var path = require("path"),
    _ = require("underscore"),
    fs = require("fs");

module.exports = function(themes) {

  if (!themes || !_.keys(_.omit(themes, "default")).length) {
    throw new Error("No themes found in settings/themes.json. See https://github.com/nypublicradio/audiogram/blob/master/THEMES.md for details.");
  }

  for (var key in themes) {
    if (key !== "default") {
      validateTheme(key, _.extend({}, themes.default || {}, themes[key]));
    }
  }

};

function validateTheme(name, options) {

  var fullBackgroundImagePath;

  if (!options || !_.keys(options).length) {
    return console.warn("Theme '" + name + "' is not defined.");
  }

  ["width", "height", "framesPerSecond", "samplesPerFrame"].forEach(function(key){
    if (typeof options[key] !== "number") {
      console.warn("The required property '" + key +"' is missing from theme '" + name + "' or invalid.");
    }
  });

  if (typeof options.backgroundImage === "string") {
    fullBackgroundImagePath = path.join(__dirname, "..", "..", "settings/backgrounds/", options.backgroundImage);

    try {
      fs.accessSync(fullBackgroundImagePath);
    } catch(e) {
      console.warn("Background image for theme '" + name + "' (" + fullBackgroundImagePath + ") does not exist or is not readable.");
    }
  }
}