#!/usr/bin/env node

// A minimal implementation of the venerable Grep utility [1], which prints
// lines that match a given regular expression [2]. Demonstrates how to parse
// the input into lines and write strings.
//
// [1] https://en.wikipedia.org/wiki/Grep
// [2] https://en.wikipedia.org/wiki/Regular_expression

var rw = require("../");

var pattern = new RegExp(process.argv[2]),
    reader = rw.fileReader(process.argv[3] || "/dev/stdin"),
    writer = rw.fileWriter("/dev/stdout"),
    lineParser = rw.lineParser();

reader.fill(function flow(error) {
  if (error) throw error;
  var data = reader.read(),
      line;

  if (data) lineParser.push(data);

  while ((line = lineParser.pop(reader.ended)) != null) {
    if (pattern.test(line) && !writer.write(line + "\n")) {
      return writer.drain(flow);
    }
  }

  if (reader.ended) return writer.end();

  reader.fill(flow);
});