let path = require('path');

let mount = require('koa-mount');

// wrap('modulePath')

// is same as

// require('modulePath').middleware,

// but also calls apply/undo upon entering/leaving the middleware

// --> here it does: this.templateDir = handlerModule dirname

module.exports = function (prefix, moduleDir) {

// actually includes router when the middleware is accessed (mount prefix matches)

let lazyRouterMiddleware = require('./lazyRouterMiddleware')(path.join(moduleDir, 'router'));

let templateDir = path.join(moduleDir, 'templates');

// /users/me -> /me

return mount(prefix, async function wrapMiddleware(ctx, next) {

// before entering middeware

let apply = () => {

// console.log("APPLY", templateDir);

ctx.templateDir = templateDir;

};

// before leaving middleware

let undo = () => {

// console.log("UNDO", templateDir);

delete ctx.templateDir;

};

apply();

try {

await lazyRouterMiddleware(ctx, async function () {

// when middleware does await next, undo changes

undo();

try {

await next();

} finally {

// ...then apply back, when control goes back after await next

apply();

}

});

} finally {

undo();

}

});

};