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index.js
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index.js
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var clone = require('clone');
var Velocity = require('velocityjs');
var jsonpath = workaroundJsonPath(require('JSONPath'));
module.exports = function(parameters) {
parameters = clone(parameters || {});
var template = parameters.template;
var payload = parameters.payload;
var params = clone(parameters.params || {});
params.path = params.path || {};
params.querystring = params.querystring || {};
params.header = params.header || {};
var context = clone(parameters.context || {});
context.identity = context.identity || {};
// API Gateway Mapping Template Reference
// http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
var data = {
context: context,
input: {
_payload: payload.toString(),
path: function(path) {
var obj;
if (this._payload === '') {
// if payload is empty, treat it as empty object
// https://github.com/ToQoz/api-gateway-mapping-template/blob/master/test/_.md#example-91575d0e
obj = {};
} else if (/^\s*(?:{|\[|")/.test(this._payload)) {
// if payload starts with `{` or `[` or `"`, treat as JSON
obj = JSON.parse(this._payload);
} else {
// treat as string
obj = this._payload;
}
return jsonpath(obj, path);
},
json: function(path) {
var obj;
if (this._payload === '') {
// if payload is empty, treat it as empty object
// https://github.com/ToQoz/api-gateway-mapping-template/blob/master/test/_.md#example-098fd028
obj = {};
} else if (/^\s*(?:{|\[|")/.test(this._payload)) {
// if payload starts with `{` or `[` or `"`, treat as JSON
obj = JSON.parse(this._payload);
} else {
// treat as string
obj = this._payload;
}
return JSON.stringify(jsonpath(obj, path));
},
params: function(x) {
switch (true) {
case x === undefined:
return params;
case x in params.path:
return params.path[x];
case x in params.querystring:
return params.querystring[x];
case x in params.header:
return params.header[x];
}
},
},
util: {
escapeJavaScript: escapeJavaScript,
urlEncode: encodeURIComponent,
urlDecode: decodeURIComponent,
base64Encode: base64Encode,
base64Decode: base64Decode,
}
};
data = workaroundAwsObjectSerialization(data);
var ast = Velocity.parse(template.toString());
var config = {
escape: false, // don't escape HTML
};
return (new Velocity.Compile(ast, config)).render(data, null, true);
};
// Workaround to followings
// When the tempalte is "$input.params" (is a Function)
// - AWS API Gateway returns "{}".
// - This is not org.apache.velocity's behaviour. It returns "$input.params".
// When the tempalte is "$input" or "$util"
// - AWS API Gateway returns "{}"
// - This is not org.apache.velocity's behaviour. It returns serialized hash.
function workaroundAwsObjectSerialization(data) {
var returnEmptyObject = function() { return "{}"; };
// This never be called because keySet/entrySet/size will be processed by velocity.js.
// But I want to handling only toString
var builtinMethod = function() { throw "unexpected error"; };
builtinMethod.toString = returnEmptyObject;
data.input.toString = returnEmptyObject;
data.util.toString = returnEmptyObject;
walk(data, function(obj) {
if (typeof(obj) == 'function') {
obj.toString = returnEmptyObject;
}
obj.keySet = builtinMethod;
obj.entrySet = builtinMethod;
obj.size = builtinMethod;
});
return data;
}
function workaroundJsonPath(jsonpath) {
return function(obj, path) {
if (path === '$') {
return obj;
}
var result = jsonpath({
json: obj,
path: path
});
if (result.length === 1) {
return result[0];
} else {
return result;
}
};
}
function walk(obj, cb) {
cb(obj);
if (Array.isArray(obj)) {
obj.forEach(function(c) {
walk(c, cb);
});
} else if ({}.toString.call(obj) === '[object Object]') {
Object.keys(obj).forEach(function(k) {
walk(obj[k], cb);
});
}
}
function base64Encode(x) {
return (new Buffer(x)).toString('base64');
}
function base64Decode(x) {
return (new Buffer(x, 'base64')).toString();
}
// I recognize $util.escapeJavaScript as almost `escapeJSONString` and implemented so.
// c.f. 24.3.2.2 Runtime Semantics: QuoteJSONString ( value )
// http://www.ecma-international.org/ecma-262/6.0/index.html#sec-quotejsonstring
// DO: 2.a -> 2.b -> 2.c -> 2.d
var escapeJavaScriptTable = {
'"': '\"', // 2.a
'\\': '\\\\',
'\b': '\\b', // 2.b (skip abbrev)
'\f': '\\f',
'\n': '\\n',
'\r': '\\r',
'\t': '\\t',
};
// 2.c
for (var code = 0; code < 20; code++) {
escapeJavaScriptTable[String.fromCharCode(code)] = ((code < 16) ? '\\u000' : '\\u00') + code.toString(16);
}
function escapeJavaScript(x) {
return x.split("").map(function(c) {
// 2.a - 2.c
if (c in escapeJavaScriptTable) {
return escapeJavaScriptTable[c];
}
// 2.d
return c;
}).join("");
}