haproxy and 'fixing" host names in http requests - haproxy

Question

I'm starting to use haproxy to balance across nginx servers (in order to load balance the rails instances behind those nginxen). I want to 301 redirect all names that aren't the www name to the www name (and all http -> https). So I write this, which doesn't quite work. What actually happens is that http -> https, but all the names on https return 200 rather than 301 for all but www.staging.example.com. In addition, I was hoping to 301, say http://staging.example.com/ directly to https://www.staging.example.com/, but instead it just 301's to https://staging.example.com/
frontend www-http
bind 1.2.3.4:80
acl redirect_canonical req_ssl_sni -i staging.example.com
acl redirect_canonical req_ssl_sni -i myname.example.com
http-request redirect code 301 location https://www.staging.example.com%[capture.req.uri] if\
redirect_canonical
http-request redirect code 301 scheme https if !{ ssl_fc }
reqadd X-Forwarded-Proto:\ http
default_backend railswebapp-backend
frontend www-https
bind 1.2.3.4:443 ssl crt /etc/haproxy/ssl/
# Test URI to see if its a letsencrypt request.
acl letsencrypt-acl path_beg /.well-known/acme-challenge/
use_backend letsencrypt-backend if letsencrypt-acl
acl redirect_canonical req_ssl_sni -i staging.example.com
acl redirect_canonical req_ssl_sni -i myname.example.com
http-request redirect code 301 location https://www.staging.example.com%[capture.req.uri] if\
redirect_canonical
reqadd X-Forwarded-Proto:\ https
default_backend railswebapp-backend
Any pointers on what I'm doing wrong?
Update
The corrected block is this:
frontend www-http
bind 1.2.3.4:80
acl redirect_canonical hdr(host) -i staging.example.com
acl redirect_canonical hdr(host) -i myname.example.com
http-request redirect code 301 location https://www.staging.example.com%[capture.req.uri] if\
redirect_canonical
http-request redirect code 301 scheme https if !{ ssl_fc }
reqadd X-Forwarded-Proto:\ http
default_backend railswebapp-backend
frontend www-https
bind 1.2.3.4:443 ssl crt /etc/haproxy/ssl/
# Test URI to see if its a letsencrypt request.
acl letsencrypt-acl path_beg /.well-known/acme-challenge/
use_backend letsencrypt-backend if letsencrypt-acl
acl redirect_canonical ssl_fc_sni -i staging.example.com
acl redirect_canonical ssl_fc_sni -i myname.example.com
http-request redirect code 301 location https://www.staging.example.com%[capture.req.uri] if\
redirect_canonical
reqadd X-Forwarded-Proto:\ https
default_backend railswebapp-backend