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jsontemplate.js
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jsontemplate.js
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// Copyright (C) 2009 Andy Chu
//
// 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.
// $Id: json-template.js 271 2009-05-31 19:35:43Z andy@chubot.org $
//
// JavaScript implementation of json-template.
//
// This is predefined in tests, shouldn't be defined anywhere else. TODO: Do
// something nicer.
var log = log || function() {};
var repr = repr || function() {};
// The "module" exported by this script is called "jsontemplate":
var jsontemplate = exports.jsontemplate = function() {
// Regex escaping for common metacharacters (note that JavaScript needs 2 \\ --
// no raw strings!
var META_ESCAPE = {
'{': '\\{',
'}': '\\}',
'{{': '\\{\\{',
'}}': '\\}\\}',
'[': '\\[',
']': '\\]'
};
function _MakeTokenRegex(meta_left, meta_right) {
// TODO: check errors
return new RegExp(
'(' +
META_ESCAPE[meta_left] +
'.+?' +
META_ESCAPE[meta_right] +
'\n?)', 'g'); // global for use with .exec()
}
//
// Formatters
//
function HtmlEscape(s) {
return s.replace(/&/g,'&').
replace(/>/g,'>').
replace(/</g,'<');
}
function HtmlTagEscape(s) {
return s.replace(/&/g,'&').
replace(/>/g,'>').
replace(/</g,'<').
replace(/"/g,'"');
}
// Default ToString can be changed
function ToString(s) {
return s.toString();
}
var DEFAULT_FORMATTERS = {
'html': HtmlEscape,
'htmltag': HtmlTagEscape,
'html-attr-value': HtmlTagEscape,
'str': ToString,
'raw': function(x) {return x;}
};
//
// Template implementation
//
function _ScopedContext(context, undefined_str) {
// The stack contains:
// The current context (an object).
// An iteration index. -1 means we're NOT iterating.
var stack = [{context: context, index: -1}];
return {
PushSection: function(name) {
log('PushSection '+name);
if (name === undefined || name === null) {
return null;
}
var new_context = stack[stack.length-1].context[name] || null;
stack.push({context: new_context, index: -1});
return new_context;
},
Pop: function() {
stack.pop();
},
next: function() {
var stacktop = stack[stack.length-1];
// Now we're iterating -- push a new mutable object onto the stack
if (stacktop.index == -1) {
stacktop = {context: null, index: 0};
stack.push(stacktop);
}
// The thing we're iterating over
var context_array = stack[stack.length - 2].context;
// We're already done
if (stacktop.index == context_array.length) {
stack.pop();
log('next: null');
return null; // sentinel to say that we're done
}
log('next: ' + stacktop.index);
stacktop.context = context_array[stacktop.index++];
log('next: true');
return true; // OK, we mutated the stack
},
CursorValue: function() {
return stack[stack.length - 1].context;
},
_Undefined: function(name) {
if (undefined_str === undefined) {
throw {
name: 'UndefinedVariable', message: name + ' is not defined'
};
} else {
return undefined_str;
}
},
_LookUpStack: function(name) {
var i = stack.length - 1;
while (true) {
var context = stack[i].context;
log('context '+repr(context));
if (typeof context !== 'object') {
i--;
} else {
var value = context[name];
if (value === undefined || value === null) {
i--;
} else {
return value;
}
}
if (i <= -1) {
return this._Undefined(name);
}
}
},
Lookup: function(name) {
var parts = name.split('.');
var value = this._LookUpStack(parts[0]);
if (parts.length > 1) {
for (var i=1; i<parts.length; i++) {
value = value[parts[i]];
if (value === undefined) {
return this._Undefined(parts[i]);
}
}
}
return value;
}
};
}
function _Section(section_name) {
var current_clause = [];
var statements = {'default': current_clause};
return {
section_name: section_name, // public attribute
Statements: function(clause) {
clause = clause || 'default';
return statements[clause] || [];
},
NewClause: function(clause_name) {
var new_clause = [];
statements[clause_name] = new_clause;
current_clause = new_clause;
},
Append: function(statement) {
current_clause.push(statement);
}
};
}
function _Execute(statements, context, callback) {
var i;
for (i=0; i<statements.length; i++) {
var statement = statements[i];
//log('Executing ' + statement);
if (typeof(statement) == 'string') {
callback(statement);
} else {
var func = statement[0];
var args = statement[1];
func(args, context, callback);
}
}
}
function _DoSubstitute(statement, context, callback) {
log('Substituting: '+ statement.name);
var value;
if (statement.name == '@') {
value = context.CursorValue();
} else {
value = context.Lookup(statement.name);
}
// Format values
for (i=0; i<statement.formatters.length; i++) {
value = statement.formatters[i](value);
}
callback(value);
}
// for [section foo]
function _DoSection(args, context, callback) {
var block = args;
var value = context.PushSection(block.section_name);
var do_section = false;
// "truthy" values should have their sections executed.
if (value) {
do_section = true;
}
// Except: if the value is a zero-length array (which is "truthy")
if (value && value.length === 0) {
do_section = false;
}
if (do_section) {
_Execute(block.Statements(), context, callback);
context.Pop();
} else { // Empty list, None, False, etc.
context.Pop();
_Execute(block.Statements('or'), context, callback);
}
}
function _DoRepeatedSection(args, context, callback) {
var block = args;
var pushed;
if (block.section_name == '@') {
// If the name is @, we stay in the enclosing context, but assume it's a
// list, and repeat this block many times.
items = context.CursorValue();
// TODO: check that items is an array; apparently this is hard in JavaScript
//if type(items) is not list:
// raise EvaluationError('Expected a list; got %s' % type(items))
pushed = false;
} else {
items = context.PushSection(block.section_name);
pushed = true;
}
//log('ITEMS: '+showArray(items));
if (items && items.length > 0) {
// Execute the statements in the block for every item in the list.
// Execute the alternate block on every iteration except the last. Each
// item could be an atom (string, integer, etc.) or a dictionary.
var last_index = items.length - 1;
var statements = block.Statements();
var alt_statements = block.Statements('alternate');
for (var i=0; context.next() !== null; i++) {
log('_DoRepeatedSection i: ' +i);
_Execute(statements, context, callback);
if (i != last_index) {
log('ALTERNATE');
_Execute(alt_statements, context, callback);
}
}
} else {
log('OR: '+block.Statements('or'));
_Execute(block.Statements('or'), context, callback);
}
if (pushed) {
context.Pop();
}
}
var _SECTION_RE = /(repeated)?\s*(section)\s+(\S+)?/;
// TODO: The compile function could be in a different module, in case we want to
// compile on the server side.
function _Compile(template_str, options) {
var more_formatters = options.more_formatters ||
function (x) { return null; };
// We want to allow an explicit null value for default_formatter, which means
// that an error is raised if no formatter is specified.
var default_formatter;
if (options.default_formatter === undefined) {
default_formatter = 'str';
} else {
default_formatter = options.default_formatter;
}
function GetFormatter(format_str) {
var formatter = more_formatters(format_str) ||
DEFAULT_FORMATTERS[format_str];
if (formatter === undefined) {
throw {
name: 'BadFormatter',
message: format_str + ' is not a valid formatter'
};
}
return formatter;
}
var format_char = options.format_char || '|';
if (format_char != ':' && format_char != '|') {
throw {
name: 'ConfigurationError',
message: 'Only format characters : and | are accepted'
};
}
var meta = options.meta || '{}';
var n = meta.length;
if (n % 2 == 1) {
throw {
name: 'ConfigurationError',
message: meta + ' has an odd number of metacharacters'
};
}
var meta_left = meta.substring(0, n/2);
var meta_right = meta.substring(n/2, n);
var token_re = _MakeTokenRegex(meta_left, meta_right);
var current_block = _Section();
var stack = [current_block];
var strip_num = meta_left.length; // assume they're the same length
var token_match;
var last_index = 0;
while (true) {
token_match = token_re.exec(template_str);
log('match:', token_match);
if (token_match === null) {
break;
} else {
var token = token_match[0];
}
log('last_index: '+ last_index);
log('token_match.index: '+ token_match.index);
// Add the previous literal to the program
if (token_match.index > last_index) {
var tok = template_str.slice(last_index, token_match.index);
current_block.Append(tok);
log('tok: "'+ tok+'"');
}
last_index = token_re.lastIndex;
log('token0: "'+ token+'"');
var had_newline = false;
if (token.slice(-1) == '\n') {
token = token.slice(null, -1);
had_newline = true;
}
token = token.slice(strip_num, -strip_num);
if (token.charAt(0) == '#') {
continue; // comment
}
if (token.charAt(0) == '.') { // Keyword
token = token.substring(1, token.length);
var literal = {
'meta-left': meta_left,
'meta-right': meta_right,
'space': ' ',
'tab': '\t',
'newline': '\n'
}[token];
if (literal !== undefined) {
current_block.Append(literal);
continue;
}
var section_match = token.match(_SECTION_RE);
if (section_match) {
var repeated = section_match[1];
var section_name = section_match[3];
var func = repeated ? _DoRepeatedSection : _DoSection;
log('repeated ' + repeated + ' section_name ' + section_name);
var new_block = _Section(section_name);
current_block.Append([func, new_block]);
stack.push(new_block);
current_block = new_block;
continue;
}
if (token == 'alternates with') {
current_block.NewClause('alternate');
continue;
}
if (token == 'or') {
current_block.NewClause('or');
continue;
}
if (token == 'end') {
// End the block
stack.pop();
if (stack.length > 0) {
current_block = stack[stack.length-1];
} else {
throw {
name: 'TemplateSyntaxError',
message: 'Got too many {end} statements'
};
}
continue;
}
}
// A variable substitution
var parts = token.split(format_char);
var formatters;
var name;
if (parts.length == 1) {
if (default_formatter === null) {
throw {
name: 'MissingFormatter',
message: 'This template requires explicit formatters.'
};
}
// If no formatter is specified, the default is the 'str' formatter,
// which the user can define however they desire.
formatters = [GetFormatter(default_formatter)];
name = token;
} else {
formatters = [];
for (var j=1; j<parts.length; j++) {
formatters.push(GetFormatter(parts[j]));
}
name = parts[0];
}
current_block.Append(
[_DoSubstitute, { name: name, formatters: formatters}]);
if (had_newline) {
current_block.Append('\n');
}
}
// Add the trailing literal
current_block.Append(template_str.slice(last_index));
if (stack.length !== 1) {
throw {
name: 'TemplateSyntaxError',
message: 'Got too few {end} statements'
};
}
return current_block;
}
// The Template class is defined in the traditional style so that users can add
// methods by mutating the prototype attribute. TODO: Need a good idiom for
// inheritance without mutating globals.
function Template(template_str, options) {
// Add 'new' if we were not called with 'new', so prototyping works.
if(!(this instanceof Template)) {
return new Template(template_str, options);
}
this._options = options || {};
this._program = _Compile(template_str, this._options);
}
Template.prototype.render = function(data_dict, callback) {
// options.undefined_str can either be a string or undefined
var context = _ScopedContext(data_dict, this._options.undefined_str);
_Execute(this._program.Statements(), context, callback);
};
Template.prototype.expand = function(data_dict) {
var tokens = [];
this.render(data_dict, function(x) { tokens.push(x); });
return tokens.join('');
};
// We just export one name for now, the Template "class".
// We need HtmlEscape in the browser tests, so might as well export it.
return {Template: Template, HtmlEscape: HtmlEscape};
}();