var views = require('koa-views');

const render = views(__dirname + '/views', {
  map: {
    html: 'underscore'
  }
})

// Must be used before any router is used
app.use(render)
// OR Expand by app.context
// No order restrictions
// app.context.render = render()

app.use(async function (ctx) {
  ctx.state = {
    session: this.session,
    title: 'app'
  };

  await ctx.render('user', {
    user: 'John'
  });
});

var render = require('koa-views-render');

// ...

app.use(render('home', { title : 'Home Page' }));

const render = views(__dirname, { autoRender: false, extension: 'pug' });
app.use(render)
// OR
// app.context.render = render()

app.use(async function (ctx) {
  return await ctx.render('user.pug')
})

const render = views(__dirname, { extension: 'pug' })
app.use(render)
// OR
// app.context.render = render()

app.use(async function (ctx) {
  await ctx.render('user.pug')
})

app.use(async function (ctx) {
  await ctx.render('user.pug')
})

const render = views(__dirname, { extension: 'pug' })
app.use(render)
// OR
// app.context.render = render()

app.use(async function (ctx) {
  await ctx.render('user')
})

const render = views(__dirname, { map: {html: 'nunjucks' }})
app.use(render)
// OR
// app.context.render = render()
// render `user.html` with nunjucks
app.use(async function (ctx) {
  await ctx.render('user.html')
})

const render = views(__dirname, { engineSource: {foo: () => Promise.resolve('bar')}})
app.use(render)
// OR
// app.context.render = render()

app.use(async function (ctx) {
  await ctx.render('index.foo')
})

const app = new Koa()
  .use(views(__dirname, {
    map: { hbs: 'handlebars' },
    options: {
      helpers: {
        uppercase: (str) => str.toUpperCase()
      },

      partials: {
        subTitle: './my-partial' // requires ./my-partial.hbs
      },
      
      cache: true // cache the template string or not
    }
  }))
  .use(function (ctx) {
    ctx.state = { title: 'my title', author: 'queckezz' }
    return ctx.render('./my-view.hbs')
  })