToBuffer: function(string) {
    if (this.environment.isSimple) {
      return "return " + string + ";";
    } else {
      return {
        appendToBuffer: true,
        content: string,
        toString: function() { return "buffer += " + string + ";"; }
      };
    }
  },

  initializeBuffer: function() {
    return this.quotedString("");
  },

  namespace: "Handlebars",
  // END PUBLIC API

  compile: function(environment, options, context, asObject) {
    this.environment = environment;
    this.options = options || {};

    log('debug', this.environment.disassemble() + "\n\n");

    this.name = this.environment.name;
    this.isChild = !!context;
    this.context = context || {
      programs: [],
      environments: [],
      aliases: { }
    };

    this.preamble();

    this.stackSlot = 0;
    this.stackVars = [];
    this.registers = { list: [] };
    this.compileStack = [];
    this.inlineStack = [];

    this.compileChildren(environment, options);

    var opcodes = environment.opcodes, opcode;

    this.i = 0;

    for(var l=opcodes.length; this.i<l; this.i++) {
      opcode = opcodes[this.i];

      if(opcode.opcode === 'DECLARE') {
        this[opcode.name] = opcode.value;
      } else {
        this[opcode.opcode].apply(this, opcode.args);
      }

      // Reset the stripNext flag if it was not set by this operation.
      if (opcode.opcode !== this.stripNext) {
        this.stripNext = false;
      }
    }

    // Flush any trailing content that might be pending.
    this.pushSource('');

    return this.createFunctionContext(asObject);
  },

  preamble: function() {
    var out = [];

    if (!this.isChild) {
      var namespace = this.namespace;

      var copies = "helpers = this.merge(helpers, " + namespace + ".helpers);";
      if (this.environment.usePartial) { copies = copies + " partials = this.merge(partials, " + namespace + ".partials);"; }
      if (this.options.data) { copies = copies + " data = data || {};"; }
      out.push(copies);
    } else {
      out.push('');
    }

    if (!this.environment.isSimple) {
      out.push(", buffer = " + this.initializeBuffer());
    } else {
      out.push("");
    }

    // track the last context pushed into place to allow skipping the
    // getContext opcode when it would be a noop
    this.lastContext = 0;
    this.source = out;
  },

  createFunctionContext: function(asObject) {
    var locals = this.stackVars.concat(this.registers.list);

    if(locals.length > 0) {
      this.source[1] = this.source[1] + ", " + locals.join(", ");
    }

    // Generate minimizer alias mappings
    if (!this.isChild) {
      for (var alias in this.context.aliases) {
        if (this.context.aliases.hasOwnProperty(alias)) {
          this.source[1] = this.source[1] + ', ' + alias + '=' + this.context.aliases[alias];
        }
      }
    }

    if (this.source[1]) {
      this.source[1] = "var " + this.source[1].substring(2) + ";";
    }

    // Merge children
    if (!this.isChild) {
      this.source[1] += '\n' + this.context.programs.join('\n') + '\n';
    }

    if (!this.environment.isSimple) {
      this.pushSource("return buffer;");
    }

    var params = this.isChild ? ["depth0", "data"] : ["Handlebars", "depth0", "helpers", "partials", "data"];

    for(var i=0, l=this.environment.depths.list.length; i<l; i++) {
      params.push("depth" + this.environment.depths.list[i]);
    }

    // Perform a second pass over the output to merge content when possible
    var source = this.mergeSource();

    if (!this.isChild) {
      var revision = COMPILER_REVISION,
          versions = REVISION_CHANGES[revision];
      source = "this.compilerInfo = ["+revision+",'"+versions+"'];\n"+source;
    }

    if (asObject) {
      params.push(source);

      return Function.apply(this, params);
    } else {
      var functionSource = 'function ' + (this.name || '') + '(' + params.join(',') + ') {\n  ' + source + '}';
      log('debug', functionSource + "\n\n");
      return functionSource;
    }
  },
  mergeSource: function() {
    // WARN: We are not handling the case where buffer is still populated as the source should
    // not have buffer append operations as their final action.
    var source = '',
        buffer;
    for (var i = 0, len = this.source.length; i < len; i++) {
      var line = this.source[i];
      if (line.appendToBuffer) {
        if (buffer) {
          buffer = buffer + '\n    + ' + line.content;
        } else {
          buffer = line.content;
        }
      } else {
        if (buffer) {
          source += 'buffer += ' + buffer + ';\n  ';
          buffer = undefined;
        }
        source += line + '\n  ';
      }
    }
    return source;
  },

  // [blockValue]
  //
  // On stack, before: hash, inverse, program, value
  // On stack, after: return value of blockHelperMissing
  //
  // The purpose of this opcode is to take a block of the form
  // `{{#foo}}...{{/foo}}`, resolve the value of `foo`, and
  // replace it on the stack with the result of properly
  // invoking blockHelperMissing.
  blockValue: function() {
    this.context.aliases.blockHelperMissing = 'helpers.blockHelperMissing';

    var params = ["depth0"];
    this.setupParams(0, params);

    this.replaceStack(function(current) {
      params.splice(1, 0, current);
      return "blockHelperMissing.call(" + params.join(", ") + ")";
    });
  },

  // [ambiguousBlockValue]
  //
  // On stack, before: hash, inverse, program, value
  // Compiler value, before: lastHelper=value of last found helper, if any
  // On stack, after, if no lastHelper: same as [blockValue]
  // On stack, after, if lastHelper: value
  ambiguousBlockValue: function() {
    this.context.aliases.blockHelperMissing = 'helpers.blockHelperMissing';

    var params = ["depth0"];
    this.setupParams(0, params);

    var current = this.topStack();
    params.splice(1, 0, current);

    // Use the options value generated from the invocation
    params[params.length-1] = 'options';

    this.pushSource("if (!" + this.lastHelper + ") { " + current + " = blockHelperMissing.call(" + params.join(", ") + "); }");
  },

  // [appendContent]
  //
  // On stack, before: ...
  // On stack, after: ...
  //
  // Appends the string value of `content` to the current buffer
  appendContent: function(content) {
    if (this.pendingContent) {
      content = this.pendingContent + content;
    }
    if (this.stripNext) {
      content = content.replace(/^\s+/, '');
    }

    this.pendingContent = content;
  },

  // [strip]
  //
  // On stack, before: ...
  // On stack, after: ...
  //
  // Removes any trailing whitespace from the prior content node and flags
  // the next operation for stripping if it is a content node.
  strip: function() {
    if (this.pendingContent) {
      this.pendingContent = this.pendingContent.replace(/\s+$/, '');
    }
    this.stripNext = 'strip';
  },

  // [append]
  //
  // On stack, before: value, ...
  // On stack, after: ...
  //
  // Coerces `value` to a String and appends it to the current buffer.
  //
  // If `value` is truthy, or 0, it is coerced into a string and appended
  // Otherwise, the empty string is appended
  append: function() {
    // Force anything that is inlined onto the stack so we don't have duplication
    // when we examine local
    this.flushInline();
    var local = this.popStack();
    this.pushSource("if(" + local + " || " + local + " === 0) { " + this.appendToBuffer(local) + " }");
    if (this.environment.isSimple) {
      this.pushSource("else { " + this.appendToBuffer("''") + " }");
    }
  },

  // [appendEscaped]
  //
  // On stack, before: value, ...
  // On stack, after: ...
  //
  // Escape `value` and append it to the buffer
  appendEscaped: function() {
    this.context.aliases.escapeExpression = 'this.escapeExpression';

    this.pushSource(this.appendToBuffer("escapeExpression(" + this.popStack() + ")"));
  },

  // [getContext]
  //
  // On stack, before: ...
  // On stack, after: ...
  // Compiler value, after: lastContext=depth
  //
  // Set the value of the `lastContext` compiler value to the depth
  getContext: function(depth) {
    if(this.lastContext !== depth) {
      this.lastContext = depth;
    }
  },

  // [lookupOnContext]
  //
  // On stack, before: ...
  // On stack, after: currentContext[name], ...
  //
  // Looks up the value of `name` on the current context and pushes
  // it onto the stack.
  lookupOnContext: function(name) {
    this.push(this.nameLookup('depth' + this.lastContext, name, 'context'));
  },

  // [pushContext]
  //
  // On stack, before: ...
  // On stack, after: currentContext, ...
  //
  // Pushes the value of the current context onto the stack.
  pushContext: function() {
    this.pushStackLiteral('depth' + this.lastContext);
  },

  // [resolvePossibleLambda]
  //
  // On stack, before: value, ...
  // On stack, after: resolved value, ...
  //
  // If the `value` is a lambda, replace it on the stack by
  // the return value of the lambda
  resolvePossibleLambda: function() {
    this.context.aliases.functionType = '"function"';

    this.replaceStack(function(current) {
      return "typeof " + current + " === functionType ? " + current + ".apply(depth0) : " + current;
    });
  },

  // [lookup]
  //
  // On stack, before: value, ...
  // On stack, after: value[name], ...
  //
  // Replace the value on the stack with the result of looking
  // up `name` on `value`
  lookup: function(name) {
    this.replaceStack(function(current) {
      return current + " == null || " + current + " === false ? " + current + " : " + this.nameLookup(current, name, 'context');
    });
  },

  // [lookupData]
  //
  // On stack, before: ...
  // On stack, after: data, ...
  //
  // Push the data lookup operator
  lookupData: function() {
    this.push('data');
  },

  // [pushStringParam]
  //
  // On stack, before: ...
  // On stack, after: string, currentContext, ...
  //
  // This opcode is designed for use in string mode, which
  // provides the string value of a parameter along with its
  // depth rather than resolving it immediately.
  pushStringParam: function(string, type) {
    this.pushStackLiteral('depth' + this.lastContext);

    this.pushString(type);

    if (typeof string === 'string') {
      this.pushString(string);
    } else {
      this.pushStackLiteral(string);
    }
  },

  emptyHash: function() {
    this.pushStackLiteral('{}');

    if (this.options.stringParams) {
      this.register('hashTypes', '{}');
      this.register('hashContexts', '{}');
    }
  },
  pushHash: function() {
    this.hash = {values: [], types: [], contexts: []};
  },
  popHash: function() {
    var hash = this.hash;
    this.hash = undefined;

    if (this.options.stringParams) {
      this.register('hashContexts', '{' + hash.contexts.join(',') + '}');
      this.register('hashTypes', '{' + hash.types.join(',') + '}');
    }
    this.push('{\n    ' + hash.values.join(',\n    ') + '\n  }');
  },

  // [pushString]
  //
  // On stack, before: ...
  // On stack, after: quotedString(string), ...
  //
  // Push a quoted version of `string` onto the stack
  pushString: function(string) {
    this.pushStackLiteral(this.quotedString(string));
  },

  // [push]
  //
  // On stack, before: ...
  // On stack, after: expr, ...
  //
  // Push an expression onto the stack
  push: function(expr) {
    this.inlineStack.push(expr);
    return expr;
  },

  // [pushLiteral]
  //
  // On stack, before: ...
  // On stack, after: value, ...
  //
  // Pushes a value onto the stack. This operation prevents
  // the compiler from creating a temporary variable to hold
  // it.
  pushLiteral: function(value) {
    this.pushStackLiteral(value);
  },

  // [pushProgram]
  //
  // On stack, before: ...
  // On stack, after: program(guid), ...
  //
  // Push a program expression onto the stack. This takes
  // a compile-time guid and converts it into a runtime-accessible
  // expression.
  pushProgram: function(guid) {
    if (guid != null) {
      this.pushStackLiteral(this.programExpression(guid));
    } else {
      this.pushStackLiteral(null);
    }
  },

  // [invokeHelper]
  //
  // On stack, before: hash, inverse, program, params..., ...
  // On stack, after: result of helper invocation
  //
  // Pops off the helper's parameters, invokes the helper,
  // and pushes the helper's return value onto the stack.
  //
  // If the helper is not found, `helperMissing` is called.
  invokeHelper: function(paramSize, name) {
    this.context.aliases.helperMissing = 'helpers.helperMissing';

    var helper = this.lastHelper = this.setupHelper(paramSize, name, true);
    var nonHelper = this.nameLookup('depth' + this.lastContext, name, 'context');

    this.push(helper.name + ' || ' + nonHelper);
    this.replaceStack(function(name) {
      return name + ' ? ' + name + '.call(' +
          helper.callParams + ") " + ": helperMissing.call(" +
          helper.helperMissingParams + ")";
    });
  },

  // [invokeKnownHelper]
  //
  // On stack, before: hash, inverse, program, params..., ...
  // On stack, after: result of helper invocation
  //
  // This operation is used when the helper is known to exist,
  // so a `helperMissing` fallback is not required.
  invokeKnownHelper: function(paramSize, name) {
    var helper = this.setupHelper(paramSize, name);
    this.push(helper.name + ".call(" + helper.callParams + ")");
  },

  // [invokeAmbiguous]
  //
  // On stack, before: hash, inverse, program, params..., ...
  // On stack, after: result of disambiguation
  //
  // This operation is used when an expression like `{{foo}}`
  // is provided, but we don't know at compile-time whether it
  // is a helper or a path.
  //
  // This operation emits more code than the other options,
  // and can be avoided by passing the `knownHelpers` and
  // `knownHelpersOnly` flags at compile-time.
  invokeAmbiguous: function(name, helperCall) {
    this.context.aliases.functionType = '"function"';

    this.pushStackLiteral('{}');    // Hash value
    var helper = this.setupHelper(0, name, helperCall);

    var helperName = this.lastHelper = this.nameLookup('helpers', name, 'helper');

    var nonHelper = this.nameLookup('depth' + this.lastContext, name, 'context');
    var nextStack = this.nextStack();

    this.pushSource('if (' + nextStack + ' = ' + helperName + ') { ' + nextStack + ' = ' + nextStack + '.call(' + helper.callParams + '); }');
    this.pushSource('else { ' + nextStack + ' = ' + nonHelper + '; ' + nextStack + ' = typeof ' + nextStack + ' === functionType ? ' + nextStack + '.call(' + helper.callParams + ') : ' + nextStack + '; }');
  },

  // [invokePartial]
  //
  // On stack, before: context, ...
  // On stack after: result of partial invocation
  //
  // This operation pops off a context, invokes a partial with that context,
  // and pushes the result of the invocation back.
  invokePartial: function(name) {
    var params = [this.nameLookup('partials', name, 'partial'), "'" + name + "'", this.popStack(), "helpers", "partials"];

    if (this.options.data) {
      params.push("data");
    }

    this.context.aliases.self = "this";
    this.push("self.invokePartial(" + params.join(", ") + ")");
  },

  // [assignToHash]
  //
  // On stack, before: value, hash, ...
  // On stack, after: hash, ...
  //
  // Pops a value and hash off the stack, assigns `hash[key] = value`
  // and pushes the hash back onto the stack.
  assignToHash: function(key) {
    var value = this.popStack(),
        context,
        type;

    if (this.options.stringParams) {
      type = this.popStack();
      context = this.popStack();
    }

    var hash = this.hash;
    if (context) {
      hash.contexts.push("'" + key + "': " + context);
    }
    if (type) {
      hash.types.push("'" + key + "': " + type);
    }
    hash.values.push("'" + key + "': (" + value + ")");
  },

  // HELPERS

  compiler: JavaScriptCompiler,

  compileChildren: function(environment, options) {
    var children = environment.children, child, compiler;

    for(var i=0, l=children.length; i<l; i++) {
      child = children[i];
      compiler = new this.compiler();

      var index = this.matchExistingProgram(child);

      if (index == null) {
        this.context.programs.push('');     // Placeholder to prevent name conflicts for nested children
        index = this.context.programs.length;
        child.index = index;
        child.name = 'program' + index;
        this.context.programs[index] = compiler.compile(child, options, this.context);
        this.context.environments[index] = child;
      } else {
        child.index = index;
        child.name = 'program' + index;
      }
    }
  },
  matchExistingProgram: function(child) {
    for (var i = 0, len = this.context.environments.length; i < len; i++) {
      var environment = this.context.environments[i];
      if (environment && environment.equals(child)) {
        return i;
      }
    }
  },

  programExpression: function(guid) {
    this.context.aliases.self = "this";

    if(guid == null) {
      return "self.noop";
    }

    var child = this.environment.children[guid],
        depths = child.depths.list, depth;

    var programParams = [child.index, child.name, "data"];

    for(var i=0, l = depths.length; i<l; i++) {
      depth = depths[i];

      if(depth === 1) { programParams.push("depth0"); }
      else { programParams.push("depth" + (depth - 1)); }
    }

    return (depths.length === 0 ? "self.program(" : "self.programWithDepth(") + programParams.join(", ") + ")";
  },

  register: function(name, val) {
    this.useRegister(name);
    this.pushSource(name + " = " + val + ";");
  },

  useRegister: function(name) {
    if(!this.registers[name]) {
      this.registers[name] = true;
      this.registers.list.push(name);
    }
  },

  pushStackLiteral: function(item) {
    return this.push(new Literal(item));
  },

  pushSource: function(source) {
    if (this.pendingContent) {
      this.source.push(this.appendToBuffer(this.quotedString(this.pendingContent)));
      this.pendingContent = undefined;
    }

    if (source) {
      this.source.push(source);
    }
  },

  pushStack: function(item) {
    this.flushInline();

    var stack = this.incrStack();
    if (item) {
      this.pushSource(stack + " = " + item + ";");
    }
    this.compileStack.push(stack);
    return stack;
  },

  replaceStack: function(callback) {
    var prefix = '',
        inline = this.isInline(),
        stack;

    // If we are currently inline then we want to merge the inline statement into the
    // replacement statement via ','
    if (inline) {
      var top = this.popStack(true);

      if (top instanceof Literal) {
        // Literals do not need to be inlined
        stack = top.value;
      } else {
        // Get or create the current stack name for use by the inline
        var name = this.stackSlot ? this.topStackName() : this.incrStack();

        prefix = '(' + this.push(name) + ' = ' + top + '),';
        stack = this.topStack();
      }
    } else {
      stack = this.topStack();
    }

    var item = callback.call(this, stack);

    if (inline) {
      if (this.inlineStack.length || this.compileStack.length) {
        this.popStack();
      }
      this.push('(' + prefix + item + ')');
    } else {
      // Prevent modification of the context depth variable. Through replaceStack
      if (!/^stack/.test(stack)) {
        stack = this.nextStack();
      }

      this.pushSource(stack + " = (" + prefix + item + ");");
    }
    return stack;
  },

  nextStack: function() {
    return this.pushStack();
  },

  incrStack: function() {
    this.stackSlot++;
    if(this.stackSlot > this.stackVars.length) { this.stackVars.push("stack" + this.stackSlot); }
    return this.topStackName();
  },
  topStackName: function() {
    return "stack" + this.stackSlot;
  },
  flushInline: function() {
    var inlineStack = this.inlineStack;
    if (inlineStack.length) {
      this.inlineStack = [];
      for (var i = 0, len = inlineStack.length; i < len; i++) {
        var entry = inlineStack[i];
        if (entry instanceof Literal) {
          this.compileStack.push(entry);
        } else {
          this.pushStack(entry);
        }
      }
    }
  },
  isInline: function() {
    return this.inlineStack.length;
  },

  popStack: function(wrapped) {
    var inline = this.isInline(),
        item = (inline ? this.inlineStack : this.compileStack).pop();

    if (!wrapped && (item instanceof Literal)) {
      return item.value;
    } else {
      if (!inline) {
        this.stackSlot--;
      }
      return item;
    }
  },

  topStack: function(wrapped) {
    var stack = (this.isInline() ? this.inlineStack : this.compileStack),
        item = stack[stack.length - 1];

    if (!wrapped && (item instanceof Literal)) {
      return item.value;
    } else {
      return item;
    }
  },

  quotedString: function(str) {
    return '"' + str
      .replace(/\\/g, '\\\\')
      .replace(/"/g, '\\"')
      .replace(/\n/g, '\\n')
      .replace(/\r/g, '\\r')
      .replace(/\u2028/g, '\\u2028')   // Per Ecma-262 7.3 + 7.8.4
      .replace(/\u2029/g, '\\u2029') + '"';
  },

  setupHelper: function(paramSize, name, missingParams) {
    var params = [];
    this.setupParams(paramSize, params, missingParams);
    var foundHelper = this.nameLookup('helpers', name, 'helper');

    return {
      params: params,
      name: foundHelper,
      callParams: ["depth0"].concat(params).join(", "),
      helperMissingParams: missingParams && ["depth0", this.quotedString(name)].concat(params).join(", ")
    };
  },

  // the params and contexts arguments are passed in arrays
  // to fill in
  setupParams: function(paramSize, params, useRegister) {
    var options = [], contexts = [], types = [], param, inverse, program;

    options.push("hash:" + this.popStack());

    inverse = this.popStack();
    program = this.popStack();

    // Avoid setting fn and inverse if neither are set. This allows
    // helpers to do a check for `if (options.fn)`
    if (program || inverse) {
      if (!program) {
        this.context.aliases.self = "this";
        program = "self.noop";
      }

      if (!inverse) {
       this.context.aliases.self = "this";
        inverse = "self.noop";
      }

      options.push("inverse:" + inverse);
      options.push("fn:" + program);
    }

    for(var i=0; i<paramSize; i++) {
      param = this.popStack();
      params.push(param);

      if(this.options.stringParams) {
        types.push(this.popStack());
        contexts.push(this.popStack());
      }
    }

    if (this.options.stringParams) {
      options.push("contexts:[" + contexts.join(",") + "]");
      options.push("types:[" + types.join(",") + "]");
      options.push("hashContexts:hashContexts");
      options.push("hashTypes:hashTypes");
    }

    if(this.options.data) {
      options.push("data:data");
    }

    options = "{" + options.join(",") + "}";
    if (useRegister) {
      this.register('options', options);
      params.push('options');
    } else {
      params.push(options);
    }
    return params.join(", ");
  }
};

var reservedWords = (
  "break else new var" +
  " case finally return void" +
  " catch for switch while" +
  " continue function this with" +
  " default if throw" +
  " delete in try" +
  " do instanceof typeof" +
  " abstract enum int short" +
  " boolean export interface static" +
  " byte extends long super" +
  " char final native synchronized" +
  " class float package throws" +
  " const goto private transient" +
  " debugger implements protected volatile" +
  " double import public let yield"
).split(" ");

var compilerWords = JavaScriptCompiler.RESERVED_WORDS = {};

for(var i=0, l=reservedWords.length; i<l; i++) {
  compilerWords[reservedWords[i]] = true;
}

JavaScriptCompiler.isValidJavaScriptVariableName = function(name) {
  if(!JavaScriptCompiler.RESERVED_WORDS[name] && /^[a-zA-Z_$][0-9a-zA-Z_$]+$/.test(name)) {
    return true;
  }
  return false;
};

export default JavaScriptCompiler;