init

mc_test/node_modules/logform/combine.js

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+'use strict';
+
+const format = require('./format');
+
+/*
+ * function cascade(formats)
+ * Returns a function that invokes the `._format` function in-order
+ * for the specified set of `formats`. In this manner we say that Formats
+ * are "pipe-like", but not a pure pumpify implementation. Since there is no back
+ * pressure we can remove all of the "readable" plumbing in Node streams.
+ */
+function cascade(formats) {
+  if (!formats.every(isValidFormat)) {
+    return;
+  }
+
+  return info => {
+    let obj = info;
+    for (let i = 0; i < formats.length; i++) {
+      obj = formats[i].transform(obj, formats[i].options);
+      if (!obj) {
+        return false;
+      }
+    }
+
+    return obj;
+  };
+}
+
+/*
+ * function isValidFormat(format)
+ * If the format does not define a `transform` function throw an error
+ * with more detailed usage.
+ */
+function isValidFormat(fmt) {
+  if (typeof fmt.transform !== 'function') {
+    throw new Error([
+      'No transform function found on format. Did you create a format instance?',
+      'const myFormat = format(formatFn);',
+      'const instance = myFormat();'
+    ].join('\n'));
+  }
+
+  return true;
+}
+
+/*
+ * function combine (info)
+ * Returns a new instance of the combine Format which combines the specified
+ * formats into a new format. This is similar to a pipe-chain in transform streams.
+ * We choose to combine the prototypes this way because there is no back pressure in
+ * an in-memory transform chain.
+ */
+module.exports = (...formats) => {
+  const combinedFormat = format(cascade(formats));
+  const instance = combinedFormat();
+  instance.Format = combinedFormat.Format;
+  return instance;
+};
+
+//
+// Export the cascade method for use in cli and other
+// combined formats that should not be assumed to be
+// singletons.
+//
+module.exports.cascade = cascade;