heroku - Redirect to HTTPS and Apex Domain with Nginx location Configuration

I would like to force HTTPS and the apex domain (e.g. https://example.com) in my application through nginx configuration using location blocks. I currently have the following nginx_app.conf file (which works with both the apex and the www subdomain, and both http and https):

location / {
    try_files $uri @rewriteapp;
}

location @rewriteapp {
    rewrite ^(.*)$ /app.php/$1 last;
}

location ~ ^/(app|config)\.php(/|$) {
    # fastcgi_pass directives go here...

}

To force the apex domain and https, I tried using if-statements as follows, checking for the $scheme and $host variables, but I get an error that the page is not redirecting properly. I also added an HSTS directive.

location / {
    if ($scheme = http) {
        rewrite ^/(.*) https://$host/$1 permanent;
    }
    if ($host = www.example.com) {

        rewrite ^/(.*) https://example.com/$1 permanent;
    }
    try_files $uri @rewriteapp;
}

location @rewriteapp {
    rewrite ^(.*)$ /app.php/$1 last;
}

location ~ ^/(app|config)\.php(/|$) {

    # fastcgi_pass directives go here...
    add_header Strict-Transport-Security "max-age=86400";
}

What is the proper way to force http and the apex domain with nginx configuration? As an aside, I'm using heroku (with DNSimple) to deploy my app so I would like both the following domains to work: https://example.herokuapp.com and https://example.com.

UPDATE:
I tried moving the if-statements outside the location block into the default server block (click here), and change the rewrites for returns as follows, but it still does not work. I still get "The page isn't redirecting properly" when requesting http, and "Unable to connect error" when requesting the www subdomain.

if ($scheme = http) {
    return 301 https://$host$request_uri;
}
if ($host = www.example.com) {
    return 301 https://example.com$request_uri;
}

location / {
    try_files $uri @rewriteapp;
}


location @rewriteapp {
    rewrite ^(.*)$ /app.php/$1 last;
}

location ~ ^/(app|config)\.php(/|$) {
    # fastcgi_pass directives go here...
    add_header Strict-Transport-Security "max-age=86400";
}