/* Parse function for JavaScript. Makes use of the tokenizer from
 * tokenizejavascript.js. Note that your parsers do not have to be
 * this complicated -- if you don't want to recognize local variables,
 * in many languages it is enough to just look for braces, semicolons,
 * parentheses, etc, and know when you are inside a string or comment.
 *
 * See manual.html for more info about the parser interface.
 */

var JSParser = Editor.Parser = (function () {
    // Token types that can be considered to be atoms.
    var atomicTypes = {"atom": true, "number": true, "variable": true, "string": true, "regexp": true};
    // Setting that can be used to have JSON data indent properly.
    var json = false;
    // Constructor for the lexical context objects.
    function JSLexical(indented, column, type, align, prev, info) {
        // indentation at start of this line
        this.indented = indented;
        // column at which this scope was opened
        this.column = column;
        // type of scope ('vardef', 'stat' (statement), 'form' (special form), '[', '{', or '(')
        this.type = type;
        // '[', '{', or '(' blocks that have any text after their opening
        // character are said to be 'aligned' -- any lines below are
        // indented all the way to the opening character.
        if (align != null)
            this.align = align;
        // Parent scope, if any.
        this.prev = prev;
        this.info = info;
    }

    // My favourite JavaScript indentation rules.
    function indentJS(lexical) {
        return function (firstChars) {
            var firstChar = firstChars && firstChars.charAt(0), type = lexical.type;
            var closing = firstChar == type;
            if (type == "vardef")
                return lexical.indented + 4;
            else if (type == "form" && firstChar == "{")
                return lexical.indented;
            else if (type == "stat" || type == "form")
                return lexical.indented + indentUnit;
            else if (lexical.info == "switch" && !closing)
                return lexical.indented + (/^(?:case|default)\b/.test(firstChars) ? indentUnit : 2 * indentUnit);
            else if (lexical.align)
                return lexical.column - (closing ? 1 : 0);
            else
                return lexical.indented + (closing ? 0 : indentUnit);
        };
    }

    // The parser-iterator-producing function itself.
    function parseJS(input, basecolumn) {
        // Wrap the input in a token stream
        var tokens = tokenizeJavaScript(input);
        // The parser state. cc is a stack of actions that have to be
        // performed to finish the current statement. For example we might
        // know that we still need to find a closing parenthesis and a
        // semicolon. Actions at the end of the stack go first. It is
        // initialized with an infinitely looping action that consumes
        // whole statements.
        var cc = [statements];
        // Context contains information about the current local scope, the
        // variables defined in that, and the scopes above it.
        var context = null;
        // The lexical scope, used mostly for indentation.
        var lexical = new JSLexical((basecolumn || 0) - indentUnit, 0, "block", false);
        // Current column, and the indentation at the start of the current
        // line. Used to create lexical scope objects.
        var column = 0;
        var indented = 0;
        // Variables which are used by the mark, cont, and pass functions
        // below to communicate with the driver loop in the 'next'
        // function.
        var consume, marked;

        // The iterator object.
        var parser = {next: next, copy: copy};

        function next() {
            // Start by performing any 'lexical' actions (adjusting the
            // lexical variable), or the operations below will be working
            // with the wrong lexical state.
            while (cc[cc.length - 1].lex)
                cc.pop()();

            // Fetch a token.
            var token = tokens.next();

            // Adjust column and indented.
            if (token.type == "whitespace" && column == 0)
                indented = token.value.length;
            column += token.value.length;
            if (token.content == "\n") {
                indented = column = 0;
                // If the lexical scope's align property is still undefined at
                // the end of the line, it is an un-aligned scope.
                if (!("align" in lexical))
                    lexical.align = false;
                // Newline tokens get an indentation function associated with
                // them.
                token.indentation = indentJS(lexical);
            }
            // No more processing for meaningless tokens.
            if (token.type == "whitespace" || token.type == "comment")
                return token;
            // When a meaningful token is found and the lexical scope's
            // align is undefined, it is an aligned scope.
            if (!("align" in lexical))
                lexical.align = true;

            // Execute actions until one 'consumes' the token and we can
            // return it.
            while (true) {
                consume = marked = false;
                // Take and execute the topmost action.
                cc.pop()(token.type, token.content);
                if (consume) {
                    // Marked is used to change the style of the current token.
                    if (marked)
                        token.style = marked;
                    // Here we differentiate between local and global variables.
                    else if (token.type == "variable" && inScope(token.content))
                        token.style = "js-localvariable";
                    return token;
                }
            }
        }

        // This makes a copy of the parser state. It stores all the
        // stateful variables in a closure, and returns a function that
        // will restore them when called with a new input stream. Note
        // that the cc array has to be copied, because it is contantly
        // being modified. Lexical objects are not mutated, and context
        // objects are not mutated in a harmful way, so they can be shared
        // between runs of the parser.
        function copy() {
            var _context = context, _lexical = lexical, _cc = cc.concat([]), _tokenState = tokens.state;

            return function copyParser(input) {
                context = _context;
                lexical = _lexical;
                cc = _cc.concat([]); // copies the array
                column = indented = 0;
                tokens = tokenizeJavaScript(input, _tokenState);
                return parser;
            };
        }

        // Helper function for pushing a number of actions onto the cc
        // stack in reverse order.
        function push(fs) {
            for (var i = fs.length - 1; i >= 0; i--)
                cc.push(fs[i]);
        }

        // cont and pass are used by the action functions to add other
        // actions to the stack. cont will cause the current token to be
        // consumed, pass will leave it for the next action.
        function cont() {
            push(arguments);
            consume = true;
        }

        function pass() {
            push(arguments);
            consume = false;
        }

        // Used to change the style of the current token.
        function mark(style) {
            marked = style;
        }

        // Push a new scope. Will automatically link the current scope.
        function pushcontext() {
            context = {prev: context, vars: {"this": true, "arguments": true}};
        }

        // Pop off the current scope.
        function popcontext() {
            context = context.prev;
        }

        // Register a variable in the current scope.
        function register(varname) {
            if (context) {
                mark("js-variabledef");
                context.vars[varname] = true;
            }
        }

        // Check whether a variable is defined in the current scope.
        function inScope(varname) {
            var cursor = context;
            while (cursor) {
                if (cursor.vars[varname])
                    return true;
                cursor = cursor.prev;
            }
            return false;
        }

        // Push a new lexical context of the given type.
        function pushlex(type, info) {
            var result = function () {
                lexical = new JSLexical(indented, column, type, null, lexical, info)
            };
            result.lex = true;
            return result;
        }

        // Pop off the current lexical context.
        function poplex() {
            lexical = lexical.prev;
        }

        poplex.lex = true;
        // The 'lex' flag on these actions is used by the 'next' function
        // to know they can (and have to) be ran before moving on to the
        // next token.

        // Creates an action that discards tokens until it finds one of
        // the given type.
        function expect(wanted) {
            return function expecting(type) {
                if (type == wanted) cont();
                else cont(arguments.callee);
            };
        }

        // Looks for a statement, and then calls itself.
        function statements(type) {
            return pass(statement, statements);
        }

        // Dispatches various types of statements based on the type of the
        // current token.
        function statement(type) {
            if (type == "var") cont(pushlex("vardef"), vardef1, expect(";"), poplex);
            else if (type == "keyword a") cont(pushlex("form"), expression, statement, poplex);
            else if (type == "keyword b") cont(pushlex("form"), statement, poplex);
            else if (type == "{" && json) cont(pushlex("}"), commasep(objprop, "}"), poplex);
            else if (type == "{") cont(pushlex("}"), block, poplex);
            else if (type == "function") cont(functiondef);
            else if (type == "for") cont(pushlex("form"), expect("("), pushlex(")"), forspec1, expect(")"), poplex, statement, poplex);
            else if (type == "variable") cont(pushlex("stat"), maybelabel);
            else if (type == "switch") cont(pushlex("form"), expression, pushlex("}", "switch"), expect("{"), block, poplex, poplex);
            else if (type == "case") cont(expression, expect(":"));
            else if (type == "default") cont(expect(":"));
            else if (type == "catch") cont(pushlex("form"), pushcontext, expect("("), funarg, expect(")"), statement, poplex, popcontext);
            else pass(pushlex("stat"), expression, expect(";"), poplex);
        }

        // Dispatch expression types.
        function expression(type) {
            if (atomicTypes.hasOwnProperty(type)) cont(maybeoperator);
            else if (type == "function") cont(functiondef);
            else if (type == "keyword c") cont(expression);
            else if (type == "(") cont(pushlex(")"), expression, expect(")"), poplex, maybeoperator);
            else if (type == "operator") cont(expression);
            else if (type == "[") cont(pushlex("]"), commasep(expression, "]"), poplex, maybeoperator);
            else if (type == "{") cont(pushlex("}"), commasep(objprop, "}"), poplex, maybeoperator);
        }

        // Called for places where operators, function calls, or
        // subscripts are valid. Will skip on to the next action if none
        // is found.
        function maybeoperator(type) {
            if (type == "operator") cont(expression);
            else if (type == "(") cont(pushlex(")"), expression, commasep(expression, ")"), poplex, maybeoperator);
            else if (type == ".") cont(property, maybeoperator);
            else if (type == "[") cont(pushlex("]"), expression, expect("]"), poplex, maybeoperator);
        }

        // When a statement starts with a variable name, it might be a
        // label. If no colon follows, it's a regular statement.
        function maybelabel(type) {
            if (type == ":") cont(poplex, statement);
            else pass(maybeoperator, expect(";"), poplex);
        }

        // Property names need to have their style adjusted -- the
        // tokenizer thinks they are variables.
        function property(type) {
            if (type == "variable") {
                mark("js-property");
                cont();
            }
        }

        // This parses a property and its value in an object literal.
        function objprop(type) {
            if (type == "variable") mark("js-property");
            if (atomicTypes.hasOwnProperty(type)) cont(expect(":"), expression);
        }

        // Parses a comma-separated list of the things that are recognized
        // by the 'what' argument.
        function commasep(what, end) {
            function proceed(type) {
                if (type == ",") cont(what, proceed);
                else if (type == end) cont();
                else cont(expect(end));
            };
            return function commaSeparated(type) {
                if (type == end) cont();
                else pass(what, proceed);
            };
        }

        // Look for statements until a closing brace is found.
        function block(type) {
            if (type == "}") cont();
            else pass(statement, block);
        }

        // Variable definitions are split into two actions -- 1 looks for
        // a name or the end of the definition, 2 looks for an '=' sign or
        // a comma.
        function vardef1(type, value) {
            if (type == "variable") {
                register(value);
                cont(vardef2);
            }
            else cont();
        }

        function vardef2(type, value) {
            if (value == "=") cont(expression, vardef2);
            else if (type == ",") cont(vardef1);
        }

        // For loops.
        function forspec1(type) {
            if (type == "var") cont(vardef1, forspec2);
            else if (type == ";") pass(forspec2);
            else if (type == "variable") cont(formaybein);
            else pass(forspec2);
        }

        function formaybein(type, value) {
            if (value == "in") cont(expression);
            else cont(maybeoperator, forspec2);
        }

        function forspec2(type, value) {
            if (type == ";") cont(forspec3);
            else if (value == "in") cont(expression);
            else cont(expression, expect(";"), forspec3);
        }

        function forspec3(type) {
            if (type == ")") pass();
            else cont(expression);
        }

        // A function definition creates a new context, and the variables
        // in its argument list have to be added to this context.
        function functiondef(type, value) {
            if (type == "variable") {
                register(value);
                cont(functiondef);
            }
            else if (type == "(") cont(pushcontext, commasep(funarg, ")"), statement, popcontext);
        }

        function funarg(type, value) {
            if (type == "variable") {
                register(value);
                cont();
            }
        }

        return parser;
    }

    return {
        make: parseJS,
        electricChars: "{}:",
        configure: function (obj) {
            if (obj.json != null) json = obj.json;
        }
    };
})();
