#!/usr/bin/env node

var fs = require('fs');

var Mustache = require('..');
var pkg = require('../package');

var viewArg = process.argv[2];
var templateArg = process.argv[3];

if (process.argv.indexOf('--version') > -1) {
  return console.log(pkg.version);
}

if (!templateArg || !viewArg) {
  console.error('Syntax: mustache <view> <template>');
  process.exit(1);
}

run(readView, readTemplate, render, toStdout);

/**
 * Runs a list of functions as a waterfall.
 * Functions are runned one after the other in order, providing each
 * function the returned values of all the previously invoked functions.
 * Each function is expected to exit the process if an error occurs.
 */
function run(/*args*/) {
  var values = [];
  var fns = Array.prototype.slice.call(arguments);

  function invokeNextFn(val) {
    values.unshift(val);
    if (fns.length == 0) return;
    invoke(fns.shift());
  }

  function invoke(fn) {
    fn.apply(null, [invokeNextFn].concat(values));
  }

  invoke(fns.shift());
}

function readView(cb) {
  var view = isStdin(viewArg) ? process.openStdin() : fs.createReadStream(viewArg);

  streamToStr(view, function(str) {
    cb(JSON.parse(str));
  });
}

function readTemplate(cb) {
  var template = fs.createReadStream(templateArg);
  streamToStr(template, cb);
}

function render(cb, templateStr, jsonView) {
  cb(Mustache.render(templateStr, jsonView));
}

function toStdout(cb, str) {
  cb(process.stdout.write(str));
}

function streamToStr(stream, cb) {
  var data = '';

  stream.on('data', function(chunk) {
    data += chunk;
  }).once('end', function() {
    cb(data.toString());
  }).on('error', function(err) {
    if (wasNotFound(err)) {
      console.error('Could not find file:', err.path);
    } else {
      console.error('Error while reading file:', err.message);
    }
    process.exit(1);
  });
}

function isStdin(viewArg) {
  return viewArg === '-';
}

function wasNotFound(err) {
  return err.code && err.code === 'ENOENT';
}